Integrate unfix.org's IPv6 patches up to level 10, with rather a lot
[u/mdw/putty] / ssh.c
diff --git a/ssh.c b/ssh.c
index 57743cf..170253b 100644 (file)
--- a/ssh.c
+++ b/ssh.c
  * Packet type contexts, so that ssh2_pkt_type can correctly decode
  * the ambiguous type numbers back into the correct type strings.
  */
-#define SSH2_PKTCTX_DHGROUP1         0x0001
+#define SSH2_PKTCTX_DHGROUP          0x0001
 #define SSH2_PKTCTX_DHGEX            0x0002
 #define SSH2_PKTCTX_PUBLICKEY        0x0010
 #define SSH2_PKTCTX_PASSWORD         0x0020
@@ -162,7 +162,7 @@ static const char *const ssh2_disconnect_reasons[] = {
 #define BUG_CHOKES_ON_RSA                        8
 #define BUG_SSH2_RSA_PADDING                    16
 #define BUG_SSH2_DERIVEKEY                       32
-#define BUG_SSH2_DH_GEX                          64
+/* 64 was BUG_SSH2_DH_GEX, now spare */
 #define BUG_SSH2_PK_SESSIONID                   128
 
 #define translate(x) if (type == x) return #x
@@ -222,8 +222,8 @@ static char *ssh2_pkt_type(int pkt_ctx, int type)
     translate(SSH2_MSG_SERVICE_ACCEPT);
     translate(SSH2_MSG_KEXINIT);
     translate(SSH2_MSG_NEWKEYS);
-    translatec(SSH2_MSG_KEXDH_INIT, SSH2_PKTCTX_DHGROUP1);
-    translatec(SSH2_MSG_KEXDH_REPLY, SSH2_PKTCTX_DHGROUP1);
+    translatec(SSH2_MSG_KEXDH_INIT, SSH2_PKTCTX_DHGROUP);
+    translatec(SSH2_MSG_KEXDH_REPLY, SSH2_PKTCTX_DHGROUP);
     translatec(SSH2_MSG_KEX_DH_GEX_REQUEST, SSH2_PKTCTX_DHGEX);
     translatec(SSH2_MSG_KEX_DH_GEX_GROUP, SSH2_PKTCTX_DHGEX);
     translatec(SSH2_MSG_KEX_DH_GEX_INIT, SSH2_PKTCTX_DHGEX);
@@ -329,6 +329,7 @@ static unsigned char *ssh2_mpint_fmt(Bignum b, int *len);
 static void ssh2_pkt_addmp(struct Packet *, Bignum b);
 static int ssh2_pkt_construct(Ssh, struct Packet *);
 static void ssh2_pkt_send(Ssh, struct Packet *);
+static void ssh2_pkt_send_noqueue(Ssh, struct Packet *);
 static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
                         struct Packet *pktin);
 static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
@@ -359,11 +360,6 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 #define SSH_MAX_BACKLOG 32768
 #define OUR_V2_WINSIZE 16384
 
-const static struct ssh_kex *kex_algs[] = {
-    &ssh_diffiehellman_gex,
-    &ssh_diffiehellman
-};
-
 const static struct ssh_signkey *hostkey_algs[] = { &ssh_rsa, &ssh_dss };
 
 static void *nullmac_make_context(void)
@@ -498,23 +494,48 @@ struct ssh_channel {
  * of its ports was connected to; and _you_ have to remember what
  * local host:port pair went with that port number.
  * 
- * Hence: in SSH 1 this structure stores host:port pairs we intend
- * to allow connections to, and is indexed by those host:port
- * pairs. In SSH 2 it stores a mapping from source port to
- * destination host:port pair, and is indexed by source port.
+ * Hence, in SSH 1 this structure is indexed by destination
+ * host:port pair, whereas in SSH 2 it is indexed by source port.
  */
+struct ssh_portfwd; /* forward declaration */
+
 struct ssh_rportfwd {
     unsigned sport, dport;
     char dhost[256];
+    char *sportdesc;
+    struct ssh_portfwd *pfrec;
+};
+#define free_rportfwd(pf) ( \
+    ((pf) ? (sfree((pf)->sportdesc)) : (void)0 ), sfree(pf) )
+
+/*
+ * Separately to the rportfwd tree (which is for looking up port
+ * open requests from the server), a tree of _these_ structures is
+ * used to keep track of all the currently open port forwardings,
+ * so that we can reconfigure in mid-session if the user requests
+ * it.
+ */
+struct ssh_portfwd {
+    int keep;
+    int type;
+    unsigned sport, dport;
+    char *saddr, *daddr;
+    struct ssh_rportfwd *remote;
+    int addressfamily;
+    void *local;
 };
+#define free_portfwd(pf) ( \
+    ((pf) ? (sfree((pf)->saddr), sfree((pf)->daddr)) : (void)0 ), sfree(pf) )
 
 struct Packet {
     long length;
     int type;
+    unsigned long sequence;
     unsigned char *data;
     unsigned char *body;
     long savedpos;
     long maxlen;
+    long encrypted_len;                       /* for SSH2 total-size counting */
 
     /*
      * State associated with packet logging
@@ -528,6 +549,8 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen,
                          struct Packet *pktin);
 static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen,
                          struct Packet *pktin);
+static void ssh1_protocol_setup(Ssh ssh);
+static void ssh2_protocol_setup(Ssh ssh);
 static void ssh_size(void *handle, int width, int height);
 static void ssh_special(void *handle, Telnet_Special);
 static int ssh2_try_send(struct ssh_channel *c);
@@ -539,6 +562,9 @@ static void ssh_do_close(Ssh ssh);
 static unsigned long ssh_pkt_getuint32(struct Packet *pkt);
 static int ssh2_pkt_getbool(struct Packet *pkt);
 static void ssh_pkt_getstring(struct Packet *pkt, char **p, int *length);
+static void ssh2_timer(void *ctx, long now);
+static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
+                            struct Packet *pktin);
 
 struct rdpkt1_state_tag {
     long len, pad, biglen, to_read;
@@ -557,6 +583,17 @@ struct rdpkt2_state_tag {
     struct Packet *pktin;
 };
 
+typedef void (*handler_fn_t)(Ssh ssh, struct Packet *pktin);
+typedef void (*chandler_fn_t)(Ssh ssh, struct Packet *pktin, void *ctx);
+
+struct queued_handler;
+struct queued_handler {
+    int msg1, msg2;
+    chandler_fn_t handler;
+    void *ctx;
+    struct queued_handler *next;
+};
+
 struct ssh_tag {
     const struct plug_function_table *fn;
     /* the above field _must_ be first in the structure */
@@ -603,7 +640,7 @@ struct ssh_tag {
     struct ssh_channel *mainchan;      /* primary session channel */
     int exitcode;
 
-    tree234 *rportfwds;
+    tree234 *rportfwds, *portfwds;
 
     enum {
        SSH_STATE_PREPACKET,
@@ -615,6 +652,9 @@ struct ssh_tag {
 
     int size_needed, eof_needed;
 
+    struct Packet **queue;
+    int queuelen, queuesize;
+    int queueing;
     unsigned char *deferred_send_data;
     int deferred_len, deferred_size;
 
@@ -634,7 +674,6 @@ struct ssh_tag {
     int userpass_input_bufpos;
     int userpass_input_echo;
 
-    char *portfwd_strptr;
     int pkt_ctx;
 
     void *x11auth;
@@ -650,8 +689,8 @@ struct ssh_tag {
     int ssh2_rdpkt_crstate;
     int do_ssh_init_crstate;
     int ssh_gotdata_crstate;
-    int ssh1_protocol_crstate;
     int do_ssh1_login_crstate;
+    int do_ssh1_connection_crstate;
     int do_ssh2_transport_crstate;
     int do_ssh2_authconn_crstate;
 
@@ -663,6 +702,9 @@ struct ssh_tag {
     struct rdpkt1_state_tag rdpkt1_state;
     struct rdpkt2_state_tag rdpkt2_state;
 
+    /* ssh1 and ssh2 use this for different things, but both use it */
+    int protocol_initial_phase_done;
+
     void (*protocol) (Ssh ssh, unsigned char *in, int inlen,
                      struct Packet *pkt);
     struct Packet *(*s_rdpkt) (Ssh ssh, unsigned char **data, int *datalen);
@@ -680,6 +722,32 @@ struct ssh_tag {
      */
     void *agent_response;
     int agent_response_len;
+
+    /*
+     * Dispatch table for packet types that we may have to deal
+     * with at any time.
+     */
+    handler_fn_t packet_dispatch[256];
+
+    /*
+     * Queues of one-off handler functions for success/failure
+     * indications from a request.
+     */
+    struct queued_handler *qhead, *qtail;
+
+    /*
+     * This module deals with sending keepalives.
+     */
+    Pinger pinger;
+
+    /*
+     * Track incoming and outgoing data sizes and time, for
+     * size-based rekeys.
+     */
+    unsigned long incoming_data_size, outgoing_data_size, deferred_data_size;
+    unsigned long max_data_size;
+    int kex_in_progress;
+    long next_rekey, last_rekey;
 };
 
 #define logevent(s) logevent(ssh->frontend, s)
@@ -772,6 +840,47 @@ static int ssh_rportcmp_ssh2(void *av, void *bv)
     return 0;
 }
 
+/*
+ * Special form of strcmp which can cope with NULL inputs. NULL is
+ * defined to sort before even the empty string.
+ */
+static int nullstrcmp(const char *a, const char *b)
+{
+    if (a == NULL && b == NULL)
+       return 0;
+    if (a == NULL)
+       return -1;
+    if (b == NULL)
+       return +1;
+    return strcmp(a, b);
+}
+
+static int ssh_portcmp(void *av, void *bv)
+{
+    struct ssh_portfwd *a = (struct ssh_portfwd *) av;
+    struct ssh_portfwd *b = (struct ssh_portfwd *) bv;
+    int i;
+    if (a->type > b->type)
+       return +1;
+    if (a->type < b->type)
+       return -1;
+    if ( (i = nullstrcmp(a->saddr, b->saddr)) != 0)
+       return i < 0 ? -1 : +1;
+    if (a->sport > b->sport)
+       return +1;
+    if (a->sport < b->sport)
+       return -1;
+    if (a->type != 'D') {
+       if ( (i = nullstrcmp(a->daddr, b->daddr)) != 0)
+           return i < 0 ? -1 : +1;
+       if (a->dport > b->dport)
+           return +1;
+       if (a->dport < b->dport)
+           return -1;
+    }
+    return 0;
+}
+
 static int alloc_channel_id(Ssh ssh)
 {
     const unsigned CHANNEL_NUMBER_OFFSET = 256;
@@ -869,8 +978,6 @@ static struct Packet *ssh1_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
 
     crBegin(ssh->ssh1_rdpkt_crstate);
 
-  next_packet:
-
     st->pktin = ssh_new_packet();
 
     st->pktin->type = 0;
@@ -988,48 +1095,6 @@ static struct Packet *ssh1_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
                   nblanks, &blank);
     }
 
-    if (st->pktin->type == SSH1_SMSG_STDOUT_DATA ||
-       st->pktin->type == SSH1_SMSG_STDERR_DATA ||
-       st->pktin->type == SSH1_MSG_DEBUG ||
-       st->pktin->type == SSH1_SMSG_AUTH_TIS_CHALLENGE ||
-       st->pktin->type == SSH1_SMSG_AUTH_CCARD_CHALLENGE) {
-       long stringlen = GET_32BIT(st->pktin->body);
-       if (stringlen + 4 != st->pktin->length) {
-           bombout(("Received data packet with bogus string length"));
-           ssh_free_packet(st->pktin);
-           crStop(NULL);
-       }
-    }
-
-    if (st->pktin->type == SSH1_MSG_DEBUG) {
-        char *buf, *msg;
-        int msglen;
-
-        ssh_pkt_getstring(st->pktin, &msg, &msglen);
-        buf = dupprintf("Remote debug message: %.*s", msglen, msg);
-       logevent(buf);
-        sfree(buf);
-
-       ssh_free_packet(st->pktin);
-       goto next_packet;
-    } else if (st->pktin->type == SSH1_MSG_IGNORE) {
-       /* do nothing */
-       ssh_free_packet(st->pktin);
-       goto next_packet;
-    }
-
-    if (st->pktin->type == SSH1_MSG_DISCONNECT) {
-       /* log reason code in disconnect message */
-       char *msg;
-       int msglen;
-
-        ssh_pkt_getstring(st->pktin, &msg, &msglen);
-
-       bombout(("Server sent disconnect message:\n\"%.*s\"", msglen, msg));
-       ssh_free_packet(st->pktin);
-       crStop(NULL);
-    }
-
     crFinish(st->pktin);
 }
 
@@ -1039,8 +1104,6 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
 
     crBegin(ssh->ssh2_rdpkt_crstate);
 
-  next_packet:
-
     st->pktin = ssh_new_packet();
 
     st->pktin->type = 0;
@@ -1122,6 +1185,8 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
                               st->pktin->data + st->cipherblk,
                               st->packetlen - st->cipherblk);
 
+    st->pktin->encrypted_len = st->packetlen;
+
     /*
      * Check the MAC.
      */
@@ -1132,7 +1197,8 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
        ssh_free_packet(st->pktin);
        crStop(NULL);
     }
-    st->incoming_sequence++;          /* whether or not we MACed */
+
+    st->pktin->sequence = st->incoming_sequence++;
 
     /*
      * Decompress packet payload.
@@ -1187,113 +1253,6 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
                   nblanks, &blank);
     }
 
-    switch (st->pktin->type) {
-        /*
-         * These packets we must handle instantly.
-         */
-      case SSH2_MSG_DISCONNECT:
-        {
-            /* log reason code in disconnect message */
-            char *buf, *msg;
-            int nowlen, reason, msglen;
-
-            reason = ssh_pkt_getuint32(st->pktin);
-            ssh_pkt_getstring(st->pktin, &msg, &msglen);
-
-            if (reason > 0 && reason < lenof(ssh2_disconnect_reasons)) {
-                buf = dupprintf("Received disconnect message (%s)",
-                               ssh2_disconnect_reasons[reason]);
-            } else {
-                buf = dupprintf("Received disconnect message (unknown"
-                               " type %d)", reason);
-            }
-            logevent(buf);
-           sfree(buf);
-            buf = dupprintf("Disconnection message text: %n%.*s",
-                           &nowlen, msglen, msg);
-            logevent(buf);
-            bombout(("Server sent disconnect message\ntype %d (%s):\n\"%s\"",
-                     reason,
-                     (reason > 0 && reason < lenof(ssh2_disconnect_reasons)) ?
-                     ssh2_disconnect_reasons[reason] : "unknown",
-                     buf+nowlen));
-           sfree(buf);
-           ssh_free_packet(st->pktin);
-            crStop(NULL);
-        }
-        break;
-      case SSH2_MSG_IGNORE:
-       ssh_free_packet(st->pktin);
-       goto next_packet;
-      case SSH2_MSG_DEBUG:
-       {
-           /* log the debug message */
-           char *buf, *msg;
-           int msglen;
-           int always_display;
-
-           /* XXX maybe we should actually take notice of this */
-            always_display = ssh2_pkt_getbool(st->pktin);
-            ssh_pkt_getstring(st->pktin, &msg, &msglen);
-
-            buf = dupprintf("Remote debug message: %.*s", msglen, msg);
-           logevent(buf);
-            sfree(buf);
-       }
-       ssh_free_packet(st->pktin);
-        goto next_packet;
-
-        /*
-         * These packets we need do nothing about here.
-         */
-      case SSH2_MSG_UNIMPLEMENTED:
-      case SSH2_MSG_SERVICE_REQUEST:
-      case SSH2_MSG_SERVICE_ACCEPT:
-      case SSH2_MSG_KEXINIT:
-      case SSH2_MSG_NEWKEYS:
-      case SSH2_MSG_KEXDH_INIT:
-      case SSH2_MSG_KEXDH_REPLY:
-      /* case SSH2_MSG_KEX_DH_GEX_REQUEST: duplicate case value */
-      /* case SSH2_MSG_KEX_DH_GEX_GROUP: duplicate case value */
-      case SSH2_MSG_KEX_DH_GEX_INIT:
-      case SSH2_MSG_KEX_DH_GEX_REPLY:
-      case SSH2_MSG_USERAUTH_REQUEST:
-      case SSH2_MSG_USERAUTH_FAILURE:
-      case SSH2_MSG_USERAUTH_SUCCESS:
-      case SSH2_MSG_USERAUTH_BANNER:
-      case SSH2_MSG_USERAUTH_PK_OK:
-      /* case SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ: duplicate case value */
-      /* case SSH2_MSG_USERAUTH_INFO_REQUEST: duplicate case value */
-      case SSH2_MSG_USERAUTH_INFO_RESPONSE:
-      case SSH2_MSG_GLOBAL_REQUEST:
-      case SSH2_MSG_REQUEST_SUCCESS:
-      case SSH2_MSG_REQUEST_FAILURE:
-      case SSH2_MSG_CHANNEL_OPEN:
-      case SSH2_MSG_CHANNEL_OPEN_CONFIRMATION:
-      case SSH2_MSG_CHANNEL_OPEN_FAILURE:
-      case SSH2_MSG_CHANNEL_WINDOW_ADJUST:
-      case SSH2_MSG_CHANNEL_DATA:
-      case SSH2_MSG_CHANNEL_EXTENDED_DATA:
-      case SSH2_MSG_CHANNEL_EOF:
-      case SSH2_MSG_CHANNEL_CLOSE:
-      case SSH2_MSG_CHANNEL_REQUEST:
-      case SSH2_MSG_CHANNEL_SUCCESS:
-      case SSH2_MSG_CHANNEL_FAILURE:
-        break;
-
-        /*
-         * For anything else we send SSH2_MSG_UNIMPLEMENTED.
-         */
-      default:
-       {
-           struct Packet *pktout;
-           pktout = ssh2_pkt_init(SSH2_MSG_UNIMPLEMENTED);
-           ssh2_pkt_adduint32(pktout, st->incoming_sequence - 1);
-           ssh2_pkt_send(ssh, pktout);
-       }
-        break;
-    }
-
     crFinish(st->pktin);
 }
 
@@ -1721,14 +1680,45 @@ static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
        ssh->cscipher->encrypt(ssh->cs_cipher_ctx,
                               pkt->data, pkt->length + padding);
 
+    pkt->encrypted_len = pkt->length + padding;
+
     /* Ready-to-send packet starts at pkt->data. We return length. */
     return pkt->length + padding + maclen;
 }
 
 /*
- * Construct and send an SSH2 packet immediately.
+ * Routines called from the main SSH code to send packets. There
+ * are quite a few of these, because we have two separate
+ * mechanisms for delaying the sending of packets:
+ * 
+ *  - In order to send an IGNORE message and a password message in
+ *    a single fixed-length blob, we require the ability to
+ *    concatenate the encrypted forms of those two packets _into_ a
+ *    single blob and then pass it to our <network.h> transport
+ *    layer in one go. Hence, there's a deferment mechanism which
+ *    works after packet encryption.
+ * 
+ *  - In order to avoid sending any connection-layer messages
+ *    during repeat key exchange, we have to queue up any such
+ *    outgoing messages _before_ they are encrypted (and in
+ *    particular before they're allocated sequence numbers), and
+ *    then send them once we've finished.
+ * 
+ * I call these mechanisms `defer' and `queue' respectively, so as
+ * to distinguish them reasonably easily.
+ * 
+ * The functions send_noqueue() and defer_noqueue() free the packet
+ * structure they are passed. Every outgoing packet goes through
+ * precisely one of these functions in its life; packets passed to
+ * ssh2_pkt_send() or ssh2_pkt_defer() either go straight to one of
+ * these or get queued, and then when the queue is later emptied
+ * the packets are all passed to defer_noqueue().
+ */
+
+/*
+ * Send an SSH2 packet immediately, without queuing or deferring.
  */
-static void ssh2_pkt_send(Ssh ssh, struct Packet *pkt)
+static void ssh2_pkt_send_noqueue(Ssh ssh, struct Packet *pkt)
 {
     int len;
     int backlog;
@@ -1736,21 +1726,21 @@ static void ssh2_pkt_send(Ssh ssh, struct Packet *pkt)
     backlog = sk_write(ssh->s, (char *)pkt->data, len);
     if (backlog > SSH_MAX_BACKLOG)
        ssh_throttle_all(ssh, 1, backlog);
+
+    ssh->outgoing_data_size += pkt->encrypted_len;
+    if (!ssh->kex_in_progress &&
+       ssh->max_data_size != 0 &&
+       ssh->outgoing_data_size > ssh->max_data_size)
+       do_ssh2_transport(ssh, "Initiating key re-exchange "
+                         "(too much data sent)", -1, NULL);
+
     ssh_free_packet(pkt);
 }
 
 /*
- * Construct an SSH2 packet and add it to a deferred data block.
- * Useful for sending multiple packets in a single sk_write() call,
- * to prevent a traffic-analysing listener from being able to work
- * out the length of any particular packet (such as the password
- * packet).
- * 
- * Note that because SSH2 sequence-numbers its packets, this can
- * NOT be used as an m4-style `defer' allowing packets to be
- * constructed in one order and sent in another.
+ * Defer an SSH2 packet.
  */
-static void ssh2_pkt_defer(Ssh ssh, struct Packet *pkt)
+static void ssh2_pkt_defer_noqueue(Ssh ssh, struct Packet *pkt)
 {
     int len = ssh2_pkt_construct(ssh, pkt);
     if (ssh->deferred_len + len > ssh->deferred_size) {
@@ -1761,12 +1751,61 @@ static void ssh2_pkt_defer(Ssh ssh, struct Packet *pkt)
     }
     memcpy(ssh->deferred_send_data + ssh->deferred_len, pkt->data, len);
     ssh->deferred_len += len;
+    ssh->deferred_data_size += pkt->encrypted_len;
     ssh_free_packet(pkt);
 }
 
 /*
+ * Queue an SSH2 packet.
+ */
+static void ssh2_pkt_queue(Ssh ssh, struct Packet *pkt)
+{
+    assert(ssh->queueing);
+
+    if (ssh->queuelen >= ssh->queuesize) {
+       ssh->queuesize = ssh->queuelen + 32;
+       ssh->queue = sresize(ssh->queue, ssh->queuesize, struct Packet *);
+    }
+
+    ssh->queue[ssh->queuelen++] = pkt;
+}
+
+/*
+ * Either queue or send a packet, depending on whether queueing is
+ * set.
+ */
+static void ssh2_pkt_send(Ssh ssh, struct Packet *pkt)
+{
+    if (ssh->queueing)
+       ssh2_pkt_queue(ssh, pkt);
+    else
+       ssh2_pkt_send_noqueue(ssh, pkt);
+}
+
+/*
+ * Either queue or defer a packet, depending on whether queueing is
+ * set.
+ */
+static void ssh2_pkt_defer(Ssh ssh, struct Packet *pkt)
+{
+    if (ssh->queueing)
+       ssh2_pkt_queue(ssh, pkt);
+    else
+       ssh2_pkt_defer_noqueue(ssh, pkt);
+}
+
+/*
  * Send the whole deferred data block constructed by
  * ssh2_pkt_defer() or SSH1's defer_packet().
+ * 
+ * The expected use of the defer mechanism is that you call
+ * ssh2_pkt_defer() a few times, then call ssh_pkt_defersend(). If
+ * not currently queueing, this simply sets up deferred_send_data
+ * and then sends it. If we _are_ currently queueing, the calls to
+ * ssh2_pkt_defer() put the deferred packets on to the queue
+ * instead, and therefore ssh_pkt_defersend() has no deferred data
+ * to send. Hence, there's no need to make it conditional on
+ * ssh->queueing.
  */
 static void ssh_pkt_defersend(Ssh ssh)
 {
@@ -1778,6 +1817,32 @@ static void ssh_pkt_defersend(Ssh ssh)
     ssh->deferred_send_data = NULL;
     if (backlog > SSH_MAX_BACKLOG)
        ssh_throttle_all(ssh, 1, backlog);
+
+    ssh->outgoing_data_size += ssh->deferred_data_size;
+    if (!ssh->kex_in_progress &&
+       ssh->max_data_size != 0 &&
+       ssh->outgoing_data_size > ssh->max_data_size)
+       do_ssh2_transport(ssh, "Initiating key re-exchange "
+                         "(too much data sent)", -1, NULL);
+    ssh->deferred_data_size = 0;
+}
+
+/*
+ * Send all queued SSH2 packets. We send them by means of
+ * ssh2_pkt_defer_noqueue(), in case they included a pair of
+ * packets that needed to be lumped together.
+ */
+static void ssh2_pkt_queuesend(Ssh ssh)
+{
+    int i;
+
+    assert(!ssh->queueing);
+
+    for (i = 0; i < ssh->queuelen; i++)
+       ssh2_pkt_defer_noqueue(ssh, ssh->queue[i]);
+    ssh->queuelen = 0;
+
+    ssh_pkt_defersend(ssh);
 }
 
 #if 0
@@ -2065,13 +2130,28 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
        ssh->remote_bugs |= BUG_SSH2_PK_SESSIONID;
        logevent("We believe remote version has SSH2 public-key-session-ID bug");
     }
+}
 
-    if (ssh->cfg.sshbug_dhgex2 == FORCE_ON) {
-       /*
-        * User specified the SSH2 DH GEX bug.
-        */
-       ssh->remote_bugs |= BUG_SSH2_DH_GEX;
-       logevent("We believe remote version has SSH2 DH group exchange bug");
+/*
+ * The `software version' part of an SSH version string is required
+ * to contain no spaces or minus signs.
+ */
+static void ssh_fix_verstring(char *str)
+{
+    /* Eat "SSH-<protoversion>-". */
+    assert(*str == 'S'); str++;
+    assert(*str == 'S'); str++;
+    assert(*str == 'H'); str++;
+    assert(*str == '-'); str++;
+    while (*str && *str != '-') str++;
+    assert(*str == '-'); str++;
+
+    /* Convert minus signs and spaces in the remaining string into
+     * underscores. */
+    while (*str) {
+        if (*str == '-' || *str == ' ')
+            *str = '_';
+        str++;
     }
 }
 
@@ -2134,7 +2214,7 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
     ssh->rdpkt2_state.incoming_sequence = 0;
 
     s->vstring[s->vslen] = 0;
-    s->vstring[strcspn(s->vstring, "\r\n")] = '\0';/* remove EOL chars */
+    s->vstring[strcspn(s->vstring, "\015\012")] = '\0';/* remove EOL chars */
     {
        char *vlog;
        vlog = snewn(20 + s->vslen, char);
@@ -2162,46 +2242,63 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
        crStop(0);
     }
 
-    if (s->proto2 && (ssh->cfg.sshprot >= 2 || !s->proto1)) {
-       /*
-        * Use v2 protocol.
-        */
-       char verstring[80], vlog[100];
-       sprintf(verstring, "SSH-2.0-%s", sshver);
-       SHA_Init(&ssh->exhashbase);
-       /*
-        * Hash our version string and their version string.
-        */
-       sha_string(&ssh->exhashbase, verstring, strlen(verstring));
-       sha_string(&ssh->exhashbase, s->vstring, strcspn(s->vstring, "\r\n"));
-       sprintf(vlog, "We claim version: %s", verstring);
-       logevent(vlog);
-       strcat(verstring, "\012");
-       logevent("Using SSH protocol version 2");
-       sk_write(ssh->s, verstring, strlen(verstring));
-       ssh->protocol = ssh2_protocol;
-       ssh->version = 2;
-       ssh->s_rdpkt = ssh2_rdpkt;
-    } else {
-       /*
-        * Use v1 protocol.
-        */
-       char verstring[80], vlog[100];
-       sprintf(verstring, "SSH-%s-%s",
-               (ssh_versioncmp(s->version, "1.5") <= 0 ? s->version : "1.5"),
-               sshver);
-       sprintf(vlog, "We claim version: %s", verstring);
-       logevent(vlog);
-       strcat(verstring, "\012");
+    {
+        char *verstring;
+
+        if (s->proto2 && (ssh->cfg.sshprot >= 2 || !s->proto1)) {
+            /*
+             * Construct a v2 version string.
+             */
+            verstring = dupprintf("SSH-2.0-%s\015\012", sshver);
+            ssh->version = 2;
+        } else {
+            /*
+             * Construct a v1 version string.
+             */
+            verstring = dupprintf("SSH-%s-%s\012",
+                                  (ssh_versioncmp(s->version, "1.5") <= 0 ?
+                                   s->version : "1.5"),
+                                  sshver);
+            ssh->version = 1;
+        }
 
-       logevent("Using SSH protocol version 1");
+        ssh_fix_verstring(verstring);
+
+        if (ssh->version == 2) {
+            /*
+             * Hash our version string and their version string.
+             */
+            SHA_Init(&ssh->exhashbase);
+            sha_string(&ssh->exhashbase, verstring,
+                       strcspn(verstring, "\015\012"));
+            sha_string(&ssh->exhashbase, s->vstring,
+                       strcspn(s->vstring, "\015\012"));
+
+            /*
+             * Initialise SSHv2 protocol.
+             */
+            ssh->protocol = ssh2_protocol;
+            ssh2_protocol_setup(ssh);
+            ssh->s_rdpkt = ssh2_rdpkt;
+        } else {
+            /*
+             * Initialise SSHv1 protocol.
+             */
+            ssh->protocol = ssh1_protocol;
+            ssh1_protocol_setup(ssh);
+            ssh->s_rdpkt = ssh1_rdpkt;
+        }
+        logeventf(ssh, "We claim version: %.*s",
+                  strcspn(verstring, "\015\012"), verstring);
        sk_write(ssh->s, verstring, strlen(verstring));
-       ssh->protocol = ssh1_protocol;
-       ssh->version = 1;
-       ssh->s_rdpkt = ssh1_rdpkt;
+        sfree(verstring);
     }
+
+    logeventf(ssh, "Using SSH protocol version %d", ssh->version);
+
     update_specials_menu(ssh->frontend);
     ssh->state = SSH_STATE_BEFORE_SIZE;
+    ssh->pinger = pinger_new(&ssh->cfg, &ssh_backend, ssh);
 
     sfree(s->vstring);
 
@@ -2261,6 +2358,7 @@ static void ssh_do_close(Ssh ssh)
     if (ssh->s) {
         sk_close(ssh->s);
         ssh->s = NULL;
+       notify_remote_exit(ssh->frontend);
     }
     /*
      * Now we must shut down any port and X forwardings going
@@ -2352,8 +2450,11 @@ static const char *connect_to_host(Ssh ssh, char *host, int port,
     /*
      * Try to find host.
      */
-    logeventf(ssh, "Looking up host \"%s\"", host);
-    addr = name_lookup(host, port, realhost, &ssh->cfg);
+    logeventf(ssh, "Looking up host \"%s\"%s", host,
+             (ssh->cfg.addressfamily == ADDRTYPE_IPV4 ? " (IPv4)" :
+              (ssh->cfg.addressfamily == ADDRTYPE_IPV6 ? " (IPv6)" : "")));
+    addr = name_lookup(host, port, realhost, &ssh->cfg,
+                      ssh->cfg.addressfamily);
     if ((err = sk_addr_error(addr)) != NULL) {
        sk_addr_free(addr);
        return err;
@@ -2372,6 +2473,7 @@ static const char *connect_to_host(Ssh ssh, char *host, int port,
                            0, 1, nodelay, keepalive, (Plug) ssh, &ssh->cfg);
     if ((err = sk_socket_error(ssh->s)) != NULL) {
        ssh->s = NULL;
+       notify_remote_exit(ssh->frontend);
        return err;
     }
 
@@ -2726,7 +2828,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 
        /* Warn about chosen cipher if necessary. */
        if (warn)
-           askcipher(ssh->frontend, cipher_string, 0);
+           askalg(ssh->frontend, "cipher", cipher_string);
     }
 
     switch (s->cipher_type) {
@@ -3481,221 +3583,785 @@ void sshfwd_unthrottle(struct ssh_channel *c, int bufsize)
     }
 }
 
-static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen,
-                         struct Packet *pktin)
+static void ssh_queueing_handler(Ssh ssh, struct Packet *pktin)
 {
-    crBegin(ssh->ssh1_protocol_crstate);
+    struct queued_handler *qh = ssh->qhead;
 
-    random_init();
+    assert(qh != NULL);
 
-    while (!do_ssh1_login(ssh, in, inlen, pktin)) {
-       crReturnV;
+    assert(pktin->type == qh->msg1 || pktin->type == qh->msg2);
+
+    if (qh->msg1 > 0) {
+       assert(ssh->packet_dispatch[qh->msg1] == ssh_queueing_handler);
+       ssh->packet_dispatch[qh->msg1] = NULL;
+    }
+    if (qh->msg2 > 0) {
+       assert(ssh->packet_dispatch[qh->msg2] == ssh_queueing_handler);
+       ssh->packet_dispatch[qh->msg2] = NULL;
     }
-    if (ssh->state == SSH_STATE_CLOSED)
-       crReturnV;
 
-    if (ssh->cfg.agentfwd && agent_exists()) {
-       logevent("Requesting agent forwarding");
-       send_packet(ssh, SSH1_CMSG_AGENT_REQUEST_FORWARDING, PKT_END);
-       do {
-           crReturnV;
-       } while (!pktin);
-       if (pktin->type != SSH1_SMSG_SUCCESS
-           && pktin->type != SSH1_SMSG_FAILURE) {
-           bombout(("Protocol confusion"));
-           crStopV;
-       } else if (pktin->type == SSH1_SMSG_FAILURE) {
-           logevent("Agent forwarding refused");
-       } else {
-           logevent("Agent forwarding enabled");
-           ssh->agentfwd_enabled = TRUE;
+    if (qh->next) {
+       ssh->qhead = qh->next;
+
+       if (ssh->qhead->msg1 > 0) {
+           assert(ssh->packet_dispatch[ssh->qhead->msg1] == NULL);
+           ssh->packet_dispatch[ssh->qhead->msg1] = ssh_queueing_handler;
        }
+       if (ssh->qhead->msg2 > 0) {
+           assert(ssh->packet_dispatch[ssh->qhead->msg2] == NULL);
+           ssh->packet_dispatch[ssh->qhead->msg2] = ssh_queueing_handler;
+       }
+    } else {
+       ssh->qhead = ssh->qtail = NULL;
+       ssh->packet_dispatch[pktin->type] = NULL;
     }
 
-    if (ssh->cfg.x11_forward) {
-       char proto[20], data[64];
-       logevent("Requesting X11 forwarding");
-       ssh->x11auth = x11_invent_auth(proto, sizeof(proto),
-                                      data, sizeof(data), ssh->cfg.x11_auth);
-        x11_get_real_auth(ssh->x11auth, ssh->cfg.x11_display);
-       if (ssh->v1_local_protoflags & SSH1_PROTOFLAG_SCREEN_NUMBER) {
-           send_packet(ssh, SSH1_CMSG_X11_REQUEST_FORWARDING,
-                       PKT_STR, proto, PKT_STR, data,
-                       PKT_INT, x11_get_screen_number(ssh->cfg.x11_display),
-                       PKT_END);
-       } else {
-           send_packet(ssh, SSH1_CMSG_X11_REQUEST_FORWARDING,
-                       PKT_STR, proto, PKT_STR, data, PKT_END);
+    qh->handler(ssh, pktin, qh->ctx);
+
+    sfree(qh);
+}
+
+static void ssh_queue_handler(Ssh ssh, int msg1, int msg2,
+                             chandler_fn_t handler, void *ctx)
+{
+    struct queued_handler *qh;
+
+    qh = snew(struct queued_handler);
+    qh->msg1 = msg1;
+    qh->msg2 = msg2;
+    qh->handler = handler;
+    qh->ctx = ctx;
+    qh->next = NULL;
+
+    if (ssh->qtail == NULL) {
+       ssh->qhead = qh;
+
+       if (qh->msg1 > 0) {
+           assert(ssh->packet_dispatch[qh->msg1] == NULL);
+           ssh->packet_dispatch[qh->msg1] = ssh_queueing_handler;
        }
-       do {
-           crReturnV;
-       } while (!pktin);
-       if (pktin->type != SSH1_SMSG_SUCCESS
-           && pktin->type != SSH1_SMSG_FAILURE) {
-           bombout(("Protocol confusion"));
-           crStopV;
-       } else if (pktin->type == SSH1_SMSG_FAILURE) {
-           logevent("X11 forwarding refused");
-       } else {
-           logevent("X11 forwarding enabled");
-           ssh->X11_fwd_enabled = TRUE;
+       if (qh->msg2 > 0) {
+           assert(ssh->packet_dispatch[qh->msg2] == NULL);
+           ssh->packet_dispatch[qh->msg2] = ssh_queueing_handler;
        }
+    } else {
+       ssh->qtail->next = qh;
     }
+    ssh->qtail = qh;
+}
 
-    {
-       char type;
-       int n;
-       int sport,dport,sserv,dserv;
-       char sports[256], dports[256], saddr[256], host[256];
-
-       ssh->rportfwds = newtree234(ssh_rportcmp_ssh1);
-        /* Add port forwardings. */
-       ssh->portfwd_strptr = ssh->cfg.portfwd;
-       while (*ssh->portfwd_strptr) {
-           type = *ssh->portfwd_strptr++;
-           saddr[0] = '\0';
-           n = 0;
-           while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != '\t') {
-               if (*ssh->portfwd_strptr == ':') {
-                   /*
-                    * We've seen a colon in the middle of the
-                    * source port number. This means that
-                    * everything we've seen until now is the
-                    * source _address_, so we'll move it into
-                    * saddr and start sports from the beginning
-                    * again.
-                    */
-                   ssh->portfwd_strptr++;
-                   sports[n] = '\0';
+static void ssh_rportfwd_succfail(Ssh ssh, struct Packet *pktin, void *ctx)
+{
+    struct ssh_rportfwd *rpf, *pf = (struct ssh_rportfwd *)ctx;
+
+    if (pktin->type == (ssh->version == 1 ? SSH1_SMSG_SUCCESS :
+                       SSH2_MSG_REQUEST_SUCCESS)) {
+       logeventf(ssh, "Remote port forwarding from %s enabled",
+                 pf->sportdesc);
+    } else {
+       logeventf(ssh, "Remote port forwarding from %s refused",
+                 pf->sportdesc);
+
+       rpf = del234(ssh->rportfwds, pf);
+       assert(rpf == pf);
+       free_rportfwd(pf);
+    }
+}
+
+static void ssh_setup_portfwd(Ssh ssh, const Config *cfg)
+{
+    char address_family, type;
+    int n;
+    int sport,dport,sserv,dserv;
+    char sports[256], dports[256], saddr[256], host[256];
+    const char *portfwd_strptr;
+
+    portfwd_strptr = cfg->portfwd;
+
+    if (!ssh->portfwds) {
+       ssh->portfwds = newtree234(ssh_portcmp);
+    } else {
+       /*
+        * Go through the existing port forwardings and tag them
+        * with keep==FALSE. Any that we want to keep will be
+        * re-enabled as we go through the configuration and find
+        * out which bits are the same as they were before.
+        */
+       struct ssh_portfwd *epf;
+       int i;
+       for (i = 0; (epf = index234(ssh->portfwds, i)) != NULL; i++)
+           epf->keep = FALSE;
+    }
+
+    while (*portfwd_strptr) {
+       address_family = 'A';
+       type = 'L';
+       while (*portfwd_strptr && *portfwd_strptr != '\t') {
+           if (*portfwd_strptr == 'A' ||
+               *portfwd_strptr == '4' ||
+               *portfwd_strptr == '6')
+               address_family = *portfwd_strptr;
+           else if (*portfwd_strptr == 'L' ||
+               *portfwd_strptr == 'R' ||
+               *portfwd_strptr == 'D')
+               type = *portfwd_strptr;
+           portfwd_strptr++;
+       }
+
+       saddr[0] = '\0';
+
+       n = 0;
+       while (*portfwd_strptr && *portfwd_strptr != '\t') {
+           if (*portfwd_strptr == ':') {
+               /*
+                * We've seen a colon in the middle of the
+                * source port number. This means that
+                * everything we've seen until now is the
+                * source _address_, so we'll move it into
+                * saddr and start sports from the beginning
+                * again.
+                */
+               portfwd_strptr++;
+               sports[n] = '\0';
+               if (ssh->version == 1 && type == 'R') {
+                   logeventf(ssh, "SSH1 cannot handle remote source address "
+                             "spec \"%s\"; ignoring", sports);
+               } else
                    strcpy(saddr, sports);
-                   n = 0;
-               }
-               if (n < 255) sports[n++] = *ssh->portfwd_strptr++;
-           }
-           sports[n] = 0;
-           if (type != 'D') {
-               if (*ssh->portfwd_strptr == '\t')
-                   ssh->portfwd_strptr++;
-               n = 0;
-               while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != ':') {
-                   if (n < 255) host[n++] = *ssh->portfwd_strptr++;
-               }
-               host[n] = 0;
-               if (*ssh->portfwd_strptr == ':')
-                   ssh->portfwd_strptr++;
                n = 0;
-               while (*ssh->portfwd_strptr) {
-                   if (n < 255) dports[n++] = *ssh->portfwd_strptr++;
-               }
-               dports[n] = 0;
-               ssh->portfwd_strptr++;
-               dport = atoi(dports);
-               dserv = 0;
-               if (dport == 0) {
-                   dserv = 1;
-                   dport = net_service_lookup(dports);
-                   if (!dport) {
-                       logeventf(ssh, "Service lookup failed for"
-                                 " destination port \"%s\"", dports);
-                   }
-               }
-           } else {
-               while (*ssh->portfwd_strptr) ssh->portfwd_strptr++;
-               dport = dserv = -1;
-               ssh->portfwd_strptr++; /* eat the NUL and move to next one */
            }
-           sport = atoi(sports);
-           sserv = 0;
-           if (sport == 0) {
-               sserv = 1;
-               sport = net_service_lookup(sports);
-               if (!sport) {
-                   logeventf(ssh, "Service lookup failed for source"
-                             " port \"%s\"", sports);
+           if (n < 255) sports[n++] = *portfwd_strptr++;
+       }
+       sports[n] = 0;
+       if (type != 'D') {
+           if (*portfwd_strptr == '\t')
+               portfwd_strptr++;
+           n = 0;
+           while (*portfwd_strptr && *portfwd_strptr != ':') {
+               if (n < 255) host[n++] = *portfwd_strptr++;
+           }
+           host[n] = 0;
+           if (*portfwd_strptr == ':')
+               portfwd_strptr++;
+           n = 0;
+           while (*portfwd_strptr) {
+               if (n < 255) dports[n++] = *portfwd_strptr++;
+           }
+           dports[n] = 0;
+           portfwd_strptr++;
+           dport = atoi(dports);
+           dserv = 0;
+           if (dport == 0) {
+               dserv = 1;
+               dport = net_service_lookup(dports);
+               if (!dport) {
+                   logeventf(ssh, "Service lookup failed for destination"
+                             " port \"%s\"", dports);
                }
            }
-           if (sport && dport) {
-               /* Set up a description of the source port. */
-               static char *sportdesc;
-               sportdesc = dupprintf("%.*s%.*s%.*s%.*s%d%.*s",
-                       (int)(*saddr?strlen(saddr):0), *saddr?saddr:NULL,
-                       (int)(*saddr?1:0), ":",
-                       (int)(sserv ? strlen(sports) : 0), sports,
-                       sserv, "(", sport, sserv, ")");
-               if (type == 'L') {
-                   /* Verbose description of the destination port */
-                   char *dportdesc = dupprintf("%s:%.*s%.*s%d%.*s",
-                           host,
-                           (int)(dserv ? strlen(dports) : 0), dports,
-                           dserv, "(", dport, dserv, ")");
-                   const char *err = pfd_addforward(host, dport,
-                                                    *saddr ? saddr : NULL,
-                                                    sport, ssh, &ssh->cfg);
-                   if (err) {
-                       logeventf(ssh, "Local port %s forward to %s"
-                                 " failed: %s", sportdesc, dportdesc, err);
-                   } else {
-                       logeventf(ssh, "Local port %s forwarding to %s",
-                                 sportdesc, dportdesc);
-                   }
-                   sfree(dportdesc);
-               } else if (type == 'D') {
-                   const char *err = pfd_addforward(NULL, -1,
-                                                    *saddr ? saddr : NULL,
-                                                    sport, ssh, &ssh->cfg);
-                   if (err) {
-                       logeventf(ssh, "Local port %s SOCKS dynamic forward"
-                                 " setup failed: %s", sportdesc, err);
-                   } else {
-                       logeventf(ssh, "Local port %s doing SOCKS"
-                                 " dynamic forwarding", sportdesc);
-                   }
-               } else {
-                   struct ssh_rportfwd *pf;
-                   pf = snew(struct ssh_rportfwd);
-                   strcpy(pf->dhost, host);
-                   pf->dport = dport;
-                   if (*saddr) {
-                       logeventf(ssh,
-                                 "SSH1 cannot handle source address spec \"%s:%d\"; ignoring",
-                                 saddr, sport);
-                   }
-                   if (add234(ssh->rportfwds, pf) != pf) {
-                       logeventf(ssh, 
-                                 "Duplicate remote port forwarding to %s:%d",
-                                 host, dport);
-                       sfree(pf);
-                   } else {
-                       logeventf(ssh, "Requesting remote port %.*s%.*s%d%.*s"
-                                 " forward to %s:%.*s%.*s%d%.*s",
+       } else {
+           while (*portfwd_strptr) portfwd_strptr++;
+           dport = dserv = -1;
+           portfwd_strptr++;          /* eat the NUL and move to next one */
+       }
+       sport = atoi(sports);
+       sserv = 0;
+       if (sport == 0) {
+           sserv = 1;
+           sport = net_service_lookup(sports);
+           if (!sport) {
+               logeventf(ssh, "Service lookup failed for source"
+                         " port \"%s\"", sports);
+           }
+       }
+       if (sport && dport) {
+           /* Set up a description of the source port. */
+           struct ssh_portfwd *pfrec, *epfrec;
+           char *sportdesc;
+           sportdesc = dupprintf("%.*s%.*s%.*s%.*s%d%.*s",
+                                 (int)(*saddr?strlen(saddr):0), *saddr?saddr:NULL,
+                                 (int)(*saddr?1:0), ":",
                                  (int)(sserv ? strlen(sports) : 0), sports,
-                                 sserv, "(", sport, sserv, ")",
-                                 host,
-                                 (int)(dserv ? strlen(dports) : 0), dports,
-                                 dserv, "(", dport, dserv, ")");
+                                 sserv, "(", sport, sserv, ")");
+
+           pfrec = snew(struct ssh_portfwd);
+           pfrec->type = type;
+           pfrec->saddr = *saddr ? dupstr(saddr) : NULL;
+           pfrec->sport = sport;
+           pfrec->daddr = dupstr(host);
+           pfrec->dport = dport;
+           pfrec->local = NULL;
+           pfrec->remote = NULL;
+           pfrec->addressfamily = (address_family == '4' ? ADDRTYPE_IPV4 :
+                                   address_family == '6' ? ADDRTYPE_IPV6 :
+                                   ADDRTYPE_UNSPEC);
+
+           epfrec = add234(ssh->portfwds, pfrec);
+           if (epfrec != pfrec) {
+               /*
+                * We already have a port forwarding with precisely
+                * these parameters. Hence, no need to do anything;
+                * simply tag the existing one as `keep'.
+                */
+               epfrec->keep = TRUE;
+               free_portfwd(pfrec);
+           } else if (type == 'L') {
+               /* Verbose description of the destination port */
+               char *dportdesc = dupprintf("%s:%.*s%.*s%d%.*s",
+                                           host,
+                                           (int)(dserv ? strlen(dports) : 0), dports,
+                                           dserv, "(", dport, dserv, ")");
+               const char *err = pfd_addforward(host, dport,
+                                                *saddr ? saddr : NULL,
+                                                sport, ssh, &ssh->cfg,
+                                                &pfrec->local,
+                                                pfrec->addressfamily);
+
+               logeventf(ssh, "Local %sport %s forward to %s%s%s",
+                         pfrec->addressfamily == ADDRTYPE_IPV4 ? "IPv4 " :
+                         pfrec->addressfamily == ADDRTYPE_IPV6 ? "IPv6 " : "",
+                         sportdesc, dportdesc,
+                         err ? " failed: " : "", err);
+
+               sfree(dportdesc);
+           } else if (type == 'D') {
+               const char *err = pfd_addforward(NULL, -1,
+                                                *saddr ? saddr : NULL,
+                                                sport, ssh, &ssh->cfg,
+                                                &pfrec->local,
+                                                pfrec->addressfamily);
+
+                       logeventf(ssh, "Local %sport %s SOCKS dynamic forward%s%s",
+                                 pfrec->addressfamily == ADDRTYPE_IPV4 ? "IPv4 " :
+                                 pfrec->addressfamily == ADDRTYPE_IPV6 ? "IPv6 " : "",
+                                 sportdesc,
+                                 err ? " setup failed: " : "", err);
+           } else {
+               struct ssh_rportfwd *pf;
+
+               /*
+                * Ensure the remote port forwardings tree exists.
+                */
+               if (!ssh->rportfwds) {
+                   if (ssh->version == 1)
+                       ssh->rportfwds = newtree234(ssh_rportcmp_ssh1);
+                   else
+                       ssh->rportfwds = newtree234(ssh_rportcmp_ssh2);
+               }
+
+               pf = snew(struct ssh_rportfwd);
+               strcpy(pf->dhost, host);
+               pf->dport = dport;
+               pf->sport = sport;
+               if (add234(ssh->rportfwds, pf) != pf) {
+                   logeventf(ssh, "Duplicate remote port forwarding to %s:%d",
+                             host, dport);
+                   sfree(pf);
+               } else {
+                   logeventf(ssh, "Requesting remote port %s"
+                             " forward to %s:%.*s%.*s%d%.*s",
+                             sportdesc, host,
+                             (int)(dserv ? strlen(dports) : 0), dports,
+                             dserv, "(", dport, dserv, ")");
+
+                   pf->sportdesc = sportdesc;
+                   sportdesc = NULL;
+                   pfrec->remote = pf;
+                   pf->pfrec = pfrec;
+
+                   if (ssh->version == 1) {
                        send_packet(ssh, SSH1_CMSG_PORT_FORWARD_REQUEST,
                                    PKT_INT, sport,
                                    PKT_STR, host,
                                    PKT_INT, dport,
                                    PKT_END);
-                       do {
-                           crReturnV;
-                       } while (!pktin);
-                       if (pktin->type != SSH1_SMSG_SUCCESS
-                           && pktin->type != SSH1_SMSG_FAILURE) {
-                           bombout(("Protocol confusion"));
-                           crStopV;
-                       } else if (pktin->type == SSH1_SMSG_FAILURE) {
-                           c_write_str(ssh, "Server refused port"
-                                       " forwarding\r\n");
+                       ssh_queue_handler(ssh, SSH1_SMSG_SUCCESS,
+                                         SSH1_SMSG_FAILURE,
+                                         ssh_rportfwd_succfail, pf);
+                   } else {
+                       struct Packet *pktout;
+                       pktout = ssh2_pkt_init(SSH2_MSG_GLOBAL_REQUEST);
+                       ssh2_pkt_addstring(pktout, "tcpip-forward");
+                       ssh2_pkt_addbool(pktout, 1);/* want reply */
+                       if (*saddr) {
+                           ssh2_pkt_addstring(pktout, saddr);
+                       } else if (ssh->cfg.rport_acceptall) {
+                           ssh2_pkt_addstring(pktout, "0.0.0.0");
+                       } else {
+                           ssh2_pkt_addstring(pktout, "127.0.0.1");
+                       }
+                       ssh2_pkt_adduint32(pktout, sport);
+                       ssh2_pkt_send(ssh, pktout);
+
+                       ssh_queue_handler(ssh, SSH2_MSG_REQUEST_SUCCESS,
+                                         SSH2_MSG_REQUEST_FAILURE,
+                                         ssh_rportfwd_succfail, pf);
+                   }
+               }
+           }
+           sfree(sportdesc);
+       }
+    }
+
+    /*
+     * Now go through and destroy any port forwardings which were
+     * not re-enabled.
+     */
+    {
+       struct ssh_portfwd *epf;
+       int i;
+       for (i = 0; (epf = index234(ssh->portfwds, i)) != NULL; i++)
+           if (!epf->keep) {
+               char *message;
+
+               message = dupprintf("%s port forwarding from %s%s%d",
+                                   epf->type == 'L' ? "local" :
+                                   epf->type == 'R' ? "remote" : "dynamic",
+                                   epf->saddr ? epf->saddr : "",
+                                   epf->saddr ? ":" : "",
+                                   epf->sport);
+
+               if (epf->type != 'D') {
+                   char *msg2 = dupprintf("%s to %s:%d", message,
+                                          epf->daddr, epf->dport);
+                   sfree(message);
+                   message = msg2;
+               }
+
+               logeventf(ssh, "Cancelling %s", message);
+               sfree(message);
+
+               if (epf->remote) {
+                   struct ssh_rportfwd *rpf = epf->remote;
+                   struct Packet *pktout;
+
+                   /*
+                    * Cancel the port forwarding at the server
+                    * end.
+                    */
+                   if (ssh->version == 1) {
+                       /*
+                        * We cannot cancel listening ports on the
+                        * server side in SSH1! There's no message
+                        * to support it. Instead, we simply remove
+                        * the rportfwd record from the local end
+                        * so that any connections the server tries
+                        * to make on it are rejected.
+                        */
+                   } else {
+                       pktout = ssh2_pkt_init(SSH2_MSG_GLOBAL_REQUEST);
+                       ssh2_pkt_addstring(pktout, "cancel-tcpip-forward");
+                       ssh2_pkt_addbool(pktout, 0);/* _don't_ want reply */
+                       if (epf->saddr) {
+                           ssh2_pkt_addstring(pktout, epf->saddr);
+                       } else if (ssh->cfg.rport_acceptall) {
+                           ssh2_pkt_addstring(pktout, "0.0.0.0");
+                       } else {
+                           ssh2_pkt_addstring(pktout, "127.0.0.1");
                        }
-                       logevent("Remote port forwarding enabled");
+                       ssh2_pkt_adduint32(pktout, epf->sport);
+                       ssh2_pkt_send(ssh, pktout);
                    }
+
+                   del234(ssh->rportfwds, rpf);
+                   free_rportfwd(rpf);
+               } else if (epf->local) {
+                   pfd_terminate(epf->local);
                }
-               sfree(sportdesc);
+
+               delpos234(ssh->portfwds, i);
+               free_portfwd(epf);
+               i--;                   /* so we don't skip one in the list */
            }
+    }
+}
+
+static void ssh1_smsg_stdout_stderr_data(Ssh ssh, struct Packet *pktin)
+{
+    char *string;
+    int stringlen, bufsize;
+
+    ssh_pkt_getstring(pktin, &string, &stringlen);
+    if (string == NULL) {
+       bombout(("Incoming terminal data packet was badly formed"));
+       return;
+    }
+
+    bufsize = from_backend(ssh->frontend, pktin->type == SSH1_SMSG_STDERR_DATA,
+                          string, stringlen);
+    if (!ssh->v1_stdout_throttling && bufsize > SSH1_BUFFER_LIMIT) {
+       ssh->v1_stdout_throttling = 1;
+       ssh1_throttle(ssh, +1);
+    }
+}
+
+static void ssh1_smsg_x11_open(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side is trying to open a channel to talk to our
+     * X-Server. Give them back a local channel number. */
+    struct ssh_channel *c;
+    int remoteid = ssh_pkt_getuint32(pktin);
+
+    logevent("Received X11 connect request");
+    /* Refuse if X11 forwarding is disabled. */
+    if (!ssh->X11_fwd_enabled) {
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                   PKT_INT, remoteid, PKT_END);
+       logevent("Rejected X11 connect request");
+    } else {
+       c = snew(struct ssh_channel);
+       c->ssh = ssh;
+
+       if (x11_init(&c->u.x11.s, ssh->cfg.x11_display, c,
+                    ssh->x11auth, NULL, -1, &ssh->cfg) != NULL) {
+           logevent("Opening X11 forward connection failed");
+           sfree(c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                       PKT_INT, remoteid, PKT_END);
+       } else {
+           logevent
+               ("Opening X11 forward connection succeeded");
+           c->remoteid = remoteid;
+           c->localid = alloc_channel_id(ssh);
+           c->closes = 0;
+           c->v.v1.throttling = 0;
+           c->type = CHAN_X11; /* identify channel type */
+           add234(ssh->channels, c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                       PKT_INT, c->remoteid, PKT_INT,
+                       c->localid, PKT_END);
+           logevent("Opened X11 forward channel");
+       }
+    }
+}
+
+static void ssh1_smsg_agent_open(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side is trying to open a channel to talk to our
+     * agent. Give them back a local channel number. */
+    struct ssh_channel *c;
+    int remoteid = ssh_pkt_getuint32(pktin);
+
+    /* Refuse if agent forwarding is disabled. */
+    if (!ssh->agentfwd_enabled) {
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                   PKT_INT, remoteid, PKT_END);
+    } else {
+       c = snew(struct ssh_channel);
+       c->ssh = ssh;
+       c->remoteid = remoteid;
+       c->localid = alloc_channel_id(ssh);
+       c->closes = 0;
+       c->v.v1.throttling = 0;
+       c->type = CHAN_AGENT;   /* identify channel type */
+       c->u.a.lensofar = 0;
+       add234(ssh->channels, c);
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                   PKT_INT, c->remoteid, PKT_INT, c->localid,
+                   PKT_END);
+    }
+}
+
+static void ssh1_msg_port_open(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side is trying to open a channel to talk to a
+     * forwarded port. Give them back a local channel number. */
+    struct ssh_channel *c;
+    struct ssh_rportfwd pf, *pfp;
+    int remoteid;
+    int hostsize, port;
+    char *host, buf[1024];
+    const char *e;
+    c = snew(struct ssh_channel);
+    c->ssh = ssh;
+
+    remoteid = ssh_pkt_getuint32(pktin);
+    ssh_pkt_getstring(pktin, &host, &hostsize);
+    port = ssh_pkt_getuint32(pktin);
+
+    if (hostsize >= lenof(pf.dhost))
+       hostsize = lenof(pf.dhost)-1;
+    memcpy(pf.dhost, host, hostsize);
+    pf.dhost[hostsize] = '\0';
+    pf.dport = port;
+    pfp = find234(ssh->rportfwds, &pf, NULL);
+
+    if (pfp == NULL) {
+       sprintf(buf, "Rejected remote port open request for %s:%d",
+               pf.dhost, port);
+       logevent(buf);
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                   PKT_INT, remoteid, PKT_END);
+    } else {
+       sprintf(buf, "Received remote port open request for %s:%d",
+               pf.dhost, port);
+       logevent(buf);
+       e = pfd_newconnect(&c->u.pfd.s, pf.dhost, port,
+                          c, &ssh->cfg, pfp->pfrec->addressfamily);
+       if (e != NULL) {
+           char buf[256];
+           sprintf(buf, "Port open failed: %s", e);
+           logevent(buf);
+           sfree(c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                       PKT_INT, remoteid, PKT_END);
+       } else {
+           c->remoteid = remoteid;
+           c->localid = alloc_channel_id(ssh);
+           c->closes = 0;
+           c->v.v1.throttling = 0;
+           c->type = CHAN_SOCKDATA;    /* identify channel type */
+           add234(ssh->channels, c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                       PKT_INT, c->remoteid, PKT_INT,
+                       c->localid, PKT_END);
+           logevent("Forwarded port opened successfully");
        }
     }
+}
+
+static void ssh1_msg_channel_open_confirmation(Ssh ssh, struct Packet *pktin)
+{
+    unsigned int remoteid = ssh_pkt_getuint32(pktin);
+    unsigned int localid = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+
+    c = find234(ssh->channels, &remoteid, ssh_channelfind);
+    if (c && c->type == CHAN_SOCKDATA_DORMANT) {
+       c->remoteid = localid;
+       c->type = CHAN_SOCKDATA;
+       c->v.v1.throttling = 0;
+       pfd_confirm(c->u.pfd.s);
+    }
+
+    if (c && c->closes) {
+       /*
+        * We have a pending close on this channel,
+        * which we decided on before the server acked
+        * the channel open. So now we know the
+        * remoteid, we can close it again.
+        */
+       send_packet(ssh, SSH1_MSG_CHANNEL_CLOSE,
+                   PKT_INT, c->remoteid, PKT_END);
+    }
+}
+
+static void ssh1_msg_channel_open_failure(Ssh ssh, struct Packet *pktin)
+{
+    unsigned int remoteid = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+
+    c = find234(ssh->channels, &remoteid, ssh_channelfind);
+    if (c && c->type == CHAN_SOCKDATA_DORMANT) {
+       logevent("Forwarded connection refused by server");
+       pfd_close(c->u.pfd.s);
+       del234(ssh->channels, c);
+       sfree(c);
+    }
+}
+
+static void ssh1_msg_channel_close(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side closes a channel. */
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (c && ((int)c->remoteid) != -1) {
+       int closetype;
+       closetype =
+           (pktin->type == SSH1_MSG_CHANNEL_CLOSE ? 1 : 2);
+
+       if ((c->closes == 0) && (c->type == CHAN_X11)) {
+           logevent("Forwarded X11 connection terminated");
+           assert(c->u.x11.s != NULL);
+           x11_close(c->u.x11.s);
+           c->u.x11.s = NULL;
+       }
+       if ((c->closes == 0) && (c->type == CHAN_SOCKDATA)) {
+           logevent("Forwarded port closed");
+           assert(c->u.pfd.s != NULL);
+           pfd_close(c->u.pfd.s);
+           c->u.pfd.s = NULL;
+       }
+
+       c->closes |= (closetype << 2);   /* seen this message */
+       if (!(c->closes & closetype)) {
+           send_packet(ssh, pktin->type, PKT_INT, c->remoteid,
+                       PKT_END);
+           c->closes |= closetype;      /* sent it too */
+       }
+
+       if (c->closes == 15) {
+           del234(ssh->channels, c);
+           sfree(c);
+       }
+    } else {
+       bombout(("Received CHANNEL_CLOSE%s for %s channel %d\n",
+                pktin->type == SSH1_MSG_CHANNEL_CLOSE ? "" :
+                "_CONFIRMATION", c ? "half-open" : "nonexistent",
+                i));
+    }
+}
+
+static void ssh1_msg_channel_data(Ssh ssh, struct Packet *pktin)
+{
+    /* Data sent down one of our channels. */
+    int i = ssh_pkt_getuint32(pktin);
+    char *p;
+    unsigned int len;
+    struct ssh_channel *c;
+
+    ssh_pkt_getstring(pktin, &p, &len);
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (c) {
+       int bufsize = 0;
+       switch (c->type) {
+         case CHAN_X11:
+           bufsize = x11_send(c->u.x11.s, p, len);
+           break;
+         case CHAN_SOCKDATA:
+           bufsize = pfd_send(c->u.pfd.s, p, len);
+           break;
+         case CHAN_AGENT:
+           /* Data for an agent message. Buffer it. */
+           while (len > 0) {
+               if (c->u.a.lensofar < 4) {
+                   unsigned int l = min(4 - c->u.a.lensofar, len);
+                   memcpy(c->u.a.msglen + c->u.a.lensofar, p,
+                          l);
+                   p += l;
+                   len -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == 4) {
+                   c->u.a.totallen =
+                       4 + GET_32BIT(c->u.a.msglen);
+                   c->u.a.message = snewn(c->u.a.totallen,
+                                          unsigned char);
+                   memcpy(c->u.a.message, c->u.a.msglen, 4);
+               }
+               if (c->u.a.lensofar >= 4 && len > 0) {
+                   unsigned int l =
+                       min(c->u.a.totallen - c->u.a.lensofar,
+                           len);
+                   memcpy(c->u.a.message + c->u.a.lensofar, p,
+                          l);
+                   p += l;
+                   len -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == c->u.a.totallen) {
+                   void *reply;
+                   int replylen;
+                   if (agent_query(c->u.a.message,
+                                   c->u.a.totallen,
+                                   &reply, &replylen,
+                                   ssh_agentf_callback, c))
+                       ssh_agentf_callback(c, reply, replylen);
+                   sfree(c->u.a.message);
+                   c->u.a.lensofar = 0;
+               }
+           }
+           bufsize = 0;   /* agent channels never back up */
+           break;
+       }
+       if (!c->v.v1.throttling && bufsize > SSH1_BUFFER_LIMIT) {
+           c->v.v1.throttling = 1;
+           ssh1_throttle(ssh, +1);
+       }
+    }
+}
+
+static void ssh1_smsg_exit_status(Ssh ssh, struct Packet *pktin)
+{
+    char buf[100];
+    ssh->exitcode = ssh_pkt_getuint32(pktin);
+    sprintf(buf, "Server sent command exit status %d",
+           ssh->exitcode);
+    logevent(buf);
+    send_packet(ssh, SSH1_CMSG_EXIT_CONFIRMATION, PKT_END);
+    /*
+     * In case `helpful' firewalls or proxies tack
+     * extra human-readable text on the end of the
+     * session which we might mistake for another
+     * encrypted packet, we close the session once
+     * we've sent EXIT_CONFIRMATION.
+     */
+    ssh_closing((Plug)ssh, NULL, 0, 0);
+}
+
+static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
+                              struct Packet *pktin)
+{
+    crBegin(ssh->do_ssh1_connection_crstate);
+
+    ssh->packet_dispatch[SSH1_SMSG_STDOUT_DATA] = 
+       ssh->packet_dispatch[SSH1_SMSG_STDERR_DATA] =
+       ssh1_smsg_stdout_stderr_data;
+
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_OPEN_CONFIRMATION] =
+       ssh1_msg_channel_open_confirmation;
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_OPEN_FAILURE] =
+       ssh1_msg_channel_open_failure;
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_CLOSE] =
+       ssh->packet_dispatch[SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION] =
+       ssh1_msg_channel_close;
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_DATA] = ssh1_msg_channel_data;
+    ssh->packet_dispatch[SSH1_SMSG_EXIT_STATUS] = ssh1_smsg_exit_status;
+
+    if (ssh->cfg.agentfwd && agent_exists()) {
+       logevent("Requesting agent forwarding");
+       send_packet(ssh, SSH1_CMSG_AGENT_REQUEST_FORWARDING, PKT_END);
+       do {
+           crReturnV;
+       } while (!pktin);
+       if (pktin->type != SSH1_SMSG_SUCCESS
+           && pktin->type != SSH1_SMSG_FAILURE) {
+           bombout(("Protocol confusion"));
+           crStopV;
+       } else if (pktin->type == SSH1_SMSG_FAILURE) {
+           logevent("Agent forwarding refused");
+       } else {
+           logevent("Agent forwarding enabled");
+           ssh->agentfwd_enabled = TRUE;
+           ssh->packet_dispatch[SSH1_SMSG_AGENT_OPEN] = ssh1_smsg_agent_open;
+       }
+    }
+
+    if (ssh->cfg.x11_forward) {
+       char proto[20], data[64];
+       logevent("Requesting X11 forwarding");
+       ssh->x11auth = x11_invent_auth(proto, sizeof(proto),
+                                      data, sizeof(data), ssh->cfg.x11_auth);
+        x11_get_real_auth(ssh->x11auth, ssh->cfg.x11_display);
+       if (ssh->v1_local_protoflags & SSH1_PROTOFLAG_SCREEN_NUMBER) {
+           send_packet(ssh, SSH1_CMSG_X11_REQUEST_FORWARDING,
+                       PKT_STR, proto, PKT_STR, data,
+                       PKT_INT, x11_get_screen_number(ssh->cfg.x11_display),
+                       PKT_END);
+       } else {
+           send_packet(ssh, SSH1_CMSG_X11_REQUEST_FORWARDING,
+                       PKT_STR, proto, PKT_STR, data, PKT_END);
+       }
+       do {
+           crReturnV;
+       } while (!pktin);
+       if (pktin->type != SSH1_SMSG_SUCCESS
+           && pktin->type != SSH1_SMSG_FAILURE) {
+           bombout(("Protocol confusion"));
+           crStopV;
+       } else if (pktin->type == SSH1_SMSG_FAILURE) {
+           logevent("X11 forwarding refused");
+       } else {
+           logevent("X11 forwarding enabled");
+           ssh->X11_fwd_enabled = TRUE;
+           ssh->packet_dispatch[SSH1_SMSG_X11_OPEN] = ssh1_smsg_x11_open;
+       }
+    }
+
+    ssh_setup_portfwd(ssh, &ssh->cfg);
+    ssh->packet_dispatch[SSH1_MSG_PORT_OPEN] = ssh1_msg_port_open;
 
     if (!ssh->cfg.nopty) {
        /* Unpick the terminal-speed string. */
@@ -3781,313 +4447,20 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen,
     ssh->send_ok = 1;
     ssh->channels = newtree234(ssh_channelcmp);
     while (1) {
-       crReturnV;
-       if (pktin) {
-           if (pktin->type == SSH1_SMSG_STDOUT_DATA ||
-               pktin->type == SSH1_SMSG_STDERR_DATA) {
-               char *string;
-               int stringlen, bufsize;
-
-               ssh_pkt_getstring(pktin, &string, &stringlen);
-               if (string == NULL) {
-                   bombout(("Incoming terminal data packet was badly formed"));
-                   crStopV;
-               }
-
-               bufsize =
-                   from_backend(ssh->frontend,
-                                pktin->type == SSH1_SMSG_STDERR_DATA,
-                                string, stringlen);
-               if (!ssh->v1_stdout_throttling && bufsize > SSH1_BUFFER_LIMIT) {
-                   ssh->v1_stdout_throttling = 1;
-                   ssh1_throttle(ssh, +1);
-               }
-           } else if (pktin->type == SSH1_MSG_DISCONNECT) {
-                ssh_closing((Plug)ssh, NULL, 0, 0);
-               logevent("Received disconnect request");
-               crStopV;
-           } else if (pktin->type == SSH1_SMSG_X11_OPEN) {
-               /* Remote side is trying to open a channel to talk to our
-                * X-Server. Give them back a local channel number. */
-               struct ssh_channel *c;
-               int remoteid = ssh_pkt_getuint32(pktin);
-
-               logevent("Received X11 connect request");
-               /* Refuse if X11 forwarding is disabled. */
-               if (!ssh->X11_fwd_enabled) {
-                   send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                               PKT_INT, remoteid, PKT_END);
-                   logevent("Rejected X11 connect request");
-               } else {
-                   c = snew(struct ssh_channel);
-                   c->ssh = ssh;
-
-                   if (x11_init(&c->u.x11.s, ssh->cfg.x11_display, c,
-                                ssh->x11auth, NULL, -1, &ssh->cfg) != NULL) {
-                       logevent("Opening X11 forward connection failed");
-                       sfree(c);
-                       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                   PKT_INT, remoteid, PKT_END);
-                   } else {
-                       logevent
-                           ("Opening X11 forward connection succeeded");
-                       c->remoteid = remoteid;
-                       c->localid = alloc_channel_id(ssh);
-                       c->closes = 0;
-                       c->v.v1.throttling = 0;
-                       c->type = CHAN_X11;     /* identify channel type */
-                       add234(ssh->channels, c);
-                       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
-                                   PKT_INT, c->remoteid, PKT_INT,
-                                   c->localid, PKT_END);
-                       logevent("Opened X11 forward channel");
-                   }
-               }
-           } else if (pktin->type == SSH1_SMSG_AGENT_OPEN) {
-               /* Remote side is trying to open a channel to talk to our
-                * agent. Give them back a local channel number. */
-               struct ssh_channel *c;
-               int remoteid = ssh_pkt_getuint32(pktin);
-
-               /* Refuse if agent forwarding is disabled. */
-               if (!ssh->agentfwd_enabled) {
-                   send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                               PKT_INT, remoteid, PKT_END);
-               } else {
-                   c = snew(struct ssh_channel);
-                   c->ssh = ssh;
-                   c->remoteid = remoteid;
-                   c->localid = alloc_channel_id(ssh);
-                   c->closes = 0;
-                   c->v.v1.throttling = 0;
-                   c->type = CHAN_AGENT;       /* identify channel type */
-                   c->u.a.lensofar = 0;
-                   add234(ssh->channels, c);
-                   send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
-                               PKT_INT, c->remoteid, PKT_INT, c->localid,
-                               PKT_END);
-               }
-           } else if (pktin->type == SSH1_MSG_PORT_OPEN) {
-               /* Remote side is trying to open a channel to talk to a
-                * forwarded port. Give them back a local channel number. */
-               struct ssh_channel *c;
-               struct ssh_rportfwd pf;
-               int remoteid;
-               int hostsize, port;
-               char *host, buf[1024];
-               const char *e;
-               c = snew(struct ssh_channel);
-               c->ssh = ssh;
-
-               remoteid = ssh_pkt_getuint32(pktin);
-               ssh_pkt_getstring(pktin, &host, &hostsize);
-               port = ssh_pkt_getuint32(pktin);
-
-               if (hostsize >= lenof(pf.dhost))
-                   hostsize = lenof(pf.dhost)-1;
-               memcpy(pf.dhost, host, hostsize);
-               pf.dhost[hostsize] = '\0';
-               pf.dport = port;
-
-               if (find234(ssh->rportfwds, &pf, NULL) == NULL) {
-                   sprintf(buf, "Rejected remote port open request for %s:%d",
-                           pf.dhost, port);
-                   logevent(buf);
-                    send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                PKT_INT, remoteid, PKT_END);
-               } else {
-                   sprintf(buf, "Received remote port open request for %s:%d",
-                           pf.dhost, port);
-                   logevent(buf);
-                   e = pfd_newconnect(&c->u.pfd.s, pf.dhost, port,
-                                      c, &ssh->cfg);
-                   if (e != NULL) {
-                       char buf[256];
-                       sprintf(buf, "Port open failed: %s", e);
-                       logevent(buf);
-                       sfree(c);
-                       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                   PKT_INT, remoteid, PKT_END);
-                   } else {
-                       c->remoteid = remoteid;
-                       c->localid = alloc_channel_id(ssh);
-                       c->closes = 0;
-                       c->v.v1.throttling = 0;
-                       c->type = CHAN_SOCKDATA;        /* identify channel type */
-                       add234(ssh->channels, c);
-                       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
-                                   PKT_INT, c->remoteid, PKT_INT,
-                                   c->localid, PKT_END);
-                       logevent("Forwarded port opened successfully");
-                   }
-               }
-
-           } else if (pktin->type == SSH1_MSG_CHANNEL_OPEN_CONFIRMATION) {
-               unsigned int remoteid = ssh_pkt_getuint32(pktin);
-               unsigned int localid = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-
-               c = find234(ssh->channels, &remoteid, ssh_channelfind);
-               if (c && c->type == CHAN_SOCKDATA_DORMANT) {
-                   c->remoteid = localid;
-                   c->type = CHAN_SOCKDATA;
-                   c->v.v1.throttling = 0;
-                   pfd_confirm(c->u.pfd.s);
-               }
-
-               if (c && c->closes) {
-                   /*
-                    * We have a pending close on this channel,
-                    * which we decided on before the server acked
-                    * the channel open. So now we know the
-                    * remoteid, we can close it again.
-                    */
-                   send_packet(ssh, SSH1_MSG_CHANNEL_CLOSE,
-                               PKT_INT, c->remoteid, PKT_END);
-               }
-
-           } else if (pktin->type == SSH1_MSG_CHANNEL_OPEN_FAILURE) {
-               unsigned int remoteid = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
 
-               c = find234(ssh->channels, &remoteid, ssh_channelfind);
-               if (c && c->type == CHAN_SOCKDATA_DORMANT) {
-                   logevent("Forwarded connection refused by server");
-                   pfd_close(c->u.pfd.s);
-                   del234(ssh->channels, c);
-                   sfree(c);
-               }
-
-           } else if (pktin->type == SSH1_MSG_CHANNEL_CLOSE ||
-                      pktin->type == SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION) {
-               /* Remote side closes a channel. */
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (c && ((int)c->remoteid) != -1) {
-                   int closetype;
-                   closetype =
-                       (pktin->type == SSH1_MSG_CHANNEL_CLOSE ? 1 : 2);
-
-                   if ((c->closes == 0) && (c->type == CHAN_X11)) {
-                       logevent("Forwarded X11 connection terminated");
-                       assert(c->u.x11.s != NULL);
-                       x11_close(c->u.x11.s);
-                       c->u.x11.s = NULL;
-                   }
-                   if ((c->closes == 0) && (c->type == CHAN_SOCKDATA)) {
-                       logevent("Forwarded port closed");
-                       assert(c->u.pfd.s != NULL);
-                       pfd_close(c->u.pfd.s);
-                       c->u.pfd.s = NULL;
-                   }
-
-                   c->closes |= (closetype << 2);   /* seen this message */
-                   if (!(c->closes & closetype)) {
-                       send_packet(ssh, pktin->type, PKT_INT, c->remoteid,
-                                   PKT_END);
-                       c->closes |= closetype;      /* sent it too */
-                   }
+       /*
+        * By this point, most incoming packets are already being
+        * handled by the dispatch table, and we need only pay
+        * attention to the unusual ones.
+        */
 
-                   if (c->closes == 15) {
-                       del234(ssh->channels, c);
-                       sfree(c);
-                   }
-               } else {
-                   bombout(("Received CHANNEL_CLOSE%s for %s channel %d\n",
-                            pktin->type == SSH1_MSG_CHANNEL_CLOSE ? "" :
-                            "_CONFIRMATION", c ? "half-open" : "nonexistent",
-                            i));
-                   crStopV;
-               }
-           } else if (pktin->type == SSH1_MSG_CHANNEL_DATA) {
-               /* Data sent down one of our channels. */
-               int i = ssh_pkt_getuint32(pktin);
-               char *p;
-               int len;
-               struct ssh_channel *c;
-
-               ssh_pkt_getstring(pktin, &p, &len);
-
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (c) {
-                   int bufsize = 0;
-                   switch (c->type) {
-                     case CHAN_X11:
-                       bufsize = x11_send(c->u.x11.s, p, len);
-                       break;
-                     case CHAN_SOCKDATA:
-                       bufsize = pfd_send(c->u.pfd.s, p, len);
-                       break;
-                     case CHAN_AGENT:
-                       /* Data for an agent message. Buffer it. */
-                       while (len > 0) {
-                           if (c->u.a.lensofar < 4) {
-                               int l = min(4 - c->u.a.lensofar, len);
-                               memcpy(c->u.a.msglen + c->u.a.lensofar, p,
-                                      l);
-                               p += l;
-                               len -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == 4) {
-                               c->u.a.totallen =
-                                   4 + GET_32BIT(c->u.a.msglen);
-                               c->u.a.message = snewn(c->u.a.totallen,
-                                                      unsigned char);
-                               memcpy(c->u.a.message, c->u.a.msglen, 4);
-                           }
-                           if (c->u.a.lensofar >= 4 && len > 0) {
-                               int l =
-                                   min(c->u.a.totallen - c->u.a.lensofar,
-                                       len);
-                               memcpy(c->u.a.message + c->u.a.lensofar, p,
-                                      l);
-                               p += l;
-                               len -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == c->u.a.totallen) {
-                               void *reply;
-                               int replylen;
-                               if (agent_query(c->u.a.message,
-                                               c->u.a.totallen,
-                                               &reply, &replylen,
-                                               ssh_agentf_callback, c))
-                                   ssh_agentf_callback(c, reply, replylen);
-                               sfree(c->u.a.message);
-                               c->u.a.lensofar = 0;
-                           }
-                       }
-                       bufsize = 0;   /* agent channels never back up */
-                       break;
-                   }
-                   if (!c->v.v1.throttling && bufsize > SSH1_BUFFER_LIMIT) {
-                       c->v.v1.throttling = 1;
-                       ssh1_throttle(ssh, +1);
-                   }
-               }
-           } else if (pktin->type == SSH1_SMSG_SUCCESS) {
+       crReturnV;
+       if (pktin) {
+           if (pktin->type == SSH1_SMSG_SUCCESS) {
                /* may be from EXEC_SHELL on some servers */
            } else if (pktin->type == SSH1_SMSG_FAILURE) {
                /* may be from EXEC_SHELL on some servers
                 * if no pty is available or in other odd cases. Ignore */
-           } else if (pktin->type == SSH1_SMSG_EXIT_STATUS) {
-               char buf[100];
-               ssh->exitcode = ssh_pkt_getuint32(pktin);
-               sprintf(buf, "Server sent command exit status %d",
-                       ssh->exitcode);
-               logevent(buf);
-               send_packet(ssh, SSH1_CMSG_EXIT_CONFIRMATION, PKT_END);
-                /*
-                 * In case `helpful' firewalls or proxies tack
-                 * extra human-readable text on the end of the
-                 * session which we might mistake for another
-                 * encrypted packet, we close the session once
-                 * we've sent EXIT_CONFIRMATION.
-                 */
-                ssh_closing((Plug)ssh, NULL, 0, 0);
-                crStopV;
            } else {
                bombout(("Strange packet received: type %d", pktin->type));
                crStopV;
@@ -4108,6 +4481,74 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen,
 }
 
 /*
+ * Handle the top-level SSH2 protocol.
+ */
+static void ssh1_msg_debug(Ssh ssh, struct Packet *pktin)
+{
+    char *buf, *msg;
+    int msglen;
+
+    ssh_pkt_getstring(pktin, &msg, &msglen);
+    buf = dupprintf("Remote debug message: %.*s", msglen, msg);
+    logevent(buf);
+    sfree(buf);
+}
+
+static void ssh1_msg_disconnect(Ssh ssh, struct Packet *pktin)
+{
+    /* log reason code in disconnect message */
+    char *msg;
+    int msglen;
+
+    ssh_pkt_getstring(pktin, &msg, &msglen);
+    bombout(("Server sent disconnect message:\n\"%.*s\"", msglen, msg));
+}
+
+void ssh_msg_ignore(Ssh ssh, struct Packet *pktin)
+{
+    /* Do nothing, because we're ignoring it! Duhh. */
+}
+
+static void ssh1_protocol_setup(Ssh ssh)
+{
+    int i;
+
+    /*
+     * Most messages are handled by the coroutines.
+     */
+    for (i = 0; i < 256; i++)
+       ssh->packet_dispatch[i] = NULL;
+
+    /*
+     * These special message types we install handlers for.
+     */
+    ssh->packet_dispatch[SSH1_MSG_DISCONNECT] = ssh1_msg_disconnect;
+    ssh->packet_dispatch[SSH1_MSG_IGNORE] = ssh_msg_ignore;
+    ssh->packet_dispatch[SSH1_MSG_DEBUG] = ssh1_msg_debug;
+}
+
+static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen,
+                         struct Packet *pktin)
+{
+    if (ssh->state == SSH_STATE_CLOSED)
+       return;
+
+    if (pktin && ssh->packet_dispatch[pktin->type]) {
+       ssh->packet_dispatch[pktin->type](ssh, pktin);
+       return;
+    }
+
+    if (!ssh->protocol_initial_phase_done) {
+       if (do_ssh1_login(ssh, in, inlen, pktin))
+           ssh->protocol_initial_phase_done = TRUE;
+       else
+           return;
+    }
+
+    do_ssh1_connection(ssh, in, inlen, pktin);
+}
+
+/*
  * Utility routine for decoding comma-separated strings in KEXINIT.
  */
 static int in_commasep_string(char *needle, char *haystack, int haylen)
@@ -4185,6 +4626,8 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
        int hostkeylen, siglen;
        void *hkey;                    /* actual host key */
        unsigned char exchange_hash[20];
+       int n_preferred_kex;
+       const struct ssh_kex *preferred_kex[KEX_MAX];
        int n_preferred_ciphers;
        const struct ssh2_ciphers *preferred_ciphers[CIPHER_MAX];
        const struct ssh_compress *preferred_comp;
@@ -4199,12 +4642,42 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     s->csmac_tobe = s->scmac_tobe = NULL;
     s->cscomp_tobe = s->sccomp_tobe = NULL;
 
-    random_init();
     s->first_kex = 1;
 
     {
        int i;
        /*
+        * Set up the preferred key exchange. (NULL => warn below here)
+        */
+       s->n_preferred_kex = 0;
+       for (i = 0; i < KEX_MAX; i++) {
+           switch (ssh->cfg.ssh_kexlist[i]) {
+             case KEX_DHGEX:
+               s->preferred_kex[s->n_preferred_kex++] =
+                   &ssh_diffiehellman_gex;
+               break;
+             case KEX_DHGROUP14:
+               s->preferred_kex[s->n_preferred_kex++] =
+                   &ssh_diffiehellman_group14;
+               break;
+             case KEX_DHGROUP1:
+               s->preferred_kex[s->n_preferred_kex++] =
+                   &ssh_diffiehellman_group1;
+               break;
+             case CIPHER_WARN:
+               /* Flag for later. Don't bother if it's the last in
+                * the list. */
+               if (i < KEX_MAX - 1) {
+                   s->preferred_kex[s->n_preferred_kex++] = NULL;
+               }
+               break;
+           }
+       }
+    }
+
+    {
+       int i;
+       /*
         * Set up the preferred ciphers. (NULL => warn below here)
         */
        s->n_preferred_ciphers = 0;
@@ -4253,7 +4726,18 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 
   begin_key_exchange:
     {
-       int i, j, cipherstr_started;
+       int i, j, commalist_started;
+
+       /*
+        * Enable queueing of outgoing auth- or connection-layer
+        * packets while we are in the middle of a key exchange.
+        */
+       ssh->queueing = TRUE;
+
+       /*
+        * Flag that KEX is in progress.
+        */
+       ssh->kex_in_progress = TRUE;
 
        /*
         * Construct and send our key exchange packet.
@@ -4263,13 +4747,14 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
            ssh2_pkt_addbyte(s->pktout, (unsigned char) random_byte());
        /* List key exchange algorithms. */
        ssh2_pkt_addstring_start(s->pktout);
-       for (i = 0; i < lenof(kex_algs); i++) {
-           if (kex_algs[i] == &ssh_diffiehellman_gex &&
-               (ssh->remote_bugs & BUG_SSH2_DH_GEX))
-               continue;
-           ssh2_pkt_addstring_str(s->pktout, kex_algs[i]->name);
-           if (i < lenof(kex_algs) - 1)
+       commalist_started = 0;
+       for (i = 0; i < s->n_preferred_kex; i++) {
+           const struct ssh_kex *k = s->preferred_kex[i];
+           if (!k) continue;          /* warning flag */
+           if (commalist_started)
                ssh2_pkt_addstring_str(s->pktout, ",");
+           ssh2_pkt_addstring_str(s->pktout, s->preferred_kex[i]->name);
+           commalist_started = 1;
        }
        /* List server host key algorithms. */
        ssh2_pkt_addstring_start(s->pktout);
@@ -4280,28 +4765,28 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
        }
        /* List client->server encryption algorithms. */
        ssh2_pkt_addstring_start(s->pktout);
-       cipherstr_started = 0;
+       commalist_started = 0;
        for (i = 0; i < s->n_preferred_ciphers; i++) {
            const struct ssh2_ciphers *c = s->preferred_ciphers[i];
            if (!c) continue;          /* warning flag */
            for (j = 0; j < c->nciphers; j++) {
-               if (cipherstr_started)
+               if (commalist_started)
                    ssh2_pkt_addstring_str(s->pktout, ",");
                ssh2_pkt_addstring_str(s->pktout, c->list[j]->name);
-               cipherstr_started = 1;
+               commalist_started = 1;
            }
        }
        /* List server->client encryption algorithms. */
        ssh2_pkt_addstring_start(s->pktout);
-       cipherstr_started = 0;
+       commalist_started = 0;
        for (i = 0; i < s->n_preferred_ciphers; i++) {
            const struct ssh2_ciphers *c = s->preferred_ciphers[i];
            if (!c) continue; /* warning flag */
            for (j = 0; j < c->nciphers; j++) {
-               if (cipherstr_started)
+               if (commalist_started)
                    ssh2_pkt_addstring_str(s->pktout, ",");
                ssh2_pkt_addstring_str(s->pktout, c->list[j]->name);
-               cipherstr_started = 1;
+               commalist_started = 1;
            }
        }
        /* List client->server MAC algorithms. */
@@ -4353,7 +4838,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     ssh->exhash = ssh->exhashbase;
     sha_string(&ssh->exhash, s->pktout->data + 5, s->pktout->length - 5);
 
-    ssh2_pkt_send(ssh, s->pktout);
+    ssh2_pkt_send_noqueue(ssh, s->pktout);
 
     if (!pktin)
        crWaitUntil(pktin);
@@ -4382,15 +4867,26 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
        s->sccomp_tobe = NULL;
        pktin->savedpos += 16;          /* skip garbage cookie */
        ssh_pkt_getstring(pktin, &str, &len);    /* key exchange algorithms */
-       for (i = 0; i < lenof(kex_algs); i++) {
-           if (kex_algs[i] == &ssh_diffiehellman_gex &&
-               (ssh->remote_bugs & BUG_SSH2_DH_GEX))
-               continue;
-           if (in_commasep_string(kex_algs[i]->name, str, len)) {
-               ssh->kex = kex_algs[i];
+       s->warn = 0;
+       for (i = 0; i < s->n_preferred_kex; i++) {
+           const struct ssh_kex *k = s->preferred_kex[i];
+           if (!k) {
+               s->warn = 1;
+           } else if (in_commasep_string(k->name, str, len)) {
+               ssh->kex = k;
+           }
+           if (ssh->kex) {
+               if (s->warn)
+                   askalg(ssh->frontend, "key-exchange algorithm",
+                          ssh->kex->name);
                break;
            }
        }
+       if (!ssh->kex) {
+           bombout(("Couldn't agree a key exchange algorithm (available: %s)",
+                    str ? str : "(null)"));
+           crStop(0);
+       }
        ssh_pkt_getstring(pktin, &str, &len);    /* host key algorithms */
        for (i = 0; i < lenof(hostkey_algs); i++) {
            if (in_commasep_string(hostkey_algs[i]->name, str, len)) {
@@ -4414,7 +4910,8 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
            }
            if (s->cscipher_tobe) {
                if (s->warn)
-                   askcipher(ssh->frontend, s->cscipher_tobe->name, 1);
+                   askalg(ssh->frontend, "client-to-server cipher",
+                          s->cscipher_tobe->name);
                break;
            }
        }
@@ -4440,7 +4937,8 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
            }
            if (s->sccipher_tobe) {
                if (s->warn)
-                   askcipher(ssh->frontend, s->sccipher_tobe->name, 2);
+                   askalg(ssh->frontend, "server-to-client cipher",
+                          s->sccipher_tobe->name);
                break;
            }
        }
@@ -4505,7 +5003,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      * If we're doing Diffie-Hellman group exchange, start by
      * requesting a group.
      */
-    if (ssh->kex == &ssh_diffiehellman_gex) {
+    if (!ssh->kex->pdata) {
        logevent("Doing Diffie-Hellman group exchange");
        ssh->pkt_ctx |= SSH2_PKTCTX_DHGEX;
        /*
@@ -4515,7 +5013,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
        s->pbits = 512 << ((s->nbits - 1) / 64);
        s->pktout = ssh2_pkt_init(SSH2_MSG_KEX_DH_GEX_REQUEST);
        ssh2_pkt_adduint32(s->pktout, s->pbits);
-       ssh2_pkt_send(ssh, s->pktout);
+       ssh2_pkt_send_noqueue(ssh, s->pktout);
 
        crWaitUntil(pktin);
        if (pktin->type != SSH2_MSG_KEX_DH_GEX_GROUP) {
@@ -4528,14 +5026,16 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
            bombout(("unable to read mp-ints from incoming group packet"));
            crStop(0);
        }
-       ssh->kex_ctx = dh_setup_group(s->p, s->g);
+       ssh->kex_ctx = dh_setup_gex(s->p, s->g);
        s->kex_init_value = SSH2_MSG_KEX_DH_GEX_INIT;
        s->kex_reply_value = SSH2_MSG_KEX_DH_GEX_REPLY;
     } else {
-       ssh->pkt_ctx |= SSH2_PKTCTX_DHGROUP1;
-       ssh->kex_ctx = dh_setup_group1();
+       ssh->pkt_ctx |= SSH2_PKTCTX_DHGROUP;
+       ssh->kex_ctx = dh_setup_group(ssh->kex);
        s->kex_init_value = SSH2_MSG_KEXDH_INIT;
        s->kex_reply_value = SSH2_MSG_KEXDH_REPLY;
+       logeventf(ssh, "Using Diffie-Hellman with standard group \"%s\"",
+                 ssh->kex->groupname);
     }
 
     logevent("Doing Diffie-Hellman key exchange");
@@ -4545,7 +5045,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     s->e = dh_create_e(ssh->kex_ctx, s->nbits * 2);
     s->pktout = ssh2_pkt_init(s->kex_init_value);
     ssh2_pkt_addmp(s->pktout, s->e);
-    ssh2_pkt_send(ssh, s->pktout);
+    ssh2_pkt_send_noqueue(ssh, s->pktout);
 
     crWaitUntil(pktin);
     if (pktin->type != s->kex_reply_value) {
@@ -4590,27 +5090,85 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     }
 
     /*
-     * Authenticate remote host: verify host key. (We've already
-     * checked the signature of the exchange hash.)
+     * Authenticate remote host: verify host key. (We've already
+     * checked the signature of the exchange hash.)
+     */
+    s->keystr = ssh->hostkey->fmtkey(s->hkey);
+    s->fingerprint = ssh->hostkey->fingerprint(s->hkey);
+    verify_ssh_host_key(ssh->frontend,
+                       ssh->savedhost, ssh->savedport, ssh->hostkey->keytype,
+                       s->keystr, s->fingerprint);
+    if (s->first_kex) {                       /* don't bother logging this in rekeys */
+       logevent("Host key fingerprint is:");
+       logevent(s->fingerprint);
+    }
+    sfree(s->fingerprint);
+    sfree(s->keystr);
+    ssh->hostkey->freekey(s->hkey);
+
+    /*
+     * The exchange hash from the very first key exchange is also
+     * the session id, used in session key construction and
+     * authentication.
+     */
+    if (s->first_kex)
+       memcpy(ssh->v2_session_id, s->exchange_hash,
+              sizeof(s->exchange_hash));
+
+    /*
+     * Send SSH2_MSG_NEWKEYS.
+     */
+    s->pktout = ssh2_pkt_init(SSH2_MSG_NEWKEYS);
+    ssh2_pkt_send_noqueue(ssh, s->pktout);
+    ssh->outgoing_data_size = 0;       /* start counting from here */
+
+    /*
+     * We've sent client NEWKEYS, so create and initialise
+     * client-to-server session keys.
+     */
+    if (ssh->cs_cipher_ctx)
+       ssh->cscipher->free_context(ssh->cs_cipher_ctx);
+    ssh->cscipher = s->cscipher_tobe;
+    ssh->cs_cipher_ctx = ssh->cscipher->make_context();
+
+    if (ssh->cs_mac_ctx)
+       ssh->csmac->free_context(ssh->cs_mac_ctx);
+    ssh->csmac = s->csmac_tobe;
+    ssh->cs_mac_ctx = ssh->csmac->make_context();
+
+    if (ssh->cs_comp_ctx)
+       ssh->cscomp->compress_cleanup(ssh->cs_comp_ctx);
+    ssh->cscomp = s->cscomp_tobe;
+    ssh->cs_comp_ctx = ssh->cscomp->compress_init();
+
+    /*
+     * Set IVs on client-to-server keys. Here we use the exchange
+     * hash from the _first_ key exchange.
      */
-    s->keystr = ssh->hostkey->fmtkey(s->hkey);
-    s->fingerprint = ssh->hostkey->fingerprint(s->hkey);
-    verify_ssh_host_key(ssh->frontend,
-                       ssh->savedhost, ssh->savedport, ssh->hostkey->keytype,
-                       s->keystr, s->fingerprint);
-    if (s->first_kex) {                       /* don't bother logging this in rekeys */
-       logevent("Host key fingerprint is:");
-       logevent(s->fingerprint);
+    {
+       unsigned char keyspace[40];
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'C',keyspace);
+       ssh->cscipher->setkey(ssh->cs_cipher_ctx, keyspace);
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'A',keyspace);
+       ssh->cscipher->setiv(ssh->cs_cipher_ctx, keyspace);
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'E',keyspace);
+       ssh->csmac->setkey(ssh->cs_mac_ctx, keyspace);
     }
-    sfree(s->fingerprint);
-    sfree(s->keystr);
-    ssh->hostkey->freekey(s->hkey);
+
+    logeventf(ssh, "Initialised %.200s client->server encryption",
+             ssh->cscipher->text_name);
+    logeventf(ssh, "Initialised %.200s client->server MAC algorithm",
+             ssh->csmac->text_name);
+    if (ssh->cscomp->text_name)
+       logeventf(ssh, "Initialised %s compression",
+                 ssh->cscomp->text_name);
 
     /*
-     * Send SSH2_MSG_NEWKEYS.
+     * Now our end of the key exchange is complete, we can send all
+     * our queued higher-layer packets.
      */
-    s->pktout = ssh2_pkt_init(SSH2_MSG_NEWKEYS);
-    ssh2_pkt_send(ssh, s->pktout);
+    ssh->queueing = FALSE;
+    ssh2_pkt_queuesend(ssh);
 
     /*
      * Expect SSH2_MSG_NEWKEYS from server.
@@ -4620,76 +5178,51 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
        bombout(("expected new-keys packet from server"));
        crStop(0);
     }
+    ssh->incoming_data_size = 0;       /* start counting from here */
 
     /*
-     * Create and initialise session keys.
+     * We've seen server NEWKEYS, so create and initialise
+     * server-to-client session keys.
      */
-    if (ssh->cs_cipher_ctx)
-       ssh->cscipher->free_context(ssh->cs_cipher_ctx);
-    ssh->cscipher = s->cscipher_tobe;
-    ssh->cs_cipher_ctx = ssh->cscipher->make_context();
-
     if (ssh->sc_cipher_ctx)
        ssh->sccipher->free_context(ssh->sc_cipher_ctx);
     ssh->sccipher = s->sccipher_tobe;
     ssh->sc_cipher_ctx = ssh->sccipher->make_context();
 
-    if (ssh->cs_mac_ctx)
-       ssh->csmac->free_context(ssh->cs_mac_ctx);
-    ssh->csmac = s->csmac_tobe;
-    ssh->cs_mac_ctx = ssh->csmac->make_context();
-
     if (ssh->sc_mac_ctx)
        ssh->scmac->free_context(ssh->sc_mac_ctx);
     ssh->scmac = s->scmac_tobe;
     ssh->sc_mac_ctx = ssh->scmac->make_context();
 
-    if (ssh->cs_comp_ctx)
-       ssh->cscomp->compress_cleanup(ssh->cs_comp_ctx);
-    ssh->cscomp = s->cscomp_tobe;
-    ssh->cs_comp_ctx = ssh->cscomp->compress_init();
-
     if (ssh->sc_comp_ctx)
        ssh->sccomp->decompress_cleanup(ssh->sc_comp_ctx);
     ssh->sccomp = s->sccomp_tobe;
     ssh->sc_comp_ctx = ssh->sccomp->decompress_init();
 
     /*
-     * Set IVs after keys. Here we use the exchange hash from the
-     * _first_ key exchange.
+     * Set IVs on server-to-client keys. Here we use the exchange
+     * hash from the _first_ key exchange.
      */
     {
        unsigned char keyspace[40];
-       if (s->first_kex)
-           memcpy(ssh->v2_session_id, s->exchange_hash,
-                  sizeof(s->exchange_hash));
-       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'C',keyspace);
-       ssh->cscipher->setkey(ssh->cs_cipher_ctx, keyspace);
        ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'D',keyspace);
        ssh->sccipher->setkey(ssh->sc_cipher_ctx, keyspace);
-       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'A',keyspace);
-       ssh->cscipher->setiv(ssh->cs_cipher_ctx, keyspace);
        ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'B',keyspace);
        ssh->sccipher->setiv(ssh->sc_cipher_ctx, keyspace);
-       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'E',keyspace);
-       ssh->csmac->setkey(ssh->cs_mac_ctx, keyspace);
        ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'F',keyspace);
        ssh->scmac->setkey(ssh->sc_mac_ctx, keyspace);
     }
-    logeventf(ssh, "Initialised %.200s client->server encryption",
-             ssh->cscipher->text_name);
     logeventf(ssh, "Initialised %.200s server->client encryption",
              ssh->sccipher->text_name);
-    logeventf(ssh, "Initialised %.200s client->server MAC algorithm",
-             ssh->csmac->text_name);
     logeventf(ssh, "Initialised %.200s server->client MAC algorithm",
              ssh->scmac->text_name);
-    if (ssh->cscomp->text_name)
-       logeventf(ssh, "Initialised %s compression",
-                 ssh->cscomp->text_name);
     if (ssh->sccomp->text_name)
        logeventf(ssh, "Initialised %s decompression",
                  ssh->sccomp->text_name);
+
+    /*
+     * Free key exchange data.
+     */
     freebn(s->f);
     freebn(s->K);
     if (ssh->kex == &ssh_diffiehellman_gex) {
@@ -4698,6 +5231,15 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     }
 
     /*
+     * Key exchange is over. Schedule a timer for our next rekey.
+     */
+    ssh->kex_in_progress = FALSE;
+    ssh->last_rekey = GETTICKCOUNT();
+    if (ssh->cfg.ssh_rekey_time != 0)
+       ssh->next_rekey = schedule_timer(ssh->cfg.ssh_rekey_time*60*TICKSPERSEC,
+                                        ssh2_timer, ssh);
+    
+    /*
      * If this is the first key exchange phase, we must pass the
      * SSH2_MSG_NEWKEYS packet to the next layer, not because it
      * wants to see it but because it will need time to initialise
@@ -4706,7 +5248,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      * it would only confuse the layer above.
      */
     if (!s->first_kex) {
-       crReturn(0);
+       crReturn(1);
     }
     s->first_kex = 0;
 
@@ -4715,11 +5257,21 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      * function so that other things can run on top of the
      * transport. If we ever see a KEXINIT, we must go back to the
      * start.
+     * 
+     * We _also_ go back to the start if we see pktin==NULL and
+     * inlen==-1, because this is a special signal meaning
+     * `initiate client-driven rekey', and `in' contains a message
+     * giving the reason for the rekey.
      */
-    while (!(pktin && pktin->type == SSH2_MSG_KEXINIT)) {
+    while (!((pktin && pktin->type == SSH2_MSG_KEXINIT) ||
+            (!pktin && inlen == -1))) {
        crReturn(1);
     }
-    logevent("Server initiated key re-exchange");
+    if (pktin) {
+       logevent("Server initiated key re-exchange");
+    } else {
+       logevent((char *)in);
+    }
     goto begin_key_exchange;
 
     crFinish(1);
@@ -4794,6 +5346,533 @@ static void ssh2_set_window(struct ssh_channel *c, unsigned newwin)
     }
 }
 
+static void ssh2_msg_channel_window_adjust(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (c && !c->closes)
+       c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
+}
+
+static void ssh2_msg_channel_data(Ssh ssh, struct Packet *pktin)
+{
+    char *data;
+    unsigned int length;
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+    if (pktin->type == SSH2_MSG_CHANNEL_EXTENDED_DATA &&
+       ssh_pkt_getuint32(pktin) != SSH2_EXTENDED_DATA_STDERR)
+       return;                        /* extended but not stderr */
+    ssh_pkt_getstring(pktin, &data, &length);
+    if (data) {
+       int bufsize = 0;
+       c->v.v2.locwindow -= length;
+       switch (c->type) {
+         case CHAN_MAINSESSION:
+           bufsize =
+               from_backend(ssh->frontend, pktin->type ==
+                            SSH2_MSG_CHANNEL_EXTENDED_DATA,
+                            data, length);
+           break;
+         case CHAN_X11:
+           bufsize = x11_send(c->u.x11.s, data, length);
+           break;
+         case CHAN_SOCKDATA:
+           bufsize = pfd_send(c->u.pfd.s, data, length);
+           break;
+         case CHAN_AGENT:
+           while (length > 0) {
+               if (c->u.a.lensofar < 4) {
+                   unsigned int l = min(4 - c->u.a.lensofar, length);
+                   memcpy(c->u.a.msglen + c->u.a.lensofar,
+                          data, l);
+                   data += l;
+                   length -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == 4) {
+                   c->u.a.totallen =
+                       4 + GET_32BIT(c->u.a.msglen);
+                   c->u.a.message = snewn(c->u.a.totallen,
+                                          unsigned char);
+                   memcpy(c->u.a.message, c->u.a.msglen, 4);
+               }
+               if (c->u.a.lensofar >= 4 && length > 0) {
+                   unsigned int l =
+                       min(c->u.a.totallen - c->u.a.lensofar,
+                           length);
+                   memcpy(c->u.a.message + c->u.a.lensofar,
+                          data, l);
+                   data += l;
+                   length -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == c->u.a.totallen) {
+                   void *reply;
+                   int replylen;
+                   if (agent_query(c->u.a.message,
+                                   c->u.a.totallen,
+                                   &reply, &replylen,
+                                   ssh_agentf_callback, c))
+                       ssh_agentf_callback(c, reply, replylen);
+                   sfree(c->u.a.message);
+                   c->u.a.lensofar = 0;
+               }
+           }
+           bufsize = 0;
+           break;
+       }
+       /*
+        * If we are not buffering too much data,
+        * enlarge the window again at the remote side.
+        */
+       if (bufsize < OUR_V2_WINSIZE)
+           ssh2_set_window(c, OUR_V2_WINSIZE - bufsize);
+    }
+}
+
+static void ssh2_msg_channel_eof(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+
+    if (c->type == CHAN_X11) {
+       /*
+        * Remote EOF on an X11 channel means we should
+        * wrap up and close the channel ourselves.
+        */
+       x11_close(c->u.x11.s);
+       sshfwd_close(c);
+    } else if (c->type == CHAN_AGENT) {
+       sshfwd_close(c);
+    } else if (c->type == CHAN_SOCKDATA) {
+       pfd_close(c->u.pfd.s);
+       sshfwd_close(c);
+    }
+}
+
+static void ssh2_msg_channel_close(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    struct Packet *pktout;
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c || ((int)c->remoteid) == -1) {
+       bombout(("Received CHANNEL_CLOSE for %s channel %d\n",
+                c ? "half-open" : "nonexistent", i));
+       return;
+    }
+    /* Do pre-close processing on the channel. */
+    switch (c->type) {
+      case CHAN_MAINSESSION:
+       ssh->mainchan = NULL;
+       update_specials_menu(ssh->frontend);
+       break;
+      case CHAN_X11:
+       if (c->u.x11.s != NULL)
+           x11_close(c->u.x11.s);
+       sshfwd_close(c);
+       break;
+      case CHAN_AGENT:
+       sshfwd_close(c);
+       break;
+      case CHAN_SOCKDATA:
+       if (c->u.pfd.s != NULL)
+           pfd_close(c->u.pfd.s);
+       sshfwd_close(c);
+       break;
+    }
+    if (c->closes == 0) {
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_send(ssh, pktout);
+    }
+    del234(ssh->channels, c);
+    bufchain_clear(&c->v.v2.outbuffer);
+    sfree(c);
+
+    /*
+     * See if that was the last channel left open.
+     * (This is only our termination condition if we're
+     * not running in -N mode.)
+     */
+    if (!ssh->cfg.ssh_no_shell && count234(ssh->channels) == 0) {
+       logevent("All channels closed. Disconnecting");
+#if 0
+       /*
+        * We used to send SSH_MSG_DISCONNECT here,
+        * because I'd believed that _every_ conforming
+        * SSH2 connection had to end with a disconnect
+        * being sent by at least one side; apparently
+        * I was wrong and it's perfectly OK to
+        * unceremoniously slam the connection shut
+        * when you're done, and indeed OpenSSH feels
+        * this is more polite than sending a
+        * DISCONNECT. So now we don't.
+        */
+       s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
+       ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
+       ssh2_pkt_addstring(s->pktout, "All open channels closed");
+       ssh2_pkt_addstring(s->pktout, "en");    /* language tag */
+       ssh2_pkt_send_noqueue(ssh, s->pktout);
+#endif
+       ssh_closing((Plug)ssh, NULL, 0, 0);
+    }
+}
+
+static void ssh2_msg_channel_open_confirmation(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    struct Packet *pktout;
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+    if (c->type != CHAN_SOCKDATA_DORMANT)
+       return;                        /* dunno why they're confirming this */
+    c->remoteid = ssh_pkt_getuint32(pktin);
+    c->type = CHAN_SOCKDATA;
+    c->v.v2.remwindow = ssh_pkt_getuint32(pktin);
+    c->v.v2.remmaxpkt = ssh_pkt_getuint32(pktin);
+    if (c->u.pfd.s)
+       pfd_confirm(c->u.pfd.s);
+    if (c->closes) {
+       /*
+        * We have a pending close on this channel,
+        * which we decided on before the server acked
+        * the channel open. So now we know the
+        * remoteid, we can close it again.
+        */
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
+static void ssh2_msg_channel_open_failure(Ssh ssh, struct Packet *pktin)
+{
+    static const char *const reasons[] = {
+       "<unknown reason code>",
+           "Administratively prohibited",
+           "Connect failed",
+           "Unknown channel type",
+           "Resource shortage",
+    };
+    unsigned i = ssh_pkt_getuint32(pktin);
+    unsigned reason_code;
+    char *reason_string;
+    int reason_length;
+    char *message;
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+    if (c->type != CHAN_SOCKDATA_DORMANT)
+       return;                        /* dunno why they're failing this */
+
+    reason_code = ssh_pkt_getuint32(pktin);
+    if (reason_code >= lenof(reasons))
+       reason_code = 0; /* ensure reasons[reason_code] in range */
+    ssh_pkt_getstring(pktin, &reason_string, &reason_length);
+    message = dupprintf("Forwarded connection refused by"
+                       " server: %s [%.*s]", reasons[reason_code],
+                       reason_length, reason_string);
+    logevent(message);
+    sfree(message);
+
+    pfd_close(c->u.pfd.s);
+
+    del234(ssh->channels, c);
+    sfree(c);
+}
+
+static void ssh2_msg_channel_request(Ssh ssh, struct Packet *pktin)
+{
+    unsigned localid;
+    char *type;
+    int typelen, want_reply;
+    int reply = SSH2_MSG_CHANNEL_FAILURE; /* default */
+    struct ssh_channel *c;
+    struct Packet *pktout;
+
+    localid = ssh_pkt_getuint32(pktin);
+    ssh_pkt_getstring(pktin, &type, &typelen);
+    want_reply = ssh2_pkt_getbool(pktin);
+
+    /*
+     * First, check that the channel exists. Otherwise,
+     * we can instantly disconnect with a rude message.
+     */
+    c = find234(ssh->channels, &localid, ssh_channelfind);
+    if (!c) {
+       char buf[80];
+       sprintf(buf, "Received channel request for nonexistent"
+               " channel %d", localid);
+       logevent(buf);
+       pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
+       ssh2_pkt_adduint32(pktout, SSH2_DISCONNECT_BY_APPLICATION);
+       ssh2_pkt_addstring(pktout, buf);
+       ssh2_pkt_addstring(pktout, "en");       /* language tag */
+       ssh2_pkt_send_noqueue(ssh, pktout);
+       connection_fatal(ssh->frontend, "%s", buf);
+       ssh_closing((Plug)ssh, NULL, 0, 0);
+       return;
+    }
+
+    /*
+     * Having got the channel number, we now look at
+     * the request type string to see if it's something
+     * we recognise.
+     */
+    if (c == ssh->mainchan) {
+       /*
+        * We recognise "exit-status" and "exit-signal" on
+        * the primary channel.
+        */
+       if (typelen == 11 &&
+           !memcmp(type, "exit-status", 11)) {
+
+           ssh->exitcode = ssh_pkt_getuint32(pktin);
+           logeventf(ssh, "Server sent command exit status %d",
+                     ssh->exitcode);
+           reply = SSH2_MSG_CHANNEL_SUCCESS;
+
+       } else if (typelen == 11 &&
+                  !memcmp(type, "exit-signal", 11)) {
+
+           int is_plausible = TRUE, is_int = FALSE;
+           char *fmt_sig = "", *fmt_msg = "";
+           char *msg;
+           int msglen = 0, core = FALSE;
+           /* ICK: older versions of OpenSSH (e.g. 3.4p1)
+            * provide an `int' for the signal, despite its
+            * having been a `string' in the drafts since at
+            * least 2001. (Fixed in session.c 1.147.) Try to
+            * infer which we can safely parse it as. */
+           {
+               unsigned char *p = pktin->body +
+                   pktin->savedpos;
+               long len = pktin->length - pktin->savedpos;
+               unsigned long num = GET_32BIT(p); /* what is it? */
+               /* If it's 0, it hardly matters; assume string */
+               if (num == 0) {
+                   is_int = FALSE;
+               } else {
+                   int maybe_int = FALSE, maybe_str = FALSE;
+#define CHECK_HYPOTHESIS(offset, result) \
+    do { \
+       long q = offset; \
+       if (q >= 0 && q+4 <= len) { \
+           q = q + 4 + GET_32BIT(p+q); \
+           if (q >= 0 && q+4 <= len && \
+                   (q = q + 4 + GET_32BIT(p+q)) && q == len) \
+               result = TRUE; \
+       } \
+    } while(0)
+                   CHECK_HYPOTHESIS(4+1, maybe_int);
+                   CHECK_HYPOTHESIS(4+num+1, maybe_str);
+#undef CHECK_HYPOTHESIS
+                   if (maybe_int && !maybe_str)
+                       is_int = TRUE;
+                   else if (!maybe_int && maybe_str)
+                       is_int = FALSE;
+                   else
+                       /* Crikey. Either or neither. Panic. */
+                       is_plausible = FALSE;
+               }
+           }
+           if (is_plausible) {
+               if (is_int) {
+                   /* Old non-standard OpenSSH. */
+                   int signum = ssh_pkt_getuint32(pktin);
+                   fmt_sig = dupprintf(" %d", signum);
+               } else {
+                   /* As per the drafts. */
+                   char *sig;
+                   int siglen;
+                   ssh_pkt_getstring(pktin, &sig, &siglen);
+                   /* Signal name isn't supposed to be blank, but
+                    * let's cope gracefully if it is. */
+                   if (siglen) {
+                       fmt_sig = dupprintf(" \"%.*s\"",
+                                           siglen, sig);
+                   }
+               }
+               core = ssh2_pkt_getbool(pktin);
+               ssh_pkt_getstring(pktin, &msg, &msglen);
+               if (msglen) {
+                   fmt_msg = dupprintf(" (\"%.*s\")", msglen, msg);
+               }
+               /* ignore lang tag */
+           } /* else don't attempt to parse */
+           logeventf(ssh, "Server exited on signal%s%s%s",
+                     fmt_sig, core ? " (core dumped)" : "",
+                     fmt_msg);
+           if (*fmt_sig) sfree(fmt_sig);
+           if (*fmt_msg) sfree(fmt_msg);
+           reply = SSH2_MSG_CHANNEL_SUCCESS;
+
+       }
+    } else {
+       /*
+        * This is a channel request we don't know
+        * about, so we now either ignore the request
+        * or respond with CHANNEL_FAILURE, depending
+        * on want_reply.
+        */
+       reply = SSH2_MSG_CHANNEL_FAILURE;
+    }
+    if (want_reply) {
+       pktout = ssh2_pkt_init(reply);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
+static void ssh2_msg_global_request(Ssh ssh, struct Packet *pktin)
+{
+    char *type;
+    int typelen, want_reply;
+    struct Packet *pktout;
+
+    ssh_pkt_getstring(pktin, &type, &typelen);
+    want_reply = ssh2_pkt_getbool(pktin);
+
+    /*
+     * We currently don't support any global requests
+     * at all, so we either ignore the request or
+     * respond with REQUEST_FAILURE, depending on
+     * want_reply.
+     */
+    if (want_reply) {
+       pktout = ssh2_pkt_init(SSH2_MSG_REQUEST_FAILURE);
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
+static void ssh2_msg_channel_open(Ssh ssh, struct Packet *pktin)
+{
+    char *type;
+    int typelen;
+    char *peeraddr;
+    int peeraddrlen;
+    int peerport;
+    char *error = NULL;
+    struct ssh_channel *c;
+    unsigned remid, winsize, pktsize;
+    struct Packet *pktout;
+
+    ssh_pkt_getstring(pktin, &type, &typelen);
+    c = snew(struct ssh_channel);
+    c->ssh = ssh;
+
+    remid = ssh_pkt_getuint32(pktin);
+    winsize = ssh_pkt_getuint32(pktin);
+    pktsize = ssh_pkt_getuint32(pktin);
+
+    if (typelen == 3 && !memcmp(type, "x11", 3)) {
+       char *addrstr;
+
+       ssh_pkt_getstring(pktin, &peeraddr, &peeraddrlen);
+       addrstr = snewn(peeraddrlen+1, char);
+       memcpy(addrstr, peeraddr, peeraddrlen);
+       addrstr[peeraddrlen] = '\0';
+       peerport = ssh_pkt_getuint32(pktin);
+
+       logeventf(ssh, "Received X11 connect request from %s:%d",
+                 addrstr, peerport);
+
+       if (!ssh->X11_fwd_enabled)
+           error = "X11 forwarding is not enabled";
+       else if (x11_init(&c->u.x11.s, ssh->cfg.x11_display, c,
+                         ssh->x11auth, addrstr, peerport,
+                         &ssh->cfg) != NULL) {
+           error = "Unable to open an X11 connection";
+       } else {
+           logevent("Opening X11 forward connection succeeded");
+           c->type = CHAN_X11;
+       }
+
+       sfree(addrstr);
+    } else if (typelen == 15 &&
+              !memcmp(type, "forwarded-tcpip", 15)) {
+       struct ssh_rportfwd pf, *realpf;
+       char *dummy;
+       int dummylen;
+       ssh_pkt_getstring(pktin, &dummy, &dummylen);/* skip address */
+       pf.sport = ssh_pkt_getuint32(pktin);
+       ssh_pkt_getstring(pktin, &peeraddr, &peeraddrlen);
+       peerport = ssh_pkt_getuint32(pktin);
+       realpf = find234(ssh->rportfwds, &pf, NULL);
+       logeventf(ssh, "Received remote port %d open request "
+                 "from %s:%d", pf.sport, peeraddr, peerport);
+       if (realpf == NULL) {
+           error = "Remote port is not recognised";
+       } else {
+           const char *e = pfd_newconnect(&c->u.pfd.s,
+                                          realpf->dhost,
+                                          realpf->dport, c,
+                                          &ssh->cfg,
+                                          realpf->pfrec->addressfamily);
+           logeventf(ssh, "Attempting to forward remote port to "
+                     "%s:%d", realpf->dhost, realpf->dport);
+           if (e != NULL) {
+               logeventf(ssh, "Port open failed: %s", e);
+               error = "Port open failed";
+           } else {
+               logevent("Forwarded port opened successfully");
+               c->type = CHAN_SOCKDATA;
+           }
+       }
+    } else if (typelen == 22 &&
+              !memcmp(type, "auth-agent@openssh.com", 3)) {
+       if (!ssh->agentfwd_enabled)
+           error = "Agent forwarding is not enabled";
+       else {
+           c->type = CHAN_AGENT;       /* identify channel type */
+           c->u.a.lensofar = 0;
+       }
+    } else {
+       error = "Unsupported channel type requested";
+    }
+
+    c->remoteid = remid;
+    if (error) {
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_FAILURE);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_adduint32(pktout, SSH2_OPEN_CONNECT_FAILED);
+       ssh2_pkt_addstring(pktout, error);
+       ssh2_pkt_addstring(pktout, "en");       /* language tag */
+       ssh2_pkt_send(ssh, pktout);
+       logeventf(ssh, "Rejected channel open: %s", error);
+       sfree(c);
+    } else {
+       c->localid = alloc_channel_id(ssh);
+       c->closes = 0;
+       c->v.v2.locwindow = OUR_V2_WINSIZE;
+       c->v.v2.remwindow = winsize;
+       c->v.v2.remmaxpkt = pktsize;
+       bufchain_init(&c->v.v2.outbuffer);
+       add234(ssh->channels, c);
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_adduint32(pktout, c->localid);
+       ssh2_pkt_adduint32(pktout, c->v.v2.locwindow);
+       ssh2_pkt_adduint32(pktout, 0x4000UL);   /* our max pkt size */
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
 /*
  * Handle the SSH2 userauth and connection layers.
  */
@@ -5452,7 +6531,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
                        ssh2_pkt_addstring(s->pktout, "No more passwords available"
                                           " to try");
                        ssh2_pkt_addstring(s->pktout, "en");    /* language tag */
-                       ssh2_pkt_send(ssh, s->pktout);
+                       ssh2_pkt_send_noqueue(ssh, s->pktout);
                        logevent("Unable to authenticate");
                        connection_fatal(ssh->frontend,
                                         "Unable to authenticate");
@@ -5653,7 +6732,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
                ssh2_pkt_addstring(s->pktout, "No supported authentication"
                                   " methods available");
                ssh2_pkt_addstring(s->pktout, "en");    /* language tag */
-               ssh2_pkt_send(ssh, s->pktout);
+               ssh2_pkt_send_noqueue(ssh, s->pktout);
                 ssh_closing((Plug)ssh, NULL, 0, 0);
                crStopV;
            }
@@ -5669,6 +6748,15 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
     ssh->channels = newtree234(ssh_channelcmp);
 
     /*
+     * Set up handlers for some connection protocol messages, so we
+     * don't have to handle them repeatedly in this coroutine.
+     */
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_WINDOW_ADJUST] =
+       ssh2_msg_channel_window_adjust;
+    ssh->packet_dispatch[SSH2_MSG_GLOBAL_REQUEST] =
+       ssh2_msg_global_request;
+
+    /*
      * Create the main session channel.
      */
     if (!ssh->cfg.ssh_no_shell) {
@@ -5705,6 +6793,24 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
        ssh->mainchan = NULL;
 
     /*
+     * Now we have a channel, make dispatch table entries for
+     * general channel-based messages.
+     */
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_DATA] =
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_EXTENDED_DATA] =
+       ssh2_msg_channel_data;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_EOF] = ssh2_msg_channel_eof;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_CLOSE] = ssh2_msg_channel_close;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN_CONFIRMATION] =
+       ssh2_msg_channel_open_confirmation;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN_FAILURE] =
+       ssh2_msg_channel_open_failure;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_REQUEST] =
+       ssh2_msg_channel_request;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN] =
+       ssh2_msg_channel_open;
+
+    /*
      * Potentially enable X11 forwarding.
      */
     if (ssh->mainchan && ssh->cfg.x11_forward) {
@@ -5723,17 +6829,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
        ssh2_pkt_adduint32(s->pktout, x11_get_screen_number(ssh->cfg.x11_display));
        ssh2_pkt_send(ssh, s->pktout);
 
-       do {
-           crWaitUntilV(pktin);
-           if (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
-           }
-       } while (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+       crWaitUntilV(pktin);
 
        if (pktin->type != SSH2_MSG_CHANNEL_SUCCESS) {
            if (pktin->type != SSH2_MSG_CHANNEL_FAILURE) {
@@ -5751,173 +6847,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
     /*
      * Enable port forwardings.
      */
-    {
-       char type;
-       int n;
-       int sport,dport,sserv,dserv;
-       char sports[256], dports[256], saddr[256], host[256];
-
-       ssh->rportfwds = newtree234(ssh_rportcmp_ssh2);
-        /* Add port forwardings. */
-       ssh->portfwd_strptr = ssh->cfg.portfwd;
-       while (*ssh->portfwd_strptr) {
-           type = *ssh->portfwd_strptr++;
-           saddr[0] = '\0';
-           n = 0;
-           while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != '\t') {
-               if (*ssh->portfwd_strptr == ':') {
-                   /*
-                    * We've seen a colon in the middle of the
-                    * source port number. This means that
-                    * everything we've seen until now is the
-                    * source _address_, so we'll move it into
-                    * saddr and start sports from the beginning
-                    * again.
-                    */
-                   ssh->portfwd_strptr++;
-                   sports[n] = '\0';
-                   strcpy(saddr, sports);
-                   n = 0;
-               }
-               if (n < 255) sports[n++] = *ssh->portfwd_strptr++;
-           }
-           sports[n] = 0;
-           if (type != 'D') {
-               if (*ssh->portfwd_strptr == '\t')
-                   ssh->portfwd_strptr++;
-               n = 0;
-               while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != ':') {
-                   if (n < 255) host[n++] = *ssh->portfwd_strptr++;
-               }
-               host[n] = 0;
-               if (*ssh->portfwd_strptr == ':')
-                   ssh->portfwd_strptr++;
-               n = 0;
-               while (*ssh->portfwd_strptr) {
-                   if (n < 255) dports[n++] = *ssh->portfwd_strptr++;
-               }
-               dports[n] = 0;
-               ssh->portfwd_strptr++;
-               dport = atoi(dports);
-               dserv = 0;
-               if (dport == 0) {
-                   dserv = 1;
-                   dport = net_service_lookup(dports);
-                   if (!dport) {
-                       logeventf(ssh, "Service lookup failed for destination"
-                                 " port \"%s\"", dports);
-                   }
-               }
-           } else {
-               while (*ssh->portfwd_strptr) ssh->portfwd_strptr++;
-               dport = dserv = -1;
-               ssh->portfwd_strptr++; /* eat the NUL and move to next one */
-           }
-           sport = atoi(sports);
-           sserv = 0;
-           if (sport == 0) {
-               sserv = 1;
-               sport = net_service_lookup(sports);
-               if (!sport) {
-                   logeventf(ssh, "Service lookup failed for source"
-                             " port \"%s\"", sports);
-               }
-           }
-           if (sport && dport) {
-               /* Set up a description of the source port. */
-               static char *sportdesc;
-               sportdesc = dupprintf("%.*s%.*s%.*s%.*s%d%.*s",
-                       (int)(*saddr?strlen(saddr):0), *saddr?saddr:NULL,
-                       (int)(*saddr?1:0), ":",
-                       (int)(sserv ? strlen(sports) : 0), sports,
-                       sserv, "(", sport, sserv, ")");
-               if (type == 'L') {
-                   /* Verbose description of the destination port */
-                   char *dportdesc = dupprintf("%s:%.*s%.*s%d%.*s",
-                           host,
-                           (int)(dserv ? strlen(dports) : 0), dports,
-                           dserv, "(", dport, dserv, ")");
-                   const char *err = pfd_addforward(host, dport,
-                                                    *saddr ? saddr : NULL,
-                                                    sport, ssh, &ssh->cfg);
-                   if (err) {
-                       logeventf(ssh, "Local port %s forward to %s"
-                                 " failed: %s", sportdesc, dportdesc, err);
-                   } else {
-                       logeventf(ssh, "Local port %s forwarding to %s",
-                                 sportdesc, dportdesc);
-                   }
-                   sfree(dportdesc);
-               } else if (type == 'D') {
-                   const char *err = pfd_addforward(NULL, -1,
-                                                    *saddr ? saddr : NULL,
-                                                    sport, ssh, &ssh->cfg);
-                   if (err) {
-                       logeventf(ssh, "Local port %s SOCKS dynamic forward"
-                                 " setup failed: %s", sportdesc, err);
-                   } else {
-                       logeventf(ssh, "Local port %s doing SOCKS"
-                                 " dynamic forwarding", sportdesc);
-                   }
-               } else {
-                   struct ssh_rportfwd *pf;
-                   pf = snew(struct ssh_rportfwd);
-                   strcpy(pf->dhost, host);
-                   pf->dport = dport;
-                   pf->sport = sport;
-                   if (add234(ssh->rportfwds, pf) != pf) {
-                       logeventf(ssh, "Duplicate remote port forwarding"
-                                 " to %s:%d", host, dport);
-                       sfree(pf);
-                   } else {
-                       logeventf(ssh, "Requesting remote port %s"
-                                 " forward to %s:%.*s%.*s%d%.*s",
-                                 sportdesc,
-                                 host,
-                                 (int)(dserv ? strlen(dports) : 0), dports,
-                                 dserv, "(", dport, dserv, ")");
-                       s->pktout = ssh2_pkt_init(SSH2_MSG_GLOBAL_REQUEST);
-                       ssh2_pkt_addstring(s->pktout, "tcpip-forward");
-                       ssh2_pkt_addbool(s->pktout, 1);/* want reply */
-                       if (*saddr) {
-                           ssh2_pkt_addstring(s->pktout, saddr);
-                       } else if (ssh->cfg.rport_acceptall) {
-                           ssh2_pkt_addstring(s->pktout, "0.0.0.0");
-                       } else {
-                           ssh2_pkt_addstring(s->pktout, "127.0.0.1");
-                       }
-                       ssh2_pkt_adduint32(s->pktout, sport);
-                       ssh2_pkt_send(ssh, s->pktout);
-
-                       do {
-                           crWaitUntilV(pktin);
-                           if (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-                               unsigned i = ssh_pkt_getuint32(pktin);
-                               struct ssh_channel *c;
-                               c = find234(ssh->channels, &i, ssh_channelfind);
-                               if (!c)
-                                   continue;/* nonexistent channel */
-                               c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
-                           }
-                       } while (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
-
-                       if (pktin->type != SSH2_MSG_REQUEST_SUCCESS) {
-                           if (pktin->type != SSH2_MSG_REQUEST_FAILURE) {
-                               bombout(("Unexpected response to port "
-                                        "forwarding request: packet type %d",
-                                        pktin->type));
-                               crStopV;
-                           }
-                           logevent("Server refused this port forwarding");
-                       } else {
-                           logevent("Remote port forwarding enabled");
-                       }
-                   }
-               }
-               sfree(sportdesc);
-           }
-       }
-    }
+    ssh_setup_portfwd(ssh, &ssh->cfg);
 
     /*
      * Potentially enable agent forwarding.
@@ -5930,17 +6860,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
        ssh2_pkt_addbool(s->pktout, 1);        /* want reply */
        ssh2_pkt_send(ssh, s->pktout);
 
-       do {
-           crWaitUntilV(pktin);
-           if (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
-           }
-       } while (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+       crWaitUntilV(pktin);
 
        if (pktin->type != SSH2_MSG_CHANNEL_SUCCESS) {
            if (pktin->type != SSH2_MSG_CHANNEL_FAILURE) {
@@ -5982,17 +6902,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
        ssh2_pkt_send(ssh, s->pktout);
        ssh->state = SSH_STATE_INTERMED;
 
-       do {
-           crWaitUntilV(pktin);
-           if (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
-           }
-       } while (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+       crWaitUntilV(pktin);
 
        if (pktin->type != SSH2_MSG_CHANNEL_SUCCESS) {
            if (pktin->type != SSH2_MSG_CHANNEL_FAILURE) {
@@ -6049,17 +6959,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
        s->env_left = s->num_env;
 
        while (s->env_left > 0) {
-           do {
-               crWaitUntilV(pktin);
-               if (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-                   unsigned i = ssh_pkt_getuint32(pktin);
-                   struct ssh_channel *c;
-                   c = find234(ssh->channels, &i, ssh_channelfind);
-                   if (!c)
-                       continue;              /* nonexistent channel */
-                   c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
-               }
-           } while (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+           crWaitUntilV(pktin);
 
            if (pktin->type != SSH2_MSG_CHANNEL_SUCCESS) {
                if (pktin->type != SSH2_MSG_CHANNEL_FAILURE) {
@@ -6118,17 +7018,9 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
            ssh2_pkt_addbool(s->pktout, 1);            /* want reply */
        }
        ssh2_pkt_send(ssh, s->pktout);
-       do {
-           crWaitUntilV(pktin);
-           if (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
-           }
-       } while (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+
+       crWaitUntilV(pktin);
+
        if (pktin->type != SSH2_MSG_CHANNEL_SUCCESS) {
            if (pktin->type != SSH2_MSG_CHANNEL_FAILURE) {
                bombout(("Unexpected response to shell/command request:"
@@ -6171,507 +7063,15 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
        crReturnV;
        s->try_send = FALSE;
        if (pktin) {
-           if (pktin->type == SSH2_MSG_CHANNEL_DATA ||
-               pktin->type == SSH2_MSG_CHANNEL_EXTENDED_DATA) {
-               char *data;
-               int length;
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               if (pktin->type == SSH2_MSG_CHANNEL_EXTENDED_DATA &&
-                   ssh_pkt_getuint32(pktin) != SSH2_EXTENDED_DATA_STDERR)
-                   continue;          /* extended but not stderr */
-               ssh_pkt_getstring(pktin, &data, &length);
-               if (data) {
-                   int bufsize = 0;
-                   c->v.v2.locwindow -= length;
-                   switch (c->type) {
-                     case CHAN_MAINSESSION:
-                       bufsize =
-                           from_backend(ssh->frontend, pktin->type ==
-                                        SSH2_MSG_CHANNEL_EXTENDED_DATA,
-                                        data, length);
-                       break;
-                     case CHAN_X11:
-                       bufsize = x11_send(c->u.x11.s, data, length);
-                       break;
-                     case CHAN_SOCKDATA:
-                       bufsize = pfd_send(c->u.pfd.s, data, length);
-                       break;
-                     case CHAN_AGENT:
-                       while (length > 0) {
-                           if (c->u.a.lensofar < 4) {
-                               int l = min(4 - c->u.a.lensofar, length);
-                               memcpy(c->u.a.msglen + c->u.a.lensofar,
-                                      data, l);
-                               data += l;
-                               length -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == 4) {
-                               c->u.a.totallen =
-                                   4 + GET_32BIT(c->u.a.msglen);
-                               c->u.a.message = snewn(c->u.a.totallen,
-                                                      unsigned char);
-                               memcpy(c->u.a.message, c->u.a.msglen, 4);
-                           }
-                           if (c->u.a.lensofar >= 4 && length > 0) {
-                               int l =
-                                   min(c->u.a.totallen - c->u.a.lensofar,
-                                       length);
-                               memcpy(c->u.a.message + c->u.a.lensofar,
-                                      data, l);
-                               data += l;
-                               length -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == c->u.a.totallen) {
-                               void *reply;
-                               int replylen;
-                               if (agent_query(c->u.a.message,
-                                               c->u.a.totallen,
-                                               &reply, &replylen,
-                                               ssh_agentf_callback, c))
-                                   ssh_agentf_callback(c, reply, replylen);
-                               sfree(c->u.a.message);
-                               c->u.a.lensofar = 0;
-                           }
-                       }
-                       bufsize = 0;
-                       break;
-                   }
-                   /*
-                    * If we are not buffering too much data,
-                    * enlarge the window again at the remote side.
-                    */
-                   if (bufsize < OUR_V2_WINSIZE)
-                       ssh2_set_window(c, OUR_V2_WINSIZE - bufsize);
-               }
-           } else if (pktin->type == SSH2_MSG_CHANNEL_EOF) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-
-               if (c->type == CHAN_X11) {
-                   /*
-                    * Remote EOF on an X11 channel means we should
-                    * wrap up and close the channel ourselves.
-                    */
-                   x11_close(c->u.x11.s);
-                   sshfwd_close(c);
-               } else if (c->type == CHAN_AGENT) {
-                   sshfwd_close(c);
-               } else if (c->type == CHAN_SOCKDATA) {
-                   pfd_close(c->u.pfd.s);
-                   sshfwd_close(c);
-               }
-           } else if (pktin->type == SSH2_MSG_CHANNEL_CLOSE) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c || ((int)c->remoteid) == -1) {
-                   bombout(("Received CHANNEL_CLOSE for %s channel %d\n",
-                            c ? "half-open" : "nonexistent", i));
-                   crStopV;
-               }
-               /* Do pre-close processing on the channel. */
-               switch (c->type) {
-                 case CHAN_MAINSESSION:
-                   ssh->mainchan = NULL;
-                   update_specials_menu(ssh->frontend);
-                   break;
-                 case CHAN_X11:
-                   if (c->u.x11.s != NULL)
-                       x11_close(c->u.x11.s);
-                   sshfwd_close(c);
-                   break;
-                 case CHAN_AGENT:
-                   sshfwd_close(c);
-                   break;
-                 case CHAN_SOCKDATA:
-                   if (c->u.pfd.s != NULL)
-                       pfd_close(c->u.pfd.s);
-                   sshfwd_close(c);
-                   break;
-               }
-               if (c->closes == 0) {
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
-                   ssh2_pkt_adduint32(s->pktout, c->remoteid);
-                   ssh2_pkt_send(ssh, s->pktout);
-               }
-               del234(ssh->channels, c);
-               bufchain_clear(&c->v.v2.outbuffer);
-               sfree(c);
-
-               /*
-                * See if that was the last channel left open.
-                * (This is only our termination condition if we're
-                * not running in -N mode.)
-                */
-               if (!ssh->cfg.ssh_no_shell && count234(ssh->channels) == 0) {
-                   logevent("All channels closed. Disconnecting");
-#if 0
-                    /*
-                     * We used to send SSH_MSG_DISCONNECT here,
-                     * because I'd believed that _every_ conforming
-                     * SSH2 connection had to end with a disconnect
-                     * being sent by at least one side; apparently
-                     * I was wrong and it's perfectly OK to
-                     * unceremoniously slam the connection shut
-                     * when you're done, and indeed OpenSSH feels
-                     * this is more polite than sending a
-                     * DISCONNECT. So now we don't.
-                     */
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-                   ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
-                   ssh2_pkt_addstring(s->pktout, "All open channels closed");
-                   ssh2_pkt_addstring(s->pktout, "en");        /* language tag */
-                   ssh2_pkt_send(ssh, s->pktout);
-#endif
-                    ssh_closing((Plug)ssh, NULL, 0, 0);
-                   crStopV;
-               }
-               continue;              /* remote sends close; ignore (FIXME) */
-           } else if (pktin->type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c || c->closes)
-                   continue;          /* nonexistent or closing channel */
-               c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
-               s->try_send = TRUE;
-           } else if (pktin->type == SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               if (c->type != CHAN_SOCKDATA_DORMANT)
-                   continue;          /* dunno why they're confirming this */
-               c->remoteid = ssh_pkt_getuint32(pktin);
-               c->type = CHAN_SOCKDATA;
-               c->v.v2.remwindow = ssh_pkt_getuint32(pktin);
-               c->v.v2.remmaxpkt = ssh_pkt_getuint32(pktin);
-               if (c->u.pfd.s)
-                   pfd_confirm(c->u.pfd.s);
-               if (c->closes) {
-                   /*
-                    * We have a pending close on this channel,
-                    * which we decided on before the server acked
-                    * the channel open. So now we know the
-                    * remoteid, we can close it again.
-                    */
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
-                   ssh2_pkt_adduint32(s->pktout, c->remoteid);
-                   ssh2_pkt_send(ssh, s->pktout);
-               }
-           } else if (pktin->type == SSH2_MSG_CHANNEL_OPEN_FAILURE) {
-                static const char *const reasons[] = {
-                    "<unknown reason code>",
-                    "Administratively prohibited",
-                    "Connect failed",
-                    "Unknown channel type",
-                    "Resource shortage",
-                };
-               unsigned i = ssh_pkt_getuint32(pktin);
-                unsigned reason_code;
-                char *reason_string;
-                int reason_length;
-                char *message;
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               if (c->type != CHAN_SOCKDATA_DORMANT)
-                   continue;          /* dunno why they're failing this */
-
-                reason_code = ssh_pkt_getuint32(pktin);
-                if (reason_code >= lenof(reasons))
-                    reason_code = 0; /* ensure reasons[reason_code] in range */
-                ssh_pkt_getstring(pktin, &reason_string, &reason_length);
-                message = dupprintf("Forwarded connection refused by"
-                                    " server: %s [%.*s]", reasons[reason_code],
-                                    reason_length, reason_string);
-               logevent(message);
-                sfree(message);
-
-               pfd_close(c->u.pfd.s);
-
-               del234(ssh->channels, c);
-               sfree(c);
-           } else if (pktin->type == SSH2_MSG_CHANNEL_REQUEST) {
-               unsigned localid;
-               char *type;
-               int typelen, want_reply;
-               int reply = SSH2_MSG_CHANNEL_FAILURE; /* default */
-               struct ssh_channel *c;
-
-               localid = ssh_pkt_getuint32(pktin);
-               ssh_pkt_getstring(pktin, &type, &typelen);
-               want_reply = ssh2_pkt_getbool(pktin);
-
-               /*
-                * First, check that the channel exists. Otherwise,
-                * we can instantly disconnect with a rude message.
-                */
-               c = find234(ssh->channels, &localid, ssh_channelfind);
-               if (!c) {
-                   char buf[80];
-                   sprintf(buf, "Received channel request for nonexistent"
-                           " channel %d", localid);
-                   logevent(buf);
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-                   ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
-                   ssh2_pkt_addstring(s->pktout, buf);
-                   ssh2_pkt_addstring(s->pktout, "en");        /* language tag */
-                   ssh2_pkt_send(ssh, s->pktout);
-                   connection_fatal(ssh->frontend, "%s", buf);
-                    ssh_closing((Plug)ssh, NULL, 0, 0);
-                   crStopV;
-               }
-
-               /*
-                * Having got the channel number, we now look at
-                * the request type string to see if it's something
-                * we recognise.
-                */
-               if (c == ssh->mainchan) {
-                   /*
-                    * We recognise "exit-status" and "exit-signal" on
-                    * the primary channel.
-                    */
-                   if (typelen == 11 &&
-                       !memcmp(type, "exit-status", 11)) {
-
-                       ssh->exitcode = ssh_pkt_getuint32(pktin);
-                       logeventf(ssh, "Server sent command exit status %d",
-                                 ssh->exitcode);
-                       reply = SSH2_MSG_CHANNEL_SUCCESS;
-
-                   } else if (typelen == 11 &&
-                              !memcmp(type, "exit-signal", 11)) {
-
-                       int is_plausible = TRUE, is_int = FALSE;
-                       char *fmt_sig = "", *fmt_msg = "";
-                       char *msg;
-                       int msglen = 0, core = FALSE;
-                       /* ICK: older versions of OpenSSH (e.g. 3.4p1)
-                        * provide an `int' for the signal, despite its
-                        * having been a `string' in the drafts since at
-                        * least 2001. (Fixed in session.c 1.147.) Try to
-                        * infer which we can safely parse it as. */
-                       {
-                           unsigned char *p = pktin->body +
-                                              pktin->savedpos;
-                           long len = pktin->length - pktin->savedpos;
-                           unsigned long num = GET_32BIT(p); /* what is it? */
-                           /* If it's 0, it hardly matters; assume string */
-                           if (num == 0) {
-                               is_int = FALSE;
-                           } else {
-                               int maybe_int = FALSE, maybe_str = FALSE;
-#define CHECK_HYPOTHESIS(offset, result) \
-    do { \
-       long q = offset; \
-       if (q >= 0 && q+4 <= len) { \
-           q = q + 4 + GET_32BIT(p+q); \
-           if (q >= 0 && q+4 <= len && \
-                   (q = q + 4 + GET_32BIT(p+q)) && q == len) \
-               result = TRUE; \
-       } \
-    } while(0)
-                               CHECK_HYPOTHESIS(4+1, maybe_int);
-                               CHECK_HYPOTHESIS(4+num+1, maybe_str);
-#undef CHECK_HYPOTHESIS
-                               if (maybe_int && !maybe_str)
-                                   is_int = TRUE;
-                               else if (!maybe_int && maybe_str)
-                                   is_int = FALSE;
-                               else
-                                   /* Crikey. Either or neither. Panic. */
-                                   is_plausible = FALSE;
-                           }
-                       }
-                       if (is_plausible) {
-                           if (is_int) {
-                               /* Old non-standard OpenSSH. */
-                               int signum = ssh_pkt_getuint32(pktin);
-                               fmt_sig = dupprintf(" %d", signum);
-                           } else {
-                               /* As per the drafts. */
-                               char *sig;
-                               int siglen;
-                               ssh_pkt_getstring(pktin, &sig, &siglen);
-                               /* Signal name isn't supposed to be blank, but
-                                * let's cope gracefully if it is. */
-                               if (siglen) {
-                                   fmt_sig = dupprintf(" \"%.*s\"",
-                                                       siglen, sig);
-                               }
-                           }
-                           core = ssh2_pkt_getbool(pktin);
-                           ssh_pkt_getstring(pktin, &msg, &msglen);
-                           if (msglen) {
-                               fmt_msg = dupprintf(" (\"%.*s\")", msglen, msg);
-                           }
-                           /* ignore lang tag */
-                       } /* else don't attempt to parse */
-                       logeventf(ssh, "Server exited on signal%s%s%s",
-                                 fmt_sig, core ? " (core dumped)" : "",
-                                 fmt_msg);
-                       if (*fmt_sig) sfree(fmt_sig);
-                       if (*fmt_msg) sfree(fmt_msg);
-                       reply = SSH2_MSG_CHANNEL_SUCCESS;
-
-                   }
-               } else {
-                   /*
-                    * This is a channel request we don't know
-                    * about, so we now either ignore the request
-                    * or respond with CHANNEL_FAILURE, depending
-                    * on want_reply.
-                    */
-                   reply = SSH2_MSG_CHANNEL_FAILURE;
-               }
-               if (want_reply) {
-                   s->pktout = ssh2_pkt_init(reply);
-                   ssh2_pkt_adduint32(s->pktout, c->remoteid);
-                   ssh2_pkt_send(ssh, s->pktout);
-               }
-           } else if (pktin->type == SSH2_MSG_GLOBAL_REQUEST) {
-               char *type;
-               int typelen, want_reply;
-
-               ssh_pkt_getstring(pktin, &type, &typelen);
-               want_reply = ssh2_pkt_getbool(pktin);
-
-                /*
-                 * We currently don't support any global requests
-                 * at all, so we either ignore the request or
-                 * respond with REQUEST_FAILURE, depending on
-                 * want_reply.
-                 */
-                if (want_reply) {
-                    s->pktout = ssh2_pkt_init(SSH2_MSG_REQUEST_FAILURE);
-                    ssh2_pkt_send(ssh, s->pktout);
-               }
-           } else if (pktin->type == SSH2_MSG_CHANNEL_OPEN) {
-               char *type;
-               int typelen;
-               char *peeraddr;
-               int peeraddrlen;
-               int peerport;
-               char *error = NULL;
-               struct ssh_channel *c;
-               unsigned remid, winsize, pktsize;
-               ssh_pkt_getstring(pktin, &type, &typelen);
-               c = snew(struct ssh_channel);
-               c->ssh = ssh;
-
-               remid = ssh_pkt_getuint32(pktin);
-               winsize = ssh_pkt_getuint32(pktin);
-               pktsize = ssh_pkt_getuint32(pktin);
-
-               if (typelen == 3 && !memcmp(type, "x11", 3)) {
-                   char *addrstr;
-
-                    ssh_pkt_getstring(pktin, &peeraddr, &peeraddrlen);
-                   addrstr = snewn(peeraddrlen+1, char);
-                   memcpy(addrstr, peeraddr, peeraddrlen);
-                   addrstr[peeraddrlen] = '\0';
-                    peerport = ssh_pkt_getuint32(pktin);
-
-                   logeventf(ssh, "Received X11 connect request from %s:%d",
-                             addrstr, peerport);
-
-                   if (!ssh->X11_fwd_enabled)
-                       error = "X11 forwarding is not enabled";
-                   else if (x11_init(&c->u.x11.s, ssh->cfg.x11_display, c,
-                                     ssh->x11auth, addrstr, peerport,
-                                     &ssh->cfg) != NULL) {
-                       error = "Unable to open an X11 connection";
-                   } else {
-                       logevent("Opening X11 forward connection succeeded");
-                       c->type = CHAN_X11;
-                   }
 
-                   sfree(addrstr);
-               } else if (typelen == 15 &&
-                          !memcmp(type, "forwarded-tcpip", 15)) {
-                   struct ssh_rportfwd pf, *realpf;
-                   char *dummy;
-                   int dummylen;
-                   ssh_pkt_getstring(pktin, &dummy, &dummylen);/* skip address */
-                   pf.sport = ssh_pkt_getuint32(pktin);
-                    ssh_pkt_getstring(pktin, &peeraddr, &peeraddrlen);
-                    peerport = ssh_pkt_getuint32(pktin);
-                   realpf = find234(ssh->rportfwds, &pf, NULL);
-                   logeventf(ssh, "Received remote port %d open request "
-                             "from %s:%d", pf.sport, peeraddr, peerport);
-                   if (realpf == NULL) {
-                       error = "Remote port is not recognised";
-                   } else {
-                       const char *e = pfd_newconnect(&c->u.pfd.s,
-                                                      realpf->dhost,
-                                                      realpf->dport, c,
-                                                      &ssh->cfg);
-                       logeventf(ssh, "Attempting to forward remote port to "
-                                 "%s:%d", realpf->dhost, realpf->dport);
-                       if (e != NULL) {
-                           logeventf(ssh, "Port open failed: %s", e);
-                           error = "Port open failed";
-                       } else {
-                           logevent("Forwarded port opened successfully");
-                           c->type = CHAN_SOCKDATA;
-                       }
-                   }
-               } else if (typelen == 22 &&
-                          !memcmp(type, "auth-agent@openssh.com", 3)) {
-                   if (!ssh->agentfwd_enabled)
-                       error = "Agent forwarding is not enabled";
-                   else {
-                       c->type = CHAN_AGENT;   /* identify channel type */
-                       c->u.a.lensofar = 0;
-                   }
-               } else {
-                   error = "Unsupported channel type requested";
-               }
+           /*
+            * _All_ the connection-layer packets we expect to
+            * receive are now handled by the dispatch table.
+            * Anything that reaches here must be bogus.
+            */
 
-               c->remoteid = remid;
-               if (error) {
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_FAILURE);
-                   ssh2_pkt_adduint32(s->pktout, c->remoteid);
-                   ssh2_pkt_adduint32(s->pktout, SSH2_OPEN_CONNECT_FAILED);
-                   ssh2_pkt_addstring(s->pktout, error);
-                   ssh2_pkt_addstring(s->pktout, "en");        /* language tag */
-                   ssh2_pkt_send(ssh, s->pktout);
-                   logeventf(ssh, "Rejected channel open: %s", error);
-                   sfree(c);
-               } else {
-                   c->localid = alloc_channel_id(ssh);
-                   c->closes = 0;
-                   c->v.v2.locwindow = OUR_V2_WINSIZE;
-                   c->v.v2.remwindow = winsize;
-                   c->v.v2.remmaxpkt = pktsize;
-                   bufchain_init(&c->v.v2.outbuffer);
-                   add234(ssh->channels, c);
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
-                   ssh2_pkt_adduint32(s->pktout, c->remoteid);
-                   ssh2_pkt_adduint32(s->pktout, c->localid);
-                   ssh2_pkt_adduint32(s->pktout, c->v.v2.locwindow);
-                   ssh2_pkt_adduint32(s->pktout, 0x4000UL);    /* our max pkt size */
-                   ssh2_pkt_send(ssh, s->pktout);
-               }
-           } else {
-               bombout(("Strange packet received: type %d", pktin->type));
-               crStopV;
-           }
+           bombout(("Strange packet received: type %d", pktin->type));
+           crStopV;
        } else if (ssh->mainchan) {
            /*
             * We have spare data. Add it to the channel buffer.
@@ -6716,14 +7116,168 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 }
 
 /*
+ * Handlers for SSH2 messages that might arrive at any moment.
+ */
+void ssh2_msg_disconnect(Ssh ssh, struct Packet *pktin)
+{
+    /* log reason code in disconnect message */
+    char *buf, *msg;
+    int nowlen, reason, msglen;
+
+    reason = ssh_pkt_getuint32(pktin);
+    ssh_pkt_getstring(pktin, &msg, &msglen);
+
+    if (reason > 0 && reason < lenof(ssh2_disconnect_reasons)) {
+       buf = dupprintf("Received disconnect message (%s)",
+                       ssh2_disconnect_reasons[reason]);
+    } else {
+       buf = dupprintf("Received disconnect message (unknown"
+                       " type %d)", reason);
+    }
+    logevent(buf);
+    sfree(buf);
+    buf = dupprintf("Disconnection message text: %n%.*s",
+                   &nowlen, msglen, msg);
+    logevent(buf);
+    bombout(("Server sent disconnect message\ntype %d (%s):\n\"%s\"",
+            reason,
+            (reason > 0 && reason < lenof(ssh2_disconnect_reasons)) ?
+            ssh2_disconnect_reasons[reason] : "unknown",
+            buf+nowlen));
+    sfree(buf);
+}
+
+void ssh2_msg_debug(Ssh ssh, struct Packet *pktin)
+{
+    /* log the debug message */
+    char *buf, *msg;
+    int msglen;
+    int always_display;
+
+    /* XXX maybe we should actually take notice of this */
+    always_display = ssh2_pkt_getbool(pktin);
+    ssh_pkt_getstring(pktin, &msg, &msglen);
+
+    buf = dupprintf("Remote debug message: %.*s", msglen, msg);
+    logevent(buf);
+    sfree(buf);
+}
+
+void ssh2_msg_something_unimplemented(Ssh ssh, struct Packet *pktin)
+{
+    struct Packet *pktout;
+    pktout = ssh2_pkt_init(SSH2_MSG_UNIMPLEMENTED);
+    ssh2_pkt_adduint32(pktout, pktin->sequence);
+    /*
+     * UNIMPLEMENTED messages MUST appear in the same order as the
+     * messages they respond to. Hence, never queue them.
+     */
+    ssh2_pkt_send_noqueue(ssh, pktout);
+}
+
+/*
  * Handle the top-level SSH2 protocol.
  */
+static void ssh2_protocol_setup(Ssh ssh)
+{
+    int i;
+
+    /*
+     * Most messages cause SSH2_MSG_UNIMPLEMENTED.
+     */
+    for (i = 0; i < 256; i++)
+       ssh->packet_dispatch[i] = ssh2_msg_something_unimplemented;
+
+    /*
+     * Any message we actually understand, we set to NULL so that
+     * the coroutines will get it.
+     */
+    ssh->packet_dispatch[SSH2_MSG_UNIMPLEMENTED] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_SERVICE_REQUEST] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_SERVICE_ACCEPT] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_KEXINIT] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_NEWKEYS] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_KEXDH_INIT] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_KEXDH_REPLY] = NULL;
+    /* ssh->packet_dispatch[SSH2_MSG_KEX_DH_GEX_REQUEST] = NULL; duplicate case value */
+    /* ssh->packet_dispatch[SSH2_MSG_KEX_DH_GEX_GROUP] = NULL; duplicate case value */
+    ssh->packet_dispatch[SSH2_MSG_KEX_DH_GEX_INIT] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_KEX_DH_GEX_REPLY] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_REQUEST] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_FAILURE] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_SUCCESS] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_BANNER] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_PK_OK] = NULL;
+    /* ssh->packet_dispatch[SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ] = NULL; duplicate case value */
+    /* ssh->packet_dispatch[SSH2_MSG_USERAUTH_INFO_REQUEST] = NULL; duplicate case value */
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_INFO_RESPONSE] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_GLOBAL_REQUEST] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_REQUEST_SUCCESS] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_REQUEST_FAILURE] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN_CONFIRMATION] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN_FAILURE] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_WINDOW_ADJUST] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_DATA] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_EXTENDED_DATA] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_EOF] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_CLOSE] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_REQUEST] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_SUCCESS] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_FAILURE] = NULL;
+
+    /*
+     * These special message types we install handlers for.
+     */
+    ssh->packet_dispatch[SSH2_MSG_DISCONNECT] = ssh2_msg_disconnect;
+    ssh->packet_dispatch[SSH2_MSG_IGNORE] = ssh_msg_ignore; /* shared with ssh1 */
+    ssh->packet_dispatch[SSH2_MSG_DEBUG] = ssh2_msg_debug;
+}
+
+static void ssh2_timer(void *ctx, long now)
+{
+    Ssh ssh = (Ssh)ctx;
+
+    if (!ssh->kex_in_progress && ssh->cfg.ssh_rekey_time != 0 &&
+       now - ssh->next_rekey >= 0) {
+       do_ssh2_transport(ssh, "Initiating key re-exchange (timeout)",
+                         -1, NULL);
+    }
+}
+
 static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen,
                          struct Packet *pktin)
 {
-    if (do_ssh2_transport(ssh, in, inlen, pktin) == 0)
+    if (ssh->state == SSH_STATE_CLOSED)
        return;
-    do_ssh2_authconn(ssh, in, inlen, pktin);
+
+    if (pktin) {
+       ssh->incoming_data_size += pktin->encrypted_len;
+       if (!ssh->kex_in_progress &&
+           ssh->max_data_size != 0 &&
+           ssh->incoming_data_size > ssh->max_data_size)
+           do_ssh2_transport(ssh, "Initiating key re-exchange "
+                             "(too much data received)", -1, NULL);
+    }
+
+    if (pktin && ssh->packet_dispatch[pktin->type]) {
+       ssh->packet_dispatch[pktin->type](ssh, pktin);
+       return;
+    }
+
+    if (!ssh->protocol_initial_phase_done ||
+       (pktin && pktin->type >= 20 && pktin->type < 50)) {
+       if (do_ssh2_transport(ssh, in, inlen, pktin) &&
+           !ssh->protocol_initial_phase_done) {
+           ssh->protocol_initial_phase_done = TRUE;
+           /*
+            * Allow authconn to initialise itself.
+            */
+           do_ssh2_authconn(ssh, NULL, 0, NULL);
+       }
+    } else {
+       do_ssh2_authconn(ssh, in, inlen, pktin);
+    }
 }
 
 /*
@@ -6779,7 +7333,7 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->ssh2_rdpkt_crstate = 0;
     ssh->do_ssh_init_crstate = 0;
     ssh->ssh_gotdata_crstate = 0;
-    ssh->ssh1_protocol_crstate = 0;
+    ssh->do_ssh1_connection_crstate = 0;
     ssh->do_ssh1_login_crstate = 0;
     ssh->do_ssh2_transport_crstate = 0;
     ssh->do_ssh2_authconn_crstate = 0;
@@ -6790,6 +7344,10 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->mainchan = NULL;
     ssh->throttled_all = 0;
     ssh->v1_stdout_throttling = 0;
+    ssh->queue = NULL;
+    ssh->queuelen = ssh->queuesize = 0;
+    ssh->queueing = FALSE;
+    ssh->qhead = ssh->qtail = NULL;
 
     *backend_handle = ssh;
 
@@ -6804,6 +7362,7 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
 
     ssh->channels = NULL;
     ssh->rportfwds = NULL;
+    ssh->portfwds = NULL;
 
     ssh->send_ok = 0;
     ssh->editing = 0;
@@ -6814,10 +7373,21 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
 
     ssh->protocol = NULL;
 
+    ssh->protocol_initial_phase_done = FALSE;
+
+    ssh->pinger = NULL;
+
+    ssh->incoming_data_size = ssh->outgoing_data_size =
+       ssh->deferred_data_size = 0L;
+    ssh->max_data_size = parse_blocksize(ssh->cfg.ssh_rekey_data);
+    ssh->kex_in_progress = FALSE;
+
     p = connect_to_host(ssh, host, port, realhost, nodelay, keepalive);
     if (p != NULL)
        return p;
 
+    random_ref();
+
     return NULL;
 }
 
@@ -6853,6 +7423,17 @@ static void ssh_free(void *handle)
        dh_cleanup(ssh->kex_ctx);
     sfree(ssh->savedhost);
 
+    while (ssh->queuelen-- > 0)
+       ssh_free_packet(ssh->queue[ssh->queuelen]);
+    sfree(ssh->queue);
+
+    while (ssh->qhead) {
+       struct queued_handler *qh = ssh->qhead;
+       ssh->qhead = qh->next;
+       sfree(ssh->qhead);
+    }
+    ssh->qhead = ssh->qtail = NULL;
+
     if (ssh->channels) {
        while ((c = delpos234(ssh->channels, 0)) != NULL) {
            switch (c->type) {
@@ -6868,12 +7449,14 @@ static void ssh_free(void *handle)
            sfree(c);
        }
        freetree234(ssh->channels);
+       ssh->channels = NULL;
     }
 
     if (ssh->rportfwds) {
        while ((pf = delpos234(ssh->rportfwds, 0)) != NULL)
            sfree(pf);
        freetree234(ssh->rportfwds);
+       ssh->rportfwds = NULL;
     }
     sfree(ssh->deferred_send_data);
     if (ssh->x11auth)
@@ -6888,21 +7471,51 @@ static void ssh_free(void *handle)
     }
     if (ssh->s)
        ssh_do_close(ssh);
+    expire_timer_context(ssh);
+    if (ssh->pinger)
+       pinger_free(ssh->pinger);
     sfree(ssh);
+
+    random_unref();
 }
 
 /*
  * Reconfigure the SSH backend.
- * 
- * Currently, this function does nothing very useful. In future,
- * however, we could do some handy things with it. For example, we
- * could make the port forwarding configurer active in the Change
- * Settings box, and this routine could close down existing
- * forwardings and open up new ones in response to changes.
  */
 static void ssh_reconfig(void *handle, Config *cfg)
 {
     Ssh ssh = (Ssh) handle;
+    char *rekeying = NULL;
+    unsigned long old_max_data_size;
+
+    pinger_reconfig(ssh->pinger, &ssh->cfg, cfg);
+    ssh_setup_portfwd(ssh, cfg);
+
+    if (ssh->cfg.ssh_rekey_time != cfg->ssh_rekey_time &&
+       cfg->ssh_rekey_time != 0) {
+       long new_next = ssh->last_rekey + cfg->ssh_rekey_time*60*TICKSPERSEC;
+       long now = GETTICKCOUNT();
+
+       if (new_next - now < 0) {
+           rekeying = "Initiating key re-exchange (timeout shortened)";
+       } else {
+           ssh->next_rekey = schedule_timer(new_next - now, ssh2_timer, ssh);
+       }
+    }
+
+    old_max_data_size = ssh->max_data_size;
+    ssh->max_data_size = parse_blocksize(cfg->ssh_rekey_data);
+    if (old_max_data_size != ssh->max_data_size &&
+       ssh->max_data_size != 0) {
+       if (ssh->outgoing_data_size > ssh->max_data_size ||
+           ssh->incoming_data_size > ssh->max_data_size)
+           rekeying = "Initiating key re-exchange (data limit lowered)";
+    }
+
+    if (rekeying && !ssh->kex_in_progress) {
+       do_ssh2_transport(ssh, rekeying, -1, NULL);
+    }
+
     ssh->cfg = *cfg;                  /* STRUCTURE COPY */
 }
 
@@ -7001,13 +7614,17 @@ static void ssh_size(void *handle, int width, int height)
  */
 static const struct telnet_special *ssh_get_specials(void *handle)
 {
-    static const struct telnet_special ignore_special[] = {
+    static const struct telnet_special ssh1_ignore_special[] = {
+       {"IGNORE message", TS_NOP}
+    };
+    static const struct telnet_special ssh2_transport_specials[] = {
        {"IGNORE message", TS_NOP},
+       {"Repeat key exchange", TS_REKEY},
     };
     static const struct telnet_special ssh2_session_specials[] = {
        {NULL, TS_SEP},
        {"Break", TS_BRK},
-       /* These are the signal names defined by draft-ietf-secsh-connect-19.
+       /* These are the signal names defined by draft-ietf-secsh-connect-23.
         * They include all the ISO C signals, but are a subset of the POSIX
         * required signals. */
        {"SIGINT (Interrupt)", TS_SIGINT},
@@ -7025,7 +7642,8 @@ static const struct telnet_special *ssh_get_specials(void *handle)
     static const struct telnet_special specials_end[] = {
        {NULL, TS_EXITMENU}
     };
-    static struct telnet_special ssh_specials[lenof(ignore_special) +
+    /* XXX review this length for any changes: */
+    static struct telnet_special ssh_specials[lenof(ssh2_transport_specials) +
                                              lenof(ssh2_session_specials) +
                                              lenof(specials_end)];
     Ssh ssh = (Ssh) handle;
@@ -7042,10 +7660,9 @@ static const struct telnet_special *ssh_get_specials(void *handle)
         * won't cope with it, since we wouldn't bother sending it if
         * asked anyway. */
        if (!(ssh->remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE))
-           ADD_SPECIALS(ignore_special);
+           ADD_SPECIALS(ssh1_ignore_special);
     } else if (ssh->version == 2) {
-       /* XXX add rekey, when implemented */
-       ADD_SPECIALS(ignore_special);
+       ADD_SPECIALS(ssh2_transport_specials);
        if (ssh->mainchan)
            ADD_SPECIALS(ssh2_session_specials);
     } /* else we're not ready yet */
@@ -7096,7 +7713,12 @@ static void ssh_special(void *handle, Telnet_Special code)
        } else {
            pktout = ssh2_pkt_init(SSH2_MSG_IGNORE);
            ssh2_pkt_addstring_start(pktout);
-           ssh2_pkt_send(ssh, pktout);
+           ssh2_pkt_send_noqueue(ssh, pktout);
+       }
+    } else if (code == TS_REKEY) {
+       if (!ssh->kex_in_progress && ssh->version == 2) {
+           do_ssh2_transport(ssh, "Initiating key re-exchange at"
+                             " user request", -1, NULL);
        }
     } else if (code == TS_BRK) {
        if (ssh->state == SSH_STATE_CLOSED
@@ -7196,7 +7818,7 @@ void ssh_send_port_open(void *channel, char *hostname, int port, char *org)
                    PKT_INT, c->localid,
                    PKT_STR, hostname,
                    PKT_INT, port,
-                   //PKT_STR, <org:orgport>,
+                   /* PKT_STR, <org:orgport>, */
                    PKT_END);
     } else {
        pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN);
@@ -7263,6 +7885,16 @@ static int ssh_return_exitcode(void *handle)
 }
 
 /*
+ * cfg_info for SSH is the currently running version of the
+ * protocol. (1 for 1; 2 for 2; 0 for not-decided-yet.)
+ */
+static int ssh_cfg_info(void *handle)
+{
+    Ssh ssh = (Ssh) handle;
+    return ssh->version;
+}
+
+/*
  * Gross hack: pscp will try to start SFTP but fall back to scp1 if
  * that fails. This variable is the means by which scp.c can reach
  * into the SSH code and find out which one it got.
@@ -7289,5 +7921,6 @@ Backend ssh_backend = {
     ssh_provide_ldisc,
     ssh_provide_logctx,
     ssh_unthrottle,
+    ssh_cfg_info,
     22
 };