[tripe] / server / peer.c

/* -*-c-*-
 *
 * Communication with the peer
 *
 * (c) 2001 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of Trivial IP Encryption (TrIPE).
 *
 * TrIPE is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * TrIPE is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with TrIPE; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*----- Header files ------------------------------------------------------*/

#include "tripe.h"

/*----- Static variables --------------------------------------------------*/

static sym_table byname;
static addrmap byaddr;
static sel_file sock;
static unsigned nmobile;

/*----- Tunnel table ------------------------------------------------------*/

const tunnel_ops *tunnels[] = {
#ifdef TUN_LINUX
  &tun_linux,
#endif
#ifdef TUN_BSD
  &tun_bsd,
#endif
#ifdef TUN_UNET
  &tun_unet,
#endif
  &tun_slip,
  0
}, *tun_default;

/*----- Main code ---------------------------------------------------------*/

/* --- @p_pingtype@ --- *
 *
 * Arguments:   @unsigned msg@ = message type
 *
 * Returns:     String to describe the message.
 */

static const char *p_pingtype(unsigned msg)
{
  switch (msg & MSG_TYPEMASK) {
    case MISC_PING:
    case MISC_PONG:
      return "transport-ping";
    case MISC_EPING:
    case MISC_EPONG:
      return "encrypted-ping";
    default:
      abort();
  }
}

/* --- @p_ponged@ --- *
 *
 * Arguments:   @peer *p@ = peer packet arrived from
 *              @unsigned msg@ = message type
 *              @buf *b@ = buffer containing payload
 *
 * Returns:     ---
 *
 * Use:         Processes a ping response.
 */

static void p_ponged(peer *p, unsigned msg, buf *b)
{
  uint32 id;
  const octet *magic;
  ping *pg;

  IF_TRACING(T_PEER, {
    trace(T_PEER, "peer: received %s reply from %s",
          p_pingtype(msg), p->spec.name);
    trace_block(T_PACKET, "peer: ping contents", BBASE(b), BSZ(b));
  })

  if (buf_getu32(b, &id) ||
      (magic = buf_get(b, sizeof(pg->magic))) == 0 ||
      BLEFT(b)) {
    a_warn("PEER", "?PEER", p, "malformed-%s", p_pingtype(msg), A_END);
    return;
  }

  for (pg = p->pings; pg; pg = pg->next) {
    if (pg->id == id)
      goto found;
  }
  a_warn("PEER",
         "?PEER", p,
         "unexpected-%s", p_pingtype(msg),
         "0x%08lx", (unsigned long)id,
         A_END);
  return;

found:
  if (memcmp(magic, pg->magic, sizeof(pg->magic)) != 0) {
    a_warn("PEER", "?PEER", p, "corrupt-%s", p_pingtype(msg), A_END);
    return;
  }
  p_pingdone(pg, PING_OK);
}

/* --- @p_rxupdstats@ --- *
 *
 * Arguments:   @peer *p@ = peer to update
 *              @size_t n@ = size of incoming packet
 *
 * Returns:     ---
 *
 * Use:         Updates the peer's incoming packet statistics.
 */

static void p_rxupdstats(peer *p, size_t n)
{
  p->st.t_last = time(0);
  p->st.n_in++;
  p->st.sz_in += n;
}

/* --- @p_encrypt@ --- *
 *
 * Arguments:   @peer *p@ = peer to encrypt message to
 *              @int ty@ message type to send
 *              @buf *bin, *bout@ = input and output buffers
 *
 * Returns:     ---
 *
 * Use:         Convenience function for packet encryption.  Forces
 *              renegotiation when necessary.  Check for the output buffer
 *              being broken to find out whether the encryption was
 *              successful.
 */

static int p_encrypt(peer *p, int ty, buf *bin, buf *bout)
{
  int err = ksl_encrypt(&p->ks, ty, bin, bout);

  if (err == KSERR_REGEN) {
    kx_start(&p->kx, 1);
    err = 0;
  }
  if (!BOK(bout))
    err = -1;
  return (err);
}

/* --- @p_decrypt@ --- *
 *
 * Arguments:   @peer **pp@ = pointer to peer to decrypt message from
 *              @addr *a@ = address the packet arrived on
 *              @size_t n@ = size of original incoming packet
 *              @int ty@ = message type to expect
 *              @buf *bin, *bout@ = input and output buffers
 *
 * Returns:     Zero on success; nonzero on error.
 *
 * Use:         Convenience function for packet decryption.  Reports errors
 *              and updates statistics appropriately.
 *
 *              If @*pp@ is null on entry and there are mobile peers then we
 *              see if any of them can decrypt the packet.  If so, we record
 *              @*a@ as the peer's new address and send a notification.
 */

static int p_decrypt(peer **pp, addr *a, size_t n,
                     int ty, buf *bin, buf *bout)
{
  peer *p;
  peer_byaddr *pa;
  int err = KSERR_DECRYPT;
  unsigned f;

  if (*pp) {
    p = *pp;
    T( trace(T_PEER, "peer: decrypting packet from known peer `%s'",
             p_name(p)); )
    err = ksl_decrypt(&p->ks, ty, bin, bout);
  } else {
    p = 0;
    if (nmobile) {
      T( trace(T_PEER, "peer: unknown source: trying mobile peers..."); )
      FOREACH_PEER(q, {
        if (!(q->spec.f & PSF_MOBILE)) continue;
        if ((err = ksl_decrypt(&q->ks, ty, bin, bout)) == KSERR_DECRYPT) {
          T( trace(T_PEER, "peer: peer `%s' failed to decrypt",
                   p_name(q)); )
          continue;
        } else {
          p = *pp = q;
          IF_TRACING(T_PEER, {
            if (!err)
              trace(T_PEER, "peer: peer `%s' reports success", p_name(p));
            else {
              trace(T_PEER, "peer: peer `%s' reports decryption error %d",
                    p_name(p), err);
            }
          })
          break;
        }
      });
    }
    if (!p) {
      a_warn("PEER", "-", "unexpected-source", "?ADDR", a, A_END);
      return (-1);
    }
    if (!err) {
      T( trace(T_PEER, "peer: updating address for `%s'", p_name(p)); )
      p_rxupdstats(p, n);
      pa = am_find(&byaddr, a, sizeof(peer_byaddr), &f); assert(!f);
      am_remove(&byaddr, p->byaddr);
      p->byaddr = pa;
      pa->p = p;
      p->spec.sa = *a;
      a_notify("NEWADDR", "?PEER", p, "?ADDR", a, A_END);
    }
  }
  if (err) {
    if (p) p->st.n_reject++;
    a_warn("PEER", "?PEER", p, "decrypt-failed",
           "error-code", "%d", err, A_END);
    return (-1);
  }
  if (!BOK(bout))
    return (-1);
  return (0);
}

/* --- @p_read@ --- *
 *
 * Arguments:   @int fd@ = file descriptor to read from
 *              @unsigned mode@ = what happened
 *              @void *v@ = an uninteresting pointer
 *
 * Returns:     ---
 *
 * Use:         Reads a packet from somewhere.
 */

static void p_read(int fd, unsigned mode, void *v)
{
  peer *p = 0;
  addr a;
  size_t sz;
  ssize_t n;
  int ch;
  buf b, bb;

  /* --- Read the data --- */

  TIMER;
  sz = sizeof(addr);
  n = recvfrom(fd, buf_i, sizeof(buf_i), 0, &a.sa, &sz);
  if (n < 0) {
    a_warn("PEER", "-", "socket-read-error", "?ERRNO", A_END);
    return;
  }

  /* --- If the packet is a greeting, don't check peers --- */

  if (n && buf_i[0] == (MSG_MISC | MISC_GREET)) {
    IF_TRACING(T_PEER, {
      trace(T_PEER, "peer: greeting received from INET %s %u",
            inet_ntoa(a.sin.sin_addr),
            (unsigned)ntohs(a.sin.sin_port));
      trace_block(T_PACKET, "peer: greeting contents", buf_i, n);
    })
    buf_init(&b, buf_i, n);
    buf_getbyte(&b);
    if (c_check(&b) || BLEFT(&b)) {
      a_warn("PEER", "-", "invalid-greeting", A_END);
      return;
    }
    a_notify("GREET",
             "?B64", buf_i + 1, (size_t)(n - 1),
             "?ADDR", &a,
             A_END);
    return;
  }

  /* --- Find the appropriate peer --- *
   *
   * At this stage, don't worry too much about whether we actually found it.
   */

  p = p_findbyaddr(&a);

  IF_TRACING(T_PEER, {
    if (p) {
      trace(T_PEER,
            "peer: packet received from `%s' from address INET %s %d",
            p_name(p), inet_ntoa(a.sin.sin_addr), ntohs(a.sin.sin_port));
    } else {
      trace(T_PEER, "peer: packet received from unknown address INET %s %d",
            inet_ntoa(a.sin.sin_addr), ntohs(a.sin.sin_port));
    }
    trace_block(T_PACKET, "peer: packet contents", buf_i, n);
  })

  /* --- Pick the packet apart --- */

  if (p) p_rxupdstats(p, n);
  buf_init(&b, buf_i, n);
  if ((ch = buf_getbyte(&b)) < 0) {
    a_warn("PEER", "?PEER", p, "bad-packet", "no-type", A_END);
    return;
  }
  switch (ch & MSG_CATMASK) {
    case MSG_PACKET:
      if (ch & MSG_TYPEMASK) {
        a_warn("PEER",
               "?PEER", p,
               "bad-packet",
               "unknown-type", "0x%02x", ch,
               A_END);
        if (p) p->st.n_reject++;
        return;
      }
      buf_init(&bb, buf_o, sizeof(buf_o));
      if (p_decrypt(&p, &a, n, MSG_PACKET, &b, &bb))
        return;
      if (BOK(&bb)) {
        p->st.n_ipin++;
        p->st.sz_ipin += BSZ(&b);
        p->t->ops->inject(p->t, &bb);
      } else {
        p->st.n_reject++;
        a_warn("PEER", "?PEER", p, "packet-build-failed", A_END);
      }
      break;
    case MSG_KEYEXCH:
      if (!p) goto unexp;
      kx_message(&p->kx, ch & MSG_TYPEMASK, &b);
      break;
    case MSG_MISC:
      switch (ch & MSG_TYPEMASK) {
        case MISC_NOP:
          if (!p) goto unexp;
          T( trace(T_PEER, "peer: received NOP packet"); )
          break;
        case MISC_PING:
          if (!p) goto unexp;
          buf_put(p_txstart(p, MSG_MISC | MISC_PONG), BCUR(&b), BLEFT(&b));
          p_txend(p);
          break;
        case MISC_PONG:
          if (!p) goto unexp;
          p_ponged(p, MISC_PONG, &b);
          break;
        case MISC_EPING:
          buf_init(&bb, buf_t, sizeof(buf_t));
          if (p_decrypt(&p, &a, n, ch, &b, &bb))
            return;
          if (BOK(&bb)) {
            buf_flip(&bb);
            p_encrypt(p, MSG_MISC | MISC_EPONG, &bb,
                      p_txstart(p, MSG_MISC | MISC_EPONG));
            p_txend(p);
          }
          break;
        case MISC_EPONG:
          buf_init(&bb, buf_t, sizeof(buf_t));
          if (p_decrypt(&p, &a, n, ch, &b, &bb))
            return;
          if (BOK(&bb)) {
            buf_flip(&bb);
            p_ponged(p, MISC_EPONG, &bb);
          }
          break;
      }
      break;
    default:
      if (p) p->st.n_reject++;
      a_warn("PEER",
             "?PEER", p,
             "bad-packet",
             "unknown-category", "0x%02x", ch,
             A_END);
      break;
    unexp:
      a_warn("PEER", "-", "unexpected-source", "?ADDR", &a, A_END);
      break;
  }
}

/* --- @p_txstart@ --- *
 *
 * Arguments:   @peer *p@ = pointer to peer block
 *              @unsigned msg@ = message type code
 *
 * Returns:     A pointer to a buffer to write to.
 *
 * Use:         Starts sending to a peer.  Only one send can happen at a
 *              time.
 */

buf *p_txstart(peer *p, unsigned msg)
{
  buf_init(&p->b, buf_o, sizeof(buf_o));
  buf_putbyte(&p->b, msg);
  return (&p->b);
}

/* --- @p_txend@ --- *
 *
 * Arguments:   @peer *p@ = pointer to peer block
 *
 * Returns:     ---
 *
 * Use:         Sends a packet to the peer.
 */

static void p_setkatimer(peer *);

static int p_dotxend(peer *p)
{
  if (!BOK(&p->b)) {
    a_warn("PEER", "?PEER", p, "packet-build-failed", A_END);
    return (0);
  }
  IF_TRACING(T_PEER, trace_block(T_PACKET, "peer: sending packet",
                                 BBASE(&p->b), BLEN(&p->b)); )
  if (sendto(sock.fd, BBASE(&p->b), BLEN(&p->b),
             0, &p->spec.sa.sa, p->spec.sasz) < 0) {
    a_warn("PEER", "?PEER", p, "socket-write-error", "?ERRNO", A_END);
    return (0);
  } else {
    p->st.n_out++;
    p->st.sz_out += BLEN(&p->b);
    return (1);
  }
}

void p_txend(peer *p)
{
  if (p_dotxend(p) && p->spec.t_ka) {
    sel_rmtimer(&p->tka);
    p_setkatimer(p);
  }
}

/* --- @p_pingwrite@ --- *
 *
 * Arguments:   @ping *p@ = ping structure
 *              @buf *b@ = buffer to write in
 *
 * Returns:     ---
 *
 * Use:         Fills in a ping structure and writes the packet payload.
 */

static void p_pingwrite(ping *p, buf *b)
{
  static uint32 seq = 0;

  p->id = U32(seq++);
  GR_FILL(&rand_global, p->magic, sizeof(p->magic));
  buf_putu32(b, p->id);
  buf_put(b, p->magic, sizeof(p->magic));
}

/* --- @p_pingdone@ --- *
 *
 * Arguments:   @ping *p@ = ping structure
 *              @int rc@ = return code to pass on
 *
 * Returns:     ---
 *
 * Use:         Disposes of a ping structure, maybe sending a notification.
 */

void p_pingdone(ping *p, int rc)
{
  if (p->prev) p->prev->next = p->next;
  else p->p->pings = p->next;
  if (p->next) p->next->prev = p->prev;
  if (rc != PING_TIMEOUT) sel_rmtimer(&p->t);
  T( trace(T_PEER, "peer: ping 0x%08lx done (rc = %d)",
           (unsigned long)p->id, rc); )
  if (rc >= 0) p->func(rc, p->arg);
}

/* --- @p_pingtimeout@ --- *
 *
 * Arguments:   @struct timeval *now@ = the time now
 *              @void *pv@ = pointer to ping block
 *
 * Returns:     ---
 *
 * Use:         Called when a ping times out.
 */

static void p_pingtimeout(struct timeval *now, void *pv)
{
  ping *p = pv;

  T( trace(T_PEER, "peer: ping 0x%08lx timed out", (unsigned long)p->id); )
  p_pingdone(p, PING_TIMEOUT);
}

/* --- @p_pingsend@ --- *
 *
 * Arguments:   @peer *p@ = destination peer
 *              @ping *pg@ = structure to fill in
 *              @unsigned type@ = message type
 *              @unsigned long timeout@ = how long to wait before giving up
 *              @void (*func)(int, void *)@ = callback function
 *              @void *arg@ = argument for callback
 *
 * Returns:     Zero if successful, nonzero if it failed.
 *
 * Use:         Sends a ping to a peer.  Call @func@ with a nonzero argument
 *              if we get an answer within the timeout, or zero if no answer.
 */

int p_pingsend(peer *p, ping *pg, unsigned type,
               unsigned long timeout,
               void (*func)(int, void *), void *arg)
{
  buf *b, bb;
  struct timeval tv;

  switch (type) {
    case MISC_PING:
      pg->msg = MISC_PONG;
      b = p_txstart(p, MSG_MISC | MISC_PING);
      p_pingwrite(pg, b);
      p_txend(p);
      break;
    case MISC_EPING:
      pg->msg = MISC_EPONG;
      b = p_txstart(p, MSG_MISC | MISC_EPING);
      buf_init(&bb, buf_t, sizeof(buf_t));
      p_pingwrite(pg, &bb);
      buf_flip(&bb);
      p_encrypt(p, MSG_MISC | MISC_EPING, &bb, b);
      if (!BOK(b))
        return (-1);
      p_txend(p);
      break;
    default:
      abort();
      break;
  }

  pg->next = p->pings;
  pg->prev = 0;
  pg->p = p;
  pg->func = func;
  pg->arg = arg;
  if (p->pings) p->pings->prev = pg;
  p->pings = pg;
  gettimeofday(&tv, 0);
  tv.tv_sec += timeout;
  sel_addtimer(&sel, &pg->t, &tv, p_pingtimeout, pg);
  T( trace(T_PEER, "peer: send %s 0x%08lx to %s",
           p_pingtype(type), (unsigned long)pg->id, p->spec.name); )
  return (0);
}

/* --- @p_greet@ --- *
 *
 * Arguments:   @peer *p@ = peer to send to
 *              @const void *c@ = pointer to challenge
 *              @size_t sz@ = size of challenge
 *
 * Returns:     ---
 *
 * Use:         Sends a greeting packet.
 */

void p_greet(peer *p, const void *c, size_t sz)
{
  buf *b = p_txstart(p, MSG_MISC | MISC_GREET);
  buf_put(b, c, sz);
  p_txend(p);
}

/* --- @p_tun@ --- *
 *
 * Arguments:   @peer *p@ = pointer to peer block
 *              @buf *b@ = buffer containing incoming packet
 *
 * Returns:     ---
 *
 * Use:         Handles a packet which needs to be sent to a peer.
 */

void p_tun(peer *p, buf *b)
{
  buf *bb = p_txstart(p, MSG_PACKET);

  TIMER;
  p_encrypt(p, MSG_PACKET, b, bb);
  if (BOK(bb) && BLEN(bb)) {
    p->st.n_ipout++;
    p->st.sz_ipout += BLEN(bb);
    p_txend(p);
  }
}

/* --- @p_keyreload@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Forces a check of the daemon's keyring files.
 */

void p_keyreload(void)
{
  if (km_reload())
    FOREACH_PEER(p, { kx_newkeys(&p->kx); });
}

/* --- @p_interval@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Called periodically to do tidying.
 */

void p_interval(void)
{
  p_keyreload();
  FOREACH_PEER(p, { ksl_prune(&p->ks); });
}

/* --- @p_stats@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's statistics.
 */

stats *p_stats(peer *p) { return (&p->st); }

/* --- @p_ifname@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's interface name.
 */

const char *p_ifname(peer *p) { return (p->ifname); }

/* --- @p_setifname@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *              @const char *name@ = pointer to the new name
 *
 * Returns:     ---
 *
 * Use:         Changes the name held for a peer's interface.
 */

void p_setifname(peer *p, const char *name)
{
  xfree(p->ifname);
  p->ifname = xstrdup(name);
  if (p->spec.tops->setifname)
    p->spec.tops->setifname(p->t, name);
}

/* --- @p_addr@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's address.
 */

const addr *p_addr(peer *p) { return (&p->spec.sa); }

/* --- @p_init@ --- *
 *
 * Arguments:   @struct in_addr addr@ = address to bind to
 *              @unsigned port@ = port number to listen to
 *
 * Returns:     ---
 *
 * Use:         Initializes the peer system; creates the socket.
 */

void p_init(struct in_addr addr, unsigned port)
{
  int fd;
  struct sockaddr_in sin;
  int len = PKBUFSZ;

  /* --- Note on socket buffer sizes --- *
   *
   * For some bizarre reason, Linux 2.2 (at least) doubles the socket buffer
   * sizes I pass to @setsockopt@.  I'm not putting special-case code here
   * for Linux: BSD (at least TCPv2) does what I tell it rather than second-
   * guessing me.
   */

  if ((fd = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
    die(EXIT_FAILURE, "socket creation failed: %s", strerror(errno));
  BURN(sin);
  sin.sin_family = AF_INET;
  sin.sin_addr = addr;
  sin.sin_port = htons(port);
  if (bind(fd, (struct sockaddr *)&sin, sizeof(sin)))
    die(EXIT_FAILURE, "bind failed: %s", strerror(errno));
  if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &len, sizeof(len)) ||
      setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &len, sizeof(len))) {
    die(EXIT_FAILURE, "failed to set socket buffer sizes: %s",
        strerror(errno));
  }
  fdflags(fd, O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
  sel_initfile(&sel, &sock, fd, SEL_READ, p_read, 0);
  sel_addfile(&sock);
  T( trace(T_PEER, "peer: created socket"); )

  sym_create(&byname);
  am_create(&byaddr);
}

/* --- @p_port@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     Port number used for socket.
 */

unsigned p_port(void)
{
  addr a;
  size_t sz = sizeof(addr);

  if (getsockname(sock.fd, &a.sa, &sz))
    die(EXIT_FAILURE, "couldn't read port number: %s", strerror(errno));
  assert(a.sa.sa_family == AF_INET);
  return (ntohs(a.sin.sin_port));
}

/* --- @p_keepalive@ --- *
 *
 * Arguments:   @struct timeval *now@ = the current time
 *              @void *pv@ = peer to wake up
 *
 * Returns:     ---
 *
 * Use:         Sends a keepalive ping message to its peer.
 */

static void p_keepalive(struct timeval *now, void *pv)
{
  peer *p = pv;
  p_txstart(p, MSG_MISC | MISC_NOP); p_dotxend(p);
  T( trace(T_PEER, "peer: sent keepalive to %s", p->spec.name); )
  p_setkatimer(p);
}

/* --- @p_setkatimer@ --- *
 *
 * Arguments:   @peer *p@ = peer to set
 *
 * Returns:     ---
 *
 * Use:         Resets the keepalive timer thing.
 */

static void p_setkatimer(peer *p)
{
  struct timeval tv;

  if (!p->spec.t_ka)
    return;
  gettimeofday(&tv, 0);
  tv.tv_sec += p->spec.t_ka;
  sel_addtimer(&sel, &p->tka, &tv, p_keepalive, p);
}

/* --- @p_create@ --- *
 *
 * Arguments:   @peerspec *spec@ = information about this peer
 *
 * Returns:     Pointer to the peer block, or null if it failed.
 *
 * Use:         Creates a new named peer block.  No peer is actually attached
 *              by this point.
 */

peer *p_create(peerspec *spec)
{
  peer *p = CREATE(peer);
  const tunnel_ops *tops = spec->tops;
  int fd;
  unsigned f;

  p->byname = sym_find(&byname, spec->name, -1, sizeof(peer_byname), &f);
  if (f) goto tidy_0;
  p->byaddr = am_find(&byaddr, &spec->sa, sizeof(peer_byaddr), &f);
  if (f) goto tidy_1;
  p->byname->p = p->byaddr->p = p;

  T( trace(T_PEER, "peer: creating new peer `%s'", spec->name); )
  p->spec = *spec;
  p->spec.name = (/*unconst*/ char *)SYM_NAME(p->byname);
  if (spec->tag)
    p->spec.tag = xstrdup(spec->tag);
  p->ks = 0;
  p->pings = 0;
  p->ifname = 0;
  memset(&p->st, 0, sizeof(stats));
  p->st.t_start = time(0);
  if (!(tops->flags & TUNF_PRIVOPEN))
    fd = -1;
  else if ((fd = ps_tunfd(tops, &p->ifname)) < 0)
    goto tidy_2;
  if ((p->t = tops->create(p, fd, &p->ifname)) == 0)
    goto tidy_3;
  T( trace(T_TUNNEL, "peer: attached interface %s to peer `%s'",
           p->ifname, p_name(p)); )
  p_setkatimer(p);
  if (kx_init(&p->kx, p, &p->ks, p->spec.f & PSF_KXMASK))
    goto tidy_4;
  a_notify("ADD",
           "?PEER", p,
           "%s", p->ifname,
           "?ADDR", &p->spec.sa,
           A_END);
  if (!(p->spec.f & KXF_CORK)) {
    a_notify("KXSTART", "?PEER", p, A_END);
    /* Couldn't tell anyone before */
  }
  if (p->spec.f & PSF_MOBILE) nmobile++;
  return (p);

tidy_4:
  if (spec->t_ka)
    sel_rmtimer(&p->tka);
  xfree(p->ifname);
  p->t->ops->destroy(p->t);
tidy_3:
  if (fd >= 0) close(fd);
tidy_2:
  am_remove(&byaddr, p->byaddr);
  if (p->spec.tag) xfree(p->spec.tag);
tidy_1:
  sym_remove(&byname, p->byname);
tidy_0:
  DESTROY(p);
  return (0);
}

/* --- @p_name@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's name.
 */

const char *p_name(peer *p)
  { if (p) return (p->spec.name); else return ("-"); }

/* --- @p_tag@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     A pointer to the peer's public key tag.
 */

const char *p_tag(peer *p)
  { return (p->spec.tag ? p->spec.tag : p->spec.name); }

/* --- @p_spec@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer block
 *
 * Returns:     Pointer to the peer's specification
 */

const peerspec *p_spec(peer *p) { return (&p->spec); }

/* --- @p_findbyaddr@ --- *
 *
 * Arguments:   @const addr *a@ = address to look up
 *
 * Returns:     Pointer to the peer block, or null if not found.
 *
 * Use:         Finds a peer by address.
 */

peer *p_findbyaddr(const addr *a)
{
  peer_byaddr *pa;

  if ((pa = am_find(&byaddr, a, 0, 0)) != 0) {
    assert(pa->p);
    return (pa->p);
  }
  return (0);
}

/* --- @p_find@ --- *
 *
 * Arguments:   @const char *name@ = name to look up
 *
 * Returns:     Pointer to the peer block, or null if not found.
 *
 * Use:         Finds a peer by name.
 */

peer *p_find(const char *name)
{
  peer_byname *pn;

  if ((pn = sym_find(&byname, name, -1, 0, 0)) != 0)
    return (pn->p);
  return (0);
}

/* --- @p_destroy@ --- *
 *
 * Arguments:   @peer *p@ = pointer to a peer
 *
 * Returns:     ---
 *
 * Use:         Destroys a peer.
 */

void p_destroy(peer *p)
{
  ping *pg, *ppg;

  T( trace(T_PEER, "peer: destroying peer `%s'", p->spec.name); )
  a_notify("KILL", "%s", p->spec.name, A_END);
  ksl_free(&p->ks);
  kx_free(&p->kx);
  if (p->spec.f & PSF_MOBILE)
    nmobile--;
  if (p->ifname)
    xfree(p->ifname);
  if (p->spec.tag)
    xfree(p->spec.tag);
  p->t->ops->destroy(p->t);
  if (p->spec.t_ka)
    sel_rmtimer(&p->tka);
  for (pg = p->pings; pg; pg = ppg) {
    ppg = pg->next;
    p_pingdone(pg, PING_PEERDIED);
  }
  sym_remove(&byname, p->byname);
  am_remove(&byaddr, p->byaddr);
  DESTROY(p);
}

/* --- @p_mkiter@ --- *
 *
 * Arguments:   @peer_iter *i@ = pointer to an iterator
 *
 * Returns:     ---
 *
 * Use:         Initializes the iterator.
 */

void p_mkiter(peer_iter *i) { sym_mkiter(&i->i, &byname); }

/* --- @p_next@ --- *
 *
 * Arguments:   @peer_iter *i@ = pointer to an iterator
 *
 * Returns:     Next peer, or null if at the end.
 *
 * Use:         Returns the next peer.
 */

peer *p_next(peer_iter *i)
{
  peer_byname *pn;

  if ((pn = sym_next(&i->i)) == 0)
    return (0);
  return (pn->p);
}

/*----- That's all, folks -------------------------------------------------*/