git.distorted.org.uk Git - u/mdw/putty/blob - network.h

   1 /*
   2  * Networking abstraction in PuTTY.
   3  *
   4  * The way this works is: a back end can choose to open any number
   5  * of sockets - including zero, which might be necessary in some.
   6  * It can register a bunch of callbacks (most notably for when
   7  * data is received) for each socket, and it can call the networking
   8  * abstraction to send data without having to worry about blocking.
   9  * The stuff behind the abstraction takes care of selects and
  10  * nonblocking writes and all that sort of painful gubbins.
  11  */
  12
  13 #ifndef PUTTY_NETWORK_H
  14 #define PUTTY_NETWORK_H
  15
  16 typedef struct SockAddr_tag *SockAddr;
  17 /* pay attention to levels of indirection */
  18 typedef struct socket_function_table **Socket;
  19 typedef struct plug_function_table **Plug;
  20
  21 struct socket_function_table {
  22     Plug(*plug) (Socket s, Plug p);
  23     /* use a different plug (return the old one) */
  24     /* if p is NULL, it doesn't change the plug */
  25     /* but it does return the one it's using */
  26     void (*close) (Socket s);
  27     int (*write) (Socket s, char *data, int len);
  28     int (*write_oob) (Socket s, char *data, int len);
  29     void (*flush) (Socket s);
  30     /* ignored by tcp, but vital for ssl */
  31     char *(*socket_error) (Socket s);
  32 };
  33
  34 struct plug_function_table {
  35     int (*closing)
  36      (Plug p, char *error_msg, int error_code, int calling_back);
  37     /* error_msg is NULL iff it is not an error (ie it closed normally) */
  38     /* calling_back != 0 iff there is a Plug function */
  39     /* currently running (would cure the fixme in try_send()) */
  40     int (*receive) (Plug p, int urgent, char *data, int len);
  41     /*
  42      *  - urgent==0. `data' points to `len' bytes of perfectly
  43      *    ordinary data.
  44      *
  45      *  - urgent==1. `data' points to `len' bytes of data,
  46      *    which were read from before an Urgent pointer.
  47      *
  48      *  - urgent==2. `data' points to `len' bytes of data,
  49      *    the first of which was the one at the Urgent mark.
  50      */
  51     void (*sent) (Plug p, int bufsize);
  52     /*
  53      * The `sent' function is called when the pending send backlog
  54      * on a socket is cleared or partially cleared. The new backlog
  55      * size is passed in the `bufsize' parameter.
  56      */
  57     int (*accepting)(Plug p, void *sock);
  58     /*
  59      * returns 0 if the host at address addr is a valid host for connecting or error
  60      */
  61 };
  62
  63
  64 void sk_init(void);                    /* called once at program startup */
  65
  66 SockAddr sk_namelookup(char *host, char **canonicalname);
  67 void sk_getaddr(SockAddr addr, char *buf, int buflen);
  68 void sk_addr_free(SockAddr addr);
  69
  70 Socket sk_new(SockAddr addr, int port, int privport, int oobinline,
  71               Plug p);
  72
  73 Socket sk_newlistener(int port, Plug plug, int local_host_only);
  74
  75 Socket sk_register(void *sock, Plug plug);
  76
  77 #define sk_plug(s,p) (((*s)->plug) (s, p))
  78 #define sk_close(s) (((*s)->close) (s))
  79 #define sk_write(s,buf,len) (((*s)->write) (s, buf, len))
  80 #define sk_write_oob(s,buf,len) (((*s)->write_oob) (s, buf, len))
  81 #define sk_flush(s) (((*s)->flush) (s))
  82
  83 #ifdef DEFINE_PLUG_METHOD_MACROS
  84 #define plug_closing(p,msg,code,callback) (((*p)->closing) (p, msg, code, callback))
  85 #define plug_receive(p,urgent,buf,len) (((*p)->receive) (p, urgent, buf, len))
  86 #define plug_sent(p,bufsize) (((*p)->sent) (p, bufsize))
  87 #define plug_accepting(p, sock) (((*p)->accepting)(p, sock))
  88 #endif
  89
  90 /*
  91  * Each socket abstraction contains a `void *' private field in
  92  * which the client can keep state.
  93  *
  94  * This is perhaps unnecessary now that we have the notion of a plug,
  95  * but there is some existing code that uses it, so it stays.
  96  */
  97 void sk_set_private_ptr(Socket s, void *ptr);
  98 void *sk_get_private_ptr(Socket s);
  99
 100 /*
 101  * Special error values are returned from sk_namelookup and sk_new
 102  * if there's a problem. These functions extract an error message,
 103  * or return NULL if there's no problem.
 104  */
 105 char *sk_addr_error(SockAddr addr);
 106 #define sk_socket_error(s) (((*s)->socket_error) (s))
 107
 108 /*
 109  * Set the `frozen' flag on a socket. A frozen socket is one in
 110  * which all READABLE notifications are ignored, so that data is
 111  * not accepted from the peer until the socket is unfrozen. This
 112  * exists for two purposes:
 113  *
 114  *  - Port forwarding: when a local listening port receives a
 115  *    connection, we do not want to receive data from the new
 116  *    socket until we have somewhere to send it. Hence, we freeze
 117  *    the socket until its associated SSH channel is ready; then we
 118  *    unfreeze it and pending data is delivered.
 119  *
 120  *  - Socket buffering: if an SSH channel (or the whole connection)
 121  *    backs up or presents a zero window, we must freeze the
 122  *    associated local socket in order to avoid unbounded buffer
 123  *    growth.
 124  */
 125 void sk_set_frozen(Socket sock, int is_frozen);
 126
 127 /*
 128  * Call this after an operation that might have tried to send on a
 129  * socket, to clean up any pending network errors.
 130  */
 131 void net_pending_errors(void);
 132
 133 /********** SSL stuff **********/
 134
 135 /*
 136  * This section is subject to change, but you get the general idea
 137  * of what it will eventually look like.
 138  */
 139
 140 typedef struct certificate *Certificate;
 141 typedef struct our_certificate *Our_Certificate;
 142     /* to be defined somewhere else, somehow */
 143
 144 typedef struct ssl_client_socket_function_table **SSL_Client_Socket;
 145 typedef struct ssl_client_plug_function_table **SSL_Client_Plug;
 146
 147 struct ssl_client_socket_function_table {
 148     struct socket_function_table base;
 149     void (*renegotiate) (SSL_Client_Socket s);
 150     /* renegotiate the cipher spec */
 151 };
 152
 153 struct ssl_client_plug_function_table {
 154     struct plug_function_table base;
 155     int (*refuse_cert) (SSL_Client_Plug p, Certificate cert[]);
 156     /* do we accept this certificate chain?  If not, why not? */
 157     /* cert[0] is the server's certificate, cert[] is NULL-terminated */
 158     /* the last certificate may or may not be the root certificate */
 159      Our_Certificate(*client_cert) (SSL_Client_Plug p);
 160     /* the server wants us to identify ourselves */
 161     /* may return NULL if we want anonymity */
 162 };
 163
 164 SSL_Client_Socket sk_ssl_client_over(Socket s,  /* pre-existing (tcp) connection */
 165                                      SSL_Client_Plug p);
 166
 167 #define sk_renegotiate(s) (((*s)->renegotiate) (s))
 168
 169 #endif