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     void (*set_private_ptr) (Socket s, void *ptr);
  31     void *(*get_private_ptr) (Socket s);
  32     void (*set_frozen) (Socket s, int is_frozen);
  33     /* ignored by tcp, but vital for ssl */
  34     char *(*socket_error) (Socket s);
  35 };
  36
  37 struct plug_function_table {
  38     int (*closing)
  39      (Plug p, char *error_msg, int error_code, int calling_back);
  40     /* error_msg is NULL iff it is not an error (ie it closed normally) */
  41     /* calling_back != 0 iff there is a Plug function */
  42     /* currently running (would cure the fixme in try_send()) */
  43     int (*receive) (Plug p, int urgent, char *data, int len);
  44     /*
  45      *  - urgent==0. `data' points to `len' bytes of perfectly
  46      *    ordinary data.
  47      *
  48      *  - urgent==1. `data' points to `len' bytes of data,
  49      *    which were read from before an Urgent pointer.
  50      *
  51      *  - urgent==2. `data' points to `len' bytes of data,
  52      *    the first of which was the one at the Urgent mark.
  53      */
  54     void (*sent) (Plug p, int bufsize);
  55     /*
  56      * The `sent' function is called when the pending send backlog
  57      * on a socket is cleared or partially cleared. The new backlog
  58      * size is passed in the `bufsize' parameter.
  59      */
  60     int (*accepting)(Plug p, void *sock);
  61     /*
  62      * returns 0 if the host at address addr is a valid host for connecting or error
  63      */
  64 };
  65
  66 /* proxy indirection layer */
  67 Socket new_connection(SockAddr addr, char *hostname,
  68                       int port, int privport,
  69                       int oobinline, int nodelay, Plug plug);
  70 Socket new_listener(int port, Plug plug, int local_host_only);
  71
  72 /* socket functions */
  73
  74 void sk_init(void);                    /* called once at program startup */
  75 void sk_cleanup(void);                 /* called just before program exit */
  76
  77 SockAddr sk_namelookup(char *host, char **canonicalname);
  78 void sk_getaddr(SockAddr addr, char *buf, int buflen);
  79 void sk_addr_free(SockAddr addr);
  80
  81 Socket sk_new(SockAddr addr, int port, int privport, int oobinline,
  82               int nodelay, Plug p);
  83
  84 Socket sk_newlistener(int port, Plug plug, int local_host_only);
  85
  86 Socket sk_register(void *sock, Plug plug);
  87
  88 #define sk_plug(s,p) (((*s)->plug) (s, p))
  89 #define sk_close(s) (((*s)->close) (s))
  90 #define sk_write(s,buf,len) (((*s)->write) (s, buf, len))
  91 #define sk_write_oob(s,buf,len) (((*s)->write_oob) (s, buf, len))
  92 #define sk_flush(s) (((*s)->flush) (s))
  93
  94 #ifdef DEFINE_PLUG_METHOD_MACROS
  95 #define plug_closing(p,msg,code,callback) (((*p)->closing) (p, msg, code, callback))
  96 #define plug_receive(p,urgent,buf,len) (((*p)->receive) (p, urgent, buf, len))
  97 #define plug_sent(p,bufsize) (((*p)->sent) (p, bufsize))
  98 #define plug_accepting(p, sock) (((*p)->accepting)(p, sock))
  99 #endif
 100
 101 /*
 102  * Each socket abstraction contains a `void *' private field in
 103  * which the client can keep state.
 104  *
 105  * This is perhaps unnecessary now that we have the notion of a plug,
 106  * but there is some existing code that uses it, so it stays.
 107  */
 108 #define sk_set_private_ptr(s, ptr) (((*s)->set_private_ptr) (s, ptr))
 109 #define sk_get_private_ptr(s) (((*s)->get_private_ptr) (s))
 110
 111 /*
 112  * Special error values are returned from sk_namelookup and sk_new
 113  * if there's a problem. These functions extract an error message,
 114  * or return NULL if there's no problem.
 115  */
 116 char *sk_addr_error(SockAddr addr);
 117 #define sk_socket_error(s) (((*s)->socket_error) (s))
 118
 119 /*
 120  * Set the `frozen' flag on a socket. A frozen socket is one in
 121  * which all READABLE notifications are ignored, so that data is
 122  * not accepted from the peer until the socket is unfrozen. This
 123  * exists for two purposes:
 124  *
 125  *  - Port forwarding: when a local listening port receives a
 126  *    connection, we do not want to receive data from the new
 127  *    socket until we have somewhere to send it. Hence, we freeze
 128  *    the socket until its associated SSH channel is ready; then we
 129  *    unfreeze it and pending data is delivered.
 130  *
 131  *  - Socket buffering: if an SSH channel (or the whole connection)
 132  *    backs up or presents a zero window, we must freeze the
 133  *    associated local socket in order to avoid unbounded buffer
 134  *    growth.
 135  */
 136 #define sk_set_frozen(s, is_frozen) (((*s)->set_frozen) (s, is_frozen))
 137
 138 /*
 139  * Call this after an operation that might have tried to send on a
 140  * socket, to clean up any pending network errors.
 141  */
 142 void net_pending_errors(void);
 143
 144 /********** SSL stuff **********/
 145
 146 /*
 147  * This section is subject to change, but you get the general idea
 148  * of what it will eventually look like.
 149  */
 150
 151 typedef struct certificate *Certificate;
 152 typedef struct our_certificate *Our_Certificate;
 153     /* to be defined somewhere else, somehow */
 154
 155 typedef struct ssl_client_socket_function_table **SSL_Client_Socket;
 156 typedef struct ssl_client_plug_function_table **SSL_Client_Plug;
 157
 158 struct ssl_client_socket_function_table {
 159     struct socket_function_table base;
 160     void (*renegotiate) (SSL_Client_Socket s);
 161     /* renegotiate the cipher spec */
 162 };
 163
 164 struct ssl_client_plug_function_table {
 165     struct plug_function_table base;
 166     int (*refuse_cert) (SSL_Client_Plug p, Certificate cert[]);
 167     /* do we accept this certificate chain?  If not, why not? */
 168     /* cert[0] is the server's certificate, cert[] is NULL-terminated */
 169     /* the last certificate may or may not be the root certificate */
 170      Our_Certificate(*client_cert) (SSL_Client_Plug p);
 171     /* the server wants us to identify ourselves */
 172     /* may return NULL if we want anonymity */
 173 };
 174
 175 SSL_Client_Socket sk_ssl_client_over(Socket s,  /* pre-existing (tcp) connection */
 176                                      SSL_Client_Plug p);
 177
 178 #define sk_renegotiate(s) (((*s)->renegotiate) (s))
 179
 180 #endif