src/src/ip.c

   1 /* $Cambridge: exim/src/src/ip.c,v 1.8 2009/11/16 19:50:37 nm4 Exp $ */
   2
   3 /*************************************************
   4 *     Exim - an Internet mail transport agent    *
   5 *************************************************/
   6
   7 /* Copyright (c) University of Cambridge 1995 - 2009 */
   8 /* See the file NOTICE for conditions of use and distribution. */
   9
  10 /* Functions for doing things with sockets. With the advent of IPv6 this has
  11 got messier, so that it's worth pulling out the code into separate functions
  12 that other parts of Exim can call, expecially as there are now several
  13 different places in the code where sockets are used. */
  14
  15
  16 #include "exim.h"
  17
  18
  19 /*************************************************
  20 *             Create a socket                    *
  21 *************************************************/
  22
  23 /* Socket creation happens in a number of places so it's packaged here for
  24 convenience.
  25
  26 Arguments:
  27   type       SOCK_DGRAM or SOCK_STREAM
  28   af         AF_INET or AF_INET6
  29
  30 Returns:     socket number or -1 on failure
  31 */
  32
  33 int
  34 ip_socket(int type, int af)
  35 {
  36 int sock = socket(af, type, 0);
  37 if (sock < 0)
  38   log_write(0, LOG_MAIN, "IPv%c socket creation failed: %s",
  39     (af == AF_INET6)? '6':'4', strerror(errno));
  40 return sock;
  41 }
  42
  43
  44
  45
  46 #if HAVE_IPV6
  47 /*************************************************
  48 *      Convert printing address to numeric       *
  49 *************************************************/
  50
  51 /* This function converts the textual form of an IP address into a numeric form
  52 in an appropriate structure in an IPv6 environment. The getaddrinfo() function
  53 can (apparently) handle more complicated addresses (e.g. those containing
  54 scopes) than inet_pton() in some environments. We use hints to tell it that the
  55 input must be a numeric address.
  56
  57 However, apparently some operating systems (or libraries) don't support
  58 getaddrinfo(), so there is a build-time option to revert to inet_pton() (which
  59 does not support scopes).
  60
  61 Arguments:
  62   address     textual form of the address
  63   addr        where to copy back the answer
  64
  65 Returns:      nothing - failure provokes a panic-die
  66 */
  67
  68 static void
  69 ip_addrinfo(uschar *address, struct sockaddr_in6 *saddr)
  70 {
  71 #ifdef IPV6_USE_INET_PTON
  72
  73   if (inet_pton(AF_INET6, CS address, &saddr->sin6_addr) != 1)
  74     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "unable to parse \"%s\" as an "
  75       "IP address", address);
  76   saddr->sin6_family = AF_INET6;
  77
  78 #else
  79
  80   int rc;
  81   struct addrinfo hints, *res;
  82   memset(&hints, 0, sizeof(hints));
  83   hints.ai_family = AF_INET6;
  84   hints.ai_socktype = SOCK_STREAM;
  85   hints.ai_flags = AI_NUMERICHOST;
  86   if ((rc = getaddrinfo(CS address, NULL, &hints, &res)) != 0 || res == NULL)
  87     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "unable to parse \"%s\" as an "
  88       "IP address: %s", address,
  89       (rc == 0)? "NULL result returned" : gai_strerror(rc));
  90   memcpy(saddr, res->ai_addr, res->ai_addrlen);
  91   freeaddrinfo(res);
  92
  93 #endif
  94 }
  95 #endif  /* HAVE_IPV6 */
  96
  97
  98 /*************************************************
  99 *         Bind socket to interface and port      *
 100 *************************************************/
 101
 102 /* This function binds a socket to a local interface address and port. For a
 103 wildcard IPv6 bind, the address is ":".
 104
 105 Arguments:
 106   sock           the socket
 107   af             AF_INET or AF_INET6 - the socket type
 108   address        the IP address, in text form
 109   port           the IP port (host order)
 110
 111 Returns:         the result of bind()
 112 */
 113
 114 int
 115 ip_bind(int sock, int af, uschar *address, int port)
 116 {
 117 int s_len;
 118 union sockaddr_46 sin;
 119 memset(&sin, 0, sizeof(sin));
 120
 121 /* Setup code when using an IPv6 socket. The wildcard address is ":", to
 122 ensure an IPv6 socket is used. */
 123
 124 #if HAVE_IPV6
 125 if (af == AF_INET6)
 126   {
 127   if (address[0] == ':' && address[1] == 0)
 128     {
 129     sin.v6.sin6_family = AF_INET6;
 130     sin.v6.sin6_addr = in6addr_any;
 131     }
 132   else
 133     {
 134     ip_addrinfo(address, &sin.v6);  /* Panic-dies on error */
 135     }
 136   sin.v6.sin6_port = htons(port);
 137   s_len = sizeof(sin.v6);
 138   }
 139 else
 140 #else     /* HAVE_IPv6 */
 141 af = af;  /* Avoid compiler warning */
 142 #endif    /* HAVE_IPV6 */
 143
 144 /* Setup code when using IPv4 socket. The wildcard address is "". */
 145
 146   {
 147   sin.v4.sin_family = AF_INET;
 148   sin.v4.sin_port = htons(port);
 149   s_len = sizeof(sin.v4);
 150   if (address[0] == 0)
 151     sin.v4.sin_addr.s_addr = (S_ADDR_TYPE)INADDR_ANY;
 152   else
 153     sin.v4.sin_addr.s_addr = (S_ADDR_TYPE)inet_addr(CS address);
 154   }
 155
 156 /* Now we can call the bind() function */
 157
 158 return bind(sock, (struct sockaddr *)&sin, s_len);
 159 }
 160
 161
 162
 163 /*************************************************
 164 *        Connect socket to remote host           *
 165 *************************************************/
 166
 167 /* This function connects a socket to a remote address and port. The socket may
 168 or may not have previously been bound to a local interface. The socket is not
 169 closed, even in cases of error. It is expected that the calling function, which
 170 created the socket, will be the one that closes it.
 171
 172 Arguments:
 173   sock        the socket
 174   af          AF_INET6 or AF_INET for the socket type
 175   address     the remote address, in text form
 176   port        the remote port
 177   timeout     a timeout
 178
 179 Returns:      0 on success; -1 on failure, with errno set
 180 */
 181
 182 int
 183 ip_connect(int sock, int af, uschar *address, int port, int timeout)
 184 {
 185 struct sockaddr_in s_in4;
 186 struct sockaddr *s_ptr;
 187 int s_len, rc, save_errno;
 188
 189 /* For an IPv6 address, use an IPv6 sockaddr structure. */
 190
 191 #if HAVE_IPV6
 192 struct sockaddr_in6 s_in6;
 193 if (af == AF_INET6)
 194   {
 195   memset(&s_in6, 0, sizeof(s_in6));
 196   ip_addrinfo(address, &s_in6);   /* Panic-dies on error */
 197   s_in6.sin6_port = htons(port);
 198   s_ptr = (struct sockaddr *)&s_in6;
 199   s_len = sizeof(s_in6);
 200   }
 201 else
 202 #else     /* HAVE_IPV6 */
 203 af = af;  /* Avoid compiler warning */
 204 #endif    /* HAVE_IPV6 */
 205
 206 /* For an IPv4 address, use an IPv4 sockaddr structure, even on a system with
 207 IPv6 support. */
 208
 209   {
 210   memset(&s_in4, 0, sizeof(s_in4));
 211   s_in4.sin_family = AF_INET;
 212   s_in4.sin_port = htons(port);
 213   s_in4.sin_addr.s_addr = (S_ADDR_TYPE)inet_addr(CS address);
 214   s_ptr = (struct sockaddr *)&s_in4;
 215   s_len = sizeof(s_in4);
 216   }
 217
 218 /* If no connection timeout is set, just call connect() without setting a
 219 timer, thereby allowing the inbuilt OS timeout to operate. */
 220
 221 sigalrm_seen = FALSE;
 222 if (timeout > 0) alarm(timeout);
 223 rc = connect(sock, s_ptr, s_len);
 224 save_errno = errno;
 225 alarm(0);
 226
 227 /* There is a testing facility for simulating a connection timeout, as I
 228 can't think of any other way of doing this. It converts a connection refused
 229 into a timeout if the timeout is set to 999999. */
 230
 231 if (running_in_test_harness)
 232   {
 233   if (save_errno == ECONNREFUSED && timeout == 999999)
 234     {
 235     rc = -1;
 236     save_errno = EINTR;
 237     sigalrm_seen = TRUE;
 238     }
 239   }
 240
 241 /* Success */
 242
 243 if (rc >= 0) return 0;
 244
 245 /* A failure whose error code is "Interrupted system call" is in fact
 246 an externally applied timeout if the signal handler has been run. */
 247
 248 errno = (save_errno == EINTR && sigalrm_seen)? ETIMEDOUT : save_errno;
 249 return -1;
 250 }
 251
 252
 253
 254 /*************************************************
 255 *         Set keepalive on a socket              *
 256 *************************************************/
 257
 258 /* Can be called for both incoming and outgoing sockets.
 259
 260 Arguments:
 261   sock       the socket
 262   address    the remote host address, for failure logging
 263   torf       true for outgoing connection, false for incoming
 264
 265 Returns:     nothing
 266 */
 267
 268 void
 269 ip_keepalive(int sock, uschar *address, BOOL torf)
 270 {
 271 int fodder = 1;
 272 if (setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
 273     (uschar *)(&fodder), sizeof(fodder)) != 0)
 274   log_write(0, LOG_MAIN, "setsockopt(SO_KEEPALIVE) on connection %s %s "
 275     "failed: %s", torf? "to":"from", address, strerror(errno));
 276 }
 277
 278
 279
 280 /*************************************************
 281 *         Receive from a socket with timeout     *
 282 *************************************************/
 283
 284 /* The timeout is implemented using select(), and we loop to cover select()
 285 getting interrupted, and the possibility of select() returning with a positive
 286 result but no ready descriptor. Is this in fact possible?
 287
 288 Arguments:
 289   sock        the socket
 290   buffer      to read into
 291   bufsize     the buffer size
 292   timeout     the timeout
 293
 294 Returns:      > 0 => that much data read
 295               <= 0 on error or EOF; errno set - zero for EOF
 296 */
 297
 298 int
 299 ip_recv(int sock, uschar *buffer, int buffsize, int timeout)
 300 {
 301 fd_set select_inset;
 302 struct timeval tv;
 303 int start_recv = time(NULL);
 304 int rc;
 305
 306 /* Wait until the socket is ready */
 307
 308 for (;;)
 309   {
 310   FD_ZERO (&select_inset);
 311   FD_SET (sock, &select_inset);
 312   tv.tv_sec = timeout;
 313   tv.tv_usec = 0;
 314
 315   DEBUG(D_transport) debug_printf("waiting for data on socket\n");
 316   rc = select(sock + 1, (SELECT_ARG2_TYPE *)&select_inset, NULL, NULL, &tv);
 317
 318   /* If some interrupt arrived, just retry. We presume this to be rare,
 319   but it can happen (e.g. the SIGUSR1 signal sent by exiwhat causes
 320   select() to exit).
 321
 322   Aug 2004: Somebody set up a cron job that ran exiwhat every 2 minutes, making
 323   the interrupt not at all rare. Since the timeout is typically more than 2
 324   minutes, the effect was to block the timeout completely. To prevent this
 325   happening again, we do an explicit time test. */
 326
 327   if (rc < 0 && errno == EINTR)
 328     {
 329     DEBUG(D_transport) debug_printf("EINTR while waiting for socket data\n");
 330     if (time(NULL) - start_recv < timeout) continue;
 331     DEBUG(D_transport) debug_printf("total wait time exceeds timeout\n");
 332     }
 333
 334   /* Handle a timeout, and treat any other select error as a timeout, including
 335   an EINTR when we have been in this loop for longer than timeout. */
 336
 337   if (rc <= 0)
 338     {
 339     errno = ETIMEDOUT;
 340     return -1;
 341     }
 342
 343   /* If the socket is ready, break out of the loop. */
 344
 345   if (FD_ISSET(sock, &select_inset)) break;
 346   }
 347
 348 /* The socket is ready, read from it (via TLS if it's active). On EOF (i.e.
 349 close down of the connection), set errno to zero; otherwise leave it alone. */
 350
 351 #ifdef SUPPORT_TLS
 352 if (tls_active == sock)
 353   rc = tls_read(buffer, buffsize);
 354 else
 355 #endif
 356   rc = recv(sock, buffer, buffsize, 0);
 357
 358 if (rc > 0) return rc;
 359 if (rc == 0) errno = 0;
 360 return -1;
 361 }
 362
 363
 364 /* End of ip.c */