src/src/ip.c

   1 /* $Cambridge: exim/src/src/ip.c,v 1.5 2006/02/16 10:05:33 ph10 Exp $ */
   2
   3 /*************************************************
   4 *     Exim - an Internet mail transport agent    *
   5 *************************************************/
   6
   7 /* Copyright (c) University of Cambridge 1995 - 2006 */
   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.
 169
 170 Arguments:
 171   sock        the socket
 172   af          AF_INET6 or AF_INET for the socket type
 173   address     the remote address, in text form
 174   port        the remote port
 175   timeout     a timeout
 176
 177 Returns:      0 on success; -1 on failure, with errno set
 178 */
 179
 180 int
 181 ip_connect(int sock, int af, uschar *address, int port, int timeout)
 182 {
 183 struct sockaddr_in s_in4;
 184 struct sockaddr *s_ptr;
 185 int s_len, rc, save_errno;
 186
 187 /* For an IPv6 address, use an IPv6 sockaddr structure. */
 188
 189 #if HAVE_IPV6
 190 struct sockaddr_in6 s_in6;
 191 if (af == AF_INET6)
 192   {
 193   memset(&s_in6, 0, sizeof(s_in6));
 194   ip_addrinfo(address, &s_in6);   /* Panic-dies on error */
 195   s_in6.sin6_port = htons(port);
 196   s_ptr = (struct sockaddr *)&s_in6;
 197   s_len = sizeof(s_in6);
 198   }
 199 else
 200 #else     /* HAVE_IPV6 */
 201 af = af;  /* Avoid compiler warning */
 202 #endif    /* HAVE_IPV6 */
 203
 204 /* For an IPv4 address, use an IPv4 sockaddr structure, even on a system with
 205 IPv6 support. */
 206
 207   {
 208   memset(&s_in4, 0, sizeof(s_in4));
 209   s_in4.sin_family = AF_INET;
 210   s_in4.sin_port = htons(port);
 211   s_in4.sin_addr.s_addr = (S_ADDR_TYPE)inet_addr(CS address);
 212   s_ptr = (struct sockaddr *)&s_in4;
 213   s_len = sizeof(s_in4);
 214   }
 215
 216 /* If no connection timeout is set, just call connect() without setting a
 217 timer, thereby allowing the inbuilt OS timeout to operate. */
 218
 219 sigalrm_seen = FALSE;
 220 if (timeout > 0) alarm(timeout);
 221 rc = connect(sock, s_ptr, s_len);
 222 save_errno = errno;
 223 alarm(0);
 224
 225 /* There is a testing facility for simulating a connection timeout, as I
 226 can't think of any other way of doing this. It converts a connection refused
 227 into a timeout if the timeout is set to 999999. */
 228
 229 if (running_in_test_harness)
 230   {
 231   if (save_errno == ECONNREFUSED && timeout == 999999)
 232     {
 233     rc = -1;
 234     save_errno = EINTR;
 235     sigalrm_seen = TRUE;
 236     }
 237   }
 238
 239 /* Success */
 240
 241 if (rc >= 0) return 0;
 242
 243 /* A failure whose error code is "Interrupted system call" is in fact
 244 an externally applied timeout if the signal handler has been run. */
 245
 246 (void)close(sock);
 247 errno = (save_errno == EINTR && sigalrm_seen)? ETIMEDOUT : save_errno;
 248 return -1;
 249 }
 250
 251
 252
 253 /*************************************************
 254 *         Set keepalive on a socket              *
 255 *************************************************/
 256
 257 /* Can be called for both incoming and outgoing sockets.
 258
 259 Arguments:
 260   sock       the socket
 261   address    the remote host address, for failure logging
 262   torf       true for outgoing connection, false for incoming
 263
 264 Returns:     nothing
 265 */
 266
 267 void
 268 ip_keepalive(int sock, uschar *address, BOOL torf)
 269 {
 270 int fodder = 1;
 271 if (setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
 272     (uschar *)(&fodder), sizeof(fodder)) != 0)
 273   log_write(0, LOG_MAIN, "setsockopt(SO_KEEPALIVE) on connection %s %s "
 274     "failed: %s", torf? "to":"from", address, strerror(errno));
 275 }
 276
 277
 278
 279 /*************************************************
 280 *         Receive from a socket with timeout     *
 281 *************************************************/
 282
 283 /* The timeout is implemented using select(), and we loop to cover select()
 284 getting interrupted, and the possibility of select() returning with a positive
 285 result but no ready descriptor. Is this in fact possible?
 286
 287 Arguments:
 288   sock        the socket
 289   buffer      to read into
 290   bufsize     the buffer size
 291   timeout     the timeout
 292
 293 Returns:      > 0 => that much data read
 294               <= 0 on error or EOF; errno set - zero for EOF
 295 */
 296
 297 int
 298 ip_recv(int sock, uschar *buffer, int buffsize, int timeout)
 299 {
 300 fd_set select_inset;
 301 struct timeval tv;
 302 int start_recv = time(NULL);
 303 int rc;
 304
 305 /* Wait until the socket is ready */
 306
 307 for (;;)
 308   {
 309   FD_ZERO (&select_inset);
 310   FD_SET (sock, &select_inset);
 311   tv.tv_sec = timeout;
 312   tv.tv_usec = 0;
 313
 314   DEBUG(D_transport) debug_printf("waiting for data on socket\n");
 315   rc = select(sock + 1, (SELECT_ARG2_TYPE *)&select_inset, NULL, NULL, &tv);
 316
 317   /* If some interrupt arrived, just retry. We presume this to be rare,
 318   but it can happen (e.g. the SIGUSR1 signal sent by exiwhat causes
 319   select() to exit).
 320
 321   Aug 2004: Somebody set up a cron job that ran exiwhat every 2 minutes, making
 322   the interrupt not at all rare. Since the timeout is typically more than 2
 323   minutes, the effect was to block the timeout completely. To prevent this
 324   happening again, we do an explicit time test. */
 325
 326   if (rc < 0 && errno == EINTR)
 327     {
 328     DEBUG(D_transport) debug_printf("EINTR while waiting for socket data\n");
 329     if (time(NULL) - start_recv < timeout) continue;
 330     DEBUG(D_transport) debug_printf("total wait time exceeds timeout\n");
 331     }
 332
 333   /* Handle a timeout, and treat any other select error as a timeout, including
 334   an EINTR when we have been in this loop for longer than timeout. */
 335
 336   if (rc <= 0)
 337     {
 338     errno = ETIMEDOUT;
 339     return -1;
 340     }
 341
 342   /* If the socket is ready, break out of the loop. */
 343
 344   if (FD_ISSET(sock, &select_inset)) break;
 345   }
 346
 347 /* The socket is ready, read from it (via TLS if it's active). On EOF (i.e.
 348 close down of the connection), set errno to zero; otherwise leave it alone. */
 349
 350 #ifdef SUPPORT_TLS
 351 if (tls_active == sock)
 352   rc = tls_read(buffer, buffsize);
 353 else
 354 #endif
 355   rc = recv(sock, buffer, buffsize, 0);
 356
 357 if (rc > 0) return rc;
 358 if (rc == 0) errno = 0;
 359 return -1;
 360 }
 361
 362
 363 /* End of ip.c */