src/src/ip.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2009 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 /* Functions for doing things with sockets. With the advent of IPv6 this has
   9 got messier, so that it's worth pulling out the code into separate functions
  10 that other parts of Exim can call, expecially as there are now several
  11 different places in the code where sockets are used. */
  12
  13
  14 #include "exim.h"
  15
  16
  17 /*************************************************
  18 *             Create a socket                    *
  19 *************************************************/
  20
  21 /* Socket creation happens in a number of places so it's packaged here for
  22 convenience.
  23
  24 Arguments:
  25   type       SOCK_DGRAM or SOCK_STREAM
  26   af         AF_INET or AF_INET6
  27
  28 Returns:     socket number or -1 on failure
  29 */
  30
  31 int
  32 ip_socket(int type, int af)
  33 {
  34 int sock = socket(af, type, 0);
  35 if (sock < 0)
  36   log_write(0, LOG_MAIN, "IPv%c socket creation failed: %s",
  37     (af == AF_INET6)? '6':'4', strerror(errno));
  38 return sock;
  39 }
  40
  41
  42
  43
  44 #if HAVE_IPV6
  45 /*************************************************
  46 *      Convert printing address to numeric       *
  47 *************************************************/
  48
  49 /* This function converts the textual form of an IP address into a numeric form
  50 in an appropriate structure in an IPv6 environment. The getaddrinfo() function
  51 can (apparently) handle more complicated addresses (e.g. those containing
  52 scopes) than inet_pton() in some environments. We use hints to tell it that the
  53 input must be a numeric address.
  54
  55 However, apparently some operating systems (or libraries) don't support
  56 getaddrinfo(), so there is a build-time option to revert to inet_pton() (which
  57 does not support scopes).
  58
  59 Arguments:
  60   address     textual form of the address
  61   addr        where to copy back the answer
  62
  63 Returns:      nothing - failure provokes a panic-die
  64 */
  65
  66 static void
  67 ip_addrinfo(uschar *address, struct sockaddr_in6 *saddr)
  68 {
  69 #ifdef IPV6_USE_INET_PTON
  70
  71   if (inet_pton(AF_INET6, CS address, &saddr->sin6_addr) != 1)
  72     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "unable to parse \"%s\" as an "
  73       "IP address", address);
  74   saddr->sin6_family = AF_INET6;
  75
  76 #else
  77
  78   int rc;
  79   struct addrinfo hints, *res;
  80   memset(&hints, 0, sizeof(hints));
  81   hints.ai_family = AF_INET6;
  82   hints.ai_socktype = SOCK_STREAM;
  83   hints.ai_flags = AI_NUMERICHOST;
  84   if ((rc = getaddrinfo(CS address, NULL, &hints, &res)) != 0 || res == NULL)
  85     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "unable to parse \"%s\" as an "
  86       "IP address: %s", address,
  87       (rc == 0)? "NULL result returned" : gai_strerror(rc));
  88   memcpy(saddr, res->ai_addr, res->ai_addrlen);
  89   freeaddrinfo(res);
  90
  91 #endif
  92 }
  93 #endif  /* HAVE_IPV6 */
  94
  95
  96 /*************************************************
  97 *         Bind socket to interface and port      *
  98 *************************************************/
  99
 100 /* This function binds a socket to a local interface address and port. For a
 101 wildcard IPv6 bind, the address is ":".
 102
 103 Arguments:
 104   sock           the socket
 105   af             AF_INET or AF_INET6 - the socket type
 106   address        the IP address, in text form
 107   port           the IP port (host order)
 108
 109 Returns:         the result of bind()
 110 */
 111
 112 int
 113 ip_bind(int sock, int af, uschar *address, int port)
 114 {
 115 int s_len;
 116 union sockaddr_46 sin;
 117 memset(&sin, 0, sizeof(sin));
 118
 119 /* Setup code when using an IPv6 socket. The wildcard address is ":", to
 120 ensure an IPv6 socket is used. */
 121
 122 #if HAVE_IPV6
 123 if (af == AF_INET6)
 124   {
 125   if (address[0] == ':' && address[1] == 0)
 126     {
 127     sin.v6.sin6_family = AF_INET6;
 128     sin.v6.sin6_addr = in6addr_any;
 129     }
 130   else
 131     {
 132     ip_addrinfo(address, &sin.v6);  /* Panic-dies on error */
 133     }
 134   sin.v6.sin6_port = htons(port);
 135   s_len = sizeof(sin.v6);
 136   }
 137 else
 138 #else     /* HAVE_IPv6 */
 139 af = af;  /* Avoid compiler warning */
 140 #endif    /* HAVE_IPV6 */
 141
 142 /* Setup code when using IPv4 socket. The wildcard address is "". */
 143
 144   {
 145   sin.v4.sin_family = AF_INET;
 146   sin.v4.sin_port = htons(port);
 147   s_len = sizeof(sin.v4);
 148   if (address[0] == 0)
 149     sin.v4.sin_addr.s_addr = (S_ADDR_TYPE)INADDR_ANY;
 150   else
 151     sin.v4.sin_addr.s_addr = (S_ADDR_TYPE)inet_addr(CS address);
 152   }
 153
 154 /* Now we can call the bind() function */
 155
 156 return bind(sock, (struct sockaddr *)&sin, s_len);
 157 }
 158
 159
 160
 161 /*************************************************
 162 *        Connect socket to remote host           *
 163 *************************************************/
 164
 165 /* This function connects a socket to a remote address and port. The socket may
 166 or may not have previously been bound to a local interface. The socket is not
 167 closed, even in cases of error. It is expected that the calling function, which
 168 created the socket, will be the one that closes it.
 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 errno = (save_errno == EINTR && sigalrm_seen)? ETIMEDOUT : save_errno;
 247 return -1;
 248 }
 249
 250
 251
 252 /*************************************************
 253 *         Set keepalive on a socket              *
 254 *************************************************/
 255
 256 /* Can be called for both incoming and outgoing sockets.
 257
 258 Arguments:
 259   sock       the socket
 260   address    the remote host address, for failure logging
 261   torf       true for outgoing connection, false for incoming
 262
 263 Returns:     nothing
 264 */
 265
 266 void
 267 ip_keepalive(int sock, uschar *address, BOOL torf)
 268 {
 269 int fodder = 1;
 270 if (setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
 271     (uschar *)(&fodder), sizeof(fodder)) != 0)
 272   log_write(0, LOG_MAIN, "setsockopt(SO_KEEPALIVE) on connection %s %s "
 273     "failed: %s", torf? "to":"from", address, strerror(errno));
 274 }
 275
 276
 277
 278 /*************************************************
 279 *         Receive from a socket with timeout     *
 280 *************************************************/
 281
 282 /* The timeout is implemented using select(), and we loop to cover select()
 283 getting interrupted, and the possibility of select() returning with a positive
 284 result but no ready descriptor. Is this in fact possible?
 285
 286 Arguments:
 287   sock        the socket
 288   buffer      to read into
 289   bufsize     the buffer size
 290   timeout     the timeout
 291
 292 Returns:      > 0 => that much data read
 293               <= 0 on error or EOF; errno set - zero for EOF
 294 */
 295
 296 int
 297 ip_recv(int sock, uschar *buffer, int buffsize, int timeout)
 298 {
 299 fd_set select_inset;
 300 struct timeval tv;
 301 int start_recv = time(NULL);
 302 int rc;
 303
 304 /* Wait until the socket is ready */
 305
 306 for (;;)
 307   {
 308   FD_ZERO (&select_inset);
 309   FD_SET (sock, &select_inset);
 310   tv.tv_sec = timeout;
 311   tv.tv_usec = 0;
 312
 313   DEBUG(D_transport) debug_printf("waiting for data on socket\n");
 314   rc = select(sock + 1, (SELECT_ARG2_TYPE *)&select_inset, NULL, NULL, &tv);
 315
 316   /* If some interrupt arrived, just retry. We presume this to be rare,
 317   but it can happen (e.g. the SIGUSR1 signal sent by exiwhat causes
 318   select() to exit).
 319
 320   Aug 2004: Somebody set up a cron job that ran exiwhat every 2 minutes, making
 321   the interrupt not at all rare. Since the timeout is typically more than 2
 322   minutes, the effect was to block the timeout completely. To prevent this
 323   happening again, we do an explicit time test. */
 324
 325   if (rc < 0 && errno == EINTR)
 326     {
 327     DEBUG(D_transport) debug_printf("EINTR while waiting for socket data\n");
 328     if (time(NULL) - start_recv < timeout) continue;
 329     DEBUG(D_transport) debug_printf("total wait time exceeds timeout\n");
 330     }
 331
 332   /* Handle a timeout, and treat any other select error as a timeout, including
 333   an EINTR when we have been in this loop for longer than timeout. */
 334
 335   if (rc <= 0)
 336     {
 337     errno = ETIMEDOUT;
 338     return -1;
 339     }
 340
 341   /* If the socket is ready, break out of the loop. */
 342
 343   if (FD_ISSET(sock, &select_inset)) break;
 344   }
 345
 346 /* The socket is ready, read from it (via TLS if it's active). On EOF (i.e.
 347 close down of the connection), set errno to zero; otherwise leave it alone. */
 348
 349 #ifdef SUPPORT_TLS
 350 if (tls_active == sock)
 351   rc = tls_read(buffer, buffsize);
 352 else
 353 #endif
 354   rc = recv(sock, buffer, buffsize, 0);
 355
 356 if (rc > 0) return rc;
 357 if (rc == 0) errno = 0;
 358 return -1;
 359 }
 360
 361
 362 /* End of ip.c */