src/src/ip.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2014 */
   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 (zero for indefinite 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 /* Create a socket and connect to host (name or number, ipv6 ok)
 252    at one of port-range.
 253 Arguments:
 254   type          SOCK_DGRAM or SOCK_STREAM
 255   af            AF_INET6 or AF_INET for the socket type
 256   address       the remote address, in text form
 257   portlo,porthi the remote port range
 258   timeout       a timeout
 259   connhost      if not NULL, host_item filled in with connection details
 260   errstr        pointer for allocated string on error
 261
 262 Return:
 263   socket fd, or -1 on failure (having allocated an error string)
 264 */
 265 int
 266 ip_connectedsocket(int type, const uschar * hostname, int portlo, int porthi,
 267         int timeout, host_item * connhost, uschar ** errstr)
 268 {
 269 int namelen, port;
 270 host_item shost;
 271 host_item *h;
 272 int af = 0, fd, fd4 = -1, fd6 = -1;
 273
 274 shost.next = NULL;
 275 shost.address = NULL;
 276 shost.port = portlo;
 277 shost.mx = -1;
 278
 279 namelen = Ustrlen(hostname);
 280
 281 /* Anything enclosed in [] must be an IP address. */
 282
 283 if (hostname[0] == '[' &&
 284     hostname[namelen - 1] == ']')
 285   {
 286   uschar * host = string_copy(hostname);
 287   host[namelen - 1] = 0;
 288   host++;
 289   if (string_is_ip_address(host, NULL) == 0)
 290     {
 291     *errstr = string_sprintf("malformed IP address \"%s\"", hostname);
 292     return -1;
 293     }
 294   shost.name = shost.address = host;
 295   }
 296
 297 /* Otherwise check for an unadorned IP address */
 298
 299 else if (string_is_ip_address(hostname, NULL) != 0)
 300   shost.name = shost.address = string_copy(hostname);
 301
 302 /* Otherwise lookup IP address(es) from the name */
 303
 304 else
 305   {
 306   shost.name = string_copy(hostname);
 307   if (host_find_byname(&shost, NULL, HOST_FIND_QUALIFY_SINGLE, NULL,
 308       FALSE) != HOST_FOUND)
 309     {
 310     *errstr = string_sprintf("no IP address found for host %s", shost.name);
 311     return -1;
 312     }
 313   }
 314
 315 /* Try to connect to the server - test each IP till one works */
 316
 317 for (h = &shost; h != NULL; h = h->next)
 318   {
 319   fd = (Ustrchr(h->address, ':') != 0)
 320     ? (fd6 < 0) ? (fd6 = ip_socket(SOCK_STREAM, af = AF_INET6)) : fd6
 321     : (fd4 < 0) ? (fd4 = ip_socket(SOCK_STREAM, af = AF_INET )) : fd4;
 322
 323   if (fd < 0)
 324     {
 325     *errstr = string_sprintf("failed to create socket: %s", strerror(errno));
 326     goto bad;
 327     }
 328
 329   for(port = portlo; port <= porthi; port++)
 330     if (ip_connect(fd, af, h->address, port, timeout) == 0)
 331       {
 332       if (fd != fd6) close(fd6);
 333       if (fd != fd4) close(fd4);
 334       if (connhost) {
 335         h->port = port;
 336         *connhost = *h;
 337         connhost->next = NULL;
 338         }
 339       return fd;
 340       }
 341   }
 342
 343 *errstr = string_sprintf("failed to connect to "
 344   "%s: couldn't connect to any host", hostname, strerror(errno));
 345
 346 bad:
 347   close(fd4); close(fd6); return -1;
 348 }
 349
 350
 351 /*************************************************
 352 *         Set keepalive on a socket              *
 353 *************************************************/
 354
 355 /* Can be called for both incoming and outgoing sockets.
 356
 357 Arguments:
 358   sock       the socket
 359   address    the remote host address, for failure logging
 360   torf       true for outgoing connection, false for incoming
 361
 362 Returns:     nothing
 363 */
 364
 365 void
 366 ip_keepalive(int sock, uschar *address, BOOL torf)
 367 {
 368 int fodder = 1;
 369 if (setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE,
 370     (uschar *)(&fodder), sizeof(fodder)) != 0)
 371   log_write(0, LOG_MAIN, "setsockopt(SO_KEEPALIVE) on connection %s %s "
 372     "failed: %s", torf? "to":"from", address, strerror(errno));
 373 }
 374
 375
 376
 377 /*************************************************
 378 *         Receive from a socket with timeout     *
 379 *************************************************/
 380
 381 /* The timeout is implemented using select(), and we loop to cover select()
 382 getting interrupted, and the possibility of select() returning with a positive
 383 result but no ready descriptor. Is this in fact possible?
 384
 385 Arguments:
 386   sock        the socket
 387   buffer      to read into
 388   bufsize     the buffer size
 389   timeout     the timeout
 390
 391 Returns:      > 0 => that much data read
 392               <= 0 on error or EOF; errno set - zero for EOF
 393 */
 394
 395 int
 396 ip_recv(int sock, uschar *buffer, int buffsize, int timeout)
 397 {
 398 fd_set select_inset;
 399 struct timeval tv;
 400 int start_recv = time(NULL);
 401 int rc;
 402
 403 /* Wait until the socket is ready */
 404
 405 for (;;)
 406   {
 407   FD_ZERO (&select_inset);
 408   FD_SET (sock, &select_inset);
 409   tv.tv_sec = timeout;
 410   tv.tv_usec = 0;
 411
 412   DEBUG(D_transport) debug_printf("waiting for data on socket\n");
 413   rc = select(sock + 1, (SELECT_ARG2_TYPE *)&select_inset, NULL, NULL, &tv);
 414
 415   /* If some interrupt arrived, just retry. We presume this to be rare,
 416   but it can happen (e.g. the SIGUSR1 signal sent by exiwhat causes
 417   select() to exit).
 418
 419   Aug 2004: Somebody set up a cron job that ran exiwhat every 2 minutes, making
 420   the interrupt not at all rare. Since the timeout is typically more than 2
 421   minutes, the effect was to block the timeout completely. To prevent this
 422   happening again, we do an explicit time test. */
 423
 424   if (rc < 0 && errno == EINTR)
 425     {
 426     DEBUG(D_transport) debug_printf("EINTR while waiting for socket data\n");
 427     if (time(NULL) - start_recv < timeout) continue;
 428     DEBUG(D_transport) debug_printf("total wait time exceeds timeout\n");
 429     }
 430
 431   /* Handle a timeout, and treat any other select error as a timeout, including
 432   an EINTR when we have been in this loop for longer than timeout. */
 433
 434   if (rc <= 0)
 435     {
 436     errno = ETIMEDOUT;
 437     return -1;
 438     }
 439
 440   /* If the socket is ready, break out of the loop. */
 441
 442   if (FD_ISSET(sock, &select_inset)) break;
 443   }
 444
 445 /* The socket is ready, read from it (via TLS if it's active). On EOF (i.e.
 446 close down of the connection), set errno to zero; otherwise leave it alone. */
 447
 448 #ifdef SUPPORT_TLS
 449 if (tls_out.active == sock)
 450   rc = tls_read(FALSE, buffer, buffsize);
 451 else if (tls_in.active == sock)
 452   rc = tls_read(TRUE, buffer, buffsize);
 453 else
 454 #endif
 455   rc = recv(sock, buffer, buffsize, 0);
 456
 457 if (rc > 0) return rc;
 458 if (rc == 0) errno = 0;
 459 return -1;
 460 }
 461
 462
 463
 464
 465 /*************************************************
 466 *    Lookup address family of potential socket   *
 467 *************************************************/
 468
 469 /* Given a file-descriptor, check to see if it's a socket and, if so,
 470 return the address family; detects IPv4 vs IPv6.  If not a socket then
 471 return -1.
 472
 473 The value 0 is typically AF_UNSPEC, which should not be seen on a connected
 474 fd.  If the return is -1, the errno will be from getsockname(); probably
 475 ENOTSOCK or ECONNRESET.
 476
 477 Arguments:     socket-or-not fd
 478 Returns:       address family or -1
 479 */
 480
 481 int
 482 ip_get_address_family(int fd)
 483 {
 484 struct sockaddr_storage ss;
 485 socklen_t sslen = sizeof(ss);
 486
 487 if (getsockname(fd, (struct sockaddr *) &ss, &sslen) < 0)
 488   return -1;
 489
 490 return (int) ss.ss_family;
 491 }
 492
 493
 494
 495
 496 /*************************************************
 497 *       Lookup DSCP settings for a socket        *
 498 *************************************************/
 499
 500 struct dscp_name_tableentry {
 501   const uschar *name;
 502   int value;
 503 };
 504 /* Keep both of these tables sorted! */
 505 static struct dscp_name_tableentry dscp_table[] = {
 506 #ifdef IPTOS_DSCP_AF11
 507     { CUS"af11", IPTOS_DSCP_AF11 },
 508     { CUS"af12", IPTOS_DSCP_AF12 },
 509     { CUS"af13", IPTOS_DSCP_AF13 },
 510     { CUS"af21", IPTOS_DSCP_AF21 },
 511     { CUS"af22", IPTOS_DSCP_AF22 },
 512     { CUS"af23", IPTOS_DSCP_AF23 },
 513     { CUS"af31", IPTOS_DSCP_AF31 },
 514     { CUS"af32", IPTOS_DSCP_AF32 },
 515     { CUS"af33", IPTOS_DSCP_AF33 },
 516     { CUS"af41", IPTOS_DSCP_AF41 },
 517     { CUS"af42", IPTOS_DSCP_AF42 },
 518     { CUS"af43", IPTOS_DSCP_AF43 },
 519     { CUS"ef", IPTOS_DSCP_EF },
 520 #endif
 521 #ifdef IPTOS_LOWCOST
 522     { CUS"lowcost", IPTOS_LOWCOST },
 523 #endif
 524     { CUS"lowdelay", IPTOS_LOWDELAY },
 525 #ifdef IPTOS_MINCOST
 526     { CUS"mincost", IPTOS_MINCOST },
 527 #endif
 528     { CUS"reliability", IPTOS_RELIABILITY },
 529     { CUS"throughput", IPTOS_THROUGHPUT }
 530 };
 531 static int dscp_table_size =
 532   sizeof(dscp_table) / sizeof(struct dscp_name_tableentry);
 533
 534 /* DSCP values change by protocol family, and so do the options used for
 535 setsockopt(); this utility does all the lookups.  It takes an unexpanded
 536 option string, expands it, strips off affix whitespace, then checks if it's
 537 a number.  If all of what's left is a number, then that's how the option will
 538 be parsed and success/failure is a range check.  If it's not all a number,
 539 then it must be a supported keyword.
 540
 541 Arguments:
 542   dscp_name   a string, so far unvalidated
 543   af          address_family in use
 544   level       setsockopt level to use
 545   optname     setsockopt name to use
 546   dscp_value  value for dscp_name
 547
 548 Returns: TRUE if okay to setsockopt(), else FALSE
 549
 550 *level and *optname may be set even if FALSE is returned
 551 */
 552
 553 BOOL
 554 dscp_lookup(const uschar *dscp_name, int af,
 555     int *level, int *optname, int *dscp_value)
 556 {
 557 uschar *dscp_lookup, *p;
 558 int first, last;
 559 long rawlong;
 560
 561 if (af == AF_INET)
 562   {
 563   *level = IPPROTO_IP;
 564   *optname = IP_TOS;
 565   }
 566 #if HAVE_IPV6 && defined(IPV6_TCLASS)
 567 else if (af == AF_INET6)
 568   {
 569   *level = IPPROTO_IPV6;
 570   *optname = IPV6_TCLASS;
 571   }
 572 #endif
 573 else
 574   {
 575   DEBUG(D_transport)
 576     debug_printf("Unhandled address family %d in dscp_lookup()\n", af);
 577   return FALSE;
 578   }
 579 if (!dscp_name)
 580   {
 581   DEBUG(D_transport)
 582     debug_printf("[empty DSCP]\n");
 583   return FALSE;
 584   }
 585 dscp_lookup = expand_string(US dscp_name);
 586 if (dscp_lookup == NULL || *dscp_lookup == '\0')
 587   return FALSE;
 588
 589 p = dscp_lookup + Ustrlen(dscp_lookup) - 1;
 590 while (isspace(*p)) *p-- = '\0';
 591 while (isspace(*dscp_lookup) && dscp_lookup < p) dscp_lookup++;
 592 if (*dscp_lookup == '\0')
 593   return FALSE;
 594
 595 rawlong = Ustrtol(dscp_lookup, &p, 0);
 596 if (p != dscp_lookup && *p == '\0')
 597   {
 598   /* We have six bits available, which will end up shifted to fit in 0xFC mask.
 599   RFC 2597 defines the values unshifted. */
 600   if (rawlong < 0 || rawlong > 0x3F)
 601     {
 602     DEBUG(D_transport)
 603       debug_printf("DSCP value %ld out of range, ignored.\n", rawlong);
 604     return FALSE;
 605     }
 606   *dscp_value = rawlong << 2;
 607   return TRUE;
 608   }
 609
 610 first = 0;
 611 last = dscp_table_size;
 612 while (last > first)
 613   {
 614   int middle = (first + last)/2;
 615   int c = Ustrcmp(dscp_lookup, dscp_table[middle].name);
 616   if (c == 0)
 617     {
 618     *dscp_value = dscp_table[middle].value;
 619     return TRUE;
 620     }
 621   else if (c > 0)
 622     {
 623     first = middle + 1;
 624     }
 625   else
 626     {
 627     last = middle;
 628     }
 629   }
 630 return FALSE;
 631 }
 632
 633 void
 634 dscp_list_to_stream(FILE *stream)
 635 {
 636 int i;
 637 for (i=0; i < dscp_table_size; ++i)
 638   fprintf(stream, "%s\n", dscp_table[i].name);
 639 }
 640
 641
 642 /* End of ip.c */