socket.c

   1 /* -*- c-file-style: "linux" -*-
   2
   3    rsync -- fast file replication program
   4
   5    Copyright (C) 1992-2001 by Andrew Tridgell <tridge@samba.org>
   6    Copyright (C) 2001, 2002 by Martin Pool <mbp@samba.org>
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23 /**
  24  * @file socket.c
  25  *
  26  * Socket functions used in rsync.
  27  *
  28  * This file is now converted to use the new-style getaddrinfo()
  29  * interface, which supports IPv6 but is also supported on recent
  30  * IPv4-only machines.  On systems that don't have that interface, we
  31  * emulate it using the KAME implementation.
  32  **/
  33
  34 #include "rsync.h"
  35
  36
  37 /**
  38  * Establish a proxy connection on an open socket to a web proxy by
  39  * using the HTTP CONNECT method.
  40  **/
  41 static int establish_proxy_connection(int fd, char *host, int port)
  42 {
  43         char buffer[1024];
  44         char *cp;
  45
  46         snprintf(buffer, sizeof(buffer), "CONNECT %s:%d HTTP/1.0\r\n\r\n", host, port);
  47         if (write(fd, buffer, strlen(buffer)) != (int) strlen(buffer)) {
  48                 rprintf(FERROR, "failed to write to proxy: %s\n",
  49                         strerror(errno));
  50                 return -1;
  51         }
  52
  53         for (cp = buffer; cp < &buffer[sizeof(buffer) - 1]; cp++) {
  54                 if (read(fd, cp, 1) != 1) {
  55                         rprintf(FERROR, "failed to read from proxy: %s\n",
  56                                 strerror(errno));
  57                         return -1;
  58                 }
  59                 if (*cp == '\n')
  60                         break;
  61         }
  62
  63         if (*cp != '\n')
  64                 cp++;
  65         *cp-- = '\0';
  66         if (*cp == '\r')
  67                 *cp = '\0';
  68         if (strncmp(buffer, "HTTP/", 5) != 0) {
  69                 rprintf(FERROR, "bad response from proxy - %s\n",
  70                         buffer);
  71                 return -1;
  72         }
  73         for (cp = &buffer[5]; isdigit(* (unsigned char *) cp) || (*cp == '.'); cp++)
  74                 ;
  75         while (*cp == ' ')
  76                 cp++;
  77         if (*cp != '2') {
  78                 rprintf(FERROR, "bad response from proxy - %s\n",
  79                         buffer);
  80                 return -1;
  81         }
  82         /* throw away the rest of the HTTP header */
  83         while (1) {
  84                 for (cp = buffer; cp < &buffer[sizeof(buffer) - 1];
  85                      cp++) {
  86                         if (read(fd, cp, 1) != 1) {
  87                                 rprintf(FERROR, "failed to read from proxy: %s\n",
  88                                         strerror(errno));
  89                                 return -1;
  90                         }
  91                         if (*cp == '\n')
  92                                 break;
  93                 }
  94                 if ((cp > buffer) && (*cp == '\n'))
  95                         cp--;
  96                 if ((cp == buffer) && ((*cp == '\n') || (*cp == '\r')))
  97                         break;
  98         }
  99         return 0;
 100 }
 101
 102
 103 /**
 104  * Try to set the local address for a newly-created socket.  Return -1
 105  * if this fails.
 106  **/
 107 int try_bind_local(int s,
 108                    int ai_family, int ai_socktype,
 109                    const char *bind_address)
 110 {
 111         int error;
 112         struct addrinfo bhints, *bres_all, *r;
 113
 114         memset(&bhints, 0, sizeof(bhints));
 115         bhints.ai_family = ai_family;
 116         bhints.ai_socktype = ai_socktype;
 117         bhints.ai_flags = AI_PASSIVE;
 118         if ((error = getaddrinfo(bind_address, NULL, &bhints, &bres_all))) {
 119                 rprintf(FERROR, RSYNC_NAME ": getaddrinfo %s: %s\n",
 120                         bind_address, gai_strerror(error));
 121                 return -1;
 122         }
 123
 124         for (r = bres_all; r; r = r->ai_next) {
 125                 if (bind(s, r->ai_addr, r->ai_addrlen) == -1)
 126                         continue;
 127                 freeaddrinfo(bres_all);
 128                 return s;
 129         }
 130
 131         /* no error message; there might be some problem that allows
 132          * creation of the socket but not binding, perhaps if the
 133          * machine has no ipv6 address of this name. */
 134         freeaddrinfo(bres_all);
 135         return -1;
 136 }
 137
 138
 139 /**
 140  * Open a socket to a tcp remote host with the specified port .
 141  *
 142  * Based on code from Warren.  Proxy support by Stephen Rothwell.
 143  * getaddrinfo() rewrite contributed by KAME.net.
 144  *
 145  * Now that we support IPv6 we need to look up the remote machine's
 146  * address first, using @p af_hint to set a preference for the type
 147  * of address.  Then depending on whether it has v4 or v6 addresses we
 148  * try to open a connection.
 149  *
 150  * The loop allows for machines with some addresses which may not be
 151  * reachable, perhaps because we can't e.g. route ipv6 to that network
 152  * but we can get ip4 packets through.
 153  *
 154  * @param bind_address Local address to use.  Normally NULL to bind
 155  * the wildcard address.
 156  *
 157  * @param af_hint Address family, e.g. AF_INET or AF_INET6.
 158  **/
 159 int open_socket_out(char *host, int port, const char *bind_address,
 160                     int af_hint)
 161 {
 162         int type = SOCK_STREAM;
 163         int error;
 164         int s;
 165         struct addrinfo hints, *res0, *res;
 166         char portbuf[10];
 167         char *h;
 168         int proxied = 0;
 169         char buffer[1024];
 170         char *cp;
 171
 172         /* if we have a RSYNC_PROXY env variable then redirect our
 173          * connetcion via a web proxy at the given address. The format
 174          * is hostname:port */
 175         h = getenv("RSYNC_PROXY");
 176         proxied = (h != NULL) && (*h != '\0');
 177
 178         if (proxied) {
 179                 strlcpy(buffer, h, sizeof(buffer));
 180                 cp = strchr(buffer, ':');
 181                 if (cp == NULL) {
 182                         rprintf(FERROR,
 183                                 "invalid proxy specification: should be HOST:PORT\n");
 184                         return -1;
 185                 }
 186                 *cp++ = '\0';
 187                 strcpy(portbuf, cp);
 188                 h = buffer;
 189                 if (verbose >= 2) {
 190                         rprintf(FINFO, "connection via http proxy %s port %s\n",
 191                                 h, portbuf);
 192                 }
 193         } else {
 194                 snprintf(portbuf, sizeof(portbuf), "%d", port);
 195                 h = host;
 196         }
 197
 198         memset(&hints, 0, sizeof(hints));
 199         hints.ai_family = af_hint;
 200         hints.ai_socktype = type;
 201         error = getaddrinfo(h, portbuf, &hints, &res0);
 202         if (error) {
 203                 rprintf(FERROR, RSYNC_NAME ": getaddrinfo: %s %s: %s\n",
 204                         h, portbuf, gai_strerror(error));
 205                 return -1;
 206         }
 207
 208         s = -1;
 209         /* Try to connect to all addresses for this machine until we get
 210          * through.  It might e.g. be multi-homed, or have both IPv4 and IPv6
 211          * addresses.  We need to create a socket for each record, since the
 212          * address record tells us what protocol to use to try to connect. */
 213         for (res = res0; res; res = res->ai_next) {
 214                 s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
 215                 if (s < 0)
 216                         continue;
 217
 218                 if (bind_address)
 219                         if (try_bind_local(s, res->ai_family, type,
 220                                            bind_address) == -1) {
 221                                 close(s);
 222                                 s = -1;
 223                                 continue;
 224                         }
 225
 226                 if (connect(s, res->ai_addr, res->ai_addrlen) < 0) {
 227                         close(s);
 228                         s = -1;
 229                         continue;
 230                 }
 231                 if (proxied &&
 232                     establish_proxy_connection(s, host, port) != 0) {
 233                         close(s);
 234                         s = -1;
 235                         continue;
 236                 } else
 237                         break;
 238         }
 239         freeaddrinfo(res0);
 240         if (s < 0) {
 241                 rprintf(FERROR, RSYNC_NAME ": failed to connect to %s: %s\n",
 242                         h, strerror(errno));
 243                 return -1;
 244         }
 245         return s;
 246 }
 247
 248
 249 /**
 250  * Open an outgoing socket, but allow for it to be intercepted by
 251  * $RSYNC_CONNECT_PROG, which will execute a program across a TCP
 252  * socketpair rather than really opening a socket.
 253  *
 254  * We use this primarily in testing to detect TCP flow bugs, but not
 255  * cause security problems by really opening remote connections.
 256  *
 257  * This is based on the Samba LIBSMB_PROG feature.
 258  *
 259  * @param bind_address Local address to use.  Normally NULL to get the stack default.
 260  **/
 261 int open_socket_out_wrapped (char *host,
 262                              int port,
 263                              const char *bind_address,
 264                              int af_hint)
 265 {
 266         char *prog;
 267
 268         if ((prog = getenv ("RSYNC_CONNECT_PROG")) != NULL)
 269                 return sock_exec (prog);
 270         else
 271                 return open_socket_out (host, port, bind_address,
 272                                         af_hint);
 273 }
 274
 275
 276
 277 /**
 278  * Open a socket of the specified type, port and address for incoming data
 279  *
 280  * Try to be better about handling the results of getaddrinfo(): when
 281  * opening an inbound socket, we might get several address results,
 282  * e.g. for the machine's ipv4 and ipv6 name.
 283  *
 284  * If binding a wildcard, then any one of them should do.  If an address
 285  * was specified but it's insufficiently specific then that's not our
 286  * fault.
 287  *
 288  * However, some of the advertized addresses may not work because e.g. we
 289  * don't have IPv6 support in the kernel.  In that case go on and try all
 290  * addresses until one succeeds.
 291  *
 292  * @param bind_address Local address to bind, or NULL to allow it to
 293  * default.
 294  **/
 295 static int open_socket_in(int type, int port, const char *bind_address,
 296                           int af_hint)
 297 {
 298         int one=1;
 299         int s;
 300         struct addrinfo hints, *all_ai, *resp;
 301         char portbuf[10];
 302         int error;
 303
 304         memset(&hints, 0, sizeof(hints));
 305         hints.ai_family = af_hint;
 306         hints.ai_socktype = type;
 307         hints.ai_flags = AI_PASSIVE;
 308         snprintf(portbuf, sizeof(portbuf), "%d", port);
 309         error = getaddrinfo(bind_address, portbuf, &hints, &all_ai);
 310         if (error) {
 311                 rprintf(FERROR, RSYNC_NAME ": getaddrinfo: bind address %s: %s\n",
 312                         bind_address, gai_strerror(error));
 313                 return -1;
 314         }
 315
 316         /* We may not be able to create the socket, if for example the
 317          * machine knows about IPv6 in the C library, but not in the
 318          * kernel. */
 319         for (resp = all_ai; resp; resp = resp->ai_next) {
 320                 s = socket(resp->ai_family, resp->ai_socktype,
 321                            resp->ai_protocol);
 322
 323                 if (s == -1)
 324                         /* See if there's another address that will work... */
 325                         continue;
 326
 327                 setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
 328                            (char *)&one, sizeof one);
 329
 330                 /* now we've got a socket - we need to bind it */
 331                 if (bind(s, all_ai->ai_addr, all_ai->ai_addrlen) < 0) {
 332                         /* Nope, try another */
 333                         close(s);
 334                         continue;
 335                 }
 336
 337                 freeaddrinfo(all_ai);
 338                 return s;
 339         }
 340
 341         rprintf(FERROR, RSYNC_NAME ": open inbound socket on port %d failed: "
 342                 "%s\n",
 343                 port,
 344                 strerror(errno));
 345
 346         freeaddrinfo(all_ai);
 347         return -1;
 348 }
 349
 350
 351 /*
 352  * Determine if a file descriptor is in fact a socket
 353  */
 354 int is_a_socket(int fd)
 355 {
 356         int v;
 357         socklen_t l;
 358         l = sizeof(int);
 359
 360         /* Parameters to getsockopt, setsockopt etc are very
 361          * unstandardized across platforms, so don't be surprised if
 362          * there are compiler warnings on e.g. SCO OpenSwerver or AIX.
 363          * It seems they all eventually get the right idea.
 364          *
 365          * Debian says: ``The fifth argument of getsockopt and
 366          * setsockopt is in reality an int [*] (and this is what BSD
 367          * 4.* and libc4 and libc5 have).  Some POSIX confusion
 368          * resulted in the present socklen_t.  The draft standard has
 369          * not been adopted yet, but glibc2 already follows it and
 370          * also has socklen_t [*]. See also accept(2).''
 371          *
 372          * We now return to your regularly scheduled programming.  */
 373         return(getsockopt(fd, SOL_SOCKET, SO_TYPE, (char *)&v, &l) == 0);
 374 }
 375
 376
 377 void start_accept_loop(int port, int (*fn)(int, int))
 378 {
 379         int s;
 380         extern char *bind_address;
 381         extern int default_af_hint;
 382
 383         /* open an incoming socket */
 384         s = open_socket_in(SOCK_STREAM, port, bind_address, default_af_hint);
 385         if (s == -1)
 386                 exit_cleanup(RERR_SOCKETIO);
 387
 388         /* ready to listen */
 389         if (listen(s, 5) == -1) {
 390                 close(s);
 391                 exit_cleanup(RERR_SOCKETIO);
 392         }
 393
 394
 395         /* now accept incoming connections - forking a new process
 396            for each incoming connection */
 397         while (1) {
 398                 fd_set fds;
 399                 pid_t pid;
 400                 int fd;
 401                 struct sockaddr_storage addr;
 402                 socklen_t addrlen = sizeof addr;
 403
 404                 /* close log file before the potentially very long select so
 405                    file can be trimmed by another process instead of growing
 406                    forever */
 407                 log_close();
 408
 409                 FD_ZERO(&fds);
 410                 FD_SET(s, &fds);
 411
 412                 if (select(s+1, &fds, NULL, NULL, NULL) != 1) {
 413                         continue;
 414                 }
 415
 416                 if(!FD_ISSET(s, &fds)) continue;
 417
 418                 fd = accept(s,(struct sockaddr *)&addr,&addrlen);
 419
 420                 if (fd == -1) continue;
 421
 422                 signal(SIGCHLD, SIG_IGN);
 423
 424                 /* we shouldn't have any children left hanging around
 425                    but I have had reports that on Digital Unix zombies
 426                    are produced, so this ensures that they are reaped */
 427 #ifdef WNOHANG
 428                 while (waitpid(-1, NULL, WNOHANG) > 0);
 429 #endif
 430
 431                 if ((pid = fork()) == 0) {
 432                         int ret;
 433                         close(s);
 434                         /* open log file in child before possibly giving
 435                            up privileges  */
 436                         log_open();
 437                         ret = fn(fd, fd);
 438                         close_all();
 439                         _exit(ret);
 440                 } else if (pid < 0) {
 441                         rprintf(FERROR,
 442                                 RSYNC_NAME
 443                                 ": could not create child server process: %s\n",
 444                                 strerror(errno));
 445                         close(fd);
 446                         /* This might have happened because we're
 447                          * overloaded.  Sleep briefly before trying to
 448                          * accept again. */
 449                         sleep(2);
 450                 } else {
 451                         /* Parent doesn't need this fd anymore. */
 452                         close(fd);
 453                 }
 454         }
 455 }
 456
 457
 458 enum SOCK_OPT_TYPES {OPT_BOOL,OPT_INT,OPT_ON};
 459
 460 struct
 461 {
 462   char *name;
 463   int level;
 464   int option;
 465   int value;
 466   int opttype;
 467 } socket_options[] = {
 468   {"SO_KEEPALIVE",      SOL_SOCKET,    SO_KEEPALIVE,    0,                 OPT_BOOL},
 469   {"SO_REUSEADDR",      SOL_SOCKET,    SO_REUSEADDR,    0,                 OPT_BOOL},
 470   {"SO_BROADCAST",      SOL_SOCKET,    SO_BROADCAST,    0,                 OPT_BOOL},
 471 #ifdef TCP_NODELAY
 472   {"TCP_NODELAY",       IPPROTO_TCP,   TCP_NODELAY,     0,                 OPT_BOOL},
 473 #endif
 474 #ifdef IPTOS_LOWDELAY
 475   {"IPTOS_LOWDELAY",    IPPROTO_IP,    IP_TOS,          IPTOS_LOWDELAY,    OPT_ON},
 476 #endif
 477 #ifdef IPTOS_THROUGHPUT
 478   {"IPTOS_THROUGHPUT",  IPPROTO_IP,    IP_TOS,          IPTOS_THROUGHPUT,  OPT_ON},
 479 #endif
 480 #ifdef SO_SNDBUF
 481   {"SO_SNDBUF",         SOL_SOCKET,    SO_SNDBUF,       0,                 OPT_INT},
 482 #endif
 483 #ifdef SO_RCVBUF
 484   {"SO_RCVBUF",         SOL_SOCKET,    SO_RCVBUF,       0,                 OPT_INT},
 485 #endif
 486 #ifdef SO_SNDLOWAT
 487   {"SO_SNDLOWAT",       SOL_SOCKET,    SO_SNDLOWAT,     0,                 OPT_INT},
 488 #endif
 489 #ifdef SO_RCVLOWAT
 490   {"SO_RCVLOWAT",       SOL_SOCKET,    SO_RCVLOWAT,     0,                 OPT_INT},
 491 #endif
 492 #ifdef SO_SNDTIMEO
 493   {"SO_SNDTIMEO",       SOL_SOCKET,    SO_SNDTIMEO,     0,                 OPT_INT},
 494 #endif
 495 #ifdef SO_RCVTIMEO
 496   {"SO_RCVTIMEO",       SOL_SOCKET,    SO_RCVTIMEO,     0,                 OPT_INT},
 497 #endif
 498   {NULL,0,0,0,0}};
 499
 500
 501
 502 /**
 503  * Set user socket options
 504  **/
 505 void set_socket_options(int fd, char *options)
 506 {
 507         char *tok;
 508         if (!options || !*options) return;
 509
 510         options = strdup(options);
 511
 512         if (!options) out_of_memory("set_socket_options");
 513
 514         for (tok=strtok(options, " \t,"); tok; tok=strtok(NULL," \t,")) {
 515                 int ret=0,i;
 516                 int value = 1;
 517                 char *p;
 518                 int got_value = 0;
 519
 520                 if ((p = strchr(tok,'='))) {
 521                         *p = 0;
 522                         value = atoi(p+1);
 523                         got_value = 1;
 524                 }
 525
 526                 for (i=0;socket_options[i].name;i++)
 527                         if (strcmp(socket_options[i].name,tok)==0)
 528                                 break;
 529
 530                 if (!socket_options[i].name) {
 531                         rprintf(FERROR,"Unknown socket option %s\n",tok);
 532                         continue;
 533                 }
 534
 535                 switch (socket_options[i].opttype) {
 536                 case OPT_BOOL:
 537                 case OPT_INT:
 538                         ret = setsockopt(fd,socket_options[i].level,
 539                                          socket_options[i].option,(char *)&value,sizeof(int));
 540                         break;
 541
 542                 case OPT_ON:
 543                         if (got_value)
 544                                 rprintf(FERROR,"syntax error - %s does not take a value\n",tok);
 545
 546                         {
 547                                 int on = socket_options[i].value;
 548                                 ret = setsockopt(fd,socket_options[i].level,
 549                                                  socket_options[i].option,(char *)&on,sizeof(int));
 550                         }
 551                         break;
 552                 }
 553
 554                 if (ret != 0)
 555                         rprintf(FERROR, "failed to set socket option %s: %s\n", tok,
 556                                 strerror(errno));
 557         }
 558
 559         free(options);
 560 }
 561
 562 /**
 563  * Become a daemon, discarding the controlling terminal
 564  **/
 565 void become_daemon(void)
 566 {
 567         int i;
 568
 569         if (fork()) {
 570                 _exit(0);
 571         }
 572
 573         /* detach from the terminal */
 574 #ifdef HAVE_SETSID
 575         setsid();
 576 #else
 577 #ifdef TIOCNOTTY
 578         i = open("/dev/tty", O_RDWR);
 579         if (i >= 0) {
 580                 ioctl(i, (int) TIOCNOTTY, (char *)0);
 581                 close(i);
 582         }
 583 #endif /* TIOCNOTTY */
 584 #endif
 585         /* make sure that stdin, stdout an stderr don't stuff things
 586            up (library functions, for example) */
 587         for (i=0;i<3;i++) {
 588                 close(i);
 589                 open("/dev/null", O_RDWR);
 590         }
 591 }
 592
 593
 594 /**
 595  * This is like socketpair but uses tcp. It is used by the Samba
 596  * regression test code.
 597  *
 598  * The function guarantees that nobody else can attach to the socket,
 599  * or if they do that this function fails and the socket gets closed
 600  * returns 0 on success, -1 on failure the resulting file descriptors
 601  * are symmetrical.
 602  **/
 603 static int socketpair_tcp(int fd[2])
 604 {
 605         int listener;
 606         struct sockaddr_in sock;
 607         struct sockaddr_in sock2;
 608         socklen_t socklen = sizeof(sock);
 609         int connect_done = 0;
 610
 611         fd[0] = fd[1] = listener = -1;
 612
 613         memset(&sock, 0, sizeof(sock));
 614
 615         if ((listener = socket(PF_INET, SOCK_STREAM, 0)) == -1) goto failed;
 616
 617         memset(&sock2, 0, sizeof(sock2));
 618 #ifdef HAVE_SOCKADDR_LEN
 619         sock2.sin_len = sizeof(sock2);
 620 #endif
 621         sock2.sin_family = PF_INET;
 622
 623         bind(listener, (struct sockaddr *)&sock2, sizeof(sock2));
 624
 625         if (listen(listener, 1) != 0) goto failed;
 626
 627         if (getsockname(listener, (struct sockaddr *)&sock, &socklen) != 0) goto failed;
 628
 629         if ((fd[1] = socket(PF_INET, SOCK_STREAM, 0)) == -1) goto failed;
 630
 631         set_nonblocking(fd[1]);
 632
 633         sock.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 634
 635         if (connect(fd[1],(struct sockaddr *)&sock,sizeof(sock)) == -1) {
 636                 if (errno != EINPROGRESS) goto failed;
 637         } else {
 638                 connect_done = 1;
 639         }
 640
 641         if ((fd[0] = accept(listener, (struct sockaddr *)&sock, &socklen)) == -1) goto failed;
 642
 643         close(listener);
 644         if (connect_done == 0) {
 645                 if (connect(fd[1],(struct sockaddr *)&sock,sizeof(sock)) != 0
 646                     && errno != EISCONN) goto failed;
 647         }
 648
 649         set_blocking (fd[1]);
 650
 651         /* all OK! */
 652         return 0;
 653
 654  failed:
 655         if (fd[0] != -1) close(fd[0]);
 656         if (fd[1] != -1) close(fd[1]);
 657         if (listener != -1) close(listener);
 658         return -1;
 659 }
 660
 661
 662
 663 /**
 664  * Run a program on a local tcp socket, so that we can talk to it's
 665  * stdin and stdout.  This is used to fake a connection to a daemon
 666  * for testing -- not for the normal case of running SSH.
 667  *
 668  * @return a socket which is attached to a subprocess running
 669  * "prog". stdin and stdout are attached. stderr is left attached to
 670  * the original stderr
 671  **/
 672 int sock_exec(const char *prog)
 673 {
 674         int fd[2];
 675
 676         if (socketpair_tcp(fd) != 0) {
 677                 rprintf (FERROR, RSYNC_NAME
 678                          ": socketpair_tcp failed (%s)\n",
 679                          strerror(errno));
 680                 return -1;
 681         }
 682         if (fork() == 0) {
 683                 close(fd[0]);
 684                 close(0);
 685                 close(1);
 686                 dup(fd[1]);
 687                 dup(fd[1]);
 688                 if (verbose > 3) {
 689                         /* Can't use rprintf because we've forked. */
 690                         fprintf (stderr,
 691                                  RSYNC_NAME ": execute socket program \"%s\"\n",
 692                                  prog);
 693                 }
 694                 exit (system (prog));
 695         }
 696         close (fd[1]);
 697         return fd[0];
 698 }
 699
 700
 701