---

socket.c

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/* -*- c-file-style: "linux" -*-
   
   rsync -- fast file replication program
   
   Copyright (C) 1992-2001 by Andrew Tridgell <tridge@samba.org>
   Copyright (C) 2001, 2002 by Martin Pool <mbp@samba.org>
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/**
 * @file socket.c
 * 
 * Socket functions used in rsync.
 *
 * This file is now converted to use the new-style getaddrinfo()
 * interface, which supports IPv6 but is also supported on recent
 * IPv4-only machines.  On systems that don't have that interface, we
 * emulate it using the KAME implementation.
 **/

#include "rsync.h"


/**
 * Establish a proxy connection on an open socket to a web proxy by
 * using the HTTP CONNECT method.
 **/
static int establish_proxy_connection(int fd, char *host, int port)
{
        char buffer[1024];
        char *cp;

        snprintf(buffer, sizeof(buffer), "CONNECT %s:%d HTTP/1.0\r\n\r\n", host, port);
        if (write(fd, buffer, strlen(buffer)) != (int) strlen(buffer)) {
                rprintf(FERROR, "failed to write to proxy: %s\n",
                        strerror(errno));
                return -1;
        }

        for (cp = buffer; cp < &buffer[sizeof(buffer) - 1]; cp++) {
                if (read(fd, cp, 1) != 1) {
                        rprintf(FERROR, "failed to read from proxy: %s\n",
                                strerror(errno));
                        return -1;
                }
                if (*cp == '\n')
                        break;
        }

        if (*cp != '\n')
                cp++;
        *cp-- = '\0';
        if (*cp == '\r')
                *cp = '\0';
        if (strncmp(buffer, "HTTP/", 5) != 0) {
                rprintf(FERROR, "bad response from proxy - %s\n",
                        buffer);
                return -1;
        }
        for (cp = &buffer[5]; isdigit(* (unsigned char *) cp) || (*cp == '.'); cp++)
                ;
        while (*cp == ' ')
                cp++;
        if (*cp != '2') {
                rprintf(FERROR, "bad response from proxy - %s\n",
                        buffer);
                return -1;
        }
        /* throw away the rest of the HTTP header */
        while (1) {
                for (cp = buffer; cp < &buffer[sizeof(buffer) - 1];
                     cp++) {
                        if (read(fd, cp, 1) != 1) {
                                rprintf(FERROR, "failed to read from proxy: %s\n",
                                        strerror(errno));
                                return -1;
                        }
                        if (*cp == '\n')
                                break;
                }
                if ((cp > buffer) && (*cp == '\n'))
                        cp--;
                if ((cp == buffer) && ((*cp == '\n') || (*cp == '\r')))
                        break;
        }
        return 0;
}


/**
 * Try to set the local address for a newly-created socket.  Return -1
 * if this fails.
 **/
int try_bind_local(int s,
                   int ai_family, int ai_socktype,
                   const char *bind_address)
{
        int error;
        struct addrinfo bhints, *bres_all, *r;

        memset(&bhints, 0, sizeof(bhints));
        bhints.ai_family = ai_family;
        bhints.ai_socktype = ai_socktype;
        bhints.ai_flags = AI_PASSIVE;
        if ((error = getaddrinfo(bind_address, NULL, &bhints, &bres_all))) {
                rprintf(FERROR, RSYNC_NAME ": getaddrinfo %s: %s\n",
                        bind_address, gai_strerror(error));
                return -1;
        }

        for (r = bres_all; r; r = r->ai_next) {
                if (bind(s, r->ai_addr, r->ai_addrlen) == -1)
                        continue;
                freeaddrinfo(bres_all);
                return s;
        }

        /* no error message; there might be some problem that allows
         * creation of the socket but not binding, perhaps if the
         * machine has no ipv6 address of this name. */
        freeaddrinfo(bres_all);
        return -1;
}


/**
 * Open a socket to a tcp remote host with the specified port .
 *
 * Based on code from Warren.  Proxy support by Stephen Rothwell.
 * getaddrinfo() rewrite contributed by KAME.net.
 *
 * Now that we support IPv6 we need to look up the remote machine's
 * address first, using @p af_hint to set a preference for the type
 * of address.  Then depending on whether it has v4 or v6 addresses we
 * try to open a connection.
 *
 * The loop allows for machines with some addresses which may not be
 * reachable, perhaps because we can't e.g. route ipv6 to that network
 * but we can get ip4 packets through.
 *
 * @param bind_address Local address to use.  Normally NULL to bind
 * the wildcard address.
 *
 * @param af_hint Address family, e.g. AF_INET or AF_INET6.
 **/
int open_socket_out(char *host, int port, const char *bind_address,
                    int af_hint)
{
        int type = SOCK_STREAM;
        int error;
        int s;
        struct addrinfo hints, *res0, *res;
        char portbuf[10];
        char *h;
        int proxied = 0;
        char buffer[1024];
        char *cp;

        /* if we have a RSYNC_PROXY env variable then redirect our
         * connetcion via a web proxy at the given address. The format
         * is hostname:port */
        h = getenv("RSYNC_PROXY");
        proxied = (h != NULL) && (*h != '\0');

        if (proxied) {
                strlcpy(buffer, h, sizeof(buffer));
                cp = strchr(buffer, ':');
                if (cp == NULL) {
                        rprintf(FERROR,
                                "invalid proxy specification: should be HOST:PORT\n");
                        return -1;
                }
                *cp++ = '\0';
                strcpy(portbuf, cp);
                h = buffer;
                if (verbose >= 2) {
                        rprintf(FINFO, "connection via http proxy %s port %s\n",
                                h, portbuf);
                }
        } else {
                snprintf(portbuf, sizeof(portbuf), "%d", port);
                h = host;
        }

        memset(&hints, 0, sizeof(hints));
        hints.ai_family = af_hint;
        hints.ai_socktype = type;
        error = getaddrinfo(h, portbuf, &hints, &res0);
        if (error) {
                rprintf(FERROR, RSYNC_NAME ": getaddrinfo: %s %s: %s\n",
                        h, portbuf, gai_strerror(error));
                return -1;
        }

        s = -1;
        /* Try to connect to all addresses for this machine until we get
         * through.  It might e.g. be multi-homed, or have both IPv4 and IPv6
         * addresses.  We need to create a socket for each record, since the
         * address record tells us what protocol to use to try to connect. */
        for (res = res0; res; res = res->ai_next) {
                s = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
                if (s < 0)
                        continue;

                if (bind_address)
                        if (try_bind_local(s, res->ai_family, type,
                                           bind_address) == -1) {
                                close(s);
                                s = -1;
                                continue;
                        }

                if (connect(s, res->ai_addr, res->ai_addrlen) < 0) {
                        close(s);
                        s = -1;
                        continue;
                }
                if (proxied &&
                    establish_proxy_connection(s, host, port) != 0) {
                        close(s);
                        s = -1;
                        continue;
                } else
                        break;
        }
        freeaddrinfo(res0);
        if (s < 0) {
                rprintf(FERROR, RSYNC_NAME ": failed to connect to %s: %s\n",
                        h, strerror(errno));
                return -1;
        }
        return s;
}


/**
 * Open an outgoing socket, but allow for it to be intercepted by
 * $RSYNC_CONNECT_PROG, which will execute a program across a TCP
 * socketpair rather than really opening a socket.
 *
 * We use this primarily in testing to detect TCP flow bugs, but not
 * cause security problems by really opening remote connections.
 *
 * This is based on the Samba LIBSMB_PROG feature.
 *
 * @param bind_address Local address to use.  Normally NULL to get the stack default.
 **/
int open_socket_out_wrapped (char *host,
                             int port,
                             const char *bind_address,
                             int af_hint)
{
        char *prog;

        if ((prog = getenv ("RSYNC_CONNECT_PROG")) != NULL) 
                return sock_exec (prog);
        else 
                return open_socket_out (host, port, bind_address,
                                        af_hint);
}



/**
 * Open a socket of the specified type, port and address for incoming data
 *
 * Try to be better about handling the results of getaddrinfo(): when
 * opening an inbound socket, we might get several address results,
 * e.g. for the machine's ipv4 and ipv6 name.  
 * 
 * If binding a wildcard, then any one of them should do.  If an address
 * was specified but it's insufficiently specific then that's not our
 * fault.  
 * 
 * However, some of the advertized addresses may not work because e.g. we
 * don't have IPv6 support in the kernel.  In that case go on and try all
 * addresses until one succeeds.
 * 
 * @param bind_address Local address to bind, or NULL to allow it to
 * default.
 **/
static int open_socket_in(int type, int port, const char *bind_address,
                          int af_hint)
{
        int one=1;
        int s;
        struct addrinfo hints, *all_ai, *resp;
        char portbuf[10];
        int error;

        memset(&hints, 0, sizeof(hints));
        hints.ai_family = af_hint;
        hints.ai_socktype = type;
        hints.ai_flags = AI_PASSIVE;
        snprintf(portbuf, sizeof(portbuf), "%d", port);
        error = getaddrinfo(bind_address, portbuf, &hints, &all_ai);
        if (error) {
                rprintf(FERROR, RSYNC_NAME ": getaddrinfo: bind address %s: %s\n",
                        bind_address, gai_strerror(error));
                return -1;
        }

        /* We may not be able to create the socket, if for example the
         * machine knows about IPv6 in the C library, but not in the
         * kernel. */
        for (resp = all_ai; resp; resp = resp->ai_next) {
                s = socket(resp->ai_family, resp->ai_socktype,
                           resp->ai_protocol);

                if (s == -1) 
                        /* See if there's another address that will work... */
                        continue;
                
                setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
                           (char *)&one, sizeof one);
                
                /* now we've got a socket - we need to bind it */
                if (bind(s, all_ai->ai_addr, all_ai->ai_addrlen) < 0) {
                        /* Nope, try another */
                        close(s);
                        continue;
                }

                freeaddrinfo(all_ai);
                return s;
        }

        rprintf(FERROR, RSYNC_NAME ": open inbound socket on port %d failed: "
                "%s\n",
                port, 
                strerror(errno));

        freeaddrinfo(all_ai);
        return -1; 
}


/*
 * Determine if a file descriptor is in fact a socket
 */
int is_a_socket(int fd)
{
        int v;
        socklen_t l;
        l = sizeof(int);

        /* Parameters to getsockopt, setsockopt etc are very
         * unstandardized across platforms, so don't be surprised if
         * there are compiler warnings on e.g. SCO OpenSwerver or AIX.
         * It seems they all eventually get the right idea.
         *
         * Debian says: ``The fifth argument of getsockopt and
         * setsockopt is in reality an int [*] (and this is what BSD
         * 4.* and libc4 and libc5 have).  Some POSIX confusion
         * resulted in the present socklen_t.  The draft standard has
         * not been adopted yet, but glibc2 already follows it and
         * also has socklen_t [*]. See also accept(2).''
         *
         * We now return to your regularly scheduled programming.  */
        return(getsockopt(fd, SOL_SOCKET, SO_TYPE, (char *)&v, &l) == 0);
}


void start_accept_loop(int port, int (*fn)(int ))
{
        int s;
        extern char *bind_address;
        extern int default_af_hint;

        /* open an incoming socket */
        s = open_socket_in(SOCK_STREAM, port, bind_address, default_af_hint);
        if (s == -1)
                exit_cleanup(RERR_SOCKETIO);

        /* ready to listen */
        if (listen(s, 5) == -1) {
                close(s);
                exit_cleanup(RERR_SOCKETIO);
        }


        /* now accept incoming connections - forking a new process
           for each incoming connection */
        while (1) {
                fd_set fds;
                pid_t pid;
                int fd;
                struct sockaddr_storage addr;
                socklen_t addrlen = sizeof addr;

                /* close log file before the potentially very long select so
                   file can be trimmed by another process instead of growing
                   forever */
                log_close();

                FD_ZERO(&fds);
                FD_SET(s, &fds);

                if (select(s+1, &fds, NULL, NULL, NULL) != 1) {
                        continue;
                }

                if(!FD_ISSET(s, &fds)) continue;

                fd = accept(s,(struct sockaddr *)&addr,&addrlen);

                if (fd == -1) continue;

                signal(SIGCHLD, SIG_IGN);

                /* we shouldn't have any children left hanging around
                   but I have had reports that on Digital Unix zombies
                   are produced, so this ensures that they are reaped */
#ifdef WNOHANG
                while (waitpid(-1, NULL, WNOHANG) > 0);
#endif

                if ((pid = fork()) == 0) {
                        close(s);
                        /* open log file in child before possibly giving
                           up privileges  */
                        log_open();
                        _exit(fn(fd));
                } else if (pid < 0) {
                        rprintf(FERROR,
                                RSYNC_NAME
                                ": could not create child server process: %s\n",
                                strerror(errno));
                        close(fd);
                        /* This might have happened because we're
                         * overloaded.  Sleep briefly before trying to
                         * accept again. */
                        sleep(2);
                } else {
                        /* Parent doesn't need this fd anymore. */
                        close(fd);
                }
        }
}


enum SOCK_OPT_TYPES {OPT_BOOL,OPT_INT,OPT_ON};

struct
{
  char *name;
  int level;
  int option;
  int value;
  int opttype;
} socket_options[] = {
  {"SO_KEEPALIVE",      SOL_SOCKET,    SO_KEEPALIVE,    0,                 OPT_BOOL},
  {"SO_REUSEADDR",      SOL_SOCKET,    SO_REUSEADDR,    0,                 OPT_BOOL},
  {"SO_BROADCAST",      SOL_SOCKET,    SO_BROADCAST,    0,                 OPT_BOOL},
#ifdef TCP_NODELAY
  {"TCP_NODELAY",       IPPROTO_TCP,   TCP_NODELAY,     0,                 OPT_BOOL},
#endif
#ifdef IPTOS_LOWDELAY
  {"IPTOS_LOWDELAY",    IPPROTO_IP,    IP_TOS,          IPTOS_LOWDELAY,    OPT_ON},
#endif
#ifdef IPTOS_THROUGHPUT
  {"IPTOS_THROUGHPUT",  IPPROTO_IP,    IP_TOS,          IPTOS_THROUGHPUT,  OPT_ON},
#endif
#ifdef SO_SNDBUF
  {"SO_SNDBUF",         SOL_SOCKET,    SO_SNDBUF,       0,                 OPT_INT},
#endif
#ifdef SO_RCVBUF
  {"SO_RCVBUF",         SOL_SOCKET,    SO_RCVBUF,       0,                 OPT_INT},
#endif
#ifdef SO_SNDLOWAT
  {"SO_SNDLOWAT",       SOL_SOCKET,    SO_SNDLOWAT,     0,                 OPT_INT},
#endif
#ifdef SO_RCVLOWAT
  {"SO_RCVLOWAT",       SOL_SOCKET,    SO_RCVLOWAT,     0,                 OPT_INT},
#endif
#ifdef SO_SNDTIMEO
  {"SO_SNDTIMEO",       SOL_SOCKET,    SO_SNDTIMEO,     0,                 OPT_INT},
#endif
#ifdef SO_RCVTIMEO
  {"SO_RCVTIMEO",       SOL_SOCKET,    SO_RCVTIMEO,     0,                 OPT_INT},
#endif
  {NULL,0,0,0,0}};

        

/**
 * Set user socket options
 **/
void set_socket_options(int fd, char *options)
{
        char *tok;
        if (!options || !*options) return;

        options = strdup(options);
        
        if (!options) out_of_memory("set_socket_options");

        for (tok=strtok(options, " \t,"); tok; tok=strtok(NULL," \t,")) {
                int ret=0,i;
                int value = 1;
                char *p;
                int got_value = 0;

                if ((p = strchr(tok,'='))) {
                        *p = 0;
                        value = atoi(p+1);
                        got_value = 1;
                }

                for (i=0;socket_options[i].name;i++)
                        if (strcmp(socket_options[i].name,tok)==0)
                                break;

                if (!socket_options[i].name) {
                        rprintf(FERROR,"Unknown socket option %s\n",tok);
                        continue;
                }

                switch (socket_options[i].opttype) {
                case OPT_BOOL:
                case OPT_INT:
                        ret = setsockopt(fd,socket_options[i].level,
                                         socket_options[i].option,(char *)&value,sizeof(int));
                        break;
                        
                case OPT_ON:
                        if (got_value)
                                rprintf(FERROR,"syntax error - %s does not take a value\n",tok);

                        {
                                int on = socket_options[i].value;
                                ret = setsockopt(fd,socket_options[i].level,
                                                 socket_options[i].option,(char *)&on,sizeof(int));
                        }
                        break;    
                }
                
                if (ret != 0)
                        rprintf(FERROR, "failed to set socket option %s: %s\n", tok,
                                strerror(errno));
        }

        free(options);
}

/**
 * Become a daemon, discarding the controlling terminal
 **/
void become_daemon(void)
{
        int i;

        if (fork()) {
                _exit(0);
        }

        /* detach from the terminal */
#ifdef HAVE_SETSID
        setsid();
#else
#ifdef TIOCNOTTY
        i = open("/dev/tty", O_RDWR);
        if (i >= 0) {
                ioctl(i, (int) TIOCNOTTY, (char *)0);      
                close(i);
        }
#endif /* TIOCNOTTY */
#endif
        /* make sure that stdin, stdout an stderr don't stuff things
           up (library functions, for example) */
        for (i=0;i<3;i++) {
                close(i); 
                open("/dev/null", O_RDWR);
        }
}


/**
 * This is like socketpair but uses tcp. It is used by the Samba
 * regression test code.
 * 
 * The function guarantees that nobody else can attach to the socket,
 * or if they do that this function fails and the socket gets closed
 * returns 0 on success, -1 on failure the resulting file descriptors
 * are symmetrical.
 **/
static int socketpair_tcp(int fd[2])
{
        int listener;
        struct sockaddr_in sock;
        struct sockaddr_in sock2;
        socklen_t socklen = sizeof(sock);
        int connect_done = 0;
        
        fd[0] = fd[1] = listener = -1;

        memset(&sock, 0, sizeof(sock));
        
        if ((listener = socket(PF_INET, SOCK_STREAM, 0)) == -1) goto failed;

        memset(&sock2, 0, sizeof(sock2));
#ifdef HAVE_SOCKADDR_LEN
        sock2.sin_len = sizeof(sock2);
#endif
        sock2.sin_family = PF_INET;

        bind(listener, (struct sockaddr *)&sock2, sizeof(sock2));

        if (listen(listener, 1) != 0) goto failed;

        if (getsockname(listener, (struct sockaddr *)&sock, &socklen) != 0) goto failed;

        if ((fd[1] = socket(PF_INET, SOCK_STREAM, 0)) == -1) goto failed;

        set_nonblocking(fd[1]);

        sock.sin_addr.s_addr = htonl(INADDR_LOOPBACK);

        if (connect(fd[1],(struct sockaddr *)&sock,sizeof(sock)) == -1) {
                if (errno != EINPROGRESS) goto failed;
        } else {
                connect_done = 1;
        }

        if ((fd[0] = accept(listener, (struct sockaddr *)&sock, &socklen)) == -1) goto failed;

        close(listener);
        if (connect_done == 0) {
                if (connect(fd[1],(struct sockaddr *)&sock,sizeof(sock)) != 0
                    && errno != EISCONN) goto failed;
        }

        set_blocking (fd[1]);

        /* all OK! */
        return 0;

 failed:
        if (fd[0] != -1) close(fd[0]);
        if (fd[1] != -1) close(fd[1]);
        if (listener != -1) close(listener);
        return -1;
}



/**
 * Run a program on a local tcp socket, so that we can talk to it's
 * stdin and stdout.  This is used to fake a connection to a daemon
 * for testing -- not for the normal case of running SSH.
 *
 * @return a socket which is attached to a subprocess running
 * "prog". stdin and stdout are attached. stderr is left attached to
 * the original stderr
 **/
int sock_exec(const char *prog)
{
        int fd[2];
        
        if (socketpair_tcp(fd) != 0) {
                rprintf (FERROR, RSYNC_NAME
                         ": socketpair_tcp failed (%s)\n",
                         strerror(errno));
                return -1;
        }
        if (fork() == 0) {
                close(fd[0]);
                close(0);
                close(1);
                dup(fd[1]);
                dup(fd[1]);
                if (verbose > 3) {
                        /* Can't use rprintf because we've forked. */
                        fprintf (stderr,
                                 RSYNC_NAME ": execute socket program \"%s\"\n",
                                 prog);
                }
                exit (system (prog));
        }
        close (fd[1]);
        return fd[0];
}

---