socket.c

/* -*- 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(*(uchar*)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);
	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, resp->ai_addr, resp->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;
}


static RETSIGTYPE sigchld_handler(UNUSED(int val))
{
	signal(SIGCHLD, sigchld_handler);
#ifdef WNOHANG
	while (waitpid(-1, NULL, WNOHANG) > 0) {}
#endif
}


void start_accept_loop(int port, int (*fn)(int, 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, sigchld_handler);

		if ((pid = fork()) == 0) {
			int ret;
			close(s);
			/* open log file in child before possibly giving
			   up privileges  */
			log_open();
			ret = fn(fd, fd);
			close_all();
			_exit(ret);
		} 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];
}