socket.c

OpenVPN is a robust and highly flexible tunneling application that uses all of the encryption, authe

/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single TCP/UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2004 James Yonan <[e-mail]>
 *
 *  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 (see the file COPYING included with this
 *  distribution); if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#ifdef WIN32
#include "config-win32.h"
#else
#include "config.h"
#endif

#include "syshead.h"

#include "socket.h"
#include "fdmisc.h"
#include "thread.h"
#include "misc.h"

#include "memdbg.h"

/*
 * Functions related to the translation of DNS names to IP addresses.
 */

static const char*
h_errno_msg(int h_errno_err)
{
  switch (h_errno_err)
    {
    case HOST_NOT_FOUND:
      return "[HOST_NOT_FOUND] The specified host is unknown.";
    case NO_DATA:
      return "[NO_DATA] The requested name is valid but does not have an IP address.";
    case NO_RECOVERY:
      return "[NO_RECOVERY] A non-recoverable name server error occurred.";
    case TRY_AGAIN:
      return "[TRY_AGAIN] A temporary error occurred on an authoritative name server.";
    }
  return "[unknown h_errno value]";
}

/*
 * Translate IP addr or hostname to in_addr_t.
 * If resolve error, try again for
 * resolve_retry_seconds seconds.
 */
in_addr_t
getaddr (unsigned int flags,
	 const char *hostname,
	 int resolve_retry_seconds,
	 bool *succeeded,
	 volatile int *signal_received)
{
  struct in_addr ia;
  int status;
  int sigrec = 0;
  const int msglevel = (flags & GETADDR_FATAL) ? M_FATAL : D_RESOLVE_ERRORS;

  CLEAR (ia);
  if (succeeded)
    *succeeded = false;

  if ((flags & (GETADDR_FATAL_ON_SIGNAL|GETADDR_WARN_ON_SIGNAL))
      && !signal_received)
    signal_received = &sigrec;

  status = inet_aton (hostname, &ia);

  if (!status)
    {
      const int fail_wait_interval = 5; /* seconds */
      int resolve_retries = resolve_retry_seconds / fail_wait_interval;
      struct hostent *h;
      const char *fmt;

      CLEAR (ia);

      fmt = "RESOLVE: Cannot resolve host address: %s: %s";
      if ((flags & GETADDR_MENTION_RESOLVE_RETRY)
	  && !resolve_retry_seconds)
	fmt = "RESOLVE: Cannot resolve host address: %s: %s (I would have retried this name query if you had specified the --resolv-retry option.)";

      if (!(flags & GETADDR_RESOLVE))
	{
	  if (flags & GETADDR_FATAL)
	    msg (M_FATAL, "RESOLVE: Cannot parse IP address: %s", hostname);
	  else
	    goto done;
	}

      /*
       * Resolve hostname
       */
      while (true)
	{
	  /* try hostname lookup */
	  h = gethostbyname (hostname);

	  if (signal_received)
	    {
	      get_signal (signal_received);
	      if (*signal_received)
	        goto done;
	    }

	  /* success? */
	  if (h)
	    break;

	  /* resolve lookup failed, should we
	     continue or fail? */
	  msg (((resolve_retries > 0
		 || !(flags & GETADDR_FATAL))
		? D_RESOLVE_ERRORS : M_FATAL),
	       fmt,
	       hostname,
	       h_errno_msg (h_errno));

	  if (--resolve_retries <= 0
	      && !(flags & GETADDR_FATAL))
	    goto done;

	  sleep (fail_wait_interval);
	}

      if (h->h_addrtype != AF_INET || h->h_length != 4)
	{
	    msg (msglevel, "RESOLVE: Sorry, but we only accept IPv4 DNS names: %s", hostname);
	    goto done;
	}

      ia.s_addr = *(in_addr_t *) (h->h_addr_list[0]);

      if (ia.s_addr)
	{
	  if (h->h_addr_list[1]) /* more than one address returned */
	    {
	      int n = 0;

	      /* count address list */
	      while (h->h_addr_list[n])
		++n;
	      ASSERT (n >= 2);

	      msg (D_RESOLVE_ERRORS, "RESOLVE: NOTE: %s resolves to %d addresses, choosing one by random",
		   hostname,
		   n);

	      /* choose address randomly, for basic load-balancing capability */
	      ia.s_addr = *(in_addr_t *) (h->h_addr_list[get_random () % n]);
	    }
	}

      /* hostname resolve succeeded */
      if (succeeded)
	*succeeded = true;
    }
  else
    {
      /* IP address parse succeeded */
      if (succeeded)
	*succeeded = true;
    }

 done:
  if (signal_received && *signal_received)
    {
      int level = 0;
      if (flags & GETADDR_FATAL_ON_SIGNAL)
	level = M_FATAL;
      else if (flags & GETADDR_WARN_ON_SIGNAL)
	level = M_WARN;
      msg (level, "RESOLVE: signal received during DNS resolution attempt");
    }

  return (flags & GETADDR_HOST_ORDER) ? ntohl (ia.s_addr) : ia.s_addr;
}

static void
update_remote (const char* host,
	       struct sockaddr_in *addr,
	       bool *changed)
{
  if (host && addr)
    {
      const in_addr_t new_addr = getaddr (
					  GETADDR_RESOLVE,
					  host,
					  1,
					  NULL,
					  NULL);
      if (new_addr && addr->sin_addr.s_addr != new_addr)
	{
	  addr->sin_addr.s_addr = new_addr;
	  *changed = true;
	}
    }
}

static int
socket_get_sndbuf (int sd)
{
#if defined(HAVE_GETSOCKOPT) && defined(SOL_SOCKET) && defined(SO_SNDBUF)
  int val;
  socklen_t len;

  len = sizeof (val);
  if (getsockopt (sd, SOL_SOCKET, SO_SNDBUF, (void *) &val, &len) == 0
      && len == sizeof (val))
    return val;
#endif
  return 0;
}

static void
socket_set_sndbuf (int sd, int size)
{
#if defined(HAVE_SETSOCKOPT) && defined(SOL_SOCKET) && defined(SO_SNDBUF)
  if (setsockopt (sd, SOL_SOCKET, SO_SNDBUF, (void *) &size, sizeof (size)) != 0)
    {
      msg (M_WARN, "NOTE: setsockopt SO_SNDBUF=%d failed", size);
    }
#endif
}

static int
socket_get_rcvbuf (int sd)
{
#if defined(HAVE_GETSOCKOPT) && defined(SOL_SOCKET) && defined(SO_RCVBUF)
  int val;
  socklen_t len;

  len = sizeof (val);
  if (getsockopt (sd, SOL_SOCKET, SO_RCVBUF, (void *) &val, &len) == 0
      && len == sizeof (val))
    return val;
#endif
  return 0;
}

static void
socket_set_rcvbuf (int sd, int size)
{
#if defined(HAVE_SETSOCKOPT) && defined(SOL_SOCKET) && defined(SO_RCVBUF)
  if (setsockopt (sd, SOL_SOCKET, SO_RCVBUF, (void *) &size, sizeof (size)) != 0)
    {
      msg (M_WARN, "NOTE: setsockopt SO_RCVBUF=%d failed", size);
    }
#endif
}

static void
socket_set_buffers (int fd, const struct socket_buffer_size *sbs)
{
  if (sbs)
    {
      const int sndbuf_old = socket_get_sndbuf (fd);
      const int rcvbuf_old = socket_get_rcvbuf (fd);

      socket_set_sndbuf (fd, sbs->sndbuf);
      socket_set_rcvbuf (fd, sbs->rcvbuf);
       
      msg (D_OSBUF, "Socket Buffers: R=[%d->%d] S=[%d->%d]",
	   rcvbuf_old,
	   socket_get_rcvbuf (fd),
	   sndbuf_old,
	   socket_get_sndbuf (fd));
    }
}

/*
 * Remote list code allows clients to specify a list of
 * potential remote server addresses.
 */

static void
remote_list_next (struct remote_list *l)
{
  if (l)
    {
      int i;
      if (++l->current >= l->len)
	l->current = 0;

      msg (D_REMOTE_LIST, "REMOTE_LIST len=%d current=%d",
	   l->len, l->current);
      for (i = 0; i < l->len; ++i)
	{
	  msg (D_REMOTE_LIST, "[%d] %s:%d",
	       i,
	       l->array[i].hostname,
	       l->array[i].port);
	}
    }
}

void
remote_list_randomize (struct remote_list *l)
{
  int i;
  for (i = 0; i < l->len; ++i)
    {
      const int j = get_random () % l->len;
      if (i != j)
	{
	  struct remote_entry tmp;
	  tmp = l->array[i];
	  l->array[i] = l->array[j];
	  l->array[j] = tmp;
	}
    }
}

static const char *
remote_list_host (const struct remote_list *rl)
{
  if (rl)
    return rl->array[rl->current].hostname;
  else
    return NULL;
}

static int
remote_list_port (const struct remote_list *rl)
{
  if (rl)
    return rl->array[rl->current].port;
  else
    return 0;
}

/*
 * SOCKET INITALIZATION CODE.
 * Create a TCP/UDP socket
 */

static socket_descriptor_t
create_socket_tcp (void)
{
  socket_descriptor_t sd;

  if ((sd = socket (PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
    msg (M_SOCKERR, "Cannot create TCP socket");

  /* set SO_REUSEADDR on socket */
  {
    int on = 1;
    if (setsockopt (sd, SOL_SOCKET, SO_REUSEADDR,
		    (void *) &on, sizeof (on)) < 0)
      msg (M_SOCKERR, "TCP: Cannot setsockopt SO_REUSEADDR on TCP socket");
  }

#if 0
  /* set socket linger options */
  {
    struct linger linger;
    linger.l_onoff = 1;
    linger.l_linger = 2;
    if (setsockopt (sd, SOL_SOCKET, SO_LINGER,
		    (void *) &linger, sizeof (linger)) < 0)
      msg (M_SOCKERR, "TCP: Cannot setsockopt SO_LINGER on TCP socket");
  }
#endif

  return sd;
}

static socket_descriptor_t
create_socket_udp (void)
{
  socket_descriptor_t sd;

  if ((sd = socket (PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
    msg (M_SOCKERR, "UDP: Cannot create UDP socket");
  return sd;
}

static void
create_socket (struct link_socket *sock)
{
  /* create socket */
  if (sock->info.proto == PROTO_UDPv4)
    {
      sock->sd = create_socket_udp ();

      if (sock->socks_proxy)
	{
	  sock->ctrl_sd = create_socket_tcp ();
	}
    }
  else if (sock->info.proto == PROTO_TCPv4_SERVER
	   || sock->info.proto == PROTO_TCPv4_CLIENT)
    {
      sock->sd = create_socket_tcp ();
    }
  else
    {
      ASSERT (0);
    }
}

/*
 * Functions used for establishing a TCP stream connection.
 */

static void
socket_do_listen (socket_descriptor_t sd,
		  const struct sockaddr_in *local,
		  bool do_listen,
		  bool do_set_nonblock)
{
  struct gc_arena gc = gc_new ();
  if (do_listen)
    {
      msg (M_INFO, "Listening for incoming TCP connection on %s", 
	   print_sockaddr (local, &gc));
      if (listen (sd, 1))
	msg (M_SOCKERR, "TCP: listen() failed");
    }

  /* set socket to non-blocking mode */
  if (do_set_nonblock)
    set_nonblock (sd);

  gc_free (&gc);
}

static socket_descriptor_t
socket_do_accept (socket_descriptor_t sd,
		  struct sockaddr_in *remote,
		  const bool nowait)
{
  socklen_t remote_len = sizeof (*remote);
  socket_descriptor_t new_sd = -1;

#ifdef HAVE_GETPEERNAME
  if (nowait)
    {
      new_sd = getpeername (sd, (struct sockaddr *) remote, &remote_len);

      if (new_sd == -1)
	msg (D_LINK_ERRORS | M_ERRNO_SOCK, "TCP: getpeername() failed");
      else
	new_sd = sd;
    }
#else
  if (nowait)
    msg (M_WARN, "TCP: this OS does not provide the getpeername() function");
#endif
  else
    {
      new_sd = accept (sd, (struct sockaddr *) remote, &remote_len);
    }

  if (new_sd == -1)
    {
      msg (D_LINK_ERRORS | M_ERRNO_SOCK, "TCP: accept() failed");
    }
  else if (remote_len != sizeof (*remote))
    {
      msg (D_LINK_ERRORS, "TCP: Received strange incoming connection with unknown address length=%d", remote_len);
      openvpn_close_socket (new_sd);