src/network.c

/* dnsmasq is Copyright (c) 2000 - 2006 Simon Kelley

   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; version 2 dated June, 1991.

   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.
*/

#include "dnsmasq.h"

int iface_check(struct daemon *daemon, int family, struct all_addr *addr, char *name)
{
  struct iname *tmp;
  int ret = 1;

  /* Note: have to check all and not bail out early, so that we set the
     "used" flags. */

  if (daemon->if_names || daemon->if_addrs)
    {
      ret = 0;

      for (tmp = daemon->if_names; tmp; tmp = tmp->next)
	if (tmp->name && (strcmp(tmp->name, name) == 0))
	  ret = tmp->used = 1;
	        
      for (tmp = daemon->if_addrs; tmp; tmp = tmp->next)
	if (tmp->addr.sa.sa_family == family)
	  {
	    if (family == AF_INET &&
		tmp->addr.in.sin_addr.s_addr == addr->addr.addr4.s_addr)
	      ret = tmp->used = 1;
#ifdef HAVE_IPV6
	    else if (family == AF_INET6 &&
		     IN6_ARE_ADDR_EQUAL(&tmp->addr.in6.sin6_addr, 
					&addr->addr.addr6))
	      ret = tmp->used = 1;
#endif
	  }          
    }
  
  for (tmp = daemon->if_except; tmp; tmp = tmp->next)
    if (tmp->name && (strcmp(tmp->name, name) == 0))
      ret = 0;
  
  return ret; 
}
      
static int iface_allowed(struct daemon *daemon, struct irec **irecp, int if_index, 
			 union mysockaddr *addr, struct in_addr netmask) 
{
  struct irec *iface;
  int fd;
  struct ifreq ifr;
  
  /* check whether the interface IP has been added already 
     we call this routine multiple times. */
  for (iface = *irecp; iface; iface = iface->next) 
    if (sockaddr_isequal(&iface->addr, addr))
      return 1;
  
#ifdef HAVE_LINUX_NETWORK
  ifr.ifr_ifindex = if_index;
#endif
  
  if ((fd = socket(PF_INET, SOCK_DGRAM, 0)) == -1 ||
#ifdef HAVE_LINUX_NETWORK
      ioctl(fd, SIOCGIFNAME, &ifr) == -1 ||
#else
      !if_indextoname(if_index, ifr.ifr_name) ||
#endif
      ioctl(fd, SIOCGIFFLAGS, &ifr) == -1)
    {
      if (fd != -1)
	{
	  int errsave = errno;
	  close(fd);
	  errno = errsave;
	}
      return 0;
    }
  
  close(fd);
  
  /* If we are restricting the set of interfaces to use, make
     sure that loopback interfaces are in that set. */
  if (daemon->if_names && (ifr.ifr_flags & IFF_LOOPBACK))
    {
      struct iname *lo;
      for (lo = daemon->if_names; lo; lo = lo->next)
	if (lo->name && strcmp(lo->name, ifr.ifr_name) == 0)
	  {
	    lo->isloop = 1;
	    break;
	  }
      
      if (!lo && (lo = malloc(sizeof(struct iname))))
	{
	  lo->name = safe_malloc(strlen(ifr.ifr_name)+1);
	  strcpy(lo->name, ifr.ifr_name);
	  lo->isloop = lo->used = 1;
	  lo->next = daemon->if_names;
	  daemon->if_names = lo;
	}
    }
  
  if (addr->sa.sa_family == AF_INET &&
      !iface_check(daemon, AF_INET, (struct all_addr *)&addr->in.sin_addr, ifr.ifr_name))
    return 1;

#ifdef HAVE_IPV6
  if (addr->sa.sa_family == AF_INET6 &&
      !iface_check(daemon, AF_INET6, (struct all_addr *)&addr->in6.sin6_addr, ifr.ifr_name))
    return 1;
#endif

  /* add to list */
  if ((iface = malloc(sizeof(struct irec))))
    {
      iface->addr = *addr;
      iface->netmask = netmask;
      iface->next = *irecp;
      *irecp = iface; 
      return 1;
    }
  
  errno = ENOMEM; 
  return 0;
}

#ifdef HAVE_IPV6
static int iface_allowed_v6(struct daemon *daemon, struct in6_addr *local, 
			    int scope, int if_index, void *vparam)
{
  union mysockaddr addr;
  struct in_addr netmask; /* dummy */
  
  netmask.s_addr = 0;
  
  memset(&addr, 0, sizeof(addr));
#ifdef HAVE_SOCKADDR_SA_LEN
  addr.in6.sin6_len = sizeof(addr.in6);
#endif
  addr.in6.sin6_family = AF_INET6;
  addr.in6.sin6_addr = *local;
  addr.in6.sin6_port = htons(daemon->port);
  addr.in6.sin6_scope_id = scope;
  
  return iface_allowed(daemon, (struct irec **)vparam, if_index, &addr, netmask);
}
#endif

static int iface_allowed_v4(struct daemon *daemon, struct in_addr local, int if_index, 
			    struct in_addr netmask, struct in_addr broadcast, void *vparam)
{
  union mysockaddr addr;

  memset(&addr, 0, sizeof(addr));
#ifdef HAVE_SOCKADDR_SA_LEN
  addr.in.sin_len = sizeof(addr.in);
#endif
  addr.in.sin_family = AF_INET;
  addr.in.sin_addr = broadcast; /* warning */
  addr.in.sin_addr = local;
  addr.in.sin_port = htons(daemon->port);

  return iface_allowed(daemon, (struct irec **)vparam, if_index, &addr, netmask);
}
   

int enumerate_interfaces(struct daemon *daemon)
{
#ifdef HAVE_IPV6
  return iface_enumerate(daemon, &daemon->interfaces, iface_allowed_v4, iface_allowed_v6);
#else
  return iface_enumerate(daemon, &daemon->interfaces, iface_allowed_v4, NULL);
#endif
}

/* set NONBLOCK and CLOEXEC bits on fd: See Stevens 16.6 */
int fix_fd(int fd)
{
  int flags;

  if ((flags = fcntl(fd, F_GETFL)) == -1 ||
      fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1 ||
      (flags = fcntl(fd, F_GETFD)) == -1 ||
      fcntl(fd, F_SETFD, flags | FD_CLOEXEC) == -1)
    return 0;

  return 1;
}

#if defined(HAVE_IPV6)
static int create_ipv6_listener(struct listener **link, int port)
{
  union mysockaddr addr;
  int tcpfd, fd;
  struct listener *l;
  int opt = 1;

  memset(&addr, 0, sizeof(addr));
  addr.in6.sin6_family = AF_INET6;
  addr.in6.sin6_addr = in6addr_any;
  addr.in6.sin6_port = htons(port);
#ifdef HAVE_SOCKADDR_SA_LEN
  addr.in6.sin6_len = sizeof(addr.in6);
#endif

  /* No error of the kernel doesn't support IPv6 */
  if ((fd = socket(AF_INET6, SOCK_DGRAM, 0)) == -1)
    return (errno == EPROTONOSUPPORT ||
	    errno == EAFNOSUPPORT ||
	    errno == EINVAL);
  
  if ((tcpfd = socket(AF_INET6, SOCK_STREAM, 0)) == -1)
    return 0;
      
  if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) == -1 ||
      setsockopt(tcpfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) == -1 ||
      setsockopt(fd, IPV6_LEVEL, IPV6_V6ONLY, &opt, sizeof(opt)) == -1 ||
      setsockopt(tcpfd, IPV6_LEVEL, IPV6_V6ONLY, &opt, sizeof(opt)) == -1 ||
      !fix_fd(fd) ||
      !fix_fd(tcpfd) ||
#ifdef IPV6_RECVPKTINFO
      setsockopt(fd, IPV6_LEVEL, IPV6_RECVPKTINFO, &opt, sizeof(opt)) == -1 ||
#else
      setsockopt(fd, IPV6_LEVEL, IPV6_PKTINFO, &opt, sizeof(opt)) == -1 ||
#endif
      bind(tcpfd, (struct sockaddr *)&addr, sa_len(&addr)) == -1 ||
      listen(tcpfd, 5) == -1 ||
      bind(fd, (struct sockaddr *)&addr, sa_len(&addr)) == -1) 
    return 0;
      
  l = safe_malloc(sizeof(struct listener));
  l->fd = fd;
  l->tcpfd = tcpfd;
  l->family = AF_INET6;
  l->next = NULL;
  *link = l;
  
  return 1;
}
#endif

struct listener *create_wildcard_listeners(int port)
{
  union mysockaddr addr;
  int opt = 1;
  struct listener *l, *l6 = NULL;
  int tcpfd, fd;

  memset(&addr, 0, sizeof(addr));
  addr.in.sin_family = AF_INET;
  addr.in.sin_addr.s_addr = INADDR_ANY;
  addr.in.sin_port = htons(port);
#ifdef HAVE_SOCKADDR_SA_LEN
  addr.in.sin_len = sizeof(struct sockaddr_in);
#endif

  if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) == -1 ||
      (tcpfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    return NULL;
  
  if (setsockopt(tcpfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) == -1 ||
      bind(tcpfd, (struct sockaddr *)&addr, sa_len(&addr)) == -1 ||
      listen(tcpfd, 5) == -1 ||
      !fix_fd(tcpfd) ||
#ifdef HAVE_IPV6
      !create_ipv6_listener(&l6, port) ||
#endif
      setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) == -1 ||
      !fix_fd(fd) ||
#if defined(HAVE_LINUX_NETWORK) 
      setsockopt(fd, SOL_IP, IP_PKTINFO, &opt, sizeof(opt)) == -1 ||
#elif defined(IP_RECVDSTADDR) && defined(IP_RECVIF)
      setsockopt(fd, IPPROTO_IP, IP_RECVDSTADDR, &opt, sizeof(opt)) == -1 ||
      setsockopt(fd, IPPROTO_IP, IP_RECVIF, &opt, sizeof(opt)) == -1 ||
#endif 
      bind(fd, (struct sockaddr *)&addr, sa_len(&addr)) == -1)
    return NULL;
      
  l = safe_malloc(sizeof(struct listener));
  l->family = AF_INET;
  l->fd = fd;
  l->tcpfd = tcpfd;
  l->next = l6;

  return l;
}

struct listener *create_bound_listeners(struct daemon *daemon)
{

  struct listener *listeners = NULL;
  struct irec *iface;
  int opt = 1;
  
  for (iface = daemon->interfaces; iface; iface = iface->next)
    {
      struct listener *new = safe_malloc(sizeof(struct listener));
      new->family = iface->addr.sa.sa_family;
      new->iface = iface;
      new->next = listeners;
      if ((new->tcpfd = socket(iface->addr.sa.sa_family, SOCK_STREAM, 0)) == -1 ||
	  (new->fd = socket(iface->addr.sa.sa_family, SOCK_DGRAM, 0)) == -1 ||
	  setsockopt(new->fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) == -1 ||
	  setsockopt(new->tcpfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) == -1 ||
	  !fix_fd(new->tcpfd) ||
	  !fix_fd(new->fd))
	die(_("failed to create listening socket: %s"), NULL);
      
#ifdef HAVE_IPV6
      if (iface->addr.sa.sa_family == AF_INET6)
	{
	  if (setsockopt(new->fd, IPV6_LEVEL, IPV6_V6ONLY, &opt, sizeof(opt)) == -1 ||
	      setsockopt(new->tcpfd, IPV6_LEVEL, IPV6_V6ONLY, &opt, sizeof(opt)) == -1)
	    die(_("failed to set IPV6 options on listening socket: %s"), NULL);
	}
#endif
      
      if (bind(new->tcpfd, &iface->addr.sa, sa_len(&iface->addr)) == -1 ||
	  bind(new->fd, &iface->addr.sa, sa_len(&iface->addr)) == -1)
	{
#ifdef HAVE_IPV6
	  if (iface->addr.sa.sa_family == AF_INET6 && errno == ENODEV)
	    {
	      close(new->tcpfd);
	      close(new->fd);
	      free(new);
	    }
	  else
#endif
	    {
	      prettyprint_addr(&iface->addr, daemon->namebuff);
	      die(_("failed to bind listening socket for %s: %s"), 
		  daemon->namebuff);
	    }
	}
      else
	 {
	   listeners = new;     
	   if (listen(new->tcpfd, 5) == -1)
	     die(_("failed to listen on socket: %s"), NULL);
	 }
    }
  
  return listeners;
}

struct serverfd *allocate_sfd(union mysockaddr *addr, struct serverfd **sfds)
{
  struct serverfd *sfd;

  /* may have a suitable one already */
  for (sfd = *sfds; sfd; sfd = sfd->next )
    if (sockaddr_isequal(&sfd->source_addr, addr))
      return sfd;
  
  /* need to make a new one. */
  errno = ENOMEM; /* in case malloc fails. */
  if (!(sfd = malloc(sizeof(struct serverfd))))
    return NULL;
  
  if ((sfd->fd = socket(addr->sa.sa_family, SOCK_DGRAM, 0)) == -1)
    {
      free(sfd);
      return NULL;
    }
  
  if (bind(sfd->fd, (struct sockaddr *)addr, sa_len(addr)) == -1 ||
      !fix_fd(sfd->fd))
    {
      int errsave = errno; /* save error from bind. */
      close(sfd->fd);
      free(sfd);
      errno = errsave;
      return NULL;
    }
  
  sfd->source_addr = *addr;
  sfd->next = *sfds;
  *sfds = sfd;
  
  return sfd;
}

void check_servers(struct daemon *daemon)
{
  struct irec *iface;
  struct server *new, *tmp, *ret = NULL;
  int port = 0;

  for (new = daemon->servers; new; new = tmp)
    {
      tmp = new->next;
      
      if (!(new->flags & (SERV_LITERAL_ADDRESS | SERV_NO_ADDR)))
	{
	  port = prettyprint_addr(&new->addr, daemon->namebuff);

	  /* 0.0.0.0 is nothing, the stack treats it like 127.0.0.1 */
	  if (new->addr.sa.sa_family == AF_INET &&
	      new->addr.in.sin_addr.s_addr == 0)
	    {
	      free(new);
	      continue;
	    }

	  for (iface = daemon->interfaces; iface; iface = iface->next)
	    if (sockaddr_isequal(&new->addr, &iface->addr))
	      break;
	  if (iface)
	    {
	      syslog(LOG_WARNING, _("ignoring nameserver %s - local interface"), daemon->namebuff);
	      free(new);
	      continue;
	    }
	  
	  /* Do we need a socket set? */
	  if (!new->sfd && !(new->sfd = allocate_sfd(&new->source_addr, &daemon->sfds)))
	    {
	      syslog(LOG_WARNING, 
		     _("ignoring nameserver %s - cannot make/bind socket: %m"), daemon->namebuff);
	      free(new);
	      continue;
	    }
	}
      
      /* reverse order - gets it right. */
      new->next = ret;
      ret = new;
      
      if (new->flags & (SERV_HAS_DOMAIN | SERV_FOR_NODOTS))
	{
	  char *s1, *s2;
	  if (new->flags & SERV_HAS_DOMAIN)
	    s1 = _("domain"), s2 = new->domain;
	  else
	    s1 = _("unqualified"), s2 = _("domains");
	  
	  if (new->flags & SERV_NO_ADDR)
	    syslog(LOG_INFO, _("using local addresses only for %s %s"), s1, s2);
	  else if (!(new->flags & SERV_LITERAL_ADDRESS))
	    syslog(LOG_INFO, _("using nameserver %s#%d for %s %s"), daemon->namebuff, port, s1, s2);
	}
      else
	syslog(LOG_INFO, _("using nameserver %s#%d"), daemon->namebuff, port); 
    }
  
  daemon->servers = ret;
}

/* Return zero if no servers found, in that case we keep polling.
   This is a protection against an update-time/write race on resolv.conf */
int reload_servers(char *fname, struct daemon *daemon)
{
  FILE *f;
  char *line;
  struct server *old_servers = NULL;
  struct server *new_servers = NULL;
  struct server *serv;
  int gotone = 0;

  /* buff happens to be MAXDNAME long... */
  if (!(f = fopen(fname, "r")))
    {
      syslog(LOG_ERR, _("failed to read %s: %m"), fname);
      return 0;
    }
  
  /* move old servers to free list - we can reuse the memory 
     and not risk malloc if there are the same or fewer new servers. 
     Servers which were specced on the command line go to the new list. */
  for (serv = daemon->servers; serv;)
    {
      struct server *tmp = serv->next;
      if (serv->flags & SERV_FROM_RESOLV)
	{
	  serv->next = old_servers;
	  old_servers = serv; 
	  /* forward table rules reference servers, so have to blow them away */
	  server_gone(daemon, serv);
	}
      else
	{
	  serv->next = new_servers;
	  new_servers = serv;
	}
      serv = tmp;
    }
  
  while ((line = fgets(daemon->namebuff, MAXDNAME, f)))
    {
      union mysockaddr addr, source_addr;
      char *token = strtok(line, " \t\n\r");
      
      if (!token || strcmp(token, "nameserver") != 0)
	continue;
      if (!(token = strtok(NULL, " \t\n\r")))
	continue;
      
      memset(&addr, 0, sizeof(addr));
      memset(&source_addr, 0, sizeof(source_addr));
      
      if ((addr.in.sin_addr.s_addr = inet_addr(token)) != (in_addr_t) -1)
	{
#ifdef HAVE_SOCKADDR_SA_LEN
	  source_addr.in.sin_len = addr.in.sin_len = sizeof(source_addr.in);
#endif
	  source_addr.in.sin_family = addr.in.sin_family = AF_INET;
	  addr.in.sin_port = htons(NAMESERVER_PORT);
	  source_addr.in.sin_addr.s_addr = INADDR_ANY;
	  source_addr.in.sin_port = htons(daemon->query_port);
	}
#ifdef HAVE_IPV6
      else if (inet_pton(AF_INET6, token, &addr.in6.sin6_addr) > 0)
	{
#ifdef HAVE_SOCKADDR_SA_LEN
	  source_addr.in6.sin6_len = addr.in6.sin6_len = sizeof(source_addr.in6);
#endif
	  source_addr.in6.sin6_family = addr.in6.sin6_family = AF_INET6;
	  addr.in6.sin6_port = htons(NAMESERVER_PORT);
	  source_addr.in6.sin6_addr = in6addr_any;
	  source_addr.in6.sin6_port = htons(daemon->query_port);
	}
#endif /* IPV6 */
      else
	continue;
      
      if (old_servers)
	{
	  serv = old_servers;
	  old_servers = old_servers->next;
	}
      else if (!(serv = malloc(sizeof (struct server))))
	continue;
      
      /* this list is reverse ordered: 
	 it gets reversed again in check_servers */
      serv->next = new_servers;
      new_servers = serv;
      serv->addr = addr;
      serv->source_addr = source_addr;
      serv->domain = NULL;
      serv->sfd = NULL;
      serv->flags = SERV_FROM_RESOLV;

      gotone = 1;
    }
  
  /* Free any memory not used. */
  while (old_servers)
    {
      struct server *tmp = old_servers->next;
      free(old_servers);
      old_servers = tmp;
    }

  daemon->servers = new_servers;
  fclose(f);

  return gotone;
}