コード例 #1
0
ファイル: forward.c プロジェクト: MIPS/external-dnsmasq
/* The daemon forks before calling this: it should deal with one connection,
   blocking as neccessary, and then return. Note, need to be a bit careful
   about resources for debug mode, when the fork is suppressed: that's
   done by the caller. */
unsigned char *tcp_request(int confd, time_t now,
			   struct in_addr local_addr, struct in_addr netmask)
{
  int size = 0;
  size_t m;
  unsigned short qtype, gotname;
  unsigned char c1, c2;
  /* Max TCP packet + slop */
  unsigned char *packet = whine_malloc(65536 + MAXDNAME + RRFIXEDSZ);
  HEADER *header;
  struct server *last_server;
  
  while (1)
    {
      if (!packet ||
	  !read_write(confd, &c1, 1, 1) || !read_write(confd, &c2, 1, 1) ||
	  !(size = c1 << 8 | c2) ||
	  !read_write(confd, packet, size, 1))
       	return packet; 
  
      if (size < (int)sizeof(HEADER))
	continue;
      
      header = (HEADER *)packet;
      
      if ((gotname = extract_request(header, (unsigned int)size, daemon->namebuff, &qtype)))
	{
	  union mysockaddr peer_addr;
	  socklen_t peer_len = sizeof(union mysockaddr);
	  
	  if (getpeername(confd, (struct sockaddr *)&peer_addr, &peer_len) != -1)
	    {
	      char types[20];

	      querystr(types, qtype);

	      if (peer_addr.sa.sa_family == AF_INET) 
		log_query(F_QUERY | F_IPV4 | F_FORWARD, daemon->namebuff, 
			  (struct all_addr *)&peer_addr.in.sin_addr, types);
#ifdef HAVE_IPV6
	      else
		log_query(F_QUERY | F_IPV6 | F_FORWARD, daemon->namebuff, 
			  (struct all_addr *)&peer_addr.in6.sin6_addr, types);
#endif
	    }
	}
      
      /* m > 0 if answered from cache */
      m = answer_request(header, ((char *) header) + 65536, (unsigned int)size, 
			 local_addr, netmask, now);

      /* Do this by steam now we're not in the select() loop */
      check_log_writer(NULL); 
      
      if (m == 0)
	{
	  unsigned short flags = 0;
	  struct all_addr *addrp = NULL;
	  int type = 0;
	  char *domain = NULL;
	  
	  if (gotname)
	    flags = search_servers(now, &addrp, gotname, daemon->namebuff, &type, &domain);
	  
	  if (type != 0  || (daemon->options & OPT_ORDER) || !daemon->last_server)
	    last_server = daemon->servers;
	  else
	    last_server = daemon->last_server;
      
	  if (!flags && last_server)
	    {
	      struct server *firstsendto = NULL;
	      unsigned int crc = questions_crc(header, (unsigned int)size, daemon->namebuff);

	      /* Loop round available servers until we succeed in connecting to one.
	         Note that this code subtley ensures that consecutive queries on this connection
	         which can go to the same server, do so. */
	      while (1) 
		{
		  if (!firstsendto)
		    firstsendto = last_server;
		  else
		    {
		      if (!(last_server = last_server->next))
			last_server = daemon->servers;
		      
		      if (last_server == firstsendto)
			break;
		    }
	      
		  /* server for wrong domain */
		  if (type != (last_server->flags & SERV_TYPE) ||
		      (type == SERV_HAS_DOMAIN && !hostname_isequal(domain, last_server->domain)))
		    continue;
		  
		  if ((last_server->tcpfd == -1) &&
		      (last_server->tcpfd = socket(last_server->addr.sa.sa_family, SOCK_STREAM, 0)) != -1 &&
		      (!local_bind(last_server->tcpfd, &last_server->source_addr,
				   last_server->interface, last_server->mark, 1) ||
		       connect(last_server->tcpfd, &last_server->addr.sa, sa_len(&last_server->addr)) == -1))
		    {
		      close(last_server->tcpfd);
		      last_server->tcpfd = -1;
		    }
		  
		  if (last_server->tcpfd == -1)	
		    continue;

		  c1 = size >> 8;
		  c2 = size;
		  
		  if (!read_write(last_server->tcpfd, &c1, 1, 0) ||
		      !read_write(last_server->tcpfd, &c2, 1, 0) ||
		      !read_write(last_server->tcpfd, packet, size, 0) ||
		      !read_write(last_server->tcpfd, &c1, 1, 1) ||
		      !read_write(last_server->tcpfd, &c2, 1, 1))
		    {
		      close(last_server->tcpfd);
		      last_server->tcpfd = -1;
		      continue;
		    } 
		  
		  m = (c1 << 8) | c2;
		  if (!read_write(last_server->tcpfd, packet, m, 1))
		    return packet;
		  
		  if (!gotname)
		    strcpy(daemon->namebuff, "query");
		  if (last_server->addr.sa.sa_family == AF_INET)
		    log_query(F_SERVER | F_IPV4 | F_FORWARD, daemon->namebuff, 
			      (struct all_addr *)&last_server->addr.in.sin_addr, NULL); 
#ifdef HAVE_IPV6
		  else
		    log_query(F_SERVER | F_IPV6 | F_FORWARD, daemon->namebuff, 
			      (struct all_addr *)&last_server->addr.in6.sin6_addr, NULL);
#endif 
		  
		  /* There's no point in updating the cache, since this process will exit and
		     lose the information after a few queries. We make this call for the alias and 
		     bogus-nxdomain side-effects. */
		  /* If the crc of the question section doesn't match the crc we sent, then
		     someone might be attempting to insert bogus values into the cache by 
		     sending replies containing questions and bogus answers. */
		  if (crc == questions_crc(header, (unsigned int)m, daemon->namebuff))
		    m = process_reply(header, now, last_server, (unsigned int)m);
		  
		  break;
		}
	    }
	  
	  /* In case of local answer or no connections made. */
	  if (m == 0)
	    m = setup_reply(header, (unsigned int)size, addrp, flags, daemon->local_ttl);
	}

      check_log_writer(NULL);
      
      c1 = m>>8;
      c2 = m;
      if (!read_write(confd, &c1, 1, 0) ||
	  !read_write(confd, &c2, 1, 0) || 
	  !read_write(confd, packet, m, 0))
	return packet;
    }
コード例 #2
0
ファイル: forward.c プロジェクト: MIPS/external-dnsmasq
/* sets new last_server */
void reply_query(int fd, int family, time_t now)
{
  /* packet from peer server, extract data for cache, and send to
     original requester */
  HEADER *header;
  union mysockaddr serveraddr;
  struct frec *forward;
  socklen_t addrlen = sizeof(serveraddr);
  ssize_t n = recvfrom(fd, daemon->packet, daemon->edns_pktsz, 0, &serveraddr.sa, &addrlen);
  size_t nn;
  struct server *server;
  
  /* packet buffer overwritten */
  daemon->srv_save = NULL;
  
  /* Determine the address of the server replying  so that we can mark that as good */
  serveraddr.sa.sa_family = family;
#ifdef HAVE_IPV6
  if (serveraddr.sa.sa_family == AF_INET6)
    serveraddr.in6.sin6_flowinfo = 0;
#endif
  
  /* spoof check: answer must come from known server, */
  for (server = daemon->servers; server; server = server->next)
    if (!(server->flags & (SERV_LITERAL_ADDRESS | SERV_NO_ADDR)) &&
	sockaddr_isequal(&server->addr, &serveraddr))
      break;
   
  header = (HEADER *)daemon->packet;
  
  if (!server ||
      n < (int)sizeof(HEADER) || !header->qr ||
      !(forward = lookup_frec(ntohs(header->id), questions_crc(header, n, daemon->namebuff))))
    return;
   
  server = forward->sentto;
  
  if ((header->rcode == SERVFAIL || header->rcode == REFUSED) &&
      !(daemon->options & OPT_ORDER) &&
      forward->forwardall == 0)
    /* for broken servers, attempt to send to another one. */
    {
      unsigned char *pheader;
      size_t plen;
      int is_sign;
      
      /* recreate query from reply */
      pheader = find_pseudoheader(header, (size_t)n, &plen, NULL, &is_sign);
      if (!is_sign)
	{
	  header->ancount = htons(0);
	  header->nscount = htons(0);
	  header->arcount = htons(0);
	  if ((nn = resize_packet(header, (size_t)n, pheader, plen)))
	    {
	      header->qr = 0;
	      header->tc = 0;
	      forward_query(-1, NULL, NULL, 0, header, nn, now, forward);
	      return;
	    }
	}
    }   
  
  if ((forward->sentto->flags & SERV_TYPE) == 0)
    {
      if (header->rcode == SERVFAIL || header->rcode == REFUSED)
	server = NULL;
      else
	{
	  struct server *last_server;
	  
	  /* find good server by address if possible, otherwise assume the last one we sent to */ 
	  for (last_server = daemon->servers; last_server; last_server = last_server->next)
	    if (!(last_server->flags & (SERV_LITERAL_ADDRESS | SERV_HAS_DOMAIN | SERV_FOR_NODOTS | SERV_NO_ADDR)) &&
		sockaddr_isequal(&last_server->addr, &serveraddr))
	      {
		server = last_server;
		break;
	      }
	} 
      if (!(daemon->options & OPT_ALL_SERVERS))
	daemon->last_server = server;
    }
  
  /* If the answer is an error, keep the forward record in place in case
     we get a good reply from another server. Kill it when we've
     had replies from all to avoid filling the forwarding table when
     everything is broken */
  if (forward->forwardall == 0 || --forward->forwardall == 1 || 
      (header->rcode != REFUSED && header->rcode != SERVFAIL))
    {
      if ((nn = process_reply(header, now, server, (size_t)n)))
	{
	  header->id = htons(forward->orig_id);
	  header->ra = 1; /* recursion if available */
	  send_from(forward->fd, daemon->options & OPT_NOWILD, daemon->packet, nn, 
		    &forward->source, &forward->dest, forward->iface);
	}
      free_frec(forward); /* cancel */
    }
}
コード例 #3
0
ファイル: forward.c プロジェクト: MIPS/external-dnsmasq
static int forward_query(int udpfd, union mysockaddr *udpaddr,
			 struct all_addr *dst_addr, unsigned int dst_iface,
			 HEADER *header, size_t plen, time_t now, struct frec *forward)
{
  char *domain = NULL;
  int type = 0;
  struct all_addr *addrp = NULL;
  unsigned int crc = questions_crc(header, plen, daemon->namebuff);
  unsigned short flags = 0;
  unsigned short gotname = extract_request(header, plen, daemon->namebuff, NULL);
  struct server *start = NULL;
    
  /* may be no servers available. */
  if (!daemon->servers)
    forward = NULL;
  else if (forward || (forward = lookup_frec_by_sender(ntohs(header->id), udpaddr, crc)))
    {
      /* retry on existing query, send to all available servers  */
      domain = forward->sentto->domain;
      forward->sentto->failed_queries++;
      if (!(daemon->options & OPT_ORDER))
	{
	  forward->forwardall = 1;
	  daemon->last_server = NULL;
	}
      type = forward->sentto->flags & SERV_TYPE;
      if (!(start = forward->sentto->next))
	start = daemon->servers; /* at end of list, recycle */
      header->id = htons(forward->new_id);
    }
  else 
    {
      if (gotname)
	flags = search_servers(now, &addrp, gotname, daemon->namebuff, &type, &domain);
      
      if (!flags && !(forward = get_new_frec(now, NULL)))
	/* table full - server failure. */
	flags = F_NEG;
      
      if (forward)
	{
	  /* force unchanging id for signed packets */
	  int is_sign;
	  find_pseudoheader(header, plen, NULL, NULL, &is_sign);
	  
	  forward->source = *udpaddr;
	  forward->dest = *dst_addr;
	  forward->iface = dst_iface;
	  forward->orig_id = ntohs(header->id);
	  forward->new_id = get_id(is_sign, forward->orig_id, crc);
	  forward->fd = udpfd;
	  forward->crc = crc;
	  forward->forwardall = 0;
	  header->id = htons(forward->new_id);

	  /* In strict_order mode, or when using domain specific servers
	     always try servers in the order specified in resolv.conf,
	     otherwise, use the one last known to work. */
	  
	  if (type != 0  || (daemon->options & OPT_ORDER))
	    start = daemon->servers;
	  else if (!(start = daemon->last_server) ||
		   daemon->forwardcount++ > FORWARD_TEST ||
		   difftime(now, daemon->forwardtime) > FORWARD_TIME)
	    {
	      start = daemon->servers;
	      forward->forwardall = 1;
	      daemon->forwardcount = 0;
	      daemon->forwardtime = now;
	    }
	}
    }

  /* check for send errors here (no route to host) 
     if we fail to send to all nameservers, send back an error
     packet straight away (helps modem users when offline)  */
  
  if (!flags && forward)
    {
      struct server *firstsentto = start;
      int forwarded = 0;

      while (1)
	{ 
	  /* only send to servers dealing with our domain.
	     domain may be NULL, in which case server->domain 
	     must be NULL also. */
	  
	  if (type == (start->flags & SERV_TYPE) &&
	      (type != SERV_HAS_DOMAIN || hostname_isequal(domain, start->domain)) &&
	      !(start->flags & SERV_LITERAL_ADDRESS))
	    {
	      int fd;

	      /* find server socket to use, may need to get random one. */
	      if (start->sfd)
		fd = start->sfd->fd;
	      else 
		{
#ifdef HAVE_IPV6
		  if (start->addr.sa.sa_family == AF_INET6)
		    {
		      if (!forward->rfd6 &&
			  !(forward->rfd6 = allocate_rfd(AF_INET6)))
			break;
		      daemon->rfd_save = forward->rfd6;
		      fd = forward->rfd6->fd;
		    }
		  else
#endif
		    {
		      if (!forward->rfd4 &&
			  !(forward->rfd4 = allocate_rfd(AF_INET)))
			break;
		      daemon->rfd_save = forward->rfd4;
		      fd = forward->rfd4->fd;
		    }

#ifdef ANDROID
		  // Mark the socket so it goes out on the correct network. Note
		  // that we never clear the mark, only re-set it the next time we
		  // allocate a new random fd. This is because we buffer DNS
		  // queries (in daemon->srv_save, daemon->packet_len) and socket
		  // file descriptors (in daemon->rfd_save) with the expectation of
		  // being able to use them again.
		  //
		  // Server fds are marked separately in allocate_sfd.
		  setsockopt(fd, SOL_SOCKET, SO_MARK, &start->mark, sizeof(start->mark));
#endif
		}

	      if (sendto(fd, (char *)header, plen, 0,
			 &start->addr.sa,
			 sa_len(&start->addr)) == -1)
		{
		  if (retry_send())
		    continue;
		}
	      else
		{
		  /* Keep info in case we want to re-send this packet */
		  daemon->srv_save = start;
		  daemon->packet_len = plen;
		  
		  if (!gotname)
		    strcpy(daemon->namebuff, "query");
		  if (start->addr.sa.sa_family == AF_INET)
		    log_query(F_SERVER | F_IPV4 | F_FORWARD, daemon->namebuff, 
			      (struct all_addr *)&start->addr.in.sin_addr, NULL); 
#ifdef HAVE_IPV6
		  else
		    log_query(F_SERVER | F_IPV6 | F_FORWARD, daemon->namebuff, 
			      (struct all_addr *)&start->addr.in6.sin6_addr, NULL);
#endif 
		  start->queries++;
		  forwarded = 1;
		  forward->sentto = start;
		  if (!forward->forwardall) 
		    break;
		  forward->forwardall++;
		}
	    } 
	  
	  if (!(start = start->next))
 	    start = daemon->servers;
	  
	  if (start == firstsentto)
	    break;
	}
      
      if (forwarded)
	return 1;
      
      /* could not send on, prepare to return */ 
      header->id = htons(forward->orig_id);
      free_frec(forward); /* cancel */
    }	  
  
  /* could not send on, return empty answer or address if known for whole domain */
  if (udpfd != -1)
    {
      plen = setup_reply(header, plen, addrp, flags, daemon->local_ttl);
      send_from(udpfd, daemon->options & OPT_NOWILD, (char *)header, plen, udpaddr, dst_addr, dst_iface);
    }

  return 0;
}
コード例 #4
0
ファイル: forward.c プロジェクト: a33g-dev/platform_samsung
static int forward_query(int udpfd, union mysockaddr *udpaddr,
			 struct all_addr *dst_addr, unsigned int dst_iface,
			 struct dns_header *header, size_t plen, time_t now, struct frec *forward)
{
  char *domain = NULL;
  int type = 0, norebind = 0;
  struct all_addr *addrp = NULL;
  unsigned int crc = questions_crc(header, plen, daemon->namebuff);
  unsigned int flags = 0;
  unsigned int gotname = extract_request(header, plen, daemon->namebuff, NULL);
  struct server *start = NULL;
  
  /* RFC 4035: sect 4.6 para 2 */
  header->hb4 &= ~HB4_AD;
  
  /* may be no servers available. */
  if (!daemon->servers)
    forward = NULL;
  else if (forward || (forward = lookup_frec_by_sender(ntohs(header->id), udpaddr, crc)))
    {
      /* retry on existing query, send to all available servers  */
      domain = forward->sentto->domain;
      forward->sentto->failed_queries++;
      if (!option_bool(OPT_ORDER))
	{
	  forward->forwardall = 1;
	  daemon->last_server = NULL;
	}
      type = forward->sentto->flags & SERV_TYPE;
      if (!(start = forward->sentto->next))
	start = daemon->servers; /* at end of list, recycle */
      header->id = htons(forward->new_id);
    }
  else 
    {
      if (gotname)
	flags = search_servers(now, &addrp, gotname, daemon->namebuff, &type, &domain, &norebind);
      
      if (!flags && !(forward = get_new_frec(now, NULL)))
	/* table full - server failure. */
	flags = F_NEG;
      
      if (forward)
	{
	  forward->source = *udpaddr;
	  forward->dest = *dst_addr;
	  forward->iface = dst_iface;
	  forward->orig_id = ntohs(header->id);
	  forward->new_id = get_id(crc);
	  forward->fd = udpfd;
	  forward->crc = crc;
	  forward->forwardall = 0;
	  if (norebind)
	    forward->flags |= FREC_NOREBIND;
	  if (header->hb4 & HB4_CD)
	    forward->flags |= FREC_CHECKING_DISABLED;

	  header->id = htons(forward->new_id);
	  
	  /* In strict_order mode, always try servers in the order 
	     specified in resolv.conf, if a domain is given 
	     always try all the available servers,
	     otherwise, use the one last known to work. */
	  
	  if (type == 0)
	    {
	      if (option_bool(OPT_ORDER))
		start = daemon->servers;
	      else if (!(start = daemon->last_server) ||
		       daemon->forwardcount++ > FORWARD_TEST ||
		       difftime(now, daemon->forwardtime) > FORWARD_TIME)
		{
		  start = daemon->servers;
		  forward->forwardall = 1;
		  daemon->forwardcount = 0;
		  daemon->forwardtime = now;
		}
	    }
	  else
	    {
	      start = daemon->servers;
	      if (!option_bool(OPT_ORDER))
		forward->forwardall = 1;
	    }
	}
    }

  /* check for send errors here (no route to host) 
     if we fail to send to all nameservers, send back an error
     packet straight away (helps modem users when offline)  */
  
  if (!flags && forward)
    {
      struct server *firstsentto = start;
      int forwarded = 0;
      
      if (udpaddr && option_bool(OPT_ADD_MAC))
	plen = add_mac(header, plen, ((char *) header) + PACKETSZ, udpaddr);
      
      while (1)
	{ 
	  /* only send to servers dealing with our domain.
	     domain may be NULL, in which case server->domain 
	     must be NULL also. */
	  
	  if (type == (start->flags & SERV_TYPE) &&
	      (type != SERV_HAS_DOMAIN || hostname_isequal(domain, start->domain)) &&
	      !(start->flags & SERV_LITERAL_ADDRESS))
	    {
	      int fd;

	      /* find server socket to use, may need to get random one. */
	      if (start->sfd)
		fd = start->sfd->fd;
	      else 
		{
#ifdef HAVE_IPV6
		  if (start->addr.sa.sa_family == AF_INET6)
		    {
		      if (!forward->rfd6 &&
			  !(forward->rfd6 = allocate_rfd(AF_INET6)))
			break;
		      daemon->rfd_save = forward->rfd6;
		      fd = forward->rfd6->fd;
		    }
		  else
#endif
		    {
		      if (!forward->rfd4 &&
			  !(forward->rfd4 = allocate_rfd(AF_INET)))
			break;
		      daemon->rfd_save = forward->rfd4;
		      fd = forward->rfd4->fd;
		    }

#ifdef HAVE_CONNTRACK
		  /* Copy connection mark of incoming query to outgoing connection. */
		  if (option_bool(OPT_CONNTRACK))
		    {
		      unsigned int mark;
		      if (get_incoming_mark(udpaddr, dst_addr, 0, &mark))
			setsockopt(fd, SOL_SOCKET, SO_MARK, &mark, sizeof(unsigned int));
		    }
#endif
		}
	      
	      if (sendto(fd, (char *)header, plen, 0,
			 &start->addr.sa,
			 sa_len(&start->addr)) == -1)
		{
		  if (retry_send())
		    continue;
		}
	      else
		{
		  /* Keep info in case we want to re-send this packet */
		  daemon->srv_save = start;
		  daemon->packet_len = plen;
		  
		  if (!gotname)
		    strcpy(daemon->namebuff, "query");
		  if (start->addr.sa.sa_family == AF_INET)
		    log_query(F_SERVER | F_IPV4 | F_FORWARD, daemon->namebuff, 
			      (struct all_addr *)&start->addr.in.sin_addr, NULL); 
#ifdef HAVE_IPV6
		  else
		    log_query(F_SERVER | F_IPV6 | F_FORWARD, daemon->namebuff, 
			      (struct all_addr *)&start->addr.in6.sin6_addr, NULL);
#endif 
		  start->queries++;
		  forwarded = 1;
		  forward->sentto = start;
		  if (!forward->forwardall) 
		    break;
		  forward->forwardall++;
		}
	    } 
	  
	  if (!(start = start->next))
 	    start = daemon->servers;
	  
	  if (start == firstsentto)
	    break;
	}
      
      if (forwarded)
	return 1;
      
      /* could not send on, prepare to return */ 
      header->id = htons(forward->orig_id);
      free_frec(forward); /* cancel */
    }	  
  
  /* could not send on, return empty answer or address if known for whole domain */
  if (udpfd != -1)
    {
      plen = setup_reply(header, plen, addrp, flags, daemon->local_ttl);
      send_from(udpfd, option_bool(OPT_NOWILD), (char *)header, plen, udpaddr, dst_addr, dst_iface);
    }

  return 0;
}
コード例 #5
0
static size_t process_reply(struct daemon *daemon, HEADER *header, time_t now, 
			    unsigned int query_crc, struct server *server, size_t n)
{
  unsigned char *pheader, *sizep;
  int munged = 0;
  size_t plen; 

  /* If upstream is advertising a larger UDP packet size
	 than we allow, trim it so that we don't get overlarge
	 requests for the client. */

  if ((pheader = find_pseudoheader(header, n, &plen, &sizep)))
    {
      unsigned short udpsz;
      unsigned char *psave = sizep;
      
      GETSHORT(udpsz, sizep);
      if (udpsz > daemon->edns_pktsz)
	PUTSHORT(daemon->edns_pktsz, psave);
    }

  if (header->opcode != QUERY || (header->rcode != NOERROR && header->rcode != NXDOMAIN))
    return n;
  
  /* Complain loudly if the upstream server is non-recursive. */
  if (!header->ra && header->rcode == NOERROR && ntohs(header->ancount) == 0 &&
      server && !(server->flags & SERV_WARNED_RECURSIVE))
    {
      prettyprint_addr(&server->addr, daemon->namebuff);
      syslog(LOG_WARNING, _("nameserver %s refused to do a recursive query"), daemon->namebuff);
      if (!(daemon->options & OPT_LOG))
	server->flags |= SERV_WARNED_RECURSIVE;
    }  
    
  if (daemon->bogus_addr && header->rcode != NXDOMAIN &&
      check_for_bogus_wildcard(header, n, daemon->namebuff, daemon->bogus_addr, now))
    {
      munged = 1;
      header->rcode = NXDOMAIN;
      header->aa = 0;
    }
  else 
    {
      if (header->rcode == NXDOMAIN && 
	  extract_request(header, n, daemon->namebuff, NULL) &&
	  check_for_local_domain(daemon->namebuff, now, daemon))
	{
	  /* if we forwarded a query for a locally known name (because it was for 
	     an unknown type) and the answer is NXDOMAIN, convert that to NODATA,
	     since we know that the domain exists, even if upstream doesn't */
	  munged = 1;
	  header->aa = 1;
	  header->rcode = NOERROR;
	}
  
      /* If the crc of the question section doesn't match the crc we sent, then
	 someone might be attempting to insert bogus values into the cache by 
	 sending replies containing questions and bogus answers. */
      if (query_crc == questions_crc(header, n, daemon->namebuff))
	extract_addresses(header, n, daemon->namebuff, now, daemon);
    }
  
  /* do this after extract_addresses. Ensure NODATA reply and remove
     nameserver info. */
  
  if (munged)
    {
      header->ancount = htons(0);
      header->nscount = htons(0);
      header->arcount = htons(0);
    }
  
  /* the bogus-nxdomain stuff, doctor and NXDOMAIN->NODATA munging can all elide
     sections of the packet. Find the new length here and put back pseudoheader
     if it was removed. */
  return resize_packet(header, n, pheader, plen);
}
コード例 #6
0
/* returns new last_server */	
static void forward_query(struct daemon *daemon, int udpfd, union mysockaddr *udpaddr,
			  struct all_addr *dst_addr, unsigned int dst_iface,
			  HEADER *header, size_t plen, time_t now, struct frec *forward)
{
  char *domain = NULL;
  int type = 0;
  struct all_addr *addrp = NULL;
  unsigned int crc = questions_crc(header, plen, daemon->namebuff);
  unsigned short flags = 0;
  unsigned short gotname = extract_request(header, plen, daemon->namebuff, NULL);
  struct server *start = NULL;
    
  /* may be no servers available. */
  if (!daemon->servers)
    forward = NULL;
  else if (forward || (forward = lookup_frec_by_sender(ntohs(header->id), udpaddr, crc)))
    {
      /* retry on existing query, send to all available servers  */
      domain = forward->sentto->domain;
      if (!(daemon->options & OPT_ORDER))
	{
	  forward->forwardall = 1;
	  daemon->last_server = NULL;
	}
      type = forward->sentto->flags & SERV_TYPE;
      if (!(start = forward->sentto->next))
	start = daemon->servers; /* at end of list, recycle */
      header->id = htons(forward->new_id);
    }
  else 
    {
      if (gotname)
	flags = search_servers(daemon, now, &addrp, gotname, daemon->namebuff, &type, &domain);
      
      if (!flags && !(forward = get_new_frec(daemon, now, NULL)))
	/* table full - server failure. */
	flags = F_NEG;
      
      if (forward)
	{
	  forward->source = *udpaddr;
	  forward->dest = *dst_addr;
	  forward->iface = dst_iface;
	  forward->new_id = get_id();
	  forward->fd = udpfd;
	  forward->orig_id = ntohs(header->id);
	  forward->crc = crc;
	  forward->forwardall = 0;
	  header->id = htons(forward->new_id);

	  /* In strict_order mode, or when using domain specific servers
	     always try servers in the order specified in resolv.conf,
	     otherwise, use the one last known to work. */
	  
	  if (type != 0  || (daemon->options & OPT_ORDER))
	    start = daemon->servers;
	  else if (!(start = daemon->last_server))
	    {
	      start = daemon->servers;
	      forward->forwardall = 1;
	    }
	}
    }

  /* check for send errors here (no route to host) 
     if we fail to send to all nameservers, send back an error
     packet straight away (helps modem users when offline)  */
  
  if (!flags && forward)
    {
      struct server *firstsentto = start;
      int forwarded = 0;

      while (1)
	{ 
	  /* only send to servers dealing with our domain.
	     domain may be NULL, in which case server->domain 
	     must be NULL also. */
	  
	  if (type == (start->flags & SERV_TYPE) &&
	      (type != SERV_HAS_DOMAIN || hostname_isequal(domain, start->domain)) &&
	      !(start->flags & SERV_LITERAL_ADDRESS))
	    {
	      if (sendto(start->sfd->fd, (char *)header, plen, 0,
			 &start->addr.sa,
			 sa_len(&start->addr)) == -1)
		{
		  if (retry_send())
		    continue;
		}
	      else
		{
		  /* Keep info in case we want to re-send this packet */
		  daemon->srv_save = start;
		  daemon->packet_len = plen;
		  
		  if (!gotname)
		    strcpy(daemon->namebuff, "query");
		  if (start->addr.sa.sa_family == AF_INET)
		    log_query(F_SERVER | F_IPV4 | F_FORWARD, daemon->namebuff, 
			      (struct all_addr *)&start->addr.in.sin_addr, 0,
			      NULL, 0); 
#ifdef HAVE_IPV6
		  else
		    log_query(F_SERVER | F_IPV6 | F_FORWARD, daemon->namebuff, 
			      (struct all_addr *)&start->addr.in6.sin6_addr, 0,
			      NULL, 0);
#endif 
		  forwarded = 1;
		  forward->sentto = start;
		  if (!forward->forwardall) 
		    break;
		  forward->forwardall++;
		}
	    } 
	  
	  if (!(start = start->next))
 	    start = daemon->servers;
	  
	  if (start == firstsentto)
	    break;
	}
      
      if (forwarded)
	  return;
      
      /* could not send on, prepare to return */ 
      header->id = htons(forward->orig_id);
      forward->new_id = 0; /* cancel */
    }	  
  
  /* could not send on, return empty answer or address if known for whole domain */
  if (udpfd != -1)
    {
      plen = setup_reply(header, plen, addrp, flags, daemon->local_ttl);
      send_from(udpfd, daemon->options & OPT_NOWILD, (char *)header, plen, udpaddr, dst_addr, dst_iface);
    }

  return;
}