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libcares/ares_process.c  view on Meta::CPAN

}

/* Something interesting happened on the wire, or there was a timeout.
 * See what's up and respond accordingly.
 */
void ares_process_fd(ares_channel channel,
                     ares_socket_t read_fd, /* use ARES_SOCKET_BAD or valid
                                               file descriptors */
                     ares_socket_t write_fd)
{
  processfds(channel, NULL, read_fd, NULL, write_fd);
}


/* Return 1 if the specified error number describes a readiness error, or 0
 * otherwise. This is mostly for HP-UX, which could return EAGAIN or
 * EWOULDBLOCK. See this man page
 *
 * http://devrsrc1.external.hp.com/STKS/cgi-bin/man2html?
 *     manpage=/usr/share/man/man2.Z/send.2
 */
static int try_again(int errnum)
{
#if !defined EWOULDBLOCK && !defined EAGAIN
#error "Neither EWOULDBLOCK nor EAGAIN defined"
#endif
  switch (errnum)
    {
#ifdef EWOULDBLOCK
    case EWOULDBLOCK:
      return 1;
#endif
#if defined EAGAIN && EAGAIN != EWOULDBLOCK
    case EAGAIN:
      return 1;
#endif
    }
  return 0;
}

static ares_ssize_t socket_writev(ares_channel channel, ares_socket_t s, const struct iovec * vec, int len)
{
  if (channel->sock_funcs)
    return channel->sock_funcs->asendv(s, vec, len, channel->sock_func_cb_data);

  return writev(s, vec, len);
}

static ares_ssize_t socket_write(ares_channel channel, ares_socket_t s, const void * data, size_t len)
{
  if (channel->sock_funcs)
    {
      struct iovec vec;
      vec.iov_base = (void*)data;
      vec.iov_len = len;
      return channel->sock_funcs->asendv(s, &vec, 1, channel->sock_func_cb_data);
    }
  return swrite(s, data, len);
}

/* If any TCP sockets select true for writing, write out queued data
 * we have for them.
 */
static void write_tcp_data(ares_channel channel,
                           fd_set *write_fds,
                           ares_socket_t write_fd,
                           struct timeval *now)
{
  struct server_state *server;
  struct send_request *sendreq;
  struct iovec *vec;
  int i;
  ares_ssize_t scount;
  ares_ssize_t wcount;
  size_t n;

  if(!write_fds && (write_fd == ARES_SOCKET_BAD))
    /* no possible action */
    return;

  for (i = 0; i < channel->nservers; i++)
    {
      /* Make sure server has data to send and is selected in write_fds or
         write_fd. */
      server = &channel->servers[i];
      if (!server->qhead || server->tcp_socket == ARES_SOCKET_BAD ||
          server->is_broken)
        continue;

      if(write_fds) {
        if(!FD_ISSET(server->tcp_socket, write_fds))
          continue;
      }
      else {
        if(server->tcp_socket != write_fd)
          continue;
      }

      if(write_fds)
        /* If there's an error and we close this socket, then open
         * another with the same fd to talk to another server, then we
         * don't want to think that it was the new socket that was
         * ready. This is not disastrous, but is likely to result in
         * extra system calls and confusion. */
        FD_CLR(server->tcp_socket, write_fds);

      /* Count the number of send queue items. */
      n = 0;
      for (sendreq = server->qhead; sendreq; sendreq = sendreq->next)
        n++;

      /* Allocate iovecs so we can send all our data at once. */
      vec = ares_malloc(n * sizeof(struct iovec));
      if (vec)
        {
          /* Fill in the iovecs and send. */
          n = 0;
          for (sendreq = server->qhead; sendreq; sendreq = sendreq->next)
            {
              vec[n].iov_base = (char *) sendreq->data;
              vec[n].iov_len = sendreq->len;
              n++;
            }
          wcount = socket_writev(channel, server->tcp_socket, vec, (int)n);
          ares_free(vec);
          if (wcount < 0)
            {
              if (!try_again(SOCKERRNO))
                handle_error(channel, i, now);
              continue;
            }

          /* Advance the send queue by as many bytes as we sent. */
          advance_tcp_send_queue(channel, i, wcount);
        }
      else
        {
          /* Can't allocate iovecs; just send the first request. */
          sendreq = server->qhead;

          scount = socket_write(channel, server->tcp_socket, sendreq->data, sendreq->len);
          if (scount < 0)
            {

libcares/ares_process.c  view on Meta::CPAN

                                   ares_ssize_t num_bytes)
{
  struct send_request *sendreq;
  struct server_state *server = &channel->servers[whichserver];
  while (num_bytes > 0) {
    sendreq = server->qhead;
    if ((size_t)num_bytes >= sendreq->len) {
      num_bytes -= sendreq->len;
      server->qhead = sendreq->next;
      if (sendreq->data_storage)
        ares_free(sendreq->data_storage);
      ares_free(sendreq);
      if (server->qhead == NULL) {
        SOCK_STATE_CALLBACK(channel, server->tcp_socket, 1, 0);
        server->qtail = NULL;

        /* qhead is NULL so we cannot continue this loop */
        break;
      }
    }
    else {
      sendreq->data += num_bytes;
      sendreq->len -= num_bytes;
      num_bytes = 0;
    }
  }
}

static ares_ssize_t socket_recvfrom(ares_channel channel,
   ares_socket_t s,
   void * data,
   size_t data_len,
   int flags,
   struct sockaddr *from,
   ares_socklen_t *from_len)
{
   if (channel->sock_funcs)
      return channel->sock_funcs->arecvfrom(s, data, data_len,
	 flags, from, from_len,
	 channel->sock_func_cb_data);

#ifdef HAVE_RECVFROM
   return recvfrom(s, data, data_len, flags, from, from_len);
#else
   return sread(s, data, data_len);
#endif
}

static ares_ssize_t socket_recv(ares_channel channel,
   ares_socket_t s,
   void * data,
   size_t data_len)
{
   if (channel->sock_funcs)
      return channel->sock_funcs->arecvfrom(s, data, data_len, 0, 0, 0,
	 channel->sock_func_cb_data);

   return sread(s, data, data_len);
}

/* If any TCP socket selects true for reading, read some data,
 * allocate a buffer if we finish reading the length word, and process
 * a packet if we finish reading one.
 */
static void read_tcp_data(ares_channel channel, fd_set *read_fds,
                          ares_socket_t read_fd, struct timeval *now)
{
  struct server_state *server;
  int i;
  ares_ssize_t count;

  if(!read_fds && (read_fd == ARES_SOCKET_BAD))
    /* no possible action */
    return;

  for (i = 0; i < channel->nservers; i++)
    {
      /* Make sure the server has a socket and is selected in read_fds. */
      server = &channel->servers[i];
      if (server->tcp_socket == ARES_SOCKET_BAD || server->is_broken)
        continue;

      if(read_fds) {
        if(!FD_ISSET(server->tcp_socket, read_fds))
          continue;
      }
      else {
        if(server->tcp_socket != read_fd)
          continue;
      }

      if(read_fds)
        /* If there's an error and we close this socket, then open another
         * with the same fd to talk to another server, then we don't want to
         * think that it was the new socket that was ready. This is not
         * disastrous, but is likely to result in extra system calls and
         * confusion. */
        FD_CLR(server->tcp_socket, read_fds);

      if (server->tcp_lenbuf_pos != 2)
        {
          /* We haven't yet read a length word, so read that (or
           * what's left to read of it).
           */
          count = socket_recv(channel, server->tcp_socket,
			      server->tcp_lenbuf + server->tcp_lenbuf_pos,
			      2 - server->tcp_lenbuf_pos);
          if (count <= 0)
            {
              if (!(count == -1 && try_again(SOCKERRNO)))
                handle_error(channel, i, now);
              continue;
            }

          server->tcp_lenbuf_pos += (int)count;
          if (server->tcp_lenbuf_pos == 2)
            {
              /* We finished reading the length word.  Decode the
               * length and allocate a buffer for the data.
               */
              server->tcp_length = server->tcp_lenbuf[0] << 8
                | server->tcp_lenbuf[1];
              server->tcp_buffer = ares_malloc(server->tcp_length);
              if (!server->tcp_buffer) {
                handle_error(channel, i, now);
                return; /* bail out on malloc failure. TODO: make this
                           function return error codes */
              }
              server->tcp_buffer_pos = 0;
            }
        }
      else
        {
          /* Read data into the allocated buffer. */
          count = socket_recv(channel, server->tcp_socket,
			      server->tcp_buffer + server->tcp_buffer_pos,
			      server->tcp_length - server->tcp_buffer_pos);
          if (count <= 0)
            {
              if (!(count == -1 && try_again(SOCKERRNO)))
                handle_error(channel, i, now);
              continue;
            }

          server->tcp_buffer_pos += (int)count;
          if (server->tcp_buffer_pos == server->tcp_length)
            {
              /* We finished reading this answer; process it and
               * prepare to read another length word.
               */
              process_answer(channel, server->tcp_buffer, server->tcp_length,
                             i, 1, now);
              ares_free(server->tcp_buffer);
              server->tcp_buffer = NULL;
              server->tcp_lenbuf_pos = 0;
              server->tcp_buffer_pos = 0;
            }
        }
    }
}

/* If any UDP sockets select true for reading, process them. */
static void read_udp_packets(ares_channel channel, fd_set *read_fds,
                             ares_socket_t read_fd, struct timeval *now)
{
  struct server_state *server;
  int i;
  ares_ssize_t count;
  unsigned char buf[MAXENDSSZ + 1];
#ifdef HAVE_RECVFROM
  ares_socklen_t fromlen;
  ares_sockaddr from;
#endif

  if(!read_fds && (read_fd == ARES_SOCKET_BAD))
    /* no possible action */
    return;

  for (i = 0; i < channel->nservers; i++)
    {
      /* Make sure the server has a socket and is selected in read_fds. */
      server = &channel->servers[i];

      if (server->udp_socket == ARES_SOCKET_BAD || server->is_broken)
        continue;

      if(read_fds) {
        if(!FD_ISSET(server->udp_socket, read_fds))
          continue;
      }
      else {
        if(server->udp_socket != read_fd)
          continue;
      }

      if(read_fds)
        /* If there's an error and we close this socket, then open
         * another with the same fd to talk to another server, then we
         * don't want to think that it was the new socket that was
         * ready. This is not disastrous, but is likely to result in
         * extra system calls and confusion. */
        FD_CLR(server->udp_socket, read_fds);

      /* To reduce event loop overhead, read and process as many
       * packets as we can. */
      do {
        if (server->udp_socket == ARES_SOCKET_BAD)
          count = 0;

        else {
          if (server->addr.family == AF_INET)
            fromlen = sizeof(from.sa4);
          else
            fromlen = sizeof(from.sa6);
          count = socket_recvfrom(channel, server->udp_socket, (void *)buf,
                                  sizeof(buf), 0, &from.sa, &fromlen);
        }

        if (count == -1 && try_again(SOCKERRNO))
          continue;
        else if (count <= 0)
          handle_error(channel, i, now);
#ifdef HAVE_RECVFROM
        else if (!same_address(&from.sa, &server->addr))
          /* The address the response comes from does not match the address we
           * sent the request to. Someone may be attempting to perform a cache
           * poisoning attack. */
          break;
#endif
        else
          process_answer(channel, buf, (int)count, i, 0, now);
       } while (count > 0);
    }
}

/* If any queries have timed out, note the timeout and move them on. */
static void process_timeouts(ares_channel channel, struct timeval *now)
{
  time_t t;  /* the time of the timeouts we're processing */
  struct query *query;
  struct list_node* list_head;