src/lib/legacy/ares_fds.c

/* MIT License
 *
 * Copyright (c) 1998 Massachusetts Institute of Technology
 * Copyright (c) The c-ares project and its contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * SPDX-License-Identifier: MIT
 */

#include "ares_private.h"

int ares_fds(const ares_channel_t *channel, fd_set *read_fds, fd_set *write_fds)
{
  ares_socket_t      nfds;
  ares_slist_node_t *snode;
  /* Are there any active queries? */
  size_t             active_queries;

  if (channel == NULL || read_fds == NULL || write_fds == NULL) {
    return 0;
  }

  ares_channel_lock(channel);

  active_queries = ares_llist_len(channel->all_queries);

  nfds = 0;
  for (snode = ares_slist_node_first(channel->servers); snode != NULL;
       snode = ares_slist_node_next(snode)) {
    ares_server_t     *server = ares_slist_node_val(snode);
    ares_llist_node_t *node;

    for (node = ares_llist_node_first(server->connections); node != NULL;
         node = ares_llist_node_next(node)) {
      const ares_conn_t *conn = ares_llist_node_val(node);

      if (!active_queries && !(conn->flags & ARES_CONN_FLAG_TCP)) {
        continue;
      }

      /* Silence coverity, shouldn't be possible */
      if (conn->fd == ARES_SOCKET_BAD) {
        continue;
      }

      /* Always wait on read */
      FD_SET(conn->fd, read_fds);

      if (conn->fd >= nfds) {
        nfds = conn->fd + 1;
      }

      /* TCP only wait on write if we have the flag set */
      if (conn->state_flags & ARES_CONN_STATE_WRITE) {
        FD_SET(conn->fd, write_fds);
      }
    }
  }

  ares_channel_unlock(channel);
  return (int)nfds;
}