1
2/* Copyright 1998 by the Massachusetts Institute of Technology.
3 *
4 * Permission to use, copy, modify, and distribute this
5 * software and its documentation for any purpose and without
6 * fee is hereby granted, provided that the above copyright
7 * notice appear in all copies and that both that copyright
8 * notice and this permission notice appear in supporting
9 * documentation, and that the name of M.I.T. not be used in
10 * advertising or publicity pertaining to distribution of the
11 * software without specific, written prior permission.
12 * M.I.T. makes no representations about the suitability of
13 * this software for any purpose.  It is provided "as is"
14 * without express or implied warranty.
15 */
16
17#include "ares_setup.h"
18
19#ifdef HAVE_SYS_TIME_H
20#include <sys/time.h>
21#endif
22
23#include "ares.h"
24#include "ares_nowarn.h"
25#include "ares_private.h"
26
27int ares_fds(ares_channel channel, fd_set *read_fds, fd_set *write_fds)
28{
29  struct server_state *server;
30  ares_socket_t nfds;
31  int i;
32
33  /* Are there any active queries? */
34  int active_queries = !ares__is_list_empty(&(channel->all_queries));
35
36  nfds = 0;
37  for (i = 0; i < channel->nservers; i++)
38    {
39      server = &channel->servers[i];
40      /* We only need to register interest in UDP sockets if we have
41       * outstanding queries.
42       */
43      if (active_queries && server->udp_socket != ARES_SOCKET_BAD)
44        {
45          FD_SET(server->udp_socket, read_fds);
46          if (server->udp_socket >= nfds)
47            nfds = server->udp_socket + 1;
48        }
49      /* We always register for TCP events, because we want to know
50       * when the other side closes the connection, so we don't waste
51       * time trying to use a broken connection.
52       */
53      if (server->tcp_socket != ARES_SOCKET_BAD)
54       {
55         FD_SET(server->tcp_socket, read_fds);
56         if (server->qhead)
57           FD_SET(server->tcp_socket, write_fds);
58         if (server->tcp_socket >= nfds)
59           nfds = server->tcp_socket + 1;
60	}
61    }
62  return (int)nfds;
63}
64