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 #include "ares.h"
20 #include "ares_nowarn.h"
21 #include "ares_private.h"
22
ares_fds(ares_channel channel,fd_set * read_fds,fd_set * write_fds)23 int ares_fds(ares_channel channel, fd_set *read_fds, fd_set *write_fds)
24 {
25 struct server_state *server;
26 ares_socket_t nfds;
27 int i;
28
29 /* Are there any active queries? */
30 int active_queries = !ares__is_list_empty(&(channel->all_queries));
31
32 nfds = 0;
33 for (i = 0; i < channel->nservers; i++)
34 {
35 server = &channel->servers[i];
36 /* We only need to register interest in UDP sockets if we have
37 * outstanding queries.
38 */
39 if (active_queries && server->udp_socket != ARES_SOCKET_BAD)
40 {
41 FD_SET(server->udp_socket, read_fds);
42 if (server->udp_socket >= nfds)
43 nfds = server->udp_socket + 1;
44 }
45 /* We always register for TCP events, because we want to know
46 * when the other side closes the connection, so we don't waste
47 * time trying to use a broken connection.
48 */
49 if (server->tcp_socket != ARES_SOCKET_BAD)
50 {
51 FD_SET(server->tcp_socket, read_fds);
52 if (server->qhead)
53 FD_SET(server->tcp_socket, write_fds);
54 if (server->tcp_socket >= nfds)
55 nfds = server->tcp_socket + 1;
56 }
57 }
58 return (int)nfds;
59 }
60