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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 
ares_fds(ares_channel channel,fd_set * read_fds,fd_set * write_fds)27 int 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