/* $Id: ares_fds.c,v 1.12 2009-11-02 11:55:53 yangtse Exp $ */ /* Copyright 1998 by the Massachusetts Institute of Technology. * * Permission to use, copy, modify, and distribute this * software and its documentation for any purpose and without * fee is hereby granted, provided that the above copyright * notice appear in all copies and that both that copyright * notice and this permission notice appear in supporting * documentation, and that the name of M.I.T. not be used in * advertising or publicity pertaining to distribution of the * software without specific, written prior permission. * M.I.T. makes no representations about the suitability of * this software for any purpose. It is provided "as is" * without express or implied warranty. */ #include "ares_setup.h" #ifdef HAVE_SYS_TIME_H #include <sys/time.h> #endif #include "ares.h" #include "ares_private.h" int ares_fds(ares_channel channel, fd_set *read_fds, fd_set *write_fds) { struct server_state *server; ares_socket_t nfds; int i; /* Are there any active queries? */ int active_queries = !ares__is_list_empty(&(channel->all_queries)); nfds = 0; for (i = 0; i < channel->nservers; i++) { server = &channel->servers[i]; /* We only need to register interest in UDP sockets if we have * outstanding queries. */ if (active_queries && server->udp_socket != ARES_SOCKET_BAD) { FD_SET(server->udp_socket, read_fds); if (server->udp_socket >= nfds) nfds = server->udp_socket + 1; } /* We always register for TCP events, because we want to know * when the other side closes the connection, so we don't waste * time trying to use a broken connection. */ if (server->tcp_socket != ARES_SOCKET_BAD) { FD_SET(server->tcp_socket, read_fds); if (server->qhead) FD_SET(server->tcp_socket, write_fds); if (server->tcp_socket >= nfds) nfds = server->tcp_socket + 1; } } return (int)nfds; }