ares_socket_t *socks = (ares_socket_t *)s;
- /* No queries, no file descriptors. */
- if (ares__is_list_empty(&(channel->all_queries)))
- return 0;
+ /* Are there any active queries? */
+ int active_queries = !ares__is_list_empty(&(channel->all_queries));
for (i = 0;
(i < channel->nservers) && (sockindex < ARES_GETSOCK_MAXNUM);
i++)
{
server = &channel->servers[i];
- if (server->udp_socket != ARES_SOCKET_BAD)
+ /* We only need to register interest in UDP sockets if we have
+ * outstanding queries.
+ */
+ if (active_queries && server->udp_socket != ARES_SOCKET_BAD)
{
if(sockindex >= numsocks)
break;
bitmap |= ARES_GETSOCK_READABLE(setbits, sockindex);
sockindex++;
}
+ /* 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)
{
if(sockindex >= numsocks)
socks[sockindex] = server->tcp_socket;
bitmap |= ARES_GETSOCK_READABLE(setbits, sockindex);
- if (server->qhead)
+ if (server->qhead && active_queries)
/* then the tcp socket is also writable! */
bitmap |= ARES_GETSOCK_WRITABLE(setbits, sockindex);