Nick Mathewson added the ARES_OPT_SOCK_STATE_CB option that when set makes

c-ares call a callback on socket state changes. A better way than the
ares_getsock() to get full control over the socket state.

ares/ares_init.3

@@ -98,6 +98,24 @@ The lookups to perform for host queries.
 .I lookups
 should be set to a string of the characters "b" or "f", where "b"
 indicates a DNS lookup and "f" indicates a lookup in the hosts file.
+.TP 18
+.B ARES_OPT_SOCK_STATE_CB
+.B void (*\fIsock_state_cb\fP)(void *data, int s, int read, int write);
+.br
+.B void *\fIsock_state_cb_data\fP;
+.br
+A callback function to be invoked when a socket changes state.
+.I s
+will be passed the socket whose state has changed;
+.I read
+will be set to true if the socket should listen for read events, and
+.I write
+will be set to true if the socket should listen for write events.
+The value of
+.I sock_state_cb_data
+will be passed as the
+.I data
+argument.
 .PP
 The
 .I flags