ares: remove fd from multi fd set when ares is about to close the fd

When using c-ares for asyn dns, the dns socket fd was silently closed
by c-ares without curl being aware. curl would then 'realize' the fd
has been removed at next call of Curl_resolver_getsock, and only then
notify the CURLMOPT_SOCKETFUNCTION to remove fd from its poll set with
CURL_POLL_REMOVE. At this point the fd is already closed.

By using ares socket state callback (ARES_OPT_SOCK_STATE_CB), this
patch allows curl to be notified that the fd is not longer needed
for neither for write nor read. At this point by calling
Curl_multi_closed we are able to notify multi with CURL_POLL_REMOVE
before the fd is actually closed by ares.

In asyn-ares.c Curl_resolver_duphandle we can't use ares_dup anymore
since it does not allow passing a different sock_state_cb_data

Closes #3238

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/connect.c b/lib/connect.c
index 41f220268..18645b9b7 100644
--- a/lib/connect.c
+++ b/lib/connect.c
@@ -1314,7 +1314,7 @@ int Curl_closesocket(struct connectdata *conn,
       conn->sock_accepted[SECONDARYSOCKET] = FALSE;
     else {
       int rc;
-      Curl_multi_closed(conn, sock);
+      Curl_multi_closed(conn->data, sock);
       Curl_set_in_callback(conn->data, true);
       rc = conn->fclosesocket(conn->closesocket_client, sock);
       Curl_set_in_callback(conn->data, false);
@@ -1324,7 +1324,7 @@ int Curl_closesocket(struct connectdata *conn,
 
   if(conn)
     /* tell the multi-socket code about this */
-    Curl_multi_closed(conn, sock);
+    Curl_multi_closed(conn->data, sock);
 
   sclose(sock);