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, 4 insertions, 4 deletions

diff --git a/lib/multi.c b/lib/multi.c
index 0db2a9730..fbd389716 100644
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -2466,11 +2466,11 @@ void Curl_updatesocket(struct Curl_easy *data)
  * socket again and it gets the same file descriptor number.
  */
 
-void Curl_multi_closed(struct connectdata *conn, curl_socket_t s)
+void Curl_multi_closed(struct Curl_easy *data, curl_socket_t s)
 {
-  if(conn->data) {
+  if(data) {
     /* if there's still an easy handle associated with this connection */
-    struct Curl_multi *multi = conn->data->multi;
+    struct Curl_multi *multi = data->multi;
     if(multi) {
       /* this is set if this connection is part of a handle that is added to
          a multi handle, and only then this is necessary */
@@ -2478,7 +2478,7 @@ void Curl_multi_closed(struct connectdata *conn, curl_socket_t s)
 
       if(entry) {
         if(multi->socket_cb)
-          multi->socket_cb(conn->data, s, CURL_POLL_REMOVE,
+          multi->socket_cb(data, s, CURL_POLL_REMOVE,
                            multi->socket_userp,
                            entry->socketp);