Attached is a patch to fix a problem I've been having with the
multi-interface. The problem that I've observed is that if the first name
server is not available, the multi interface does not invoke the socket_cb
when the DNS request to the first name server timesout.
This bug can be reproduced if Curl is complied with --enable_ares and your
code uses the multi socket interfaces and the CURLMOPT_SOCKETFUNCTION
option. The way I test is to set up an iptables rule that discards the
name server reply from the first name server. This forces a timeout and
then cares tries to use the secondary name server. Without the patch, the
client code is never informed of the new socket that cares is using.
To test try:
iptables -I INPUT \
-s $(sed -n -e '/name/{s/.* //p;q}' /etc/resolv.conf)/32 \
-j REJECT
and then run a program which uses the multi-interface
-Jason
From 690738503fbdb3cbf1fb24edd9d25972e2d14206 Mon Sep 17 00:00:00 2001
From: Jason Glasgow <[email protected]>
Date: Wed, 30 Nov 2011 15:23:44 -0500
Subject: [PATCH] multi: handle timeouts on DNS servers by checking for new sockets
If the first name server is not available, the multi interface does
not invoke the socket_cb when the DNS request to the first name server
timesout. Ensure that the list of sockets are always updated after
calling Curl_resolver_is_resolved.
This bug can be reproduced if Curl is complied with --enable_ares and
your code uses the multi socket interfaces and the
CURLMOPT_SOCKETFUNCTION option. To test try:
iptables -I INPUT \
-s $(sed -n -e '/name/{s/.* //p;q}' /etc/resolv.conf)/32 \
-j REJECT
and then run a program which uses the multi-interface.
---
lib/multi.c | 13 ++++++++-----
1 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/lib/multi.c b/lib/multi.c
index ae70851..3059e49 100644
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -1085,12 +1085,15 @@ static CURLMcode multi_runsingle(struct Curl_multi *multi,
/* check if we have the name resolved by now */
easy->result = Curl_resolver_is_resolved(easy->easy_conn, &dns);
- if(dns) {
- /* Update sockets here. Mainly because the socket(s) may have been
- closed and the application thus needs to be told, even if it is
- likely that the same socket(s) will again be used further down. */
- singlesocket(multi, easy);
+ /* Update sockets here, because the socket(s) may have been
+ closed and the application thus needs to be told, even if it
+ is likely that the same socket(s) will again be used further
+ down. If the name has not yet been resolved, it is likely
+ that new sockets have been opened in an attempt to contact
+ another resolver. */
+ singlesocket(multi, easy);
+ if(dns) {
/* Perform the next step in the connection phase, and then move on
to the WAITCONNECT state */
easy->result = Curl_async_resolved(easy->easy_conn,
--
1.7.3.1
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