From 3d9e52ac5661fda80d2967df22a22a4d92fd1cdf Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Tue, 1 May 2012 19:52:55 -0400
Subject: [PATCH] When retransmitting a timed-out DNS request, pick a fresh
 nameserver.

Otherwise, requests initially sent to a failing nameserver would
stay there indefinitely, even if other nameservers would work.

Fix for sourceforge bug 3518439
---
 evdns.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/evdns.c b/evdns.c
index 72e44673..ed2dbdc5 100644
--- a/evdns.c
+++ b/evdns.c
@@ -2161,9 +2161,13 @@ evdns_request_timeout_callback(evutil_socket_t fd, short events, void *arg) {
 		request_finished(req, &REQ_HEAD(req->base, req->trans_id), 1);
 	} else {
 		/* retransmit it */
+		struct nameserver *new_ns;
 		log(EVDNS_LOG_DEBUG, "Retransmitting request %p; tx_count==%d",
 		    arg, req->tx_count);
 		(void) evtimer_del(&req->timeout_event);
+		new_ns = nameserver_pick(base);
+		if (new_ns)
+			req->ns = new_ns;
 		evdns_request_transmit(req);
 	}
 	EVDNS_UNLOCK(base);