Commit 06484eb5 authored by Dhalgren's avatar Dhalgren Committed by Nick Mathewson
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Bug 21394 touchup: Increase DNS attempts to 3

Also don't give up on a resolver as quickly if multiple are configured.
parent 4bb7d9fd
o Minor bugfix (Exit node DNS retries):
- Re-attempt timed-out DNS queries 3 times before failure, since our
timeout is 5 seconds for them, but clients wait 10-15. Also allow
slightly more timeouts per resolver before giving up on it in the
case where an exit has multiple resolvers configured. Fixes bug 21394;
bugfix on 0.3.1.9.
......@@ -1428,27 +1428,30 @@ configure_nameservers(int force)
// If we only have one nameserver, it does not make sense to back off
// from it for a timeout. Unfortunately, the value for max-timeouts is
// currently clamped by libevent to 255, but it does not hurt to set
// it higher in case libevent gets a patch for this.
// Reducing attempts in the case of just one name server too, because
// it is very likely to be a local one where a network connectivity
// issue should not cause an attempt to fail.
// it higher in case libevent gets a patch for this. Higher-than-
// default maximum of 3 with multiple nameservers to avoid spuriously
// marking one down on bursts of timeouts resulting from scans/attacks
// against non-responding authoritative DNS servers.
if (evdns_base_count_nameservers(the_evdns_base) == 1) {
SET("max-timeouts:", "1000000");
SET("attempts:", "1");
} else {
SET("max-timeouts:", "3");
SET("max-timeouts:", "10");
}
// Elongate the queue of maximum inflight dns requests, so if a bunch
// time out at the resolver (happens commonly with unbound) we won't
// remain pending at the resolver (happens commonly with Unbound) we won't
// stall every other DNS request. This potentially means some wasted
// CPU as there's a walk over a linear queue involved, but this is a
// much better tradeoff compared to just failing DNS requests because
// of a full queue.
SET("max-inflight:", "8192");
// Time out after 5 seconds if no reply.
// Two retries at 5 and 10 seconds for bind9/named which relies on
// clients to handle retries. Second retry for retried circuits with
// extended 15 second timeout. Superfluous with local-system Unbound
// instance--has its own elaborate retry scheme.
SET("timeout:", "5");
SET("attempts:","3");
if (options->ServerDNSRandomizeCase)
SET("randomize-case:", "1");
......
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