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| author | Kai Krakow <kai@kaishome.de> | 2017-05-13 12:30:56 +0200 |
|---|---|---|
| committer | Lennart Poettering <lennart@poettering.net> | 2017-06-27 22:04:16 +0200 |
| commit | 496ae8c84b2d3622bc767a727e3582e2b6bcffcd (patch) | |
| tree | 83e00059ea9ff8034625f5c565a5d8b36f4d1e36 /src/resolve | |
| parent | 9af868392bb8ceb50afc6b5028786dc266888dea (diff) | |
| download | systemd-496ae8c84b2d3622bc767a727e3582e2b6bcffcd.tar.gz | |
resolved: Recover from slow DNS responses
When DNS is unreliable temporarily, the current implementation will
never improve resend behavior again and switch DNS servers only late
(current maximum timeout is 5 seconds).
We can improve this by biasing the resend_timeout back to the current
RTT when a successful response was received. Next time, a timeout is hit
on this server, it will switch to the next server faster.
Fixes: #5953
Diffstat (limited to 'src/resolve')
| -rw-r--r-- | src/resolve/resolved-dns-server.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/src/resolve/resolved-dns-server.c b/src/resolve/resolved-dns-server.c index 63cb6a5bda..9c3ee0136c 100644 --- a/src/resolve/resolved-dns-server.c +++ b/src/resolve/resolved-dns-server.c @@ -304,7 +304,10 @@ void dns_server_packet_received(DnsServer *s, int protocol, DnsServerFeatureLeve if (s->max_rtt < rtt) { s->max_rtt = rtt; s->resend_timeout = CLAMP(s->max_rtt * 2, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); - } + } else if (s->resend_timeout > rtt) + /* If we received the packet faster than the resend_timeout, bias + * the resend_timeout back to the rtt. */ + s->resend_timeout = CLAMP((2 * s->resend_timeout + rtt) / 3, DNS_TIMEOUT_MIN_USEC, DNS_TIMEOUT_MAX_USEC); } void dns_server_packet_lost(DnsServer *s, int protocol, DnsServerFeatureLevel level, usec_t usec) { |