TCP backlog exceeded with bind 9.16.0
Craig Leres
bind-workers-post at ee.lbl.gov
Mon Mar 16 17:56:14 UTC 2020
Since 9.14 reaches EOL soon, we recently switch to 9.16. Several times
since then is has been necessary to restart the zone master named
because it starts rejecting TCP connections (breaking zone transfers
among other things). When this happens netstat shows a bunch of
established connections with no pending data:
Proto Recv-Q Send-Q Local Address Foreign Address
(state)
tcp4 0 0 131.243.???.???.53 ???.???.???.???.2223
ESTABLISHED
And also some non-zero receive queues in close_wait or closed states:
tcp4 66 0 131.243.???.???.53 ???.???.???.???.37998
CLOSED
tcp4 66 0 131.243.???.???.53 ???.???.???.???.29349
CLOSE_WAIT
Finally, the TCP listen queue for named's public ip has more connections
queued than the TCP backlog:
Current listen queue sizes (qlen/incqlen/maxqlen)
Proto Listen Local Address
tcp4 16/0/10 131.243.???.???.53
Which is why new TCP connections are being refused.
Is anybody else seeing this?
Craig
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