Good Evening,
After running for some amount of time (seems to be days), our dnsdist instances
suddenly start trying to talk to the backends using the loopback address as the
source:
# tcpdump -i ens192 -nn port 53
dropped privs to tcpdump
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on ens192, link-type EN10MB (Ethernet), capture size 262144 bytes
22:39:07.014963 IP6 <snip>:ac10:0:ac10:2e.64975 > <snip>::197.53: 35980+
[1au] SOA? lbdn.domain. (45)
22:39:07.015390 IP6 ::1.38717 > <snip>::195.53: 43034 [1au] SOA?
lbdn.domain. (69)
Note this is not the loopback interface - packets are being placed on the wire
and fired off into the network with ::1 as the source address. This is
affecting all our instances, but they don't fail simultaneously.
Bizarrely, this only affects queries made by clients - the backend health check
still uses the correct source address while this is going on. Restarting
dnsdist brings them back into service.
I think I can work around this by setting an explicit source IP for each
backend - I'm suspecting that trying to talk to backends with the return
address set to ::1 is probably a bug though!
We're running the current master branch builds on RHEL8.
Adam Bishop
gpg: E75B 1F92 6407 DFDF 9F1C BF10 C993 2504 6609 D460
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