Maintained by: NLnet Labs

unbound flooding syslog with 'sendto failed: Cannot assign requested address'

Hendrik Jaeger
Fri Oct 16 12:47:09 CEST 2015


Hi,

I’m running unbound 1.4.22 from debian unstable on my laptop.
Since yesterday unbound started behaving strangely, flooding the syslog
with failure messages. Example:
Oct 16 10:23:20 frustcomp unbound: [26958:0] notice: sendto failed: Cannot assign requested address
Oct 16 10:23:20 frustcomp unbound: [26958:0] notice: remote address is 2001:500:3::42 port 53

The pattern is always the same: 'sendto failed' followed by 'remote
address is' with varying IPv6 addresses. You can find full unbound-logs
for yesterday in [0], created using this command:
grep 'unbound' /var/log/syslog.1 > /tmp/unbound_failures.log
(Careful: this file is 339M big and has 3642512 lines.)

IPv6 is disabled on this system, it has neither an IPv6 address on any
interface nor a route set.

Today I tried just restarting unbound and that failed as well:
# service unbound restart
Restarting recursive DNS server: unbound[1444991903] unbound[22562:0] error: can't bind socket: Cannot assign requested address
[1444991903] unbound[22562:0] debug: failed address ::1 port 8953
[1444991903] unbound[22562:0] error: cannot open control interface ::1 8953
[1444991903] unbound[22562:0] fatal error: could not open ports
 failed!

# ss -apen | grep 8953
returns nothing listening on that port, just to make sure that’s not
the problem. Since the message refers to 'requested address' and
probably means ::1, I doubt it is. ::1 is not configured on any
interface, as IPv6 is disabled.

I can’t figure out either of these problems, and I’m not sure if they
are related but the timing seems to suggest that.

Can anyone help me understand any of the error messages please? What
might cause them? Why do they appear on a system without IPv6
configured?

Please tell me (off-list maybe) what other info I should provide.

Thank you very much.

Sincerely

henk

[0]: http://henk.hnjs.ch/20151015_unbound_failures.txt

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