Periodic SERVFAIL for TLD .BY

Tue Mar 29 15:16:02 UTC 2022

The .by domain is kind of bonkers…

Step 1: get nameservers for 103.by:

$ dig +noall +authority IN NS 103.by. @a.root-servers.net
by.			172800	IN	NS	dns1.tld.becloudby.com.
by.			172800	IN	NS	dns2.tld.becloudby.com.
by.			172800	IN	NS	dns3.tld.becloudby.com.
by.			172800	IN	NS	dns4.tld.becloudby.com.
by.			172800	IN	NS	dns5.tld.becloudby.com.

Step 2: get nameservers for becloudy.com:

$ dig +noall +authority IN NS becloudby.com. @a.root-servers.net
com.			172800	IN	NS	e.gtld-servers.net.
com.			172800	IN	NS	b.gtld-servers.net.
[…]

$ dig +noall +authority IN NS becloudby.com. @a.gtld-servers.net.
becloudby.com.		172800	IN	NS	u1.hoster.by.
becloudby.com.		172800	IN	NS	u2.hoster.by.

Step 3: get nameservers for hoster.by

$ dig +noall +authority IN NS hoster.by. @a.root-servers.net
by.			172800	IN	NS	dns1.tld.becloudby.com.
by.			172800	IN	NS	dns2.tld.becloudby.com.
by.			172800	IN	NS	dns3.tld.becloudby.com.
by.			172800	IN	NS	dns4.tld.becloudby.com.
by.			172800	IN	NS	dns5.tld.becloudby.com.

Step 4: get nameservers for  becloudy.com:

[…]

My guess is that it probably depends on the current state of the cache
whether `named` is able to break out of the loop using the existing data
or not.

From the log, I can see that it’s hitting the SERVFAIL cache.

You can disable the servfail caching with:

``servfail-ttl``
   This sets the number of seconds to cache a SERVFAIL response due to DNSSEC
   validation failure or other general server failure. If set to ``0``,
   SERVFAIL caching is disabled. The SERVFAIL cache is not consulted if
   a query has the CD (Checking Disabled) bit set; this allows a query
   that failed due to DNSSEC validation to be retried without waiting
   for the SERVFAIL TTL to expire.

   The maximum value is ``30`` seconds; any higher value is
   silently reduced. The default is ``1`` second.

And see if that helps.

Ondrej
--
Ondřej Surý (He/Him)
ondrej at isc.org

My working hours and your working hours may be different. Please do not feel obligated to reply outside your normal working hours.

> On 29. 3. 2022, at 16:02, Dzmitry Shykuts <dshykuts at gmail.com> wrote:
> 
> Hello! Can anybody help me with periodic and critical for me SERVFAIL? Cannot determine the source of the problem.
> 
> I have Debian 11.3 and BIND9 9.16.27 on it. There was no such problem earlier.
> 
> I do request:
> 
>  <<>> DiG 9.16.27-Debian <<>> 103.by +trace
> ;; global options: +cmd
> . 518377 IN NS e.root-servers.net.
> . 518377 IN NS a.root-servers.net.
> . 518377 IN NS h.root-servers.net.
> . 518377 IN NS k.root-servers.net.
> . 518377 IN NS b.root-servers.net.
> . 518377 IN NS i.root-servers.net.
> . 518377 IN NS j.root-servers.net.
> . 518377 IN NS d.root-servers.net.
> . 518377 IN NS c.root-servers.net.
> . 518377 IN NS m.root-servers.net.
> . 518377 IN NS f.root-servers.net.
> . 518377 IN NS g.root-servers.net.
> . 518377 IN NS l.root-servers.net.
> . 518377 IN RRSIG NS 8 0 518400 20220411050000 20220329040000 9799 . keszTJZg3TCzY3s4UyinKYe7VwZGGf/8kHoWzJ2Ab3n4ctBt8gtleqC0 UZqIIjc9Ez9srWGGeNn2gRUtB65QvL99oX5gD5VI6h1SY81OC0HcBx2c 80SZJ0s9qpNmkDDcp4EUNlgoheDkBAtB3MsIRIVA6T746gBthcVKLHxC rpOy7ELdgDtHwtq8jL5QIFae6QlIGuO95nflzk31VoL/yhCxvpzIXEfq QJlJQf21YJtAtYnY7vJJwuDVT20y/cj5W7PNxSkNLMoukqUXOeH/w2yB 0yNkwbKLBZUkyrE5tQmlq5AnScofbT7ffOYB9o9ug39DgCTcqSeNZDYX 0Gekmg==
> ;; Received 1137 bytes from 127.0.0.1#53(127.0.0.1) in 3 ms
> 
> by. 172800 IN NS dns5.tld.becloudby.com.
> by. 172800 IN NS dns2.tld.becloudby.com.
> by. 172800 IN NS dns3.tld.becloudby.com.
> by. 172800 IN NS dns4.tld.becloudby.com.
> by. 172800 IN NS dns1.tld.becloudby.com.
> by. 86400 IN DS 495 13 2 2D14284F8E47B53F839BD8068D438680B4B6C7A645769C9D89B47DF0 C5359B7B
> by. 86400 IN RRSIG DS 8 1 86400 20220411050000 20220329040000 9799 . IAk+oEOmuQVbb8RyxB9ML/GOwnLIaQdi0XMD8Y7san2AIx2lXeEZp3AV fNgYQfTnVrGyi3ylXNkVmQXnqDdrPK8iJu6mKvmaI40sQwv8xDyx5Fnz VaNHcY4+J3fQwSp+TrFxQuAlW3g3CFaUVNLk20V/TQUycVA75c+3TrW4 IQJ1aua0lDsG1JS7BigHryUH9Vy8nSyuikYOIiML0BTTTqFQN7yk4AiE 3gbYMuCsMHQKfAIXpswc/i1eGEW7yi5USnQqza4P2YEDrUhSUps5N2u5 /UwdS1BsmW17WZRbfDudeL4y471jwKhYgCCycGI1whtToDA452nvDJL2 it6mlg==
> couldn't get address for 'dns5.tld.becloudby.com': failure
> couldn't get address for 'dns2.tld.becloudby.com': failure
> couldn't get address for 'dns3.tld.becloudby.com': failure
> couldn't get address for 'dns4.tld.becloudby.com': failure
> couldn't get address for 'dns1.tld.becloudby.com': failure
> dig: couldn't get address for 'dns5.tld.becloudby.com': no more
> 
> Request SERVFAILed. When I do "rndc flush" several times, the problem has gone for a while. After some time I get SERVFAIL again. Now I'm forwarding the zone to Google DNS and there is no such problem.
> 
> There is a some debug log from BIND of the problem:
> 
> <named.txt>-- 
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