[Pdns-users] How to set up pdns recursor to repeat the query if it does not get an answer
krejci at i3.cz
Wed Sep 23 14:27:14 UTC 2020
would it be possible to solve the problem by querying the authoritative
server via the TCP protocol? If so, how to do this in the recursor
configuration (whether for a specific domain or globally)?
Dne 23. 09. 20 v 9:23 Thomas Mieslinger via Pdns-users napsal(a):
> In my opinion this needs to be fixed at the authoritative end.
> These repeated recursive queries tend to produce retry waves. So
> recursors would need to implement a quadratic backoff or similar.
> Just from my mind... I took over authoritative DNS for a hoster. They
> claimed to have ddos problems. In reality they just restarted their
> auths and the whole internet started to retry. Then a 100k or 200k req/s
> retry wave hit the auths.
> I'm doing this differently so that recursor do not start to retry and
> have not to deal with waves.
> On 18.09.20 17:42, Winfried Angele via Pdns-users wrote:
>> Hi Mira,
>> I think if a Resolver retries on possibly overloaded or attacked
>> authoritative DNS servers, it gets even worse for them. So I'd recommend
>> to try to contact the people in charge for that domain and try to
>> convince them to solve the problem on their side. And again, the
>> Recursor tries on each Nameservers address listed in the NS RRset. So it
>> does retries, but not on the same address. That means, in your case, all
>> DNS servers of that domain are overloaded or broken or attacked.
>> Am 18. September 2020 16:05:04 MESZ schrieb Mira Krejci <krejci at i3.cz>:
>> Hi Winfried,
>> thank you for your reply.
>> If it's a feature and can't be changed, I have a big problem that
>> I'll have to solve by changing the software to another.
>> For example, Bind asks more than once if answer does not come. Users
>> are angry that DNS resolving does not work for them (of course, it
>> is to blame for authoritative servers of a specific domain).
>> But I have to solve it somehow.
>> Dne 18. 09. 20 v 15:34 Winfried Angele napsal(a):
>>> Hi Mira,
>>> Yes the Recursor does no retry on *this* auth. But it tries on the
>>> other nameservers from the NS RR set. IPv4 and IPv6. So if you
>>> have only one auth, Recursor tries two times, IPv4 and IPv6 if
>>> Am 18. September 2020 14:47:49 MESZ schrieb Mira Krejci via
>>> Pdns-users <pdns-users at mailman.powerdns.com>:
>>> I have a problem that I can't force the pdns recursor to
>>> query the
>>> authoritative servers repeatedly if they do not answer.
>>> Recursor tries
>>> the query only once and then return an error (SERVFAIL) to
>>> the client.
>>> This is very problematic when the authoritative server is
>>> overloaded or
>>> there are some problems on the network. I didn't find any
>>> way in the
>>> configuration to change it.
>>> Server version: 4.2.2-1 (from EPEL repo on CentOS 8)
>>> Can anyone help?
>>> Pdns-users mailing list
>>> Pdns-users at mailman.powerdns.com
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