When I queried the authoritative server directly it worked:

;; QUESTION SECTION:
;111.250.179.17.in-addr.arpa.   IN      PTR

;; ANSWER SECTION:
111.250.179.17.in-addr.arpa. 86400 IN   PTR     rn2-msbadger07105.apple.com.

;; Query time: 62 msec
;; SERVER: 17.47.176.10#53(17.47.176.10)

I would recommend that you too do a dig @ and see what you get.

If it works then you can start examining your on prim configs .. if it does not 
work then you need to be using wireshark to figure out what is happening to the 
traffic.

Either way you need to first break your troubleshooting into two parts .. on 
prim vs off prim and proceed from there.

Good hunting.

John

-----Original Message-----
From: bind-users [mailto:bind-users-boun...@lists.isc.org] On Behalf Of Julien 
Salort
Sent: Thursday, March 25, 2021 12:11 PM
To: bind-users@lists.isc.org
Subject: Timeout setting

Hello,


I have a VPS running postfix and bind9. Bind is used as a recursive resolver, 
in particular to be able to query anti-spam database.

Postfix is also configured to reject incoming connections from servers with no 
reverse dns.

It works great overall, but sometimes legitimate messages get rejected because 
the reverse dns query fails.

Here is an example (anonymized email and host address):

In mail.log:

450 4.7.1 Client host rejected: cannot find your reverse hostname, 
[17.179.250.111]; from=<developer_boun...@insideapple.apple.com>
to=<x...@example.com> proto=ESMTP helo=<rn2-msbadger07105.apple.com>
(total: 1)

In named journal:

mars 02 01:14:20 example.com named[2756114]: client @0x7f3a0808c750
127.0.0.1#43646 (111.250.179.17.in-addr.arpa): query: 
111.250.179.17.in-addr.arpa IN PTR +E(0) (127.0.0.1)

mars 02 01:14:25 example.com named[2756114]: client @0x7f3a08079d00
127.0.0.1#43646 (111.250.179.17.in-addr.arpa): query: 
111.250.179.17.in-addr.arpa IN PTR +E(0) (127.0.0.1)

mars 02 01:14:32 example.com named[2756114]: client @0x7f3a0808c750
127.0.0.1#43646 (111.250.179.17.in-addr.arpa): query failed (timed out) for 
111.250.179.17.in-addr.arpa/IN/PTR at query.c:6883

mars 02 01:14:32 example.com named[2756114]: client @0x7f3a000d5110
127.0.0.1#49520 (insideapple.apple.com): query: insideapple.apple.com IN MX + 
(127.0.0.1)


So there is a timeout.

Now if I try again:

$ dig -x 17.179.250.111 @localhost +short rn2-msbadger07105.apple.com.


So it seems that it is just that sometimes the query takes a bit longer...


Is there a general advice regarding timeout for bind?

Should I just choose a longer timeout? Or is there a reason for the default 
value?


I did not have such problems when I was using the ISP dns server instead 
of a local recursive resolver. So I was wondering if the configuration 
is sub-optimal somehow...


Thank you,


Cheers,


Julien


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