[squid-users] Squid 4.9 Client IP PTR lookup on connect

Amos Jeffries squid3 at treenet.co.nz
Sun Dec 1 08:15:30 UTC 2019

On 1/12/19 6:31 am, Alex Rousskov wrote:
> On 11/29/19 11:43 AM, Amos Jeffries wrote:
>> The PTR should only need to be looked up at all if something needs to
>> use the client FQDN. Usually that is logging. I suspect your build
>> auto-enabled ICAP features which uses the FQDN for icap_log.
> ... but icap_log is disabled by default, even in Squid builds that have
> ICAP support enabled, right? If a disabled icap_log triggers DNS
> lookups, there is a Squid bug we should fix.

I thought so. But something is turning on log_fqdn, there are no ACLs or
logformat lines in that config. Which leaves us the default settings, of
which only icap_log format uses %<A these days.

> FWIW, the easiest way to figure out what triggered the lookup could be
> to start Squid in a debugger, and then, before starting the test
> transaction, add a breakpoint for fqdncache_nbgethostbyaddr. Post a
> stack trace from that function (when it is triggered after the
> httpAccept line is logged as shown in your cache.log).



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