[squid-users] Another "Forwarding loop detected" issue

[Amos Jeffries]

On 5/11/19 10:40 pm, Nick Howitt wrote:
> I am trying to help someone who is running squid-3.5.20-12 on a
> standalone server with the dansguardian content filter and suddenly
> recently has been getting a lot of messages like:
> 
>    2019/10/31 13:48:14 kid1| WARNING: Forwarding loop detected for:
>    HEAD / HTTP/1.0
>    Via: 1.0 HSFilterHyperos7.haftr.local (squid/3.5.20)
>    Cache-Control: max-age=259200
>    Connection: keep-alive
>    X-Forwarded-For: 10.10.1.2
>    Host: 10.10.1.2:8080
> 
> 
> The access log looks something like:
> 
>    1572545946.383 120000 10.10.1.2 TCP_MISS_ABORTED/000 0 HEAD
>    http://10.10.1.2:8080/ - HIER_DIRECT/10.10.1.2 -
>    1572545946.477 120000 10.10.1.2 TCP_MISS_ABORTED/000 0 HEAD
>    http://10.10.1.2:8080/ - HIER_DIRECT/10.10.1.2 -
>    1572545946.493 120000 10.10.1.2 TCP_MISS_ABORTED/000 0 HEAD
>    http://10.10.1.2:8080/ - HIER_DIRECT/10.10.1.2 -
> 
> (but these are for different transactions - they are all the same apart
> from the timestamps)
> 

That is what a forwarding loop looks like in the access.log.


> The content filter listens on port 8080 and squid on 3128. The machine
> is on 10.10.1.2
> 
> All the other posts I've seen seem to be for transparent mode or where
> there is a User Agent string. I have found nothing to cover this
> scenario. How can I troubleshoot to fix it and what information do you
> need from me to help diagnose?
> 

Something is telling Squid the origin server being contacted exists at
10.10.1.2:8080. You can see that in the Host header of the message.

I would trace the traffic flow from the client to Squid.

Amos