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

[Nick Howitt]

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)

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?

The only thing I have thought of is to put in a firewall rule blocking 
traffic from 10.10.1.2 to 10.10.1.2:8080 but I fear shooting myself in 
the foot.

Any help would be greatly appreciated.

Nick