Re: [RFC] Breaking forwarding loops

On 12/01/11 13:53, Alex Rousskov wrote:
> On 01/07/2011 06:04 PM, Amos Jeffries wrote:
>
>> Note that a great many hostnames are "localhost" or
>> "localhost.localdomain" or "localhost.local" due to certain distros
>> hard-coding "localhost" into their packages.
>>
>> We also use "localhost" as a backup when the gethostname() call fails to
>> provide anything with rDNS. (IMO that hard rDNS requirement is a bit naive)
>
> Good point!
>
> On 01/11/2011 01:16 AM, Henrik Nordström wrote:
>> A proposal is to always return an error if Via indicates
>> that we have already processed this request twice
>> (on third time the same request is received). This will break actual
>> loops, while keeping sibling loops silent.
>
> Sounds like a good approach to me. I would even take it a few steps
> further to address Amos concern using the same technique. How about this
> plan:
>
> If we have detected a forwarding loop and our name appeared N times,
> then respond with an error provided at least one of the conditions below
> is true:
>
> 1) N> 2 and our name is not localhost or similar.
> 2) N> 10.
>
> No checks for the port mode or transaction flags (intercepted,
> accelerated, etc.).
>
> In addition to the above, do a startup check for the name and warn the
> user if our name is localhost or similar.

I've done a quick search and failed to find the patch I made for this
(bug 2654). Please go ahead with just the warning anyway, I'll resolve
any conflict when I get back into the bug fix.

As for the >10. why 10 and not 1000? or 5?

Consider: what is the use case for allowing a request through the same
Squid three times?
  the only valid one as Henrik said was peer loops by accident. Due to
us not checking if the source IP matches the peer IP. This is resolved
on loop #2 by not passing to peers if we have already looped. So
breaking on 3 makes a strong case.

Amos

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