[squid-users] Making destination IP available in ICAP REQMOD request

[Alex Rousskov]

On 1/17/21 5:28 PM, Moti Berger wrote:
> I couldn't figure out a way to start the DNS resolving just before
> the startAdaptation starts as it requires all sorts of objects that seem
> to be unavailable there.

Please ask development questions on squid-dev:
http://www.squid-cache.org/Support/mailing-lists.html#squid-dev

Triggering a DNS lookup before REQMOD is easy, but waiting for its
asynchronous result requires a bit of development work outside this
mailing list scope.

More importantly, a DNS lookup alone is probably not enough. If your
REQMOD service relies on the destination address that Squid will use
when/if forwarding the request, then Squid should be modified to
(optionally) decide on the forwarding destination first, _before_
adapting the request and then, to the extent possible, stick with that
original decision after REQMOD. This may be equivalent to implementing
post-cache REQMOD!

It is possible to implement all that, and there are legitimate use cases
that would benefit from such functionality, but a quality implementation
will require serious development work. If you are sure that you need
this functionality, and you want to implement it yourself, then I
recommend starting with an RFC on squid-dev:
https://wiki.squid-cache.org/MergeProcedure#Before_you_start_coding


HTH,

Alex.