Re: [squid-users] Any guidelines on writing external_acl_type s?

On Tuesday 29 July 2003 17.48, Chris Wilcox wrote:

> I've had a good search through google and found nothing. Are there
> any limits or things that can't be done with this type of ACL? Eg
> can the helper class query a DB, can it be written in any language?
> Can it be a simple perl script?

Squid does not care. As long as the helper is capable of reading lines
of input according to your external_acl_type specification and give
OK/ERR responses back (optionally with extra information, see
squid.conf notes)

There is however limitations on where acl types requiring external
lookups (external, dst, srcdomain, ident etc) can be used. Such acl
types can only be used in "blocking" access directives. The
"blocking" access directives currently are (Squid-2.5):

   http_access
   no_cache
   always_direct
   never_direct

Use of acl types requiring any form of external lookup in other
directives will not always work in other directives, but in many
cases acceptable levels can be found (if a few false negatives is
acceptable) by making sure the acl is first evaluated in http_access,
allowing Squid to cache the result of the acl.

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