[squid-users] Fwd: cache_peer_access by dynamic ACL

Alex Rousskov rousskov at measurement-factory.com
Wed Apr 26 13:34:38 UTC 2023


On 4/26/23 08:08, Alexeyяр Gruzdov wrote:
> Oh... Looks like I just need to send as answer the list of my policy 
> acl, for example
> 
> user1 wanted to go over peer1 and peer3
> the answer from external script must be like  "OK proxy=peer1 
> proxy=peer3"  and looks like it works well like I need. User will go 
> over peer1 and peer3 only by round-robin.

Instead of sending N same-name annotations to Squid, please try sending 
one annotation with a coma-separated list of N values:

     proxy=peer1,peer3,peer4

Rationale: Even if your current N-annotation setup "works", it is 
essentially relying on undefined and/or questionable behavior that may 
change. Using N-value annotations, you are avoiding that problem.

The "note" ACL has -m option that tells Squid to interpret the 
annotation value as a list:

     acl cleared_for_peer1 note -m proxy peer1
     acl cleared_for_peer2 note -m proxy peer2
     ...


And, again, avoid using "proxy" as the annotation name: That name is 
currently reserved for Squid own use. Use "proxy_" or any other name 
ending with an underscore character. IMO, we should change the 
policy/code to be more admin-friendly, but that change may not happen 
for a long time, and modern Squids will warn you about reserved names 
like "proxy": 
https://github.com/squid-cache/squid/commit/27c36771bf145c2f8ca1efab6743b9e087867ab5


HTH,

Alex.


> ср, 26 апр. 2023 г. в 15:40, Alexeyяр Gruzdov:
> 
>     Hello!
>     Yes!
>     Thank you!
> 
> 
>     One more question pls:
> 
>     For example I have five of cache_peers and ACL associated  with some
>     cache peer.
>     As you know - I used the my external ACL script and now I can put
>     the policy to answer fo my script and squid will get an answer and
>     used the correct ACL for username.
>     For example answer is  "OK  proxy=peer1"  and user will be used the
>     cache_peer1, or if "OK proxy=all" and user will go over all of
>     cache_peers by round-robin.
>     All works well.
>     But how I can put something like a list of ACL for user ?  for
>     example  I want that some one user can go over peer1 and peer3 only,
>     by round robin, but will be denied over peer2. peer4, peer5. Of
>     course better using external ACL (as DB ). What do you think?
> 
> 
> 
> 
> 
> 
>     пн, 24 апр. 2023 г. в 18:07, Alex Rousskov
>     <rousskov at measurement-factory.com
>     <mailto:rousskov at measurement-factory.com>>:
> 
>         On 4/23/23 14:28, Alexeyяр Gruzdov wrote:
> 
>          > One more may be last thing:  - I found the strange behavior 
>         - if I make
>          > changes at my ext ACL script (its python ) and then "squid -k
>          > reconfigure"  then I can see that my script appears in the
>         "TOP" of
>          > process and loads CPU to 100%
> 
>         Check how your ACL script reacts to stdin closure/EOF. The
>         script should
>         quit but probably does not. Same for any stdin reading errors.
>         On EOF,
>         the script should use exit code zero. All these things are easy
>         to test
>         on the command line (without Squid).
> 
>         Alex.
> 
>          > вс, 23 апр. 2023 г. в 16:36, Amos Jeffries
>         <squid3 at treenet.co.nz <mailto:squid3 at treenet.co.nz>
>          > <mailto:squid3 at treenet.co.nz <mailto:squid3 at treenet.co.nz>>>:
>          >
>          >     On 23/04/2023 5:27 pm, Alexeyяр Gruzdov wrote:
>          >      > Hello Guys!
>          >      > Thank you very much! For now all works like I needed!
>          >      >
>          >      > But I have an one more  questions about how I could to
>         use the
>          >     kv-pair:
>          >     ...
>          >      > and then ACL with “note proxy all “
>          >      > But how the kv-pair must to be looked for this my tag ?
>          >      >
>          >      > I have tried to get answer from my ext script like
>          >      > “OK”
>          >      > “proxy=all”
>          >      >
>          >      > But looks like it’s not correct
>          >      >
>          >
>          >     This part of the instructions were missed:
>          >
>         https://wiki.squid-cache.org/Features/AddonHelpers#helper-protocols <https://wiki.squid-cache.org/Features/AddonHelpers#helper-protocols>
>          >   
>           <https://wiki.squid-cache.org/Features/AddonHelpers#helper-protocols <https://wiki.squid-cache.org/Features/AddonHelpers#helper-protocols>>
>          >     "
>          >     For every line sent by Squid exactly one line is expected
>         back. Some
>          >     script language such as perl and python need to be
>         careful about the
>          >     number of newlines in their output.
>          >     "
>          >
>          >     If your helper received something like this (with concurrency
>          >     channel-id
>          >     "1"):
>          >
>          >        "1 bob 192.0.2.1"
>          >
>          >     It should produce a line like:
>          >         "1 OK proxy=all"
>          >
>          >     If no concurrency channel-id is received, then output is
>         the same but
>          >     without sending channel-id back and MUST be sent in same
>         order as
>          >     received.
>          >
>          >     I do recommend using concurrency. It can help further
>         debug issues with
>          >     helpers responding incorrectly.
>          >
>          >     HTH
>          >     Amos
>          >
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