[exim/exim] [Bug]: host_lookup not applied for client addresses passed via proxy protocol (Issue #3221)

What is the problem environment ?
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Tested in Debian 12, analyzed in upstream code.

What happened?
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When direct smtp client IP is exluded from host_lookup, DNS check is skipped ( https://code.exim.org/exim/exim/src/branch/master/src/src/smtp_in.c#L2598 ) for it but if client IP comes from proxy protocol, it's not ( https://code.exim.org/exim/exim/src/commit/371e5210218746e876fd71c888fdb666c85ceb56/src/src/miscmods/proxy.c#L521 ).

This may generate lot of unnecesarry DNS lookups (i.e. when frontend tests connection to exim backend every few secs passing own IP as client IP via proxy protocol).

Please consider excluding client DNS checks with same host_lookup algo for client IPs passed via proxy protocol.

Relevant log output
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No response

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View it on Exim Forgejo ( https://code.exim.org/exim/exim/issues/3221 ) or reply to this email directly.