[exim-dev] [Bug 1289] 10.14: Is there a wrong example?

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Author: Phil Pennock
Date:  
To: exim-dev
Subject: [exim-dev] [Bug 1289] 10.14: Is there a wrong example?
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http://bugs.exim.org/show_bug.cgi?id=1289




--- Comment #3 from Phil Pennock <pdp@???> 2012-08-27 03:55:26 ---
The "+ignore_unknown" example looks correct to me, but could be better phrased.

Note: +include_unknown and +ignore_unknown both exist and are different.

Note further:

1) if the hostlist only contains IP addresses, there's no need for any DNS,
everything's easy
2) if the hostlist contains a name, then the matching is *NOT* to resolve that
name to some IPs to be checked; instead, the behaviour is to look up reverse
DNS for the IP address and match that hostname against the list item. This is
used for items such as wildcarded match patterns.

So let's say that a connection is received from the IPv4 address [192.168.4.5]
and there is no reverse DNS for that IP address.

Given an ACL item of:

accept hosts = friend.example : 192.168.4.5

then the rule will *NOT* match; Exim is unable to obtain a hostname so is
unable to compare to "friend.example" and so errors out at that point, instead
of continuing onto the next item.

Given an ACL item of:

accept hosts = +ignore_unknown : friend.example : 192.168.4.5

then Exim modifies its behaviour because of the first item; the second item
requires DNS and is now ignored because we have no DNS; so matching proceeds to
the third item and succeeds, so the rule as a whole *DOES* now match.


Your proposed rephrasing may be clearer and might still be a good idea to
apply. I am jetlagged and unwilling to make a judgement call on that, so will
leave it to Todd on Monday.


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