[courier-users] Found small bug in rfc1035/rfc1035mxlist.c

[Matthias W. <m...@tt...>]

Hi!

I found a small bug in the file rfc1035/rfc1035mxlist.c.

The bug is in the addrecord() function:

        while ( *list && (*list)->priority < mxpreference )
                list= &(*list)->next;

should get changed to:

        while ( *list && (*list)->priority <= mxpreference )
                list= &(*list)->next;

The reason for this is that the original code reverses the order of the
address records for an MX preference level. When add_arecords first
calls harvest_records for AAAA records and after that calls
harvest_records for A records, this results in IPv4 addresses tried
before IPv6 addresses which is incorrect according to RFC 3974 section 3.

And alternative solution to fix the problem would be to change the order
of the harvest_records() calls for AAAA and A records within the
add_arecords() function, but in that case also the code for processing
the HARVEST_NODUPE flag would have to be modified, as this flag would
have to be used with the AAAA record call in that case.

Without the patch "testmxlookup tthias.eu" shows the addresses in the
incorrect order:

# testmxlookup tthias.eu
Domain tthias.eu:
Relay: mailin.amessage.eu, Priority: 10, Address: ::ffff:212.112.238.55
[ LOCAL ]
Relay: mailin.amessage.eu, Priority: 10, Address: 2001:6f8:900:10d::2 [
LOCAL ]

After fixing the bug textmxlookup returns the addresses in the correct
order:

# testmxlookup tthias.eu
Domain tthias.eu:
Relay: mailin.amessage.eu, Priority: 10, Address: 2001:6f8:900:10d::2 [
LOCAL ]
Relay: mailin.amessage.eu, Priority: 10, Address: ::ffff:212.112.238.55
[ LOCAL ]


Matthias

-- 
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81476 München       http://ma.tthias.eu/