Public bug reported:
On Ubuntu 20.04 with glibc-2.31, sendmail fails to verify IPv6 client
addresses (reverse-then-forward-lookup) and refuses to accept incoming
mail:
May 20 16:42:50 mx sm-mta[161617]: ruleset=check_relay,
arg1=[IPv6:2a04:6c0:0:0:0:0:bad:0], arg2=IPv6:2a04:6c0:0:0:0:0:bad:0,
relay=hektik.14v.de [IPv6:2a04:6c0:0:0:0:0:bad:0] (may be forged),
reject=451 4.1.8 Possibly forged hostname for
IPv6:2a04:6c0:0:0:0:0:bad:0
No such problem on Ubuntu 18.04 (glibc-2.27).
It seems the patch "glibc-2.30.patch" fixes the FTBS problem, but does
not provide an alternate method for IPv6 reverse lookups.
I checked with tcpdump and the forward lookups are always for "A"
records instead of "AAAA".
There is already some #ifdef in conf.c, function sm_getipnodebyname()
for gethostbyname2().
If I add
#define HAS_GETHOSTBYNAME2 1
before that, reverse lookups for IPv6 do work again as expected.
** Affects: sendmail (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1879738
Title:
IPv6 reverse lookup broken (possibly by glibc-2.30.patch)
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