Re: [exim] Now exim segfault in a very strange way :-/ (was:…

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Autor: Philip Hazel
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A: Marc Schiffbauer
CC: exim-users
Assumpte: Re: [exim] Now exim segfault in a very strange way :-/ (was: Re: Why does exim4 stat /boot and /proc/<pid>/mounts very often?)
On Sat, 18 Dec 2004, Marc Schiffbauer wrote:

> 02:22:53 10252 host in host_lookup? yes (matched "*")
> 02:22:53 10252 looking up host name for 62.134.104.46
> 02:22:53 10252 DNS lookup of 46.104.134.62.in-addr.arpa (PTR) succeeded
> 02:22:53 10252 ---1 Get 0x8107540     8         host.c 1310
> 02:22:53 10252 ---1 Get 0x8107548   264         host.c 1320
> 02:22:53 10252 ---1 Rst 0x8107569    **         host.c 1333 32800
> 02:22:53 10252 IP address lookup yielded c-134-x3-x4.k.dial.de.ignite.net
> 02:22:53 10252 gethostbyname2(af=inet6) returned 4 (NO_DATA)
>                                  ^^^^^??
> 02:22:53 30968 child 10252 ended: status=0xb
>                                          ^^^?


Your Exim has been compiled with IPv6 support. That is why an attempt to
look up an IP address starts by looking for an IPv6 address. Then it
will try an IPv4 address (having not found an IPv6 one).

I think I see where the problem might be. Try running the command

host c-134-x3-x4.k.dial.de.ignite.net

When I do that, it returns

;; Truncated, retrying in TCP mode.
c-134-x3-x4.k.dial.de.ignite.net has address 62.134.104.0

followed by another 2047 IP addresses. In other words, that host name
has 2048 IP addresses associated with it. Sheesh. What lunatics are
running that zone?

The obvious Exim workaround is to set

host_lookup = !62.134.104.0/21

Or even just set host_lookup empty so it never does reverse lookups.

The crash might be in Exim, or it might be in the resolver library. I
will do some experiments with Exim when I get some time, and if it is a
problem in Exim itself, I'll fix it.

-- 
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book:    http://www.uit.co.uk/exim-book