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SubjectRe: Kernel messages
Date
chris@ferret.lmh.ox.ac.uk said:
} I got these (see below). What are they all about? I don't have any
} masquerading rules defined! Although I believe I do have masquerade
} support compiled in.

} MASQ: failed TCP/UDP checksum from x.x.x.x!
} MASQ: failed TCP/UDP checksum from x.x.x.x!

Oh, what an interesting side effect....

If you have masq compiled in, all incoming packets destined for a local
address will pass through the masq checks. Since masq involves rewriting
packets and regenerating the checksums, quite early on it checks UDP/TCP
packets for correct checksums on the basis that rewriting a broken packet
is a waste of time. Nothing else reports broken checksums at all, but the
masq code does (at too high a level of message in retrospect).

} Is someone trying it on??

No, just some broken kit or wiring out there...

I guess that it may be time to look at that code and see if we can speed
it up by moving the checksum check after the relevance check. You may
only get this if the packets are destined for a port about 60000 - need to
check code for that.

Nigel.


--
[ Nigel.Metheringham@theplanet.net - Systems Software Engineer ]
[ Tel : +44 113 251 6012 Fax : +44 113 224 0003 ]
[ Friends don't let friends use sendmail! ]



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