TCPv4 and UDP bad cheksums

Jakob Borg (jborg@df.lth.se)
Fri, 17 Dec 1999 21:52:02 +0100

I get a lot of these (frequency obvious from logs below). This is
mildly irritating, but does not seem to have any other bad effects
that I have notices. All of the addresses mentioned are on my subnet,
and at least the source machines for the UDP packets are windows
machines.

This is under 2.3.33 ("Linux version 2.3.33 (jb@narayan.replicant.nu)
(gcc version 2.95.2 19991109 (Debian GNU/Linux)) #3 SMP Wed Dec 15
15:52:17 CET 1999" but I have seen the same thing in earlier 2.3.2?
kernels, just haven't run the in-between kernels). It happens more or
less all the time, not depending on machine load or so.

The machine is a 2-way PII at 400MHz running an SMP kernel, with some
kind of ISA NE2000-clone network card.

Dec 17 21:41:34 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0003 to 194.47.218.58:0420, len=20/40
Dec 17 21:41:42 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0420 to 194.47.218.58:008b, len=20/40
Dec 17 21:42:13 narayan last message repeated 12 times
Dec 17 21:42:18 narayan last message repeated 3 times
Dec 17 21:42:22 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0001 to 194.47.218.58:0420, len=20/40
Dec 17 21:42:22 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0420 to 194.47.218.58:008b, len=20/40
Dec 17 21:42:38 narayan last message repeated 4 times
Dec 17 21:42:39 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0052 to 194.47.218.58:0420, len=20/40
Dec 17 21:42:39 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0420 to 194.47.218.58:008b, len=20/40
Dec 17 21:42:47 narayan kernel: UDP: bad checksum. From 194.47.219.107:137 to 194.47.219.255:137 ulen 76
Dec 17 21:43:28 narayan kernel: UDP: bad checksum. From 194.47.219.224:138 to 194.47.219.255:138 ulen 219
Dec 17 21:43:28 narayan kernel: UDP: bad checksum. From 194.47.216.121:138 to 194.47.219.255:138 ulen 228
Dec 17 21:44:15 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0420 to 194.47.218.58:008b, len=20/40
Dec 17 21:44:22 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0420 to 194.47.218.58:008b, len=20/40
Dec 17 21:44:28 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0013 to 194.47.218.58:0420, len=20/40
Dec 17 21:44:57 narayan kernel: UDP: bad checksum. From 194.47.216.129:138 to 194.47.219.255:138 ulen 216
Dec 17 21:44:59 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0420 to 194.47.218.58:008b, len=20/40
Dec 17 21:45:13 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0049 to 194.47.218.58:0420, len=20/40
Dec 17 21:45:14 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0420 to 194.47.218.58:008b, len=20/40
Dec 17 21:45:24 narayan kernel: UDP: bad checksum. From 194.47.216.126:138 to 194.47.219.255:138 ulen 209
Dec 17 21:45:27 narayan kernel: TCPv4 bad checksum from 194.47.218.23:001e to 194.47.218.58:0420, len=20/40
Dec 17 21:45:28 narayan kernel: TCPv4 bad checksum from 194.47.218.23:0420 to 194.47.218.58:008b, len=20/40

Is there something I can do to get rid of these messages? Do they
indicate some kind of network problem, or are they just harmless debug
output?

thanks,

-- 
Jakob Borg <jborg@df.lth.se>  http://jb.replicant.nu
----
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