Re: slow tcp with isdn
Tue, 29 Jul 1997 13:29:52 +0200

Gerd Knorr <> writes:
>Syslog says nothing. ifconfig ippp0 says 0 rx/tx errors, so does
>/proc/net/snmp for ip. But ip checksum is the ip header only, right?


>I grep'ed net/ipv4/tcp*.c for a bad-checksum-printk(), but hav'nt found
>one. Does the 2.0.30 kernel log and/or count bad tcp packets? If not,
>is there any way to do this?

You'd have to add a printk or a log count to the code that checks the
TCP checksum. Look at the routine tcp_rcv in net/ipv4/tcp_input.c
to see where you need to add this. You should do the printk/count
just before the jump to discard_it in the checksum testing code
at the start of this routine.

>/proc/net/snmp has no somethingError entry for tcp. But there is a
>RetransSegs entry. This one lists 5. Hmm...
>Is this incoming? outgoing? both?

Outgoing. There is no way of knowing the actual incoming count, although
I suppose we could count the number of "duplicate" packets we received.

Eric Schenk                               www:
Dept. of Comp. Sci., Lund University          email:
Box 118, S-221 00 LUND, Sweden   fax: +46-46 13 10 21  ph: +46-46 222 96 38