Packet-corruption with re(4)

[Jeremy Chadwick]

On Tue, Apr 29, 2008 at 01:18:10PM +0200, Peter Ankerstål wrote:
> Im using a built in re(4) card and it seems like its causes data-corruption 
> as soon as it gets some load (or after a few hours online)
>
> The machine is running FreeBSD 7.0R:
>
> FreeBSD ninja 7.0-RELEASE FreeBSD 7.0-RELEASE #0: Wed Apr 16 22:49:15 CEST 
> 2008     peter at ninja:/usr/obj/usr/src/sys/NINJA  amd64
>
> (using a RELENG_7 kernel updated today)
>
>
> If I download alot of files with wget or something everything works fine 
> for a while until the download just stalls and tcpdump reports "bad cksum"
>
> 13:04:25.839408 IP (tos 0x0, ttl 64, id 23912, offset 0, flags [DF], proto 
> TCP (6), length 1500, bad cksum 0 (->f40a)!) host1.http > host2.53895: . 
> 115065:116513(1448) ack 1421 win 8326 <nop,nop,timestamp 2316944721 
> 2174233192>
> and so on
> again and again until the connection times out.

tcpdump reporting "bad cksum" can occur due to TX/RX checksum
offloading.  Do you not see this message normally, but only when the
problem begins?

Have you tried turning off TX/RX offloading to see if the erroneous
behaviour goes away?

Have you tried disabling RFC1323 to see if that's actually what's
responsible for the stalls you're seeing?  sysctl net.inet.tcp.rfc1323=0

I'd recommend staying away from Realtek NICs.  Pick up an Intel Pro/1000
GT or PT.  Realtek has a well-known history of issues.

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |