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From: Imran.Patel@nokia.com
To: Imran.Patel@nokia.com
Cc: netfilter-devel@us5.samba.org, netdev@oss.sgi.com,
        linux-kernel@vger.kernel.org
Subject: RE: skb allocation problems (More Brain damage!)
Date: Wed, 11 Apr 2001 21:22:36 +0300
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> Coudl the problem be in the NIC driver not in the alloc_skb?  
No, i don't think so...i got the dump of the packet at the local_out and
post routing hooks....& found it in bad shape there. Here it is what it
looks like:

45 0 0 80 0 0 40 0 ff 1 2d f8 c0 a8 66 16 c0 a8 66 1d 0 0 e4 48 11 d 0 0 14
5d d4 3a 63 1 a 0 8 9 a b c d e f 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d
1e 1f 20 21 22 23 45 0 0 80 0 0 40 0 ff 1 2d f8 c0 a8 66 16 c0 a8 66 1d 0 0
0 0 11 d 0 0 14 5d d4 3a 63 1 a 0 8 9 a b c d e f 10 11 12 13 14 15 16 17 18
19 1a 1b 1c 1d 1e 1f 20 21 22 23


> My gut tells me to blame the NIC driver of the NIC itself.
btw, the card is Intel Ethernet Pro 100..

imran

> On Wed, 11 Apr 2001, Imran.Patel@nokia.com wrote:
> 
> > > Well, I don't know then. You have to debug it. It's probably
> > > something stupid
> > > (if fundamental services like alloc_skb/kfree_skb were
> > > completely buggy
> > > someone surely would have noticed earlier)
> >
> > yep, at first i thought it was because of sume stupidity in 
> my module...but
> > now it seems that actually it is not my code which is doing 
> something
> > stupid....just now i have found out that even simple ping 
> faces similar
> > problems ....here is the output that i get when i ping from the host
> > 192.168.102.29 (runs 2.4.1) to 192.168.102.22 (runs 2.4.3) 
> (Note:I don't
> > insert any kernel modules of my own on these machines):
> >
> >
> > PING 192.168.102.22 (192.168.102.22) from 192.168.102.29 : 
> 100(128) bytes of
> > data.
> > 108 bytes from hobbes.sr.ntc.nokia.com (192.168.102.22): 
> icmp_seq=0 ttl=255
> > time=36.5 ms
> > wrong data byte #36 should be 0x24 but was 0x45
> > 	19 45 d4 3a e 7a a 0 8 9 a b c d e f 10 11 12 13 14 15 
> 16 17 18 19
> > 1a 1b 1c 1d 1e 1f
> > 	20 21 22 23 45 0 0 80 0 0 40 0 ff 1 2d f8 c0 a8 66 16 
> c0 a8 66 1d 0
> > 0 0 0 4 c 0 0
> > 	19 45 d4 3a e 7a a 0 8 9 a b c d e f 10 11 12 13 14 15 
> 16 17 18 19
> > 1a 1b
> >
> > --- 192.168.102.22 ping statistics ---
> > 1 packets transmitted, 1 packets received, 0% packet loss
> > round-trip min/avg/max = 36.5/36.5/36.5 ms
> >
> >
> > Note that the problem starts with byte #36 which goes on 
> like " 45 0 0 80 0
> > ......." which is in fact the outer IP header!! So 
> certainly there are
> > buffer overruns on the other end (host 192.168.102.22)....
> >
> > And as a I said earlier, only ping packets with size within 
> certain range
> > create this problem......Something is terribly wrong here!! 
> But as I am not
> > a Linux mm guru, i can't tell what is wrong here!
> >
> >
> > regards,
> > imran
> >
> > -
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