[netdrivers] Truncated received packets with 4-port D-LinkDFE-580TX and sundance driver

[Michael Gellman]

On Tue, 2005-07-12 at 09:03 +0100, Mark Cave-Ayland wrote:
> Hi Michael,
> 
> I'm still interested in getting these cards working but haven't had much
> time to play. One thing you may like to try if you using an SMP kernel: I
> think I remember seeing a post a while back that mentioned the problem went
> away when using a uniprocessor kernel - if this is the case, would you be
> able to try and report back?
> 

I've got the machines running a vanilla kernel version 2.6.12.2 now.
I've tried both a uniprocessor and SMP-enabled kernel with the same
results as before (that some packets are sometimes truncated).

I'm using a UDP application sending at constant bit-rate in the range of
10Mbps. The counter that registers these errors is InHdrErrors
in /proc/net/snmp which is being incremented by the receive code in
net/ipv4/ip_input.c:

                __u32 len = ntohs(iph->tot_len);
                if (skb->len < len || len < (iph->ihl<<2))
                        goto inhdr_error;

In these error cases, skb->len (i.e. the size of the received packet) is
smaller than the length specified in the IP header, and is then dropped.

I've filed a technical support request with D-Link, and I really hope
that helps. If anyone has any other ideas, I would still greatly
appreciate them!

Thanks,

Michael