vge traffic problem

[David Ehrmann]

Pyun YongHyeon wrote:
> If receiver drops TX UDP frame sent by vge(4) would you try
> disabling TX checksum offloading of vge(4)? If packet drop happens
> only with UDP frames it could be checksum offload bug. Does your
> controller is VT6130(PCIe)?
>   

First, netstat before and after the test:

share2# netstat -I vge0 -d
Name    Mtu Network       Address              Ipkts Ierrs Idrop    
Opkts Oerrs  Coll Drop
vge0   1500 <Link#1>      00:40:63:xx:xx:xx 38940717     0     0 
55913584     0     0    0
vge0   1500 10.0.0.0/22   share2            38886994     -     - 
55898223     -     -    -
share2# netstat -I vge0 -d
Name    Mtu Network       Address              Ipkts Ierrs Idrop    
Opkts Oerrs  Coll Drop
vge0   1500 <Link#1>      00:40:63:xx:xx:xx 38942065     0     0 
55914869     0     0    0
vge0   1500 10.0.0.0/22   share2            38888320     -     - 
55899491     -     -    -

The error counters were uninteresting.  Here's what the internal 
counters said, but they weren't very interesting, either:

http://pastebin.com/m20114095

I ran the test, again, and had tcpdump capture the packets (on the host 
with the vge interface).

tcpdump -i vge0 -w dump.cap -K -s 0 host 10.0.1.2

When I opened it up in Wireshark, it's reporting that the outgoing UDP 
checksums are incorrect; they're always 0x1ae3.  That said, maybe the 
checksums are done in hardware AFTER tcpdump sees them.

I set net.inet.udp.checksum to 0.  The bad checksums are gone, but I 
still see dropped packets.

It's on the motherboard, probably wired directly to a PCI-E connection, 
but yes, it is a VT6130.