> >
> > 08:39:55.649689 IP 10.2.10.254.22 > 12.33.234.69.35026: .
> > 5906:10250(4344) ack 1
> > 794 win 674 <nop,nop,timestamp 413790 3873837887>
> > 08:39:55.650532 IP 10.2.10.1 > 10.2.10.254: icmp 92: 12.33.234.69
> > unreachable - need to frag (mtu 1500)
>
> Where was this dump taken, on 10.2.10.254?
>
Yes. It appears that if tcpdump is run on the sending system it sees the
packets before segmentation offload does its thing.
> If so could youd either take the dump further down the route
> or show the full contents (with tcpdump -x) of the ICMP error
> here so that we can see what the actual packet size was?
>
Here's an example IP packet followed by the resulting ICMP as seen with
tcpdump on 10.2.10.254. ICMP is complaining about a 2896 byte packet,
which leads me to believe that the TSO is using the wrong mss or simply
isn't doing anything at all.
11:36:12.006330 IP (tos 0x8, ttl 64, id 20681, offset 0, flags [DF],
length: 29
48) 10.2.10.254.22 > 12.33.234.69.47703: . 91224:94120(2896) ack 49 win
674 <nop
,nop,timestamp 24659048 3970819017>
0x0000: 4508 0b84 50c9 4000 4006 d33c 0a02 0afe
[EMAIL PROTECTED]@..<....
0x0010: 0c21 ea45 0016 ba57 09f8 1838 7577 90cb
.!.E...W...8uw..
0x0020: 8010 02a2 16dd 0000 0101 080a 0178 4468
.............xDh
0x0030: ecad e3c9 96f8 ad0d e909 4e89 202a 9d85
..........N..*..
0x0040: 4b58 a65f 53d9 07f4 0435 2557 970b 943d
KX._S....5%W...=
0x0050: 1eba ..
11:36:12.007019 IP (tos 0x0, ttl 64, id 43865, offset 0, flags [DF],
length: 11
2) 10.2.10.1 > 10.2.10.254: icmp 92: 12.33.234.69 unreachable - need to
frag (mt
u 1500) for IP (tos 0x8, ttl 64, id 20681, offset 0, flags [DF],
length: 2948)
10.2.10.254.22 > 12.33.234.69.47703: . 91224:94120(2896) ack 49 win 674
<nop,nop
,timestamp 24659048 3970819017>
0x0000: 4500 0070 ab59 4000 4001 6631 0a02 0a01
[EMAIL PROTECTED]@.f1....
0x0010: 0a02 0afe 0304 7cc8 0000 05dc 4508 0b84
......|.....E...
0x0020: 50c9 4000 4006 d33c 0a02 0afe 0c21 ea45
[EMAIL PROTECTED]@..<.....!.E
0x0030: 0016 ba57 09f8 1838 7577 90cb 8010 02a2
...W...8uw......
0x0040: 706d 0000 0101 080a 0178 4468 ecad e3c9
pm.......xDh....
0x0050: 96f8
-Brian
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