every 2nd echo-request malformed when ping -s >4067

[Harald Schmalzbauer]

 schrieb Jeremy Chadwick am 24.10.2012 19:44 (localtime):
> ...
> Okay, so let's decode what you got.  Too bad we don't have snoop-like
> output, since it can decode all of this and output it in a
> human-friendly way.  Gotta do this by hand...
>
>
> 12:21:09.048447 IP 10.5.49.126 > 10.5.49.65: ICMP echo request, id 46597, seq 0, length 4076
>         0x0000:  4500 1000 0f2d 4000 4001 a507 0a05 317e
>
> 0x45       = bits 7-4: IPv4 protocol
>            = bits 3-0: header length: 20 bytes
> 0x00       = DSF / RFC 2474 stuff (don't ask me :-) )
> 0x1000     = datagram length: 4096 bytes
> 0x0f2d     = fragment id
> 0x4000     = bits 15-13: %010 = reserved bit (0), DF bit (1), MF bit (0)
>            = bits 12-0:  fragment offset: 0
> 0x40       = TTL: 64
> 0x01       = protocol: 1 (ICMP)
> 0xe4c7     = header checksum
> 0x0a05317e = source IP
>
> Now for the malformed/wonky packet:
>
> 12:21:10.052891 IP 10.5.49.126 > 10.5.49.65: icmp
>         0x0000:  4500 1000 0f2d 0040 4001 e4c7 0a05 317e
>
> 0x45       = bits 7-4: IPv4 protocol
>            = bits 3-0: header length: 20 bytes
> 0x00       = DSF / RFC 2474 stuff (don't ask me :-) )
> 0x1000     = datagram length: 4096 bytes
> 0x0f2d     = fragment id
> 0x0040     = bits 15-13: %000 = reserved bit (0), DF bit (0), MF bit (0)
>            = bits 12-0:  fragment offset: 64
> 0x40       = TTL: 64
> 0x01       = protocol: 1 (ICMP)
> 0xe4c7     = header checksum
> 0x0a05317e = source IP

Thanks a lot for your effort!
What do you use for decoding?
Please find attached the requested info.
Can you reproduce this oddity via your lo0? Or is 'ping -D -s 4068
127.0.0.1' working on your machine?

Thanks,

-Harry


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