[ECOS] bug in ARP FSM with fragmented packets?

Jürgen Lambrecht J.Lambrecht@televic.com
Mon Jan 21 11:18:00 GMT 2008


I'm investigating a problem where UDP packets get lost when there is an 
ARP table timeout.
- It only happens with UDP, not with TCP; IPv4.
- It only happens with fragmented IP packets, so with UDP packets bigger 
than the Ethernet MTU of 1518 Bytes.
- I use freeBSD stack, version from CVS end 2007
This is what I see with Ethereal: The application receives a UDP request 
packet, and must send back a UDP reply packet. Instead an ARP 
request/reply happens, and the packet gets lost.

Using static ARP table entries solves the problem of course, but that is 
not acceptable.

Has anybody seen such a problem before?
Or has anybody a clue where to start looking?

I will do new and more detailed tests next week, and start looking to 
the bsd_tcpip code.

Kind regards,

Jürgen Lambrecht
R&D Engineer
Televic Transport Systems
Televic NV / SA (main office)  	
Leo Bekaertlaan 1
B-8870 Izegem
Tel: +32 (0)51 303045
Fax: +32 (0)51 310670

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