How can i detect if a received UDP got fragmented from userland?

[Sten Daniel Sørsdal]

I am currently working on a udp multicast application written in C for
FreeBSD (6.x)

For our test cases in many different network types we found that
fragmentation poses as a significant problem for quality and reliability.
Packets that get fragmented are more likely to get dropped than
packets that do not get fragmented and since our application needs high 
bulk performance without retransmissions we believe our application and 
the network would benefit from this.
Our first assumption was that adding DF to UDP would solve it, and it
does in our small tests, but it has a noticable negative effect on the 
network.
Are there any way i can read whether a message's packet was fragmented 
into smaller pieces and preferably how large the largest fragment was?
Are there any feasible way to do this?

Thank you for your time.
-- 
Sten Daniel Sørsdal



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