We've got a UDP-based network loader that is used for analysis of radio communications systems. In short is sends scheduled bursts of UDP datagrams with tx timestamp in the payload and the UDP servers receive the datagrams and record the rx timestamp. The UDP datagrams range from 100 bytes up to (65535 - 28).
We're using the latest Red Hat 9 kernel 2.4.20-20.9 and we first noticed that the IP header had the Don't Fragment (DF) bit set all the time. Also the More Fragments (MF) bit was set for packets larger than the MTU...which is normal. So we turned on the "ip_no_pmtu_disc" (set to 1) and the DF flag is no longer set for all packets.
Now the problem is that the my UDP server process running on another RHL 9 box does not receive any packets that are over the MTU. I see the IP packets get fragmented but my UDP server doesn't get anything back from the recvfrom().
Any ideas of other flags to turn on/off in /proc?
Thanks, Tuan
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