[ofa-general] IPoIB CM mode and packet drops

[Hal Rosenstock]

I'm seeing the following issue and was hoping for some additional insight:

The local IB interface on a "server" node is in CM (connected) mode
with an MTU of 64K.
dmesg shows numerous errors like:
ib0: packet len 8380 (> 2048) too long to send, dropping

Client machines are attempting to access this node with IPoIB UD. When
the server ib0
interface is switched back to UD (datagram) mode, this problem goes
away but that's
only a workaround.

Has anyone seen this problem ? Any ideas on what causes this and/or
how to resolve it ?

I've seen some comments about this occuring prior to path MTU
discovery. Is the issue is that
some IP services don't utilize path MTU discovery ?

-- Hal