[ofa-general] Receiving 24-byte remnant header on bad umad_recv?

[Roland Dreier]

 > I am building a program that sometimes sends MADs from device A to device
 > B, and device B should (by design) silently ignore these packets.
 > 
 > Device A is using OFED 1.3.1's libibumad-1.1.7, and I am sending these MADs
 > using a regular umad_send() method. When B responds, the subsequent
 > umad_recv() works just fine.  However, when B is supposed to silently
 > ignores the MAD, device A's subsequent umad_recv() receives a strange
 > packet rather than timing out.  It receives a 24-byte packet that looks
 > like a MAD Header. All of its fields except for TID are the same as the
 > original send's MAD Header.

This is expected... the small packet is showing that device A's request
is timing out (and you should see the status field in the packet showing
a timeout error -- I forget the exact details but you can look at the
user_mad.c source in the kernel to see what happens in this case).