Changing Between Infiniband Connected Mode and Datagram Mode at Runtime on FreeBSD 12.2

Foster, Greg gfoster at
Thu Mar 4 02:49:55 UTC 2021

Hello FreeBSD IB,

What is the procedure to change between Infiniband Connected Mode and Datagram Mode
at runtime on FreeBSD 12.2?

I've seen different references on the WEB, but the procedure still seems unclear.

In one reference
refers to the Linux procedure, which is not applicable on FreeBSD.

Another reference,, implies the driver must be recompiled
to change modes.

Yet another,
Suggests it can be done at runtime to add a tuneable/sysctl but doesn't specify any details...

Is the solution to maybe compile the drivers twice, once for CM and once for DM, keeping both around
and loading the desired one?

Greg Foster

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