Merge branch 'for_net-next-5.1/rds-tos-v4' of git://git.kernel.org/pub/scm/linux...

Santosh Shilimkar says:

====================
rds: add tos support

RDS applications make use of tos to classify database traffic.
This feature has been used in shipping products from 2.6.32 based
kernels. Its tied with RDS v4.1 protocol version and the compatibility
gets negotiated as part of connections setup.

Patchset keeps full backward compatibility using existing connection
negotiation scheme. Currently the feature is exploited by RDMA
transport and for TCP transport the user tos values are mapped to
same default class (0).

For RDMA transports, RDMA CM service type API is used to
set up different SL(service lanes) and the IB fabric is configured
for tos mapping using Subnet Manager(SL to VL mappings).
Similarly for ROCE fabric, user priority is mapped with different
DSCP code points which are associated with different switch queues
in the fabric.

The original code was developed by Bang Nguyen in downstream kernel back in
2.6.32 kernel days and it has evolved significantly over period of time.

Thanks to Yanjun for doing testing with various combinations of host like
v3.1<->v4.1, v4.1.<->v3.1, v4.1 upstream to shipping v4.1 etc etc
====================

Signed-off-by: David S. Miller <davem@davemloft.net>