RDMA_OPTION_ID_TOS option

RDMA_OPTION_ID_TOS option

[Steve Wise]

Hey Sean,

Are there any examples out there of IB applications that use 
RDMA_OPTION_ID_TOS?  I'm looking to make this available for iwarp 
transports, but I'm still trying to understand how its currently used, 
and what values are used.  Since this option is level RDMA_OPTION_ID, I 
guess it is transport-neutral?

Thanks,

Steve.
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RE: RDMA_OPTION_ID_TOS option

[Hefty, Sean]

> Are there any examples out there of IB applications that use
> RDMA_OPTION_ID_TOS?  I'm looking to make this available for iwarp
> transports, but I'm still trying to understand how its currently used,
> and what values are used.  Since this option is level RDMA_OPTION_ID, I
> guess it is transport-neutral?

It's transport neutral, but only defined to do anything in the kernel with IB.  For IB, it ends up being used as input into the path record query (as qos_class).  The SA uses the value as input for the resulting path record, most likely to set the SL value.

For iWarp I would expect it to behave similar to RFC 2474, which I haven't look at in a while.  Note the RoCE ends up using the TOS value to set the path record SL using this code:

        route->path_rec->sl = netdev_get_prio_tc_map(
                        ndev->priv_flags & IFF_802_1Q_VLAN ?
                                vlan_dev_real_dev(ndev) : ndev,
                        rt_tos2priority(id_priv->tos));

I don't know if this helps with iWarp, but it may be worth looking at those calls in more detail.

- Sean
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