2008/242 Data Fast-Path for Softmac

[Darren Reed]

Sebastien Roy wrote:
...

>        Note that some GLDv3 features requires the GLDv3 DLS/MAC layer
>        processing to not be bypassed to assure its function correctness.
>        For example, softmac fast-path must be disabled to support GLDv3
>        VNIC functionality. As the result, we propose: By default, the
>        softmac fast-path mode will be used to assure the performance; MAC
>        clients will be able to request to disable the softmac fast-path
>        mode to support certain features, and if that succeeds, the system
>        will fallback to the existing softmac data-path model (called 
> slow-path).


Does VNIC here only refer to the vni* interfaces or does
it also to the VLAN network interfaces, such as ce132000?

Can the architecture of this project be changed or expanded
to include dealing with the VNIC functionality problem?


>        2. For IP/ARP streams over a softMAC, softmac data fast-path 
> will be
>           used by default, unless fast-path is disabled by any MAC client
>           explicitly. The softmac module first identifies an IP/ARP 
> stream
>           by seeing whether there is a SIOCSLIFNAME ioctl sent from 
> upstream,
>           if there is one, this stream is either an IP or an ARP stream
>           and will use fast-path potentially;


Why are you looking at the SIOCSLIFNAME ioctl rather than
the bind?  As defined, SIOCSLIFNAME does not appear to be
IP specific at all, aside from our implementation and use.


>        4. When the softmac data fast-path is disabled by a MAC client 
> (e.g.,
>           by a VNIC), all the IP/ARP upper streams will try to switch 
> from
>           the fast-path to the slow-path. 

...
 >       5. On the other hand, when the last MAC client cancels its 
fast-path
 >          disable request, all the IP/ARP streams will try to switch 
back to
 >          the fast-path mode;


In both cases 4 & 5, what happens if they fail to switch over?


Darren