Re: [PATCH RFC] iw_cxgb3: Support "iwarp-only" interfaces to avoid 4-tuple conflicts with the host stack.

[Steve Wise <swise@opengridcomputing.com>]

Steve Wise wrote:
> Roland Dreier wrote:
> >  > > What's wrong with my suggestion of having the iwarp driver create an
> >  > > "iwX" interface to go with the normal "ethX" interface?  It seems
> >  > > simpler to me, and there's a somewhat similar precedent with how
> >  > > mac80211 devices create both wlan0 and wmaster0 interfaces.
> >  > >  - R.
> >  >  > It seemed much more painful for me to implement. :-)
> >  >  > I'll look into this, but I think for this to be done, the 
> > changes must
> >  > be in the cxgb3 driver, not the rdma driver, because the guts of the
> >  > netdev struct are all private to cxgb3.  Remember that this interface
> >  > needs to still do non TCP traffic (like ARP and UDP)...
> >  >  > Maybe you have something in mind here that I'm not thinking about?
> >
> > No, I was just spouting off.
>
> At least someone is looking at my patch. ;-)
>
> > But the whole "create a magic alias" seems kind of unfriendly to the
> > user.  Maybe as you said, the cxgb3 net driver could create the alias
> > for the iw_cxgb3 driver?
>
> I agree that it is not very user friendly.
>
> My current patch just utilizes the IP address alias logic in the IP 
> stack.  So when you do 'ifconfig ethxx:blah ipaddr up' it creates a 
> struct in_ifaddr which contains a ptr to the real struct net_device that 
> services this alias.  However, from what I can tell, I cannot just 
> create one of these without binding an address.  So the driver cannot 
> create the alias interface until it knows the ipaddr/netmask/etc.  IE: 
> if you say 'ifconfig ethxx:blah up' it fails...  You must supply an 
> address to get one of these created.
>
> To have the cxgb3 driver create something like 'iw0', I think it would 
> need to create a full net_device struct.  This makes the change much 
> more complex.  But perhaps its the right thing to do...
>
> Steve.

Also, I could defer registering the device with the rdma core until the 
alias interface is created by the user.  Thus the T3 device wouldn't be 
available for use until the ethxx:iw interface is created.

And I could log a WARN or INFO message if the iw_cxgb3 module is loaded 
and no ethxx:iw alias exists.  This would help clue in the user...

Steve.


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