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

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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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