[ofw] RE: [owf][patch] user multicast offload support

[Slava Strebkov]

Hi Fab,

Please read the answers below

 

-----Original Message-----
From: Fab Tillier [mailto:ftillier at windows.microsoft.com] 
Sent: Monday, June 30, 2008 7:48 PM
To: Slava Strebkov; ofw at lists.openfabrics.org
Subject: RE: [owf][patch] user multicast offload support

 

Hi Slava,

 

>Please review the code that adds support for user mode component

>performing multicast offload for applications.

>The idea is to allow host to issue IGMP messages through IPoIB. No data

>flow on IPoIB since there is no ATTACH in case of using user mcast

>offload. This prevents data duplicating on receive path.

>IB leave will send always if issued from user mode application, and
when

>reference count reaches 0 if leave has been requested from IPoIB.

 

Is there anything in the WinOF SVN that will use this capability?

There is nothing in SVN and probably will not be.

Are you going to solve the issue where the first client to leave a MC
group will tell the SA to remove the port from the MC group so that
other clients using the MC group will not get 'disconnected'?  I would
think this would be an important first step.

      SA will remove the port from MC group when the last user of this
group leaves it. Reference count is used for that purpose in
al_igmp_list_remove_record

Maybe it's just that I don't understand how the applications work.  Do
they create their own UD QPs, and attach them to the MC group?  Who
issues the MC join/leave to the SA?  Who issues the attach/detach of the
user-mode UD QPs to the HCA, and how?

 New LSP for multicast offloading will create QPs from user mode and
issue attach/detach upon application request (e.g. from
SetSockOptions()). Together with IB socket provider, original (TCP /
IPoIB) service provider will be called in order to use IGMP
functionality in windows protocol stack. This is essential for issuing
IGMP messages to Ethernet routers that may be in a data way connected to
IB host through IPR.

 

Once I understand the above better I'll be able to provide meaningful
comments on the patch.

 

Thanks,

-Fab

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