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

[Fab Tillier]

Hi Slava,

Thanks for the insight, I understand what you're trying to do better now.

I think what you are doing should be abstracted somewhat.  Supporting multiple QPs in an IB multicast group should be generic functionality in IBAL.  Once that functionality is there, the support for your specific case of the IGMP multicast groups would be supported.

This also allows using the existing ib_join/leave_mcast APIs without having to expose a new 'attach'.

-Fab

>From: Slava Strebkov [mailto:slavas at voltaire.com]
>Sent: Tuesday, July 01, 2008 1:28 AM
>To: Fab Tillier; ofw at lists.openfabrics.org
>Subject: RE: [owf][patch] user multicast offload support
>
>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
>