netdev - RE: [PATCH net-next 1/5] vxlan: Make VXLAN default UDP port number available for others

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Date:	Tue, 11 Mar 2014 05:41:37 +0000
From:	Shahed Shaikh <shahed.shaikh@...gic.com>
To:	Or Gerlitz <or.gerlitz@...il.com>
CC:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Dept-HSG Linux NIC Dev <Dept-HSGLinuxNICDev@...gic.com>
Subject: RE: [PATCH net-next 1/5] vxlan: Make VXLAN default UDP port number
 available for others

> -----Original Message-----
> From: Or Gerlitz [mailto:or.gerlitz@...il.com]
> Sent: Tuesday, March 11, 2014 1:28 AM
> To: Shahed Shaikh
> Cc: David Miller; netdev; Dept-HSG Linux NIC Dev
> Subject: Re: [PATCH net-next 1/5] vxlan: Make VXLAN default UDP port
> number available for others
> 
> On Mon, Mar 10, 2014 at 6:48 PM, Shahed Shaikh
> <shahed.shaikh@...gic.com> wrote:
> > From: Shahed Shaikh <shahed.shaikh@...gic.com>
> >
> > Although vxlan module has capability to notify udp ports to other
> > interested net devices using .ndo_add_rx_vxlan_port and
> > .ndo_del_rx_vxlan_port, there could be some devices which support
> > vxlan offload but not interested in updating udp port numbers.
> > This may be because some hardware do not support programming multiple
> > udp ports and their drivers may decide to program only default udp
> > port into adapter. So that adapter, at least, can do offloading for
> > default udp port number.
> 
> Indeed, but the default port number can be unused while another port is
> used. The ndo will be invoked only behalf of an actual instancing of udp port
> for listener socket (== destination port you want the hw to indentify), what's
> wrong with support this ndo also for devices that supported limited (say
> one) such port?


 If driver implements .ndo for udp port and user creates multiple vxlan device with different 
udp ports, it may end up programming the udp port which may not go through the adapter 
and no offload will happen. OTOH, if drive does not implement .ndo and if user is aware that driver
 is capable of offloading for default port, he can at least crate vxlan device on top of qlcnic interface
 with default udp port. So, there is no chance for other udp port numbers to replace default udp port and disturb offloading.

Like Stephen suggested, exporting udp port variable of vxlan driver will be more suitable approach.

Thanks,
Shahed  
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