On Mon, 28 Apr 2025 11:31:10 +0530
Prashant Upadhyaya <praupadhyaya@gmail.com> wrote:

> On Sat, 26 Apr 2025 at 20:58, Stephen Hemminger <stephen@networkplumber.org>
> wrote:
>
> > On Fri, 25 Apr 2025 23:17:30 +0530
> > Prashant Upadhyaya <praupadhyaya@gmail.com> wrote:
> > 
> > > Hi,
> > >
> > > I am having a VM on Azure where I have got two 'accelerated networking'
> > > interfaces of Mellanox
> > > # lspci -nn|grep -i ether
> > > 6561:00:02.0 Ethernet controller [0200]: Mellanox Technologies MT27710
> > > Family [ConnectX-4 Lx Virtual Function] [15b3:1016] (rev 80)
> > > f08c:00:02.0 Ethernet controller [0200]: Mellanox Technologies MT27710
> > > Family [ConnectX-4 Lx Virtual Function] [15b3:1016] (rev 80)
> > >
> > > I have a DPDK application which needs to obtain 'all' packets from the 
> > NIC. 
> > > I installed the drivers, compiled DPDK24.11 (Ubuntu20.04), my app starts
> > > and is able to detect the NIC's.
> > > Everything looks good
> > > myapp.out -c 0x07 -a f08c:00:02.0 -a 6561:00:02.0
> > > EAL: Detected CPU lcores: 8
> > > EAL: Detected NUMA nodes: 1
> > > EAL: Detected shared linkage of DPDK
> > > EAL: Multi-process socket /var/run/dpdk/rte/mp_socket
> > > EAL: Selected IOVA mode 'PA'
> > > EAL: VFIO support initialized
> > > mlx5_net: Default miss action is not supported.
> > > mlx5_net: Default miss action is not supported.
> > > All Ports initialized
> > > Port 0 is UP (50000 Mbps)
> > > Port 1 is UP (50000 Mbps)
> > >
> > > The trouble is that the ARP packets are not being picked up by my DPDK
> > > application, I see them being delivered to the kernel via the eth 
> > interface 
> > > corresponding to the port (MLX is a bifurcated driver, you don't really
> > > bind to the NIC, so you still see the eth interfaces at linux level and 
> > can 
> > > run tcpdump on those, I see ARP packets in the tcpdump there on the
> > > interface)
> > > I can receive UDP packets in my DPDK app though.
> > >
> > > My application is not setting any rte_flow rules etc. so I was expecting
> > > that by default my dpdk app would get all the packets as is normally the
> > > case with other NIC's
> > > Is there something I need to configure for Mellanox NIC somewhere such 
> > that 
> > > I get 'all' the packets including ARP packets in my DPDK app ?
> > >
> > > Regards
> > > -Prashant 
> >
> > The Mellanox device in Azure networking cards is only used as a VF switch.
> > You can go back to earlier DPDK presentations for more detail.
> >
> > Three reason bifurcation won't work.
> >  1. Only some of the packets arrive on the VF. All non-IP show up on
> >     the synthetic device. The VF is only used after the TCP three way
> >     handshake.
> >  2. The Netvsc PMD doesn't handle flow rules.
> >  3. The VF can be removed and restored any time (by hypervisor)
> >     it is not a stable entity.
> >
> > 
>  Thanks Stephen, so are we concluding that DPDK apps are unusable in Azure
> as per my requirements, is there no work around or any other possibility to
> use DPDK in Azure VM ? Please do send me a link to the correct presentation
> I should refer to.
>
> Regards
> -Prashant

Remember in the cloud network interfaces are free, there really is no need
for bifurication just create two interfaces to VM, one for DPDK, and one for
non DPDK.