Re: Containernet (Docker/Container Networking) with DPDK?

[Thomas Monjalon <thomas@monjalon.net>]

20/11/2024 00:23, Thea Corinne Rossman:
> Conceptually, for two containers on the same host, how would exchanging
> traffic work under-the-hood? Specifically, how is the physical NIC
> involved, if at all?

Traffic between containers on the same host does not need to use a PCI device.

You can check virtio-user for this usage:
https://doc.dpdk.org/guides/howto/virtio_user_for_container_networking.html

> For example, on a physical host: for TX, a userspace application writes a
> packet to host memory and pushes its physical address/metadata to the
> appropriate NIC's TX queue. The NIC uses the physical address + DMA to
> avoid a copy when serializing/sending. (Similar for RX in the other
> direction, where the NIC writes to memory.)
> 
> I'm not sure how this would translate to a containerized case on a single
> host, since traffic shouldn't need to exit and the container network has
> its own namespace. Say that two different containers have NICs mapped to
> different PCI addresses (split device). If container A appends to its TX
> queue, what happens next?
> 
> Thanks again for your help.
> 
> On Tue, Nov 19, 2024 at 2:14 PM Thomas Monjalon <thomas@monjalon.net> wrote:
> 
> > 19/11/2024 22:39, Thea Corinne Rossman:
> > > This is SO helpful -- thank you so much.
> > >
> > > One follow-up question regarding NICs: can multiple containers on the
> > same
> > > host share the same PCI device? If I have a host NIC with (say) VFIO
> > driver
> > > binding, do I have to split it with some kind of SR-IOV so that each
> > > container has its own "NIC" binding? Or, when running DPDK's "devbind"
> > > script, can I set up each one with the same PCI address?
> >
> > You need to split devices.
> > SR-IOV VF may help, or you can use SF which was designed exactly for this,
> > with the help of the Linux auxiliary bus.