Re: [Intel-wired-lan] bpf_redirect and xdpgeneric

["Nguyen, Anthony L" <anthony.l.nguyen@intel.com>]

On Mon, 2020-09-28 at 18:20 +0200, Sven Auhagen wrote:
> On Mon, Sep 28, 2020 at 05:24:49PM +0200, Jesper Dangaard Brouer
> wrote:
> > On Fri, 18 Sep 2020 14:27:45 -0600
> > David Ahern <dsahern@gmail.com> wrote:
> > 
> > > On 9/18/20 12:42 PM, Thomas Ptacek wrote:
> > > > The setup is pretty simple. There's an eno1 (igb driver), to
> > > > which our
> > > > default route points. On the same box are several VMs. There's
> > > > a tap
> > > > interface (for each VM, call it tapX). Traffic for a VM flows
> > > > in from
> > > > the Internet on eno1 and is directed to tapX; the response
> > > > traffic
> > > > flows in the other direction.
> > > > 
> > > > I'm deliberately simplifying here:
> > > > 
> > > > eno1 runs an XDP program that does some lightweight IP
> > > > rewriting from
> > > > anycast addresses to internal VM addresses on ingress. eno1's
> > > > XDP
> > > > program currently XDP_PASS's rewritten packets to the IP stack,
> > > > where
> > > > they're routed to the VM's tap. This works fine.
> > > > 
> > > > tapX runs an XDP program that does the same rewriting in
> > > > reverse.
> > > > Right now, it also XDP_PASS's packets to the stack, which also
> > > > works
> > > > --- the stack routes response traffic out eno1.
> > > > 
> > > > I'm playing with XDP_REDIRECT'ing instead of XDP_PASS'ing.
> > > > 
> > > > I have the ifindexes and MAC addresses (and those of IP
> > > > neighbors) in
> > > > a map --- a normal HASH map, not a DEVMAP. Using that map, I
> > > > can
> > > > successfully redirect traffic from tapX to arbitrary other tap
> > > > interfaces. What I can't do is redirect packets from tapX to
> > > > eno1,
> > > > which is what the system actually needs to do.
> > > >   
> > > 
> > > XDP_REDIRECT sends the packet to a devices ndo_xdp_xmit function.
> > > tap
> > > implements it hence eno1 -> tap works; igb does not meaning tap
> > > -> eno1
> > > fails.
> > 
> > There is clearly a real-life use-case for adding native-XDP support
> > for
> > igb driver.  Sven (cc) have implemented this (v6[1]), but something
> > is
> > causing this patch to not move forward, what is stalling Intel
> > maintainers?
> 
> The holdup is from the Intel guys.
> There is a v7 with the changes for Kernel 5.9 but it was only posted
> on
> the Intel list:
> 
> 
https://patchwork.ozlabs.org/project/intel-wired-lan/patch/20200902203222.185141-1-anthony.l.nguyen@intel.com/
> 
> They tested it last week so it should hopefully be merged in the next
> window.

There were some email issues which prevented us from sending it out
sooner (after it was tested). The issue was resolved Friday, I just
sent the patch to netdev:


https://patchwork.ozlabs.org/project/netdev/patch/20200928175908.318502-2-anthony.l.nguyen@intel.com/

Thanks,
Tony

> > 
> > To Thomas, you could try out the patch[2] and report back if it
> > works
> > for you?  (I think it will help moving patch forward...)
> > 
> 
> I would be interested if it works for you as well.
> 
> Best
> Sven
> 
> > [1] 
> > https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fnetdev%2F20200902054509.23jbv5fyj3otziq2%40svensmacbookair.sven.lan%2F&amp;data=02%7C01%7Csven.auhagen%40voleatech.de%7Ccbd762e5a024488f491b08d863c2b6cb%7Cb82a99f679814a7295344d35298f847b%7C0%7C0%7C637369035229290801&amp;sdata=Pv%2BTEQeY4lcPnIprg0n6K0nHOMMlMo2qlrcmxqWNuLY%3D&amp;reserved=0
> > [2] 
> > https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpatchwork.ozlabs.org%2Fproject%2Fnetdev%2Fpatch%2F20200902054509.23jbv5fyj3otziq2%40svensmacbookair.sven.lan%2F&amp;data=02%7C01%7Csven.auhagen%40voleatech.de%7Ccbd762e5a024488f491b08d863c2b6cb%7Cb82a99f679814a7295344d35298f847b%7C0%7C0%7C637369035229290801&amp;sdata=CmlEramL%2FHGz745N6HP%2FWRzPwZs0ERh3kQ8%2Bj%2FIUztw%3D&amp;reserved=0
> > -- 
> > Best regards,
> >   Jesper Dangaard Brouer
> >   MSc.CS, Principal Kernel Engineer at Red Hat
> >   LinkedIn: 
> > https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.linkedin.com%2Fin%2Fbrouer&amp;data=02%7C01%7Csven.auhagen%40voleatech.de%7Ccbd762e5a024488f491b08d863c2b6cb%7Cb82a99f679814a7295344d35298f847b%7C0%7C0%7C637369035229290801&amp;sdata=LJUt38GAkdXS2rW7WG%2BUS0d6eVxZfl3VJqyHvNsqLmY%3D&amp;reserved=0
> > 
> 
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