Re: bpf_redirect and xdpgeneric

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


Perfect, thank you for the super-clear answer!

Thomas H. Ptacek

On Fri, Sep 18, 2020 at 3:27 PM David Ahern <dsahern@xxxxxxxxx> 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.
> xdpgeneric does not work in the Tx path.

Thomas H. Ptacek

[Index of Archives]     [Linux Networking Development]     [Fedora Linux Users]     [Linux SCTP]     [DCCP]     [Gimp]     [Yosemite Campsites]

  Powered by Linux