Re: XDP_REDIRECT with xsks_map and dev_map

[Maciej Fijalkowski <maciej.fijalkowski@intel.com>]

On Wed, Jun 03, 2020 at 01:07:05PM +0200, Toke Høiland-Jørgensen wrote:
> Maciej Fijalkowski <maciej.fijalkowski@intel.com> writes:
> 
> > On Wed, Jun 03, 2020 at 12:49:25PM +0200, Toke Høiland-Jørgensen wrote:
> >> maharishi bhargava <bhargavamaharishi@gmail.com> writes:
> >> 
> >> > On Tue, Jun 2, 2020 at 9:31 PM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
> >> >>
> >> >> maharishi bhargava <bhargavamaharishi@gmail.com> writes:
> >> >>
> >> >> > On Tue 2 Jun, 2020, 14:31 Toke Høiland-Jørgensen, <toke@redhat.com> wrote:
> >> >> >>
> >> >> >> maharishi bhargava <bhargavamaharishi@gmail.com> writes:
> >> >> >>
> >> >> >> > Hi, in my XDP program, I want to redirect some packets using AF_XDP
> >> >> >> > and redirect other packets directly from driver space.
> >> >> >> > Redirection through AF_XDP works fine, but redirection through dev map
> >> >> >> > stops after some packets are processed.
> >> >> >>
> >> >> >> Do you mean it stops even if you are *only* redirecting to a devmap, or
> >> >> >> if you are first redirecting a few packets to AF_XDP, then to devmap?
> >> >> >>
> >> >> >> Also, which driver(s) are the physical NICs you're redirecting to/from
> >> >> >> using, and which kernel version are you on?
> >> >> >>
> >> >> >> -Toke
> >> >> >
> >> >> >
> >> >> >
> >> >> > Currently, I'm trying to redirect packets only using devmap. But also
> >> >> > have code for redirection using AF_XDP(only when a given condition is
> >> >> > satisfied). A DPDK program is running in userspace which will receive
> >> >> > packets from AF_XDP.
> >> >>
> >> >> Right, so it's just devmap redirect that breaks. What do you mean
> >> >> 'redirection stops', exactly? How are you seeing this? Does xdp_monitor
> >> >> (from samples/bpf) report any exceptions?
> >> >>
> >> >> -Toke
> >> >>
> >> > So, In my setup, there are three systems, Let's Assume A, B, C. System
> >> > B is acting as a forwarder between A and C. So I can see the number of
> >> > packets received at system C. To be specific, only 1024 packets are
> >> > received. If I remove the xsks_map part from the code and don't run
> >> > DPDK in userspace. This problem does not occur. Also if I forward all
> >> > the packets using AF_XDP, there is no such issue.
> >> 
> >> I thought you said you were seeing the problem when only redirecting to
> >> a devmap? So why does the xsk_map code impact this? I think you may have
> >> to share some code...
> >
> > Isn't the case here that either xsk_map or dev_map consumes the frame and
> > therefore the latter doesn't see it? so cloning might be needed here?
> 
> Yeah, certainly you can't redirect *the same packet* to both xsk_map and
> devmap - but that wasn't what I understood was the use case here?

Maybe the best would be if Maharishi shared the code as you requested :)

> 
> -Toke
>