On Tue, 11 Jul 2017 11:26:54 -0700 John Fastabend <john.fastab...@gmail.com> wrote:
> On 07/11/2017 07:23 AM, Jesper Dangaard Brouer wrote: > > On Mon, 10 Jul 2017 17:59:17 -0700 > > John Fastabend <john.fastab...@gmail.com> wrote: > > > >> On 07/10/2017 11:30 AM, Jesper Dangaard Brouer wrote: > >>> On Sat, 8 Jul 2017 21:06:17 +0200 > >>> Jesper Dangaard Brouer <bro...@redhat.com> wrote: > >>> > >>>> On Sat, 08 Jul 2017 10:46:18 +0100 (WEST) > >>>> David Miller <da...@davemloft.net> wrote: > >>>> > >>>>> From: John Fastabend <john.fastab...@gmail.com> > >>>>> Date: Fri, 07 Jul 2017 10:48:36 -0700 > >>>>> > >>>>>> On 07/07/2017 10:34 AM, John Fastabend wrote: > >>>>>>> This series adds two new XDP helper routines bpf_redirect() and > >>>>>>> bpf_redirect_map(). The first variant bpf_redirect() is meant > >>>>>>> to be used the same way it is currently being used by the cls_bpf > >>>>>>> classifier. An xdp packet will be redirected immediately when this > >>>>>>> is called. > >>>>>> > >>>>>> Also other than the typo in the title there ;) I'm going to CC > >>>>>> the driver maintainers working on XDP (makes for a long CC list but) > >>>>>> because we would want to try and get support in as many as possible in > >>>>>> the next merge window. > >>>>>> > >>>>>> For this rev I just implemented on ixgbe because I wrote the > >>>>>> original XDP support there. I'll volunteer to do virtio as well. > >>>>>> > >>>>> > >>>>> I went over this series a few times and it looks great to me. > >>>>> You didn't even give me some coding style issues to pick on :-) > >>>> > >>>> We (Daniel, Andy and I) have been reviewing and improving on this > >>>> patchset the last couple of weeks ;-). We had some stability issues, > >>>> which is why it wasn't published earlier. My plan is to test this > >>>> latest patchset again, Monday and Tuesday. I'll try to assess stability > >>>> and provide some performance numbers. > >>> > >>> > >>> Damn, I though it was stable, I have been running a lot of performance > >>> tests, and then this just happened :-( > >> > >> Thanks, I'll take a look through the code and see if I can come up with > >> why this might happen. I haven't hit it on my tests yet though. > > > > I've figured out why this happens, and I have a fix, see patch below > > with some comments with questions. > > > > Awesome! > > > The problem is that we can leak map_to_flush in an error path, the fix: > > > > diff --git a/net/core/filter.c b/net/core/filter.c > > index 2ccd6ff09493..7f1f48668dcf 100644 > > --- a/net/core/filter.c > > +++ b/net/core/filter.c > > @@ -2497,11 +2497,14 @@ int xdp_do_redirect_map(struct net_device *dev, > > struct xdp_buff *xdp, > > ri->map = NULL; > > > > trace_xdp_redirect(dev, fwd, xdp_prog, XDP_REDIRECT); > > - > > + // Q: Should we also trace "goto out" (failed lookup)? > > + // like bpf_warn_invalid_xdp_redirect(); > > Maybe another trace event? trace_xdp_redirect_failed() > > > return __bpf_tx_xdp(fwd, map, xdp, index); > > out: > > ri->ifindex = 0; > > - ri->map = NULL; > > + // XXX: here we could leak ri->map_to_flush, which could be > > + // picked up later by xdp_do_flush_map() > > + xdp_do_flush_map(); /* Clears ri->map_to_flush + ri->map */ > > +1 > > ah map lookup failed and we need to do the flush nice catch. I'm still getting crashes (but much harder to provoke), but I figured out why. We sort of missed one case, where map_to_flush gets set, when the ndo_xdp_xmit() call starts to fail, and the ixgbe driver then forgets to call xdp_do_flush_map, if all packets in that NAPI cycle failed. We could blame the driver, but yhe clean solution is making sure, that we don't set map_to_flush when the __bpf_tx_xdp() call fails. It should also handle the other case I fixed .... I'll cleanup my PoC-fix patch, test it and provide it here. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
