On Wed, 2017-04-12 at 11:22 -0400, David Miller wrote:
> From: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
> Date: Wed, 12 Apr 2017 16:29:07 +0200
>
> > On Wed, 2017-04-12 at 13:07 +0200, Johannes Berg wrote:
> >>
> >> struct ieee80211_if_mntr {
> >> u32 flags;
> >>
> > [...]
> > + bool deliver;
> >
> > That's ... broken for multi-queue RX. I haven't really found a good
> > other way to do it. The best way will likely be to copy the SKB the
> > first time it's needed, build the radiotap header, and then keep a
> > reference to it to be able to clone it later if it's needed again.
>
> If you don't recurse into the receive path for different devices
> before you are done with this boolean, simply make a global per-cpu
> boolean and use that.
No, that won't work. We don't recurse, but this is a per-interface
bool, as we can have multiple monitor interfaces (possibly with
different filters).
The problem comes from the fact that I did
for_each_interface()
iface.deliver = run_bpf_program();
if (nobody_wanted_it)
return;
skb = build_monitor_skb()
for_each_interface()
if (iface.monitor)
deliver(skb);
What I should be doing is something like this:
for_each_interface() {
if (run_bpf_program()) {
if (!skb)
skb = build_monitor_skb();
deliver(skb);
}
}
where deliver() does skb_clone() internally or so.
johannes
