On Sun, Jun 19, 2016 at 08:19:20PM -0600, David Ahern wrote:
> > diff --git a/net/mpls/mpls_iptunnel.c b/net/mpls/mpls_iptunnel.c
> > index fb31aa8..802956b 100644
> > --- a/net/mpls/mpls_iptunnel.c
> > +++ b/net/mpls/mpls_iptunnel.c
> > @@ -105,12 +105,15 @@ static int mpls_output(struct net *net, struct sock
> > *sk, struct sk_buff *skb)
> > bos = false;
> > }
> >
> > + rcu_read_lock_bh();
> > if (rt)
> > err = neigh_xmit(NEIGH_ARP_TABLE, out_dev, &rt->rt_gateway,
> > skb);
> > else if (rt6)
> > err = neigh_xmit(NEIGH_ND_TABLE, out_dev, &rt6->rt6i_gateway,
> > skb);
> > + rcu_read_unlock_bh();
> > +
> > if (err)
> > net_dbg_ratelimited("%s: packet transmission failed: %d\n",
> > __func__, err);
> >
>
> I think those need to be added to neigh_xmit in the
>
> if (likely(index < NEIGH_NR_TABLES)) {
>
> }
That'll force callers that don't need the extra protection (i.e.
mpls_forward(), since that always runs from softirq and it's enough
to protect the neigh state with rcu_read_lock() from softirq and we're
already running under rcu_read_lock() when we get to neigh_xmit()) to
eat the useless overhead of an extra rcu_read_{,un}lock_bh() pair, but
sure, functionally that's correct, I think, and in my workload I don't
care about MPLS forwarding performance anyway. ;-)
Want me to send a patch moving it to neigh_xmit() ?
Thank you for having a look!
Cheers,
Lennert
