On Fri, 2015-07-31 at 12:17 +0200, Eric Dumazet wrote:
> On Thu, 2015-07-30 at 22:29 +0000, Gregory Hoggarth wrote:
> > Hi Eric,
> >
> > Thanks for the patch. I have put this into our code and we'll run our test
> > over tonight and the weekend and report back on Monday.
> >
> > Thanks,
>
> Oh well, real fix will be :
>
> (Or at least test if DST_NOCACHE is set : those dst need special care)
Here is a more complete patch, not destroying performance of unicast
UDP.
Please guys test it, I am confident it should solve your problems.
Thanks
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 83aa604f9273..1b8c5ba7d5f7 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1995,12 +1995,19 @@ void udp_v4_early_demux(struct sk_buff *skb)
skb->sk = sk;
skb->destructor = sock_efree;
- dst = sk->sk_rx_dst;
+ dst = READ_ONCE(sk->sk_rx_dst);
if (dst)
dst = dst_check(dst, 0);
- if (dst)
- skb_dst_set_noref(skb, dst);
+ if (dst) {
+ /* DST_NOCACHE can not be used without taking a reference */
+ if (dst->flags & DST_NOCACHE) {
+ if (likely(atomic_inc_not_zero(&dst->__refcnt)))
+ skb_dst_set(skb, dst);
+ } else {
+ skb_dst_set_noref(skb, dst);
+ }
+ }
}
int udp_rcv(struct sk_buff *skb)
--
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