Re: [RFC] ipv6: gro: IPV6_GRO_CB(skb)->proto problem

On Sun, 2012-10-07 at 12:27 +0800, Herbert Xu wrote:

On Sat, Oct 06, 2012 at 09:15:27PM +0200, Eric Dumazet wrote:

quoted

It seems IPV6_GRO_CB(skb)->proto can be destroyed in skb_gro_receive()
if a new skb is allocated (to serve as an anchor for frag_list)

At line 3049 we copy NAPI_GRO_CB() only (not the IPV6 specific part)

*NAPI_GRO_CB(nskb) = *NAPI_GRO_CB(p);

So we leave IPV6_GRO_CB(nskb)->proto to 0 (fresh skb allocation) instead
of PROTO_TCP

So ipv6_gro_complete() wont be able to call ops->gro_complete()
[ tcp6_gro_complete() ]

I would fix this by moving proto in NAPI_GRO_CB() [ ie getting rid of
IPV6_GRO_CB ]

Am I missing something ?

(I'll submit a proper patch once/if prior GRO ones are accepted/merged
by David)

No I think you're absolutely right.

quoted

 include/linux/netdevice.h |    2 ++
 net/ipv6/af_inet6.c       |   11 ++---------
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 01646aa..3f13441 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h

@@ -1510,6 +1510,8 @@ struct napi_gro_cb {
 	int free;
 #define NAPI_GRO_FREE		  1
 #define NAPI_GRO_FREE_STOLEN_HEAD 2
+
+	u8 proto;

I'd prefer to keep it as an int since we're not really running
short on space.

Sure I can do that for stable anyway, but when net-next is open, I'll
submit the patch to use a hash table, and I'll need one more pointer in
this structure.

On 64bit we reach current cb[48] limit...

(skb->next/skb->prev will be used for the global chain, gro_list becomes
a list_head, and each hash chain will use a pointer in napi_gro_cb

(I'll probably use a u32 instead of "unsigned long" for the age)

Thanks