Re: [PATCH nf v2 1/3] netfilter: nf_flow_table_offload: fix dst_neigh lookup

[Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>]

On Tue, Dec 17, 2019 at 04:52:45PM +0800, wenxu@xxxxxxxxx wrote:
> From: wenxu <wenxu@xxxxxxxxx>
> 
> Get the dst_neigh through dst_ip, The dst_ip should get
> through peer tuple.src_v4 fix for dnat case.

Please, revamp patch description:

        netfilter: nf_flow_table_offload: fix incorrect ethernet dst address

Proposed description:

        original:       A -> FW
        reply:          B -> A

        Traffic going in original direction uses address B as
        destination. Traffic going in reply direction uses address A
        as destination.

I'd suggest a more simplified patch, attached.

diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index 506aaaf8151d..8680fc56cd7c 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -156,14 +156,14 @@ static int flow_offload_eth_dst(struct net *net,
 				enum flow_offload_tuple_dir dir,
 				struct nf_flow_rule *flow_rule)
 {
-	const struct flow_offload_tuple *tuple = &flow->tuplehash[dir].tuple;
+	const struct flow_offload_tuple *tuple = &flow->tuplehash[!dir].tuple;
 	struct flow_action_entry *entry0 = flow_action_entry_next(flow_rule);
 	struct flow_action_entry *entry1 = flow_action_entry_next(flow_rule);
 	struct neighbour *n;
 	u32 mask, val;
 	u16 val16;
 
-	n = dst_neigh_lookup(tuple->dst_cache, &tuple->dst_v4);
+	n = dst_neigh_lookup(tuple->dst_cache, &tuple->src_v4);
 	if (!n)
 		return -ENOENT;