[PATCH net-next 2/4] net: Do not route unicast IP packets twice

[Ido Schimmel]

Packets marked with 'offload_l3_fwd_mark' were already forwarded by a
capable device and should not be forwarded again by the kernel.
Therefore, have the kernel consume them.

The check is performed in ip{,6}_forward_finish() in order to allow the
kernel to process such packets in ip{,6}_forward() and generate required
exceptions. For example, ICMP redirects.

Signed-off-by: Ido Schimmel <ido...@mellanox.com>
---
 net/ipv4/ip_forward.c | 7 +++++++
 net/ipv6/ip6_output.c | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index 32662e9e5d21..06ee4696703c 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -69,6 +69,13 @@ static int ip_forward_finish(struct net *net, struct sock 
*sk, struct sk_buff *s
        __IP_INC_STATS(net, IPSTATS_MIB_OUTFORWDATAGRAMS);
        __IP_ADD_STATS(net, IPSTATS_MIB_OUTOCTETS, skb->len);
 
+#ifdef CONFIG_NET_SWITCHDEV
+       if (skb->offload_l3_fwd_mark) {
+               consume_skb(skb);
+               return 0;
+       }
+#endif
+
        if (unlikely(opt->optlen))
                ip_forward_options(skb);
 
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index ec8c235ea891..6592a39e5ec1 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -378,6 +378,13 @@ static inline int ip6_forward_finish(struct net *net, 
struct sock *sk,
        __IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTFORWDATAGRAMS);
        __IP6_ADD_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTOCTETS, 
skb->len);
 
+#ifdef CONFIG_NET_SWITCHDEV
+       if (skb->offload_l3_fwd_mark) {
+               consume_skb(skb);
+               return 0;
+       }
+#endif
+
        return dst_output(net, sk, skb);
 }
 
-- 
2.19.1