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

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Date:   Tue, 4 Dec 2018 08:15:11 +0000
From:   Ido Schimmel <idosch@...lanox.com>
To:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>,
        "dsahern@...il.com" <dsahern@...il.com>,
        Alexander Petrovskiy <alexpe@...lanox.com>,
        "az@...tor.net" <az@...tor.net>, mlxsw <mlxsw@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>
Subject: [PATCH net-next 2/4] net: Do not route unicast IP packets twice

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 <idosch@...lanox.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