Merge branch 'mlxsw-Add-one-armed-router-support'

Ido Schimmel says:

====================
mlxsw: Add one-armed router support

Up until now, when a packet was routed by the ASIC through the same
router interface (RIF) from which it ingressed from, the ASIC passed the
sole copy of the packet to the kernel. This allowed the kernel to route
the packet and also potentially generate an ICMP redirect.

There are scenarios (e.g., "one-armed router") where packets are
intentionally routed this way and are therefore not deemed as
exceptions. In such scenarios the current method of trapping packets to
the CPU is problematic, as it results in major packet loss.

This patchset solves the problem by having the ASIC forward the packet,
but also send a copy to the CPU, which gives the kernel the opportunity
to generate required exceptions.

To prevent the kernel from forwarding such packets again, the driver
marks them with 'offload_l3_fwd_mark', which causes the kernel to
consume them in ip{,6}_forward_finish().

Patch #1 renames 'offload_mr_fwd_mark' to 'offload_l3_fwd_mark'. When
set, the field indicates that a packet was already forwarded in L3
(unicast / multicast) by a capable device.

Patch #2 teaches the kernel to consume unicast packets that have
'offload_l3_fwd_mark' set.

Patch #3 changes mlxsw to mirror loopbacked (iRIF == eRIF) packets,
instead of trapping them.

Patch #4 adds a test case for above mentioned scenario.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 16 insertions, 2 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c78ce114537e..40552547c69a 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4885,7 +4885,7 @@ void skb_scrub_packet(struct sk_buff *skb, bool xnet)
 
 #ifdef CONFIG_NET_SWITCHDEV
 	skb->offload_fwd_mark = 0;
-	skb->offload_mr_fwd_mark = 0;
+	skb->offload_l3_fwd_mark = 0;
 #endif
 
 	if (!xnet)
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/ipv4/ipmr.c b/net/ipv4/ipmr.c
index a6defbec4f1b..5cbc749a50aa 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1802,7 +1802,7 @@ static bool ipmr_forward_offloaded(struct sk_buff *skb, struct mr_table *mrt,
 	struct vif_device *out_vif = &mrt->vif_table[out_vifi];
 	struct vif_device *in_vif = &mrt->vif_table[in_vifi];
 
-	if (!skb->offload_mr_fwd_mark)
+	if (!skb->offload_l3_fwd_mark)
 		return false;
 	if (!out_vif->dev_parent_id.id_len || !in_vif->dev_parent_id.id_len)
 		return false;
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);
 }