net: l3mdev: Add hook in ip and ipv6

Currently the VRF driver uses the rx_handler to switch the skb device
to the VRF device. Switching the dev prior to the ip / ipv6 layer
means the VRF driver has to duplicate IP/IPv6 processing which adds
overhead and makes features such as retaining the ingress device index
more complicated than necessary.

This patch moves the hook to the L3 layer just after the first NF_HOOK
for PRE_ROUTING. This location makes exposing the original ingress device
trivial (next patch) and allows adding other NF_HOOKs to the VRF driver
in the future.

dev_queue_xmit_nit is exported so that the VRF driver can cycle the skb
with the switched device through the packet taps to maintain current
behavior (tcpdump can be used on either the vrf device or the enslaved
devices).

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 1 deletions

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 58d6e158755f..5c91b0b055d4 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -118,14 +118,29 @@ struct inet6_skb_parm {
 #define IP6SKB_ROUTERALERT	8
 #define IP6SKB_FRAGMENTED      16
 #define IP6SKB_HOPBYHOP        32
+#define IP6SKB_L3SLAVE         64
 };
 
+#if defined(CONFIG_NET_L3_MASTER_DEV)
+static inline bool skb_l3mdev_slave(__u16 flags)
+{
+	return flags & IP6SKB_L3SLAVE;
+}
+#else
+static inline bool skb_l3mdev_slave(__u16 flags)
+{
+	return false;
+}
+#endif
+
 #define IP6CB(skb)	((struct inet6_skb_parm*)((skb)->cb))
 #define IP6CBMTU(skb)	((struct ip6_mtuinfo *)((skb)->cb))
 
 static inline int inet6_iif(const struct sk_buff *skb)
 {
-	return IP6CB(skb)->iif;
+	bool l3_slave = skb_l3mdev_slave(IP6CB(skb)->flags);
+
+	return l3_slave ? skb->skb_iif : IP6CB(skb)->iif;
 }
 
 struct tcp6_request_sock {