[PATCH] nft_flow_offload: Make flow offload work with vrf slave device correct

From: wenxu <redacted>

In the forward chain the iif is changed from slave device to master vrf
device. It will lead the offload not match on lower slave device.

This patch make the flollowing example can work correct

ip addr add dev eth0 1.1.1.1/24
ip addr add dev eth1 10.0.0.1/24
ip link add user1 type vrf table 1
ip l set user1 up
ip l set dev eth0 master user1
ip l set dev eth1 master user1

nft add table firewall
nft add flowtable f fb1 { hook ingress priority 0 \; devices = { eth0, eth1 } \; }
nft add chain f ftb-all {type filter hook forward priority 0 \; policy accept \; }
nft add rule f ftb-all ct zone 1 ip protocol tcp flow offload @fb1
nft add rule f ftb-all ct zone 1 ip protocol udp flow offload @fb1

Signed-off-by: wenxu <redacted>
---
 net/netfilter/nft_flow_offload.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nft_flow_offload.c b/net/netfilter/nft_flow_offload.c
index 974525e..a5995c0 100644
--- a/net/netfilter/nft_flow_offload.c
+++ b/net/netfilter/nft_flow_offload.c

@@ -30,9 +30,11 @@ static int nft_flow_route(const struct nft_pktinfo *pkt,
 	switch (nft_pf(pkt)) {
 	case NFPROTO_IPV4:
 		fl.u.ip4.daddr = ct->tuplehash[!dir].tuple.dst.u3.ip;
+		fl.u.ip4.flowi4_oif = nft_in(pkt)->ifindex;
 		break;
 	case NFPROTO_IPV6:
 		fl.u.ip6.daddr = ct->tuplehash[!dir].tuple.dst.u3.in6;
+		fl.u.ip6.flowi6_oif = nft_in(pkt)->ifindex;
 		break;
 	}
 

@@ -41,7 +43,15 @@ static int nft_flow_route(const struct nft_pktinfo *pkt,
 		return -ENOENT;
 
 	route->tuple[dir].dst		= this_dst;
-	route->tuple[dir].ifindex	= nft_in(pkt)->ifindex;
+	if (netif_is_l3_master(nft_in(pkt))) {
+		if (other_dst->dev)
+			route->tuple[dir].ifindex = other_dst->dev->ifindex;
+		else
+			route->tuple[dir].ifindex = nft_in(pkt)->ifindex;
+	} else {
+		route->tuple[dir].ifindex = nft_in(pkt)->ifindex;
+	}