From: Phil Sutter <phil@nwl.cc>
Date: Tue, 12 Nov 2019 17:14:37 +0100
Subject: netfilter: Support iif matches in POSTROUTING
Patch-mainline: v5.5-rc1
Git-commit: 28f8bfd1ac948403ebd5c8070ae1e25421560059
References: bsc#1176447

Instead of generally passing NULL to NF_HOOK_COND() for input device,
pass skb->dev which contains input device for routed skbs.

Note that iptables (both legacy and nft) reject rules with input
interface match from being added to POSTROUTING chains, but nftables
allows this.

Cc: Eric Garver <eric@garver.life>
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/ipv4/ip_output.c    |    4 ++--
 net/ipv4/xfrm4_output.c |    2 +-
 net/ipv6/ip6_output.c   |    4 ++--
 net/ipv6/xfrm6_output.c |    2 +-
 4 files changed, 6 insertions(+), 6 deletions(-)

--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -422,7 +422,7 @@ int ip_mc_output(struct net *net, struct
 
 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
-	struct net_device *dev = skb_dst(skb)->dev;
+	struct net_device *dev = skb_dst(skb)->dev, *indev = skb->dev;
 
 	IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
 
@@ -430,7 +430,7 @@ int ip_output(struct net *net, struct so
 	skb->protocol = htons(ETH_P_IP);
 
 	return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
-			    net, sk, skb, NULL, dev,
+			    net, sk, skb, indev, dev,
 			    ip_finish_output,
 			    !(IPCB(skb)->flags & IPSKB_REROUTED));
 }
--- a/net/ipv4/xfrm4_output.c
+++ b/net/ipv4/xfrm4_output.c
@@ -92,7 +92,7 @@ static int __xfrm4_output(struct net *ne
 int xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
-			    net, sk, skb, NULL, skb_dst(skb)->dev,
+			    net, sk, skb, skb->dev, skb_dst(skb)->dev,
 			    __xfrm4_output,
 			    !(IPCB(skb)->flags & IPSKB_REROUTED));
 }
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -160,7 +160,7 @@ static int ip6_finish_output(struct net
 
 int ip6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
-	struct net_device *dev = skb_dst(skb)->dev;
+	struct net_device *dev = skb_dst(skb)->dev, *indev = skb->dev;
 	struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb));
 
 	skb->protocol = htons(ETH_P_IPV6);
@@ -173,7 +173,7 @@ int ip6_output(struct net *net, struct s
 	}
 
 	return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING,
-			    net, sk, skb, NULL, dev,
+			    net, sk, skb, indev, dev,
 			    ip6_finish_output,
 			    !(IP6CB(skb)->flags & IP6SKB_REROUTED));
 }
--- a/net/ipv6/xfrm6_output.c
+++ b/net/ipv6/xfrm6_output.c
@@ -187,7 +187,7 @@ skip_frag:
 int xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING,
-			    net, sk, skb,  NULL, skb_dst(skb)->dev,
+			    net, sk, skb,  skb->dev, skb_dst(skb)->dev,
 			    __xfrm6_output,
 			    !(IP6CB(skb)->flags & IP6SKB_REROUTED));
 }