ipv4: Fix "Set rt->rt_iif more sanely on output routes."

Commit 1018b5c016 ("Set rt->rt_iif more
sanely on output routes.")  breaks rt_is_{output,input}_route.

This became the cause to return "IP_PKTINFO's ->ipi_ifindex == 0".

To fix it, this does:

1) Add "int rt_route_iif;" to struct rtable

2) For input routes, always set rt_route_iif to same value as rt_iif

3) For output routes, always set rt_route_iif to zero.  Set rt_iif
   as it is done currently.

4) Change rt_is_{output,input}_route() to test rt_route_iif

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/route.h

@@ -64,6 +64,7 @@ struct rtable {
 
 	__be32			rt_dst;	/* Path destination	*/
 	__be32			rt_src;	/* Path source		*/
+	int			rt_route_iif;
 	int			rt_iif;
 	int			rt_oif;
 	__u32			rt_mark;
@@ -80,12 +81,12 @@ struct rtable {
 
 static inline bool rt_is_input_route(struct rtable *rt)
 {
-	return rt->rt_iif != 0;
+	return rt->rt_route_iif != 0;
 }
 
 static inline bool rt_is_output_route(struct rtable *rt)
 {
-	return rt->rt_iif == 0;
+	return rt->rt_route_iif == 0;
 }
 
 struct ip_rt_acct {

net/ipv4/route.c

@@ -1891,6 +1891,7 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 #ifdef CONFIG_IP_ROUTE_CLASSID
 	rth->dst.tclassid = itag;
 #endif
+	rth->rt_route_iif = dev->ifindex;
 	rth->rt_iif	= dev->ifindex;
 	rth->dst.dev	= init_net.loopback_dev;
 	dev_hold(rth->dst.dev);
@@ -2026,6 +2027,7 @@ static int __mkroute_input(struct sk_buff *skb,
 	rth->rt_key_src	= saddr;
 	rth->rt_src	= saddr;
 	rth->rt_gateway	= daddr;
+	rth->rt_route_iif = in_dev->dev->ifindex;
 	rth->rt_iif 	= in_dev->dev->ifindex;
 	rth->dst.dev	= (out_dev)->dev;
 	dev_hold(rth->dst.dev);
@@ -2202,6 +2204,7 @@ local_input:
 #ifdef CONFIG_IP_ROUTE_CLASSID
 	rth->dst.tclassid = itag;
 #endif
+	rth->rt_route_iif = dev->ifindex;
 	rth->rt_iif	= dev->ifindex;
 	rth->dst.dev	= net->loopback_dev;
 	dev_hold(rth->dst.dev);
@@ -2401,7 +2404,8 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
 	rth->rt_mark    = oldflp4->flowi4_mark;
 	rth->rt_dst	= fl4->daddr;
 	rth->rt_src	= fl4->saddr;
-	rth->rt_iif	= 0;
+	rth->rt_route_iif = 0;
+	rth->rt_iif	= oldflp4->flowi4_oif ? : dev_out->ifindex;
 	/* get references to the devices that are to be hold by the routing
 	   cache entry */
 	rth->dst.dev	= dev_out;
@@ -2716,6 +2720,7 @@ struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_or
 		rt->rt_key_dst = ort->rt_key_dst;
 		rt->rt_key_src = ort->rt_key_src;
 		rt->rt_tos = ort->rt_tos;
+		rt->rt_route_iif = ort->rt_route_iif;
 		rt->rt_iif = ort->rt_iif;
 		rt->rt_oif = ort->rt_oif;
 		rt->rt_mark = ort->rt_mark;
@@ -2725,7 +2730,6 @@ struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_or
 		rt->rt_type = ort->rt_type;
 		rt->rt_dst = ort->rt_dst;
 		rt->rt_src = ort->rt_src;
-		rt->rt_iif = ort->rt_iif;
 		rt->rt_gateway = ort->rt_gateway;
 		rt->rt_spec_dst = ort->rt_spec_dst;
 		rt->peer = ort->peer;

net/ipv4/xfrm4_policy.c

@@ -74,6 +74,7 @@ static int xfrm4_fill_dst(struct xfrm_dst *xdst, struct net_device *dev,
 	rt->rt_key_dst = fl4->daddr;
 	rt->rt_key_src = fl4->saddr;
 	rt->rt_tos = fl4->flowi4_tos;
+	rt->rt_route_iif = fl4->flowi4_iif;
 	rt->rt_iif = fl4->flowi4_iif;
 	rt->rt_oif = fl4->flowi4_oif;
 	rt->rt_mark = fl4->flowi4_mark;