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

Commit 1018b5c01636c7c6bda31a719bda34fc631db29a ("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>

1 files changed, 6 insertions, 2 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 4b0c81180804..1628be530314 100644
--- a/net/ipv4/route.c
+++ b/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;