[PATCH V2] ipv6: Fix problem with expired dst cache

[Gao feng <gaofeng@xxxxxxxxxxxxxx>]

If the ipv6 dst cache which copy from the dst generated by ICMPV6 RA packet.
this dst cache will not check expire because it has no RTF_EXPIRES flag.
So this dst cache will always be used until the dst gc run.

Change the struct dst_entry,add a union contains new pointer from and expires.
When rt6_info.rt6i_flags has no RTF_EXPIRES flag,the dst.expires has no use.
we can use this field to point to where the dst cache copy from.
The dst.from is only used in IPV6.

In func rt6_check_expired check if rt6_info.dst.from is expired.

In func ip6_rt_copy only set dst.from when the ort has flag RTF_ADDRCONF
and RTF_DEFAULT.

Signed-off-by: Gao feng <gaofeng@xxxxxxxxxxxxxx>
---
 include/net/dst.h |   11 ++++++++++-
 net/ipv6/route.c  |   22 +++++++++++++++++++---
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/include/net/dst.h b/include/net/dst.h
index 344c8dd..eae92f9 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -35,7 +35,16 @@ struct dst_entry {
 	struct net_device       *dev;
 	struct  dst_ops	        *ops;
 	unsigned long		_metrics;
-	unsigned long		expires;
+
+	union {
+		unsigned long		expires;
+		/*
+		 *from is used only for dst cache witch copy form
+		 *the dst generated by ipv6 RA.
+		 */
+		void			*from;
+	};
+
 	struct dst_entry	*path;
 	struct neighbour __rcu	*_neighbour;
 #ifdef CONFIG_XFRM
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 8c2e3ab..cd365fe 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -316,8 +316,18 @@ static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
 
 static __inline__ int rt6_check_expired(const struct rt6_info *rt)
 {
-	return (rt->rt6i_flags & RTF_EXPIRES) &&
-		time_after(jiffies, rt->dst.expires);
+	struct rt6_info *ort = NULL;
+
+	if (rt->rt6i_flags & RTF_EXPIRES) {
+		if (time_after(jiffies, rt->dst.expires))
+			return 1;
+	} else if (rt->dst.from) {
+		ort = (struct rt6_info *) rt->dst.from;
+		return (ort->rt6i_flags & RTF_EXPIRES) &&
+			time_after(jiffies, ort->dst.expires);
+	}
+
+	return 0;
 }
 
 static inline int rt6_need_strict(const struct in6_addr *daddr)
@@ -608,6 +618,7 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
 
 	if (rt) {
 		if (!addrconf_finite_timeout(lifetime)) {
+			rt->dst.expires = 0;
 			rt->rt6i_flags &= ~RTF_EXPIRES;
 		} else {
 			rt->dst.expires = jiffies + HZ * lifetime;
@@ -1799,7 +1810,12 @@ static struct rt6_info *ip6_rt_copy(const struct rt6_info *ort,
 		if (rt->rt6i_idev)
 			in6_dev_hold(rt->rt6i_idev);
 		rt->dst.lastuse = jiffies;
-		rt->dst.expires = 0;
+
+		if ((ort->rt6i_flags & (RTF_ADDRCONF | RTF_DEFAULT)) ==
+		    (RTF_ADDRCONF | RTF_DEFAULT))
+			rt->dst.from = (void *)ort;
+		else
+			rt->dst.expires = 0;
 
 		rt->rt6i_gateway = ort->rt6i_gateway;
 		rt->rt6i_flags = ort->rt6i_flags & ~RTF_EXPIRES;
-- 
1.7.5.4

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