[ 70/85] ipv4: Dont report stale pmtu values to userspace

[Greg Kroah-Hartman]

3.6-stable review patch.  If anyone has any objections, please let me know.

------------------


From: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>

[ Upstream commit ee9a8f7ab2edf801b8b514c310455c94acc232f6 ]

We report cached pmtu values even if they are already expired.
Change this to not report these values after they are expired
and fix a race in the expire time calculation, as suggested by
Eric Dumazet.

Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv4/route.c |   19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2187,8 +2187,18 @@ static int rt_fill_info(struct net *net,
 	    nla_put_be32(skb, RTA_GATEWAY, rt->rt_gateway))
 		goto nla_put_failure;
 
+	expires = rt->dst.expires;
+	if (expires) {
+		unsigned long now = jiffies;
+
+		if (time_before(now, expires))
+			expires -= now;
+		else
+			expires = 0;
+	}
+
 	memcpy(metrics, dst_metrics_ptr(&rt->dst), sizeof(metrics));
-	if (rt->rt_pmtu)
+	if (rt->rt_pmtu && expires)
 		metrics[RTAX_MTU - 1] = rt->rt_pmtu;
 	if (rtnetlink_put_metrics(skb, metrics) < 0)
 		goto nla_put_failure;
@@ -2198,13 +2208,6 @@ static int rt_fill_info(struct net *net,
 		goto nla_put_failure;
 
 	error = rt->dst.error;
-	expires = rt->dst.expires;
-	if (expires) {
-		if (time_before(jiffies, expires))
-			expires -= jiffies;
-		else
-			expires = 0;
-	}
 
 	if (rt_is_input_route(rt)) {
 		if (nla_put_u32(skb, RTA_IIF, rt->rt_iif))


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