ipv4: Fix flushing of cached routing informations

Currently we can not flush cached pmtu/redirect informations via
the ipv4_sysctl_rtcache_flush sysctl. We need to check the rt_genid
of the old route and reset the nh exeption if the old route is
expired when we bind a new route to a nh exeption.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 3 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 432f4bb77238..a8c651216fa6 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1163,8 +1163,12 @@ static bool rt_bind_exception(struct rtable *rt, struct fib_nh_exception *fnhe,
         spin_lock_bh(&fnhe_lock);
 
         if (daddr == fnhe->fnhe_daddr) {
-                struct rtable *orig;
-
+                struct rtable *orig = rcu_dereference(fnhe->fnhe_rth);
+                if (orig && rt_is_expired(orig)) {
+                        fnhe->fnhe_gw = 0;
+                        fnhe->fnhe_pmtu = 0;
+                        fnhe->fnhe_expires = 0;
+                }
                 if (fnhe->fnhe_pmtu) {
                         unsigned long expires = fnhe->fnhe_expires;
                         unsigned long diff = expires - jiffies;
@@ -1181,7 +1185,6 @@ static bool rt_bind_exception(struct rtable *rt, struct fib_nh_exception *fnhe,
                 } else if (!rt->rt_gateway)
                         rt->rt_gateway = daddr;
 
-                orig = rcu_dereference(fnhe->fnhe_rth);
                 rcu_assign_pointer(fnhe->fnhe_rth, rt);
                 if (orig)
                         rt_free(orig);