[IPV6]: Do not update MTU by invalid value in RA message.

Noticed by HIroaki Kago <kago@jp.fujitsu.com>

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 151add4d77d268cce30374388270def3b1603970..0309a24a367e6571dbd6149fdad006b5d4baf47c 100644 (file)
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1166,9 +1166,7 @@ static void ndisc_router_discovery(struct sk_buff *skb)
                                ND_PRINTK0("NDISC: router announcement with mtu = %d\n",
                                           mtu);
                        }
-               }
-
-               if (in6_dev->cnf.mtu6 != mtu) {
+               } else if (in6_dev->cnf.mtu6 != mtu) {
                        in6_dev->cnf.mtu6 = mtu;
 
                        if (rt)