ipv6: flush nd cache on IFF_NOARP change

This patch is the IPv6 equivalent of commit
6c8b4e3ff81b ("arp: flush arp cache on IFF_NOARP change")

Without it, we keep buggy neighbours in the cache, with destination
MAC address equal to our own MAC address.

Tested:
 tcpdump -i eth0 -s 0 ip6 -n -e &
 ip link set dev eth0 arp off
 ping6 remote   // sends buggy frames
 ip link set dev eth0 arp on
 ping6 remote   // should work once kernel is patched

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Mario Fanelli <mariofanelli@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 0a05b35a90fc..c53331cfed95 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1650,6 +1650,7 @@ int ndisc_rcv(struct sk_buff *skb)
 static int ndisc_netdev_event(struct notifier_block *this, unsigned long event, void *ptr)
 {
         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+        struct netdev_notifier_change_info *change_info;
         struct net *net = dev_net(dev);
         struct inet6_dev *idev;
 
@@ -1664,6 +1665,11 @@ static int ndisc_netdev_event(struct notifier_block *this, unsigned long event,
                         ndisc_send_unsol_na(dev);
                 in6_dev_put(idev);
                 break;
+        case NETDEV_CHANGE:
+                change_info = ptr;
+                if (change_info->flags_changed & IFF_NOARP)
+                        neigh_changeaddr(&nd_tbl, dev);
+                break;
         case NETDEV_DOWN:
                 neigh_ifdown(&nd_tbl, dev);
                 fib6_run_gc(0, net, false);