neigh: Better handling of transition to NUD_PROBE state

[1] When entering NUD_PROBE state via neigh_update(), perhaps received
    from userspace, correctly (re)initialize the probes count to zero.

    This is useful for forcing revalidation of a neighbor (for example
    if the host is attempting to do DNA [IPv4 4436, IPv6 6059]).

[2] Notify listeners when a neighbor goes into NUD_PROBE state.

    By sending notifications on entry to NUD_PROBE state listeners get
    more timely warnings of imminent connectivity issues.

    The current notifications on entry to NUD_STALE have somewhat
    limited usefulness: NUD_STALE is a perfectly normal state, as is
    NUD_DELAY, whereas notifications on entry to NUD_FAILURE come after
    a neighbor reachability problem has been confirmed (typically after
    three probes).

Signed-off-by: Erik Kline <ek@google.com>
Acked-By: Lorenzo Colitti <lorenzo@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 3de6542560288b3896ab243879a7b4a9b098ca0d..3a74df750af4044eba0e7d88ae01ca9b4dac0e72 100644 (file)
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -913,6 +913,7 @@ static void neigh_timer_handler(unsigned long arg)
                        neigh->nud_state = NUD_PROBE;
                        neigh->updated = jiffies;
                        atomic_set(&neigh->probes, 0);
+                       notify = 1;
                        next = now + NEIGH_VAR(neigh->parms, RETRANS_TIME);
                }
        } else {
@@ -1144,6 +1145,8 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new,
 
        if (new != old) {
                neigh_del_timer(neigh);
+               if (new & NUD_PROBE)
+                       atomic_set(&neigh->probes, 0);
                if (new & NUD_IN_TIMER)
                        neigh_add_timer(neigh, (jiffies +
                                                ((new & NUD_REACHABLE) ?