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| author | He Chunhui <hchunhui@mail.ustc.edu.cn> | 2016-07-26 06:16:52 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-07-26 14:25:20 -0700 |
| commit | d1c2b5010d07e967d7cbcc232a86b2308d824ca3 (patch) | |
| tree | 9deefa7e8dcb6a4756e6c7faadb0ca2ab1128e1a /net | |
| parent | ee591f46a5a0ca0caaeb72b79ec5e012c6e3c9ef (diff) | |
| download | linux-d1c2b5010d07e967d7cbcc232a86b2308d824ca3.tar.bz2 | |
net: neigh: disallow transition to NUD_STALE if lladdr is unchanged in neigh_update()
NUD_STALE is used when the caller(e.g. arp_process()) can't guarantee
neighbour reachability. If the entry was NUD_VALID and lladdr is unchanged,
the entry state should not be changed.
Currently the code puts an extra "NUD_CONNECTED" condition. So if old state
was NUD_DELAY or NUD_PROBE (they are NUD_VALID but not NUD_CONNECTED), the
state can be changed to NUD_STALE.
This may cause problem. Because NUD_STALE lladdr doesn't guarantee
reachability, when we send traffic, the state will be changed to
NUD_DELAY. In normal case, if we get no confirmation (by dst_confirm()),
we will change the state to NUD_PROBE and send probe traffic. But now the
state may be reset to NUD_STALE again(e.g. by broadcast ARP packets),
so the probe traffic will not be sent. This situation may happen again and
again, and packets will be sent to an non-reachable lladdr forever.
The fix is to remove the "NUD_CONNECTED" condition. After that the
"NEIGH_UPDATE_F_WEAK_OVERRIDE" condition (used by IPv6) in that branch will
be redundant, so remove it.
This change may increase probe traffic, but it's essential since NUD_STALE
lladdr is unreliable. To ensure correctness, we prefer to resolve lladdr,
when we can't get confirmation, even while remote packets try to set
NUD_STALE state.
Signed-off-by: Chunhui He <hchunhui@mail.ustc.edu.cn>
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/neighbour.c | 7 |
1 files changed, 1 insertions, 6 deletions
diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 5cdc62a8eb84..cf26e04c4046 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1060,8 +1060,6 @@ static void neigh_update_hhs(struct neighbour *neigh) NEIGH_UPDATE_F_WEAK_OVERRIDE will suspect existing "connected" lladdr instead of overriding it if it is different. - It also allows to retain current state - if lladdr is unchanged. NEIGH_UPDATE_F_ADMIN means that the change is administrative. NEIGH_UPDATE_F_OVERRIDE_ISROUTER allows to override existing @@ -1150,10 +1148,7 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new, } else goto out; } else { - if (lladdr == neigh->ha && new == NUD_STALE && - ((flags & NEIGH_UPDATE_F_WEAK_OVERRIDE) || - (old & NUD_CONNECTED)) - ) + if (lladdr == neigh->ha && new == NUD_STALE) new = old; } } |