From 5071034e4af709d6783b7d105dc296a5cc84739b Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Fri, 2 Jun 2017 09:01:49 -0700 Subject: neigh: Really delete an arp/neigh entry on "ip neigh delete" or "arp -d" The command # arp -s 62.2.0.1 a:b:c:d:e:f dev eth2 adds an entry like the following (listed by "arp -an") ? (62.2.0.1) at 0a:0b:0c:0d:0e:0f [ether] PERM on eth2 but the symmetric deletion command # arp -i eth2 -d 62.2.0.1 does not remove the PERM entry from the table, and instead leaves behind ? (62.2.0.1) at on eth2 The reason is that there is a refcnt of 1 for the arp_tbl itself (neigh_alloc starts off the entry with a refcnt of 1), thus the neigh_release() call from arp_invalidate() will (at best) just decrement the ref to 1, but will never actually free it from the table. To fix this, we need to do something like neigh_forced_gc: if the refcnt is 1 (i.e., on the table's ref), remove the entry from the table and free it. This patch refactors and shares common code between neigh_forced_gc and the newly added neigh_remove_one. A similar issue exists for IPv6 Neighbor Cache entries, and is fixed in a similar manner by this patch. Signed-off-by: Sowmini Varadhan Reviewed-by: Julian Anastasov Signed-off-by: David S. Miller --- net/ipv4/arp.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'net/ipv4/arp.c') diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index e9f3386a528b..a651c53260ec 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c @@ -1113,13 +1113,17 @@ static int arp_invalidate(struct net_device *dev, __be32 ip) { struct neighbour *neigh = neigh_lookup(&arp_tbl, &ip, dev); int err = -ENXIO; + struct neigh_table *tbl = &arp_tbl; if (neigh) { if (neigh->nud_state & ~NUD_NOARP) err = neigh_update(neigh, NULL, NUD_FAILED, NEIGH_UPDATE_F_OVERRIDE| NEIGH_UPDATE_F_ADMIN, 0); + write_lock_bh(&tbl->lock); neigh_release(neigh); + neigh_remove_one(neigh, tbl); + write_unlock_bh(&tbl->lock); } return err; -- cgit v1.2.3-58-ga151