From 5071034e4af709d6783b7d105dc296a5cc84739b Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Fri, 2 Jun 2017 09:01:49 -0700 Subject: [PATCH] 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 --- include/net/neighbour.h | 1 + net/core/neighbour.c | 60 +++++++++++++++++++++++++++++++++-------- net/ipv4/arp.c | 4 +++ 3 files changed, 54 insertions(+), 11 deletions(-) diff --git a/include/net/neighbour.h b/include/net/neighbour.h index e4dd3a214034..639b67564a7d 100644 --- a/include/net/neighbour.h +++ b/include/net/neighbour.h @@ -317,6 +317,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb); int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new, u32 flags, u32 nlmsg_pid); void __neigh_set_probe_once(struct neighbour *neigh); +bool neigh_remove_one(struct neighbour *ndel, struct neigh_table *tbl); void neigh_changeaddr(struct neigh_table *tbl, struct net_device *dev); int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev); int neigh_resolve_output(struct neighbour *neigh, struct sk_buff *skb); diff --git a/net/core/neighbour.c b/net/core/neighbour.c index d274f81fcc2c..dadb5eef91c3 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -118,6 +118,50 @@ unsigned long neigh_rand_reach_time(unsigned long base) EXPORT_SYMBOL(neigh_rand_reach_time); +static bool neigh_del(struct neighbour *n, __u8 state, + struct neighbour __rcu **np, struct neigh_table *tbl) +{ + bool retval = false; + + write_lock(&n->lock); + if (atomic_read(&n->refcnt) == 1 && !(n->nud_state & state)) { + struct neighbour *neigh; + + neigh = rcu_dereference_protected(n->next, + lockdep_is_held(&tbl->lock)); + rcu_assign_pointer(*np, neigh); + n->dead = 1; + retval = true; + } + write_unlock(&n->lock); + if (retval) + neigh_cleanup_and_release(n); + return retval; +} + +bool neigh_remove_one(struct neighbour *ndel, struct neigh_table *tbl) +{ + struct neigh_hash_table *nht; + void *pkey = ndel->primary_key; + u32 hash_val; + struct neighbour *n; + struct neighbour __rcu **np; + + nht = rcu_dereference_protected(tbl->nht, + lockdep_is_held(&tbl->lock)); + hash_val = tbl->hash(pkey, ndel->dev, nht->hash_rnd); + hash_val = hash_val >> (32 - nht->hash_shift); + + np = &nht->hash_buckets[hash_val]; + while ((n = rcu_dereference_protected(*np, + lockdep_is_held(&tbl->lock)))) { + if (n == ndel) + return neigh_del(n, 0, np, tbl); + np = &n->next; + } + return false; +} + static int neigh_forced_gc(struct neigh_table *tbl) { int shrunk = 0; @@ -140,19 +184,10 @@ static int neigh_forced_gc(struct neigh_table *tbl) * - nobody refers to it. * - it is not permanent */ - write_lock(&n->lock); - if (atomic_read(&n->refcnt) == 1 && - !(n->nud_state & NUD_PERMANENT)) { - rcu_assign_pointer(*np, - rcu_dereference_protected(n->next, - lockdep_is_held(&tbl->lock))); - n->dead = 1; - shrunk = 1; - write_unlock(&n->lock); - neigh_cleanup_and_release(n); + if (neigh_del(n, NUD_PERMANENT, np, tbl)) { + shrunk = 1; continue; } - write_unlock(&n->lock); np = &n->next; } } @@ -1649,7 +1684,10 @@ static int neigh_delete(struct sk_buff *skb, struct nlmsghdr *nlh, NEIGH_UPDATE_F_OVERRIDE | NEIGH_UPDATE_F_ADMIN, NETLINK_CB(skb).portid); + write_lock_bh(&tbl->lock); neigh_release(neigh); + neigh_remove_one(neigh, tbl); + write_unlock_bh(&tbl->lock); out: return err; 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; -- 2.20.1