neighbor: Remove externally learned entries from gc_list

Externally learned entries are similar to PERMANENT entries in the
sense they are managed by userspace and can not be garbage collected.
As such remove them from the gc_list, remove the flags check from
neigh_forced_gc and skip threshold checks in neigh_alloc. As with
PERMANENT entries, this allows unlimited number of NTF_EXT_LEARNED
entries.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 2401040..42b4137 100644 (file)
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -129,21 +129,22 @@ static void neigh_mark_dead(struct neighbour *n)
 
 static void neigh_update_gc_list(struct neighbour *n)
 {
-       bool on_gc_list, new_is_perm;
+       bool on_gc_list, exempt_from_gc;
 
        write_lock_bh(&n->tbl->lock);
        write_lock(&n->lock);
 
-       /* remove from the gc list if new state is permanent;
-        * add to the gc list if new state is not permanent
+       /* remove from the gc list if new state is permanent or if neighbor
+        * is externally learned; otherwise entry should be on the gc list
         */
-       new_is_perm = n->nud_state & NUD_PERMANENT;
+       exempt_from_gc = n->nud_state & NUD_PERMANENT ||
+                        n->flags & NTF_EXT_LEARNED;
        on_gc_list = !list_empty(&n->gc_list);
 
-       if (new_is_perm && on_gc_list) {
+       if (exempt_from_gc && on_gc_list) {
                list_del_init(&n->gc_list);
                atomic_dec(&n->tbl->gc_entries);
-       } else if (!new_is_perm && !on_gc_list) {
+       } else if (!exempt_from_gc && !on_gc_list) {
                /* add entries to the tail; cleaning removes from the front */
                list_add_tail(&n->gc_list, &n->tbl->gc_list);
                atomic_inc(&n->tbl->gc_entries);
@@ -153,13 +154,14 @@ static void neigh_update_gc_list(struct neighbour *n)
        write_unlock_bh(&n->tbl->lock);
 }
 
-static void neigh_update_ext_learned(struct neighbour *neigh, u32 flags,
+static bool neigh_update_ext_learned(struct neighbour *neigh, u32 flags,
                                     int *notify)
 {
+       bool rc = false;
        u8 ndm_flags;
 
        if (!(flags & NEIGH_UPDATE_F_ADMIN))
-               return;
+               return rc;
 
        ndm_flags = (flags & NEIGH_UPDATE_F_EXT_LEARNED) ? NTF_EXT_LEARNED : 0;
        if ((neigh->flags ^ ndm_flags) & NTF_EXT_LEARNED) {
@@ -167,8 +169,11 @@ static void neigh_update_ext_learned(struct neighbour *neigh, u32 flags,
                        neigh->flags |= NTF_EXT_LEARNED;
                else
                        neigh->flags &= ~NTF_EXT_LEARNED;
+               rc = true;
                *notify = 1;
        }
+
+       return rc;
 }
 
 static bool neigh_del(struct neighbour *n, struct neighbour __rcu **np,
@@ -219,7 +224,6 @@ static int neigh_forced_gc(struct neigh_table *tbl)
 {
        int max_clean = atomic_read(&tbl->gc_entries) - tbl->gc_thresh2;
        unsigned long tref = jiffies - 5 * HZ;
-       u8 flags = NTF_EXT_LEARNED;
        struct neighbour *n, *tmp;
        int shrunk = 0;
 
@@ -233,7 +237,7 @@ static int neigh_forced_gc(struct neigh_table *tbl)
 
                        write_lock(&n->lock);
                        if ((n->nud_state == NUD_FAILED) ||
-                           (!(n->flags & flags) && time_after(tref, n->updated)))
+                           time_after(tref, n->updated))
                                remove = true;
                        write_unlock(&n->lock);
 
@@ -371,13 +375,13 @@ EXPORT_SYMBOL(neigh_ifdown);
 
 static struct neighbour *neigh_alloc(struct neigh_table *tbl,
                                     struct net_device *dev,
-                                    bool permanent)
+                                    bool exempt_from_gc)
 {
        struct neighbour *n = NULL;
        unsigned long now = jiffies;
        int entries;
 
-       if (permanent)
+       if (exempt_from_gc)
                goto do_alloc;
 
        entries = atomic_inc_return(&tbl->gc_entries) - 1;
@@ -419,7 +423,7 @@ out:
        return n;
 
 out_entries:
-       if (!permanent)
+       if (!exempt_from_gc)
                atomic_dec(&tbl->gc_entries);
        goto out;
 }
@@ -566,9 +570,9 @@ EXPORT_SYMBOL(neigh_lookup_nodev);
 static struct neighbour *___neigh_create(struct neigh_table *tbl,
                                         const void *pkey,
                                         struct net_device *dev,
-                                        bool permanent, bool want_ref)
+                                        bool exempt_from_gc, bool want_ref)
 {
-       struct neighbour *n1, *rc, *n = neigh_alloc(tbl, dev, permanent);
+       struct neighbour *n1, *rc, *n = neigh_alloc(tbl, dev, exempt_from_gc);
        u32 hash_val;
        unsigned int key_len = tbl->key_len;
        int error;
@@ -634,7 +638,7 @@ static struct neighbour *___neigh_create(struct neigh_table *tbl,
        }
 
        n->dead = 0;
-       if (!permanent)
+       if (!exempt_from_gc)
                list_add_tail(&n->gc_list, &n->tbl->gc_list);
 
        if (want_ref)
@@ -1210,6 +1214,7 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
                          u8 new, u32 flags, u32 nlmsg_pid,
                          struct netlink_ext_ack *extack)
 {
+       bool ext_learn_change = false;
        u8 old;
        int err;
        int notify = 0;
@@ -1230,7 +1235,7 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
                goto out;
        }
 
-       neigh_update_ext_learned(neigh, flags, &notify);
+       ext_learn_change = neigh_update_ext_learned(neigh, flags, &notify);
 
        if (!(new & NUD_VALID)) {
                neigh_del_timer(neigh);
@@ -1376,7 +1381,7 @@ out:
                neigh_update_is_router(neigh, flags, &notify);
        write_unlock_bh(&neigh->lock);
 
-       if ((new ^ old) & NUD_PERMANENT)
+       if (((new ^ old) & NUD_PERMANENT) || ext_learn_change)
                neigh_update_gc_list(neigh);
 
        if (notify)
@@ -1881,14 +1886,16 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 
        neigh = neigh_lookup(tbl, dst, dev);
        if (neigh == NULL) {
+               bool exempt_from_gc;
+
                if (!(nlh->nlmsg_flags & NLM_F_CREATE)) {
                        err = -ENOENT;
                        goto out;
                }
 
-               neigh = ___neigh_create(tbl, dst, dev,
-                                       ndm->ndm_state & NUD_PERMANENT,
-                                       true);
+               exempt_from_gc = ndm->ndm_state & NUD_PERMANENT ||
+                                ndm->ndm_flags & NTF_EXT_LEARNED;
+               neigh = ___neigh_create(tbl, dst, dev, exempt_from_gc, true);
                if (IS_ERR(neigh)) {
                        err = PTR_ERR(neigh);
                        goto out;