neighbour: add support for NUD_PERMANENT proxy entries

[ Upstream commit c7d78566bbd30544a0618a6ffbc97bc0ddac7035 ]

As discussesd before in [0] proxy entries (which are more configuration
than runtime data) should stay when the link (carrier) goes does down.
This is what happens for regular neighbour entries.

So lets fix this by:
  - storing in proxy entries the fact that it was added as NUD_PERMANENT
  - not removing NUD_PERMANENT proxy entries when the carrier goes down
    (same as how it's done in neigh_flush_dev() for regular neigh entries)

[0]: https://lore.kernel.org/netdev/c584ef7e-6897-01f3-5b80-12b53f7b4bf4@kernel.org/

Signed-off-by: Nicolas Escande <nico.escande@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250617141334.3724863-1-nico.escande@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index ccc4a0f8b4ad8ba98e04fff7c559122b93224527..93aecfaa7628a7c34247341b11295dd1812e608d 100644 (file)
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -180,6 +180,7 @@ struct pneigh_entry {
        netdevice_tracker       dev_tracker;
        u32                     flags;
        u8                      protocol;
+       bool                    permanent;
        u32                     key[];
 };
 

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index bcc3950638b91130b5b6fb765af8a123c3b7f19b..92dc1f1788de7e597975ee3e449bc795fde98ca2 100644 (file)
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -55,7 +55,8 @@ static void __neigh_notify(struct neighbour *n, int type, int flags,
                           u32 pid);
 static void neigh_update_notify(struct neighbour *neigh, u32 nlmsg_pid);
 static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
-                                   struct net_device *dev);
+                                   struct net_device *dev,
+                                   bool skip_perm);
 
 #ifdef CONFIG_PROC_FS
 static const struct seq_operations neigh_stat_seq_ops;
@@ -444,7 +445,7 @@ static int __neigh_ifdown(struct neigh_table *tbl, struct net_device *dev,
 {
        write_lock_bh(&tbl->lock);
        neigh_flush_dev(tbl, dev, skip_perm);
-       pneigh_ifdown_and_unlock(tbl, dev);
+       pneigh_ifdown_and_unlock(tbl, dev, skip_perm);
        pneigh_queue_purge(&tbl->proxy_queue, dev ? dev_net(dev) : NULL,
                           tbl->family);
        if (skb_queue_empty_lockless(&tbl->proxy_queue))
@@ -845,7 +846,8 @@ int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *pkey,
 }
 
 static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
-                                   struct net_device *dev)
+                                   struct net_device *dev,
+                                   bool skip_perm)
 {
        struct pneigh_entry *n, **np, *freelist = NULL;
        u32 h;
@@ -853,12 +855,15 @@ static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
        for (h = 0; h <= PNEIGH_HASHMASK; h++) {
                np = &tbl->phash_buckets[h];
                while ((n = *np) != NULL) {
+                       if (skip_perm && n->permanent)
+                               goto skip;
                        if (!dev || n->dev == dev) {
                                *np = n->next;
                                n->next = freelist;
                                freelist = n;
                                continue;
                        }
+skip:
                        np = &n->next;
                }
        }
@@ -2023,6 +2028,7 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,
                pn = pneigh_lookup(tbl, net, dst, dev, 1);
                if (pn) {
                        pn->flags = ndm_flags;
+                       pn->permanent = !!(ndm->ndm_state & NUD_PERMANENT);
                        if (protocol)
                                pn->protocol = protocol;
                        err = 0;