netdev - [PATCH v1 net-next 11/14] neighbour: Remove __pneigh

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Message-ID: <20250711191007.3591938-12-kuniyu@google.com>
Date: Fri, 11 Jul 2025 19:06:16 +0000
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, David Ahern <dsahern@...nel.org>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: [PATCH v1 net-next 11/14] neighbour: Remove __pneigh_lookup().

__pneigh_lookup() is the lockless version of pneigh_lookup(),
but its only caller pndisc_is_router() holds the table lock and
reads pneigh_netry.flags.

This is because accessing pneigh_entry after pneigh_lookup() was
illegal unless the caller holds RTNL or the table lock.

Now, pneigh_entry is guaranteed to be alive during the RCU critical
section.

Let's call pneigh_lookup() and use READ_ONCE() for n->flags in
pndisc_is_router() and remove __pneigh_lookup().

Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
---
 include/net/neighbour.h |  2 --
 net/core/neighbour.c    | 11 -----------
 net/ipv6/ndisc.c        |  6 ++----
 3 files changed, 2 insertions(+), 17 deletions(-)

diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index a877e56210b22..1670e2a388556 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -381,8 +381,6 @@ void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p,
 		    struct sk_buff *skb);
 struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl, struct net *net,
 				   const void *key, struct net_device *dev);
-struct pneigh_entry *__pneigh_lookup(struct neigh_table *tbl, struct net *net,
-				     const void *key, struct net_device *dev);
 struct pneigh_entry *pneigh_create(struct neigh_table *tbl, struct net *net,
 				   const void *key, struct net_device *dev);
 int pneigh_delete(struct neigh_table *tbl, struct net *net, const void *key,
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index e762e88328255..c1e5fda2cf628 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -736,17 +736,6 @@ static struct pneigh_entry *__pneigh_lookup_1(struct pneigh_entry *n,
 	return NULL;
 }
 
-struct pneigh_entry *__pneigh_lookup(struct neigh_table *tbl,
-		struct net *net, const void *pkey, struct net_device *dev)
-{
-	unsigned int key_len = tbl->key_len;
-	u32 hash_val = pneigh_hash(pkey, key_len);
-
-	return __pneigh_lookup_1(tbl->phash_buckets[hash_val],
-				 net, pkey, key_len, dev);
-}
-EXPORT_SYMBOL_GPL(__pneigh_lookup);
-
 struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl,
 				   struct net *net, const void *pkey,
 				   struct net_device *dev)
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index a3ac26c1df6d8..7d5abb3158ec9 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -768,11 +768,9 @@ static int pndisc_is_router(const void *pkey,
 	struct pneigh_entry *n;
 	int ret = -1;
 
-	read_lock_bh(&nd_tbl.lock);
-	n = __pneigh_lookup(&nd_tbl, dev_net(dev), pkey, dev);
+	n = pneigh_lookup(&nd_tbl, dev_net(dev), pkey, dev);
 	if (n)
-		ret = !!(n->flags & NTF_ROUTER);
-	read_unlock_bh(&nd_tbl.lock);
+		ret = !!(READ_ONCE(n->flags) & NTF_ROUTER);
 
 	return ret;
 }
-- 
2.50.0.727.gbf7dc18ff4-goog