netdev - [PATCH net-next 1/6] tcp/dccp: add tw->tw

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Message-Id: <20220124202457.3450198-2-eric.dumazet@gmail.com>
Date:   Mon, 24 Jan 2022 12:24:52 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 1/6] tcp/dccp: add tw->tw_bslot

From: Eric Dumazet <edumazet@...gle.com>

We want to allow inet_twsk_kill() working even if netns
has been dismantled/freed, to get rid of inet_twsk_purge().

This patch adds tw->tw_bslot to cache the bind bucket slot
so that inet_twsk_kill() no longer needs to dereference twsk_net(tw)

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/inet_timewait_sock.h |  1 +
 net/ipv4/inet_timewait_sock.c    | 11 +++++++----
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h
index dfd919b3119e8efcbc436a67e3e6fbd02091db10..c221fe2b77dd24d8e0d13db9819cdf3ac13fe742 100644
--- a/include/net/inet_timewait_sock.h
+++ b/include/net/inet_timewait_sock.h
@@ -72,6 +72,7 @@ struct inet_timewait_sock {
 				tw_tos		: 8;
 	u32			tw_txhash;
 	u32			tw_priority;
+	u32			tw_bslot; /* bind bucket slot */
 	struct timer_list	tw_timer;
 	struct inet_bind_bucket	*tw_tb;
 };
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 437afe392e667c7c54509920d1e624f759f9215b..6e8f4a6cd222e89b1c7f9fdd73b10d336ff026a1 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -52,8 +52,7 @@ static void inet_twsk_kill(struct inet_timewait_sock *tw)
 	spin_unlock(lock);
 
 	/* Disassociate with bind bucket. */
-	bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
-			hashinfo->bhash_size)];
+	bhead = &hashinfo->bhash[tw->tw_bslot];
 
 	spin_lock(&bhead->lock);
 	inet_twsk_bind_unhash(tw, hashinfo);
@@ -110,8 +109,12 @@ void inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
 	   Note, that any socket with inet->num != 0 MUST be bound in
 	   binding cache, even if it is closed.
 	 */
-	bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
-			hashinfo->bhash_size)];
+	/* Cache inet_bhashfn(), because 'struct net' might be no longer
+	 * available later in inet_twsk_kill().
+	 */
+	tw->tw_bslot = inet_bhashfn(twsk_net(tw), inet->inet_num,
+				    hashinfo->bhash_size);
+	bhead = &hashinfo->bhash[tw->tw_bslot];
 	spin_lock(&bhead->lock);
 	tw->tw_tb = icsk->icsk_bind_hash;
 	WARN_ON(!icsk->icsk_bind_hash);
-- 
2.35.0.rc0.227.g00780c9af4-goog