FAILED: patch "[PATCH] mptcp: remove MPTCP 'ifdef' in TCP SYN cookies" failed to apply to 5.10-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

Possible dependencies:

3fff88186f04 ("mptcp: remove MPTCP 'ifdef' in TCP SYN cookies")
4cf86ae84c71 ("mptcp: strict local address ID selection")
51fa7f8ebf0e ("mptcp: mark ops structures as ro_after_init")
ff5a0b421cb2 ("mptcp: faster active backup recovery")
6da14d74e2bd ("mptcp: cleanup sysctl data and helpers")
1e1d9d6f119c ("mptcp: handle pending data on closed subflow")
71b7dec27f34 ("mptcp: less aggressive retransmission strategy")
33d41c9cd74c ("mptcp: more accurate timeout")
d2f77960e5b0 ("mptcp: add sysctl allow_join_initial_addr_port")
8ce568ed06ce ("mptcp: drop tx skb cache")
adc2e56ebe63 ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3fff88186f047627bb128d65155f42517f8e448f Mon Sep 17 00:00:00 2001
From: Matthieu Baerts <matthieu.baerts@tessares.net>
Date: Fri, 9 Dec 2022 16:28:08 -0800
Subject: [PATCH] mptcp: remove MPTCP 'ifdef' in TCP SYN cookies

To ease the maintenance, it is often recommended to avoid having #ifdef
preprocessor conditions.

Here the section related to CONFIG_MPTCP was quite short but the next
commit needs to add more code around. It is then cleaner to move
specific MPTCP code to functions located in net/mptcp directory.

Now that mptcp_subflow_request_sock_ops structure can be static, it can
also be marked as "read only after init".

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 412479ebf5ad..3c5c68618fcc 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -97,8 +97,6 @@ struct mptcp_out_options {
 };
 
 #ifdef CONFIG_MPTCP
-extern struct request_sock_ops mptcp_subflow_request_sock_ops;
-
 void mptcp_init(void);
 
 static inline bool sk_is_mptcp(const struct sock *sk)
@@ -188,6 +186,9 @@ void mptcp_seq_show(struct seq_file *seq);
 int mptcp_subflow_init_cookie_req(struct request_sock *req,
 				  const struct sock *sk_listener,
 				  struct sk_buff *skb);
+struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
+					       struct sock *sk_listener,
+					       bool attach_listener);
 
 __be32 mptcp_get_reset_option(const struct sk_buff *skb);
 
@@ -274,6 +275,13 @@ static inline int mptcp_subflow_init_cookie_req(struct request_sock *req,
 	return 0; /* TCP fallback */
 }
 
+static inline struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
+							     struct sock *sk_listener,
+							     bool attach_listener)
+{
+	return NULL;
+}
+
 static inline __be32 mptcp_reset_option(const struct sk_buff *skb)  { return htonl(0u); }
 #endif /* CONFIG_MPTCP */
 
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 942d2dfa1115..26fb97d1d4d9 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -288,12 +288,11 @@ struct request_sock *cookie_tcp_reqsk_alloc(const struct request_sock_ops *ops,
 	struct tcp_request_sock *treq;
 	struct request_sock *req;
 
-#ifdef CONFIG_MPTCP
 	if (sk_is_mptcp(sk))
-		ops = &mptcp_subflow_request_sock_ops;
-#endif
+		req = mptcp_subflow_reqsk_alloc(ops, sk, false);
+	else
+		req = inet_reqsk_alloc(ops, sk, false);
 
-	req = inet_reqsk_alloc(ops, sk, false);
 	if (!req)
 		return NULL;
 
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 2159b5f9988f..3f670f2d5c5c 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -529,7 +529,7 @@ static int subflow_v6_rebuild_header(struct sock *sk)
 }
 #endif
 
-struct request_sock_ops mptcp_subflow_request_sock_ops;
+static struct request_sock_ops mptcp_subflow_request_sock_ops __ro_after_init;
 static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops __ro_after_init;
 
 static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
@@ -582,6 +582,16 @@ static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 }
 #endif
 
+struct request_sock *mptcp_subflow_reqsk_alloc(const struct request_sock_ops *ops,
+					       struct sock *sk_listener,
+					       bool attach_listener)
+{
+	ops = &mptcp_subflow_request_sock_ops;
+
+	return inet_reqsk_alloc(ops, sk_listener, attach_listener);
+}
+EXPORT_SYMBOL(mptcp_subflow_reqsk_alloc);
+
 /* validate hmac received in third ACK */
 static bool subflow_hmac_valid(const struct request_sock *req,
 			       const struct mptcp_options_received *mp_opt)