netdev - [PATCH net-next 1/2] net: introduce and use custom sockopt socket flag

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Date:   Wed, 19 Oct 2022 12:02:00 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>, mptcp@...ts.linux.dev,
        David Ahern <dsahern@...nel.org>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Matthieu Baerts <matthieu.baerts@...sares.net>
Subject: [PATCH net-next 1/2] net: introduce and use custom sockopt socket flag

We will soon introduce custom setsockopt for UDP sockets, too.
Instead of doing even more complex arbitrary checks inside
sock_use_custom_sol_socket(), add a new socket flag and set it
for the relevant socket types (currently only MPTCP).

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 include/linux/net.h  | 1 +
 net/mptcp/protocol.c | 4 ++++
 net/socket.c         | 8 +-------
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/include/linux/net.h b/include/linux/net.h
index 711c3593c3b8..59350fd85823 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -41,6 +41,7 @@ struct net;
 #define SOCK_NOSPACE		2
 #define SOCK_PASSCRED		3
 #define SOCK_PASSSEC		4
+#define SOCK_CUSTOM_SOCKOPT	5
 
 #ifndef ARCH_HAS_SOCKET_TYPES
 /**
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index f599ad44ed24..0448a5c3da3c 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2708,6 +2708,8 @@ static int mptcp_init_sock(struct sock *sk)
 	if (ret)
 		return ret;
 
+	set_bit(SOCK_CUSTOM_SOCKOPT, &sk->sk_socket->flags);
+
 	/* fetch the ca name; do it outside __mptcp_init_sock(), so that clone will
 	 * propagate the correct value
 	 */
@@ -3684,6 +3686,8 @@ static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
 		struct mptcp_subflow_context *subflow;
 		struct sock *newsk = newsock->sk;
 
+		set_bit(SOCK_CUSTOM_SOCKOPT, &newsock->flags);
+
 		lock_sock(newsk);
 
 		/* PM/worker can now acquire the first subflow socket
diff --git a/net/socket.c b/net/socket.c
index 00da9ce3dba0..55c5d536e5f6 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2199,13 +2199,7 @@ SYSCALL_DEFINE4(recv, int, fd, void __user *, ubuf, size_t, size,
 
 static bool sock_use_custom_sol_socket(const struct socket *sock)
 {
-	const struct sock *sk = sock->sk;
-
-	/* Use sock->ops->setsockopt() for MPTCP */
-	return IS_ENABLED(CONFIG_MPTCP) &&
-	       sk->sk_protocol == IPPROTO_MPTCP &&
-	       sk->sk_type == SOCK_STREAM &&
-	       (sk->sk_family == AF_INET || sk->sk_family == AF_INET6);
+	return test_bit(SOCK_CUSTOM_SOCKOPT, &sock->flags);
 }
 
 /*
-- 
2.37.3