netdev - [PATCH net-next 1/3] net: use mptcp setsockopt function for SOL

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Date:   Sun,  5 Jul 2020 01:30:15 +0200
From:   Florian Westphal <fw@...len.de>
To:     <netdev@...r.kernel.org>
Cc:     <mptcp@...ts.01.org>, Florian Westphal <fw@...len.de>
Subject: [PATCH net-next 1/3] net: use mptcp setsockopt function for SOL_SOCKET on mptcp sockets

setsockopt(mptcp_fd, SOL_SOCKET, ...)...  appears to work (returns 0),
but it has no effect -- this is because the MPTCP layer never has a
chance to copy the settings to the subflow socket.

Skip the generic handling for the mptcp case and instead call the
mptcp specific handler instead for SOL_SOCKET too.

Next patch adds more specific handling for SOL_SOCKET to mptcp.

Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/mptcp/protocol.c |  3 +++
 net/socket.c         | 13 ++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index fa137a9c42d1..320f306ea85c 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1609,6 +1609,9 @@ static int mptcp_setsockopt(struct sock *sk, int level, int optname,
 
 	pr_debug("msk=%p", msk);
 
+	if (level == SOL_SOCKET)
+		return sock_setsockopt(sk->sk_socket, level, optname, optval, optlen);
+
 	/* @@ the meaning of setsockopt() when the socket is connected and
 	 * there are multiple subflows is not yet defined. It is up to the
 	 * MPTCP-level socket to configure the subflows until the subflow
diff --git a/net/socket.c b/net/socket.c
index 976426d03f09..d87812a9ed4b 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2080,6 +2080,17 @@ SYSCALL_DEFINE4(recv, int, fd, void __user *, ubuf, size_t, size,
 	return __sys_recvfrom(fd, ubuf, size, flags, NULL, NULL);
 }
 
+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);
+}
+
 /*
  *	Set a socket option. Because we don't know the option lengths we have
  *	to pass the user mode parameter for the protocols to sort out.
@@ -2118,7 +2129,7 @@ static int __sys_setsockopt(int fd, int level, int optname,
 			optval = (char __user __force *)kernel_optval;
 		}
 
-		if (level == SOL_SOCKET)
+		if (level == SOL_SOCKET && !sock_use_custom_sol_socket(sock))
 			err =
 			    sock_setsockopt(sock, level, optname, optval,
 					    optlen);
-- 
2.26.2