[RFC PATCH mptcp-next v12 1/7] mptcp: introduce MSG_FASTOPEN flag.

[Dmytro Shytyi <dmytro@shytyi.net>]

In the following patches we will analyse the MSG_FASTOPEN flag
in the mptcp_sendmsg() and invoke the MPTFO.

Signed-of-by: Benjamin Hesmans <benjamin.hesmans@tessares.net>
Signed-off-by: Dmytro Shytyi <dmytro@shytyi.net>
---
 include/net/mptcp.h  |  9 +++++++++
 include/net/tcp.h    |  3 +++
 net/ipv4/tcp.c       | 20 ++++++++++++++++----
 net/mptcp/protocol.c | 19 +++++++++++--------
 4 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index c25939b2af68..ccf2b42837a1 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -150,6 +150,8 @@ void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp,
 			 struct mptcp_out_options *opts);
 
 void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info);
+int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr, int addr_len, int flags);
+struct sock *mptcp_subflow_conn_sock(struct sock *sk);
 
 /* move the skb extension owership, with the assumption that 'to' is
  * newly allocated
@@ -286,6 +288,13 @@ static inline bool mptcp_skb_can_collapse(const struct sk_buff *to,
 
 static inline void mptcp_space(const struct sock *ssk, int *s, int *fs) { }
 static inline void mptcp_seq_show(struct seq_file *seq) { }
+static inline int mptcp_stream_connect(struct socket *sock,
+				       struct sockaddr *uaddr,
+				       int addr_len,
+				       int flags)
+{
+
+}
 
 static inline int mptcp_subflow_init_cookie_req(struct request_sock *req,
 						const struct sock *sk_listener,
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4f71cc15ff8e..e53d26d74dec 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1757,6 +1757,9 @@ struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
 			      struct request_sock *req,
 			      struct tcp_fastopen_cookie *foc,
 			      const struct dst_entry *dst);
+int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg,
+			 int *copied, size_t size,
+			 struct ubuf_info *uarg);
 void tcp_fastopen_init_key_once(struct net *net);
 bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
 			     struct tcp_fastopen_cookie *cookie);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 5237a3f08c94..daa611671d9a 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1162,8 +1162,9 @@ void tcp_free_fastopen_req(struct tcp_sock *tp)
 	}
 }
 
-int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *copied,
-			 size_t size, struct ubuf_info *uarg)
+int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg,
+			 int *copied, size_t size,
+			 struct ubuf_info *uarg)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct inet_sock *inet = inet_sk(sk);
@@ -1196,8 +1197,19 @@ int tcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg, int *copied,
 		}
 	}
 	flags = (msg->msg_flags & MSG_DONTWAIT) ? O_NONBLOCK : 0;
-	err = __inet_stream_connect(sk->sk_socket, uaddr,
-				    msg->msg_namelen, flags, 1);
+	if (!sk_is_mptcp(sk)) {
+		err = __inet_stream_connect(sk->sk_socket, uaddr,
+					    msg->msg_namelen, flags, 1);
+	} else {
+		struct sock *parent = mptcp_subflow_conn_sock(sk);
+
+		release_sock(sk);
+		release_sock(parent);
+		err = mptcp_stream_connect(sk->sk_socket, uaddr,
+					   msg->msg_namelen, msg->msg_flags);
+		lock_sock(parent);
+		lock_sock(sk);
+	}
 	/* fastopen_req could already be freed in __inet_stream_connect
 	 * if the connection times out or gets rst
 	 */
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 8feb684408f7..0db50712bad7 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -58,6 +58,12 @@ static void __mptcp_check_send_data_fin(struct sock *sk);
 DEFINE_PER_CPU(struct mptcp_delegated_action, mptcp_delegated_actions);
 static struct net_device mptcp_napi_dev;
 
+struct sock *
+mptcp_subflow_conn_sock(struct sock *sk)
+{
+	return ((mptcp_subflow_ctx(sk))->conn);
+}
+
 /* If msk has an initial subflow socket, and the MP_CAPABLE handshake has not
  * completed yet or has failed, return the subflow socket.
  * Otherwise return NULL.
@@ -1673,17 +1679,14 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	int ret = 0;
 	long timeo;
 
-	/* we don't support FASTOPEN yet */
-	if (msg->msg_flags & MSG_FASTOPEN)
-		return -EOPNOTSUPP;
-
 	/* silently ignore everything else */
-	msg->msg_flags &= MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL;
+	msg->msg_flags &= MSG_MORE | MSG_DONTWAIT | MSG_NOSIGNAL | MSG_FASTOPEN;
 
 	lock_sock(sk);
 
 	ssock = __mptcp_nmpc_socket(msk);
-	if (unlikely(ssock && inet_sk(ssock->sk)->defer_connect)) {
+	if (unlikely(ssock && (inet_sk(ssock->sk)->defer_connect ||
+			       msg->msg_flags & MSG_FASTOPEN))) {
 		struct sock *ssk = ssock->sk;
 		int copied_syn = 0;
 
@@ -3568,8 +3571,8 @@ static void mptcp_subflow_early_fallback(struct mptcp_sock *msk,
 	__mptcp_do_fallback(msk);
 }
 
-static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
-				int addr_len, int flags)
+int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
+			 int addr_len, int flags)
 {
 	struct mptcp_sock *msk = mptcp_sk(sock->sk);
 	struct mptcp_subflow_context *subflow;
-- 
2.34.1