net-tcp: Fast Open client - sendmsg(MSG_FASTOPEN)

sendmsg() (or sendto()) with MSG_FASTOPEN is a combo of connect(2)
and write(2). The application should replace connect() with it to
send data in the opening SYN packet.

For blocking socket, sendmsg() blocks until all the data are buffered
locally and the handshake is completed like connect() call. It
returns similar errno like connect() if the TCP handshake fails.

For non-blocking socket, it returns the number of bytes queued (and
transmitted in the SYN-data packet) if cookie is available. If cookie
is not available, it transmits a data-less SYN packet with Fast Open
cookie request option and returns -EINPROGRESS like connect().

Using MSG_FASTOPEN on connecting or connected socket will result in
simlar errno like repeating connect() calls. Therefore the application
should only use this flag on new sockets.

The buffer size of sendmsg() is independent of the MSS of the connection.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/include/net/inet_common.h b/include/net/inet_common.h
index 22fac9892b16..234008782c8c 100644
--- a/include/net/inet_common.h
+++ b/include/net/inet_common.h
@@ -14,9 +14,11 @@ struct sockaddr;
 struct socket;
 
 extern int inet_release(struct socket *sock);
-extern int inet_stream_connect(struct socket *sock, struct sockaddr * uaddr,
+extern int inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
                                int addr_len, int flags);
-extern int inet_dgram_connect(struct socket *sock, struct sockaddr * uaddr,
+extern int __inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,
+                                 int addr_len, int flags);
+extern int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr,
                               int addr_len, int flags);
 extern int inet_accept(struct socket *sock, struct socket *newsock, int flags);
 extern int inet_sendmsg(struct kiocb *iocb, struct socket *sock,