• Wei Wang's avatar
    net/tcp-fastopen: Add new API support · 19f6d3f3
    Wei Wang authored
    This patch adds a new socket option, TCP_FASTOPEN_CONNECT, as an
    alternative way to perform Fast Open on the active side (client). Prior
    to this patch, a client needs to replace the connect() call with
    sendto(MSG_FASTOPEN). This can be cumbersome for applications who want
    to use Fast Open: these socket operations are often done in lower layer
    libraries used by many other applications. Changing these libraries
    and/or the socket call sequences are not trivial. A more convenient
    approach is to perform Fast Open by simply enabling a socket option when
    the socket is created w/o changing other socket calls sequence:
      s = socket()
        create a new socket
      setsockopt(s, IPPROTO_TCP, TCP_FASTOPEN_CONNECT …);
        newly introduced sockopt
        If set, new functionality described below will be used.
        Return ENOTSUPP if TFO is not supported or not enabled in the
        kernel.
    
      connect()
        With cookie present, return 0 immediately.
        With no cookie, initiate 3WHS with TFO cookie-request option and
        return -1 with errno = EINPROGRESS.
    
      write()/sendmsg()
        With cookie present, send out SYN with data and return the number of
        bytes buffered.
        With no cookie, and 3WHS not yet completed, return -1 with errno =
        EINPROGRESS.
        No MSG_FASTOPEN flag is needed.
    
      read()
        Return -1 with errno = EWOULDBLOCK/EAGAIN if connect() is called but
        write() is not called yet.
        Return -1 with errno = EWOULDBLOCK/EAGAIN if connection is
        established but no msg is received yet.
        Return number of bytes read if socket is established and there is
        msg received.
    
    The new API simplifies life for applications that always perform a write()
    immediately after a successful connect(). Such applications can now take
    advantage of Fast Open by merely making one new setsockopt() call at the time
    of creating the socket. Nothing else about the application's socket call
    sequence needs to change.
    Signed-off-by: default avatarWei Wang <weiwan@google.com>
    Acked-by: default avatarEric Dumazet <edumazet@google.com>
    Acked-by: default avatarYuchung Cheng <ycheng@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    19f6d3f3
tcp.c 88.1 KB