On Tue, Jan 31, 2017 at 5:38 PM, Wei Wang <weiwan@xxxxxxxxxx> wrote: > From: Wei Wang <weiwan@xxxxxxxxxx> > > TCP_FASTOPEN socket option was added by: > commit 8336886f786fdacbc19b719c1f7ea91eb70706d4 > TCP_FASTOPEN_CONNECT socket option was added by the following patch > series: > commit 065263f40f0972d5f1cd294bb0242bd5aa5f06b2 > commit 25776aa943401662617437841b3d3ea4693ee98a > commit 19f6d3f3c8422d65b5e3d2162e30ef07c6e21ea2 > commit 3979ad7e82dfe3fb94a51c3915e64ec64afa45c3 > Add detailed description for these 2 options > > Signed-off-by: Wei Wang <weiwan@xxxxxxxxxx> > --- Acked-by: Yuchung Cheng <ycheng@xxxxxxxxxx> Thanks Wei! this is overdue :-) > man7/tcp.7 | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 90 insertions(+) > > diff --git a/man7/tcp.7 b/man7/tcp.7 > index 529246145..c03aa60db 100644 > --- a/man7/tcp.7 > +++ b/man7/tcp.7 > @@ -1149,6 +1149,96 @@ Bound the size of the advertised window to this value. > The kernel imposes a minimum size of SOCK_MIN_RCVBUF/2. > This option should not be used in code intended to be > portable. > +.TP > +.BR TCP_FASTOPEN " (since Linux 3.6)" > +This option enables Fast Open on the listener socket. The option value > +specifies the PendingFastOpenRequests threshold, i.e. the maximum length > +of pending SYNs with data payload. Once enabled, the TCP implementation > +will respond with TCP Fast Open cookies per request. > +.TP > +.BR TCP_FASTOPEN_CONNECT " (since Linux 4.11)" > +This option enables an alternative way to perform Fast Open on the active > +side (client). > +When this option is enabled, > +.BR connect (2) > +would behave differently depending if a Fast Open cookie is available for > +the destination. > + > +If a cookie is not available (i.e. first contact to the destination), > +.BR connect (2) > +behaves as usual by sending a SYN immediately, except the SYN would include > +an empty Fast Open cookie option to solicit a cookie. > + > +If a cookie is available, > +.BR connect (2) > +would return 0 immediately but the SYN transmission is defered. A subsequent > +.BR write (2) > +or > +.BR sendmsg (2) > +would trigger a SYN with data plus cookie in the Fast Open option. In other > +words, the actual connect operation is deferred until data is supplied. > + > +While this option is designed for convenience, enabling it does change the > +behaviors and might return new errnos of socket calls: > + s = socket() > + Create a new socket > + setsockopt(s, IPPROTO_TCP, TCP_FASTOPEN_CONNECT, ...) > + Set this option > + connect() > + With cookie present, return 0 immediately. > + With no cookie, initiate 3WHS with Fast Open option empty and return > +.B EINPROGRESS > + write()/sendmsg() > + With cookie present and > +.BR connect (2) > +called ahead, send out SYN with data plus cookie in the Fast Open option > +and return the number of bytes buffered. > + With no cookie and 3 WHS not yet completed, return > +.B EINPROGRESS. > + No > +.B MSG_FASTOPEN > +flag is needed. > + > + read() > + Return > +.B EWOULDBLOCK > +/ > +.B EAGAIN > +if 3WHS is not yet completed. > + Return > +.B EWOULDBLOCK > +/ > +.B EAGAIN > +if connection is established but no message has been received. > + Return number of bytes read if connection is established and message > + has been received. > + > +.B Note: > + With cookie present, > +.BR write (2) > +/ > +.BR sendmsg (2) > +must be called right after > +.BR connect (2) > +in order to send out SYN+data to complete 3WHS and establish connection. > + Calling > +.BR read (2) > +right after > +.BR connect (2) > +without > +.BR write (2) > +will cause the blocking socket to be blocked forever. > + > +Here is the typical call flow with this new option: > + s = socket(); > + setsockopt(s, IPPROTO_TCP, TCP_FASTOPEN_CONNECT, 1, ...); > + connect(s); > + write(s); // write() should always follow connect() in order to > + // trigger SYN to go out > + read(s)/write(s); > + ... > + close(s); > + > .SS Sockets API > TCP provides limited support for out-of-band data, > in the form of (a single byte of) urgent data. > -- > 2.11.0.483.g087da7b7c-goog > -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
