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Commit cebc5cba authored by Yuchung Cheng's avatar Yuchung Cheng Committed by David S. Miller
Browse files

net-tcp: retire TFO_SERVER_WO_SOCKOPT2 config 



TFO_SERVER_WO_SOCKOPT2 was intended for debugging purposes during
Fast Open development. Remove this config option and also
update/clean-up the documentation of the Fast Open sysctl.

Reported-by: default avatarPiotr Jurkiewicz <piotr.jerzy.jurkiewicz@gmail.com>
Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1345b1ac

Documentation/networking/ip-sysctl.txt

+23 −22
Original line number Diff line number Diff line
@@ -575,32 +575,33 @@ tcp_syncookies - BOOLEAN 
	unconditionally generation of syncookies.



tcp_fastopen - INTEGER

	Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data

	in the opening SYN packet. To use this feature, the client application

	must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than

	connect() to perform a TCP handshake automatically.

	Enable TCP Fast Open (RFC7413) to send and accept data in the opening

	SYN packet.



	The values (bitmap) are

	1: Enables sending data in the opening SYN on the client w/ MSG_FASTOPEN.

	2: Enables TCP Fast Open on the server side, i.e., allowing data in

	   a SYN packet to be accepted and passed to the application before

	   3-way hand shake finishes.

	4: Send data in the opening SYN regardless of cookie availability and

	   without a cookie option.

	0x100: Accept SYN data w/o validating the cookie.

	0x200: Accept data-in-SYN w/o any cookie option present.

	0x400/0x800: Enable Fast Open on all listeners regardless of the

	   TCP_FASTOPEN socket option. The two different flags designate two

	   different ways of setting max_qlen without the TCP_FASTOPEN socket

	   option.

	The client support is enabled by flag 0x1 (on by default). The client

	then must use sendmsg() or sendto() with the MSG_FASTOPEN flag,

	rather than connect() to send data in SYN.



	Default: 1

	The server support is enabled by flag 0x2 (off by default). Then

	either enable for all listeners with another flag (0x400) or

	enable individual listeners via TCP_FASTOPEN socket option with

	the option value being the length of the syn-data backlog.



	Note that the client & server side Fast Open flags (1 and 2

	respectively) must be also enabled before the rest of flags can take

	effect.

	The values (bitmap) are

	  0x1: (client) enables sending data in the opening SYN on the client.

	  0x2: (server) enables the server support, i.e., allowing data in

			a SYN packet to be accepted and passed to the

			application before 3-way handshake finishes.

	  0x4: (client) send data in the opening SYN regardless of cookie

			availability and without a cookie option.

	0x200: (server) accept data-in-SYN w/o any cookie option present.

	0x400: (server) enable all listeners to support Fast Open by

			default without explicit TCP_FASTOPEN socket option.



	Default: 0x1



	See include/net/tcp.h and the code for more details.

	Note that that additional client or server features are only

	effective if the basic support (0x1 and 0x2) are enabled respectively.



tcp_syn_retries - INTEGER

	Number of times initial SYNs for an active TCP connection attempt

include/net/tcp.h

+1 −2
Original line number Diff line number Diff line
@@ -227,10 +227,9 @@ void tcp_time_wait(struct sock *sk, int state, int timeo); 
#define	TFO_SERVER_COOKIE_NOT_REQD	0x200



/* Force enable TFO on all listeners, i.e., not requiring the

 * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.

 * TCP_FASTOPEN socket option.

 */

#define	TFO_SERVER_WO_SOCKOPT1	0x400

#define	TFO_SERVER_WO_SOCKOPT2	0x800



extern struct inet_timewait_death_row tcp_death_row;

net/ipv4/af_inet.c

+8 −13
Original line number Diff line number Diff line
@@ -211,24 +211,19 @@ int inet_listen(struct socket *sock, int backlog) 
	 * we can only allow the backlog to be adjusted.

	 */

	if (old_state != TCP_LISTEN) {

		/* Check special setups for testing purpose to enable TFO w/o

		 * requiring TCP_FASTOPEN sockopt.

		/* Enable TFO w/o requiring TCP_FASTOPEN socket option.

		 * Note that only TCP sockets (SOCK_STREAM) will reach here.

		 * Also fastopenq may already been allocated because this

		 * socket was in TCP_LISTEN state previously but was

		 * shutdown() (rather than close()).

		 * Also fastopen backlog may already been set via the option

		 * because the socket was in TCP_LISTEN state previously but

		 * was shutdown() rather than close().

		 */

		if ((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) != 0 &&

		if ((sysctl_tcp_fastopen & TFO_SERVER_WO_SOCKOPT1) &&

		    (sysctl_tcp_fastopen & TFO_SERVER_ENABLE) &&

		    !inet_csk(sk)->icsk_accept_queue.fastopenq.max_qlen) {

			if ((sysctl_tcp_fastopen & TFO_SERVER_WO_SOCKOPT1) != 0)

			fastopen_queue_tune(sk, backlog);

			else if ((sysctl_tcp_fastopen &

				  TFO_SERVER_WO_SOCKOPT2) != 0)

				fastopen_queue_tune(sk,

				    ((uint)sysctl_tcp_fastopen) >> 16);



			tcp_fastopen_init_key_once(true);

		}



		err = inet_csk_listen_start(sk, backlog);

		if (err)

			goto out;