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Commit 1a2c6181 authored by Christoph Paasch's avatar Christoph Paasch Committed by David S. Miller
Browse files

tcp: Remove TCPCT 



TCPCT uses option-number 253, reserved for experimental use and should
not be used in production environments.
Further, TCPCT does not fully implement RFC 6013.

As a nice side-effect, removing TCPCT increases TCP's performance for
very short flows:

Doing an apache-benchmark with -c 100 -n 100000, sending HTTP-requests
for files of 1KB size.

before this patch:
	average (among 7 runs) of 20845.5 Requests/Second
after:
	average (among 7 runs) of 21403.6 Requests/Second

Signed-off-by: default avatarChristoph Paasch <christoph.paasch@uclouvain.be>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 94d8f2b1

Documentation/networking/ip-sysctl.txt

+0 −8
Original line number Diff line number Diff line
@@ -175,14 +175,6 @@ tcp_congestion_control - STRING 
	is inherited.

	[see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ]



tcp_cookie_size - INTEGER

	Default size of TCP Cookie Transactions (TCPCT) option, that may be

	overridden on a per socket basis by the TCPCT socket option.

	Values greater than the maximum (16) are interpreted as the maximum.

	Values greater than zero and less than the minimum (8) are interpreted

	as the minimum.  Odd values are interpreted as the next even value.

	Default: 0 (off).



tcp_dsack - BOOLEAN

	Allows TCP to send "duplicate" SACKs.

drivers/infiniband/hw/cxgb4/cm.c

+1 −1
Original line number Diff line number Diff line
@@ -2915,7 +2915,7 @@ static void build_cpl_pass_accept_req(struct sk_buff *skb, int stid , u8 tos) 
	 */

	memset(&tmp_opt, 0, sizeof(tmp_opt));

	tcp_clear_options(&tmp_opt);

	tcp_parse_options(skb, &tmp_opt, NULL, 0, NULL);

	tcp_parse_options(skb, &tmp_opt, 0, NULL);



	req = (struct cpl_pass_accept_req *)__skb_push(skb, sizeof(*req));

	memset(req, 0, sizeof(*req));

include/linux/tcp.h

+0 −10
Original line number Diff line number Diff line
@@ -90,9 +90,6 @@ struct tcp_options_received { 
		sack_ok : 4,	/* SACK seen on SYN packet		*/

		snd_wscale : 4,	/* Window scaling received from sender	*/

		rcv_wscale : 4;	/* Window scaling to send to receiver	*/

	u8	cookie_plus:6,	/* bytes in authenticator/cookie option	*/

		cookie_out_never:1,

		cookie_in_always:1;

	u8	num_sacks;	/* Number of SACK blocks		*/

	u16	user_mss;	/* mss requested by user in ioctl	*/

	u16	mss_clamp;	/* Maximal mss, negotiated at connection setup */
@@ -102,7 +99,6 @@ static inline void tcp_clear_options(struct tcp_options_received *rx_opt) 
{

	rx_opt->tstamp_ok = rx_opt->sack_ok = 0;

	rx_opt->wscale_ok = rx_opt->snd_wscale = 0;

	rx_opt->cookie_plus = 0;

}



/* This is the max number of SACKS that we'll generate and process. It's safe
@@ -320,12 +316,6 @@ struct tcp_sock { 
	struct tcp_md5sig_info	__rcu *md5sig_info;

#endif



	/* When the cookie options are generated and exchanged, then this

	 * object holds a reference to them (cookie_values->kref).  Also

	 * contains related tcp_cookie_transactions fields.

	 */

	struct tcp_cookie_values  *cookie_values;



/* TCP fastopen related information */

	struct tcp_fastopen_request *fastopen_req;

	/* fastopen_rsk points to request_sock that resulted in this big

include/net/request_sock.h

+1 −7
Original line number Diff line number Diff line
@@ -27,19 +27,13 @@ struct sk_buff; 
struct dst_entry;

struct proto;



/* empty to "strongly type" an otherwise void parameter.

 */

struct request_values {

};



struct request_sock_ops {

	int		family;

	int		obj_size;

	struct kmem_cache	*slab;

	char		*slab_name;

	int		(*rtx_syn_ack)(struct sock *sk,

				       struct request_sock *req,

				       struct request_values *rvp);

				       struct request_sock *req);

	void		(*send_ack)(struct sock *sk, struct sk_buff *skb,

				    struct request_sock *req);

	void		(*send_reset)(struct sock *sk,

include/net/tcp.h

+1 −88
Original line number Diff line number Diff line
@@ -179,7 +179,6 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo); 
#define TCPOPT_SACK             5       /* SACK Block */

#define TCPOPT_TIMESTAMP	8	/* Better RTT estimations/PAWS */

#define TCPOPT_MD5SIG		19	/* MD5 Signature (RFC2385) */

#define TCPOPT_COOKIE		253	/* Cookie extension (experimental) */

#define TCPOPT_EXP		254	/* Experimental */

/* Magic number to be after the option value for sharing TCP

 * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
@@ -454,7 +453,7 @@ extern void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req); 
extern int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,

		       size_t len, int nonblock, int flags, int *addr_len);

extern void tcp_parse_options(const struct sk_buff *skb,

			      struct tcp_options_received *opt_rx, const u8 **hvpp,

			      struct tcp_options_received *opt_rx,

			      int estab, struct tcp_fastopen_cookie *foc);

extern const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
@@ -476,7 +475,6 @@ extern int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, 
extern int tcp_connect(struct sock *sk);

extern struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,

					struct request_sock *req,

					struct request_values *rvp,

					struct tcp_fastopen_cookie *foc);

extern int tcp_disconnect(struct sock *sk, int flags);
@@ -1589,91 +1587,6 @@ struct tcp_request_sock_ops { 
#endif

};



/* Using SHA1 for now, define some constants.

 */

#define COOKIE_DIGEST_WORDS (SHA_DIGEST_WORDS)

#define COOKIE_MESSAGE_WORDS (SHA_MESSAGE_BYTES / 4)

#define COOKIE_WORKSPACE_WORDS (COOKIE_DIGEST_WORDS + COOKIE_MESSAGE_WORDS)



extern int tcp_cookie_generator(u32 *bakery);



/**

 *	struct tcp_cookie_values - each socket needs extra space for the

 *	cookies, together with (optional) space for any SYN data.

 *

 *	A tcp_sock contains a pointer to the current value, and this is

 *	cloned to the tcp_timewait_sock.

 *

 * @cookie_pair:	variable data from the option exchange.

 *

 * @cookie_desired:	user specified tcpct_cookie_desired.  Zero

 *			indicates default (sysctl_tcp_cookie_size).

 *			After cookie sent, remembers size of cookie.

 *			Range 0, TCP_COOKIE_MIN to TCP_COOKIE_MAX.

 *

 * @s_data_desired:	user specified tcpct_s_data_desired.  When the

 *			constant payload is specified (@s_data_constant),

 *			holds its length instead.

 *			Range 0 to TCP_MSS_DESIRED.

 *

 * @s_data_payload:	constant data that is to be included in the

 *			payload of SYN or SYNACK segments when the

 *			cookie option is present.

 */

struct tcp_cookie_values {

	struct kref	kref;

	u8		cookie_pair[TCP_COOKIE_PAIR_SIZE];

	u8		cookie_pair_size;

	u8		cookie_desired;

	u16		s_data_desired:11,

			s_data_constant:1,

			s_data_in:1,

			s_data_out:1,

			s_data_unused:2;

	u8		s_data_payload[0];

};



static inline void tcp_cookie_values_release(struct kref *kref)

{

	kfree(container_of(kref, struct tcp_cookie_values, kref));

}



/* The length of constant payload data.  Note that s_data_desired is

 * overloaded, depending on s_data_constant: either the length of constant

 * data (returned here) or the limit on variable data.

 */

static inline int tcp_s_data_size(const struct tcp_sock *tp)

{

	return (tp->cookie_values != NULL && tp->cookie_values->s_data_constant)

		? tp->cookie_values->s_data_desired

		: 0;

}



/**

 *	struct tcp_extend_values - tcp_ipv?.c to tcp_output.c workspace.

 *

 *	As tcp_request_sock has already been extended in other places, the

 *	only remaining method is to pass stack values along as function

 *	parameters.  These parameters are not needed after sending SYNACK.

 *

 * @cookie_bakery:	cryptographic secret and message workspace.

 *

 * @cookie_plus:	bytes in authenticator/cookie option, copied from

 *			struct tcp_options_received (above).

 */

struct tcp_extend_values {

	struct request_values		rv;

	u32				cookie_bakery[COOKIE_WORKSPACE_WORDS];

	u8				cookie_plus:6,

					cookie_out_never:1,

					cookie_in_always:1;

};



static inline struct tcp_extend_values *tcp_xv(struct request_values *rvp)

{

	return (struct tcp_extend_values *)rvp;

}



extern void tcp_v4_init(void);

extern void tcp_init(void);