include/linux/tcp.h

/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Definitions for the TCP protocol.
 *
 * Version:	@(#)tcp.h	1.0.2	04/28/93
 *
 * Author:	Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 */
#ifndef _LINUX_TCP_H
#define _LINUX_TCP_H

#include <linux/types.h>
#include <asm/byteorder.h>
#include <linux/socket.h>

struct tcphdr {
	__be16	source;
	__be16	dest;
	__be32	seq;
	__be32	ack_seq;
#if defined(__LITTLE_ENDIAN_BITFIELD)
	__u16	res1:4,
		doff:4,
		fin:1,
		syn:1,
		rst:1,
		psh:1,
		ack:1,
		urg:1,
		ece:1,
		cwr:1;
#elif defined(__BIG_ENDIAN_BITFIELD)
	__u16	doff:4,
		res1:4,
		cwr:1,
		ece:1,
		urg:1,
		ack:1,
		psh:1,
		rst:1,
		syn:1,
		fin:1;
#else
#error	"Adjust your <asm/byteorder.h> defines"
#endif	
	__be16	window;
	__sum16	check;
	__be16	urg_ptr;
};

/*
 *	The union cast uses a gcc extension to avoid aliasing problems
 *  (union is compatible to any of its members)
 *  This means this part of the code is -fstrict-aliasing safe now.
 */
union tcp_word_hdr { 
	struct tcphdr hdr;
	__be32 		  words[5];
}; 

#define tcp_flag_word(tp) ( ((union tcp_word_hdr *)(tp))->words [3]) 

enum { 
	TCP_FLAG_CWR = __constant_cpu_to_be32(0x00800000),
	TCP_FLAG_ECE = __constant_cpu_to_be32(0x00400000),
	TCP_FLAG_URG = __constant_cpu_to_be32(0x00200000),
	TCP_FLAG_ACK = __constant_cpu_to_be32(0x00100000),
	TCP_FLAG_PSH = __constant_cpu_to_be32(0x00080000),
	TCP_FLAG_RST = __constant_cpu_to_be32(0x00040000),
	TCP_FLAG_SYN = __constant_cpu_to_be32(0x00020000),
	TCP_FLAG_FIN = __constant_cpu_to_be32(0x00010000),
	TCP_RESERVED_BITS = __constant_cpu_to_be32(0x0F000000),
	TCP_DATA_OFFSET = __constant_cpu_to_be32(0xF0000000)
}; 

/*
 * TCP general constants
 */
#define TCP_MSS_DEFAULT		 536U	/* IPv4 (RFC1122, RFC2581) */
#define TCP_MSS_DESIRED		1220U	/* IPv6 (tunneled), EDNS0 (RFC3226) */

/* TCP socket options */
#define TCP_NODELAY		1	/* Turn off Nagle's algorithm. */
#define TCP_MAXSEG		2	/* Limit MSS */
#define TCP_CORK		3	/* Never send partially complete segments */
#define TCP_KEEPIDLE		4	/* Start keeplives after this period */
#define TCP_KEEPINTVL		5	/* Interval between keepalives */
#define TCP_KEEPCNT		6	/* Number of keepalives before death */
#define TCP_SYNCNT		7	/* Number of SYN retransmits */
#define TCP_LINGER2		8	/* Life time of orphaned FIN-WAIT-2 state */
#define TCP_DEFER_ACCEPT	9	/* Wake up listener only when data arrive */
#define TCP_WINDOW_CLAMP	10	/* Bound advertised window */
#define TCP_INFO		11	/* Information about this connection. */
#define TCP_QUICKACK		12	/* Block/reenable quick acks */
#define TCP_CONGESTION		13	/* Congestion control algorithm */
#define TCP_MD5SIG		14	/* TCP MD5 Signature (RFC2385) */
#define TCP_THIN_LINEAR_TIMEOUTS 16      /* Use linear timeouts for thin streams*/
#define TCP_THIN_DUPACK         17      /* Fast retrans. after 1 dupack */
#define TCP_USER_TIMEOUT	18	/* How long for loss retry before timeout */
#define TCP_REPAIR		19	/* TCP sock is under repair right now */
#define TCP_REPAIR_QUEUE	20
#define TCP_QUEUE_SEQ		21
#define TCP_REPAIR_OPTIONS	22
#define TCP_FASTOPEN		23	/* Enable FastOpen on listeners */
#define TCP_TIMESTAMP		24
#define TCP_NOTSENT_LOWAT	25	/* limit number of unsent bytes in write queue */

struct tcp_repair_opt {
	__u32	opt_code;
	__u32	opt_val;
};

enum {
	TCP_NO_QUEUE,
	TCP_RECV_QUEUE,
	TCP_SEND_QUEUE,
	TCP_QUEUES_NR,
};

/* for TCP_INFO socket option */
#define TCPI_OPT_TIMESTAMPS	1
#define TCPI_OPT_SACK		2
#define TCPI_OPT_WSCALE		4
#define TCPI_OPT_ECN		8 /* ECN was negociated at TCP session init */
#define TCPI_OPT_ECN_SEEN	16 /* we received at least one packet with ECT */
#define TCPI_OPT_SYN_DATA	32 /* SYN-ACK acked data in SYN sent or rcvd */

enum tcp_ca_state {
	TCP_CA_Open = 0,
#define TCPF_CA_Open	(1<<TCP_CA_Open)
	TCP_CA_Disorder = 1,
#define TCPF_CA_Disorder (1<<TCP_CA_Disorder)
	TCP_CA_CWR = 2,
#define TCPF_CA_CWR	(1<<TCP_CA_CWR)
	TCP_CA_Recovery = 3,
#define TCPF_CA_Recovery (1<<TCP_CA_Recovery)
	TCP_CA_Loss = 4
#define TCPF_CA_Loss	(1<<TCP_CA_Loss)
};

struct tcp_info {
	__u8	tcpi_state;
	__u8	tcpi_ca_state;
	__u8	tcpi_retransmits;
	__u8	tcpi_probes;
	__u8	tcpi_backoff;
	__u8	tcpi_options;
	__u8	tcpi_snd_wscale : 4, tcpi_rcv_wscale : 4;

	__u32	tcpi_rto;
	__u32	tcpi_ato;
	__u32	tcpi_snd_mss;
	__u32	tcpi_rcv_mss;

	__u32	tcpi_unacked;
	__u32	tcpi_sacked;
	__u32	tcpi_lost;
	__u32	tcpi_retrans;
	__u32	tcpi_fackets;

	/* Times. */
	__u32	tcpi_last_data_sent;
	__u32	tcpi_last_ack_sent;     /* Not remembered, sorry. */
	__u32	tcpi_last_data_recv;
	__u32	tcpi_last_ack_recv;

	/* Metrics. */
	__u32	tcpi_pmtu;
	__u32	tcpi_rcv_ssthresh;
	__u32	tcpi_rtt;
	__u32	tcpi_rttvar;
	__u32	tcpi_snd_ssthresh;
	__u32	tcpi_snd_cwnd;
	__u32	tcpi_advmss;
	__u32	tcpi_reordering;

	__u32	tcpi_rcv_rtt;
	__u32	tcpi_rcv_space;

	__u32	tcpi_total_retrans;

	__u64	tcpi_pacing_rate;
	__u64	tcpi_max_pacing_rate;
};

/* for TCP_MD5SIG socket option */
#define TCP_MD5SIG_MAXKEYLEN	80

struct tcp_md5sig {
	struct __kernel_sockaddr_storage tcpm_addr;	/* address associated */
	__u16	__tcpm_pad1;				/* zero */
	__u16	tcpm_keylen;				/* key length */
	__u32	__tcpm_pad2;				/* zero */
	__u8	tcpm_key[TCP_MD5SIG_MAXKEYLEN];		/* key (binary) */
};

#endif /* _LINUX_TCP_H */