text: /*
   * 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 = __cpu_to_be32(0x00800000),
  	TCP_FLAG_ECE = __cpu_to_be32(0x00400000),
  	TCP_FLAG_URG = __cpu_to_be32(0x00200000),
  	TCP_FLAG_ACK = __cpu_to_be32(0x00100000),
  	TCP_FLAG_PSH = __cpu_to_be32(0x00080000),
  	TCP_FLAG_RST = __cpu_to_be32(0x00040000),
  	TCP_FLAG_SYN = __cpu_to_be32(0x00020000),
  	TCP_FLAG_FIN = __cpu_to_be32(0x00010000),
  	TCP_RESERVED_BITS = __cpu_to_be32(0x0F000000),
  	TCP_DATA_OFFSET = __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_COOKIE_TRANSACTIONS	15	/* TCP Cookie Transactions */
  #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 */
  
  /* 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
  
  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;
  };
  
  /* 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) */
  };
  
  /* for TCP_COOKIE_TRANSACTIONS (TCPCT) socket option */
  #define TCP_COOKIE_MIN		 8		/*  64-bits */
  #define TCP_COOKIE_MAX		16		/* 128-bits */
  #define TCP_COOKIE_PAIR_SIZE	(2*TCP_COOKIE_MAX)
  
  /* Flags for both getsockopt and setsockopt */
  #define TCP_COOKIE_IN_ALWAYS	(1 << 0)	/* Discard SYN without cookie */
  #define TCP_COOKIE_OUT_NEVER	(1 << 1)	/* Prohibit outgoing cookies,
  						 * supercedes everything. */
  
  /* Flags for getsockopt */
  #define TCP_S_DATA_IN		(1 << 2)	/* Was data received? */
  #define TCP_S_DATA_OUT		(1 << 3)	/* Was data sent? */
  
  /* TCP_COOKIE_TRANSACTIONS data */
  struct tcp_cookie_transactions {
  	__u16	tcpct_flags;			/* see above */
  	__u8	__tcpct_pad1;			/* zero */
  	__u8	tcpct_cookie_desired;		/* bytes */
  	__u16	tcpct_s_data_desired;		/* bytes of variable data */
  	__u16	tcpct_used;			/* bytes in value */
  	__u8	tcpct_value[TCP_MSS_DEFAULT];
  };
  
  
  #endif	/* _LINUX_TCP_H */
  