include/net/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 module.
 *
 * Version:	@(#)tcp.h	1.0.5	05/23/93
 *
 * Authors:	Ross Biro
 *		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 _TCP_H
#define _TCP_H

#define FASTRETRANS_DEBUG 1

#include <linux/list.h>
#include <linux/tcp.h>
#include <linux/bug.h>
#include <linux/slab.h>
#include <linux/cache.h>
#include <linux/percpu.h>
#include <linux/skbuff.h>
#include <linux/dmaengine.h>
#include <linux/crypto.h>
#include <linux/cryptohash.h>
#include <linux/kref.h>

#include <net/inet_connection_sock.h>
#include <net/inet_timewait_sock.h>
#include <net/inet_hashtables.h>
#include <net/checksum.h>
#include <net/request_sock.h>
#include <net/sock.h>
#include <net/snmp.h>
#include <net/ip.h>
#include <net/tcp_states.h>
#include <net/inet_ecn.h>
#include <net/dst.h>

#include <linux/seq_file.h>
#include <linux/memcontrol.h>

extern struct inet_hashinfo tcp_hashinfo;

extern struct percpu_counter tcp_orphan_count;
extern void tcp_time_wait(struct sock *sk, int state, int timeo);

#define MAX_TCP_HEADER	(128 + MAX_HEADER)
#define MAX_TCP_OPTION_SPACE 40

#define MAX_TCP_WINDOW		32767U

#define TCP_DEFAULT_INIT_RCVWND	10

#define TCP_MIN_MSS		88U

#define TCP_BASE_MSS		512

#define TCP_FASTRETRANS_THRESH 3

#define TCP_MAX_REORDERING	127

#define TCP_MAX_QUICKACKS	16U

#define TCP_URG_VALID	0x0100
#define TCP_URG_NOTYET	0x0200
#define TCP_URG_READ	0x0400

#define TCP_RETR1	3	

#define TCP_RETR2	15	

#define TCP_SYN_RETRIES	 5	

#define TCP_SYNACK_RETRIES 5	

#define TCP_TIMEWAIT_LEN (60*HZ) 
#define TCP_FIN_TIMEOUT	TCP_TIMEWAIT_LEN

#define TCP_DELACK_MAX	((unsigned)(HZ/5))	
#if HZ >= 100
#define TCP_DELACK_MIN	((unsigned)(HZ/25))	
#define TCP_ATO_MIN	((unsigned)(HZ/25))
#else
#define TCP_DELACK_MIN	4U
#define TCP_ATO_MIN	4U
#endif
#define TCP_RTO_MAX	((unsigned)(120*HZ))
#define TCP_RTO_MIN	((unsigned)(HZ/5))
#define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))	
#define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ))	

#define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) 

#define TCP_KEEPALIVE_TIME	(120*60*HZ)	
#define TCP_KEEPALIVE_PROBES	9		
#define TCP_KEEPALIVE_INTVL	(75*HZ)

#define MAX_TCP_KEEPIDLE	32767
#define MAX_TCP_KEEPINTVL	32767
#define MAX_TCP_KEEPCNT		127
#define MAX_TCP_SYNCNT		127

#define TCP_SYNQ_INTERVAL	(HZ/5)	

#define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)
#define TCP_PAWS_MSL	60		
#define TCP_PAWS_WINDOW	1		
 
#define TCPOPT_NOP		1	
#define TCPOPT_EOL		0	
#define TCPOPT_MSS		2	
#define TCPOPT_WINDOW		3	
#define TCPOPT_SACK_PERM        4       
#define TCPOPT_SACK             5       
#define TCPOPT_TIMESTAMP	8	
#define TCPOPT_MD5SIG		19	
#define TCPOPT_COOKIE		253	


#define TCPOLEN_MSS            4
#define TCPOLEN_WINDOW         3
#define TCPOLEN_SACK_PERM      2
#define TCPOLEN_TIMESTAMP      10
#define TCPOLEN_MD5SIG         18
#define TCPOLEN_COOKIE_BASE    2	
#define TCPOLEN_COOKIE_PAIR    3	
#define TCPOLEN_COOKIE_MIN     (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MIN)
#define TCPOLEN_COOKIE_MAX     (TCPOLEN_COOKIE_BASE+TCP_COOKIE_MAX)

#define TCPOLEN_TSTAMP_ALIGNED		12
#define TCPOLEN_WSCALE_ALIGNED		4
#define TCPOLEN_SACKPERM_ALIGNED	4
#define TCPOLEN_SACK_BASE		2
#define TCPOLEN_SACK_BASE_ALIGNED	4
#define TCPOLEN_SACK_PERBLOCK		8
#define TCPOLEN_MD5SIG_ALIGNED		20
#define TCPOLEN_MSS_ALIGNED		4

#define TCP_NAGLE_OFF		1	
#define TCP_NAGLE_CORK		2	
#define TCP_NAGLE_PUSH		4	

#define TCP_THIN_LINEAR_RETRIES 6       

#define TCP_INIT_CWND		10

extern struct inet_timewait_death_row tcp_death_row;

extern int sysctl_tcp_timestamps;
extern int sysctl_tcp_window_scaling;
extern int sysctl_tcp_sack;
extern int sysctl_tcp_fin_timeout;
extern int sysctl_tcp_keepalive_time;
extern int sysctl_tcp_keepalive_probes;
extern int sysctl_tcp_keepalive_intvl;
extern int sysctl_tcp_syn_retries;
extern int sysctl_tcp_synack_retries;
extern int sysctl_tcp_retries1;
extern int sysctl_tcp_retries2;
extern int sysctl_tcp_orphan_retries;
extern int sysctl_tcp_syncookies;
extern int sysctl_tcp_retrans_collapse;
extern int sysctl_tcp_stdurg;
extern int sysctl_tcp_rfc1337;
extern int sysctl_tcp_abort_on_overflow;
extern int sysctl_tcp_max_orphans;
extern int sysctl_tcp_fack;
extern int sysctl_tcp_reordering;
extern int sysctl_tcp_ecn;
extern int sysctl_tcp_dsack;
extern int sysctl_tcp_wmem[3];
extern int sysctl_tcp_rmem[3];
extern int sysctl_tcp_app_win;
extern int sysctl_tcp_adv_win_scale;
extern int sysctl_tcp_tw_reuse;
extern int sysctl_tcp_frto;
extern int sysctl_tcp_frto_response;
extern int sysctl_tcp_low_latency;
extern int sysctl_tcp_dma_copybreak;
extern int sysctl_tcp_nometrics_save;
extern int sysctl_tcp_moderate_rcvbuf;
extern int sysctl_tcp_tso_win_divisor;
extern int sysctl_tcp_abc;
extern int sysctl_tcp_mtu_probing;
extern int sysctl_tcp_base_mss;
extern int sysctl_tcp_workaround_signed_windows;
extern int sysctl_tcp_slow_start_after_idle;
extern int sysctl_tcp_max_ssthresh;
extern int sysctl_tcp_cookie_size;
extern int sysctl_tcp_thin_linear_timeouts;
extern int sysctl_tcp_thin_dupack;

#ifdef CONFIG_HTC_TCP_SYN_FAIL
extern __be32 sysctl_tcp_syn_fail;
#endif 

extern atomic_long_t tcp_memory_allocated;
extern struct percpu_counter tcp_sockets_allocated;
extern int tcp_memory_pressure;


static inline int before(__u32 seq1, __u32 seq2)
{
        return (__s32)(seq1-seq2) < 0;
}
#define after(seq2, seq1) 	before(seq1, seq2)

static inline int between(__u32 seq1, __u32 seq2, __u32 seq3)
{
	return seq3 - seq2 >= seq1 - seq2;
}

static inline bool tcp_out_of_memory(struct sock *sk)
{
	if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
	    sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
		return true;
	return false;
}

static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
{
	struct percpu_counter *ocp = sk->sk_prot->orphan_count;
	int orphans = percpu_counter_read_positive(ocp);

	if (orphans << shift > sysctl_tcp_max_orphans) {
		orphans = percpu_counter_sum_positive(ocp);
		if (orphans << shift > sysctl_tcp_max_orphans)
			return true;
	}
	return false;
}

extern bool tcp_check_oom(struct sock *sk, int shift);

static inline void tcp_synq_overflow(struct sock *sk)
{
	tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
}

static inline int tcp_synq_no_recent_overflow(const struct sock *sk)
{
	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
	return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
}

extern struct proto tcp_prot;

#define TCP_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.tcp_statistics, field)
#define TCP_INC_STATS_BH(net, field)	SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
#define TCP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
#define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
#define TCP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)

extern void tcp_init_mem(struct net *net);

extern void tcp_v4_err(struct sk_buff *skb, u32);

extern void tcp_shutdown (struct sock *sk, int how);

extern int tcp_v4_rcv(struct sk_buff *skb);

extern struct inet_peer *tcp_v4_get_peer(struct sock *sk, bool *release_it);
extern void *tcp_v4_tw_get_peer(struct sock *sk);
extern int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
extern int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
		       size_t size);
extern int tcp_sendpage(struct sock *sk, struct page *page, int offset,
			size_t size, int flags);
extern int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
extern int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
				 const struct tcphdr *th, unsigned int len);
extern int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
			       const struct tcphdr *th, unsigned int len);
extern void tcp_rcv_space_adjust(struct sock *sk);
extern void tcp_cleanup_rbuf(struct sock *sk, int copied);
extern int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
extern void tcp_twsk_destructor(struct sock *sk);
extern ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
			       struct pipe_inode_info *pipe, size_t len,
			       unsigned int flags);

static inline void tcp_dec_quickack_mode(struct sock *sk,
					 const unsigned int pkts)
{
	struct inet_connection_sock *icsk = inet_csk(sk);

	if (icsk->icsk_ack.quick) {
		if (pkts >= icsk->icsk_ack.quick) {
			icsk->icsk_ack.quick = 0;
			
			icsk->icsk_ack.ato   = TCP_ATO_MIN;
		} else
			icsk->icsk_ack.quick -= pkts;
	}
}

#define	TCP_ECN_OK		1
#define	TCP_ECN_QUEUE_CWR	2
#define	TCP_ECN_DEMAND_CWR	4
#define	TCP_ECN_SEEN		8

static __inline__ void
TCP_ECN_create_request(struct request_sock *req, struct tcphdr *th)
{
	if (sysctl_tcp_ecn && th->ece && th->cwr)
		inet_rsk(req)->ecn_ok = 1;
}

enum tcp_tw_status {
	TCP_TW_SUCCESS = 0,
	TCP_TW_RST = 1,
	TCP_TW_ACK = 2,
	TCP_TW_SYN = 3
};


extern enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
						     struct sk_buff *skb,
						     const struct tcphdr *th);
extern struct sock * tcp_check_req(struct sock *sk,struct sk_buff *skb,
				   struct request_sock *req,
				   struct request_sock **prev);
extern int tcp_child_process(struct sock *parent, struct sock *child,
			     struct sk_buff *skb);
extern int tcp_use_frto(struct sock *sk);
extern void tcp_enter_frto(struct sock *sk);
extern void tcp_enter_loss(struct sock *sk, int how);
extern void tcp_clear_retrans(struct tcp_sock *tp);
extern void tcp_update_metrics(struct sock *sk);
extern void tcp_close(struct sock *sk, long timeout);
extern unsigned int tcp_poll(struct file * file, struct socket *sock,
			     struct poll_table_struct *wait);
extern int tcp_getsockopt(struct sock *sk, int level, int optname,
			  char __user *optval, int __user *optlen);
extern int tcp_setsockopt(struct sock *sk, int level, int optname,
			  char __user *optval, unsigned int optlen);
extern int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
				 char __user *optval, int __user *optlen);
extern int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
				 char __user *optval, unsigned int optlen);
extern void tcp_set_keepalive(struct sock *sk, int val);
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,
			      int estab);
extern const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);


extern void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
extern int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
extern struct sock * tcp_create_openreq_child(struct sock *sk,
					      struct request_sock *req,
					      struct sk_buff *skb);
extern struct sock * tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
					  struct request_sock *req,
					  struct dst_entry *dst);
extern int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
extern int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr,
			  int addr_len);
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);
extern int tcp_disconnect(struct sock *sk, int flags);


extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
extern struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, 
				    struct ip_options *opt);
#ifdef CONFIG_SYN_COOKIES
extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, 
				     __u16 *mss);
#else
static inline __u32 cookie_v4_init_sequence(struct sock *sk,
					    struct sk_buff *skb,
					    __u16 *mss)
{
	return 0;
}
#endif

extern __u32 cookie_init_timestamp(struct request_sock *req);
extern bool cookie_check_timestamp(struct tcp_options_received *opt, bool *);

extern struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
#ifdef CONFIG_SYN_COOKIES
extern __u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb,
				     __u16 *mss);
#else
static inline __u32 cookie_v6_init_sequence(struct sock *sk,
					    struct sk_buff *skb,
					    __u16 *mss)
{
	return 0;
}
#endif

extern void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
				      int nonagle);
extern int tcp_may_send_now(struct sock *sk);
extern int tcp_retransmit_skb(struct sock *, struct sk_buff *);
extern void tcp_retransmit_timer(struct sock *sk);
extern void tcp_xmit_retransmit_queue(struct sock *);
extern void tcp_simple_retransmit(struct sock *);
extern int tcp_trim_head(struct sock *, struct sk_buff *, u32);
extern int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int);

extern void tcp_send_probe0(struct sock *);
extern void tcp_send_partial(struct sock *);
extern int tcp_write_wakeup(struct sock *);
extern void tcp_send_fin(struct sock *sk);
extern void tcp_send_active_reset(struct sock *sk, gfp_t priority);
extern int tcp_send_synack(struct sock *);
extern int tcp_syn_flood_action(struct sock *sk,
				const struct sk_buff *skb,
				const char *proto);
extern void tcp_push_one(struct sock *, unsigned int mss_now);
extern void tcp_send_ack(struct sock *sk);
extern void tcp_send_delayed_ack(struct sock *sk);

extern void tcp_cwnd_application_limited(struct sock *sk);

extern void tcp_init_xmit_timers(struct sock *);
static inline void tcp_clear_xmit_timers(struct sock *sk)
{
	inet_csk_clear_xmit_timers(sk);
}

extern unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
extern unsigned int tcp_current_mss(struct sock *sk);

static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
{
	int cutoff;

	if (tp->max_window >= 512)
		cutoff = (tp->max_window >> 1);
	else
		cutoff = tp->max_window;

	if (cutoff && pktsize > cutoff)
		return max_t(int, cutoff, 68U - tp->tcp_header_len);
	else
		return pktsize;
}

extern void tcp_get_info(const struct sock *, struct tcp_info *);

typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
				unsigned int, size_t);
extern int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
			 sk_read_actor_t recv_actor);

extern void tcp_initialize_rcv_mss(struct sock *sk);

extern int tcp_mtu_to_mss(const struct sock *sk, int pmtu);
extern int tcp_mss_to_mtu(const struct sock *sk, int mss);
extern void tcp_mtup_init(struct sock *sk);
extern void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt);

static inline void tcp_bound_rto(const struct sock *sk)
{
	if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
		inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
}

static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
{
	return (tp->srtt >> 3) + tp->rttvar;
}

static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
{
	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
			       ntohl(TCP_FLAG_ACK) |
			       snd_wnd);
}

static inline void tcp_fast_path_on(struct tcp_sock *tp)
{
	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
}

static inline void tcp_fast_path_check(struct sock *sk)
{
	struct tcp_sock *tp = tcp_sk(sk);

	if (skb_queue_empty(&tp->out_of_order_queue) &&
	    tp->rcv_wnd &&
	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
	    !tp->urg_data)
		tcp_fast_path_on(tp);
}

static inline u32 tcp_rto_min(struct sock *sk)
{
	const struct dst_entry *dst = __sk_dst_get(sk);
	u32 rto_min = TCP_RTO_MIN;

	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
	return rto_min;
}

static inline u32 tcp_receive_window(const struct tcp_sock *tp)
{
	s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;

	if (win < 0)
		win = 0;
	return (u32) win;
}

extern u32 __tcp_select_window(struct sock *sk);

#define tcp_time_stamp		((__u32)(jiffies))

#define tcp_flag_byte(th) (((u_int8_t *)th)[13])

#define TCPHDR_FIN 0x01
#define TCPHDR_SYN 0x02
#define TCPHDR_RST 0x04
#define TCPHDR_PSH 0x08
#define TCPHDR_ACK 0x10
#define TCPHDR_URG 0x20
#define TCPHDR_ECE 0x40
#define TCPHDR_CWR 0x80

struct tcp_skb_cb {
	union {
		struct inet_skb_parm	h4;
#if IS_ENABLED(CONFIG_IPV6)
		struct inet6_skb_parm	h6;
#endif
	} header;	
	__u32		seq;		
	__u32		end_seq;	
	__u32		when;		
	__u8		tcp_flags;	
	__u8		sacked;		
#define TCPCB_SACKED_ACKED	0x01	
#define TCPCB_SACKED_RETRANS	0x02	
#define TCPCB_LOST		0x04	
#define TCPCB_TAGBITS		0x07	
	__u8		ip_dsfield;	
	
#define TCPCB_EVER_RETRANS	0x80	
#define TCPCB_RETRANS		(TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)

	__u32		ack_seq;	
};

#define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))

static inline int tcp_skb_pcount(const struct sk_buff *skb)
{
	return skb_shinfo(skb)->gso_segs;
}

static inline int tcp_skb_mss(const struct sk_buff *skb)
{
	return skb_shinfo(skb)->gso_size;
}

enum tcp_ca_event {
	CA_EVENT_TX_START,	
	CA_EVENT_CWND_RESTART,	
	CA_EVENT_COMPLETE_CWR,	
	CA_EVENT_FRTO,		
	CA_EVENT_LOSS,		
	CA_EVENT_FAST_ACK,	
	CA_EVENT_SLOW_ACK,	
};

#define TCP_CA_NAME_MAX	16
#define TCP_CA_MAX	128
#define TCP_CA_BUF_MAX	(TCP_CA_NAME_MAX*TCP_CA_MAX)

#define TCP_CONG_NON_RESTRICTED 0x1
#define TCP_CONG_RTT_STAMP	0x2

struct tcp_congestion_ops {
	struct list_head	list;
	unsigned long flags;

	
	void (*init)(struct sock *sk);
	
	void (*release)(struct sock *sk);

	
	u32 (*ssthresh)(struct sock *sk);
	
	u32 (*min_cwnd)(const struct sock *sk);
	
	void (*cong_avoid)(struct sock *sk, u32 ack, u32 in_flight);
	
	void (*set_state)(struct sock *sk, u8 new_state);
	
	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
	
	u32  (*undo_cwnd)(struct sock *sk);
	
	void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
	
	void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);

	char 		name[TCP_CA_NAME_MAX];
	struct module 	*owner;
};

extern int tcp_register_congestion_control(struct tcp_congestion_ops *type);
extern void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);

extern void tcp_init_congestion_control(struct sock *sk);
extern void tcp_cleanup_congestion_control(struct sock *sk);
extern int tcp_set_default_congestion_control(const char *name);
extern void tcp_get_default_congestion_control(char *name);
extern void tcp_get_available_congestion_control(char *buf, size_t len);
extern void tcp_get_allowed_congestion_control(char *buf, size_t len);
extern int tcp_set_allowed_congestion_control(char *allowed);
extern int tcp_set_congestion_control(struct sock *sk, const char *name);
extern void tcp_slow_start(struct tcp_sock *tp);
extern void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);

extern struct tcp_congestion_ops tcp_init_congestion_ops;
extern u32 tcp_reno_ssthresh(struct sock *sk);
extern void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight);
extern u32 tcp_reno_min_cwnd(const struct sock *sk);
extern struct tcp_congestion_ops tcp_reno;

static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
{
	struct inet_connection_sock *icsk = inet_csk(sk);

	if (icsk->icsk_ca_ops->set_state)
		icsk->icsk_ca_ops->set_state(sk, ca_state);
	icsk->icsk_ca_state = ca_state;
}

static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
{
	const struct inet_connection_sock *icsk = inet_csk(sk);

	if (icsk->icsk_ca_ops->cwnd_event)
		icsk->icsk_ca_ops->cwnd_event(sk, event);
}

static inline int tcp_is_sack(const struct tcp_sock *tp)
{
	return tp->rx_opt.sack_ok;
}

static inline int tcp_is_reno(const struct tcp_sock *tp)
{
	return !tcp_is_sack(tp);
}

static inline int tcp_is_fack(const struct tcp_sock *tp)
{
	return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
}

static inline void tcp_enable_fack(struct tcp_sock *tp)
{
	tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
}

static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
{
	return tp->sacked_out + tp->lost_out;
}

static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
{
	return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
}

#define TCP_INFINITE_SSTHRESH	0x7fffffff

static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
{
	return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
}

static inline __u32 tcp_current_ssthresh(const struct sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);

	if ((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_CWR | TCPF_CA_Recovery))
		return tp->snd_ssthresh;
	else
		return max(tp->snd_ssthresh,
			   ((tp->snd_cwnd >> 1) +
			    (tp->snd_cwnd >> 2)));
}

#define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)

extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);
extern __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);

static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
{
	return 3;
}

static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
{
	return tp->reordering;
}

static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
{
	return tp->snd_una + tp->snd_wnd;
}
extern int tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight);

static inline void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss,
				       const struct sk_buff *skb)
{
	if (skb->len < mss)
		tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
}

static inline void tcp_check_probe_timer(struct sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);

	if (!tp->packets_out && !icsk->icsk_pending)
		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
					  icsk->icsk_rto, TCP_RTO_MAX);
}

static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
{
	tp->snd_wl1 = seq;
}

static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
{
	tp->snd_wl1 = seq;
}

static inline __sum16 tcp_v4_check(int len, __be32 saddr,
				   __be32 daddr, __wsum base)
{
	return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
}

static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
{
	return __skb_checksum_complete(skb);
}

static inline int tcp_checksum_complete(struct sk_buff *skb)
{
	return !skb_csum_unnecessary(skb) &&
		__tcp_checksum_complete(skb);
}


static inline void tcp_prequeue_init(struct tcp_sock *tp)
{
	tp->ucopy.task = NULL;
	tp->ucopy.len = 0;
	tp->ucopy.memory = 0;
	skb_queue_head_init(&tp->ucopy.prequeue);
#ifdef CONFIG_NET_DMA
	tp->ucopy.dma_chan = NULL;
	tp->ucopy.wakeup = 0;
	tp->ucopy.pinned_list = NULL;
	tp->ucopy.dma_cookie = 0;
#endif
}

static inline int tcp_prequeue(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_sock *tp = tcp_sk(sk);

	if (sysctl_tcp_low_latency || !tp->ucopy.task)
		return 0;

	__skb_queue_tail(&tp->ucopy.prequeue, skb);
	tp->ucopy.memory += skb->truesize;
	if (tp->ucopy.memory > sk->sk_rcvbuf) {
		struct sk_buff *skb1;

		BUG_ON(sock_owned_by_user(sk));

		while ((skb1 = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) {
			sk_backlog_rcv(sk, skb1);
			NET_INC_STATS_BH(sock_net(sk),
					 LINUX_MIB_TCPPREQUEUEDROPPED);
		}

		tp->ucopy.memory = 0;
	} else if (skb_queue_len(&tp->ucopy.prequeue) == 1) {
		wake_up_interruptible_sync_poll(sk_sleep(sk),
					   POLLIN | POLLRDNORM | POLLRDBAND);
		if (!inet_csk_ack_scheduled(sk))
			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
						  (3 * tcp_rto_min(sk)) / 4,
						  TCP_RTO_MAX);
	}
	return 1;
}


#undef STATE_TRACE

#ifdef STATE_TRACE
static const char *statename[]={
	"Unused","Established","Syn Sent","Syn Recv",
	"Fin Wait 1","Fin Wait 2","Time Wait", "Close",
	"Close Wait","Last ACK","Listen","Closing"
};
#endif
extern void tcp_set_state(struct sock *sk, int state);

extern void tcp_done(struct sock *sk);

static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
{
	rx_opt->dsack = 0;
	rx_opt->num_sacks = 0;
}

extern void tcp_select_initial_window(int __space, __u32 mss,
				      __u32 *rcv_wnd, __u32 *window_clamp,
				      int wscale_ok, __u8 *rcv_wscale,
				      __u32 init_rcv_wnd);

static inline int tcp_win_from_space(int space)
{
	return sysctl_tcp_adv_win_scale<=0 ?
		(space>>(-sysctl_tcp_adv_win_scale)) :
		space - (space>>sysctl_tcp_adv_win_scale);
}

 
static inline int tcp_space(const struct sock *sk)
{
	return tcp_win_from_space(sk->sk_rcvbuf -
				  atomic_read(&sk->sk_rmem_alloc));
} 

static inline int tcp_full_space(const struct sock *sk)
{
	return tcp_win_from_space(sk->sk_rcvbuf); 
}

static inline void tcp_openreq_init(struct request_sock *req,
				    struct tcp_options_received *rx_opt,
				    struct sk_buff *skb)
{
	struct inet_request_sock *ireq = inet_rsk(req);

	req->rcv_wnd = 0;		
	req->cookie_ts = 0;
	tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
	req->mss = rx_opt->mss_clamp;
	req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
	ireq->tstamp_ok = rx_opt->tstamp_ok;
	ireq->sack_ok = rx_opt->sack_ok;
	ireq->snd_wscale = rx_opt->snd_wscale;
	ireq->wscale_ok = rx_opt->wscale_ok;
	ireq->acked = 0;
	ireq->ecn_ok = 0;
	ireq->rmt_port = tcp_hdr(skb)->source;
	ireq->loc_port = tcp_hdr(skb)->dest;
}

extern void tcp_enter_memory_pressure(struct sock *sk);

static inline int keepalive_intvl_when(const struct tcp_sock *tp)
{
	return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
}

static inline int keepalive_time_when(const struct tcp_sock *tp)
{
	return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
}

static inline int keepalive_probes(const struct tcp_sock *tp)
{
	return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
}

static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
{
	const struct inet_connection_sock *icsk = &tp->inet_conn;

	return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
			  tcp_time_stamp - tp->rcv_tstamp);
}

static inline int tcp_fin_time(const struct sock *sk)
{
	int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
	const int rto = inet_csk(sk)->icsk_rto;

	if (fin_timeout < (rto << 2) - (rto >> 1))
		fin_timeout = (rto << 2) - (rto >> 1);

	return fin_timeout;
}

static inline int tcp_paws_check(const struct tcp_options_received *rx_opt,
				 int paws_win)
{
	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
		return 1;
	if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
		return 1;
	if (!rx_opt->ts_recent)
		return 1;
	return 0;
}

static inline int tcp_paws_reject(const struct tcp_options_received *rx_opt,
				  int rst)
{
	if (tcp_paws_check(rx_opt, 0))
		return 0;

	if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
		return 0;
	return 1;
}

static inline void tcp_mib_init(struct net *net)
{
	
	TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
	TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
	TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
	TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
}

static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
{
	tp->lost_skb_hint = NULL;
	tp->scoreboard_skb_hint = NULL;
}

static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
{
	tcp_clear_retrans_hints_partial(tp);
	tp->retransmit_skb_hint = NULL;
}

struct crypto_hash;

union tcp_md5_addr {
	struct in_addr  a4;
#if IS_ENABLED(CONFIG_IPV6)
	struct in6_addr	a6;
#endif
};

struct tcp_md5sig_key {
	struct hlist_node	node;
	u8			keylen;
	u8			family; 
	union tcp_md5_addr	addr;
	u8			key[TCP_MD5SIG_MAXKEYLEN];
	struct rcu_head		rcu;
};

struct tcp_md5sig_info {
	struct hlist_head	head;
	struct rcu_head		rcu;
};

struct tcp4_pseudohdr {
	__be32		saddr;
	__be32		daddr;
	__u8		pad;
	__u8		protocol;
	__be16		len;
};

struct tcp6_pseudohdr {
	struct in6_addr	saddr;
	struct in6_addr daddr;
	__be32		len;
	__be32		protocol;	
};

union tcp_md5sum_block {
	struct tcp4_pseudohdr ip4;
#if IS_ENABLED(CONFIG_IPV6)
	struct tcp6_pseudohdr ip6;
#endif
};

struct tcp_md5sig_pool {
	struct hash_desc	md5_desc;
	union tcp_md5sum_block	md5_blk;
};

extern int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
			       const struct sock *sk,
			       const struct request_sock *req,
			       const struct sk_buff *skb);
extern int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
			  int family, const u8 *newkey,
			  u8 newkeylen, gfp_t gfp);
extern int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
			  int family);
extern struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
					 struct sock *addr_sk);

#ifdef CONFIG_TCP_MD5SIG
extern struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
			const union tcp_md5_addr *addr, int family);
#define tcp_twsk_md5_key(twsk)	((twsk)->tw_md5_key)
#else
static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
					 const union tcp_md5_addr *addr,
					 int family)
{
	return NULL;
}
#define tcp_twsk_md5_key(twsk)	NULL
#endif

extern struct tcp_md5sig_pool __percpu *tcp_alloc_md5sig_pool(struct sock *);
extern void tcp_free_md5sig_pool(void);

extern struct tcp_md5sig_pool	*tcp_get_md5sig_pool(void);
extern void tcp_put_md5sig_pool(void);

extern int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
extern int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
				 unsigned header_len);
extern int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
			    const struct tcp_md5sig_key *key);

static inline void tcp_write_queue_purge(struct sock *sk)
{
	struct sk_buff *skb;

	while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
		sk_wmem_free_skb(sk, skb);
	sk_mem_reclaim(sk);
	tcp_clear_all_retrans_hints(tcp_sk(sk));
}

static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
{
	return skb_peek(&sk->sk_write_queue);
}

static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
{
	return skb_peek_tail(&sk->sk_write_queue);
}

static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
						   const struct sk_buff *skb)
{
	return skb_queue_next(&sk->sk_write_queue, skb);
}

static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
						   const struct sk_buff *skb)
{
	return skb_queue_prev(&sk->sk_write_queue, skb);
}

#define tcp_for_write_queue(skb, sk)					\
	skb_queue_walk(&(sk)->sk_write_queue, skb)

#define tcp_for_write_queue_from(skb, sk)				\
	skb_queue_walk_from(&(sk)->sk_write_queue, skb)

#define tcp_for_write_queue_from_safe(skb, tmp, sk)			\
	skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)

static inline struct sk_buff *tcp_send_head(const struct sock *sk)
{
	return sk->sk_send_head;
}

static inline bool tcp_skb_is_last(const struct sock *sk,
				   const struct sk_buff *skb)
{
	return skb_queue_is_last(&sk->sk_write_queue, skb);
}

static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
{
	if (tcp_skb_is_last(sk, skb))
		sk->sk_send_head = NULL;
	else
		sk->sk_send_head = tcp_write_queue_next(sk, skb);
}

static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
{
	if (sk->sk_send_head == skb_unlinked)
		sk->sk_send_head = NULL;
}

static inline void tcp_init_send_head(struct sock *sk)
{
	sk->sk_send_head = NULL;
}

static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
{
	__skb_queue_tail(&sk->sk_write_queue, skb);
}

static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
{
	__tcp_add_write_queue_tail(sk, skb);

	
	if (sk->sk_send_head == NULL) {
		sk->sk_send_head = skb;

		if (tcp_sk(sk)->highest_sack == NULL)
			tcp_sk(sk)->highest_sack = skb;
	}
}

static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
{
	__skb_queue_head(&sk->sk_write_queue, skb);
}

static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
						struct sk_buff *buff,
						struct sock *sk)
{
	__skb_queue_after(&sk->sk_write_queue, skb, buff);
}

static inline void tcp_insert_write_queue_before(struct sk_buff *new,
						  struct sk_buff *skb,
						  struct sock *sk)
{
	__skb_queue_before(&sk->sk_write_queue, skb, new);

	if (sk->sk_send_head == skb)
		sk->sk_send_head = new;
}

static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
{
	__skb_unlink(skb, &sk->sk_write_queue);
}

static inline int tcp_write_queue_empty(struct sock *sk)
{
	return skb_queue_empty(&sk->sk_write_queue);
}

static inline void tcp_push_pending_frames(struct sock *sk)
{
	if (tcp_send_head(sk)) {
		struct tcp_sock *tp = tcp_sk(sk);

		__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
	}
}

static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
{
	if (!tp->sacked_out)
		return tp->snd_una;

	if (tp->highest_sack == NULL)
		return tp->snd_nxt;

	return TCP_SKB_CB(tp->highest_sack)->seq;
}

static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
{
	tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
						tcp_write_queue_next(sk, skb);
}

static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
{
	return tcp_sk(sk)->highest_sack;
}

static inline void tcp_highest_sack_reset(struct sock *sk)
{
	tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
}

static inline void tcp_highest_sack_combine(struct sock *sk,
					    struct sk_buff *old,
					    struct sk_buff *new)
{
	if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
		tcp_sk(sk)->highest_sack = new;
}

static inline unsigned int tcp_stream_is_thin(struct tcp_sock *tp)
{
	return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
}

enum tcp_seq_states {
	TCP_SEQ_STATE_LISTENING,
	TCP_SEQ_STATE_OPENREQ,
	TCP_SEQ_STATE_ESTABLISHED,
	TCP_SEQ_STATE_TIME_WAIT,
};

int tcp_seq_open(struct inode *inode, struct file *file);

struct tcp_seq_afinfo {
	char				*name;
	sa_family_t			family;
	const struct file_operations	*seq_fops;
	struct seq_operations		seq_ops;
};

struct tcp_iter_state {
	struct seq_net_private	p;
	sa_family_t		family;
	enum tcp_seq_states	state;
	struct sock		*syn_wait_sk;
	int			bucket, offset, sbucket, num, uid;
	loff_t			last_pos;
};

extern int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
extern void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);

extern struct request_sock_ops tcp_request_sock_ops;
extern struct request_sock_ops tcp6_request_sock_ops;

extern void tcp_v4_destroy_sock(struct sock *sk);

extern int tcp_v4_gso_send_check(struct sk_buff *skb);
extern struct sk_buff *tcp_tso_segment(struct sk_buff *skb,
				       netdev_features_t features);
extern struct sk_buff **tcp_gro_receive(struct sk_buff **head,
					struct sk_buff *skb);
extern struct sk_buff **tcp4_gro_receive(struct sk_buff **head,
					 struct sk_buff *skb);
extern int tcp_gro_complete(struct sk_buff *skb);
extern int tcp4_gro_complete(struct sk_buff *skb);

extern int tcp_nuke_addr(struct net *net, struct sockaddr *addr);

#ifdef CONFIG_PROC_FS
extern int tcp4_proc_init(void);
extern void tcp4_proc_exit(void);
#endif

struct tcp_sock_af_ops {
#ifdef CONFIG_TCP_MD5SIG
	struct tcp_md5sig_key	*(*md5_lookup) (struct sock *sk,
						struct sock *addr_sk);
	int			(*calc_md5_hash) (char *location,
						  struct tcp_md5sig_key *md5,
						  const struct sock *sk,
						  const struct request_sock *req,
						  const struct sk_buff *skb);
	int			(*md5_parse) (struct sock *sk,
					      char __user *optval,
					      int optlen);
#endif
};

struct tcp_request_sock_ops {
#ifdef CONFIG_TCP_MD5SIG
	struct tcp_md5sig_key	*(*md5_lookup) (struct sock *sk,
						struct request_sock *req);
	int			(*calc_md5_hash) (char *location,
						  struct tcp_md5sig_key *md5,
						  const struct sock *sk,
						  const struct request_sock *req,
						  const struct sk_buff *skb);
#endif
};

#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 {
	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));
}

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 {
	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);

#endif