1/*
   2 * INET		An implementation of the TCP/IP protocol suite for the LINUX
   3 *		operating system.  INET is implemented using the  BSD Socket
   4 *		interface as the means of communication with the user level.
   5 *
   6 *		Definitions for the TCP module.
   7 *
   8 * Version:	@(#)tcp.h	1.0.5	05/23/93
   9 *
  10 * Authors:	Ross Biro
  11 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  12 *
  13 *		This program is free software; you can redistribute it and/or
  14 *		modify it under the terms of the GNU General Public License
  15 *		as published by the Free Software Foundation; either version
  16 *		2 of the License, or (at your option) any later version.
  17 */
  18#ifndef _TCP_H
  19#define _TCP_H
  20
  21#define FASTRETRANS_DEBUG 1
  22
  23#include <linux/list.h>
  24#include <linux/tcp.h>
  25#include <linux/bug.h>
  26#include <linux/slab.h>
  27#include <linux/cache.h>
  28#include <linux/percpu.h>
  29#include <linux/skbuff.h>
  30#include <linux/cryptohash.h>
  31#include <linux/kref.h>
  32#include <linux/ktime.h>
  33
  34#include <net/inet_connection_sock.h>
  35#include <net/inet_timewait_sock.h>
  36#include <net/inet_hashtables.h>
  37#include <net/checksum.h>
  38#include <net/request_sock.h>
  39#include <net/sock.h>
  40#include <net/snmp.h>
  41#include <net/ip.h>
  42#include <net/tcp_states.h>
  43#include <net/inet_ecn.h>
  44#include <net/dst.h>
  45
  46#include <linux/seq_file.h>
  47#include <linux/memcontrol.h>
 
  48
  49extern struct inet_hashinfo tcp_hashinfo;
  50
  51extern struct percpu_counter tcp_orphan_count;
  52void tcp_time_wait(struct sock *sk, int state, int timeo);
  53
  54#define MAX_TCP_HEADER	(128 + MAX_HEADER)
  55#define MAX_TCP_OPTION_SPACE 40
  56
  57/*
  58 * Never offer a window over 32767 without using window scaling. Some
  59 * poor stacks do signed 16bit maths!
  60 */
  61#define MAX_TCP_WINDOW		32767U
  62
  63/* Minimal accepted MSS. It is (60+60+8) - (20+20). */
  64#define TCP_MIN_MSS		88U
  65
  66/* The least MTU to use for probing */
  67#define TCP_BASE_MSS		1024
  68
  69/* probing interval, default to 10 minutes as per RFC4821 */
  70#define TCP_PROBE_INTERVAL	600
  71
  72/* Specify interval when tcp mtu probing will stop */
  73#define TCP_PROBE_THRESHOLD	8
  74
  75/* After receiving this amount of duplicate ACKs fast retransmit starts. */
  76#define TCP_FASTRETRANS_THRESH 3
  77
  78/* Maximal number of ACKs sent quickly to accelerate slow-start. */
  79#define TCP_MAX_QUICKACKS	16U
  80
 
 
 
  81/* urg_data states */
  82#define TCP_URG_VALID	0x0100
  83#define TCP_URG_NOTYET	0x0200
  84#define TCP_URG_READ	0x0400
  85
  86#define TCP_RETR1	3	/*
  87				 * This is how many retries it does before it
  88				 * tries to figure out if the gateway is
  89				 * down. Minimal RFC value is 3; it corresponds
  90				 * to ~3sec-8min depending on RTO.
  91				 */
  92
  93#define TCP_RETR2	15	/*
  94				 * This should take at least
  95				 * 90 minutes to time out.
  96				 * RFC1122 says that the limit is 100 sec.
  97				 * 15 is ~13-30min depending on RTO.
  98				 */
  99
 100#define TCP_SYN_RETRIES	 6	/* This is how many retries are done
 101				 * when active opening a connection.
 102				 * RFC1122 says the minimum retry MUST
 103				 * be at least 180secs.  Nevertheless
 104				 * this value is corresponding to
 105				 * 63secs of retransmission with the
 106				 * current initial RTO.
 107				 */
 108
 109#define TCP_SYNACK_RETRIES 5	/* This is how may retries are done
 110				 * when passive opening a connection.
 111				 * This is corresponding to 31secs of
 112				 * retransmission with the current
 113				 * initial RTO.
 114				 */
 115
 116#define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
 117				  * state, about 60 seconds	*/
 118#define TCP_FIN_TIMEOUT	TCP_TIMEWAIT_LEN
 119                                 /* BSD style FIN_WAIT2 deadlock breaker.
 120				  * It used to be 3min, new value is 60sec,
 121				  * to combine FIN-WAIT-2 timeout with
 122				  * TIME-WAIT timer.
 123				  */
 124
 125#define TCP_DELACK_MAX	((unsigned)(HZ/5))	/* maximal time to delay before sending an ACK */
 126#if HZ >= 100
 127#define TCP_DELACK_MIN	((unsigned)(HZ/25))	/* minimal time to delay before sending an ACK */
 128#define TCP_ATO_MIN	((unsigned)(HZ/25))
 129#else
 130#define TCP_DELACK_MIN	4U
 131#define TCP_ATO_MIN	4U
 132#endif
 133#define TCP_RTO_MAX	((unsigned)(120*HZ))
 134#define TCP_RTO_MIN	((unsigned)(HZ/5))
 
 135#define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))	/* RFC6298 2.1 initial RTO value	*/
 136#define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value, now
 137						 * used as a fallback RTO for the
 138						 * initial data transmission if no
 139						 * valid RTT sample has been acquired,
 140						 * most likely due to retrans in 3WHS.
 141						 */
 142
 143#define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
 144					                 * for local resources.
 145					                 */
 146
 147#define TCP_KEEPALIVE_TIME	(120*60*HZ)	/* two hours */
 148#define TCP_KEEPALIVE_PROBES	9		/* Max of 9 keepalive probes	*/
 149#define TCP_KEEPALIVE_INTVL	(75*HZ)
 150
 151#define MAX_TCP_KEEPIDLE	32767
 152#define MAX_TCP_KEEPINTVL	32767
 153#define MAX_TCP_KEEPCNT		127
 154#define MAX_TCP_SYNCNT		127
 155
 156#define TCP_SYNQ_INTERVAL	(HZ/5)	/* Period of SYNACK timer */
 157
 158#define TCP_PAWS_24DAYS	(60 * 60 * 24 * 24)
 159#define TCP_PAWS_MSL	60		/* Per-host timestamps are invalidated
 160					 * after this time. It should be equal
 161					 * (or greater than) TCP_TIMEWAIT_LEN
 162					 * to provide reliability equal to one
 163					 * provided by timewait state.
 164					 */
 165#define TCP_PAWS_WINDOW	1		/* Replay window for per-host
 166					 * timestamps. It must be less than
 167					 * minimal timewait lifetime.
 168					 */
 169/*
 170 *	TCP option
 171 */
 172
 173#define TCPOPT_NOP		1	/* Padding */
 174#define TCPOPT_EOL		0	/* End of options */
 175#define TCPOPT_MSS		2	/* Segment size negotiating */
 176#define TCPOPT_WINDOW		3	/* Window scaling */
 177#define TCPOPT_SACK_PERM        4       /* SACK Permitted */
 178#define TCPOPT_SACK             5       /* SACK Block */
 179#define TCPOPT_TIMESTAMP	8	/* Better RTT estimations/PAWS */
 180#define TCPOPT_MD5SIG		19	/* MD5 Signature (RFC2385) */
 181#define TCPOPT_FASTOPEN		34	/* Fast open (RFC7413) */
 182#define TCPOPT_EXP		254	/* Experimental */
 183/* Magic number to be after the option value for sharing TCP
 184 * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
 185 */
 186#define TCPOPT_FASTOPEN_MAGIC	0xF989
 
 187
 188/*
 189 *     TCP option lengths
 190 */
 191
 192#define TCPOLEN_MSS            4
 193#define TCPOLEN_WINDOW         3
 194#define TCPOLEN_SACK_PERM      2
 195#define TCPOLEN_TIMESTAMP      10
 196#define TCPOLEN_MD5SIG         18
 197#define TCPOLEN_FASTOPEN_BASE  2
 198#define TCPOLEN_EXP_FASTOPEN_BASE  4
 
 199
 200/* But this is what stacks really send out. */
 201#define TCPOLEN_TSTAMP_ALIGNED		12
 202#define TCPOLEN_WSCALE_ALIGNED		4
 203#define TCPOLEN_SACKPERM_ALIGNED	4
 204#define TCPOLEN_SACK_BASE		2
 205#define TCPOLEN_SACK_BASE_ALIGNED	4
 206#define TCPOLEN_SACK_PERBLOCK		8
 207#define TCPOLEN_MD5SIG_ALIGNED		20
 208#define TCPOLEN_MSS_ALIGNED		4
 
 209
 210/* Flags in tp->nonagle */
 211#define TCP_NAGLE_OFF		1	/* Nagle's algo is disabled */
 212#define TCP_NAGLE_CORK		2	/* Socket is corked	    */
 213#define TCP_NAGLE_PUSH		4	/* Cork is overridden for already queued data */
 214
 215/* TCP thin-stream limits */
 216#define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
 217
 218/* TCP initial congestion window as per rfc6928 */
 219#define TCP_INIT_CWND		10
 220
 221/* Bit Flags for sysctl_tcp_fastopen */
 222#define	TFO_CLIENT_ENABLE	1
 223#define	TFO_SERVER_ENABLE	2
 224#define	TFO_CLIENT_NO_COOKIE	4	/* Data in SYN w/o cookie option */
 225
 226/* Accept SYN data w/o any cookie option */
 227#define	TFO_SERVER_COOKIE_NOT_REQD	0x200
 228
 229/* Force enable TFO on all listeners, i.e., not requiring the
 230 * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
 231 */
 232#define	TFO_SERVER_WO_SOCKOPT1	0x400
 233#define	TFO_SERVER_WO_SOCKOPT2	0x800
 234
 235extern struct inet_timewait_death_row tcp_death_row;
 236
 237/* sysctl variables for tcp */
 238extern int sysctl_tcp_timestamps;
 239extern int sysctl_tcp_window_scaling;
 240extern int sysctl_tcp_sack;
 241extern int sysctl_tcp_fastopen;
 242extern int sysctl_tcp_retrans_collapse;
 243extern int sysctl_tcp_stdurg;
 244extern int sysctl_tcp_rfc1337;
 245extern int sysctl_tcp_abort_on_overflow;
 246extern int sysctl_tcp_max_orphans;
 247extern int sysctl_tcp_fack;
 248extern int sysctl_tcp_reordering;
 249extern int sysctl_tcp_max_reordering;
 250extern int sysctl_tcp_dsack;
 251extern long sysctl_tcp_mem[3];
 252extern int sysctl_tcp_wmem[3];
 253extern int sysctl_tcp_rmem[3];
 254extern int sysctl_tcp_app_win;
 255extern int sysctl_tcp_adv_win_scale;
 256extern int sysctl_tcp_tw_reuse;
 257extern int sysctl_tcp_frto;
 258extern int sysctl_tcp_low_latency;
 259extern int sysctl_tcp_nometrics_save;
 260extern int sysctl_tcp_moderate_rcvbuf;
 261extern int sysctl_tcp_tso_win_divisor;
 262extern int sysctl_tcp_workaround_signed_windows;
 263extern int sysctl_tcp_slow_start_after_idle;
 264extern int sysctl_tcp_thin_linear_timeouts;
 265extern int sysctl_tcp_thin_dupack;
 266extern int sysctl_tcp_early_retrans;
 267extern int sysctl_tcp_limit_output_bytes;
 268extern int sysctl_tcp_challenge_ack_limit;
 269extern int sysctl_tcp_min_tso_segs;
 270extern int sysctl_tcp_min_rtt_wlen;
 271extern int sysctl_tcp_autocorking;
 272extern int sysctl_tcp_invalid_ratelimit;
 273extern int sysctl_tcp_pacing_ss_ratio;
 274extern int sysctl_tcp_pacing_ca_ratio;
 275
 276extern atomic_long_t tcp_memory_allocated;
 277extern struct percpu_counter tcp_sockets_allocated;
 278extern int tcp_memory_pressure;
 279
 280/* optimized version of sk_under_memory_pressure() for TCP sockets */
 281static inline bool tcp_under_memory_pressure(const struct sock *sk)
 282{
 283	if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
 284	    mem_cgroup_under_socket_pressure(sk->sk_memcg))
 285		return true;
 286
 287	return tcp_memory_pressure;
 288}
 289/*
 290 * The next routines deal with comparing 32 bit unsigned ints
 291 * and worry about wraparound (automatic with unsigned arithmetic).
 292 */
 293
 294static inline bool before(__u32 seq1, __u32 seq2)
 295{
 296        return (__s32)(seq1-seq2) < 0;
 297}
 298#define after(seq2, seq1) 	before(seq1, seq2)
 299
 300/* is s2<=s1<=s3 ? */
 301static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
 302{
 303	return seq3 - seq2 >= seq1 - seq2;
 304}
 305
 306static inline bool tcp_out_of_memory(struct sock *sk)
 307{
 308	if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
 309	    sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
 310		return true;
 311	return false;
 312}
 313
 314void sk_forced_mem_schedule(struct sock *sk, int size);
 315
 316static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
 317{
 318	struct percpu_counter *ocp = sk->sk_prot->orphan_count;
 319	int orphans = percpu_counter_read_positive(ocp);
 320
 321	if (orphans << shift > sysctl_tcp_max_orphans) {
 322		orphans = percpu_counter_sum_positive(ocp);
 323		if (orphans << shift > sysctl_tcp_max_orphans)
 324			return true;
 325	}
 326	return false;
 327}
 328
 329bool tcp_check_oom(struct sock *sk, int shift);
 330
 331
 332extern struct proto tcp_prot;
 333
 334#define TCP_INC_STATS(net, field)	SNMP_INC_STATS((net)->mib.tcp_statistics, field)
 335#define TCP_INC_STATS_BH(net, field)	SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
 336#define TCP_DEC_STATS(net, field)	SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
 337#define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
 338#define TCP_ADD_STATS(net, field, val)	SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
 339
 340void tcp_tasklet_init(void);
 341
 342void tcp_v4_err(struct sk_buff *skb, u32);
 343
 344void tcp_shutdown(struct sock *sk, int how);
 345
 346void tcp_v4_early_demux(struct sk_buff *skb);
 347int tcp_v4_rcv(struct sk_buff *skb);
 348
 349int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
 350int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
 
 351int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
 352		 int flags);
 
 
 
 
 353void tcp_release_cb(struct sock *sk);
 354void tcp_wfree(struct sk_buff *skb);
 355void tcp_write_timer_handler(struct sock *sk);
 356void tcp_delack_timer_handler(struct sock *sk);
 357int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
 358int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb);
 359void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 360			 const struct tcphdr *th, unsigned int len);
 361void tcp_rcv_space_adjust(struct sock *sk);
 362int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
 363void tcp_twsk_destructor(struct sock *sk);
 364ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
 365			struct pipe_inode_info *pipe, size_t len,
 366			unsigned int flags);
 367
 368static inline void tcp_dec_quickack_mode(struct sock *sk,
 369					 const unsigned int pkts)
 370{
 371	struct inet_connection_sock *icsk = inet_csk(sk);
 372
 373	if (icsk->icsk_ack.quick) {
 374		if (pkts >= icsk->icsk_ack.quick) {
 375			icsk->icsk_ack.quick = 0;
 376			/* Leaving quickack mode we deflate ATO. */
 377			icsk->icsk_ack.ato   = TCP_ATO_MIN;
 378		} else
 379			icsk->icsk_ack.quick -= pkts;
 380	}
 381}
 382
 383#define	TCP_ECN_OK		1
 384#define	TCP_ECN_QUEUE_CWR	2
 385#define	TCP_ECN_DEMAND_CWR	4
 386#define	TCP_ECN_SEEN		8
 387
 388enum tcp_tw_status {
 389	TCP_TW_SUCCESS = 0,
 390	TCP_TW_RST = 1,
 391	TCP_TW_ACK = 2,
 392	TCP_TW_SYN = 3
 393};
 394
 395
 396enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
 397					      struct sk_buff *skb,
 398					      const struct tcphdr *th);
 399struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
 400			   struct request_sock *req, bool fastopen);
 
 401int tcp_child_process(struct sock *parent, struct sock *child,
 402		      struct sk_buff *skb);
 403void tcp_enter_loss(struct sock *sk);
 
 404void tcp_clear_retrans(struct tcp_sock *tp);
 405void tcp_update_metrics(struct sock *sk);
 406void tcp_init_metrics(struct sock *sk);
 407void tcp_metrics_init(void);
 408bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
 409			bool paws_check, bool timestamps);
 410bool tcp_remember_stamp(struct sock *sk);
 411bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
 412void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
 413void tcp_disable_fack(struct tcp_sock *tp);
 414void tcp_close(struct sock *sk, long timeout);
 415void tcp_init_sock(struct sock *sk);
 416unsigned int tcp_poll(struct file *file, struct socket *sock,
 
 417		      struct poll_table_struct *wait);
 418int tcp_getsockopt(struct sock *sk, int level, int optname,
 419		   char __user *optval, int __user *optlen);
 420int tcp_setsockopt(struct sock *sk, int level, int optname,
 421		   char __user *optval, unsigned int optlen);
 422int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
 423			  char __user *optval, int __user *optlen);
 424int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
 425			  char __user *optval, unsigned int optlen);
 426void tcp_set_keepalive(struct sock *sk, int val);
 427void tcp_syn_ack_timeout(const struct request_sock *req);
 428int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
 429		int flags, int *addr_len);
 430void tcp_parse_options(const struct sk_buff *skb,
 431		       struct tcp_options_received *opt_rx,
 432		       int estab, struct tcp_fastopen_cookie *foc);
 433const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
 434
 435/*
 436 *	TCP v4 functions exported for the inet6 API
 437 */
 438
 439void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
 440void tcp_v4_mtu_reduced(struct sock *sk);
 441void tcp_req_err(struct sock *sk, u32 seq, bool abort);
 442int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
 443struct sock *tcp_create_openreq_child(const struct sock *sk,
 444				      struct request_sock *req,
 445				      struct sk_buff *skb);
 446void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
 447struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
 448				  struct request_sock *req,
 449				  struct dst_entry *dst,
 450				  struct request_sock *req_unhash,
 451				  bool *own_req);
 452int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
 453int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
 454int tcp_connect(struct sock *sk);
 
 
 
 
 
 455struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
 456				struct request_sock *req,
 457				struct tcp_fastopen_cookie *foc,
 458				bool attach_req);
 459int tcp_disconnect(struct sock *sk, int flags);
 460
 461void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
 462int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
 463void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
 464
 465/* From syncookies.c */
 466struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
 467				 struct request_sock *req,
 468				 struct dst_entry *dst);
 469int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
 470		      u32 cookie);
 471struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
 472#ifdef CONFIG_SYN_COOKIES
 473
 474/* Syncookies use a monotonic timer which increments every 60 seconds.
 475 * This counter is used both as a hash input and partially encoded into
 476 * the cookie value.  A cookie is only validated further if the delta
 477 * between the current counter value and the encoded one is less than this,
 478 * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
 479 * the counter advances immediately after a cookie is generated).
 480 */
 481#define MAX_SYNCOOKIE_AGE	2
 482#define TCP_SYNCOOKIE_PERIOD	(60 * HZ)
 483#define TCP_SYNCOOKIE_VALID	(MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
 484
 485/* syncookies: remember time of last synqueue overflow
 486 * But do not dirty this field too often (once per second is enough)
 487 * It is racy as we do not hold a lock, but race is very minor.
 488 */
 489static inline void tcp_synq_overflow(const struct sock *sk)
 490{
 491	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
 492	unsigned long now = jiffies;
 493
 494	if (time_after(now, last_overflow + HZ))
 495		tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
 496}
 497
 498/* syncookies: no recent synqueue overflow on this listening socket? */
 499static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
 500{
 501	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
 502
 503	return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
 504}
 505
 506static inline u32 tcp_cookie_time(void)
 507{
 508	u64 val = get_jiffies_64();
 509
 510	do_div(val, TCP_SYNCOOKIE_PERIOD);
 511	return val;
 512}
 513
 514u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
 515			      u16 *mssp);
 516__u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mss);
 517__u32 cookie_init_timestamp(struct request_sock *req);
 518bool cookie_timestamp_decode(struct tcp_options_received *opt);
 
 519bool cookie_ecn_ok(const struct tcp_options_received *opt,
 520		   const struct net *net, const struct dst_entry *dst);
 521
 522/* From net/ipv6/syncookies.c */
 523int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
 524		      u32 cookie);
 525struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
 526
 527u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
 528			      const struct tcphdr *th, u16 *mssp);
 529__u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss);
 530#endif
 531/* tcp_output.c */
 532
 533void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
 534			       int nonagle);
 535bool tcp_may_send_now(struct sock *sk);
 536int __tcp_retransmit_skb(struct sock *, struct sk_buff *);
 537int tcp_retransmit_skb(struct sock *, struct sk_buff *);
 538void tcp_retransmit_timer(struct sock *sk);
 539void tcp_xmit_retransmit_queue(struct sock *);
 540void tcp_simple_retransmit(struct sock *);
 
 541int tcp_trim_head(struct sock *, struct sk_buff *, u32);
 542int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
 
 
 
 
 
 
 543
 544void tcp_send_probe0(struct sock *);
 545void tcp_send_partial(struct sock *);
 546int tcp_write_wakeup(struct sock *, int mib);
 547void tcp_send_fin(struct sock *sk);
 548void tcp_send_active_reset(struct sock *sk, gfp_t priority);
 549int tcp_send_synack(struct sock *);
 550void tcp_push_one(struct sock *, unsigned int mss_now);
 551void tcp_send_ack(struct sock *sk);
 552void tcp_send_delayed_ack(struct sock *sk);
 553void tcp_send_loss_probe(struct sock *sk);
 554bool tcp_schedule_loss_probe(struct sock *sk);
 555void tcp_skb_collapse_tstamp(struct sk_buff *skb,
 556			     const struct sk_buff *next_skb);
 557
 558/* tcp_input.c */
 559void tcp_resume_early_retransmit(struct sock *sk);
 560void tcp_rearm_rto(struct sock *sk);
 561void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
 562void tcp_reset(struct sock *sk);
 563void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb);
 564void tcp_fin(struct sock *sk);
 565
 566/* tcp_timer.c */
 567void tcp_init_xmit_timers(struct sock *);
 568static inline void tcp_clear_xmit_timers(struct sock *sk)
 569{
 
 570	inet_csk_clear_xmit_timers(sk);
 571}
 572
 573unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
 574unsigned int tcp_current_mss(struct sock *sk);
 575
 576/* Bound MSS / TSO packet size with the half of the window */
 577static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
 578{
 579	int cutoff;
 580
 581	/* When peer uses tiny windows, there is no use in packetizing
 582	 * to sub-MSS pieces for the sake of SWS or making sure there
 583	 * are enough packets in the pipe for fast recovery.
 584	 *
 585	 * On the other hand, for extremely large MSS devices, handling
 586	 * smaller than MSS windows in this way does make sense.
 587	 */
 588	if (tp->max_window >= 512)
 589		cutoff = (tp->max_window >> 1);
 590	else
 591		cutoff = tp->max_window;
 592
 593	if (cutoff && pktsize > cutoff)
 594		return max_t(int, cutoff, 68U - tp->tcp_header_len);
 595	else
 596		return pktsize;
 597}
 598
 599/* tcp.c */
 600void tcp_get_info(struct sock *, struct tcp_info *);
 601
 602/* Read 'sendfile()'-style from a TCP socket */
 603typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
 604				unsigned int, size_t);
 605int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
 606		  sk_read_actor_t recv_actor);
 607
 608void tcp_initialize_rcv_mss(struct sock *sk);
 609
 610int tcp_mtu_to_mss(struct sock *sk, int pmtu);
 611int tcp_mss_to_mtu(struct sock *sk, int mss);
 612void tcp_mtup_init(struct sock *sk);
 613void tcp_init_buffer_space(struct sock *sk);
 614
 615static inline void tcp_bound_rto(const struct sock *sk)
 616{
 617	if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
 618		inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
 619}
 620
 621static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
 622{
 623	return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
 624}
 625
 626static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
 627{
 628	tp->pred_flags = htonl((tp->tcp_header_len << 26) |
 629			       ntohl(TCP_FLAG_ACK) |
 630			       snd_wnd);
 631}
 632
 633static inline void tcp_fast_path_on(struct tcp_sock *tp)
 634{
 635	__tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
 636}
 637
 638static inline void tcp_fast_path_check(struct sock *sk)
 639{
 640	struct tcp_sock *tp = tcp_sk(sk);
 641
 642	if (skb_queue_empty(&tp->out_of_order_queue) &&
 643	    tp->rcv_wnd &&
 644	    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
 645	    !tp->urg_data)
 646		tcp_fast_path_on(tp);
 647}
 648
 649/* Compute the actual rto_min value */
 650static inline u32 tcp_rto_min(struct sock *sk)
 651{
 652	const struct dst_entry *dst = __sk_dst_get(sk);
 653	u32 rto_min = TCP_RTO_MIN;
 654
 655	if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
 656		rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
 657	return rto_min;
 658}
 659
 660static inline u32 tcp_rto_min_us(struct sock *sk)
 661{
 662	return jiffies_to_usecs(tcp_rto_min(sk));
 663}
 664
 665static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
 666{
 667	return dst_metric_locked(dst, RTAX_CC_ALGO);
 668}
 669
 670/* Minimum RTT in usec. ~0 means not available. */
 671static inline u32 tcp_min_rtt(const struct tcp_sock *tp)
 672{
 673	return tp->rtt_min[0].rtt;
 674}
 675
 676/* Compute the actual receive window we are currently advertising.
 677 * Rcv_nxt can be after the window if our peer push more data
 678 * than the offered window.
 679 */
 680static inline u32 tcp_receive_window(const struct tcp_sock *tp)
 681{
 682	s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
 683
 684	if (win < 0)
 685		win = 0;
 686	return (u32) win;
 687}
 688
 689/* Choose a new window, without checks for shrinking, and without
 690 * scaling applied to the result.  The caller does these things
 691 * if necessary.  This is a "raw" window selection.
 692 */
 693u32 __tcp_select_window(struct sock *sk);
 694
 695void tcp_send_window_probe(struct sock *sk);
 696
 697/* TCP timestamps are only 32-bits, this causes a slight
 698 * complication on 64-bit systems since we store a snapshot
 699 * of jiffies in the buffer control blocks below.  We decided
 700 * to use only the low 32-bits of jiffies and hide the ugly
 701 * casts with the following macro.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 702 */
 703#define tcp_time_stamp		((__u32)(jiffies))
 
 
 
 
 
 
 
 
 
 
 
 704
 705static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
 706{
 707	return skb->skb_mstamp.stamp_jiffies;
 708}
 709
 710
 711#define tcp_flag_byte(th) (((u_int8_t *)th)[13])
 712
 713#define TCPHDR_FIN 0x01
 714#define TCPHDR_SYN 0x02
 715#define TCPHDR_RST 0x04
 716#define TCPHDR_PSH 0x08
 717#define TCPHDR_ACK 0x10
 718#define TCPHDR_URG 0x20
 719#define TCPHDR_ECE 0x40
 720#define TCPHDR_CWR 0x80
 721
 722#define TCPHDR_SYN_ECN	(TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
 723
 724/* This is what the send packet queuing engine uses to pass
 725 * TCP per-packet control information to the transmission code.
 726 * We also store the host-order sequence numbers in here too.
 727 * This is 44 bytes if IPV6 is enabled.
 728 * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
 729 */
 730struct tcp_skb_cb {
 731	__u32		seq;		/* Starting sequence number	*/
 732	__u32		end_seq;	/* SEQ + FIN + SYN + datalen	*/
 733	union {
 734		/* Note : tcp_tw_isn is used in input path only
 735		 *	  (isn chosen by tcp_timewait_state_process())
 736		 *
 737		 * 	  tcp_gso_segs/size are used in write queue only,
 738		 *	  cf tcp_skb_pcount()/tcp_skb_mss()
 739		 */
 740		__u32		tcp_tw_isn;
 741		struct {
 742			u16	tcp_gso_segs;
 743			u16	tcp_gso_size;
 744		};
 745	};
 746	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/
 747
 748	__u8		sacked;		/* State flags for SACK/FACK.	*/
 749#define TCPCB_SACKED_ACKED	0x01	/* SKB ACK'd by a SACK block	*/
 750#define TCPCB_SACKED_RETRANS	0x02	/* SKB retransmitted		*/
 751#define TCPCB_LOST		0x04	/* SKB is lost			*/
 752#define TCPCB_TAGBITS		0x07	/* All tag bits			*/
 753#define TCPCB_REPAIRED		0x10	/* SKB repaired (no skb_mstamp)	*/
 754#define TCPCB_EVER_RETRANS	0x80	/* Ever retransmitted frame	*/
 755#define TCPCB_RETRANS		(TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
 756				TCPCB_REPAIRED)
 757
 758	__u8		ip_dsfield;	/* IPv4 tos or IPv6 dsfield	*/
 759	/* 1 byte hole */
 
 
 
 760	__u32		ack_seq;	/* Sequence number ACK'd	*/
 761	union {
 762		struct inet_skb_parm	h4;
 
 
 
 
 
 
 
 
 
 
 
 
 
 763#if IS_ENABLED(CONFIG_IPV6)
 764		struct inet6_skb_parm	h6;
 765#endif
 766	} header;	/* For incoming frames		*/
 
 
 
 
 
 
 
 767};
 768
 769#define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
 770
 771
 772#if IS_ENABLED(CONFIG_IPV6)
 773/* This is the variant of inet6_iif() that must be used by TCP,
 774 * as TCP moves IP6CB into a different location in skb->cb[]
 775 */
 776static inline int tcp_v6_iif(const struct sk_buff *skb)
 777{
 778	return TCP_SKB_CB(skb)->header.h6.iif;
 
 
 779}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 780#endif
 
 
 781
 782/* Due to TSO, an SKB can be composed of multiple actual
 783 * packets.  To keep these tracked properly, we use this.
 784 */
 785static inline int tcp_skb_pcount(const struct sk_buff *skb)
 786{
 787	return TCP_SKB_CB(skb)->tcp_gso_segs;
 788}
 789
 790static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
 791{
 792	TCP_SKB_CB(skb)->tcp_gso_segs = segs;
 793}
 794
 795static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
 796{
 797	TCP_SKB_CB(skb)->tcp_gso_segs += segs;
 798}
 799
 800/* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
 801static inline int tcp_skb_mss(const struct sk_buff *skb)
 802{
 803	return TCP_SKB_CB(skb)->tcp_gso_size;
 804}
 805
 
 
 
 
 
 806/* Events passed to congestion control interface */
 807enum tcp_ca_event {
 808	CA_EVENT_TX_START,	/* first transmit when no packets in flight */
 809	CA_EVENT_CWND_RESTART,	/* congestion window restart */
 810	CA_EVENT_COMPLETE_CWR,	/* end of congestion recovery */
 811	CA_EVENT_LOSS,		/* loss timeout */
 812	CA_EVENT_ECN_NO_CE,	/* ECT set, but not CE marked */
 813	CA_EVENT_ECN_IS_CE,	/* received CE marked IP packet */
 814	CA_EVENT_DELAYED_ACK,	/* Delayed ack is sent */
 815	CA_EVENT_NON_DELAYED_ACK,
 816};
 817
 818/* Information about inbound ACK, passed to cong_ops->in_ack_event() */
 819enum tcp_ca_ack_event_flags {
 820	CA_ACK_SLOWPATH		= (1 << 0),	/* In slow path processing */
 821	CA_ACK_WIN_UPDATE	= (1 << 1),	/* ACK updated window */
 822	CA_ACK_ECE		= (1 << 2),	/* ECE bit is set on ack */
 823};
 824
 825/*
 826 * Interface for adding new TCP congestion control handlers
 827 */
 828#define TCP_CA_NAME_MAX	16
 829#define TCP_CA_MAX	128
 830#define TCP_CA_BUF_MAX	(TCP_CA_NAME_MAX*TCP_CA_MAX)
 831
 832#define TCP_CA_UNSPEC	0
 833
 834/* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
 835#define TCP_CONG_NON_RESTRICTED 0x1
 836/* Requires ECN/ECT set on all packets */
 837#define TCP_CONG_NEEDS_ECN	0x2
 838
 839union tcp_cc_info;
 840
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 841struct tcp_congestion_ops {
 842	struct list_head	list;
 843	u32 key;
 844	u32 flags;
 845
 846	/* initialize private data (optional) */
 847	void (*init)(struct sock *sk);
 848	/* cleanup private data  (optional) */
 849	void (*release)(struct sock *sk);
 850
 851	/* return slow start threshold (required) */
 852	u32 (*ssthresh)(struct sock *sk);
 853	/* do new cwnd calculation (required) */
 854	void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
 855	/* call before changing ca_state (optional) */
 856	void (*set_state)(struct sock *sk, u8 new_state);
 857	/* call when cwnd event occurs (optional) */
 858	void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
 859	/* call when ack arrives (optional) */
 860	void (*in_ack_event)(struct sock *sk, u32 flags);
 861	/* new value of cwnd after loss (optional) */
 862	u32  (*undo_cwnd)(struct sock *sk);
 863	/* hook for packet ack accounting (optional) */
 864	void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
 
 
 
 
 
 
 
 
 865	/* get info for inet_diag (optional) */
 866	size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
 867			   union tcp_cc_info *info);
 868
 869	char 		name[TCP_CA_NAME_MAX];
 870	struct module 	*owner;
 871};
 872
 873int tcp_register_congestion_control(struct tcp_congestion_ops *type);
 874void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
 875
 876void tcp_assign_congestion_control(struct sock *sk);
 877void tcp_init_congestion_control(struct sock *sk);
 878void tcp_cleanup_congestion_control(struct sock *sk);
 879int tcp_set_default_congestion_control(const char *name);
 880void tcp_get_default_congestion_control(char *name);
 881void tcp_get_available_congestion_control(char *buf, size_t len);
 882void tcp_get_allowed_congestion_control(char *buf, size_t len);
 883int tcp_set_allowed_congestion_control(char *allowed);
 884int tcp_set_congestion_control(struct sock *sk, const char *name);
 885u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
 886void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
 887
 888u32 tcp_reno_ssthresh(struct sock *sk);
 
 889void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
 890extern struct tcp_congestion_ops tcp_reno;
 891
 892struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
 893u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
 894#ifdef CONFIG_INET
 895char *tcp_ca_get_name_by_key(u32 key, char *buffer);
 896#else
 897static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
 898{
 899	return NULL;
 900}
 901#endif
 902
 903static inline bool tcp_ca_needs_ecn(const struct sock *sk)
 904{
 905	const struct inet_connection_sock *icsk = inet_csk(sk);
 906
 907	return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
 908}
 909
 910static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
 911{
 912	struct inet_connection_sock *icsk = inet_csk(sk);
 913
 914	if (icsk->icsk_ca_ops->set_state)
 915		icsk->icsk_ca_ops->set_state(sk, ca_state);
 916	icsk->icsk_ca_state = ca_state;
 917}
 918
 919static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
 920{
 921	const struct inet_connection_sock *icsk = inet_csk(sk);
 922
 923	if (icsk->icsk_ca_ops->cwnd_event)
 924		icsk->icsk_ca_ops->cwnd_event(sk, event);
 925}
 926
 
 
 
 
 
 
 
 
 927/* These functions determine how the current flow behaves in respect of SACK
 928 * handling. SACK is negotiated with the peer, and therefore it can vary
 929 * between different flows.
 930 *
 931 * tcp_is_sack - SACK enabled
 932 * tcp_is_reno - No SACK
 933 * tcp_is_fack - FACK enabled, implies SACK enabled
 934 */
 935static inline int tcp_is_sack(const struct tcp_sock *tp)
 936{
 937	return tp->rx_opt.sack_ok;
 938}
 939
 940static inline bool tcp_is_reno(const struct tcp_sock *tp)
 941{
 942	return !tcp_is_sack(tp);
 943}
 944
 945static inline bool tcp_is_fack(const struct tcp_sock *tp)
 946{
 947	return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
 948}
 949
 950static inline void tcp_enable_fack(struct tcp_sock *tp)
 951{
 952	tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
 953}
 954
 955/* TCP early-retransmit (ER) is similar to but more conservative than
 956 * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
 957 */
 958static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
 959{
 960	struct net *net = sock_net((struct sock *)tp);
 961
 962	tp->do_early_retrans = sysctl_tcp_early_retrans &&
 963		sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
 964		net->ipv4.sysctl_tcp_reordering == 3;
 965}
 966
 967static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
 968{
 969	tp->do_early_retrans = 0;
 970}
 971
 972static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
 973{
 974	return tp->sacked_out + tp->lost_out;
 975}
 976
 977/* This determines how many packets are "in the network" to the best
 978 * of our knowledge.  In many cases it is conservative, but where
 979 * detailed information is available from the receiver (via SACK
 980 * blocks etc.) we can make more aggressive calculations.
 981 *
 982 * Use this for decisions involving congestion control, use just
 983 * tp->packets_out to determine if the send queue is empty or not.
 984 *
 985 * Read this equation as:
 986 *
 987 *	"Packets sent once on transmission queue" MINUS
 988 *	"Packets left network, but not honestly ACKed yet" PLUS
 989 *	"Packets fast retransmitted"
 990 */
 991static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
 992{
 993	return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
 994}
 995
 996#define TCP_INFINITE_SSTHRESH	0x7fffffff
 997
 998static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
 999{
1000	return tp->snd_cwnd < tp->snd_ssthresh;
1001}
1002
1003static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1004{
1005	return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1006}
1007
1008static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1009{
1010	return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1011	       (1 << inet_csk(sk)->icsk_ca_state);
1012}
1013
1014/* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1015 * The exception is cwnd reduction phase, when cwnd is decreasing towards
1016 * ssthresh.
1017 */
1018static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1019{
1020	const struct tcp_sock *tp = tcp_sk(sk);
1021
1022	if (tcp_in_cwnd_reduction(sk))
1023		return tp->snd_ssthresh;
1024	else
1025		return max(tp->snd_ssthresh,
1026			   ((tp->snd_cwnd >> 1) +
1027			    (tp->snd_cwnd >> 2)));
1028}
1029
1030/* Use define here intentionally to get WARN_ON location shown at the caller */
1031#define tcp_verify_left_out(tp)	WARN_ON(tcp_left_out(tp) > tp->packets_out)
1032
1033void tcp_enter_cwr(struct sock *sk);
1034__u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1035
1036/* The maximum number of MSS of available cwnd for which TSO defers
1037 * sending if not using sysctl_tcp_tso_win_divisor.
1038 */
1039static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1040{
1041	return 3;
1042}
1043
1044/* Slow start with delack produces 3 packets of burst, so that
1045 * it is safe "de facto".  This will be the default - same as
1046 * the default reordering threshold - but if reordering increases,
1047 * we must be able to allow cwnd to burst at least this much in order
1048 * to not pull it back when holes are filled.
1049 */
1050static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
1051{
1052	return tp->reordering;
1053}
1054
1055/* Returns end sequence number of the receiver's advertised window */
1056static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1057{
1058	return tp->snd_una + tp->snd_wnd;
1059}
1060
1061/* We follow the spirit of RFC2861 to validate cwnd but implement a more
1062 * flexible approach. The RFC suggests cwnd should not be raised unless
1063 * it was fully used previously. And that's exactly what we do in
1064 * congestion avoidance mode. But in slow start we allow cwnd to grow
1065 * as long as the application has used half the cwnd.
1066 * Example :
1067 *    cwnd is 10 (IW10), but application sends 9 frames.
1068 *    We allow cwnd to reach 18 when all frames are ACKed.
1069 * This check is safe because it's as aggressive as slow start which already
1070 * risks 100% overshoot. The advantage is that we discourage application to
1071 * either send more filler packets or data to artificially blow up the cwnd
1072 * usage, and allow application-limited process to probe bw more aggressively.
1073 */
1074static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1075{
1076	const struct tcp_sock *tp = tcp_sk(sk);
1077
1078	/* If in slow start, ensure cwnd grows to twice what was ACKed. */
1079	if (tcp_in_slow_start(tp))
1080		return tp->snd_cwnd < 2 * tp->max_packets_out;
1081
1082	return tp->is_cwnd_limited;
1083}
1084
1085/* Something is really bad, we could not queue an additional packet,
1086 * because qdisc is full or receiver sent a 0 window.
1087 * We do not want to add fuel to the fire, or abort too early,
1088 * so make sure the timer we arm now is at least 200ms in the future,
1089 * regardless of current icsk_rto value (as it could be ~2ms)
1090 */
1091static inline unsigned long tcp_probe0_base(const struct sock *sk)
1092{
1093	return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1094}
1095
1096/* Variant of inet_csk_rto_backoff() used for zero window probes */
1097static inline unsigned long tcp_probe0_when(const struct sock *sk,
1098					    unsigned long max_when)
1099{
1100	u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;
1101
1102	return (unsigned long)min_t(u64, when, max_when);
1103}
1104
1105static inline void tcp_check_probe_timer(struct sock *sk)
1106{
1107	if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1108		inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1109					  tcp_probe0_base(sk), TCP_RTO_MAX);
1110}
1111
1112static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1113{
1114	tp->snd_wl1 = seq;
1115}
1116
1117static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1118{
1119	tp->snd_wl1 = seq;
1120}
1121
1122/*
1123 * Calculate(/check) TCP checksum
1124 */
1125static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1126				   __be32 daddr, __wsum base)
1127{
1128	return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1129}
1130
1131static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1132{
1133	return __skb_checksum_complete(skb);
1134}
1135
1136static inline bool tcp_checksum_complete(struct sk_buff *skb)
1137{
1138	return !skb_csum_unnecessary(skb) &&
1139		__tcp_checksum_complete(skb);
1140}
1141
1142/* Prequeue for VJ style copy to user, combined with checksumming. */
1143
1144static inline void tcp_prequeue_init(struct tcp_sock *tp)
1145{
1146	tp->ucopy.task = NULL;
1147	tp->ucopy.len = 0;
1148	tp->ucopy.memory = 0;
1149	skb_queue_head_init(&tp->ucopy.prequeue);
1150}
1151
1152bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1153
1154#undef STATE_TRACE
1155
1156#ifdef STATE_TRACE
1157static const char *statename[]={
1158	"Unused","Established","Syn Sent","Syn Recv",
1159	"Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1160	"Close Wait","Last ACK","Listen","Closing"
1161};
1162#endif
1163void tcp_set_state(struct sock *sk, int state);
1164
1165void tcp_done(struct sock *sk);
1166
1167int tcp_abort(struct sock *sk, int err);
1168
1169static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1170{
1171	rx_opt->dsack = 0;
1172	rx_opt->num_sacks = 0;
1173}
1174
1175u32 tcp_default_init_rwnd(u32 mss);
1176void tcp_cwnd_restart(struct sock *sk, s32 delta);
1177
1178static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1179{
 
1180	struct tcp_sock *tp = tcp_sk(sk);
1181	s32 delta;
1182
1183	if (!sysctl_tcp_slow_start_after_idle || tp->packets_out)
 
1184		return;
1185	delta = tcp_time_stamp - tp->lsndtime;
1186	if (delta > inet_csk(sk)->icsk_rto)
1187		tcp_cwnd_restart(sk, delta);
1188}
1189
1190/* Determine a window scaling and initial window to offer. */
1191void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
 
1192			       __u32 *window_clamp, int wscale_ok,
1193			       __u8 *rcv_wscale, __u32 init_rcv_wnd);
1194
1195static inline int tcp_win_from_space(int space)
1196{
1197	return sysctl_tcp_adv_win_scale<=0 ?
1198		(space>>(-sysctl_tcp_adv_win_scale)) :
1199		space - (space>>sysctl_tcp_adv_win_scale);
 
 
1200}
1201
1202/* Note: caller must be prepared to deal with negative returns */
1203static inline int tcp_space(const struct sock *sk)
1204{
1205	return tcp_win_from_space(sk->sk_rcvbuf -
1206				  atomic_read(&sk->sk_rmem_alloc));
1207}
1208
1209static inline int tcp_full_space(const struct sock *sk)
1210{
1211	return tcp_win_from_space(sk->sk_rcvbuf);
1212}
1213
1214extern void tcp_openreq_init_rwin(struct request_sock *req,
1215				  const struct sock *sk_listener,
1216				  const struct dst_entry *dst);
1217
1218void tcp_enter_memory_pressure(struct sock *sk);
 
1219
1220static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1221{
1222	struct net *net = sock_net((struct sock *)tp);
1223
1224	return tp->keepalive_intvl ? : net->ipv4.sysctl_tcp_keepalive_intvl;
1225}
1226
1227static inline int keepalive_time_when(const struct tcp_sock *tp)
1228{
1229	struct net *net = sock_net((struct sock *)tp);
1230
1231	return tp->keepalive_time ? : net->ipv4.sysctl_tcp_keepalive_time;
1232}
1233
1234static inline int keepalive_probes(const struct tcp_sock *tp)
1235{
1236	struct net *net = sock_net((struct sock *)tp);
1237
1238	return tp->keepalive_probes ? : net->ipv4.sysctl_tcp_keepalive_probes;
1239}
1240
1241static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1242{
1243	const struct inet_connection_sock *icsk = &tp->inet_conn;
1244
1245	return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1246			  tcp_time_stamp - tp->rcv_tstamp);
1247}
1248
1249static inline int tcp_fin_time(const struct sock *sk)
1250{
1251	int fin_timeout = tcp_sk(sk)->linger2 ? : sock_net(sk)->ipv4.sysctl_tcp_fin_timeout;
1252	const int rto = inet_csk(sk)->icsk_rto;
1253
1254	if (fin_timeout < (rto << 2) - (rto >> 1))
1255		fin_timeout = (rto << 2) - (rto >> 1);
1256
1257	return fin_timeout;
1258}
1259
1260static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1261				  int paws_win)
1262{
1263	if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1264		return true;
1265	if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1266		return true;
1267	/*
1268	 * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1269	 * then following tcp messages have valid values. Ignore 0 value,
1270	 * or else 'negative' tsval might forbid us to accept their packets.
1271	 */
1272	if (!rx_opt->ts_recent)
1273		return true;
1274	return false;
1275}
1276
1277static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1278				   int rst)
1279{
1280	if (tcp_paws_check(rx_opt, 0))
1281		return false;
1282
1283	/* RST segments are not recommended to carry timestamp,
1284	   and, if they do, it is recommended to ignore PAWS because
1285	   "their cleanup function should take precedence over timestamps."
1286	   Certainly, it is mistake. It is necessary to understand the reasons
1287	   of this constraint to relax it: if peer reboots, clock may go
1288	   out-of-sync and half-open connections will not be reset.
1289	   Actually, the problem would be not existing if all
1290	   the implementations followed draft about maintaining clock
1291	   via reboots. Linux-2.2 DOES NOT!
1292
1293	   However, we can relax time bounds for RST segments to MSL.
1294	 */
1295	if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1296		return false;
1297	return true;
1298}
1299
1300bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1301			  int mib_idx, u32 *last_oow_ack_time);
1302
1303static inline void tcp_mib_init(struct net *net)
1304{
1305	/* See RFC 2012 */
1306	TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1307	TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1308	TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1309	TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1310}
1311
1312/* from STCP */
1313static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1314{
1315	tp->lost_skb_hint = NULL;
1316}
1317
1318static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1319{
1320	tcp_clear_retrans_hints_partial(tp);
1321	tp->retransmit_skb_hint = NULL;
1322}
1323
1324union tcp_md5_addr {
1325	struct in_addr  a4;
1326#if IS_ENABLED(CONFIG_IPV6)
1327	struct in6_addr	a6;
1328#endif
1329};
1330
1331/* - key database */
1332struct tcp_md5sig_key {
1333	struct hlist_node	node;
1334	u8			keylen;
1335	u8			family; /* AF_INET or AF_INET6 */
1336	union tcp_md5_addr	addr;
 
1337	u8			key[TCP_MD5SIG_MAXKEYLEN];
1338	struct rcu_head		rcu;
1339};
1340
1341/* - sock block */
1342struct tcp_md5sig_info {
1343	struct hlist_head	head;
1344	struct rcu_head		rcu;
1345};
1346
1347/* - pseudo header */
1348struct tcp4_pseudohdr {
1349	__be32		saddr;
1350	__be32		daddr;
1351	__u8		pad;
1352	__u8		protocol;
1353	__be16		len;
1354};
1355
1356struct tcp6_pseudohdr {
1357	struct in6_addr	saddr;
1358	struct in6_addr daddr;
1359	__be32		len;
1360	__be32		protocol;	/* including padding */
1361};
1362
1363union tcp_md5sum_block {
1364	struct tcp4_pseudohdr ip4;
1365#if IS_ENABLED(CONFIG_IPV6)
1366	struct tcp6_pseudohdr ip6;
1367#endif
1368};
1369
1370/* - pool: digest algorithm, hash description and scratch buffer */
1371struct tcp_md5sig_pool {
1372	struct ahash_request	*md5_req;
1373	union tcp_md5sum_block	md5_blk;
1374};
1375
1376/* - functions */
1377int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1378			const struct sock *sk, const struct sk_buff *skb);
1379int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1380		   int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
 
1381int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1382		   int family);
1383struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
1384					 const struct sock *addr_sk);
1385
1386#ifdef CONFIG_TCP_MD5SIG
1387struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1388					 const union tcp_md5_addr *addr,
1389					 int family);
1390#define tcp_twsk_md5_key(twsk)	((twsk)->tw_md5_key)
1391#else
1392static inline struct tcp_md5sig_key *tcp_md5_do_lookup(const struct sock *sk,
1393					 const union tcp_md5_addr *addr,
1394					 int family)
1395{
1396	return NULL;
1397}
1398#define tcp_twsk_md5_key(twsk)	NULL
1399#endif
1400
1401bool tcp_alloc_md5sig_pool(void);
1402
1403struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1404static inline void tcp_put_md5sig_pool(void)
1405{
1406	local_bh_enable();
1407}
1408
1409int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1410int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1411			  unsigned int header_len);
1412int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1413		     const struct tcp_md5sig_key *key);
1414
1415/* From tcp_fastopen.c */
1416void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1417			    struct tcp_fastopen_cookie *cookie, int *syn_loss,
1418			    unsigned long *last_syn_loss);
1419void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1420			    struct tcp_fastopen_cookie *cookie, bool syn_lost,
1421			    u16 try_exp);
1422struct tcp_fastopen_request {
1423	/* Fast Open cookie. Size 0 means a cookie request */
1424	struct tcp_fastopen_cookie	cookie;
1425	struct msghdr			*data;  /* data in MSG_FASTOPEN */
1426	size_t				size;
1427	int				copied;	/* queued in tcp_connect() */
1428};
1429void tcp_free_fastopen_req(struct tcp_sock *tp);
1430
1431extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1432int tcp_fastopen_reset_cipher(void *key, unsigned int len);
 
1433void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb);
1434struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1435			      struct request_sock *req,
1436			      struct tcp_fastopen_cookie *foc,
1437			      struct dst_entry *dst);
1438void tcp_fastopen_init_key_once(bool publish);
 
 
 
1439#define TCP_FASTOPEN_KEY_LENGTH 16
1440
1441/* Fastopen key context */
1442struct tcp_fastopen_context {
1443	struct crypto_cipher	*tfm;
1444	__u8			key[TCP_FASTOPEN_KEY_LENGTH];
1445	struct rcu_head		rcu;
1446};
1447
1448/* write queue abstraction */
1449static inline void tcp_write_queue_purge(struct sock *sk)
1450{
1451	struct sk_buff *skb;
 
 
 
 
 
 
 
 
 
 
 
 
1452
1453	while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1454		sk_wmem_free_skb(sk, skb);
1455	sk_mem_reclaim(sk);
1456	tcp_clear_all_retrans_hints(tcp_sk(sk));
1457}
1458
1459static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
 
 
 
1460{
1461	return skb_peek(&sk->sk_write_queue);
 
1462}
1463
1464static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1465{
1466	return skb_peek_tail(&sk->sk_write_queue);
 
 
 
1467}
1468
1469static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1470						   const struct sk_buff *skb)
 
1471{
1472	return skb_queue_next(&sk->sk_write_queue, skb);
1473}
1474
1475static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1476						   const struct sk_buff *skb)
1477{
1478	return skb_queue_prev(&sk->sk_write_queue, skb);
1479}
1480
1481#define tcp_for_write_queue(skb, sk)					\
1482	skb_queue_walk(&(sk)->sk_write_queue, skb)
1483
1484#define tcp_for_write_queue_from(skb, sk)				\
1485	skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1486
1487#define tcp_for_write_queue_from_safe(skb, tmp, sk)			\
1488	skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1489
1490static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1491{
1492	return sk->sk_send_head;
1493}
1494
1495static inline bool tcp_skb_is_last(const struct sock *sk,
1496				   const struct sk_buff *skb)
1497{
1498	return skb_queue_is_last(&sk->sk_write_queue, skb);
1499}
1500
1501static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1502{
1503	if (tcp_skb_is_last(sk, skb))
1504		sk->sk_send_head = NULL;
1505	else
1506		sk->sk_send_head = tcp_write_queue_next(sk, skb);
1507}
1508
1509static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
 
 
 
 
 
1510{
1511	if (sk->sk_send_head == skb_unlinked)
1512		sk->sk_send_head = NULL;
1513}
1514
1515static inline void tcp_init_send_head(struct sock *sk)
1516{
1517	sk->sk_send_head = NULL;
 
1518}
1519
1520static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1521{
1522	__skb_queue_tail(&sk->sk_write_queue, skb);
1523}
1524
1525static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1526{
1527	__tcp_add_write_queue_tail(sk, skb);
1528
1529	/* Queue it, remembering where we must start sending. */
1530	if (sk->sk_send_head == NULL) {
1531		sk->sk_send_head = skb;
1532
1533		if (tcp_sk(sk)->highest_sack == NULL)
1534			tcp_sk(sk)->highest_sack = skb;
1535	}
1536}
1537
1538static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1539{
1540	__skb_queue_head(&sk->sk_write_queue, skb);
1541}
1542
1543/* Insert buff after skb on the write queue of sk.  */
1544static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1545						struct sk_buff *buff,
1546						struct sock *sk)
1547{
1548	__skb_queue_after(&sk->sk_write_queue, skb, buff);
1549}
1550
1551/* Insert new before skb on the write queue of sk.  */
1552static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1553						  struct sk_buff *skb,
1554						  struct sock *sk)
1555{
1556	__skb_queue_before(&sk->sk_write_queue, skb, new);
1557
1558	if (sk->sk_send_head == skb)
1559		sk->sk_send_head = new;
1560}
1561
1562static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1563{
 
1564	__skb_unlink(skb, &sk->sk_write_queue);
1565}
1566
1567static inline bool tcp_write_queue_empty(struct sock *sk)
 
 
1568{
1569	return skb_queue_empty(&sk->sk_write_queue);
 
 
 
 
 
 
 
 
1570}
1571
1572static inline void tcp_push_pending_frames(struct sock *sk)
1573{
1574	if (tcp_send_head(sk)) {
1575		struct tcp_sock *tp = tcp_sk(sk);
1576
1577		__tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1578	}
1579}
1580
1581/* Start sequence of the skb just after the highest skb with SACKed
1582 * bit, valid only if sacked_out > 0 or when the caller has ensured
1583 * validity by itself.
1584 */
1585static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1586{
1587	if (!tp->sacked_out)
1588		return tp->snd_una;
1589
1590	if (tp->highest_sack == NULL)
1591		return tp->snd_nxt;
1592
1593	return TCP_SKB_CB(tp->highest_sack)->seq;
1594}
1595
1596static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1597{
1598	tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1599						tcp_write_queue_next(sk, skb);
1600}
1601
1602static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1603{
1604	return tcp_sk(sk)->highest_sack;
1605}
1606
1607static inline void tcp_highest_sack_reset(struct sock *sk)
1608{
1609	tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1610}
1611
1612/* Called when old skb is about to be deleted (to be combined with new skb) */
1613static inline void tcp_highest_sack_combine(struct sock *sk,
1614					    struct sk_buff *old,
1615					    struct sk_buff *new)
1616{
1617	if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1618		tcp_sk(sk)->highest_sack = new;
1619}
1620
1621/* This helper checks if socket has IP_TRANSPARENT set */
1622static inline bool inet_sk_transparent(const struct sock *sk)
1623{
1624	switch (sk->sk_state) {
1625	case TCP_TIME_WAIT:
1626		return inet_twsk(sk)->tw_transparent;
1627	case TCP_NEW_SYN_RECV:
1628		return inet_rsk(inet_reqsk(sk))->no_srccheck;
1629	}
1630	return inet_sk(sk)->transparent;
1631}
1632
1633/* Determines whether this is a thin stream (which may suffer from
1634 * increased latency). Used to trigger latency-reducing mechanisms.
1635 */
1636static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1637{
1638	return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1639}
1640
1641/* /proc */
1642enum tcp_seq_states {
1643	TCP_SEQ_STATE_LISTENING,
1644	TCP_SEQ_STATE_ESTABLISHED,
1645};
1646
1647int tcp_seq_open(struct inode *inode, struct file *file);
1648
1649struct tcp_seq_afinfo {
1650	char				*name;
1651	sa_family_t			family;
1652	const struct file_operations	*seq_fops;
1653	struct seq_operations		seq_ops;
1654};
1655
1656struct tcp_iter_state {
1657	struct seq_net_private	p;
1658	sa_family_t		family;
1659	enum tcp_seq_states	state;
1660	struct sock		*syn_wait_sk;
1661	int			bucket, offset, sbucket, num;
1662	loff_t			last_pos;
1663};
1664
1665int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1666void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1667
1668extern struct request_sock_ops tcp_request_sock_ops;
1669extern struct request_sock_ops tcp6_request_sock_ops;
1670
1671void tcp_v4_destroy_sock(struct sock *sk);
1672
1673struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1674				netdev_features_t features);
1675struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1676int tcp_gro_complete(struct sk_buff *skb);
1677
1678void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1679
1680static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1681{
1682	struct net *net = sock_net((struct sock *)tp);
1683	return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat;
1684}
1685
1686static inline bool tcp_stream_memory_free(const struct sock *sk)
1687{
1688	const struct tcp_sock *tp = tcp_sk(sk);
1689	u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1690
1691	return notsent_bytes < tcp_notsent_lowat(tp);
1692}
1693
1694#ifdef CONFIG_PROC_FS
1695int tcp4_proc_init(void);
1696void tcp4_proc_exit(void);
1697#endif
1698
1699int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
1700int tcp_conn_request(struct request_sock_ops *rsk_ops,
1701		     const struct tcp_request_sock_ops *af_ops,
1702		     struct sock *sk, struct sk_buff *skb);
1703
1704/* TCP af-specific functions */
1705struct tcp_sock_af_ops {
1706#ifdef CONFIG_TCP_MD5SIG
1707	struct tcp_md5sig_key	*(*md5_lookup) (const struct sock *sk,
1708						const struct sock *addr_sk);
1709	int		(*calc_md5_hash)(char *location,
1710					 const struct tcp_md5sig_key *md5,
1711					 const struct sock *sk,
1712					 const struct sk_buff *skb);
1713	int		(*md5_parse)(struct sock *sk,
 
1714				     char __user *optval,
1715				     int optlen);
1716#endif
1717};
1718
1719struct tcp_request_sock_ops {
1720	u16 mss_clamp;
1721#ifdef CONFIG_TCP_MD5SIG
1722	struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk,
1723						 const struct sock *addr_sk);
1724	int		(*calc_md5_hash) (char *location,
1725					  const struct tcp_md5sig_key *md5,
1726					  const struct sock *sk,
1727					  const struct sk_buff *skb);
1728#endif
1729	void (*init_req)(struct request_sock *req,
1730			 const struct sock *sk_listener,
1731			 struct sk_buff *skb);
1732#ifdef CONFIG_SYN_COOKIES
1733	__u32 (*cookie_init_seq)(const struct sk_buff *skb,
1734				 __u16 *mss);
1735#endif
1736	struct dst_entry *(*route_req)(const struct sock *sk, struct flowi *fl,
1737				       const struct request_sock *req,
1738				       bool *strict);
1739	__u32 (*init_seq)(const struct sk_buff *skb);
1740	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,
1741			   struct flowi *fl, struct request_sock *req,
1742			   struct tcp_fastopen_cookie *foc,
1743			   bool attach_req);
1744};
1745
1746#ifdef CONFIG_SYN_COOKIES
1747static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1748					 const struct sock *sk, struct sk_buff *skb,
1749					 __u16 *mss)
1750{
1751	tcp_synq_overflow(sk);
1752	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
1753	return ops->cookie_init_seq(skb, mss);
1754}
1755#else
1756static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1757					 const struct sock *sk, struct sk_buff *skb,
1758					 __u16 *mss)
1759{
1760	return 0;
1761}
1762#endif
1763
1764int tcpv4_offload_init(void);
1765
1766void tcp_v4_init(void);
1767void tcp_init(void);
1768
1769/* tcp_recovery.c */
 
 
 
 
 
 
 
 
 
 
 
 
1770
1771/* Flags to enable various loss recovery features. See below */
1772extern int sysctl_tcp_recovery;
1773
1774/* Use TCP RACK to detect (some) tail and retransmit losses */
1775#define TCP_RACK_LOST_RETRANS  0x1
1776
1777extern int tcp_rack_mark_lost(struct sock *sk);
1778
1779extern void tcp_rack_advance(struct tcp_sock *tp,
1780			     const struct skb_mstamp *xmit_time, u8 sacked);
1781
1782/*
1783 * Save and compile IPv4 options, return a pointer to it
1784 */
1785static inline struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb)
 
1786{
1787	const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1788	struct ip_options_rcu *dopt = NULL;
1789
1790	if (opt->optlen) {
1791		int opt_size = sizeof(*dopt) + opt->optlen;
1792
1793		dopt = kmalloc(opt_size, GFP_ATOMIC);
1794		if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) {
1795			kfree(dopt);
1796			dopt = NULL;
1797		}
1798	}
1799	return dopt;
1800}
1801
1802/* locally generated TCP pure ACKs have skb->truesize == 2
1803 * (check tcp_send_ack() in net/ipv4/tcp_output.c )
1804 * This is much faster than dissecting the packet to find out.
1805 * (Think of GRE encapsulations, IPv4, IPv6, ...)
1806 */
1807static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
1808{
1809	return skb->truesize == 2;
1810}
1811
1812static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
1813{
1814	skb->truesize = 2;
1815}
1816
1817static inline int tcp_inq(struct sock *sk)
1818{
1819	struct tcp_sock *tp = tcp_sk(sk);
1820	int answ;
1821
1822	if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
1823		answ = 0;
1824	} else if (sock_flag(sk, SOCK_URGINLINE) ||
1825		   !tp->urg_data ||
1826		   before(tp->urg_seq, tp->copied_seq) ||
1827		   !before(tp->urg_seq, tp->rcv_nxt)) {
1828
1829		answ = tp->rcv_nxt - tp->copied_seq;
1830
1831		/* Subtract 1, if FIN was received */
1832		if (answ && sock_flag(sk, SOCK_DONE))
1833			answ--;
1834	} else {
1835		answ = tp->urg_seq - tp->copied_seq;
1836	}
1837
1838	return answ;
1839}
1840
 
 
1841static inline void tcp_segs_in(struct tcp_sock *tp, const struct sk_buff *skb)
1842{
1843	u16 segs_in;
1844
1845	segs_in = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
1846	tp->segs_in += segs_in;
1847	if (skb->len > tcp_hdrlen(skb))
1848		tp->data_segs_in += segs_in;
1849}
1850
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1851#endif	/* _TCP_H */