linux/include/net/tcp.h
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   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/crypto.h>
  31#include <linux/cryptohash.h>
  32#include <linux/kref.h>
  33#include <linux/ktime.h>
  34
  35#include <net/inet_connection_sock.h>
  36#include <net/inet_timewait_sock.h>
  37#include <net/inet_hashtables.h>
  38#include <net/checksum.h>
  39#include <net/request_sock.h>
  40#include <net/sock.h>
  41#include <net/snmp.h>
  42#include <net/ip.h>
  43#include <net/tcp_states.h>
  44#include <net/inet_ecn.h>
  45#include <net/dst.h>
  46
  47#include <linux/seq_file.h>
  48#include <linux/memcontrol.h>
  49
  50extern struct inet_hashinfo tcp_hashinfo;
  51
  52extern struct percpu_counter tcp_orphan_count;
  53void tcp_time_wait(struct sock *sk, int state, int timeo);
  54
  55#define MAX_TCP_HEADER  (128 + MAX_HEADER)
  56#define MAX_TCP_OPTION_SPACE 40
  57
  58/*
  59 * Never offer a window over 32767 without using window scaling. Some
  60 * poor stacks do signed 16bit maths!
  61 */
  62#define MAX_TCP_WINDOW          32767U
  63
  64/* Minimal accepted MSS. It is (60+60+8) - (20+20). */
  65#define TCP_MIN_MSS             88U
  66
  67/* The least MTU to use for probing */
  68#define TCP_BASE_MSS            512
  69
  70/* After receiving this amount of duplicate ACKs fast retransmit starts. */
  71#define TCP_FASTRETRANS_THRESH 3
  72
  73/* Maximal number of ACKs sent quickly to accelerate slow-start. */
  74#define TCP_MAX_QUICKACKS       16U
  75
  76/* urg_data states */
  77#define TCP_URG_VALID   0x0100
  78#define TCP_URG_NOTYET  0x0200
  79#define TCP_URG_READ    0x0400
  80
  81#define TCP_RETR1       3       /*
  82                                 * This is how many retries it does before it
  83                                 * tries to figure out if the gateway is
  84                                 * down. Minimal RFC value is 3; it corresponds
  85                                 * to ~3sec-8min depending on RTO.
  86                                 */
  87
  88#define TCP_RETR2       15      /*
  89                                 * This should take at least
  90                                 * 90 minutes to time out.
  91                                 * RFC1122 says that the limit is 100 sec.
  92                                 * 15 is ~13-30min depending on RTO.
  93                                 */
  94
  95#define TCP_SYN_RETRIES  6      /* This is how many retries are done
  96                                 * when active opening a connection.
  97                                 * RFC1122 says the minimum retry MUST
  98                                 * be at least 180secs.  Nevertheless
  99                                 * this value is corresponding to
 100                                 * 63secs of retransmission with the
 101                                 * current initial RTO.
 102                                 */
 103
 104#define TCP_SYNACK_RETRIES 5    /* This is how may retries are done
 105                                 * when passive opening a connection.
 106                                 * This is corresponding to 31secs of
 107                                 * retransmission with the current
 108                                 * initial RTO.
 109                                 */
 110
 111#define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
 112                                  * state, about 60 seconds     */
 113#define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
 114                                 /* BSD style FIN_WAIT2 deadlock breaker.
 115                                  * It used to be 3min, new value is 60sec,
 116                                  * to combine FIN-WAIT-2 timeout with
 117                                  * TIME-WAIT timer.
 118                                  */
 119
 120#define TCP_DELACK_MAX  ((unsigned)(HZ/5))      /* maximal time to delay before sending an ACK */
 121#if HZ >= 100
 122#define TCP_DELACK_MIN  ((unsigned)(HZ/25))     /* minimal time to delay before sending an ACK */
 123#define TCP_ATO_MIN     ((unsigned)(HZ/25))
 124#else
 125#define TCP_DELACK_MIN  4U
 126#define TCP_ATO_MIN     4U
 127#endif
 128#define TCP_RTO_MAX     ((unsigned)(120*HZ))
 129#define TCP_RTO_MIN     ((unsigned)(HZ/5))
 130#define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))     /* RFC6298 2.1 initial RTO value        */
 131#define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
 132                                                 * used as a fallback RTO for the
 133                                                 * initial data transmission if no
 134                                                 * valid RTT sample has been acquired,
 135                                                 * most likely due to retrans in 3WHS.
 136                                                 */
 137
 138#define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
 139                                                         * for local resources.
 140                                                         */
 141
 142#define TCP_KEEPALIVE_TIME      (120*60*HZ)     /* two hours */
 143#define TCP_KEEPALIVE_PROBES    9               /* Max of 9 keepalive probes    */
 144#define TCP_KEEPALIVE_INTVL     (75*HZ)
 145
 146#define MAX_TCP_KEEPIDLE        32767
 147#define MAX_TCP_KEEPINTVL       32767
 148#define MAX_TCP_KEEPCNT         127
 149#define MAX_TCP_SYNCNT          127
 150
 151#define TCP_SYNQ_INTERVAL       (HZ/5)  /* Period of SYNACK timer */
 152
 153#define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
 154#define TCP_PAWS_MSL    60              /* Per-host timestamps are invalidated
 155                                         * after this time. It should be equal
 156                                         * (or greater than) TCP_TIMEWAIT_LEN
 157                                         * to provide reliability equal to one
 158                                         * provided by timewait state.
 159                                         */
 160#define TCP_PAWS_WINDOW 1               /* Replay window for per-host
 161                                         * timestamps. It must be less than
 162                                         * minimal timewait lifetime.
 163                                         */
 164/*
 165 *      TCP option
 166 */
 167
 168#define TCPOPT_NOP              1       /* Padding */
 169#define TCPOPT_EOL              0       /* End of options */
 170#define TCPOPT_MSS              2       /* Segment size negotiating */
 171#define TCPOPT_WINDOW           3       /* Window scaling */
 172#define TCPOPT_SACK_PERM        4       /* SACK Permitted */
 173#define TCPOPT_SACK             5       /* SACK Block */
 174#define TCPOPT_TIMESTAMP        8       /* Better RTT estimations/PAWS */
 175#define TCPOPT_MD5SIG           19      /* MD5 Signature (RFC2385) */
 176#define TCPOPT_EXP              254     /* Experimental */
 177/* Magic number to be after the option value for sharing TCP
 178 * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
 179 */
 180#define TCPOPT_FASTOPEN_MAGIC   0xF989
 181
 182/*
 183 *     TCP option lengths
 184 */
 185
 186#define TCPOLEN_MSS            4
 187#define TCPOLEN_WINDOW         3
 188#define TCPOLEN_SACK_PERM      2
 189#define TCPOLEN_TIMESTAMP      10
 190#define TCPOLEN_MD5SIG         18
 191#define TCPOLEN_EXP_FASTOPEN_BASE  4
 192
 193/* But this is what stacks really send out. */
 194#define TCPOLEN_TSTAMP_ALIGNED          12
 195#define TCPOLEN_WSCALE_ALIGNED          4
 196#define TCPOLEN_SACKPERM_ALIGNED        4
 197#define TCPOLEN_SACK_BASE               2
 198#define TCPOLEN_SACK_BASE_ALIGNED       4
 199#define TCPOLEN_SACK_PERBLOCK           8
 200#define TCPOLEN_MD5SIG_ALIGNED          20
 201#define TCPOLEN_MSS_ALIGNED             4
 202
 203/* Flags in tp->nonagle */
 204#define TCP_NAGLE_OFF           1       /* Nagle's algo is disabled */
 205#define TCP_NAGLE_CORK          2       /* Socket is corked         */
 206#define TCP_NAGLE_PUSH          4       /* Cork is overridden for already queued data */
 207
 208/* TCP thin-stream limits */
 209#define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
 210
 211/* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
 212#define TCP_INIT_CWND           10
 213
 214/* Bit Flags for sysctl_tcp_fastopen */
 215#define TFO_CLIENT_ENABLE       1
 216#define TFO_SERVER_ENABLE       2
 217#define TFO_CLIENT_NO_COOKIE    4       /* Data in SYN w/o cookie option */
 218
 219/* Accept SYN data w/o any cookie option */
 220#define TFO_SERVER_COOKIE_NOT_REQD      0x200
 221
 222/* Force enable TFO on all listeners, i.e., not requiring the
 223 * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
 224 */
 225#define TFO_SERVER_WO_SOCKOPT1  0x400
 226#define TFO_SERVER_WO_SOCKOPT2  0x800
 227
 228extern struct inet_timewait_death_row tcp_death_row;
 229
 230/* sysctl variables for tcp */
 231extern int sysctl_tcp_timestamps;
 232extern int sysctl_tcp_window_scaling;
 233extern int sysctl_tcp_sack;
 234extern int sysctl_tcp_fin_timeout;
 235extern int sysctl_tcp_keepalive_time;
 236extern int sysctl_tcp_keepalive_probes;
 237extern int sysctl_tcp_keepalive_intvl;
 238extern int sysctl_tcp_syn_retries;
 239extern int sysctl_tcp_synack_retries;
 240extern int sysctl_tcp_retries1;
 241extern int sysctl_tcp_retries2;
 242extern int sysctl_tcp_orphan_retries;
 243extern int sysctl_tcp_syncookies;
 244extern int sysctl_tcp_fastopen;
 245extern int sysctl_tcp_retrans_collapse;
 246extern int sysctl_tcp_stdurg;
 247extern int sysctl_tcp_rfc1337;
 248extern int sysctl_tcp_abort_on_overflow;
 249extern int sysctl_tcp_max_orphans;
 250extern int sysctl_tcp_fack;
 251extern int sysctl_tcp_reordering;
 252extern int sysctl_tcp_max_reordering;
 253extern int sysctl_tcp_dsack;
 254extern long sysctl_tcp_mem[3];
 255extern int sysctl_tcp_wmem[3];
 256extern int sysctl_tcp_rmem[3];
 257extern int sysctl_tcp_app_win;
 258extern int sysctl_tcp_adv_win_scale;
 259extern int sysctl_tcp_tw_reuse;
 260extern int sysctl_tcp_frto;
 261extern int sysctl_tcp_low_latency;
 262extern int sysctl_tcp_nometrics_save;
 263extern int sysctl_tcp_moderate_rcvbuf;
 264extern int sysctl_tcp_tso_win_divisor;
 265extern int sysctl_tcp_mtu_probing;
 266extern int sysctl_tcp_base_mss;
 267extern int sysctl_tcp_workaround_signed_windows;
 268extern int sysctl_tcp_slow_start_after_idle;
 269extern int sysctl_tcp_thin_linear_timeouts;
 270extern int sysctl_tcp_thin_dupack;
 271extern int sysctl_tcp_early_retrans;
 272extern int sysctl_tcp_limit_output_bytes;
 273extern int sysctl_tcp_challenge_ack_limit;
 274extern unsigned int sysctl_tcp_notsent_lowat;
 275extern int sysctl_tcp_min_tso_segs;
 276extern int sysctl_tcp_autocorking;
 277
 278extern atomic_long_t tcp_memory_allocated;
 279extern struct percpu_counter tcp_sockets_allocated;
 280extern int tcp_memory_pressure;
 281
 282/*
 283 * The next routines deal with comparing 32 bit unsigned ints
 284 * and worry about wraparound (automatic with unsigned arithmetic).
 285 */
 286
 287static inline bool before(__u32 seq1, __u32 seq2)
 288{
 289        return (__s32)(seq1-seq2) < 0;
 290}
 291#define after(seq2, seq1)       before(seq1, seq2)
 292
 293/* is s2<=s1<=s3 ? */
 294static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
 295{
 296        return seq3 - seq2 >= seq1 - seq2;
 297}
 298
 299static inline bool tcp_out_of_memory(struct sock *sk)
 300{
 301        if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
 302            sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
 303                return true;
 304        return false;
 305}
 306
 307static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
 308{
 309        struct percpu_counter *ocp = sk->sk_prot->orphan_count;
 310        int orphans = percpu_counter_read_positive(ocp);
 311
 312        if (orphans << shift > sysctl_tcp_max_orphans) {
 313                orphans = percpu_counter_sum_positive(ocp);
 314                if (orphans << shift > sysctl_tcp_max_orphans)
 315                        return true;
 316        }
 317        return false;
 318}
 319
 320bool tcp_check_oom(struct sock *sk, int shift);
 321
 322/* syncookies: remember time of last synqueue overflow */
 323static inline void tcp_synq_overflow(struct sock *sk)
 324{
 325        tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
 326}
 327
 328/* syncookies: no recent synqueue overflow on this listening socket? */
 329static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
 330{
 331        unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
 332        return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
 333}
 334
 335extern struct proto tcp_prot;
 336
 337#define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
 338#define TCP_INC_STATS_BH(net, field)    SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
 339#define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
 340#define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
 341#define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
 342
 343void tcp_tasklet_init(void);
 344
 345void tcp_v4_err(struct sk_buff *skb, u32);
 346
 347void tcp_shutdown(struct sock *sk, int how);
 348
 349void tcp_v4_early_demux(struct sk_buff *skb);
 350int tcp_v4_rcv(struct sk_buff *skb);
 351
 352int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
 353int tcp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 354                size_t size);
 355int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
 356                 int flags);
 357void tcp_release_cb(struct sock *sk);
 358void tcp_wfree(struct sk_buff *skb);
 359void tcp_write_timer_handler(struct sock *sk);
 360void tcp_delack_timer_handler(struct sock *sk);
 361int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
 362int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 363                          const struct tcphdr *th, unsigned int len);
 364void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 365                         const struct tcphdr *th, unsigned int len);
 366void tcp_rcv_space_adjust(struct sock *sk);
 367int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
 368void tcp_twsk_destructor(struct sock *sk);
 369ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
 370                        struct pipe_inode_info *pipe, size_t len,
 371                        unsigned int flags);
 372
 373static inline void tcp_dec_quickack_mode(struct sock *sk,
 374                                         const unsigned int pkts)
 375{
 376        struct inet_connection_sock *icsk = inet_csk(sk);
 377
 378        if (icsk->icsk_ack.quick) {
 379                if (pkts >= icsk->icsk_ack.quick) {
 380                        icsk->icsk_ack.quick = 0;
 381                        /* Leaving quickack mode we deflate ATO. */
 382                        icsk->icsk_ack.ato   = TCP_ATO_MIN;
 383                } else
 384                        icsk->icsk_ack.quick -= pkts;
 385        }
 386}
 387
 388#define TCP_ECN_OK              1
 389#define TCP_ECN_QUEUE_CWR       2
 390#define TCP_ECN_DEMAND_CWR      4
 391#define TCP_ECN_SEEN            8
 392
 393enum tcp_tw_status {
 394        TCP_TW_SUCCESS = 0,
 395        TCP_TW_RST = 1,
 396        TCP_TW_ACK = 2,
 397        TCP_TW_SYN = 3
 398};
 399
 400
 401enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
 402                                              struct sk_buff *skb,
 403                                              const struct tcphdr *th);
 404struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
 405                           struct request_sock *req, struct request_sock **prev,
 406                           bool fastopen);
 407int tcp_child_process(struct sock *parent, struct sock *child,
 408                      struct sk_buff *skb);
 409void tcp_enter_loss(struct sock *sk);
 410void tcp_clear_retrans(struct tcp_sock *tp);
 411void tcp_update_metrics(struct sock *sk);
 412void tcp_init_metrics(struct sock *sk);
 413void tcp_metrics_init(void);
 414bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
 415                        bool paws_check, bool timestamps);
 416bool tcp_remember_stamp(struct sock *sk);
 417bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
 418void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
 419void tcp_disable_fack(struct tcp_sock *tp);
 420void tcp_close(struct sock *sk, long timeout);
 421void tcp_init_sock(struct sock *sk);
 422unsigned int tcp_poll(struct file *file, struct socket *sock,
 423                      struct poll_table_struct *wait);
 424int tcp_getsockopt(struct sock *sk, int level, int optname,
 425                   char __user *optval, int __user *optlen);
 426int tcp_setsockopt(struct sock *sk, int level, int optname,
 427                   char __user *optval, unsigned int optlen);
 428int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
 429                          char __user *optval, int __user *optlen);
 430int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
 431                          char __user *optval, unsigned int optlen);
 432void tcp_set_keepalive(struct sock *sk, int val);
 433void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req);
 434int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 435                size_t len, int nonblock, int flags, int *addr_len);
 436void tcp_parse_options(const struct sk_buff *skb,
 437                       struct tcp_options_received *opt_rx,
 438                       int estab, struct tcp_fastopen_cookie *foc);
 439const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
 440
 441/*
 442 *      TCP v4 functions exported for the inet6 API
 443 */
 444
 445void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
 446void tcp_v4_mtu_reduced(struct sock *sk);
 447int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
 448struct sock *tcp_create_openreq_child(struct sock *sk,
 449                                      struct request_sock *req,
 450                                      struct sk_buff *skb);
 451struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
 452                                  struct request_sock *req,
 453                                  struct dst_entry *dst);
 454int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
 455int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
 456int tcp_connect(struct sock *sk);
 457struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
 458                                struct request_sock *req,
 459                                struct tcp_fastopen_cookie *foc);
 460int tcp_disconnect(struct sock *sk, int flags);
 461
 462void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
 463int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
 464void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
 465
 466/* From syncookies.c */
 467int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
 468                      u32 cookie);
 469struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
 470#ifdef CONFIG_SYN_COOKIES
 471
 472/* Syncookies use a monotonic timer which increments every 60 seconds.
 473 * This counter is used both as a hash input and partially encoded into
 474 * the cookie value.  A cookie is only validated further if the delta
 475 * between the current counter value and the encoded one is less than this,
 476 * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
 477 * the counter advances immediately after a cookie is generated).
 478 */
 479#define MAX_SYNCOOKIE_AGE 2
 480
 481static inline u32 tcp_cookie_time(void)
 482{
 483        u64 val = get_jiffies_64();
 484
 485        do_div(val, 60 * HZ);
 486        return val;
 487}
 488
 489u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
 490                              u16 *mssp);
 491__u32 cookie_v4_init_sequence(struct sock *sk, const struct sk_buff *skb,
 492                              __u16 *mss);
 493__u32 cookie_init_timestamp(struct request_sock *req);
 494bool cookie_timestamp_decode(struct tcp_options_received *opt);
 495bool cookie_ecn_ok(const struct tcp_options_received *opt,
 496                   const struct net *net, const struct dst_entry *dst);
 497
 498/* From net/ipv6/syncookies.c */
 499int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
 500                      u32 cookie);
 501struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
 502
 503u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
 504                              const struct tcphdr *th, u16 *mssp);
 505__u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb,
 506                              __u16 *mss);
 507#endif
 508/* tcp_output.c */
 509
 510void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
 511                               int nonagle);
 512bool tcp_may_send_now(struct sock *sk);
 513int __tcp_retransmit_skb(struct sock *, struct sk_buff *);
 514int tcp_retransmit_skb(struct sock *, struct sk_buff *);
 515void tcp_retransmit_timer(struct sock *sk);
 516void tcp_xmit_retransmit_queue(struct sock *);
 517void tcp_simple_retransmit(struct sock *);
 518int tcp_trim_head(struct sock *, struct sk_buff *, u32);
 519int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
 520
 521void tcp_send_probe0(struct sock *);
 522void tcp_send_partial(struct sock *);
 523int tcp_write_wakeup(struct sock *);
 524void tcp_send_fin(struct sock *sk);
 525void tcp_send_active_reset(struct sock *sk, gfp_t priority);
 526int tcp_send_synack(struct sock *);
 527bool tcp_syn_flood_action(struct sock *sk, const struct sk_buff *skb,
 528                          const char *proto);
 529void tcp_push_one(struct sock *, unsigned int mss_now);
 530void tcp_send_ack(struct sock *sk);
 531void tcp_send_delayed_ack(struct sock *sk);
 532void tcp_send_loss_probe(struct sock *sk);
 533bool tcp_schedule_loss_probe(struct sock *sk);
 534
 535/* tcp_input.c */
 536void tcp_resume_early_retransmit(struct sock *sk);
 537void tcp_rearm_rto(struct sock *sk);
 538void tcp_reset(struct sock *sk);
 539
 540/* tcp_timer.c */
 541void tcp_init_xmit_timers(struct sock *);
 542static inline void tcp_clear_xmit_timers(struct sock *sk)
 543{
 544        inet_csk_clear_xmit_timers(sk);
 545}
 546
 547unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
 548unsigned int tcp_current_mss(struct sock *sk);
 549
 550/* Bound MSS / TSO packet size with the half of the window */
 551static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
 552{
 553        int cutoff;
 554
 555        /* When peer uses tiny windows, there is no use in packetizing
 556         * to sub-MSS pieces for the sake of SWS or making sure there
 557         * are enough packets in the pipe for fast recovery.
 558         *
 559         * On the other hand, for extremely large MSS devices, handling
 560         * smaller than MSS windows in this way does make sense.
 561         */
 562        if (tp->max_window >= 512)
 563                cutoff = (tp->max_window >> 1);
 564        else
 565                cutoff = tp->max_window;
 566
 567        if (cutoff && pktsize > cutoff)
 568                return max_t(int, cutoff, 68U - tp->tcp_header_len);
 569        else
 570                return pktsize;
 571}
 572
 573/* tcp.c */
 574void tcp_get_info(const struct sock *, struct tcp_info *);
 575
 576/* Read 'sendfile()'-style from a TCP socket */
 577typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
 578                                unsigned int, size_t);
 579int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
 580                  sk_read_actor_t recv_actor);
 581
 582void tcp_initialize_rcv_mss(struct sock *sk);
 583
 584int tcp_mtu_to_mss(struct sock *sk, int pmtu);
 585int tcp_mss_to_mtu(struct sock *sk, int mss);
 586void tcp_mtup_init(struct sock *sk);
 587void tcp_init_buffer_space(struct sock *sk);
 588
 589static inline void tcp_bound_rto(const struct sock *sk)
 590{
 591        if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
 592                inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
 593}
 594
 595static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
 596{
 597        return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
 598}
 599
 600static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
 601{
 602        tp->pred_flags = htonl((tp->tcp_header_len << 26) |
 603                               ntohl(TCP_FLAG_ACK) |
 604                               snd_wnd);
 605}
 606
 607static inline void tcp_fast_path_on(struct tcp_sock *tp)
 608{
 609        __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
 610}
 611
 612static inline void tcp_fast_path_check(struct sock *sk)
 613{
 614        struct tcp_sock *tp = tcp_sk(sk);
 615
 616        if (skb_queue_empty(&tp->out_of_order_queue) &&
 617            tp->rcv_wnd &&
 618            atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
 619            !tp->urg_data)
 620                tcp_fast_path_on(tp);
 621}
 622
 623/* Compute the actual rto_min value */
 624static inline u32 tcp_rto_min(struct sock *sk)
 625{
 626        const struct dst_entry *dst = __sk_dst_get(sk);
 627        u32 rto_min = TCP_RTO_MIN;
 628
 629        if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
 630                rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
 631        return rto_min;
 632}
 633
 634static inline u32 tcp_rto_min_us(struct sock *sk)
 635{
 636        return jiffies_to_usecs(tcp_rto_min(sk));
 637}
 638
 639/* Compute the actual receive window we are currently advertising.
 640 * Rcv_nxt can be after the window if our peer push more data
 641 * than the offered window.
 642 */
 643static inline u32 tcp_receive_window(const struct tcp_sock *tp)
 644{
 645        s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
 646
 647        if (win < 0)
 648                win = 0;
 649        return (u32) win;
 650}
 651
 652/* Choose a new window, without checks for shrinking, and without
 653 * scaling applied to the result.  The caller does these things
 654 * if necessary.  This is a "raw" window selection.
 655 */
 656u32 __tcp_select_window(struct sock *sk);
 657
 658void tcp_send_window_probe(struct sock *sk);
 659
 660/* TCP timestamps are only 32-bits, this causes a slight
 661 * complication on 64-bit systems since we store a snapshot
 662 * of jiffies in the buffer control blocks below.  We decided
 663 * to use only the low 32-bits of jiffies and hide the ugly
 664 * casts with the following macro.
 665 */
 666#define tcp_time_stamp          ((__u32)(jiffies))
 667
 668static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
 669{
 670        return skb->skb_mstamp.stamp_jiffies;
 671}
 672
 673
 674#define tcp_flag_byte(th) (((u_int8_t *)th)[13])
 675
 676#define TCPHDR_FIN 0x01
 677#define TCPHDR_SYN 0x02
 678#define TCPHDR_RST 0x04
 679#define TCPHDR_PSH 0x08
 680#define TCPHDR_ACK 0x10
 681#define TCPHDR_URG 0x20
 682#define TCPHDR_ECE 0x40
 683#define TCPHDR_CWR 0x80
 684
 685/* This is what the send packet queuing engine uses to pass
 686 * TCP per-packet control information to the transmission code.
 687 * We also store the host-order sequence numbers in here too.
 688 * This is 44 bytes if IPV6 is enabled.
 689 * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
 690 */
 691struct tcp_skb_cb {
 692        __u32           seq;            /* Starting sequence number     */
 693        __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
 694        union {
 695                /* Note : tcp_tw_isn is used in input path only
 696                 *        (isn chosen by tcp_timewait_state_process())
 697                 *
 698                 *        tcp_gso_segs is used in write queue only,
 699                 *        cf tcp_skb_pcount()
 700                 */
 701                __u32           tcp_tw_isn;
 702                __u32           tcp_gso_segs;
 703        };
 704        __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
 705
 706        __u8            sacked;         /* State flags for SACK/FACK.   */
 707#define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
 708#define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
 709#define TCPCB_LOST              0x04    /* SKB is lost                  */
 710#define TCPCB_TAGBITS           0x07    /* All tag bits                 */
 711#define TCPCB_REPAIRED          0x10    /* SKB repaired (no skb_mstamp) */
 712#define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
 713#define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
 714                                TCPCB_REPAIRED)
 715
 716        __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
 717        /* 1 byte hole */
 718        __u32           ack_seq;        /* Sequence number ACK'd        */
 719        union {
 720                struct inet_skb_parm    h4;
 721#if IS_ENABLED(CONFIG_IPV6)
 722                struct inet6_skb_parm   h6;
 723#endif
 724        } header;       /* For incoming frames          */
 725};
 726
 727#define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
 728
 729
 730#if IS_ENABLED(CONFIG_IPV6)
 731/* This is the variant of inet6_iif() that must be used by TCP,
 732 * as TCP moves IP6CB into a different location in skb->cb[]
 733 */
 734static inline int tcp_v6_iif(const struct sk_buff *skb)
 735{
 736        return TCP_SKB_CB(skb)->header.h6.iif;
 737}
 738#endif
 739
 740/* Due to TSO, an SKB can be composed of multiple actual
 741 * packets.  To keep these tracked properly, we use this.
 742 */
 743static inline int tcp_skb_pcount(const struct sk_buff *skb)
 744{
 745        return TCP_SKB_CB(skb)->tcp_gso_segs;
 746}
 747
 748static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
 749{
 750        TCP_SKB_CB(skb)->tcp_gso_segs = segs;
 751}
 752
 753static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
 754{
 755        TCP_SKB_CB(skb)->tcp_gso_segs += segs;
 756}
 757
 758/* This is valid iff tcp_skb_pcount() > 1. */
 759static inline int tcp_skb_mss(const struct sk_buff *skb)
 760{
 761        return skb_shinfo(skb)->gso_size;
 762}
 763
 764/* Events passed to congestion control interface */
 765enum tcp_ca_event {
 766        CA_EVENT_TX_START,      /* first transmit when no packets in flight */
 767        CA_EVENT_CWND_RESTART,  /* congestion window restart */
 768        CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
 769        CA_EVENT_LOSS,          /* loss timeout */
 770        CA_EVENT_ECN_NO_CE,     /* ECT set, but not CE marked */
 771        CA_EVENT_ECN_IS_CE,     /* received CE marked IP packet */
 772        CA_EVENT_DELAYED_ACK,   /* Delayed ack is sent */
 773        CA_EVENT_NON_DELAYED_ACK,
 774};
 775
 776/* Information about inbound ACK, passed to cong_ops->in_ack_event() */
 777enum tcp_ca_ack_event_flags {
 778        CA_ACK_SLOWPATH         = (1 << 0),     /* In slow path processing */
 779        CA_ACK_WIN_UPDATE       = (1 << 1),     /* ACK updated window */
 780        CA_ACK_ECE              = (1 << 2),     /* ECE bit is set on ack */
 781};
 782
 783/*
 784 * Interface for adding new TCP congestion control handlers
 785 */
 786#define TCP_CA_NAME_MAX 16
 787#define TCP_CA_MAX      128
 788#define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
 789
 790/* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
 791#define TCP_CONG_NON_RESTRICTED 0x1
 792/* Requires ECN/ECT set on all packets */
 793#define TCP_CONG_NEEDS_ECN      0x2
 794
 795struct tcp_congestion_ops {
 796        struct list_head        list;
 797        unsigned long flags;
 798
 799        /* initialize private data (optional) */
 800        void (*init)(struct sock *sk);
 801        /* cleanup private data  (optional) */
 802        void (*release)(struct sock *sk);
 803
 804        /* return slow start threshold (required) */
 805        u32 (*ssthresh)(struct sock *sk);
 806        /* do new cwnd calculation (required) */
 807        void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
 808        /* call before changing ca_state (optional) */
 809        void (*set_state)(struct sock *sk, u8 new_state);
 810        /* call when cwnd event occurs (optional) */
 811        void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
 812        /* call when ack arrives (optional) */
 813        void (*in_ack_event)(struct sock *sk, u32 flags);
 814        /* new value of cwnd after loss (optional) */
 815        u32  (*undo_cwnd)(struct sock *sk);
 816        /* hook for packet ack accounting (optional) */
 817        void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
 818        /* get info for inet_diag (optional) */
 819        void (*get_info)(struct sock *sk, u32 ext, struct sk_buff *skb);
 820
 821        char            name[TCP_CA_NAME_MAX];
 822        struct module   *owner;
 823};
 824
 825int tcp_register_congestion_control(struct tcp_congestion_ops *type);
 826void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
 827
 828void tcp_assign_congestion_control(struct sock *sk);
 829void tcp_init_congestion_control(struct sock *sk);
 830void tcp_cleanup_congestion_control(struct sock *sk);
 831int tcp_set_default_congestion_control(const char *name);
 832void tcp_get_default_congestion_control(char *name);
 833void tcp_get_available_congestion_control(char *buf, size_t len);
 834void tcp_get_allowed_congestion_control(char *buf, size_t len);
 835int tcp_set_allowed_congestion_control(char *allowed);
 836int tcp_set_congestion_control(struct sock *sk, const char *name);
 837u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
 838void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
 839
 840u32 tcp_reno_ssthresh(struct sock *sk);
 841void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
 842extern struct tcp_congestion_ops tcp_reno;
 843
 844static inline bool tcp_ca_needs_ecn(const struct sock *sk)
 845{
 846        const struct inet_connection_sock *icsk = inet_csk(sk);
 847
 848        return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
 849}
 850
 851static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
 852{
 853        struct inet_connection_sock *icsk = inet_csk(sk);
 854
 855        if (icsk->icsk_ca_ops->set_state)
 856                icsk->icsk_ca_ops->set_state(sk, ca_state);
 857        icsk->icsk_ca_state = ca_state;
 858}
 859
 860static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
 861{
 862        const struct inet_connection_sock *icsk = inet_csk(sk);
 863
 864        if (icsk->icsk_ca_ops->cwnd_event)
 865                icsk->icsk_ca_ops->cwnd_event(sk, event);
 866}
 867
 868/* These functions determine how the current flow behaves in respect of SACK
 869 * handling. SACK is negotiated with the peer, and therefore it can vary
 870 * between different flows.
 871 *
 872 * tcp_is_sack - SACK enabled
 873 * tcp_is_reno - No SACK
 874 * tcp_is_fack - FACK enabled, implies SACK enabled
 875 */
 876static inline int tcp_is_sack(const struct tcp_sock *tp)
 877{
 878        return tp->rx_opt.sack_ok;
 879}
 880
 881static inline bool tcp_is_reno(const struct tcp_sock *tp)
 882{
 883        return !tcp_is_sack(tp);
 884}
 885
 886static inline bool tcp_is_fack(const struct tcp_sock *tp)
 887{
 888        return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
 889}
 890
 891static inline void tcp_enable_fack(struct tcp_sock *tp)
 892{
 893        tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
 894}
 895
 896/* TCP early-retransmit (ER) is similar to but more conservative than
 897 * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
 898 */
 899static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
 900{
 901        tp->do_early_retrans = sysctl_tcp_early_retrans &&
 902                sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
 903                sysctl_tcp_reordering == 3;
 904}
 905
 906static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
 907{
 908        tp->do_early_retrans = 0;
 909}
 910
 911static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
 912{
 913        return tp->sacked_out + tp->lost_out;
 914}
 915
 916/* This determines how many packets are "in the network" to the best
 917 * of our knowledge.  In many cases it is conservative, but where
 918 * detailed information is available from the receiver (via SACK
 919 * blocks etc.) we can make more aggressive calculations.
 920 *
 921 * Use this for decisions involving congestion control, use just
 922 * tp->packets_out to determine if the send queue is empty or not.
 923 *
 924 * Read this equation as:
 925 *
 926 *      "Packets sent once on transmission queue" MINUS
 927 *      "Packets left network, but not honestly ACKed yet" PLUS
 928 *      "Packets fast retransmitted"
 929 */
 930static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
 931{
 932        return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
 933}
 934
 935#define TCP_INFINITE_SSTHRESH   0x7fffffff
 936
 937static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
 938{
 939        return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
 940}
 941
 942static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
 943{
 944        return (TCPF_CA_CWR | TCPF_CA_Recovery) &
 945               (1 << inet_csk(sk)->icsk_ca_state);
 946}
 947
 948/* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
 949 * The exception is cwnd reduction phase, when cwnd is decreasing towards
 950 * ssthresh.
 951 */
 952static inline __u32 tcp_current_ssthresh(const struct sock *sk)
 953{
 954        const struct tcp_sock *tp = tcp_sk(sk);
 955
 956        if (tcp_in_cwnd_reduction(sk))
 957                return tp->snd_ssthresh;
 958        else
 959                return max(tp->snd_ssthresh,
 960                           ((tp->snd_cwnd >> 1) +
 961                            (tp->snd_cwnd >> 2)));
 962}
 963
 964/* Use define here intentionally to get WARN_ON location shown at the caller */
 965#define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
 966
 967void tcp_enter_cwr(struct sock *sk);
 968__u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
 969
 970/* The maximum number of MSS of available cwnd for which TSO defers
 971 * sending if not using sysctl_tcp_tso_win_divisor.
 972 */
 973static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
 974{
 975        return 3;
 976}
 977
 978/* Slow start with delack produces 3 packets of burst, so that
 979 * it is safe "de facto".  This will be the default - same as
 980 * the default reordering threshold - but if reordering increases,
 981 * we must be able to allow cwnd to burst at least this much in order
 982 * to not pull it back when holes are filled.
 983 */
 984static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
 985{
 986        return tp->reordering;
 987}
 988
 989/* Returns end sequence number of the receiver's advertised window */
 990static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
 991{
 992        return tp->snd_una + tp->snd_wnd;
 993}
 994
 995/* We follow the spirit of RFC2861 to validate cwnd but implement a more
 996 * flexible approach. The RFC suggests cwnd should not be raised unless
 997 * it was fully used previously. And that's exactly what we do in
 998 * congestion avoidance mode. But in slow start we allow cwnd to grow
 999 * as long as the application has used half the cwnd.
1000 * Example :
1001 *    cwnd is 10 (IW10), but application sends 9 frames.
1002 *    We allow cwnd to reach 18 when all frames are ACKed.
1003 * This check is safe because it's as aggressive as slow start which already
1004 * risks 100% overshoot. The advantage is that we discourage application to
1005 * either send more filler packets or data to artificially blow up the cwnd
1006 * usage, and allow application-limited process to probe bw more aggressively.
1007 */
1008static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1009{
1010        const struct tcp_sock *tp = tcp_sk(sk);
1011
1012        /* If in slow start, ensure cwnd grows to twice what was ACKed. */
1013        if (tp->snd_cwnd <= tp->snd_ssthresh)
1014                return tp->snd_cwnd < 2 * tp->max_packets_out;
1015
1016        return tp->is_cwnd_limited;
1017}
1018
1019static inline void tcp_check_probe_timer(struct sock *sk)
1020{
1021        const struct tcp_sock *tp = tcp_sk(sk);
1022        const struct inet_connection_sock *icsk = inet_csk(sk);
1023
1024        if (!tp->packets_out && !icsk->icsk_pending)
1025                inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1026                                          icsk->icsk_rto, TCP_RTO_MAX);
1027}
1028
1029static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1030{
1031        tp->snd_wl1 = seq;
1032}
1033
1034static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1035{
1036        tp->snd_wl1 = seq;
1037}
1038
1039/*
1040 * Calculate(/check) TCP checksum
1041 */
1042static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1043                                   __be32 daddr, __wsum base)
1044{
1045        return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1046}
1047
1048static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1049{
1050        return __skb_checksum_complete(skb);
1051}
1052
1053static inline bool tcp_checksum_complete(struct sk_buff *skb)
1054{
1055        return !skb_csum_unnecessary(skb) &&
1056                __tcp_checksum_complete(skb);
1057}
1058
1059/* Prequeue for VJ style copy to user, combined with checksumming. */
1060
1061static inline void tcp_prequeue_init(struct tcp_sock *tp)
1062{
1063        tp->ucopy.task = NULL;
1064        tp->ucopy.len = 0;
1065        tp->ucopy.memory = 0;
1066        skb_queue_head_init(&tp->ucopy.prequeue);
1067}
1068
1069bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1070
1071#undef STATE_TRACE
1072
1073#ifdef STATE_TRACE
1074static const char *statename[]={
1075        "Unused","Established","Syn Sent","Syn Recv",
1076        "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1077        "Close Wait","Last ACK","Listen","Closing"
1078};
1079#endif
1080void tcp_set_state(struct sock *sk, int state);
1081
1082void tcp_done(struct sock *sk);
1083
1084static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1085{
1086        rx_opt->dsack = 0;
1087        rx_opt->num_sacks = 0;
1088}
1089
1090u32 tcp_default_init_rwnd(u32 mss);
1091
1092/* Determine a window scaling and initial window to offer. */
1093void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1094                               __u32 *window_clamp, int wscale_ok,
1095                               __u8 *rcv_wscale, __u32 init_rcv_wnd);
1096
1097static inline int tcp_win_from_space(int space)
1098{
1099        return sysctl_tcp_adv_win_scale<=0 ?
1100                (space>>(-sysctl_tcp_adv_win_scale)) :
1101                space - (space>>sysctl_tcp_adv_win_scale);
1102}
1103
1104/* Note: caller must be prepared to deal with negative returns */
1105static inline int tcp_space(const struct sock *sk)
1106{
1107        return tcp_win_from_space(sk->sk_rcvbuf -
1108                                  atomic_read(&sk->sk_rmem_alloc));
1109}
1110
1111static inline int tcp_full_space(const struct sock *sk)
1112{
1113        return tcp_win_from_space(sk->sk_rcvbuf);
1114}
1115
1116static inline void tcp_openreq_init(struct request_sock *req,
1117                                    struct tcp_options_received *rx_opt,
1118                                    struct sk_buff *skb, struct sock *sk)
1119{
1120        struct inet_request_sock *ireq = inet_rsk(req);
1121
1122        req->rcv_wnd = 0;               /* So that tcp_send_synack() knows! */
1123        req->cookie_ts = 0;
1124        tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
1125        tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
1126        tcp_rsk(req)->snt_synack = tcp_time_stamp;
1127        req->mss = rx_opt->mss_clamp;
1128        req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
1129        ireq->tstamp_ok = rx_opt->tstamp_ok;
1130        ireq->sack_ok = rx_opt->sack_ok;
1131        ireq->snd_wscale = rx_opt->snd_wscale;
1132        ireq->wscale_ok = rx_opt->wscale_ok;
1133        ireq->acked = 0;
1134        ireq->ecn_ok = 0;
1135        ireq->ir_rmt_port = tcp_hdr(skb)->source;
1136        ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
1137        ireq->ir_mark = inet_request_mark(sk, skb);
1138}
1139
1140extern void tcp_openreq_init_rwin(struct request_sock *req,
1141                                  struct sock *sk, struct dst_entry *dst);
1142
1143void tcp_enter_memory_pressure(struct sock *sk);
1144
1145static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1146{
1147        return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1148}
1149
1150static inline int keepalive_time_when(const struct tcp_sock *tp)
1151{
1152        return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1153}
1154
1155static inline int keepalive_probes(const struct tcp_sock *tp)
1156{
1157        return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1158}
1159
1160static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1161{
1162        const struct inet_connection_sock *icsk = &tp->inet_conn;
1163
1164        return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1165                          tcp_time_stamp - tp->rcv_tstamp);
1166}
1167
1168static inline int tcp_fin_time(const struct sock *sk)
1169{
1170        int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1171        const int rto = inet_csk(sk)->icsk_rto;
1172
1173        if (fin_timeout < (rto << 2) - (rto >> 1))
1174                fin_timeout = (rto << 2) - (rto >> 1);
1175
1176        return fin_timeout;
1177}
1178
1179static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1180                                  int paws_win)
1181{
1182        if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1183                return true;
1184        if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1185                return true;
1186        /*
1187         * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1188         * then following tcp messages have valid values. Ignore 0 value,
1189         * or else 'negative' tsval might forbid us to accept their packets.
1190         */
1191        if (!rx_opt->ts_recent)
1192                return true;
1193        return false;
1194}
1195
1196static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1197                                   int rst)
1198{
1199        if (tcp_paws_check(rx_opt, 0))
1200                return false;
1201
1202        /* RST segments are not recommended to carry timestamp,
1203           and, if they do, it is recommended to ignore PAWS because
1204           "their cleanup function should take precedence over timestamps."
1205           Certainly, it is mistake. It is necessary to understand the reasons
1206           of this constraint to relax it: if peer reboots, clock may go
1207           out-of-sync and half-open connections will not be reset.
1208           Actually, the problem would be not existing if all
1209           the implementations followed draft about maintaining clock
1210           via reboots. Linux-2.2 DOES NOT!
1211
1212           However, we can relax time bounds for RST segments to MSL.
1213         */
1214        if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1215                return false;
1216        return true;
1217}
1218
1219static inline void tcp_mib_init(struct net *net)
1220{
1221        /* See RFC 2012 */
1222        TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1223        TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1224        TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1225        TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1226}
1227
1228/* from STCP */
1229static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1230{
1231        tp->lost_skb_hint = NULL;
1232}
1233
1234static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1235{
1236        tcp_clear_retrans_hints_partial(tp);
1237        tp->retransmit_skb_hint = NULL;
1238}
1239
1240/* MD5 Signature */
1241struct crypto_hash;
1242
1243union tcp_md5_addr {
1244        struct in_addr  a4;
1245#if IS_ENABLED(CONFIG_IPV6)
1246        struct in6_addr a6;
1247#endif
1248};
1249
1250/* - key database */
1251struct tcp_md5sig_key {
1252        struct hlist_node       node;
1253        u8                      keylen;
1254        u8                      family; /* AF_INET or AF_INET6 */
1255        union tcp_md5_addr      addr;
1256        u8                      key[TCP_MD5SIG_MAXKEYLEN];
1257        struct rcu_head         rcu;
1258};
1259
1260/* - sock block */
1261struct tcp_md5sig_info {
1262        struct hlist_head       head;
1263        struct rcu_head         rcu;
1264};
1265
1266/* - pseudo header */
1267struct tcp4_pseudohdr {
1268        __be32          saddr;
1269        __be32          daddr;
1270        __u8            pad;
1271        __u8            protocol;
1272        __be16          len;
1273};
1274
1275struct tcp6_pseudohdr {
1276        struct in6_addr saddr;
1277        struct in6_addr daddr;
1278        __be32          len;
1279        __be32          protocol;       /* including padding */
1280};
1281
1282union tcp_md5sum_block {
1283        struct tcp4_pseudohdr ip4;
1284#if IS_ENABLED(CONFIG_IPV6)
1285        struct tcp6_pseudohdr ip6;
1286#endif
1287};
1288
1289/* - pool: digest algorithm, hash description and scratch buffer */
1290struct tcp_md5sig_pool {
1291        struct hash_desc        md5_desc;
1292        union tcp_md5sum_block  md5_blk;
1293};
1294
1295/* - functions */
1296int tcp_v4_md5_hash_skb(char *md5_hash, struct tcp_md5sig_key *key,
1297                        const struct sock *sk, const struct request_sock *req,
1298                        const struct sk_buff *skb);
1299int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1300                   int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1301int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1302                   int family);
1303struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
1304                                         struct sock *addr_sk);
1305
1306#ifdef CONFIG_TCP_MD5SIG
1307struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1308                                         const union tcp_md5_addr *addr,
1309                                         int family);
1310#define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1311#else
1312static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1313                                         const union tcp_md5_addr *addr,
1314                                         int family)
1315{
1316        return NULL;
1317}
1318#define tcp_twsk_md5_key(twsk)  NULL
1319#endif
1320
1321bool tcp_alloc_md5sig_pool(void);
1322
1323struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1324static inline void tcp_put_md5sig_pool(void)
1325{
1326        local_bh_enable();
1327}
1328
1329int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1330int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1331                          unsigned int header_len);
1332int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1333                     const struct tcp_md5sig_key *key);
1334
1335/* From tcp_fastopen.c */
1336void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1337                            struct tcp_fastopen_cookie *cookie, int *syn_loss,
1338                            unsigned long *last_syn_loss);
1339void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1340                            struct tcp_fastopen_cookie *cookie, bool syn_lost);
1341struct tcp_fastopen_request {
1342        /* Fast Open cookie. Size 0 means a cookie request */
1343        struct tcp_fastopen_cookie      cookie;
1344        struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1345        size_t                          size;
1346        int                             copied; /* queued in tcp_connect() */
1347};
1348void tcp_free_fastopen_req(struct tcp_sock *tp);
1349
1350extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1351int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1352bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1353                      struct request_sock *req,
1354                      struct tcp_fastopen_cookie *foc,
1355                      struct dst_entry *dst);
1356void tcp_fastopen_init_key_once(bool publish);
1357#define TCP_FASTOPEN_KEY_LENGTH 16
1358
1359/* Fastopen key context */
1360struct tcp_fastopen_context {
1361        struct crypto_cipher    *tfm;
1362        __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1363        struct rcu_head         rcu;
1364};
1365
1366/* write queue abstraction */
1367static inline void tcp_write_queue_purge(struct sock *sk)
1368{
1369        struct sk_buff *skb;
1370
1371        while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1372                sk_wmem_free_skb(sk, skb);
1373        sk_mem_reclaim(sk);
1374        tcp_clear_all_retrans_hints(tcp_sk(sk));
1375}
1376
1377static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1378{
1379        return skb_peek(&sk->sk_write_queue);
1380}
1381
1382static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1383{
1384        return skb_peek_tail(&sk->sk_write_queue);
1385}
1386
1387static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1388                                                   const struct sk_buff *skb)
1389{
1390        return skb_queue_next(&sk->sk_write_queue, skb);
1391}
1392
1393static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1394                                                   const struct sk_buff *skb)
1395{
1396        return skb_queue_prev(&sk->sk_write_queue, skb);
1397}
1398
1399#define tcp_for_write_queue(skb, sk)                                    \
1400        skb_queue_walk(&(sk)->sk_write_queue, skb)
1401
1402#define tcp_for_write_queue_from(skb, sk)                               \
1403        skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1404
1405#define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1406        skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1407
1408static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1409{
1410        return sk->sk_send_head;
1411}
1412
1413static inline bool tcp_skb_is_last(const struct sock *sk,
1414                                   const struct sk_buff *skb)
1415{
1416        return skb_queue_is_last(&sk->sk_write_queue, skb);
1417}
1418
1419static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1420{
1421        if (tcp_skb_is_last(sk, skb))
1422                sk->sk_send_head = NULL;
1423        else
1424                sk->sk_send_head = tcp_write_queue_next(sk, skb);
1425}
1426
1427static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1428{
1429        if (sk->sk_send_head == skb_unlinked)
1430                sk->sk_send_head = NULL;
1431}
1432
1433static inline void tcp_init_send_head(struct sock *sk)
1434{
1435        sk->sk_send_head = NULL;
1436}
1437
1438static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1439{
1440        __skb_queue_tail(&sk->sk_write_queue, skb);
1441}
1442
1443static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1444{
1445        __tcp_add_write_queue_tail(sk, skb);
1446
1447        /* Queue it, remembering where we must start sending. */
1448        if (sk->sk_send_head == NULL) {
1449                sk->sk_send_head = skb;
1450
1451                if (tcp_sk(sk)->highest_sack == NULL)
1452                        tcp_sk(sk)->highest_sack = skb;
1453        }
1454}
1455
1456static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1457{
1458        __skb_queue_head(&sk->sk_write_queue, skb);
1459}
1460
1461/* Insert buff after skb on the write queue of sk.  */
1462static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1463                                                struct sk_buff *buff,
1464                                                struct sock *sk)
1465{
1466        __skb_queue_after(&sk->sk_write_queue, skb, buff);
1467}
1468
1469/* Insert new before skb on the write queue of sk.  */
1470static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1471                                                  struct sk_buff *skb,
1472                                                  struct sock *sk)
1473{
1474        __skb_queue_before(&sk->sk_write_queue, skb, new);
1475
1476        if (sk->sk_send_head == skb)
1477                sk->sk_send_head = new;
1478}
1479
1480static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1481{
1482        __skb_unlink(skb, &sk->sk_write_queue);
1483}
1484
1485static inline bool tcp_write_queue_empty(struct sock *sk)
1486{
1487        return skb_queue_empty(&sk->sk_write_queue);
1488}
1489
1490static inline void tcp_push_pending_frames(struct sock *sk)
1491{
1492        if (tcp_send_head(sk)) {
1493                struct tcp_sock *tp = tcp_sk(sk);
1494
1495                __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1496        }
1497}
1498
1499/* Start sequence of the skb just after the highest skb with SACKed
1500 * bit, valid only if sacked_out > 0 or when the caller has ensured
1501 * validity by itself.
1502 */
1503static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1504{
1505        if (!tp->sacked_out)
1506                return tp->snd_una;
1507
1508        if (tp->highest_sack == NULL)
1509                return tp->snd_nxt;
1510
1511        return TCP_SKB_CB(tp->highest_sack)->seq;
1512}
1513
1514static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1515{
1516        tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1517                                                tcp_write_queue_next(sk, skb);
1518}
1519
1520static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1521{
1522        return tcp_sk(sk)->highest_sack;
1523}
1524
1525static inline void tcp_highest_sack_reset(struct sock *sk)
1526{
1527        tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1528}
1529
1530/* Called when old skb is about to be deleted (to be combined with new skb) */
1531static inline void tcp_highest_sack_combine(struct sock *sk,
1532                                            struct sk_buff *old,
1533                                            struct sk_buff *new)
1534{
1535        if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1536                tcp_sk(sk)->highest_sack = new;
1537}
1538
1539/* Determines whether this is a thin stream (which may suffer from
1540 * increased latency). Used to trigger latency-reducing mechanisms.
1541 */
1542static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1543{
1544        return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1545}
1546
1547/* /proc */
1548enum tcp_seq_states {
1549        TCP_SEQ_STATE_LISTENING,
1550        TCP_SEQ_STATE_OPENREQ,
1551        TCP_SEQ_STATE_ESTABLISHED,
1552};
1553
1554int tcp_seq_open(struct inode *inode, struct file *file);
1555
1556struct tcp_seq_afinfo {
1557        char                            *name;
1558        sa_family_t                     family;
1559        const struct file_operations    *seq_fops;
1560        struct seq_operations           seq_ops;
1561};
1562
1563struct tcp_iter_state {
1564        struct seq_net_private  p;
1565        sa_family_t             family;
1566        enum tcp_seq_states     state;
1567        struct sock             *syn_wait_sk;
1568        int                     bucket, offset, sbucket, num;
1569        kuid_t                  uid;
1570        loff_t                  last_pos;
1571};
1572
1573int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1574void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1575
1576extern struct request_sock_ops tcp_request_sock_ops;
1577extern struct request_sock_ops tcp6_request_sock_ops;
1578
1579void tcp_v4_destroy_sock(struct sock *sk);
1580
1581struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1582                                netdev_features_t features);
1583struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1584int tcp_gro_complete(struct sk_buff *skb);
1585
1586void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1587
1588static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1589{
1590        return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1591}
1592
1593static inline bool tcp_stream_memory_free(const struct sock *sk)
1594{
1595        const struct tcp_sock *tp = tcp_sk(sk);
1596        u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1597
1598        return notsent_bytes < tcp_notsent_lowat(tp);
1599}
1600
1601#ifdef CONFIG_PROC_FS
1602int tcp4_proc_init(void);
1603void tcp4_proc_exit(void);
1604#endif
1605
1606int tcp_rtx_synack(struct sock *sk, struct request_sock *req);
1607int tcp_conn_request(struct request_sock_ops *rsk_ops,
1608                     const struct tcp_request_sock_ops *af_ops,
1609                     struct sock *sk, struct sk_buff *skb);
1610
1611/* TCP af-specific functions */
1612struct tcp_sock_af_ops {
1613#ifdef CONFIG_TCP_MD5SIG
1614        struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1615                                                struct sock *addr_sk);
1616        int                     (*calc_md5_hash) (char *location,
1617                                                  struct tcp_md5sig_key *md5,
1618                                                  const struct sock *sk,
1619                                                  const struct request_sock *req,
1620                                                  const struct sk_buff *skb);
1621        int                     (*md5_parse) (struct sock *sk,
1622                                              char __user *optval,
1623                                              int optlen);
1624#endif
1625};
1626
1627struct tcp_request_sock_ops {
1628        u16 mss_clamp;
1629#ifdef CONFIG_TCP_MD5SIG
1630        struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1631                                                struct request_sock *req);
1632        int                     (*calc_md5_hash) (char *location,
1633                                                  struct tcp_md5sig_key *md5,
1634                                                  const struct sock *sk,
1635                                                  const struct request_sock *req,
1636                                                  const struct sk_buff *skb);
1637#endif
1638        void (*init_req)(struct request_sock *req, struct sock *sk,
1639                         struct sk_buff *skb);
1640#ifdef CONFIG_SYN_COOKIES
1641        __u32 (*cookie_init_seq)(struct sock *sk, const struct sk_buff *skb,
1642                                 __u16 *mss);
1643#endif
1644        struct dst_entry *(*route_req)(struct sock *sk, struct flowi *fl,
1645                                       const struct request_sock *req,
1646                                       bool *strict);
1647        __u32 (*init_seq)(const struct sk_buff *skb);
1648        int (*send_synack)(struct sock *sk, struct dst_entry *dst,
1649                           struct flowi *fl, struct request_sock *req,
1650                           u16 queue_mapping, struct tcp_fastopen_cookie *foc);
1651        void (*queue_hash_add)(struct sock *sk, struct request_sock *req,
1652                               const unsigned long timeout);
1653};
1654
1655#ifdef CONFIG_SYN_COOKIES
1656static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1657                                         struct sock *sk, struct sk_buff *skb,
1658                                         __u16 *mss)
1659{
1660        return ops->cookie_init_seq(sk, skb, mss);
1661}
1662#else
1663static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1664                                         struct sock *sk, struct sk_buff *skb,
1665                                         __u16 *mss)
1666{
1667        return 0;
1668}
1669#endif
1670
1671int tcpv4_offload_init(void);
1672
1673void tcp_v4_init(void);
1674void tcp_init(void);
1675
1676/*
1677 * Save and compile IPv4 options, return a pointer to it
1678 */
1679static inline struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb)
1680{
1681        const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1682        struct ip_options_rcu *dopt = NULL;
1683
1684        if (opt->optlen) {
1685                int opt_size = sizeof(*dopt) + opt->optlen;
1686
1687                dopt = kmalloc(opt_size, GFP_ATOMIC);
1688                if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) {
1689                        kfree(dopt);
1690                        dopt = NULL;
1691                }
1692        }
1693        return dopt;
1694}
1695
1696#endif  /* _TCP_H */
1697
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