include/linux/tcp.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   4  *              operating system.  INET is implemented using the  BSD Socket
   5  *              interface as the means of communication with the user level.
   6  *
   7  *              Definitions for the TCP protocol.
   8  *
   9  * Version:     @(#)tcp.h       1.0.2   04/28/93
  10  *
  11  * Author:      Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  12  */
  13 #ifndef _LINUX_TCP_H
  14 #define _LINUX_TCP_H
  15
  16
  17 #include <linux/skbuff.h>
  18 #include <linux/win_minmax.h>
  19 #include <net/sock.h>
  20 #include <net/inet_connection_sock.h>
  21 #include <net/inet_timewait_sock.h>
  22 #include <uapi/linux/tcp.h>
  23
  24 static inline struct tcphdr *tcp_hdr(const struct sk_buff *skb)
  25 {
  26         return (struct tcphdr *)skb_transport_header(skb);
  27 }
  28
  29 static inline unsigned int __tcp_hdrlen(const struct tcphdr *th)
  30 {
  31         return th->doff * 4;
  32 }
  33
  34 static inline unsigned int tcp_hdrlen(const struct sk_buff *skb)
  35 {
  36         return __tcp_hdrlen(tcp_hdr(skb));
  37 }
  38
  39 static inline struct tcphdr *inner_tcp_hdr(const struct sk_buff *skb)
  40 {
  41         return (struct tcphdr *)skb_inner_transport_header(skb);
  42 }
  43
  44 static inline unsigned int inner_tcp_hdrlen(const struct sk_buff *skb)
  45 {
  46         return inner_tcp_hdr(skb)->doff * 4;
  47 }
  48
  49 static inline unsigned int tcp_optlen(const struct sk_buff *skb)
  50 {
  51         return (tcp_hdr(skb)->doff - 5) * 4;
  52 }
  53
  54 /* TCP Fast Open */
  55 #define TCP_FASTOPEN_COOKIE_MIN 4       /* Min Fast Open Cookie size in bytes */
  56 #define TCP_FASTOPEN_COOKIE_MAX 16      /* Max Fast Open Cookie size in bytes */
  57 #define TCP_FASTOPEN_COOKIE_SIZE 8      /* the size employed by this impl. */
  58
  59 /* TCP Fast Open Cookie as stored in memory */
  60 struct tcp_fastopen_cookie {
  61         __le64  val[DIV_ROUND_UP(TCP_FASTOPEN_COOKIE_MAX, sizeof(u64))];
  62         s8      len;
  63         bool    exp;    /* In RFC6994 experimental option format */
  64 };
  65
  66 /* This defines a selective acknowledgement block. */
  67 struct tcp_sack_block_wire {
  68         __be32  start_seq;
  69         __be32  end_seq;
  70 };
  71
  72 struct tcp_sack_block {
  73         u32     start_seq;
  74         u32     end_seq;
  75 };
  76
  77 /*These are used to set the sack_ok field in struct tcp_options_received */
  78 #define TCP_SACK_SEEN     (1 << 0)   /*1 = peer is SACK capable, */
  79 #define TCP_DSACK_SEEN    (1 << 2)   /*1 = DSACK was received from peer*/
  80
  81 struct tcp_options_received {
  82 /*      PAWS/RTTM data  */
  83         int     ts_recent_stamp;/* Time we stored ts_recent (for aging) */
  84         u32     ts_recent;      /* Time stamp to echo next              */
  85         u32     rcv_tsval;      /* Time stamp value                     */
  86         u32     rcv_tsecr;      /* Time stamp echo reply                */
  87         u16     saw_tstamp : 1, /* Saw TIMESTAMP on last packet         */
  88                 tstamp_ok : 1,  /* TIMESTAMP seen on SYN packet         */
  89                 dsack : 1,      /* D-SACK is scheduled                  */
  90                 wscale_ok : 1,  /* Wscale seen on SYN packet            */
  91                 sack_ok : 3,    /* SACK seen on SYN packet              */
  92                 smc_ok : 1,     /* SMC seen on SYN packet               */
  93                 snd_wscale : 4, /* Window scaling received from sender  */
  94                 rcv_wscale : 4; /* Window scaling to send to receiver   */
  95         u8      num_sacks;      /* Number of SACK blocks                */
  96         u16     user_mss;       /* mss requested by user in ioctl       */
  97         u16     mss_clamp;      /* Maximal mss, negotiated at connection setup */
  98 };
  99
 100 static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
 101 {
 102         rx_opt->tstamp_ok = rx_opt->sack_ok = 0;
 103         rx_opt->wscale_ok = rx_opt->snd_wscale = 0;
 104 #if IS_ENABLED(CONFIG_SMC)
 105         rx_opt->smc_ok = 0;
 106 #endif
 107 }
 108
 109 /* This is the max number of SACKS that we'll generate and process. It's safe
 110  * to increase this, although since:
 111  *   size = TCPOLEN_SACK_BASE_ALIGNED (4) + n * TCPOLEN_SACK_PERBLOCK (8)
 112  * only four options will fit in a standard TCP header */
 113 #define TCP_NUM_SACKS 4
 114
 115 struct tcp_request_sock_ops;
 116
 117 struct tcp_request_sock {
 118         struct inet_request_sock        req;
 119         const struct tcp_request_sock_ops *af_specific;
 120         u64                             snt_synack; /* first SYNACK sent time */
 121         bool                            tfo_listener;
 122         bool                            is_mptcp;
 123         u32                             txhash;
 124         u32                             rcv_isn;
 125         u32                             snt_isn;
 126         u32                             ts_off;
 127         u32                             last_oow_ack_time; /* last SYNACK */
 128         u32                             rcv_nxt; /* the ack # by SYNACK. For
 129                                                   * FastOpen it's the seq#
 130                                                   * after data-in-SYN.
 131                                                   */
 132 };
 133
 134 static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)
 135 {
 136         return (struct tcp_request_sock *)req;
 137 }
 138
 139 struct tcp_sock {
 140         /* inet_connection_sock has to be the first member of tcp_sock */
 141         struct inet_connection_sock     inet_conn;
 142         u16     tcp_header_len; /* Bytes of tcp header to send          */
 143         u16     gso_segs;       /* Max number of segs per GSO packet    */
 144
 145 /*
 146  *      Header prediction flags
 147  *      0x5?10 << 16 + snd_wnd in net byte order
 148  */
 149         __be32  pred_flags;
 150
 151 /*
 152  *      RFC793 variables by their proper names. This means you can
 153  *      read the code and the spec side by side (and laugh ...)
 154  *      See RFC793 and RFC1122. The RFC writes these in capitals.
 155  */
 156         u64     bytes_received; /* RFC4898 tcpEStatsAppHCThruOctetsReceived
 157                                  * sum(delta(rcv_nxt)), or how many bytes
 158                                  * were acked.
 159                                  */
 160         u32     segs_in;        /* RFC4898 tcpEStatsPerfSegsIn
 161                                  * total number of segments in.
 162                                  */
 163         u32     data_segs_in;   /* RFC4898 tcpEStatsPerfDataSegsIn
 164                                  * total number of data segments in.
 165                                  */
 166         u32     rcv_nxt;        /* What we want to receive next         */
 167         u32     copied_seq;     /* Head of yet unread data              */
 168         u32     rcv_wup;        /* rcv_nxt on last window update sent   */
 169         u32     snd_nxt;        /* Next sequence we send                */
 170         u32     segs_out;       /* RFC4898 tcpEStatsPerfSegsOut
 171                                  * The total number of segments sent.
 172                                  */
 173         u32     data_segs_out;  /* RFC4898 tcpEStatsPerfDataSegsOut
 174                                  * total number of data segments sent.
 175                                  */
 176         u64     bytes_sent;     /* RFC4898 tcpEStatsPerfHCDataOctetsOut
 177                                  * total number of data bytes sent.
 178                                  */
 179         u64     bytes_acked;    /* RFC4898 tcpEStatsAppHCThruOctetsAcked
 180                                  * sum(delta(snd_una)), or how many bytes
 181                                  * were acked.
 182                                  */
 183         u32     dsack_dups;     /* RFC4898 tcpEStatsStackDSACKDups
 184                                  * total number of DSACK blocks received
 185                                  */
 186         u32     snd_una;        /* First byte we want an ack for        */
 187         u32     snd_sml;        /* Last byte of the most recently transmitted small packet */
 188         u32     rcv_tstamp;     /* timestamp of last received ACK (for keepalives) */
 189         u32     lsndtime;       /* timestamp of last sent data packet (for restart window) */
 190         u32     last_oow_ack_time;  /* timestamp of last out-of-window ACK */
 191         u32     compressed_ack_rcv_nxt;
 192
 193         u32     tsoffset;       /* timestamp offset */
 194
 195         struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
 196         struct list_head tsorted_sent_queue; /* time-sorted sent but un-SACKed skbs */
 197
 198         u32     snd_wl1;        /* Sequence for window update           */
 199         u32     snd_wnd;        /* The window we expect to receive      */
 200         u32     max_window;     /* Maximal window ever seen from peer   */
 201         u32     mss_cache;      /* Cached effective mss, not including SACKS */
 202
 203         u32     window_clamp;   /* Maximal window to advertise          */
 204         u32     rcv_ssthresh;   /* Current window clamp                 */
 205
 206         /* Information of the most recently (s)acked skb */
 207         struct tcp_rack {
 208                 u64 mstamp; /* (Re)sent time of the skb */
 209                 u32 rtt_us;  /* Associated RTT */
 210                 u32 end_seq; /* Ending TCP sequence of the skb */
 211                 u32 last_delivered; /* tp->delivered at last reo_wnd adj */
 212                 u8 reo_wnd_steps;   /* Allowed reordering window */
 213 #define TCP_RACK_RECOVERY_THRESH 16
 214                 u8 reo_wnd_persist:5, /* No. of recovery since last adj */
 215                    dsack_seen:1, /* Whether DSACK seen after last adj */
 216                    advanced:1;   /* mstamp advanced since last lost marking */
 217         } rack;
 218         u16     advmss;         /* Advertised MSS                       */
 219         u8      compressed_ack;
 220         u32     chrono_start;   /* Start time in jiffies of a TCP chrono */
 221         u32     chrono_stat[3]; /* Time in jiffies for chrono_stat stats */
 222         u8      chrono_type:2,  /* current chronograph type */
 223                 rate_app_limited:1,  /* rate_{delivered,interval_us} limited? */
 224                 fastopen_connect:1, /* FASTOPEN_CONNECT sockopt */
 225                 fastopen_no_cookie:1, /* Allow send/recv SYN+data without a cookie */
 226                 is_sack_reneg:1,    /* in recovery from loss with SACK reneg? */
 227                 fastopen_client_fail:2; /* reason why fastopen failed */
 228         u8      nonagle     : 4,/* Disable Nagle algorithm?             */
 229                 thin_lto    : 1,/* Use linear timeouts for thin streams */
 230                 recvmsg_inq : 1,/* Indicate # of bytes in queue upon recvmsg */
 231                 repair      : 1,
 232                 frto        : 1;/* F-RTO (RFC5682) activated in CA_Loss */
 233         u8      repair_queue;
 234         u8      syn_data:1,     /* SYN includes data */
 235                 syn_fastopen:1, /* SYN includes Fast Open option */
 236                 syn_fastopen_exp:1,/* SYN includes Fast Open exp. option */
 237                 syn_fastopen_ch:1, /* Active TFO re-enabling probe */
 238                 syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
 239                 save_syn:1,     /* Save headers of SYN packet */
 240                 is_cwnd_limited:1,/* forward progress limited by snd_cwnd? */
 241                 syn_smc:1;      /* SYN includes SMC */
 242         u32     tlp_high_seq;   /* snd_nxt at the time of TLP retransmit. */
 243
 244         u32     tcp_tx_delay;   /* delay (in usec) added to TX packets */
 245         u64     tcp_wstamp_ns;  /* departure time for next sent data packet */
 246         u64     tcp_clock_cache; /* cache last tcp_clock_ns() (see tcp_mstamp_refresh()) */
 247
 248 /* RTT measurement */
 249         u64     tcp_mstamp;     /* most recent packet received/sent */
 250         u32     srtt_us;        /* smoothed round trip time << 3 in usecs */
 251         u32     mdev_us;        /* medium deviation                     */
 252         u32     mdev_max_us;    /* maximal mdev for the last rtt period */
 253         u32     rttvar_us;      /* smoothed mdev_max                    */
 254         u32     rtt_seq;        /* sequence number to update rttvar     */
 255         struct  minmax rtt_min;
 256
 257         u32     packets_out;    /* Packets which are "in flight"        */
 258         u32     retrans_out;    /* Retransmitted packets out            */
 259         u32     max_packets_out;  /* max packets_out in last window */
 260         u32     max_packets_seq;  /* right edge of max_packets_out flight */
 261
 262         u16     urg_data;       /* Saved octet of OOB data and control flags */
 263         u8      ecn_flags;      /* ECN status bits.                     */
 264         u8      keepalive_probes; /* num of allowed keep alive probes   */
 265         u32     reordering;     /* Packet reordering metric.            */
 266         u32     reord_seen;     /* number of data packet reordering events */
 267         u32     snd_up;         /* Urgent pointer               */
 268
 269 /*
 270  *      Options received (usually on last packet, some only on SYN packets).
 271  */
 272         struct tcp_options_received rx_opt;
 273
 274 /*
 275  *      Slow start and congestion control (see also Nagle, and Karn & Partridge)
 276  */
 277         u32     snd_ssthresh;   /* Slow start size threshold            */
 278         u32     snd_cwnd;       /* Sending congestion window            */
 279         u32     snd_cwnd_cnt;   /* Linear increase counter              */
 280         u32     snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */
 281         u32     snd_cwnd_used;
 282         u32     snd_cwnd_stamp;
 283         u32     prior_cwnd;     /* cwnd right before starting loss recovery */
 284         u32     prr_delivered;  /* Number of newly delivered packets to
 285                                  * receiver in Recovery. */
 286         u32     prr_out;        /* Total number of pkts sent during Recovery. */
 287         u32     delivered;      /* Total data packets delivered incl. rexmits */
 288         u32     delivered_ce;   /* Like the above but only ECE marked packets */
 289         u32     lost;           /* Total data packets lost incl. rexmits */
 290         u32     app_limited;    /* limited until "delivered" reaches this val */
 291         u64     first_tx_mstamp;  /* start of window send phase */
 292         u64     delivered_mstamp; /* time we reached "delivered" */
 293         u32     rate_delivered;    /* saved rate sample: packets delivered */
 294         u32     rate_interval_us;  /* saved rate sample: time elapsed */
 295
 296         u32     rcv_wnd;        /* Current receiver window              */
 297         u32     write_seq;      /* Tail(+1) of data held in tcp send buffer */
 298         u32     notsent_lowat;  /* TCP_NOTSENT_LOWAT */
 299         u32     pushed_seq;     /* Last pushed seq, required to talk to windows */
 300         u32     lost_out;       /* Lost packets                 */
 301         u32     sacked_out;     /* SACK'd packets                       */
 302
 303         struct hrtimer  pacing_timer;
 304         struct hrtimer  compressed_ack_timer;
 305
 306         /* from STCP, retrans queue hinting */
 307         struct sk_buff* lost_skb_hint;
 308         struct sk_buff *retransmit_skb_hint;
 309
 310         /* OOO segments go in this rbtree. Socket lock must be held. */
 311         struct rb_root  out_of_order_queue;
 312         struct sk_buff  *ooo_last_skb; /* cache rb_last(out_of_order_queue) */
 313
 314         /* SACKs data, these 2 need to be together (see tcp_options_write) */
 315         struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */
 316         struct tcp_sack_block selective_acks[4]; /* The SACKS themselves*/
 317
 318         struct tcp_sack_block recv_sack_cache[4];
 319
 320         struct sk_buff *highest_sack;   /* skb just after the highest
 321                                          * skb with SACKed bit set
 322                                          * (validity guaranteed only if
 323                                          * sacked_out > 0)
 324                                          */
 325
 326         int     lost_cnt_hint;
 327
 328         u32     prior_ssthresh; /* ssthresh saved at recovery start     */
 329         u32     high_seq;       /* snd_nxt at onset of congestion       */
 330
 331         u32     retrans_stamp;  /* Timestamp of the last retransmit,
 332                                  * also used in SYN-SENT to remember stamp of
 333                                  * the first SYN. */
 334         u32     undo_marker;    /* snd_una upon a new recovery episode. */
 335         int     undo_retrans;   /* number of undoable retransmissions. */
 336         u64     bytes_retrans;  /* RFC4898 tcpEStatsPerfOctetsRetrans
 337                                  * Total data bytes retransmitted
 338                                  */
 339         u32     total_retrans;  /* Total retransmits for entire connection */
 340
 341         u32     urg_seq;        /* Seq of received urgent pointer */
 342         unsigned int            keepalive_time;   /* time before keep alive takes place */
 343         unsigned int            keepalive_intvl;  /* time interval between keep alive probes */
 344
 345         int                     linger2;
 346
 347
 348 /* Sock_ops bpf program related variables */
 349 #ifdef CONFIG_BPF
 350         u8      bpf_sock_ops_cb_flags;  /* Control calling BPF programs
 351                                          * values defined in uapi/linux/tcp.h
 352                                          */
 353 #define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) (TP->bpf_sock_ops_cb_flags & ARG)
 354 #else
 355 #define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) 0
 356 #endif
 357
 358         u16 timeout_rehash;     /* Timeout-triggered rehash attempts */
 359
 360         u32 rcv_ooopack; /* Received out-of-order packets, for tcpinfo */
 361
 362 /* Receiver side RTT estimation */
 363         u32 rcv_rtt_last_tsecr;
 364         struct {
 365                 u32     rtt_us;
 366                 u32     seq;
 367                 u64     time;
 368         } rcv_rtt_est;
 369
 370 /* Receiver queue space */
 371         struct {
 372                 u32     space;
 373                 u32     seq;
 374                 u64     time;
 375         } rcvq_space;
 376
 377 /* TCP-specific MTU probe information. */
 378         struct {
 379                 u32               probe_seq_start;
 380                 u32               probe_seq_end;
 381         } mtu_probe;
 382         u32     mtu_info; /* We received an ICMP_FRAG_NEEDED / ICMPV6_PKT_TOOBIG
 383                            * while socket was owned by user.
 384                            */
 385 #if IS_ENABLED(CONFIG_MPTCP)
 386         bool    is_mptcp;
 387 #endif
 388
 389 #ifdef CONFIG_TCP_MD5SIG
 390 /* TCP AF-Specific parts; only used by MD5 Signature support so far */
 391         const struct tcp_sock_af_ops    *af_specific;
 392
 393 /* TCP MD5 Signature Option information */
 394         struct tcp_md5sig_info  __rcu *md5sig_info;
 395 #endif
 396
 397 /* TCP fastopen related information */
 398         struct tcp_fastopen_request *fastopen_req;
 399         /* fastopen_rsk points to request_sock that resulted in this big
 400          * socket. Used to retransmit SYNACKs etc.
 401          */
 402         struct request_sock __rcu *fastopen_rsk;
 403         u32     *saved_syn;
 404 };
 405
 406 enum tsq_enum {
 407         TSQ_THROTTLED,
 408         TSQ_QUEUED,
 409         TCP_TSQ_DEFERRED,          /* tcp_tasklet_func() found socket was owned */
 410         TCP_WRITE_TIMER_DEFERRED,  /* tcp_write_timer() found socket was owned */
 411         TCP_DELACK_TIMER_DEFERRED, /* tcp_delack_timer() found socket was owned */
 412         TCP_MTU_REDUCED_DEFERRED,  /* tcp_v{4|6}_err() could not call
 413                                     * tcp_v{4|6}_mtu_reduced()
 414                                     */
 415 };
 416
 417 enum tsq_flags {
 418         TSQF_THROTTLED                  = (1UL << TSQ_THROTTLED),
 419         TSQF_QUEUED                     = (1UL << TSQ_QUEUED),
 420         TCPF_TSQ_DEFERRED               = (1UL << TCP_TSQ_DEFERRED),
 421         TCPF_WRITE_TIMER_DEFERRED       = (1UL << TCP_WRITE_TIMER_DEFERRED),
 422         TCPF_DELACK_TIMER_DEFERRED      = (1UL << TCP_DELACK_TIMER_DEFERRED),
 423         TCPF_MTU_REDUCED_DEFERRED       = (1UL << TCP_MTU_REDUCED_DEFERRED),
 424 };
 425
 426 static inline struct tcp_sock *tcp_sk(const struct sock *sk)
 427 {
 428         return (struct tcp_sock *)sk;
 429 }
 430
 431 struct tcp_timewait_sock {
 432         struct inet_timewait_sock tw_sk;
 433 #define tw_rcv_nxt tw_sk.__tw_common.skc_tw_rcv_nxt
 434 #define tw_snd_nxt tw_sk.__tw_common.skc_tw_snd_nxt
 435         u32                       tw_rcv_wnd;
 436         u32                       tw_ts_offset;
 437         u32                       tw_ts_recent;
 438
 439         /* The time we sent the last out-of-window ACK: */
 440         u32                       tw_last_oow_ack_time;
 441
 442         int                       tw_ts_recent_stamp;
 443         u32                       tw_tx_delay;
 444 #ifdef CONFIG_TCP_MD5SIG
 445         struct tcp_md5sig_key     *tw_md5_key;
 446 #endif
 447 };
 448
 449 static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
 450 {
 451         return (struct tcp_timewait_sock *)sk;
 452 }
 453
 454 static inline bool tcp_passive_fastopen(const struct sock *sk)
 455 {
 456         return sk->sk_state == TCP_SYN_RECV &&
 457                rcu_access_pointer(tcp_sk(sk)->fastopen_rsk) != NULL;
 458 }
 459
 460 static inline void fastopen_queue_tune(struct sock *sk, int backlog)
 461 {
 462         struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
 463         int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);
 464
 465         queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
 466 }
 467
 468 static inline void tcp_move_syn(struct tcp_sock *tp,
 469                                 struct request_sock *req)
 470 {
 471         tp->saved_syn = req->saved_syn;
 472         req->saved_syn = NULL;
 473 }
 474
 475 static inline void tcp_saved_syn_free(struct tcp_sock *tp)
 476 {
 477         kfree(tp->saved_syn);
 478         tp->saved_syn = NULL;
 479 }
 480
 481 struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk);
 482
 483 static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss)
 484 {
 485         /* We use READ_ONCE() here because socket might not be locked.
 486          * This happens for listeners.
 487          */
 488         u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);
 489
 490         return (user_mss && user_mss < mss) ? user_mss : mss;
 491 }
 492
 493 int tcp_skb_shift(struct sk_buff *to, struct sk_buff *from, int pcount,
 494                   int shiftlen);
 495
 496 #endif  /* _LINUX_TCP_H */