include/linux/tcp.h

   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 protocol.
   7  *
   8  * Version:     @(#)tcp.h       1.0.2   04/28/93
   9  *
  10  * Author:      Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  11  *
  12  *              This program is free software; you can redistribute it and/or
  13  *              modify it under the terms of the GNU General Public License
  14  *              as published by the Free Software Foundation; either version
  15  *              2 of the License, or (at your option) any later version.
  16  */
  17 #ifndef _LINUX_TCP_H
  18 #define _LINUX_TCP_H
  19
  20
  21 #include <linux/skbuff.h>
  22 #include <linux/win_minmax.h>
  23 #include <net/sock.h>
  24 #include <net/inet_connection_sock.h>
  25 #include <net/inet_timewait_sock.h>
  26 #include <uapi/linux/tcp.h>
  27
  28 static inline struct tcphdr *tcp_hdr(const struct sk_buff *skb)
  29 {
  30         return (struct tcphdr *)skb_transport_header(skb);
  31 }
  32
  33 static inline unsigned int __tcp_hdrlen(const struct tcphdr *th)
  34 {
  35         return th->doff * 4;
  36 }
  37
  38 static inline unsigned int tcp_hdrlen(const struct sk_buff *skb)
  39 {
  40         return __tcp_hdrlen(tcp_hdr(skb));
  41 }
  42
  43 static inline struct tcphdr *inner_tcp_hdr(const struct sk_buff *skb)
  44 {
  45         return (struct tcphdr *)skb_inner_transport_header(skb);
  46 }
  47
  48 static inline unsigned int inner_tcp_hdrlen(const struct sk_buff *skb)
  49 {
  50         return inner_tcp_hdr(skb)->doff * 4;
  51 }
  52
  53 static inline unsigned int tcp_optlen(const struct sk_buff *skb)
  54 {
  55         return (tcp_hdr(skb)->doff - 5) * 4;
  56 }
  57
  58 /* TCP Fast Open */
  59 #define TCP_FASTOPEN_COOKIE_MIN 4       /* Min Fast Open Cookie size in bytes */
  60 #define TCP_FASTOPEN_COOKIE_MAX 16      /* Max Fast Open Cookie size in bytes */
  61 #define TCP_FASTOPEN_COOKIE_SIZE 8      /* the size employed by this impl. */
  62
  63 /* TCP Fast Open Cookie as stored in memory */
  64 struct tcp_fastopen_cookie {
  65         union {
  66                 u8      val[TCP_FASTOPEN_COOKIE_MAX];
  67 #if IS_ENABLED(CONFIG_IPV6)
  68                 struct in6_addr addr;
  69 #endif
  70         };
  71         s8      len;
  72         bool    exp;    /* In RFC6994 experimental option format */
  73 };
  74
  75 /* This defines a selective acknowledgement block. */
  76 struct tcp_sack_block_wire {
  77         __be32  start_seq;
  78         __be32  end_seq;
  79 };
  80
  81 struct tcp_sack_block {
  82         u32     start_seq;
  83         u32     end_seq;
  84 };
  85
  86 /*These are used to set the sack_ok field in struct tcp_options_received */
  87 #define TCP_SACK_SEEN     (1 << 0)   /*1 = peer is SACK capable, */
  88 #define TCP_DSACK_SEEN    (1 << 2)   /*1 = DSACK was received from peer*/
  89
  90 struct tcp_options_received {
  91 /*      PAWS/RTTM data  */
  92         long    ts_recent_stamp;/* Time we stored ts_recent (for aging) */
  93         u32     ts_recent;      /* Time stamp to echo next              */
  94         u32     rcv_tsval;      /* Time stamp value                     */
  95         u32     rcv_tsecr;      /* Time stamp echo reply                */
  96         u16     saw_tstamp : 1, /* Saw TIMESTAMP on last packet         */
  97                 tstamp_ok : 1,  /* TIMESTAMP seen on SYN packet         */
  98                 dsack : 1,      /* D-SACK is scheduled                  */
  99                 wscale_ok : 1,  /* Wscale seen on SYN packet            */
 100                 sack_ok : 3,    /* SACK seen on SYN packet              */
 101                 smc_ok : 1,     /* SMC seen on SYN packet               */
 102                 snd_wscale : 4, /* Window scaling received from sender  */
 103                 rcv_wscale : 4; /* Window scaling to send to receiver   */
 104         u8      num_sacks;      /* Number of SACK blocks                */
 105         u16     user_mss;       /* mss requested by user in ioctl       */
 106         u16     mss_clamp;      /* Maximal mss, negotiated at connection setup */
 107 };
 108
 109 static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
 110 {
 111         rx_opt->tstamp_ok = rx_opt->sack_ok = 0;
 112         rx_opt->wscale_ok = rx_opt->snd_wscale = 0;
 113 #if IS_ENABLED(CONFIG_SMC)
 114         rx_opt->smc_ok = 0;
 115 #endif
 116 }
 117
 118 /* This is the max number of SACKS that we'll generate and process. It's safe
 119  * to increase this, although since:
 120  *   size = TCPOLEN_SACK_BASE_ALIGNED (4) + n * TCPOLEN_SACK_PERBLOCK (8)
 121  * only four options will fit in a standard TCP header */
 122 #define TCP_NUM_SACKS 4
 123
 124 struct tcp_request_sock_ops;
 125
 126 struct tcp_request_sock {
 127         struct inet_request_sock        req;
 128         const struct tcp_request_sock_ops *af_specific;
 129         u64                             snt_synack; /* first SYNACK sent time */
 130         bool                            tfo_listener;
 131         u32                             txhash;
 132         u32                             rcv_isn;
 133         u32                             snt_isn;
 134         u32                             ts_off;
 135         u32                             last_oow_ack_time; /* last SYNACK */
 136         u32                             rcv_nxt; /* the ack # by SYNACK. For
 137                                                   * FastOpen it's the seq#
 138                                                   * after data-in-SYN.
 139                                                   */
 140 };
 141
 142 static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)
 143 {
 144         return (struct tcp_request_sock *)req;
 145 }
 146
 147 struct tcp_sock {
 148         /* inet_connection_sock has to be the first member of tcp_sock */
 149         struct inet_connection_sock     inet_conn;
 150         u16     tcp_header_len; /* Bytes of tcp header to send          */
 151         u16     gso_segs;       /* Max number of segs per GSO packet    */
 152
 153 /*
 154  *      Header prediction flags
 155  *      0x5?10 << 16 + snd_wnd in net byte order
 156  */
 157         __be32  pred_flags;
 158
 159 /*
 160  *      RFC793 variables by their proper names. This means you can
 161  *      read the code and the spec side by side (and laugh ...)
 162  *      See RFC793 and RFC1122. The RFC writes these in capitals.
 163  */
 164         u64     bytes_received; /* RFC4898 tcpEStatsAppHCThruOctetsReceived
 165                                  * sum(delta(rcv_nxt)), or how many bytes
 166                                  * were acked.
 167                                  */
 168         u32     segs_in;        /* RFC4898 tcpEStatsPerfSegsIn
 169                                  * total number of segments in.
 170                                  */
 171         u32     data_segs_in;   /* RFC4898 tcpEStatsPerfDataSegsIn
 172                                  * total number of data segments in.
 173                                  */
 174         u32     rcv_nxt;        /* What we want to receive next         */
 175         u32     copied_seq;     /* Head of yet unread data              */
 176         u32     rcv_wup;        /* rcv_nxt on last window update sent   */
 177         u32     snd_nxt;        /* Next sequence we send                */
 178         u32     segs_out;       /* RFC4898 tcpEStatsPerfSegsOut
 179                                  * The total number of segments sent.
 180                                  */
 181         u32     data_segs_out;  /* RFC4898 tcpEStatsPerfDataSegsOut
 182                                  * total number of data segments sent.
 183                                  */
 184         u64     bytes_acked;    /* RFC4898 tcpEStatsAppHCThruOctetsAcked
 185                                  * sum(delta(snd_una)), or how many bytes
 186                                  * were acked.
 187                                  */
 188         u32     snd_una;        /* First byte we want an ack for        */
 189         u32     snd_sml;        /* Last byte of the most recently transmitted small packet */
 190         u32     rcv_tstamp;     /* timestamp of last received ACK (for keepalives) */
 191         u32     lsndtime;       /* timestamp of last sent data packet (for restart window) */
 192         u32     last_oow_ack_time;  /* timestamp of last out-of-window ACK */
 193
 194         u32     tsoffset;       /* timestamp offset */
 195
 196         struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
 197         struct list_head tsorted_sent_queue; /* time-sorted sent but un-SACKed skbs */
 198
 199         u32     snd_wl1;        /* Sequence for window update           */
 200         u32     snd_wnd;        /* The window we expect to receive      */
 201         u32     max_window;     /* Maximal window ever seen from peer   */
 202         u32     mss_cache;      /* Cached effective mss, not including SACKS */
 203
 204         u32     window_clamp;   /* Maximal window to advertise          */
 205         u32     rcv_ssthresh;   /* Current window clamp                 */
 206
 207         /* Information of the most recently (s)acked skb */
 208         struct tcp_rack {
 209                 u64 mstamp; /* (Re)sent time of the skb */
 210                 u32 rtt_us;  /* Associated RTT */
 211                 u32 end_seq; /* Ending TCP sequence of the skb */
 212                 u32 last_delivered; /* tp->delivered at last reo_wnd adj */
 213                 u8 reo_wnd_steps;   /* Allowed reordering window */
 214 #define TCP_RACK_RECOVERY_THRESH 16
 215                 u8 reo_wnd_persist:5, /* No. of recovery since last adj */
 216                    dsack_seen:1, /* Whether DSACK seen after last adj */
 217                    advanced:1,   /* mstamp advanced since last lost marking */
 218                    reord:1;      /* reordering detected */
 219         } rack;
 220         u16     advmss;         /* Advertised MSS                       */
 221         u32     chrono_start;   /* Start time in jiffies of a TCP chrono */
 222         u32     chrono_stat[3]; /* Time in jiffies for chrono_stat stats */
 223         u8      chrono_type:2,  /* current chronograph type */
 224                 rate_app_limited:1,  /* rate_{delivered,interval_us} limited? */
 225                 fastopen_connect:1, /* FASTOPEN_CONNECT sockopt */
 226                 fastopen_no_cookie:1, /* Allow send/recv SYN+data without a cookie */
 227                 unused:3;
 228         u8      nonagle     : 4,/* Disable Nagle algorithm?             */
 229                 thin_lto    : 1,/* Use linear timeouts for thin streams */
 230                 unused1     : 1,
 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 /* RTT measurement */
 245         u64     tcp_mstamp;     /* most recent packet received/sent */
 246         u32     srtt_us;        /* smoothed round trip time << 3 in usecs */
 247         u32     mdev_us;        /* medium deviation                     */
 248         u32     mdev_max_us;    /* maximal mdev for the last rtt period */
 249         u32     rttvar_us;      /* smoothed mdev_max                    */
 250         u32     rtt_seq;        /* sequence number to update rttvar     */
 251         struct  minmax rtt_min;
 252
 253         u32     packets_out;    /* Packets which are "in flight"        */
 254         u32     retrans_out;    /* Retransmitted packets out            */
 255         u32     max_packets_out;  /* max packets_out in last window */
 256         u32     max_packets_seq;  /* right edge of max_packets_out flight */
 257
 258         u16     urg_data;       /* Saved octet of OOB data and control flags */
 259         u8      ecn_flags;      /* ECN status bits.                     */
 260         u8      keepalive_probes; /* num of allowed keep alive probes   */
 261         u32     reordering;     /* Packet reordering metric.            */
 262         u32     snd_up;         /* Urgent pointer               */
 263
 264 /*
 265  *      Options received (usually on last packet, some only on SYN packets).
 266  */
 267         struct tcp_options_received rx_opt;
 268
 269 /*
 270  *      Slow start and congestion control (see also Nagle, and Karn & Partridge)
 271  */
 272         u32     snd_ssthresh;   /* Slow start size threshold            */
 273         u32     snd_cwnd;       /* Sending congestion window            */
 274         u32     snd_cwnd_cnt;   /* Linear increase counter              */
 275         u32     snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */
 276         u32     snd_cwnd_used;
 277         u32     snd_cwnd_stamp;
 278         u32     prior_cwnd;     /* cwnd right before starting loss recovery */
 279         u32     prr_delivered;  /* Number of newly delivered packets to
 280                                  * receiver in Recovery. */
 281         u32     prr_out;        /* Total number of pkts sent during Recovery. */
 282         u32     delivered;      /* Total data packets delivered incl. rexmits */
 283         u32     lost;           /* Total data packets lost incl. rexmits */
 284         u32     app_limited;    /* limited until "delivered" reaches this val */
 285         u64     first_tx_mstamp;  /* start of window send phase */
 286         u64     delivered_mstamp; /* time we reached "delivered" */
 287         u32     rate_delivered;    /* saved rate sample: packets delivered */
 288         u32     rate_interval_us;  /* saved rate sample: time elapsed */
 289
 290         u32     rcv_wnd;        /* Current receiver window              */
 291         u32     write_seq;      /* Tail(+1) of data held in tcp send buffer */
 292         u32     notsent_lowat;  /* TCP_NOTSENT_LOWAT */
 293         u32     pushed_seq;     /* Last pushed seq, required to talk to windows */
 294         u32     lost_out;       /* Lost packets                 */
 295         u32     sacked_out;     /* SACK'd packets                       */
 296
 297         struct hrtimer  pacing_timer;
 298
 299         /* from STCP, retrans queue hinting */
 300         struct sk_buff* lost_skb_hint;
 301         struct sk_buff *retransmit_skb_hint;
 302
 303         /* OOO segments go in this rbtree. Socket lock must be held. */
 304         struct rb_root  out_of_order_queue;
 305         struct sk_buff  *ooo_last_skb; /* cache rb_last(out_of_order_queue) */
 306
 307         /* SACKs data, these 2 need to be together (see tcp_options_write) */
 308         struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */
 309         struct tcp_sack_block selective_acks[4]; /* The SACKS themselves*/
 310
 311         struct tcp_sack_block recv_sack_cache[4];
 312
 313         struct sk_buff *highest_sack;   /* skb just after the highest
 314                                          * skb with SACKed bit set
 315                                          * (validity guaranteed only if
 316                                          * sacked_out > 0)
 317                                          */
 318
 319         int     lost_cnt_hint;
 320
 321         u32     prior_ssthresh; /* ssthresh saved at recovery start     */
 322         u32     high_seq;       /* snd_nxt at onset of congestion       */
 323
 324         u32     retrans_stamp;  /* Timestamp of the last retransmit,
 325                                  * also used in SYN-SENT to remember stamp of
 326                                  * the first SYN. */
 327         u32     undo_marker;    /* snd_una upon a new recovery episode. */
 328         int     undo_retrans;   /* number of undoable retransmissions. */
 329         u32     total_retrans;  /* Total retransmits for entire connection */
 330
 331         u32     urg_seq;        /* Seq of received urgent pointer */
 332         unsigned int            keepalive_time;   /* time before keep alive takes place */
 333         unsigned int            keepalive_intvl;  /* time interval between keep alive probes */
 334
 335         int                     linger2;
 336
 337 /* Receiver side RTT estimation */
 338         struct {
 339                 u32     rtt_us;
 340                 u32     seq;
 341                 u64     time;
 342         } rcv_rtt_est;
 343
 344 /* Receiver queue space */
 345         struct {
 346                 int     space;
 347                 u32     seq;
 348                 u64     time;
 349         } rcvq_space;
 350
 351 /* TCP-specific MTU probe information. */
 352         struct {
 353                 u32               probe_seq_start;
 354                 u32               probe_seq_end;
 355         } mtu_probe;
 356         u32     mtu_info; /* We received an ICMP_FRAG_NEEDED / ICMPV6_PKT_TOOBIG
 357                            * while socket was owned by user.
 358                            */
 359
 360 #ifdef CONFIG_TCP_MD5SIG
 361 /* TCP AF-Specific parts; only used by MD5 Signature support so far */
 362         const struct tcp_sock_af_ops    *af_specific;
 363
 364 /* TCP MD5 Signature Option information */
 365         struct tcp_md5sig_info  __rcu *md5sig_info;
 366 #endif
 367
 368 /* TCP fastopen related information */
 369         struct tcp_fastopen_request *fastopen_req;
 370         /* fastopen_rsk points to request_sock that resulted in this big
 371          * socket. Used to retransmit SYNACKs etc.
 372          */
 373         struct request_sock *fastopen_rsk;
 374         u32     *saved_syn;
 375 };
 376
 377 enum tsq_enum {
 378         TSQ_THROTTLED,
 379         TSQ_QUEUED,
 380         TCP_TSQ_DEFERRED,          /* tcp_tasklet_func() found socket was owned */
 381         TCP_WRITE_TIMER_DEFERRED,  /* tcp_write_timer() found socket was owned */
 382         TCP_DELACK_TIMER_DEFERRED, /* tcp_delack_timer() found socket was owned */
 383         TCP_MTU_REDUCED_DEFERRED,  /* tcp_v{4|6}_err() could not call
 384                                     * tcp_v{4|6}_mtu_reduced()
 385                                     */
 386 };
 387
 388 enum tsq_flags {
 389         TSQF_THROTTLED                  = (1UL << TSQ_THROTTLED),
 390         TSQF_QUEUED                     = (1UL << TSQ_QUEUED),
 391         TCPF_TSQ_DEFERRED               = (1UL << TCP_TSQ_DEFERRED),
 392         TCPF_WRITE_TIMER_DEFERRED       = (1UL << TCP_WRITE_TIMER_DEFERRED),
 393         TCPF_DELACK_TIMER_DEFERRED      = (1UL << TCP_DELACK_TIMER_DEFERRED),
 394         TCPF_MTU_REDUCED_DEFERRED       = (1UL << TCP_MTU_REDUCED_DEFERRED),
 395 };
 396
 397 static inline struct tcp_sock *tcp_sk(const struct sock *sk)
 398 {
 399         return (struct tcp_sock *)sk;
 400 }
 401
 402 struct tcp_timewait_sock {
 403         struct inet_timewait_sock tw_sk;
 404 #define tw_rcv_nxt tw_sk.__tw_common.skc_tw_rcv_nxt
 405 #define tw_snd_nxt tw_sk.__tw_common.skc_tw_snd_nxt
 406         u32                       tw_rcv_wnd;
 407         u32                       tw_ts_offset;
 408         u32                       tw_ts_recent;
 409
 410         /* The time we sent the last out-of-window ACK: */
 411         u32                       tw_last_oow_ack_time;
 412
 413         long                      tw_ts_recent_stamp;
 414 #ifdef CONFIG_TCP_MD5SIG
 415         struct tcp_md5sig_key     *tw_md5_key;
 416 #endif
 417 };
 418
 419 static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
 420 {
 421         return (struct tcp_timewait_sock *)sk;
 422 }
 423
 424 static inline bool tcp_passive_fastopen(const struct sock *sk)
 425 {
 426         return (sk->sk_state == TCP_SYN_RECV &&
 427                 tcp_sk(sk)->fastopen_rsk != NULL);
 428 }
 429
 430 static inline void fastopen_queue_tune(struct sock *sk, int backlog)
 431 {
 432         struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
 433         int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);
 434
 435         queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
 436 }
 437
 438 static inline void tcp_move_syn(struct tcp_sock *tp,
 439                                 struct request_sock *req)
 440 {
 441         tp->saved_syn = req->saved_syn;
 442         req->saved_syn = NULL;
 443 }
 444
 445 static inline void tcp_saved_syn_free(struct tcp_sock *tp)
 446 {
 447         kfree(tp->saved_syn);
 448         tp->saved_syn = NULL;
 449 }
 450
 451 struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk);
 452
 453 static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss)
 454 {
 455         /* We use READ_ONCE() here because socket might not be locked.
 456          * This happens for listeners.
 457          */
 458         u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);
 459
 460         return (user_mss && user_mss < mss) ? user_mss : mss;
 461 }
 462 #endif  /* _LINUX_TCP_H */