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_FACK_ENABLED  (1 << 1)   /*1 = FACK is enabled locally*/
  89 #define TCP_DSACK_SEEN    (1 << 2)   /*1 = DSACK was received from peer*/
  90
  91 struct tcp_options_received {
  92 /*      PAWS/RTTM data  */
  93         long    ts_recent_stamp;/* Time we stored ts_recent (for aging) */
  94         u32     ts_recent;      /* Time stamp to echo next              */
  95         u32     rcv_tsval;      /* Time stamp value                     */
  96         u32     rcv_tsecr;      /* Time stamp echo reply                */
  97         u16     saw_tstamp : 1, /* Saw TIMESTAMP on last packet         */
  98                 tstamp_ok : 1,  /* TIMESTAMP seen on SYN packet         */
  99                 dsack : 1,      /* D-SACK is scheduled                  */
 100                 wscale_ok : 1,  /* Wscale seen on SYN packet            */
 101                 sack_ok : 4,    /* SACK 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 }
 114
 115 /* This is the max number of SACKS that we'll generate and process. It's safe
 116  * to increase this, although since:
 117  *   size = TCPOLEN_SACK_BASE_ALIGNED (4) + n * TCPOLEN_SACK_PERBLOCK (8)
 118  * only four options will fit in a standard TCP header */
 119 #define TCP_NUM_SACKS 4
 120
 121 struct tcp_request_sock_ops;
 122
 123 struct tcp_request_sock {
 124         struct inet_request_sock        req;
 125         const struct tcp_request_sock_ops *af_specific;
 126         struct skb_mstamp               snt_synack; /* first SYNACK sent time */
 127         bool                            tfo_listener;
 128         u32                             txhash;
 129         u32                             rcv_isn;
 130         u32                             snt_isn;
 131         u32                             ts_off;
 132         u32                             last_oow_ack_time; /* last SYNACK */
 133         u32                             rcv_nxt; /* the ack # by SYNACK. For
 134                                                   * FastOpen it's the seq#
 135                                                   * after data-in-SYN.
 136                                                   */
 137 };
 138
 139 static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)
 140 {
 141         return (struct tcp_request_sock *)req;
 142 }
 143
 144 struct tcp_sock {
 145         /* inet_connection_sock has to be the first member of tcp_sock */
 146         struct inet_connection_sock     inet_conn;
 147         u16     tcp_header_len; /* Bytes of tcp header to send          */
 148         u16     gso_segs;       /* Max number of segs per GSO packet    */
 149
 150 /*
 151  *      Header prediction flags
 152  *      0x5?10 << 16 + snd_wnd in net byte order
 153  */
 154         __be32  pred_flags;
 155
 156 /*
 157  *      RFC793 variables by their proper names. This means you can
 158  *      read the code and the spec side by side (and laugh ...)
 159  *      See RFC793 and RFC1122. The RFC writes these in capitals.
 160  */
 161         u64     bytes_received; /* RFC4898 tcpEStatsAppHCThruOctetsReceived
 162                                  * sum(delta(rcv_nxt)), or how many bytes
 163                                  * were acked.
 164                                  */
 165         u32     segs_in;        /* RFC4898 tcpEStatsPerfSegsIn
 166                                  * total number of segments in.
 167                                  */
 168         u32     data_segs_in;   /* RFC4898 tcpEStatsPerfDataSegsIn
 169                                  * total number of data segments in.
 170                                  */
 171         u32     rcv_nxt;        /* What we want to receive next         */
 172         u32     copied_seq;     /* Head of yet unread data              */
 173         u32     rcv_wup;        /* rcv_nxt on last window update sent   */
 174         u32     snd_nxt;        /* Next sequence we send                */
 175         u32     segs_out;       /* RFC4898 tcpEStatsPerfSegsOut
 176                                  * The total number of segments sent.
 177                                  */
 178         u32     data_segs_out;  /* RFC4898 tcpEStatsPerfDataSegsOut
 179                                  * total number of data segments sent.
 180                                  */
 181         u64     bytes_acked;    /* RFC4898 tcpEStatsAppHCThruOctetsAcked
 182                                  * sum(delta(snd_una)), or how many bytes
 183                                  * were acked.
 184                                  */
 185         u32     snd_una;        /* First byte we want an ack for        */
 186         u32     snd_sml;        /* Last byte of the most recently transmitted small packet */
 187         u32     rcv_tstamp;     /* timestamp of last received ACK (for keepalives) */
 188         u32     lsndtime;       /* timestamp of last sent data packet (for restart window) */
 189         u32     last_oow_ack_time;  /* timestamp of last out-of-window ACK */
 190
 191         u32     tsoffset;       /* timestamp offset */
 192
 193         struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
 194
 195         /* Data for direct copy to user */
 196         struct {
 197                 struct sk_buff_head     prequeue;
 198                 struct task_struct      *task;
 199                 struct msghdr           *msg;
 200                 int                     memory;
 201                 int                     len;
 202         } ucopy;
 203
 204         u32     snd_wl1;        /* Sequence for window update           */
 205         u32     snd_wnd;        /* The window we expect to receive      */
 206         u32     max_window;     /* Maximal window ever seen from peer   */
 207         u32     mss_cache;      /* Cached effective mss, not including SACKS */
 208
 209         u32     window_clamp;   /* Maximal window to advertise          */
 210         u32     rcv_ssthresh;   /* Current window clamp                 */
 211
 212         /* Information of the most recently (s)acked skb */
 213         struct tcp_rack {
 214                 struct skb_mstamp mstamp; /* (Re)sent time of the skb */
 215                 u32 rtt_us;  /* Associated RTT */
 216                 u32 end_seq; /* Ending TCP sequence of the skb */
 217                 u8 advanced; /* mstamp advanced since last lost marking */
 218                 u8 reord;    /* 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                 unused:4;
 227         u8      nonagle     : 4,/* Disable Nagle algorithm?             */
 228                 thin_lto    : 1,/* Use linear timeouts for thin streams */
 229                 unused1     : 1,
 230                 repair      : 1,
 231                 frto        : 1;/* F-RTO (RFC5682) activated in CA_Loss */
 232         u8      repair_queue;
 233         u8      syn_data:1,     /* SYN includes data */
 234                 syn_fastopen:1, /* SYN includes Fast Open option */
 235                 syn_fastopen_exp:1,/* SYN includes Fast Open exp. option */
 236                 syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
 237                 save_syn:1,     /* Save headers of SYN packet */
 238                 is_cwnd_limited:1;/* forward progress limited by snd_cwnd? */
 239         u32     tlp_high_seq;   /* snd_nxt at the time of TLP retransmit. */
 240
 241 /* RTT measurement */
 242         u32     srtt_us;        /* smoothed round trip time << 3 in usecs */
 243         u32     mdev_us;        /* medium deviation                     */
 244         u32     mdev_max_us;    /* maximal mdev for the last rtt period */
 245         u32     rttvar_us;      /* smoothed mdev_max                    */
 246         u32     rtt_seq;        /* sequence number to update rttvar     */
 247         struct  minmax rtt_min;
 248
 249         u32     packets_out;    /* Packets which are "in flight"        */
 250         u32     retrans_out;    /* Retransmitted packets out            */
 251         u32     max_packets_out;  /* max packets_out in last window */
 252         u32     max_packets_seq;  /* right edge of max_packets_out flight */
 253
 254         u16     urg_data;       /* Saved octet of OOB data and control flags */
 255         u8      ecn_flags;      /* ECN status bits.                     */
 256         u8      keepalive_probes; /* num of allowed keep alive probes   */
 257         u32     reordering;     /* Packet reordering metric.            */
 258         u32     snd_up;         /* Urgent pointer               */
 259
 260 /*
 261  *      Options received (usually on last packet, some only on SYN packets).
 262  */
 263         struct tcp_options_received rx_opt;
 264
 265 /*
 266  *      Slow start and congestion control (see also Nagle, and Karn & Partridge)
 267  */
 268         u32     snd_ssthresh;   /* Slow start size threshold            */
 269         u32     snd_cwnd;       /* Sending congestion window            */
 270         u32     snd_cwnd_cnt;   /* Linear increase counter              */
 271         u32     snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */
 272         u32     snd_cwnd_used;
 273         u32     snd_cwnd_stamp;
 274         u32     prior_cwnd;     /* Congestion window at start of Recovery. */
 275         u32     prr_delivered;  /* Number of newly delivered packets to
 276                                  * receiver in Recovery. */
 277         u32     prr_out;        /* Total number of pkts sent during Recovery. */
 278         u32     delivered;      /* Total data packets delivered incl. rexmits */
 279         u32     lost;           /* Total data packets lost incl. rexmits */
 280         u32     app_limited;    /* limited until "delivered" reaches this val */
 281         struct skb_mstamp first_tx_mstamp;  /* start of window send phase */
 282         struct skb_mstamp delivered_mstamp; /* time we reached "delivered" */
 283         u32     rate_delivered;    /* saved rate sample: packets delivered */
 284         u32     rate_interval_us;  /* saved rate sample: time elapsed */
 285
 286         u32     rcv_wnd;        /* Current receiver window              */
 287         u32     write_seq;      /* Tail(+1) of data held in tcp send buffer */
 288         u32     notsent_lowat;  /* TCP_NOTSENT_LOWAT */
 289         u32     pushed_seq;     /* Last pushed seq, required to talk to windows */
 290         u32     lost_out;       /* Lost packets                 */
 291         u32     sacked_out;     /* SACK'd packets                       */
 292         u32     fackets_out;    /* FACK'd packets                       */
 293
 294         /* from STCP, retrans queue hinting */
 295         struct sk_buff* lost_skb_hint;
 296         struct sk_buff *retransmit_skb_hint;
 297
 298         /* OOO segments go in this rbtree. Socket lock must be held. */
 299         struct rb_root  out_of_order_queue;
 300         struct sk_buff  *ooo_last_skb; /* cache rb_last(out_of_order_queue) */
 301
 302         /* SACKs data, these 2 need to be together (see tcp_options_write) */
 303         struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */
 304         struct tcp_sack_block selective_acks[4]; /* The SACKS themselves*/
 305
 306         struct tcp_sack_block recv_sack_cache[4];
 307
 308         struct sk_buff *highest_sack;   /* skb just after the highest
 309                                          * skb with SACKed bit set
 310                                          * (validity guaranteed only if
 311                                          * sacked_out > 0)
 312                                          */
 313
 314         int     lost_cnt_hint;
 315
 316         u32     prior_ssthresh; /* ssthresh saved at recovery start     */
 317         u32     high_seq;       /* snd_nxt at onset of congestion       */
 318
 319         u32     retrans_stamp;  /* Timestamp of the last retransmit,
 320                                  * also used in SYN-SENT to remember stamp of
 321                                  * the first SYN. */
 322         u32     undo_marker;    /* snd_una upon a new recovery episode. */
 323         int     undo_retrans;   /* number of undoable retransmissions. */
 324         u32     total_retrans;  /* Total retransmits for entire connection */
 325
 326         u32     urg_seq;        /* Seq of received urgent pointer */
 327         unsigned int            keepalive_time;   /* time before keep alive takes place */
 328         unsigned int            keepalive_intvl;  /* time interval between keep alive probes */
 329
 330         int                     linger2;
 331
 332 /* Receiver side RTT estimation */
 333         struct {
 334                 u32     rtt;
 335                 u32     seq;
 336                 u32     time;
 337         } rcv_rtt_est;
 338
 339 /* Receiver queue space */
 340         struct {
 341                 int     space;
 342                 u32     seq;
 343                 u32     time;
 344         } rcvq_space;
 345
 346 /* TCP-specific MTU probe information. */
 347         struct {
 348                 u32               probe_seq_start;
 349                 u32               probe_seq_end;
 350         } mtu_probe;
 351         u32     mtu_info; /* We received an ICMP_FRAG_NEEDED / ICMPV6_PKT_TOOBIG
 352                            * while socket was owned by user.
 353                            */
 354
 355 #ifdef CONFIG_TCP_MD5SIG
 356 /* TCP AF-Specific parts; only used by MD5 Signature support so far */
 357         const struct tcp_sock_af_ops    *af_specific;
 358
 359 /* TCP MD5 Signature Option information */
 360         struct tcp_md5sig_info  __rcu *md5sig_info;
 361 #endif
 362
 363 /* TCP fastopen related information */
 364         struct tcp_fastopen_request *fastopen_req;
 365         /* fastopen_rsk points to request_sock that resulted in this big
 366          * socket. Used to retransmit SYNACKs etc.
 367          */
 368         struct request_sock *fastopen_rsk;
 369         u32     *saved_syn;
 370 };
 371
 372 enum tsq_enum {
 373         TSQ_THROTTLED,
 374         TSQ_QUEUED,
 375         TCP_TSQ_DEFERRED,          /* tcp_tasklet_func() found socket was owned */
 376         TCP_WRITE_TIMER_DEFERRED,  /* tcp_write_timer() found socket was owned */
 377         TCP_DELACK_TIMER_DEFERRED, /* tcp_delack_timer() found socket was owned */
 378         TCP_MTU_REDUCED_DEFERRED,  /* tcp_v{4|6}_err() could not call
 379                                     * tcp_v{4|6}_mtu_reduced()
 380                                     */
 381 };
 382
 383 enum tsq_flags {
 384         TSQF_THROTTLED                  = (1UL << TSQ_THROTTLED),
 385         TSQF_QUEUED                     = (1UL << TSQ_QUEUED),
 386         TCPF_TSQ_DEFERRED               = (1UL << TCP_TSQ_DEFERRED),
 387         TCPF_WRITE_TIMER_DEFERRED       = (1UL << TCP_WRITE_TIMER_DEFERRED),
 388         TCPF_DELACK_TIMER_DEFERRED      = (1UL << TCP_DELACK_TIMER_DEFERRED),
 389         TCPF_MTU_REDUCED_DEFERRED       = (1UL << TCP_MTU_REDUCED_DEFERRED),
 390 };
 391
 392 static inline struct tcp_sock *tcp_sk(const struct sock *sk)
 393 {
 394         return (struct tcp_sock *)sk;
 395 }
 396
 397 struct tcp_timewait_sock {
 398         struct inet_timewait_sock tw_sk;
 399 #define tw_rcv_nxt tw_sk.__tw_common.skc_tw_rcv_nxt
 400 #define tw_snd_nxt tw_sk.__tw_common.skc_tw_snd_nxt
 401         u32                       tw_rcv_wnd;
 402         u32                       tw_ts_offset;
 403         u32                       tw_ts_recent;
 404
 405         /* The time we sent the last out-of-window ACK: */
 406         u32                       tw_last_oow_ack_time;
 407
 408         long                      tw_ts_recent_stamp;
 409 #ifdef CONFIG_TCP_MD5SIG
 410         struct tcp_md5sig_key     *tw_md5_key;
 411 #endif
 412 };
 413
 414 static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
 415 {
 416         return (struct tcp_timewait_sock *)sk;
 417 }
 418
 419 static inline bool tcp_passive_fastopen(const struct sock *sk)
 420 {
 421         return (sk->sk_state == TCP_SYN_RECV &&
 422                 tcp_sk(sk)->fastopen_rsk != NULL);
 423 }
 424
 425 static inline void fastopen_queue_tune(struct sock *sk, int backlog)
 426 {
 427         struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
 428         int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);
 429
 430         queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
 431 }
 432
 433 static inline void tcp_move_syn(struct tcp_sock *tp,
 434                                 struct request_sock *req)
 435 {
 436         tp->saved_syn = req->saved_syn;
 437         req->saved_syn = NULL;
 438 }
 439
 440 static inline void tcp_saved_syn_free(struct tcp_sock *tp)
 441 {
 442         kfree(tp->saved_syn);
 443         tp->saved_syn = NULL;
 444 }
 445
 446 struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk);
 447
 448 static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss)
 449 {
 450         /* We use READ_ONCE() here because socket might not be locked.
 451          * This happens for listeners.
 452          */
 453         u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);
 454
 455         return (user_mss && user_mss < mss) ? user_mss : mss;
 456 }
 457 #endif  /* _LINUX_TCP_H */