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         u64                             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         u32     snd_wl1;        /* Sequence for window update           */
 196         u32     snd_wnd;        /* The window we expect to receive      */
 197         u32     max_window;     /* Maximal window ever seen from peer   */
 198         u32     mss_cache;      /* Cached effective mss, not including SACKS */
 199
 200         u32     window_clamp;   /* Maximal window to advertise          */
 201         u32     rcv_ssthresh;   /* Current window clamp                 */
 202
 203         /* Information of the most recently (s)acked skb */
 204         struct tcp_rack {
 205                 u64 mstamp; /* (Re)sent time of the skb */
 206                 u32 rtt_us;  /* Associated RTT */
 207                 u32 end_seq; /* Ending TCP sequence of the skb */
 208                 u8 advanced; /* mstamp advanced since last lost marking */
 209                 u8 reord;    /* reordering detected */
 210         } rack;
 211         u16     advmss;         /* Advertised MSS                       */
 212         u32     chrono_start;   /* Start time in jiffies of a TCP chrono */
 213         u32     chrono_stat[3]; /* Time in jiffies for chrono_stat stats */
 214         u8      chrono_type:2,  /* current chronograph type */
 215                 rate_app_limited:1,  /* rate_{delivered,interval_us} limited? */
 216                 fastopen_connect:1, /* FASTOPEN_CONNECT sockopt */
 217                 unused:4;
 218         u8      nonagle     : 4,/* Disable Nagle algorithm?             */
 219                 thin_lto    : 1,/* Use linear timeouts for thin streams */
 220                 unused1     : 1,
 221                 repair      : 1,
 222                 frto        : 1;/* F-RTO (RFC5682) activated in CA_Loss */
 223         u8      repair_queue;
 224         u8      syn_data:1,     /* SYN includes data */
 225                 syn_fastopen:1, /* SYN includes Fast Open option */
 226                 syn_fastopen_exp:1,/* SYN includes Fast Open exp. option */
 227                 syn_fastopen_ch:1, /* Active TFO re-enabling probe */
 228                 syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
 229                 save_syn:1,     /* Save headers of SYN packet */
 230                 is_cwnd_limited:1;/* forward progress limited by snd_cwnd? */
 231         u32     tlp_high_seq;   /* snd_nxt at the time of TLP retransmit. */
 232
 233 /* RTT measurement */
 234         u64     tcp_mstamp;     /* most recent packet received/sent */
 235         u32     srtt_us;        /* smoothed round trip time << 3 in usecs */
 236         u32     mdev_us;        /* medium deviation                     */
 237         u32     mdev_max_us;    /* maximal mdev for the last rtt period */
 238         u32     rttvar_us;      /* smoothed mdev_max                    */
 239         u32     rtt_seq;        /* sequence number to update rttvar     */
 240         struct  minmax rtt_min;
 241
 242         u32     packets_out;    /* Packets which are "in flight"        */
 243         u32     retrans_out;    /* Retransmitted packets out            */
 244         u32     max_packets_out;  /* max packets_out in last window */
 245         u32     max_packets_seq;  /* right edge of max_packets_out flight */
 246
 247         u16     urg_data;       /* Saved octet of OOB data and control flags */
 248         u8      ecn_flags;      /* ECN status bits.                     */
 249         u8      keepalive_probes; /* num of allowed keep alive probes   */
 250         u32     reordering;     /* Packet reordering metric.            */
 251         u32     snd_up;         /* Urgent pointer               */
 252
 253 /*
 254  *      Options received (usually on last packet, some only on SYN packets).
 255  */
 256         struct tcp_options_received rx_opt;
 257
 258 /*
 259  *      Slow start and congestion control (see also Nagle, and Karn & Partridge)
 260  */
 261         u32     snd_ssthresh;   /* Slow start size threshold            */
 262         u32     snd_cwnd;       /* Sending congestion window            */
 263         u32     snd_cwnd_cnt;   /* Linear increase counter              */
 264         u32     snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */
 265         u32     snd_cwnd_used;
 266         u32     snd_cwnd_stamp;
 267         u32     prior_cwnd;     /* cwnd right before starting loss recovery */
 268         u32     prr_delivered;  /* Number of newly delivered packets to
 269                                  * receiver in Recovery. */
 270         u32     prr_out;        /* Total number of pkts sent during Recovery. */
 271         u32     delivered;      /* Total data packets delivered incl. rexmits */
 272         u32     lost;           /* Total data packets lost incl. rexmits */
 273         u32     app_limited;    /* limited until "delivered" reaches this val */
 274         u64     first_tx_mstamp;  /* start of window send phase */
 275         u64     delivered_mstamp; /* time we reached "delivered" */
 276         u32     rate_delivered;    /* saved rate sample: packets delivered */
 277         u32     rate_interval_us;  /* saved rate sample: time elapsed */
 278
 279         u32     rcv_wnd;        /* Current receiver window              */
 280         u32     write_seq;      /* Tail(+1) of data held in tcp send buffer */
 281         u32     notsent_lowat;  /* TCP_NOTSENT_LOWAT */
 282         u32     pushed_seq;     /* Last pushed seq, required to talk to windows */
 283         u32     lost_out;       /* Lost packets                 */
 284         u32     sacked_out;     /* SACK'd packets                       */
 285         u32     fackets_out;    /* FACK'd packets                       */
 286
 287         struct hrtimer  pacing_timer;
 288
 289         /* from STCP, retrans queue hinting */
 290         struct sk_buff* lost_skb_hint;
 291         struct sk_buff *retransmit_skb_hint;
 292
 293         /* OOO segments go in this rbtree. Socket lock must be held. */
 294         struct rb_root  out_of_order_queue;
 295         struct sk_buff  *ooo_last_skb; /* cache rb_last(out_of_order_queue) */
 296
 297         /* SACKs data, these 2 need to be together (see tcp_options_write) */
 298         struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */
 299         struct tcp_sack_block selective_acks[4]; /* The SACKS themselves*/
 300
 301         struct tcp_sack_block recv_sack_cache[4];
 302
 303         struct sk_buff *highest_sack;   /* skb just after the highest
 304                                          * skb with SACKed bit set
 305                                          * (validity guaranteed only if
 306                                          * sacked_out > 0)
 307                                          */
 308
 309         int     lost_cnt_hint;
 310
 311         u32     prior_ssthresh; /* ssthresh saved at recovery start     */
 312         u32     high_seq;       /* snd_nxt at onset of congestion       */
 313
 314         u32     retrans_stamp;  /* Timestamp of the last retransmit,
 315                                  * also used in SYN-SENT to remember stamp of
 316                                  * the first SYN. */
 317         u32     undo_marker;    /* snd_una upon a new recovery episode. */
 318         int     undo_retrans;   /* number of undoable retransmissions. */
 319         u32     total_retrans;  /* Total retransmits for entire connection */
 320
 321         u32     urg_seq;        /* Seq of received urgent pointer */
 322         unsigned int            keepalive_time;   /* time before keep alive takes place */
 323         unsigned int            keepalive_intvl;  /* time interval between keep alive probes */
 324
 325         int                     linger2;
 326
 327 /* Receiver side RTT estimation */
 328         struct {
 329                 u32     rtt_us;
 330                 u32     seq;
 331                 u64     time;
 332         } rcv_rtt_est;
 333
 334 /* Receiver queue space */
 335         struct {
 336                 int     space;
 337                 u32     seq;
 338                 u64     time;
 339         } rcvq_space;
 340
 341 /* TCP-specific MTU probe information. */
 342         struct {
 343                 u32               probe_seq_start;
 344                 u32               probe_seq_end;
 345         } mtu_probe;
 346         u32     mtu_info; /* We received an ICMP_FRAG_NEEDED / ICMPV6_PKT_TOOBIG
 347                            * while socket was owned by user.
 348                            */
 349
 350 #ifdef CONFIG_TCP_MD5SIG
 351 /* TCP AF-Specific parts; only used by MD5 Signature support so far */
 352         const struct tcp_sock_af_ops    *af_specific;
 353
 354 /* TCP MD5 Signature Option information */
 355         struct tcp_md5sig_info  __rcu *md5sig_info;
 356 #endif
 357
 358 /* TCP fastopen related information */
 359         struct tcp_fastopen_request *fastopen_req;
 360         /* fastopen_rsk points to request_sock that resulted in this big
 361          * socket. Used to retransmit SYNACKs etc.
 362          */
 363         struct request_sock *fastopen_rsk;
 364         u32     *saved_syn;
 365 };
 366
 367 enum tsq_enum {
 368         TSQ_THROTTLED,
 369         TSQ_QUEUED,
 370         TCP_TSQ_DEFERRED,          /* tcp_tasklet_func() found socket was owned */
 371         TCP_WRITE_TIMER_DEFERRED,  /* tcp_write_timer() found socket was owned */
 372         TCP_DELACK_TIMER_DEFERRED, /* tcp_delack_timer() found socket was owned */
 373         TCP_MTU_REDUCED_DEFERRED,  /* tcp_v{4|6}_err() could not call
 374                                     * tcp_v{4|6}_mtu_reduced()
 375                                     */
 376 };
 377
 378 enum tsq_flags {
 379         TSQF_THROTTLED                  = (1UL << TSQ_THROTTLED),
 380         TSQF_QUEUED                     = (1UL << TSQ_QUEUED),
 381         TCPF_TSQ_DEFERRED               = (1UL << TCP_TSQ_DEFERRED),
 382         TCPF_WRITE_TIMER_DEFERRED       = (1UL << TCP_WRITE_TIMER_DEFERRED),
 383         TCPF_DELACK_TIMER_DEFERRED      = (1UL << TCP_DELACK_TIMER_DEFERRED),
 384         TCPF_MTU_REDUCED_DEFERRED       = (1UL << TCP_MTU_REDUCED_DEFERRED),
 385 };
 386
 387 static inline struct tcp_sock *tcp_sk(const struct sock *sk)
 388 {
 389         return (struct tcp_sock *)sk;
 390 }
 391
 392 struct tcp_timewait_sock {
 393         struct inet_timewait_sock tw_sk;
 394 #define tw_rcv_nxt tw_sk.__tw_common.skc_tw_rcv_nxt
 395 #define tw_snd_nxt tw_sk.__tw_common.skc_tw_snd_nxt
 396         u32                       tw_rcv_wnd;
 397         u32                       tw_ts_offset;
 398         u32                       tw_ts_recent;
 399
 400         /* The time we sent the last out-of-window ACK: */
 401         u32                       tw_last_oow_ack_time;
 402
 403         long                      tw_ts_recent_stamp;
 404 #ifdef CONFIG_TCP_MD5SIG
 405         struct tcp_md5sig_key     *tw_md5_key;
 406 #endif
 407 };
 408
 409 static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
 410 {
 411         return (struct tcp_timewait_sock *)sk;
 412 }
 413
 414 static inline bool tcp_passive_fastopen(const struct sock *sk)
 415 {
 416         return (sk->sk_state == TCP_SYN_RECV &&
 417                 tcp_sk(sk)->fastopen_rsk != NULL);
 418 }
 419
 420 static inline void fastopen_queue_tune(struct sock *sk, int backlog)
 421 {
 422         struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
 423         int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);
 424
 425         queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
 426 }
 427
 428 static inline void tcp_move_syn(struct tcp_sock *tp,
 429                                 struct request_sock *req)
 430 {
 431         tp->saved_syn = req->saved_syn;
 432         req->saved_syn = NULL;
 433 }
 434
 435 static inline void tcp_saved_syn_free(struct tcp_sock *tp)
 436 {
 437         kfree(tp->saved_syn);
 438         tp->saved_syn = NULL;
 439 }
 440
 441 struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk);
 442
 443 static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss)
 444 {
 445         /* We use READ_ONCE() here because socket might not be locked.
 446          * This happens for listeners.
 447          */
 448         u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);
 449
 450         return (user_mss && user_mss < mss) ? user_mss : mss;
 451 }
 452 #endif  /* _LINUX_TCP_H */