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 <net/sock.h>
  23 #include <net/inet_connection_sock.h>
  24 #include <net/inet_timewait_sock.h>
  25 #include <uapi/linux/tcp.h>
  26
  27 static inline struct tcphdr *tcp_hdr(const struct sk_buff *skb)
  28 {
  29         return (struct tcphdr *)skb_transport_header(skb);
  30 }
  31
  32 static inline unsigned int __tcp_hdrlen(const struct tcphdr *th)
  33 {
  34         return th->doff * 4;
  35 }
  36
  37 static inline unsigned int tcp_hdrlen(const struct sk_buff *skb)
  38 {
  39         return __tcp_hdrlen(tcp_hdr(skb));
  40 }
  41
  42 static inline struct tcphdr *inner_tcp_hdr(const struct sk_buff *skb)
  43 {
  44         return (struct tcphdr *)skb_inner_transport_header(skb);
  45 }
  46
  47 static inline unsigned int inner_tcp_hdrlen(const struct sk_buff *skb)
  48 {
  49         return inner_tcp_hdr(skb)->doff * 4;
  50 }
  51
  52 static inline unsigned int tcp_optlen(const struct sk_buff *skb)
  53 {
  54         return (tcp_hdr(skb)->doff - 5) * 4;
  55 }
  56
  57 /* TCP Fast Open */
  58 #define TCP_FASTOPEN_COOKIE_MIN 4       /* Min Fast Open Cookie size in bytes */
  59 #define TCP_FASTOPEN_COOKIE_MAX 16      /* Max Fast Open Cookie size in bytes */
  60 #define TCP_FASTOPEN_COOKIE_SIZE 8      /* the size employed by this impl. */
  61
  62 /* TCP Fast Open Cookie as stored in memory */
  63 struct tcp_fastopen_cookie {
  64         s8      len;
  65         u8      val[TCP_FASTOPEN_COOKIE_MAX];
  66         bool    exp;    /* In RFC6994 experimental option format */
  67 };
  68
  69 /* This defines a selective acknowledgement block. */
  70 struct tcp_sack_block_wire {
  71         __be32  start_seq;
  72         __be32  end_seq;
  73 };
  74
  75 struct tcp_sack_block {
  76         u32     start_seq;
  77         u32     end_seq;
  78 };
  79
  80 /*These are used to set the sack_ok field in struct tcp_options_received */
  81 #define TCP_SACK_SEEN     (1 << 0)   /*1 = peer is SACK capable, */
  82 #define TCP_FACK_ENABLED  (1 << 1)   /*1 = FACK is enabled locally*/
  83 #define TCP_DSACK_SEEN    (1 << 2)   /*1 = DSACK was received from peer*/
  84
  85 struct tcp_options_received {
  86 /*      PAWS/RTTM data  */
  87         long    ts_recent_stamp;/* Time we stored ts_recent (for aging) */
  88         u32     ts_recent;      /* Time stamp to echo next              */
  89         u32     rcv_tsval;      /* Time stamp value                     */
  90         u32     rcv_tsecr;      /* Time stamp echo reply                */
  91         u16     saw_tstamp : 1, /* Saw TIMESTAMP on last packet         */
  92                 tstamp_ok : 1,  /* TIMESTAMP seen on SYN packet         */
  93                 dsack : 1,      /* D-SACK is scheduled                  */
  94                 wscale_ok : 1,  /* Wscale seen on SYN packet            */
  95                 sack_ok : 4,    /* SACK seen on SYN packet              */
  96                 snd_wscale : 4, /* Window scaling received from sender  */
  97                 rcv_wscale : 4; /* Window scaling to send to receiver   */
  98         u8      num_sacks;      /* Number of SACK blocks                */
  99         u16     user_mss;       /* mss requested by user in ioctl       */
 100         u16     mss_clamp;      /* Maximal mss, negotiated at connection setup */
 101 };
 102
 103 static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
 104 {
 105         rx_opt->tstamp_ok = rx_opt->sack_ok = 0;
 106         rx_opt->wscale_ok = rx_opt->snd_wscale = 0;
 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         struct skb_mstamp               snt_synack; /* first SYNACK sent time */
 121         bool                            tfo_listener;
 122         u32                             txhash;
 123         u32                             rcv_isn;
 124         u32                             snt_isn;
 125         u32                             last_oow_ack_time; /* last SYNACK */
 126         u32                             rcv_nxt; /* the ack # by SYNACK. For
 127                                                   * FastOpen it's the seq#
 128                                                   * after data-in-SYN.
 129                                                   */
 130 };
 131
 132 static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)
 133 {
 134         return (struct tcp_request_sock *)req;
 135 }
 136
 137 struct tcp_sock {
 138         /* inet_connection_sock has to be the first member of tcp_sock */
 139         struct inet_connection_sock     inet_conn;
 140         u16     tcp_header_len; /* Bytes of tcp header to send          */
 141         u16     gso_segs;       /* Max number of segs per GSO packet    */
 142
 143 /*
 144  *      Header prediction flags
 145  *      0x5?10 << 16 + snd_wnd in net byte order
 146  */
 147         __be32  pred_flags;
 148
 149 /*
 150  *      RFC793 variables by their proper names. This means you can
 151  *      read the code and the spec side by side (and laugh ...)
 152  *      See RFC793 and RFC1122. The RFC writes these in capitals.
 153  */
 154         u64     bytes_received; /* RFC4898 tcpEStatsAppHCThruOctetsReceived
 155                                  * sum(delta(rcv_nxt)), or how many bytes
 156                                  * were acked.
 157                                  */
 158         u32     segs_in;        /* RFC4898 tcpEStatsPerfSegsIn
 159                                  * total number of segments in.
 160                                  */
 161         u32     data_segs_in;   /* RFC4898 tcpEStatsPerfDataSegsIn
 162                                  * total number of data segments in.
 163                                  */
 164         u32     rcv_nxt;        /* What we want to receive next         */
 165         u32     copied_seq;     /* Head of yet unread data              */
 166         u32     rcv_wup;        /* rcv_nxt on last window update sent   */
 167         u32     snd_nxt;        /* Next sequence we send                */
 168         u32     segs_out;       /* RFC4898 tcpEStatsPerfSegsOut
 169                                  * The total number of segments sent.
 170                                  */
 171         u32     data_segs_out;  /* RFC4898 tcpEStatsPerfDataSegsOut
 172                                  * total number of data segments sent.
 173                                  */
 174         u64     bytes_acked;    /* RFC4898 tcpEStatsAppHCThruOctetsAcked
 175                                  * sum(delta(snd_una)), or how many bytes
 176                                  * were acked.
 177                                  */
 178         struct u64_stats_sync syncp; /* protects 64bit vars (cf tcp_get_info()) */
 179
 180         u32     snd_una;        /* First byte we want an ack for        */
 181         u32     snd_sml;        /* Last byte of the most recently transmitted small packet */
 182         u32     rcv_tstamp;     /* timestamp of last received ACK (for keepalives) */
 183         u32     lsndtime;       /* timestamp of last sent data packet (for restart window) */
 184         u32     last_oow_ack_time;  /* timestamp of last out-of-window ACK */
 185
 186         u32     tsoffset;       /* timestamp offset */
 187
 188         struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
 189         unsigned long   tsq_flags;
 190
 191         /* Data for direct copy to user */
 192         struct {
 193                 struct sk_buff_head     prequeue;
 194                 struct task_struct      *task;
 195                 struct msghdr           *msg;
 196                 int                     memory;
 197                 int                     len;
 198         } ucopy;
 199
 200         u32     snd_wl1;        /* Sequence for window update           */
 201         u32     snd_wnd;        /* The window we expect to receive      */
 202         u32     max_window;     /* Maximal window ever seen from peer   */
 203         u32     mss_cache;      /* Cached effective mss, not including SACKS */
 204
 205         u32     window_clamp;   /* Maximal window to advertise          */
 206         u32     rcv_ssthresh;   /* Current window clamp                 */
 207
 208         /* Information of the most recently (s)acked skb */
 209         struct tcp_rack {
 210                 struct skb_mstamp mstamp; /* (Re)sent time of the skb */
 211                 u8 advanced; /* mstamp advanced since last lost marking */
 212                 u8 reord;    /* reordering detected */
 213         } rack;
 214         u16     advmss;         /* Advertised MSS                       */
 215         u8      unused;
 216         u8      nonagle     : 4,/* Disable Nagle algorithm?             */
 217                 thin_lto    : 1,/* Use linear timeouts for thin streams */
 218                 thin_dupack : 1,/* Fast retransmit on first dupack      */
 219                 repair      : 1,
 220                 frto        : 1;/* F-RTO (RFC5682) activated in CA_Loss */
 221         u8      repair_queue;
 222         u8      do_early_retrans:1,/* Enable RFC5827 early-retransmit  */
 223                 syn_data:1,     /* SYN includes data */
 224                 syn_fastopen:1, /* SYN includes Fast Open option */
 225                 syn_fastopen_exp:1,/* SYN includes Fast Open exp. option */
 226                 syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
 227                 save_syn:1,     /* Save headers of SYN packet */
 228                 is_cwnd_limited:1;/* forward progress limited by snd_cwnd? */
 229         u32     tlp_high_seq;   /* snd_nxt at the time of TLP retransmit. */
 230
 231 /* RTT measurement */
 232         u32     srtt_us;        /* smoothed round trip time << 3 in usecs */
 233         u32     mdev_us;        /* medium deviation                     */
 234         u32     mdev_max_us;    /* maximal mdev for the last rtt period */
 235         u32     rttvar_us;      /* smoothed mdev_max                    */
 236         u32     rtt_seq;        /* sequence number to update rttvar     */
 237         struct rtt_meas {
 238                 u32 rtt, ts;    /* RTT in usec and sampling time in jiffies. */
 239         } rtt_min[3];
 240
 241         u32     packets_out;    /* Packets which are "in flight"        */
 242         u32     retrans_out;    /* Retransmitted packets out            */
 243         u32     max_packets_out;  /* max packets_out in last window */
 244         u32     max_packets_seq;  /* right edge of max_packets_out flight */
 245
 246         u16     urg_data;       /* Saved octet of OOB data and control flags */
 247         u8      ecn_flags;      /* ECN status bits.                     */
 248         u8      keepalive_probes; /* num of allowed keep alive probes   */
 249         u32     reordering;     /* Packet reordering metric.            */
 250         u32     snd_up;         /* Urgent pointer               */
 251
 252 /*
 253  *      Options received (usually on last packet, some only on SYN packets).
 254  */
 255         struct tcp_options_received rx_opt;
 256
 257 /*
 258  *      Slow start and congestion control (see also Nagle, and Karn & Partridge)
 259  */
 260         u32     snd_ssthresh;   /* Slow start size threshold            */
 261         u32     snd_cwnd;       /* Sending congestion window            */
 262         u32     snd_cwnd_cnt;   /* Linear increase counter              */
 263         u32     snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */
 264         u32     snd_cwnd_used;
 265         u32     snd_cwnd_stamp;
 266         u32     prior_cwnd;     /* Congestion window at start of Recovery. */
 267         u32     prr_delivered;  /* Number of newly delivered packets to
 268                                  * receiver in Recovery. */
 269         u32     prr_out;        /* Total number of pkts sent during Recovery. */
 270         u32     delivered;      /* Total data packets delivered incl. rexmits */
 271
 272         u32     rcv_wnd;        /* Current receiver window              */
 273         u32     write_seq;      /* Tail(+1) of data held in tcp send buffer */
 274         u32     notsent_lowat;  /* TCP_NOTSENT_LOWAT */
 275         u32     pushed_seq;     /* Last pushed seq, required to talk to windows */
 276         u32     lost_out;       /* Lost packets                 */
 277         u32     sacked_out;     /* SACK'd packets                       */
 278         u32     fackets_out;    /* FACK'd packets                       */
 279
 280         /* from STCP, retrans queue hinting */
 281         struct sk_buff* lost_skb_hint;
 282         struct sk_buff *retransmit_skb_hint;
 283
 284         /* OOO segments go in this rbtree. Socket lock must be held. */
 285         struct rb_root  out_of_order_queue;
 286         struct sk_buff  *ooo_last_skb; /* cache rb_last(out_of_order_queue) */
 287
 288         /* SACKs data, these 2 need to be together (see tcp_options_write) */
 289         struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */
 290         struct tcp_sack_block selective_acks[4]; /* The SACKS themselves*/
 291
 292         struct tcp_sack_block recv_sack_cache[4];
 293
 294         struct sk_buff *highest_sack;   /* skb just after the highest
 295                                          * skb with SACKed bit set
 296                                          * (validity guaranteed only if
 297                                          * sacked_out > 0)
 298                                          */
 299
 300         int     lost_cnt_hint;
 301         u32     retransmit_high;        /* L-bits may be on up to this seqno */
 302
 303         u32     prior_ssthresh; /* ssthresh saved at recovery start     */
 304         u32     high_seq;       /* snd_nxt at onset of congestion       */
 305
 306         u32     retrans_stamp;  /* Timestamp of the last retransmit,
 307                                  * also used in SYN-SENT to remember stamp of
 308                                  * the first SYN. */
 309         u32     undo_marker;    /* snd_una upon a new recovery episode. */
 310         int     undo_retrans;   /* number of undoable retransmissions. */
 311         u32     total_retrans;  /* Total retransmits for entire connection */
 312
 313         u32     urg_seq;        /* Seq of received urgent pointer */
 314         unsigned int            keepalive_time;   /* time before keep alive takes place */
 315         unsigned int            keepalive_intvl;  /* time interval between keep alive probes */
 316
 317         int                     linger2;
 318
 319 /* Receiver side RTT estimation */
 320         struct {
 321                 u32     rtt;
 322                 u32     seq;
 323                 u32     time;
 324         } rcv_rtt_est;
 325
 326 /* Receiver queue space */
 327         struct {
 328                 int     space;
 329                 u32     seq;
 330                 u32     time;
 331         } rcvq_space;
 332
 333 /* TCP-specific MTU probe information. */
 334         struct {
 335                 u32               probe_seq_start;
 336                 u32               probe_seq_end;
 337         } mtu_probe;
 338         u32     mtu_info; /* We received an ICMP_FRAG_NEEDED / ICMPV6_PKT_TOOBIG
 339                            * while socket was owned by user.
 340                            */
 341
 342 #ifdef CONFIG_TCP_MD5SIG
 343 /* TCP AF-Specific parts; only used by MD5 Signature support so far */
 344         const struct tcp_sock_af_ops    *af_specific;
 345
 346 /* TCP MD5 Signature Option information */
 347         struct tcp_md5sig_info  __rcu *md5sig_info;
 348 #endif
 349
 350 /* TCP fastopen related information */
 351         struct tcp_fastopen_request *fastopen_req;
 352         /* fastopen_rsk points to request_sock that resulted in this big
 353          * socket. Used to retransmit SYNACKs etc.
 354          */
 355         struct request_sock *fastopen_rsk;
 356         u32     *saved_syn;
 357 };
 358
 359 enum tsq_flags {
 360         TSQ_THROTTLED,
 361         TSQ_QUEUED,
 362         TCP_TSQ_DEFERRED,          /* tcp_tasklet_func() found socket was owned */
 363         TCP_WRITE_TIMER_DEFERRED,  /* tcp_write_timer() found socket was owned */
 364         TCP_DELACK_TIMER_DEFERRED, /* tcp_delack_timer() found socket was owned */
 365         TCP_MTU_REDUCED_DEFERRED,  /* tcp_v{4|6}_err() could not call
 366                                     * tcp_v{4|6}_mtu_reduced()
 367                                     */
 368 };
 369
 370 static inline struct tcp_sock *tcp_sk(const struct sock *sk)
 371 {
 372         return (struct tcp_sock *)sk;
 373 }
 374
 375 struct tcp_timewait_sock {
 376         struct inet_timewait_sock tw_sk;
 377 #define tw_rcv_nxt tw_sk.__tw_common.skc_tw_rcv_nxt
 378 #define tw_snd_nxt tw_sk.__tw_common.skc_tw_snd_nxt
 379         u32                       tw_rcv_wnd;
 380         u32                       tw_ts_offset;
 381         u32                       tw_ts_recent;
 382
 383         /* The time we sent the last out-of-window ACK: */
 384         u32                       tw_last_oow_ack_time;
 385
 386         long                      tw_ts_recent_stamp;
 387 #ifdef CONFIG_TCP_MD5SIG
 388         struct tcp_md5sig_key     *tw_md5_key;
 389 #endif
 390 };
 391
 392 static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
 393 {
 394         return (struct tcp_timewait_sock *)sk;
 395 }
 396
 397 static inline bool tcp_passive_fastopen(const struct sock *sk)
 398 {
 399         return (sk->sk_state == TCP_SYN_RECV &&
 400                 tcp_sk(sk)->fastopen_rsk != NULL);
 401 }
 402
 403 static inline void fastopen_queue_tune(struct sock *sk, int backlog)
 404 {
 405         struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
 406         int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);
 407
 408         queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
 409 }
 410
 411 static inline void tcp_move_syn(struct tcp_sock *tp,
 412                                 struct request_sock *req)
 413 {
 414         tp->saved_syn = req->saved_syn;
 415         req->saved_syn = NULL;
 416 }
 417
 418 static inline void tcp_saved_syn_free(struct tcp_sock *tp)
 419 {
 420         kfree(tp->saved_syn);
 421         tp->saved_syn = NULL;
 422 }
 423
 424 #endif  /* _LINUX_TCP_H */