/src/openthread/third_party/tcplp/bsdtcp/tcp_var.h

Source
/*-
 * Copyright (c) 1982, 1986, 1993, 1994, 1995
 *  The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *  @(#)tcp_var.h 8.4 (Berkeley) 5/24/95
 * $FreeBSD$
 */

#ifndef TCPLP_NETINET_TCP_VAR_H_
#define TCPLP_NETINET_TCP_VAR_H_

/* For memmove(). */
#include <string.h>

/* Dependencies on OpenThread. */
#include <openthread/ip6.h>
#include <openthread/message.h>

/* Dependencies on TCPlp buffering libraries. */
#include "../lib/bitmap.h"
#include "../lib/cbuf.h"
#include "../lib/lbuf.h"

#include "cc.h"
#include "tcp.h"
#include "types.h"
#include "ip6.h"

#define TCP_RFC7413

/* Implement byte-order-specific functions using OpenThread. */
uint16_t tcplp_sys_hostswap16(uint16_t hostport);
uint32_t tcplp_sys_hostswap32(uint32_t hostport);

/*
 * It seems that these are defined as macros in Mac OS X, which is why we need
 * the #ifndef checks. Simply redefining them as functions would break the
 * build.
 */

#ifndef htons
static inline uint16_t htons(uint16_t hostport) {
  return tcplp_sys_hostswap16(hostport);
}
#endif

#ifndef ntohs
static inline uint16_t ntohs(uint16_t hostport) {
  return tcplp_sys_hostswap16(hostport);
}
#endif

#ifndef htonl
static inline uint32_t htonl(uint32_t hostport) {
  return tcplp_sys_hostswap32(hostport);
}
#endif

#ifndef ntohl
static inline uint32_t ntohl(uint32_t hostport) {
  return tcplp_sys_hostswap32(hostport);
}
#endif

// From ip_compat.h
#ifndef bcopy
#define bcopy(a,b,c)  memmove(b,a,c)
#endif

#ifndef bzero
#define bzero(a,b)  memset(a,0x00,b)
#endif

struct sackblk {
  tcp_seq start;    /* start seq no. of sack block */
  tcp_seq end;    /* end seq no. */
};

struct sackhole {
  tcp_seq start;    /* start seq no. of hole */
  tcp_seq end;    /* end seq no. */
  tcp_seq rxmit;    /* next seq. no in hole to be retransmitted */

  /*
   * samkumar: I'm using this instead of the TAILQ_ENTRY macro to avoid
   * including sys/queue.h from this file. It's undesirable to include
   * sys/queue.h from this file because this file is part of the external
   * interface to TCPlp, and sys/queue.h pollutes the global namespace.
   * The original code that uses TAILQ_ENTRY is in a comment below.
   */
  struct {
    struct sackhole *tqe_next;  /* next element */
    struct sackhole **tqe_prev; /* address of previous next element */
  } scblink;  /* scoreboard linkage */
  // TAILQ_ENTRY(sackhole) scblink; /* scoreboard linkage */
};

struct sackhint {
  struct sackhole *nexthole;
  int   sack_bytes_rexmit;
  tcp_seq   last_sack_ack;  /* Most recent/largest sacked ack */
};

struct tcptemp {
  uint8_t tt_ipgen[40]; /* the size must be of max ip header, now IPv6 */
  struct  tcphdr tt_t;
};

#define tcp6cb    tcpcb  /* for KAME src sync over BSD*'s */

/* Abridged TCB for passive sockets. */
struct tcpcb_listen {
    int t_state;     /* Always CLOSED or LISTEN. */
    otInstance* instance;
  struct in6_addr laddr;
    uint16_t lport;
};

#define TCB_CANTRCVMORE 0x20
#define TCB_CANTSENDMORE 0x40

#define TCB_PASSIVE 0x80

#define tpcantrcvmore(tp) (tp)->miscflags |= TCB_CANTRCVMORE
#define tpcantsendmore(tp) (tp)->miscflags |= TCB_CANTSENDMORE
#define tpiscantrcv(tp) (((tp)->miscflags & TCB_CANTRCVMORE) != 0)
#define tpiscantsend(tp) (((tp)->miscflags & TCB_CANTSENDMORE) != 0)
#define tpmarktimeractive(tp, timer) (tp)->miscflags |= timer
#define tpistimeractive(tp, timer) (((tp)->miscflags & timer) != 0)
#define tpcleartimeractive(tp, timer) (tp)->miscflags &= ~timer
#define tpmarkpassiveopen(tp) (tp)->miscflags |= TCB_PASSIVE
#define tpispassiveopen(tp) (((tp)->miscflags & TCB_PASSIVE) != 0)

#define REASSBMP_SIZE(tp) BITS_TO_BYTES((tp)->recvbuf.size)

/* These estimates are used to allocate sackholes (see tcp_sack.c). */
#define AVG_SACKHOLES 2 // per TCB
#define MAX_SACKHOLES 5 // per TCB
#define SACKHOLE_POOL_SIZE MAX_SACKHOLES
#define SACKHOLE_BMP_SIZE BITS_TO_BYTES(SACKHOLE_POOL_SIZE)

struct tcplp_signals;

/*
 * Tcp control block, one per tcp; fields:
 * Organized for 16 byte cacheline efficiency.
 */
/*
 * samkumar: I added some fields for TCPlp to the beginning of this structure,
 * replaced the fields for buffering and timers, and deleted unused fields to
 * save memory. I've left some of the deleted fields in, as comments, for
 * clarity. At times, I reduced the configurability of the implementation
 * (e.g., by removing the ability to set keepalive parameters) in order to
 * reduce the size of this structure.
 */
struct tcpcb {
  /*
   * samkumar: Extra fields that I added. TCPlp doesn't have a struct inpcb,
   * so some of the fields I added represent data that would normally be
   * stored in the inpcb.
   */
  otInstance *instance;

  struct tcpcb_listen* accepted_from;

  struct lbufhead sendbuf;
  struct cbufhead recvbuf;
  uint8_t* reassbmp;
  int32_t reass_fin_index;

  struct in6_addr laddr; // local IP address
  struct in6_addr faddr; // foreign IP address

  uint16_t lport; // local port, network byte order
  uint16_t fport; // foreign port, network byte order
  uint8_t miscflags;

  /* samkumar: This field was there previously. */
  uint8_t t_state;    /* state of this connection */

  /* Pool of SACK holes (on per-connection basis, for OpenThread port). */
  struct sackhole sackhole_pool[SACKHOLE_POOL_SIZE];
  uint8_t sackhole_bmp[SACKHOLE_BMP_SIZE];

#if 0
  struct  tsegqe_head t_segq; /* segment reassembly queue */
  void  *t_pspare[2];   /* new reassembly queue */
  int t_segqlen;    /* segment reassembly queue length */
#endif

  int32_t t_dupacks;    /* consecutive dup acks recd */

#if 0
  struct tcp_timer *t_timers; /* All the TCP timers in one struct */

  struct  inpcb *t_inpcb;   /* back pointer to internet pcb */
#endif

  uint16_t  tw_last_win; // samkumar: Taken from struct tcptw

  uint32_t  t_flags;

//  struct  vnet *t_vnet;   /* back pointer to parent vnet */

  tcp_seq snd_una;    /* sent but unacknowledged */
  tcp_seq snd_max;    /* highest sequence number sent;
           * used to recognize retransmits
           */
  tcp_seq snd_nxt;    /* send next */
  tcp_seq snd_up;     /* send urgent pointer */

  tcp_seq snd_wl1;    /* window update seg seq number */
  tcp_seq snd_wl2;    /* window update seg ack number */
  tcp_seq iss;      /* initial send sequence number */
  tcp_seq irs;      /* initial receive sequence number */

  tcp_seq rcv_nxt;    /* receive next */
  tcp_seq rcv_adv;    /* advertised window */
  tcp_seq rcv_up;     /* receive urgent pointer */
  uint64_t  rcv_wnd;    /* receive window */

  uint64_t  snd_wnd;    /* send window */
  uint64_t  snd_cwnd;   /* congestion-controlled window */
//  uint64_t  snd_spare1;   /* unused */
  uint64_t  snd_ssthresh;   /* snd_cwnd size threshold for
           * for slow start exponential to
           * linear switch
           */
//  uint64_t  snd_spare2;   /* unused */
  tcp_seq snd_recover;    /* for use in NewReno Fast Recovery */

  uint32_t  t_maxopd;   /* mss plus options */

  uint32_t  t_rcvtime;    /* inactivity time */
  uint32_t  t_starttime;    /* time connection was established */
  uint32_t  t_rtttime;    /* RTT measurement start time */
  tcp_seq t_rtseq;    /* sequence number being timed */

//  uint32_t  t_bw_spare1;    /* unused */
//  tcp_seq t_bw_spare2;    /* unused */

  int32_t t_rxtcur;   /* current retransmit value (ticks) */
  uint32_t  t_maxseg;   /* maximum segment size */
  int32_t t_srtt;     /* smoothed round-trip time */
  int32_t t_rttvar;   /* variance in round-trip time */

  int32_t t_rxtshift;   /* log(2) of rexmt exp. backoff */
  uint32_t  t_rttmin;   /* minimum rtt allowed */
  uint32_t  t_rttbest;    /* best rtt we've seen */

  int32_t t_softerror;    /* possible error not yet reported */

  uint64_t  t_rttupdated;   /* number of times rtt sampled */
  uint64_t  max_sndwnd;   /* largest window peer has offered */
/* out-of-band data */
//  char  t_oobflags;   /* have some */
//  char  t_iobc;     /* input character */

  tcp_seq last_ack_sent;
/* experimental */
  tcp_seq snd_recover_prev; /* snd_recover prior to retransmit */
  uint64_t  snd_cwnd_prev;    /* cwnd prior to retransmit */
  uint64_t  snd_ssthresh_prev;  /* ssthresh prior to retransmit */
//  int t_sndzerowin;   /* zero-window updates sent */
  uint32_t  t_badrxtwin;    /* window for retransmit recovery */
  uint8_t snd_limited;    /* segments limited transmitted */

/* RFC 1323 variables */
/*
 * samkumar: Moved "RFC 1323 variables" after "experimental" to reduce
 * compiler-inserted padding.
 */
  uint8_t snd_scale;    /* window scaling for send window */
  uint8_t rcv_scale;    /* window scaling for recv window */
  uint8_t request_r_scale;  /* pending window scaling */
  u_int32_t  ts_recent;   /* timestamp echo data */
  uint32_t  ts_recent_age;    /* when last updated */
  u_int32_t  ts_offset;   /* our timestamp offset */

/* SACK related state */
  int32_t snd_numholes;   /* number of holes seen by sender */
  /*
   * samkumar: I replaced the TAILQ_HEAD macro invocation (commented out
   * below) with the code it stands for, to avoid having to #include
   * sys/queue.h in this file. See the comment above in struct sackhole for
   * more info.
   */
  struct sackhole_head {
    struct sackhole *tqh_first; /* first element */
    struct sackhole **tqh_last; /* addr of last next element */
  } snd_holes;
  // TAILQ_HEAD(sackhole_head, sackhole) snd_holes;
          /* SACK scoreboard (sorted) */
  tcp_seq snd_fack;   /* last seq number(+1) sack'd by rcv'r*/
  int32_t rcv_numsacks;   /* # distinct sack blks present */
  struct sackblk sackblks[MAX_SACK_BLKS]; /* seq nos. of sack blocks */
  tcp_seq sack_newdata;   /* New data xmitted in this recovery
             episode starts at this seq number */
  struct sackhint sackhint; /* SACK scoreboard hint */

  int32_t t_rttlow;   /* smallest observed RTT */
#if 0
  u_int32_t rfbuf_ts; /* recv buffer autoscaling timestamp */
  int rfbuf_cnt;    /* recv buffer autoscaling byte count */
  struct toedev *tod;   /* toedev handling this connection */
#endif
//  int t_sndrexmitpack;  /* retransmit packets sent */
//  int t_rcvoopack;    /* out-of-order packets received */
//  void  *t_toe;     /* TOE pcb pointer */
  int32_t t_bytes_acked;    /* # bytes acked during current RTT */
//  struct cc_algo  *cc_algo; /* congestion control algorithm */
  struct cc_var ccv[1];   /* congestion control specific vars */
#if 0
  struct osd  *osd;   /* storage for Khelp module data */
#endif
#if 0 // Just use the default values for the KEEP constants (see tcp_timer.h)
  uint32_t  t_keepinit;   /* time to establish connection */
  uint32_t  t_keepidle;   /* time before keepalive probes begin */
  uint32_t  t_keepintvl;    /* interval between keepalives */
  uint32_t  t_keepcnt;    /* number of keepalives before close */
#endif
#if 0 // Don't support TCP Segment Offloading
  uint32_t  t_tsomax;   /* TSO total burst length limit in bytes */
  uint32_t  t_tsomaxsegcount; /* TSO maximum segment count */
  uint32_t  t_tsomaxsegsize;  /* TSO maximum segment size in bytes */
#endif
//  uint32_t  t_pmtud_saved_maxopd; /* pre-blackhole MSS */
  uint32_t  t_flags2;   /* More tcpcb flags storage */

//  uint32_t t_ispare[8];   /* 5 UTO, 3 TBD */
//  void  *t_pspare2[4];    /* 1 TCP_SIGNATURE, 3 TBD */

    /* samkumar: TFO fields from FreeBSD 12.0. */
  uint64_t t_tfo_client_cookie_len; /* TCP Fast Open client cookie length */
//  unsigned int *t_tfo_pending;  /* TCP Fast Open server pending counter */
  union {
    uint8_t client[TCP_FASTOPEN_MAX_COOKIE_LEN];
    uint64_t server;
  } t_tfo_cookie;     /* TCP Fast Open cookie to send */
#if 0
#if defined(_KERNEL) && defined(TCPPCAP)
  struct mbufq t_inpkts;    /* List of saved input packets. */
  struct mbufq t_outpkts;   /* List of saved output packets. */
#ifdef _LP64
  uint64_t _pad[0];   /* all used! */
#else
  uint64_t _pad[2];   /* 2 are available */
#endif /* _LP64 */
#else
  uint64_t _pad[6];
#endif /* defined(_KERNEL) && defined(TCPPCAP) */
#endif
};

/* Defined in tcp_subr.c. */
void initialize_tcb(struct tcpcb* tp);

/* Copied from the "dead" portions below. */

void   tcp_state_change(struct tcpcb *, int);
tcp_seq tcp_new_isn(struct tcpcb *);
struct tcpcb *tcp_close_tcb(struct tcpcb *);
struct tcpcb *tcp_drop(struct tcpcb *, int);
void
tcp_respond(struct tcpcb *tp, otInstance* instance, struct ip6_hdr* ip6gen, struct tcphdr *thgen,
    tcp_seq ack, tcp_seq seq, int flags);
void   tcp_setpersist(struct tcpcb *);
void  cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type);

/* Added, since there is no header file for tcp_usrreq.c. */
int tcp6_usr_connect(struct tcpcb* tp, struct sockaddr_in6* sinp6);
int tcp_usr_send(struct tcpcb* tp, int moretocome, struct otLinkedBuffer* data, size_t extendby, struct sockaddr_in6* nam);
int tcp_usr_rcvd(struct tcpcb* tp);
int tcp_usr_shutdown(struct tcpcb* tp);
void tcp_usr_abort(struct tcpcb* tp);

/*
 * Flags and utility macros for the t_flags field.
 */
#define TF_ACKNOW 0x000001  /* ack peer immediately */
#define TF_DELACK 0x000002  /* ack, but try to delay it */
#define TF_NODELAY  0x000004  /* don't delay packets to coalesce */
#define TF_NOOPT  0x000008  /* don't use tcp options */
#define TF_SENTFIN  0x000010  /* have sent FIN */
#define TF_REQ_SCALE  0x000020  /* have/will request window scaling */
#define TF_RCVD_SCALE 0x000040  /* other side has requested scaling */
#define TF_REQ_TSTMP  0x000080  /* have/will request timestamps */
#define TF_RCVD_TSTMP 0x000100  /* a timestamp was received in SYN */
#define TF_SACK_PERMIT  0x000200  /* other side said I could SACK */
#define TF_NEEDSYN  0x000400  /* send SYN (implicit state) */
#define TF_NEEDFIN  0x000800  /* send FIN (implicit state) */
#define TF_NOPUSH 0x001000  /* don't push */
#define TF_PREVVALID  0x002000  /* saved values for bad rxmit valid */
#define TF_MORETOCOME 0x010000  /* More data to be appended to sock */
#define TF_LQ_OVERFLOW  0x020000  /* listen queue overflow */
#define TF_LASTIDLE 0x040000  /* connection was previously idle */
#define TF_RXWIN0SENT 0x080000  /* sent a receiver win 0 in response */
#define TF_FASTRECOVERY 0x100000  /* in NewReno Fast Recovery */
#define TF_WASFRECOVERY 0x200000  /* was in NewReno Fast Recovery */
#define TF_SIGNATURE  0x400000  /* require MD5 digests (RFC2385) */
#define TF_FORCEDATA  0x800000  /* force out a byte */
#define TF_TSO    0x1000000 /* TSO enabled on this connection */
#define TF_TOE    0x2000000 /* this connection is offloaded */
#define TF_ECN_PERMIT 0x4000000  /* connection ECN-ready */
#define TF_ECN_SND_CWR  0x8000000  /* ECN CWR in queue */
#define TF_ECN_SND_ECE  0x10000000  /* ECN ECE in queue */
#define TF_CONGRECOVERY 0x20000000  /* congestion recovery mode */
#define TF_WASCRECOVERY 0x40000000  /* was in congestion recovery */
#define TF_FASTOPEN 0x80000000  /* TCP Fast Open indication */

#define IN_FASTRECOVERY(t_flags)  (t_flags & TF_FASTRECOVERY)
#define ENTER_FASTRECOVERY(t_flags) t_flags |= TF_FASTRECOVERY
#define EXIT_FASTRECOVERY(t_flags)  t_flags &= ~TF_FASTRECOVERY

#define IN_CONGRECOVERY(t_flags)  (t_flags & TF_CONGRECOVERY)
#define ENTER_CONGRECOVERY(t_flags) t_flags |= TF_CONGRECOVERY
#define EXIT_CONGRECOVERY(t_flags)  t_flags &= ~TF_CONGRECOVERY

#define IN_RECOVERY(t_flags) (t_flags & (TF_CONGRECOVERY | TF_FASTRECOVERY))
#define ENTER_RECOVERY(t_flags) t_flags |= (TF_CONGRECOVERY | TF_FASTRECOVERY)
#define EXIT_RECOVERY(t_flags) t_flags &= ~(TF_CONGRECOVERY | TF_FASTRECOVERY)

#ifndef TCP_RFC7413
#define IS_FASTOPEN(t_flags)    (false)
#else
#define IS_FASTOPEN(t_flags)    (t_flags & TF_FASTOPEN)
#endif

#define BYTES_THIS_ACK(tp, th)  (th->th_ack - tp->snd_una)

/*
 * Flags for the t_oobflags field.
 */
#define TCPOOB_HAVEDATA 0x01
#define TCPOOB_HADDATA  0x02

#ifdef TCP_SIGNATURE
/*
 * Defines which are needed by the xform_tcp module and tcp_[in|out]put
 * for SADB verification and lookup.
 */
#define TCP_SIGLEN  16  /* length of computed digest in bytes */
#define TCP_KEYLEN_MIN  1 /* minimum length of TCP-MD5 key */
#define TCP_KEYLEN_MAX  80  /* maximum length of TCP-MD5 key */
/*
 * Only a single SA per host may be specified at this time. An SPI is
 * needed in order for the KEY_ALLOCSA() lookup to work.
 */
#define TCP_SIG_SPI 0x1000
#endif /* TCP_SIGNATURE */

/*
 * Flags for PLPMTU handling, t_flags2
 */
#define TF2_PLPMTU_BLACKHOLE  0x00000001 /* Possible PLPMTUD Black Hole. */
#define TF2_PLPMTU_PMTUD  0x00000002 /* Allowed to attempt PLPMTUD. */
#define TF2_PLPMTU_MAXSEGSNT  0x00000004 /* Last seg sent was full seg. */

/*
 * Structure to hold TCP options that are only used during segment
 * processing (in tcplp_input), but not held in the tcpcb.
 * It's basically used to reduce the number of parameters
 * to tcp_dooptions and tcp_addoptions.
 * The binary order of the to_flags is relevant for packing of the
 * options in tcp_addoptions.
 */
struct tcpopt {
  u_int64_t to_flags; /* which options are present */
#define TOF_MSS   0x0001    /* maximum segment size */
#define TOF_SCALE 0x0002    /* window scaling */
#define TOF_SACKPERM  0x0004    /* SACK permitted */
#define TOF_TS    0x0010    /* timestamp */
#define TOF_SIGNATURE 0x0040    /* TCP-MD5 signature option (RFC2385) */
#define TOF_SACK  0x0080    /* Peer sent SACK option */
#define TOF_FASTOPEN  0x0100    /* TCP Fast Open (TFO) cookie */
#define TOF_MAXOPT  0x0200
  u_int32_t to_tsval; /* new timestamp */
  u_int32_t to_tsecr; /* reflected timestamp */
  uint8_t   *to_sacks;  /* pointer to the first SACK blocks */
  uint8_t   *to_signature;  /* pointer to the TCP-MD5 signature */
  u_int8_t  *to_tfo_cookie; /* pointer to the TFO cookie */
  u_int16_t to_mss;   /* maximum segment size */
  u_int8_t  to_wscale;  /* window scaling */
  u_int8_t  to_nsacks;  /* number of SACK blocks */
  u_int8_t  to_tfo_len; /* TFO cookie length */
  u_int32_t to_spare; /* UTO */
};

/*
 * Flags for tcp_dooptions.
 */
#define TO_SYN    0x01    /* parse SYN-only options */

struct hc_metrics_lite {  /* must stay in sync with hc_metrics */
  uint64_t  rmx_mtu;  /* MTU for this path */
  uint64_t  rmx_ssthresh; /* outbound gateway buffer limit */
  uint64_t  rmx_rtt;  /* estimated round trip time */
  uint64_t  rmx_rttvar; /* estimated rtt variance */
  uint64_t  rmx_bandwidth;  /* estimated bandwidth */
  uint64_t  rmx_cwnd; /* congestion window */
  uint64_t  rmx_sendpipe;   /* outbound delay-bandwidth product */
  uint64_t  rmx_recvpipe;   /* inbound delay-bandwidth product */
};

/*
 * Used by tcp_maxmtu() to communicate interface specific features
 * and limits at the time of connection setup.
 */
struct tcp_ifcap {
  int ifcap;
  uint32_t  tsomax;
  uint32_t  tsomaxsegcount;
  uint32_t  tsomaxsegsize;
};

void   tcp_mss(struct tcpcb *, int);
void   tcp_mss_update(struct tcpcb *, int, int, struct hc_metrics_lite *,
      struct tcp_ifcap *);

/*
 * The smoothed round-trip time and estimated variance
 * are stored as fixed point numbers scaled by the values below.
 * For convenience, these scales are also used in smoothing the average
 * (smoothed = (1/scale)sample + ((scale-1)/scale)smoothed).
 * With these scales, srtt has 3 bits to the right of the binary point,
 * and thus an "ALPHA" of 0.875.  rttvar has 2 bits to the right of the
 * binary point, and is smoothed with an ALPHA of 0.75.
 */
#define TCP_RTT_SCALE   32  /* multiplier for srtt; 3 bits frac. */
#define TCP_RTT_SHIFT   5  /* shift for srtt; 3 bits frac. */
#define TCP_RTTVAR_SCALE  16  /* multiplier for rttvar; 2 bits */
#define TCP_RTTVAR_SHIFT  4  /* shift for rttvar; 2 bits */
#define TCP_DELTA_SHIFT   2  /* see tcp_input.c */

/* My definition of the max macro */
#define max(x, y) ((x) > (y) ? (x) : (y))

/*
 * The initial retransmission should happen at rtt + 4 * rttvar.
 * Because of the way we do the smoothing, srtt and rttvar
 * will each average +1/2 tick of bias.  When we compute
 * the retransmit timer, we want 1/2 tick of rounding and
 * 1 extra tick because of +-1/2 tick uncertainty in the
 * firing of the timer.  The bias will give us exactly the
 * 1.5 tick we need.  But, because the bias is
 * statistical, we have to test that we don't drop below
 * the minimum feasible timer (which is 2 ticks).
 * This version of the macro adapted from a paper by Lawrence
 * Brakmo and Larry Peterson which outlines a problem caused
 * by insufficient precision in the original implementation,
 * which results in inappropriately large RTO values for very
 * fast networks.
 */
#define TCP_REXMTVAL(tp) \
  max((tp)->t_rttmin, (((tp)->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT))  \
    + (tp)->t_rttvar) >> TCP_DELTA_SHIFT)

/* Copied from below. */
static inline void
tcp_fields_to_host(struct tcphdr *th)
{

  th->th_seq = ntohl(th->th_seq);
  th->th_ack = ntohl(th->th_ack);
  th->th_win = ntohs(th->th_win);
  th->th_urp = ntohs(th->th_urp);
}

void   tcp_twstart(struct tcpcb*);
void   tcp_twclose(struct tcpcb*, int);
int  tcp_twcheck(struct tcpcb*, struct tcphdr *, int);
void tcp_dropwithreset(struct ip6_hdr* ip6, struct tcphdr *th, struct tcpcb *tp, otInstance* instance,
    int tlen, int rstreason);
int tcplp_input(struct ip6_hdr* ip6, struct tcphdr* th, otMessage* msg, struct tcpcb* tp, struct tcpcb_listen* tpl,
          struct tcplp_signals* sig);
int  tcplp_output(struct tcpcb *);
void tcpip_maketemplate(struct tcpcb *, struct tcptemp*);
void   tcpip_fillheaders(struct tcpcb *, otMessageInfo *, void *);
uint64_t   tcp_maxmtu6(struct tcpcb*, struct tcp_ifcap *);
int  tcp_addoptions(struct tcpopt *, uint8_t *);
int  tcp_mssopt(struct tcpcb*);
int  tcp_reass(struct tcpcb *, struct tcphdr *, int *, otMessage *, off_t, struct tcplp_signals*);
void tcp_sack_init(struct tcpcb *); // Sam: new function that I added
void   tcp_sack_doack(struct tcpcb *, struct tcpopt *, tcp_seq);
void   tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_laststart, tcp_seq rcv_lastend);
void   tcp_clean_sackreport(struct tcpcb *tp);
void   tcp_sack_adjust(struct tcpcb *tp);
struct sackhole *tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt);
void   tcp_sack_partialack(struct tcpcb *, struct tcphdr *);
void   tcp_free_sackholes(struct tcpcb *tp);

#define tcps_rcvmemdrop tcps_rcvreassfull /* compat */0

/*
 * Identifiers for TCP sysctl nodes
 */
#define TCPCTL_DO_RFC1323 1 /* use RFC-1323 extensions */
#define TCPCTL_MSSDFLT    3 /* MSS default */
#define TCPCTL_STATS    4 /* statistics (read-only) */
#define TCPCTL_RTTDFLT    5 /* default RTT estimate */
#define TCPCTL_KEEPIDLE   6 /* keepalive idle timer */
#define TCPCTL_KEEPINTVL  7 /* interval to send keepalives */
#define TCPCTL_SENDSPACE  8 /* send buffer space */
#define TCPCTL_RECVSPACE  9 /* receive buffer space */
#define TCPCTL_KEEPINIT   10  /* timeout for establishing syn */
#define TCPCTL_PCBLIST    11  /* list of all outstanding PCBs */
#define TCPCTL_DELACKTIME 12  /* time before sending delayed ACK */
#define TCPCTL_V6MSSDFLT  13  /* MSS default for IPv6 */
#define TCPCTL_SACK   14  /* Selective Acknowledgement,rfc 2018 */
#define TCPCTL_DROP   15  /* drop tcp connection */

#endif /* _NETINET_TCP_VAR_H_ */

Coverage Report

Created: 2026-01-10 06:49