text: /*
   * Definitions for tcp compression routines.
   *
   * $Id: vj.h,v 1.7 2010/02/22 17:52:09 goldsimon Exp $
   *
   * Copyright (c) 1989 Regents of the University of California.
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms are permitted
   * provided that the above copyright notice and this paragraph are
   * duplicated in all such forms and that any documentation,
   * advertising materials, and other materials related to such
   * distribution and use acknowledge that the software was developed
   * by the University of California, Berkeley.  The name of the
   * University may not be used to endorse or promote products derived
   * from this software without specific prior written permission.
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
   * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
   * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
   *
   * Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
   * - Initial distribution.
   */
  
  #include "netif/ppp/ppp_opts.h"
  #if PPP_SUPPORT &&                                                             \
      VJ_SUPPORT /* don't build if not configured for use in lwipopts.h */
  
  #ifndef VJ_H
  #define VJ_H
  
  #include "lwip/ip.h"
  #include "lwip/priv/tcp_priv.h"
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  #define MAX_SLOTS 16 /* must be > 2 and < 256 */
  #define MAX_HDR 128
  
  /*
   * Compressed packet format:
   *
   * The first octet contains the packet type (top 3 bits), TCP
   * 'push' bit, and flags that indicate which of the 4 TCP sequence
   * numbers have changed (bottom 5 bits).  The next octet is a
   * conversation number that associates a saved IP/TCP header with
   * the compressed packet.  The next two octets are the TCP checksum
   * from the original datagram.  The next 0 to 15 octets are
   * sequence number changes, one change per bit set in the header
   * (there may be no changes and there are two special cases where
   * the receiver implicitly knows what changed -- see below).
   *
   * There are 5 numbers which can change (they are always inserted
   * in the following order): TCP urgent pointer, window,
   * acknowlegement, sequence number and IP ID.  (The urgent pointer
   * is different from the others in that its value is sent, not the
   * change in value.)  Since typical use of SLIP links is biased
   * toward small packets (see comments on MTU/MSS below), changes
   * use a variable length coding with one octet for numbers in the
   * range 1 - 255 and 3 octets (0, MSB, LSB) for numbers in the
   * range 256 - 65535 or 0.  (If the change in sequence number or
   * ack is more than 65535, an uncompressed packet is sent.)
   */
  
  /*
   * Packet types (must not conflict with IP protocol version)
   *
   * The top nibble of the first octet is the packet type.  There are
   * three possible types: IP (not proto TCP or tcp with one of the
   * control flags set); uncompressed TCP (a normal IP/TCP packet but
   * with the 8-bit protocol field replaced by an 8-bit connection id --
   * this type of packet syncs the sender & receiver); and compressed
   * TCP (described above).
   *
   * LSB of 4-bit field is TCP "PUSH" bit (a worthless anachronism) and
   * is logically part of the 4-bit "changes" field that follows.  Top
   * three bits are actual packet type.  For backward compatibility
   * and in the interest of conserving bits, numbers are chosen so the
   * IP protocol version number (4) which normally appears in this nibble
   * means "IP packet".
   */
  
  /* packet types */
  #define TYPE_IP 0x40
  #define TYPE_UNCOMPRESSED_TCP 0x70
  #define TYPE_COMPRESSED_TCP 0x80
  #define TYPE_ERROR 0x00
  
  /* Bits in first octet of compressed packet */
  #define NEW_C 0x40 /* flag bits for what changed in a packet */
  #define NEW_I 0x20
  #define NEW_S 0x08
  #define NEW_A 0x04
  #define NEW_W 0x02
  #define NEW_U 0x01
  
  /* reserved, special-case values of above */
  #define SPECIAL_I (NEW_S | NEW_W | NEW_U) /* echoed interactive traffic */
  #define SPECIAL_D (NEW_S | NEW_A | NEW_W | NEW_U) /* unidirectional data */
  #define SPECIALS_MASK (NEW_S | NEW_A | NEW_W | NEW_U)
  
  #define TCP_PUSH_BIT 0x10
  
  /*
   * "state" data for each active tcp conversation on the wire.  This is
   * basically a copy of the entire IP/TCP header from the last packet
   * we saw from the conversation together with a small identifier
   * the transmit & receive ends of the line use to locate saved header.
   */
  struct cstate {
    struct cstate *cs_next; /* next most recently used state (xmit only) */
    u16_t cs_hlen;          /* size of hdr (receive only) */
    u8_t cs_id;             /* connection # associated with this state */
    u8_t cs_filler;
    union {
      char csu_hdr[MAX_HDR];
      struct ip_hdr csu_ip; /* ip/tcp hdr from most recent packet */
    } vjcs_u;
  };
  #define cs_ip vjcs_u.csu_ip
  #define cs_hdr vjcs_u.csu_hdr
  
  struct vjstat {
    u32_t vjs_packets;        /* outbound packets */
    u32_t vjs_compressed;     /* outbound compressed packets */
    u32_t vjs_searches;       /* searches for connection state */
    u32_t vjs_misses;         /* times couldn't find conn. state */
    u32_t vjs_uncompressedin; /* inbound uncompressed packets */
    u32_t vjs_compressedin;   /* inbound compressed packets */
    u32_t vjs_errorin;        /* inbound unknown type packets */
    u32_t vjs_tossed;         /* inbound packets tossed because of error */
  };
  
  /*
   * all the state data for one serial line (we need one of these per line).
   */
  struct vjcompress {
    struct cstate *last_cs; /* most recently used tstate */
    u8_t last_recv;         /* last rcvd conn. id */
    u8_t last_xmit;         /* last sent conn. id */
    u16_t flags;
    u8_t maxSlotIndex;
    u8_t compressSlot; /* Flag indicating OK to compress slot ID. */
  #if LINK_STATS
    struct vjstat stats;
  #endif
    struct cstate tstate[MAX_SLOTS]; /* xmit connection states */
    struct cstate rstate[MAX_SLOTS]; /* receive connection states */
  };
  
  /* flag values */
  #define VJF_TOSS 1U /* tossing rcvd frames because of input err */
  
  extern void vj_compress_init(struct vjcompress *comp);
  extern u8_t vj_compress_tcp(struct vjcompress *comp, struct pbuf **pb);
  extern void vj_uncompress_err(struct vjcompress *comp);
  extern int vj_uncompress_uncomp(struct pbuf *nb, struct vjcompress *comp);
  extern int vj_uncompress_tcp(struct pbuf **nb, struct vjcompress *comp);
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* VJ_H */
  
  #endif /* PPP_SUPPORT && VJ_SUPPORT */
  