vjcompress.h

PPP协议的实现演示

// file from the rfc 1144


/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/


#ifndef _VJCOMPRESS_H_
#define _VJCOMPRESS_H_

#define MAX_STATES 16		/* must be >2 and <255 */
#define MAX_HDR 128		/* max TCP+IP hdr length (by protocol def) */

/* packet types */
#define TYPE_IP 0x40
#define TYPE_UNCOMPRESSED_TCP 0x70
#define TYPE_COMPRESSED_TCP 0x80
#define TYPE_ERROR 0x00		/* this is not a type that ever appears on
				 * the wire.  The receive framer uses it to
				 * tell the decompressor there was a packet
				 * transmission error. */

/*
 * Bits in first octet of compressed packet
 */

/* flag bits for what changed in a packet */
#define NEW_C  0x40
#define NEW_I  0x20
#define TCP_PUSH_BIT 0x10

#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)

/*
 * "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 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 cstate (xmit only) */
    u_short cs_hlen;		/* size of hdr (receive only) */
    u_char cs_id;		/* connection # associated with this state */
    u_char cs_filler;
    union {
	char hdr[MAX_HDR];
	struct ip csu_ip;	/* ip/tcp hdr from most recent packet */
    } slcs_u;
};

#define cs_ip slcs_u.csu_ip
#define cs_hdr slcs_u.csu_hdr

/*
 * all the state data for one serial line (we need one of these per line).
 */
struct slcompress {
    struct cstate *last_cs;	/* most recently used tstate */
    u_char last_recv;		/* last rcvd conn. id */
    u_char last_xmit;		/* last sent conn. id */
    u_short flags;
    struct cstate tstate[MAX_STATES];	/* xmit connection states */
    struct cstate rstate[MAX_STATES];	/* receive connection states */
};

/* flag values */
#define SLF_TOSS 1		/* tossing rcvd frames because of input err */

/*
 * The following macros are used to encode and decode numbers.  They all
 * assume that `cp' points to a buffer where the next byte encoded (decoded)
 * is to be stored (retrieved).  Since the decode routines do arithmetic,
 * they have to convert from and to network byte order.
 */

/*
 * ENCODE encodes a number that is known to be non-zero.  ENCODEZ checks for
 * zero (zero has to be encoded in the long, 3 byte form).
 */
#define ENCODE(n) { \
        if ((u_short)(n) >= 256) { \
             *cp++ = 0; \
             cp[1] = (n); \
             cp[0] = (n) >> 8; \
             cp += 2; \
        } else { \
             *cp++ = (n); \
        } \
   }

#define ENCODEZ(n) { \
        if ((u_short)(n) >= 256 || (u_short)(n) == 0) { \
             *cp++ = 0; \
             cp[1] = (n); \
             cp[0] = (n) >> 8; \
             cp += 2; \
        } else { \
             *cp++ = (n); \
        } \
   }

/*
 * DECODEL takes the (compressed) change at byte cp and adds it to the
 * current value of packet field 'f' (which must be a 4-byte (long) integer
 * in network byte order).  DECODES does the same for a 2-byte (short) field.
 * DECODEU takes the change at cp and stuffs it into the (short) field f.
 * 'cp' is updated to point to the next field in the compressed header.
 */
#define DECODEL(f) { \
        if (*cp == 0) {\
             (f) = htonl(ntohl(f) + ((cp[1] << 8) | cp[2])); \
             cp += 3; \
        } else { \
             (f) = htonl(ntohl(f) + (u_long)*cp++); \
        } \
   }

#define DECODES(f) { \
        if (*cp == 0) {\
             (f) = htons(ntohs(f) + ((cp[1] << 8) | cp[2])); \
             cp += 3; \
        } else { \
             (f) = htons(ntohs(f) + (u_long)*cp++); \
        } \
   }

#define DECODEU(f) { \
        if (*cp == 0) {\
             (f) = htons((cp[1] << 8) | cp[2]); \
             cp += 3; \
        } else { \
             (f) = htons((u_long)*cp++); \
        } \
   }

#ifndef VJ_NO_STATS
#define INCR(counter) ++comp->stats.counter
#else
#define INCR(counter)
#endif

#define BCMP(p1, p2, n) bcmp((char *)(p1), (char *)(p2), (int)(n))

#undef  BCOPY
#define BCOPY(p1, p2, n) bcopy((char *)(p1), (char *)(p2), (int)(n))

#define OVBCOPY bcopy

#ifdef __osf__
#define getip_hl(base)	(((base).ip_vhl)&0xf)
#define getth_off(base)	((((base).th_xoff)&0xf0)>>4)
#else
#define getip_hl(base)	((base).ip_hl)
#define getth_off(base)	((base).th_off)
#endif


struct mbuf {
    u_char *m_off;		/* pointer to start of data */
    int m_len;			/* length of data */
};

typedef u_int32_t tcp_seq;

struct tcphdr {
    u_int16_t th_sport;		/* source port */
    u_int16_t th_dport;		/* destination port */
    tcp_seq th_seq;		/* sequence number */
    tcp_seq th_ack;		/* acknowledgement number */
#if __BYTE_ORDER == __LITTLE_ENDIAN
    u_int8_t th_x2:4;		/* (unused) */
    u_int8_t th_off:4;		/* data offset */
#endif
#if __BYTE_ORDER == __BIG_ENDIAN
    u_int8_t th_off:4;		/* data offset */
    u_int8_t th_x2:4;		/* (unused) */
#endif
    u_int8_t th_flags;
#define TH_FIN  0x01
#define TH_SYN  0x02
#define TH_RST  0x04
#define TH_PUSH 0x08
#define TH_ACK  0x10
#define TH_URG  0x20
    u_int16_t th_win;		/* window */
    u_int16_t th_sum;		/* checksum */
    u_int16_t th_urp;		/* urgent pointer */
};

#endif