usr/include/sys/pack.h

struct pack {
        short   p_state;        /* line state */
        short   p_bits;         /* mask for getepack */
        short   p_psize;        /* packet size */
        short   p_icount;       /* input byte count */
        char    p_ostate;       /* output state */
        char    p_istate;       /* input state */
        char    p_msgs;         /* # cntl msgs sent */
        char    p_window;       /* window size */
        char    p_iseq;         /* input SEQ byte */
        char    p_oseq;         /* output SEQ byte */
        char    p_msg;          /* control msg */
        char    p_msg2;         /* extra msg bits */
        char    p_ps,p_pr;      /* last packet sent, recv'd */
        char    p_rps,p_rpr;    /* remote (received) ps and pr */
        char    p_nxtps;        /* next output seq number */
        char    p_nxtpr;        /* expected input seq number */
        char    p_prcopy;       /* oldest received packet in kernel */
        char    p_pscopy;       /* newest output packet */
        char    *p_input;       /* points into input buffer */
        char    p_iobuf[6];     /* cntl packet buffer */
        char    *p_ob[8];       /* output buffers */
        char    *p_ib[8];       /* input buffers */
        char    p_bstate[8];    /* output buffer status */
        char    p_cstate[8];    /* input buffer status */
        short   p_checks[8];
        short   p_rcheck;
        struct tty *p_ttyp;
        int     p_timer;
        int     xcount,rcount;
};
#define NPSTRUCT        (1+(sizeof(struct pack))/64)
#define NPERBUF         (8/NPSTRUCT)
#define CHECK   0125252

int     npbits;

/*
 * driver state
 */
#define DEAD    0
#define INITa   1
#define INITb   2
#define ISINIT  3
#define LIVE    4
#define RESYNC  010
#define DOWN    020
#define RREJ    040
#define RXMIT   0100
#define PDEBUG  0200
#define DRAINO  0400
#define WAITO   01000

/*
 * input side states
 */
#define P_IDLE  1
#define P_SCAN  2
#define P_SEQ1  3
#define P_PACK  4
#define P_CHK1  5
#define P_CHK2  6
#define P_SEQ2  7
#define P_FLUSH 8

#define SYN     026

/*
 * output side states
 */
#define T_IDLE  0
#define T_READY 1
#define T_HDR   2
#define T_PACK  3
#define T_TAIL  4

/*
 * io buffer states
 */
#define B_FREE  0
#define B_READY 1
#define B_SENT  2
#define B_PACK  4
#define B_COPY  010
#define B_XMIT  020

/*
 * frame control messages
 */
#define RR      1
#define RWR     2
#define REJ     3
#define CLOSE   4
#define RESET   6
#define INIT    7
#define UA      8


#define PKOPRI  31
#define PKIPRI  30

#define NPLINES 8

/*
 * packet ioctl buf
 */
struct  piocb {
        unsigned t;
        short   psize;
        short   mode;
        short   state;
        char    window;
};