#define ICMP_ECHOREPLY          0 
#define ICMP_ECHO               8
#define ICMP_MINLEN             8


struct ip {
#if (BYTE_ORDER == LITTLE_ENDIAN || BYTE_ORDER == PDP_ENDIAN)
        u_char  ip_hl:4,                /* header length */
                ip_v:4;                 /* version */
#else
        u_char  ip_v:4,                 /* version */
                ip_hl:4;                /* header length */
#endif
        u_char  ip_tos;                 /* type of service */
        short   ip_len;                 /* total length */
        u_short ip_id;                  /* identification */
        short   ip_off;                 /* fragment offset field */
#define IP_DF 0x4000                    /* dont fragment flag */
#define IP_MF 0x2000                    /* more fragments flag */
        u_char  ip_ttl;                 /* time to live */
        u_char  ip_p;                   /* protocol */
        u_short ip_sum;                 /* checksum */
        struct  in_addr ip_src,ip_dst;  /* source and dest address */
};

#define n_short u_short                 /* normally defined in in_systm.h */
#define n_long  u_int                   /* redefine for 64-bit machines */
#define n_time  u_int                   /* redefine for 64-bit machines */

struct icmp {
        u_char  icmp_type;              /* type of message, see below */
        u_char  icmp_code;              /* type sub code */
        u_short icmp_cksum;             /* ones complement cksum of struct */
        union {
                u_char ih_pptr;                 /* ICMP_PARAMPROB */
                struct in_addr ih_gwaddr;       /* ICMP_REDIRECT */
                struct ih_idseq {
                        n_short icd_id;
                        n_short icd_seq;
                } ih_idseq;
                int ih_void;
        } icmp_hun;
#define icmp_pptr       icmp_hun.ih_pptr
#define icmp_gwaddr     icmp_hun.ih_gwaddr
#define icmp_id         icmp_hun.ih_idseq.icd_id
#define icmp_seq        icmp_hun.ih_idseq.icd_seq
#define icmp_void       icmp_hun.ih_void
        union {
                struct id_ts {
                        n_time its_otime;
                        n_time its_rtime;
                        n_time its_ttime;
                } id_ts;
                struct id_ip  {
                        struct ip idi_ip;
                        /* options and then 64 bits of data */
                } id_ip;
                n_long  id_mask;
                char    id_data[1];
        } icmp_dun;
#define icmp_otime      icmp_dun.id_ts.its_otime
#define icmp_rtime      icmp_dun.id_ts.its_rtime
#define icmp_ttime      icmp_dun.id_ts.its_ttime
#define icmp_ip         icmp_dun.id_ip.idi_ip
#define icmp_mask       icmp_dun.id_mask
#define icmp_data       icmp_dun.id_data
};