#define ICMP_ECHOREPLY          0 #define ICMP_ECHO               8#define ICMP_MINLEN             8struct 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};