tping.c - plan9port - [fork] Plan 9 from user space
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       ---
       tping.c (1890B)
       ---
            1 #include <u.h>
            2 #include <libc.h>
            3 #include <ip.h>
            4 
            5 
            6 typedef struct Icmp Icmp;
            7 struct Icmp
            8 {
            9         uchar        vihl;                /* Version and header length */
           10         uchar        tos;                /* Type of service */
           11         uchar        length[2];        /* packet length */
           12         uchar        id[2];                /* Identification */
           13         uchar        frag[2];        /* Fragment information */
           14         uchar        ttl;                /* Time to live */
           15         uchar        proto;                /* Protocol */
           16         uchar        ipcksum[2];        /* Header checksum */
           17         uchar        src[4];                /* Ip source */
           18         uchar        dst[4];                /* Ip destination */
           19         uchar        type;
           20         uchar        code;
           21         uchar        cksum[2];
           22         uchar        icmpid[2];
           23         uchar        seq[2];
           24         uchar        data[1];
           25 };
           26 
           27 enum
           28 {                        /* Packet Types */
           29         EchoReply        = 0,
           30         Unreachable        = 3,
           31         SrcQuench        = 4,
           32         EchoRequest        = 8,
           33         TimeExceed        = 11,
           34         Timestamp        = 13,
           35         TimestampReply        = 14,
           36         InfoRequest        = 15,
           37         InfoReply        = 16,
           38 
           39         ICMP_IPSIZE        = 20,
           40         ICMP_HDRSIZE        = 8
           41 };
           42 
           43 static void
           44 catch(void *a, char *msg)
           45 {
           46         USED(a);
           47         if(strstr(msg, "alarm"))
           48                 noted(NCONT);
           49         else
           50                 noted(NDFLT);
           51 }
           52 
           53 #define MSG "dhcp probe"
           54 
           55 /*
           56  *  make sure noone is using the address
           57  */
           58 int
           59 icmpecho(uchar *a)
           60 {
           61         int fd;
           62         char buf[512];
           63         Icmp *ip;
           64         int i, n, len;
           65         ushort sseq, x;
           66         int rv;
           67 
           68 return 0;
           69         rv = 0;
           70 
           71         sprint(buf, "%I", a);
           72         fd = dial(netmkaddr(buf, "icmp", "1"), 0, 0, 0);
           73         if(fd < 0){
           74                 return 0;
           75         }
           76 
           77         sseq = getpid()*time(0);
           78 
           79         ip = (Icmp*)buf;
           80         notify(catch);
           81         for(i = 0; i < 3; i++){
           82                 ip->type = EchoRequest;
           83                 ip->code = 0;
           84                 strcpy((char*)ip->data, MSG);
           85                 ip->seq[0] = sseq;
           86                 ip->seq[1] = sseq>>8;
           87                 len = ICMP_IPSIZE+ICMP_HDRSIZE+sizeof(MSG);
           88 
           89                 /* send a request */
           90                 if(write(fd, buf, len) < len)
           91                         break;
           92 
           93                 /* wait 1/10th second for a reply and try again */
           94                 alarm(100);
           95                 n = read(fd, buf, sizeof(buf));
           96                 alarm(0);
           97                 if(n <= 0)
           98                         continue;
           99 
          100                 /* an answer to our echo request? */
          101                 x = (ip->seq[1]<<8)|ip->seq[0];
          102                 if(n >= len)
          103                 if(ip->type == EchoReply)
          104                 if(x == sseq)
          105                 if(strcmp((char*)ip->data, MSG) == 0){
          106                         rv = 1;
          107                         break;
          108                 }
          109         }
          110         close(fd);
          111         return rv;
          112 }