ソースコード
(21/22)

for (ttl = 1; ttl <= max_ttl; ++ttl) {

    ...
    for (probe = 0; probe < nprobes; ++probe) {

        ...
        send_probe(++seq, ttl);

        ...
        while ((cc = wait_for_reply(icmp_sock, &from, reset_timer)) != 0) {

           ...
           if ((i = packet_ok(packet, cc, &from, seq, &t1))) {

              ...
              switch(i - 1) {
              case ICMPV6_PORT_UNREACH:
                   ++got_there;
                   break;
              case ICMPV6_NOROUTE:
                   ++unreachable;
                   Printf(" !N");
                   break;

              ...