traceroute.tproj/README

   1 Tue Dec 27 06:24:24 PST 1988
   2
   3 Traceroute is a system administrators utility to trace the route
   4 ip packets from the current system take in getting to some
   5 destination system.  See the comments at the front of the
   6 program for a description of its use.
   7
   8 This program
   9
  10  a) can only be run by root (it uses raw ip sockets).
  11
  12  b) REQUIRES A KERNEL MOD to the raw ip output code to run.
  13
  14 If you want to hack on your kernel, my modified version of the
  15 routine rip_output (in file /sys/netinet/raw_ip.c) is attached.
  16 This code may or may not resemble the code in your kernel.
  17 It may offer you a place to start but I make no promises.
  18 If you do hack your kernel, remember to test everything that uses
  19 raw ip sockets (e.g., ping and egpup/gated) & make sure they still
  20 work.  I wish you the best of luck and you're on your own.
  21
  22 If your system has the ttl bug mentioned in the source, you
  23 might want to fix it while you're in the kernel.  (This bug
  24 appears in all releases of BSD up to but not including 4.3tahoe.
  25 If your version of netinet/ip_icmp.c is any earlier than 7.3
  26 (April, '87), it has the bug.)  The fix is just to add the line
  27         ip->ip_ttl = MAXTTL;
  28 after the line
  29         ip->ip_src = t;
  30 (or anywhere before the call to icmp_send) in routine icmp_reflect.
  31
  32 If you're running this on a pre-4.3bsd system (e.g., Sun 3.x,
  33 Ultrix) that strips ip headers from icmp messages, add -DARCHAIC
  34 to CFLAGS in the Makefile.  Also note that rip_output contains
  35 a conditional for a 4.2/4.3 change in the location of a raw
  36 socket's protocol number.  I've checked this under 4.3 & Sun OS
  37 3.5 but you should double-check your system to make sure the
  38 appropriate branch of the #if is taken (check the line that
  39 assigned to ip->ip_p in your system's original rip_output).
  40
  41 A couple of awk programs to massage the traceroute output are
  42 included.  "mean.awk" and "median.awk" compute the mean and median
  43 time to each hop, respectively.  I've found that something like
  44
  45         traceroute -q 7 foo.somewhere >t
  46         awk -f median.awk t | graph
  47
  48 can give you a quick picture of the bad spots on a long
  49 path (median is usually a better noise filter than mean).
  50
  51 Enjoy.
  52
  53  - Van Jacobson (van@helios.ee.lbl.gov)
  54
  55 -------------------- rip_output from /sys/netinet/raw_ip.c
  56 rip_output(m, so)
  57         register struct mbuf *m;
  58         struct socket *so;
  59 {
  60         register struct ip *ip;
  61         int error;
  62         struct rawcb *rp = sotorawcb(so);
  63         struct sockaddr_in *sin;
  64 #if BSD>=43
  65         short proto = rp->rcb_proto.sp_protocol;
  66 #else
  67         short proto = so->so_proto->pr_protocol;
  68 #endif
  69         /*
  70          * if the protocol is IPPROTO_RAW, the user handed us a
  71          * complete IP packet.  Otherwise, allocate an mbuf for a
  72          * header and fill it in as needed.
  73          */
  74         if (proto != IPPROTO_RAW) {
  75                 /*
  76                  * Calculate data length and get an mbuf
  77                  * for IP header.
  78                  */
  79                 int len = 0;
  80                 struct mbuf *m0;
  81
  82                 for (m0 = m; m; m = m->m_next)
  83                         len += m->m_len;
  84
  85                 m = m_get(M_DONTWAIT, MT_HEADER);
  86                 if (m == 0) {
  87                         m = m0;
  88                         error = ENOBUFS;
  89                         goto bad;
  90                 }
  91                 m->m_off = MMAXOFF - sizeof(struct ip);
  92                 m->m_len = sizeof(struct ip);
  93                 m->m_next = m0;
  94
  95                 ip = mtod(m, struct ip *);
  96                 ip->ip_tos = 0;
  97                 ip->ip_off = 0;
  98                 ip->ip_p = proto;
  99                 ip->ip_len = sizeof(struct ip) + len;
 100                 ip->ip_ttl = MAXTTL;
 101         } else
 102                 ip = mtod(m, struct ip *);
 103
 104         if (rp->rcb_flags & RAW_LADDR) {
 105                 sin = (struct sockaddr_in *)&rp->rcb_laddr;
 106                 if (sin->sin_family != AF_INET) {
 107                         error = EAFNOSUPPORT;
 108                         goto bad;
 109                 }
 110                 ip->ip_src.s_addr = sin->sin_addr.s_addr;
 111         } else
 112                 ip->ip_src.s_addr = 0;
 113
 114         ip->ip_dst = ((struct sockaddr_in *)&rp->rcb_faddr)->sin_addr;
 115
 116 #if BSD>=43
 117         return (ip_output(m, rp->rcb_options, &rp->rcb_route,
 118            (so->so_options & SO_DONTROUTE) | IP_ALLOWBROADCAST));
 119 #else
 120         return (ip_output(m, (struct mbuf *)0, &rp->rcb_route,
 121            (so->so_options & SO_DONTROUTE) | IP_ALLOWBROADCAST));
 122 #endif
 123 bad:
 124         m_freem(m);
 125         return (error);
 126 }