127 lines
3.7 KiB
Plaintext
127 lines
3.7 KiB
Plaintext
Tue Dec 27 06:24:24 PST 1988
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Traceroute is a system administrators utility to trace the route
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ip packets from the current system take in getting to some
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destination system. See the comments at the front of the
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program for a description of its use.
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This program
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a) can only be run by root (it uses raw ip sockets).
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b) REQUIRES A KERNEL MOD to the raw ip output code to run.
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If you want to hack on your kernel, my modified version of the
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routine rip_output (in file /sys/netinet/raw_ip.c) is attached.
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This code may or may not resemble the code in your kernel.
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It may offer you a place to start but I make no promises.
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If you do hack your kernel, remember to test everything that uses
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raw ip sockets (e.g., ping and egpup/gated) & make sure they still
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work. I wish you the best of luck and you're on your own.
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If your system has the ttl bug mentioned in the source, you
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might want to fix it while you're in the kernel. (This bug
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appears in all releases of BSD up to but not including 4.3tahoe.
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If your version of netinet/ip_icmp.c is any earlier than 7.3
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(April, '87), it has the bug.) The fix is just to add the line
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ip->ip_ttl = MAXTTL;
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after the line
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ip->ip_src = t;
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(or anywhere before the call to icmp_send) in routine icmp_reflect.
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If you're running this on a pre-4.3bsd system (e.g., Sun 3.x,
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Ultrix) that strips ip headers from icmp messages, add -DARCHAIC
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to CFLAGS in the Makefile. Also note that rip_output contains
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a conditional for a 4.2/4.3 change in the location of a raw
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socket's protocol number. I've checked this under 4.3 & Sun OS
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3.5 but you should double-check your system to make sure the
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appropriate branch of the #if is taken (check the line that
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assigned to ip->ip_p in your system's original rip_output).
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A couple of awk programs to massage the traceroute output are
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included. "mean.awk" and "median.awk" compute the mean and median
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time to each hop, respectively. I've found that something like
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traceroute -q 7 foo.somewhere >t
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awk -f median.awk t | graph
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can give you a quick picture of the bad spots on a long
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path (median is usually a better noise filter than mean).
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Enjoy.
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- Van Jacobson (van@helios.ee.lbl.gov)
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-------------------- rip_output from /sys/netinet/raw_ip.c
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rip_output(m, so)
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register struct mbuf *m;
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struct socket *so;
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{
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register struct ip *ip;
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int error;
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struct rawcb *rp = sotorawcb(so);
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struct sockaddr_in *sin;
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#if BSD>=43
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short proto = rp->rcb_proto.sp_protocol;
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#else
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short proto = so->so_proto->pr_protocol;
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#endif
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/*
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* if the protocol is IPPROTO_RAW, the user handed us a
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* complete IP packet. Otherwise, allocate an mbuf for a
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* header and fill it in as needed.
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*/
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if (proto != IPPROTO_RAW) {
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/*
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* Calculate data length and get an mbuf
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* for IP header.
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*/
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int len = 0;
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struct mbuf *m0;
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for (m0 = m; m; m = m->m_next)
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len += m->m_len;
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m = m_get(M_DONTWAIT, MT_HEADER);
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if (m == 0) {
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m = m0;
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error = ENOBUFS;
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goto bad;
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}
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m->m_off = MMAXOFF - sizeof(struct ip);
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m->m_len = sizeof(struct ip);
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m->m_next = m0;
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ip = mtod(m, struct ip *);
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ip->ip_tos = 0;
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ip->ip_off = 0;
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ip->ip_p = proto;
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ip->ip_len = sizeof(struct ip) + len;
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ip->ip_ttl = MAXTTL;
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} else
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ip = mtod(m, struct ip *);
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if (rp->rcb_flags & RAW_LADDR) {
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sin = (struct sockaddr_in *)&rp->rcb_laddr;
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if (sin->sin_family != AF_INET) {
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error = EAFNOSUPPORT;
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goto bad;
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}
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ip->ip_src.s_addr = sin->sin_addr.s_addr;
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} else
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ip->ip_src.s_addr = 0;
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ip->ip_dst = ((struct sockaddr_in *)&rp->rcb_faddr)->sin_addr;
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#if BSD>=43
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return (ip_output(m, rp->rcb_options, &rp->rcb_route,
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(so->so_options & SO_DONTROUTE) | IP_ALLOWBROADCAST));
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#else
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return (ip_output(m, (struct mbuf *)0, &rp->rcb_route,
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(so->so_options & SO_DONTROUTE) | IP_ALLOWBROADCAST));
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#endif
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bad:
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m_freem(m);
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return (error);
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}
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