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Annotation of 43BSDReno/usr.sbin/traceroute/README, revision 1.1

1.1     ! root        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 ([email protected])
        !            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: }

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