Lorenzo Colitti | 313379e | 2013-07-11 01:07:11 +0900 | [diff] [blame] | 1 | <refentry id="tracepath"> |
| 2 | |
| 3 | <refmeta> |
| 4 | <refentrytitle>tracepath</refentrytitle> |
| 5 | <manvolnum>8</manvolnum> |
| 6 | <refmiscinfo>iputils-&snapshot;</refmiscinfo> |
| 7 | </refmeta> |
| 8 | |
| 9 | <refnamediv> |
| 10 | <refname>tracepath, tracepath6</refname> |
| 11 | <refpurpose> |
| 12 | traces path to a network host discovering MTU along this path</refpurpose> |
| 13 | </refnamediv> |
| 14 | |
| 15 | <refsynopsisdiv> |
| 16 | <cmdsynopsis> |
| 17 | <command>tracepath</command> |
| 18 | <arg choice="opt">-n</arg> |
| 19 | <arg choice="opt">-b</arg> |
| 20 | <arg choice="opt">-l <replaceable/pktlen/</arg> |
| 21 | <arg choice="opt">-m <replaceable/max_hops/</arg> |
| 22 | <arg choice="opt">-p <replaceable/port/</arg> |
| 23 | <arg choice="req"><replaceable/destination/</arg> |
| 24 | </cmdsynopsis> |
| 25 | </refsynopsisdiv> |
| 26 | |
| 27 | <refsect1><title>DESCRIPTION</title> |
| 28 | <para> |
| 29 | It traces path to <replaceable/destination/ discovering MTU along this path. |
| 30 | It uses UDP port <replaceable/port/ or some random port. |
| 31 | It is similar to <command/traceroute/, only does not require superuser |
| 32 | privileges and has no fancy options. |
| 33 | </para> |
| 34 | |
| 35 | <para> |
| 36 | <command/tracepath6/ is good replacement for <command/traceroute6/ |
| 37 | and classic example of application of Linux error queues. |
| 38 | The situation with IPv4 is worse, because commercial |
| 39 | IP routers do not return enough information in ICMP error messages. |
| 40 | Probably, it will change, when they will be updated. |
| 41 | For now it uses Van Jacobson's trick, sweeping a range |
| 42 | of UDP ports to maintain trace history. |
| 43 | </para> |
| 44 | </refsect1> |
| 45 | |
| 46 | <refsect1><title>OPTIONS</title> |
| 47 | <variablelist> |
| 48 | |
| 49 | <varlistentry> |
| 50 | <term><option/-n/</term> |
| 51 | <listitem><para> |
| 52 | Print primarily IP addresses numerically. |
| 53 | </para></listitem> |
| 54 | </varlistentry> |
| 55 | |
| 56 | <varlistentry> |
| 57 | <term><option/-b/</term> |
| 58 | <listitem><para> |
| 59 | Print both of host names and IP addresses. |
| 60 | </para></listitem> |
| 61 | </varlistentry> |
| 62 | |
| 63 | <varlistentry> |
| 64 | <term><option/-l/</term> |
| 65 | <listitem><para> |
| 66 | Sets the initial packet length to <replaceable/pktlen/ instead of |
| 67 | 65535 for <command/tracepath/ or 128000 for <command/tracepath6/. |
| 68 | </para></listitem> |
| 69 | </varlistentry> |
| 70 | |
| 71 | <varlistentry> |
| 72 | <term><option/-m</term> |
| 73 | <listitem><para> |
| 74 | Set maximum hops (or maximum TTLs) to <replaceable/max_hops/ |
| 75 | instead of 30. |
| 76 | </para></listitem> |
| 77 | </varlistentry> |
| 78 | |
| 79 | <varlistentry> |
| 80 | <term><option/-p/</term> |
| 81 | <listitem><para> |
| 82 | Sets the initial destination port to use. |
| 83 | </para></listitem> |
| 84 | </varlistentry> |
| 85 | </variablelist> |
| 86 | </refsect1> |
| 87 | |
| 88 | <refsect1><title>OUTPUT</title> |
| 89 | <para> |
| 90 | <literallayout> |
| 91 | root@mops:~ # tracepath6 3ffe:2400:0:109::2 |
| 92 | 1?: [LOCALHOST] pmtu 1500 |
| 93 | 1: dust.inr.ac.ru 0.411ms |
| 94 | 2: dust.inr.ac.ru asymm 1 0.390ms pmtu 1480 |
| 95 | 2: 3ffe:2400:0:109::2 463.514ms reached |
| 96 | Resume: pmtu 1480 hops 2 back 2 |
| 97 | </literallayout> |
| 98 | </para> |
| 99 | |
| 100 | <para> |
| 101 | The first column shows <literal/TTL/ of the probe, followed by colon. |
| 102 | Usually value of <literal/TTL/ is obtained from reply from network, |
| 103 | but sometimes reply does not contain necessary information and |
| 104 | we have to guess it. In this case the number is followed by ?. |
| 105 | </para> |
| 106 | |
| 107 | <para> |
| 108 | The second column shows the network hop, which replied to the probe. |
| 109 | It is either address of router or word <literal/[LOCALHOST]/, if |
| 110 | the probe was not sent to the network. |
| 111 | </para> |
| 112 | |
| 113 | <para> |
| 114 | The rest of line shows miscellaneous information about path to |
| 115 | the correspinding network hop. As rule it contains value of RTT. |
| 116 | Additionally, it can show Path MTU, when it changes. |
| 117 | If the path is asymmetric |
| 118 | or the probe finishes before it reach prescribed hop, difference |
| 119 | between number of hops in forward and backward direction is shown |
| 120 | following keyword <literal/async/. This information is not reliable. |
| 121 | F.e. the third line shows asymmetry of 1, it is because the first probe |
| 122 | with TTL of 2 was rejected at the first hop due to Path MTU Discovery. |
| 123 | </para> |
| 124 | |
| 125 | <para> |
| 126 | The last line summarizes information about all the path to the destination, |
| 127 | it shows detected Path MTU, amount of hops to the destination and our |
| 128 | guess about amount of hops from the destination to us, which can be |
| 129 | different when the path is asymmetric. |
| 130 | </para> |
| 131 | |
| 132 | </refsect1> |
| 133 | |
| 134 | |
| 135 | |
| 136 | |
| 137 | <refsect1><title>SEE ALSO</title> |
| 138 | <para> |
| 139 | <citerefentry><refentrytitle/traceroute/<manvolnum/8/</citerefentry>, |
| 140 | <link linkend="traceroute6"> |
| 141 | <citerefentry><refentrytitle/traceroute6/<manvolnum/8/</citerefentry></link>, |
| 142 | <link linkend="ping"> |
| 143 | <citerefentry><refentrytitle/ping/<manvolnum/8/</citerefentry></link>. |
| 144 | </para> |
| 145 | </refsect1> |
| 146 | |
| 147 | <refsect1><title>AUTHOR</title> |
| 148 | <para> |
| 149 | <command/tracepath/ was written by |
| 150 | <ulink url="mailto:kuznet@ms2.inr.ac.ru">Alexey Kuznetsov |
| 151 | <kuznet@ms2.inr.ac.ru></ulink>. |
| 152 | </para> |
| 153 | </refsect1> |
| 154 | |
| 155 | <refsect1><title>SECURITY</title> |
| 156 | <para> |
| 157 | No security issues. |
| 158 | </para> |
| 159 | <para> |
| 160 | This lapidary deserves to be elaborated. |
| 161 | <command/tracepath/ is not a privileged program, unlike |
| 162 | <command/traceroute/, <command/ping/ and other beasts of this kind. |
| 163 | <command/tracepath/ may be executed by everyone who has some access |
| 164 | to network, enough to send UDP datagrams to investigated destination |
| 165 | using given port. |
| 166 | </para> |
| 167 | </refsect1> |
| 168 | |
| 169 | <refsect1><title>AVAILABILITY</title> |
| 170 | <para> |
| 171 | <command/tracepath/ is part of <filename/iputils/ package |
| 172 | and the latest versions are available in source form at |
| 173 | <ulink url="http://www.skbuff.net/iputils/iputils-current.tar.bz2"> |
| 174 | http://www.skbuff.net/iputils/iputils-current.tar.bz2</ulink>. |
| 175 | </para> |
| 176 | </refsect1> |
| 177 | |
| 178 | <![IGNORE[ |
| 179 | <refsect1><title>COPYING</title> |
| 180 | <para> |
| 181 | <literallayout> |
| 182 | This documentation is free software; you can redistribute |
| 183 | it and/or modify it under the terms of the GNU General Public |
| 184 | License Version 2. |
| 185 | |
| 186 | This program is distributed in the hope that it will be |
| 187 | useful, but WITHOUT ANY WARRANTY; without even the implied |
| 188 | warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. |
| 189 | See the GNU General Public License for more details. |
| 190 | |
| 191 | For more details see the file COPYING in the source |
| 192 | distribution of Linux kernel of version 2.4. |
| 193 | </literallayout> |
| 194 | </para> |
| 195 | </refsect1> |
| 196 | ]]> |
| 197 | |
| 198 | |
| 199 | |
| 200 | |
| 201 | </refentry> |