+.\" This manpage has been automatically generated by docbook2man
+.\" from a DocBook document. This tool can be found at:
+.\" <http://shell.ipoline.com/~elmert/comp/docbook2X/>
+.\" Please send any bug reports, improvements, comments, patches,
+.\" etc. to Steve Cheng <steve@ggi-project.org>.
+.TH "TRACEPATH" "8" "07 May 2014" "iputils-121221" "System Manager's Manual: iputils"
+.SH NAME
+tracepath, tracepath6 \- traces path to a network host discovering MTU along this path
+.SH SYNOPSIS
+
+\fBtracepath\fR [\fB-n\fR] [\fB-b\fR] [\fB-l \fIpktlen\fB\fR] [\fB-m \fImax_hops\fB\fR] [\fB-p \fIport\fB\fR] \fB\fIdestination\fB\fR
+
+.SH "DESCRIPTION"
+.PP
+It traces path to \fIdestination\fR discovering MTU along this path.
+It uses UDP port \fIport\fR or some random port.
+It is similar to \fBtraceroute\fR, only does not require superuser
+privileges and has no fancy options.
+.PP
+\fBtracepath6\fR is good replacement for \fBtraceroute6\fR
+and classic example of application of Linux error queues.
+The situation with IPv4 is worse, because commercial
+IP routers do not return enough information in ICMP error messages.
+Probably, it will change, when they will be updated.
+For now it uses Van Jacobson's trick, sweeping a range
+of UDP ports to maintain trace history.
+.SH "OPTIONS"
+.TP
+\fB-n\fR
+Print primarily IP addresses numerically.
+.TP
+\fB-b\fR
+Print both of host names and IP addresses.
+.TP
+\fB-l\fR
+Sets the initial packet length to \fIpktlen\fR instead of
+65535 for \fBtracepath\fR or 128000 for \fBtracepath6\fR.
+.TP
+\fB-m/term> \fR
+Set maximum hops (or maximum TTLs) to \fImax_hops\fR
+instead of 30.
+.TP
+\fB-p\fR
+Sets the initial destination port to use.
+.SH "OUTPUT"
+.PP
+
+.nf
+root@mops:~ # tracepath6 3ffe:2400:0:109::2
+ 1?: [LOCALHOST] pmtu 1500
+ 1: dust.inr.ac.ru 0.411ms
+ 2: dust.inr.ac.ru asymm 1 0.390ms pmtu 1480
+ 2: 3ffe:2400:0:109::2 463.514ms reached
+ Resume: pmtu 1480 hops 2 back 2
+.fi
+.PP
+The first column shows TTL of the probe, followed by colon.
+Usually value of TTL is obtained from reply from network,
+but sometimes reply does not contain necessary information and
+we have to guess it. In this case the number is followed by ?.
+.PP
+The second column shows the network hop, which replied to the probe.
+It is either address of router or word [LOCALHOST], if
+the probe was not sent to the network.
+.PP
+The rest of line shows miscellaneous information about path to
+the correspinding network hop. As rule it contains value of RTT.
+Additionally, it can show Path MTU, when it changes.
+If the path is asymmetric
+or the probe finishes before it reach prescribed hop, difference
+between number of hops in forward and backward direction is shown
+following keyword async. This information is not reliable.
+F.e. the third line shows asymmetry of 1, it is because the first probe
+with TTL of 2 was rejected at the first hop due to Path MTU Discovery.
+.PP
+The last line summarizes information about all the path to the destination,
+it shows detected Path MTU, amount of hops to the destination and our
+guess about amount of hops from the destination to us, which can be
+different when the path is asymmetric.
+.SH "SEE ALSO"
+.PP
+\fBtraceroute\fR(8),
+\fBtraceroute6\fR(8),
+\fBping\fR(8).
+.SH "AUTHOR"
+.PP
+\fBtracepath\fR was written by
+Alexey Kuznetsov
+<kuznet@ms2.inr.ac.ru>.
+.SH "SECURITY"
+.PP
+No security issues.
+.PP
+This lapidary deserves to be elaborated.
+\fBtracepath\fR is not a privileged program, unlike
+\fBtraceroute\fR, \fBping\fR and other beasts of this kind.
+\fBtracepath\fR may be executed by everyone who has some access
+to network, enough to send UDP datagrams to investigated destination
+using given port.
+.SH "AVAILABILITY"
+.PP
+\fBtracepath\fR is part of \fIiputils\fR package
+and the latest versions are available in source form at
+http://www.skbuff.net/iputils/iputils-current.tar.bz2.
~mdw / termux-packages / commitdiff