--- /dev/null
+.\" -*-nroff-*-
+.\"
+.\" Documentation for pathmtu
+.\"
+.\" (c) 2008 Straylight/Edgeware.
+.\"
+
+.\"----- Licensing notice ---------------------------------------------------
+.\"
+.\" This file is part of Trivial IP Encryption (TrIPE).
+.\"
+.\" TrIPE is free software; you can redistribute it and/or modify
+.\" it under the terms of the GNU General Public License as published by
+.\" the Free Software Foundation; either version 2 of the License, or
+.\" (at your option) any later version.
+.\"
+.\" TrIPE is distributed in the hope that it will be useful,
+.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
+.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+.\" GNU General Public License for more details.
+.\"
+.\" You should have received a copy of the GNU General Public License
+.\" along with TrIPE; if not, write to the Free Software Foundation,
+.\" Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+.
+.\"--------------------------------------------------------------------------
+.so ../defs.man.in \" @@@PRE@@@
+.
+.\"--------------------------------------------------------------------------
+.TH pathmtu 1 "29 December 2008" "Straylight/Edgeware" "TrIPE: Trivial IP Encryption"
+.
+.\"--------------------------------------------------------------------------
+.SH "NAME"
+.
+pathmtu \- discover path MTU to a given host
+.
+.\"--------------------------------------------------------------------------
+.SH "SYNOPSIS"
+.
+.B pathmtu
+.RB [ \-t
+.IR timeout ]
+.RB [ \-H
+.IR header ]
+.I host
+.RI [ port ]
+.
+.\"--------------------------------------------------------------------------
+.SH "DESCRIPTION"
+.
+The
+.B pathmtu
+program discovers the size of the largest IP packet which can be sent to
+a given
+.I host
+(specified as a dotted-quad IP address or host name) without being
+fragmented. This is useful information, particularly when setting up
+VPN tunnel interfaces.
+.PP
+The program works by sending UDP packets and finding out whether they
+get fragmented. The packets are sent to a specified
+.I port
+(specified as a number or service name) on the destination host. The
+destination does not need to be listening on the given port \(en indeed,
+it doesn't matter if the port is firewalled. The default port is 7
+(echo), chosen because if it is active, we'll get an answer.
+.PP
+If the local host or some intermediate router is configured to drop ICMP
+fragmentation-required errors then the discovery attempt will silently
+fail. It is likely that TCP connections with the destination host will
+fail in unexpected ways if this is the case. Don't drop
+fragmentation-required errors!
+.PP
+Command-line options are as follows.
+.TP
+.B "\-h, \-\-help"
+Writes a brief description of the command-line options available to
+standard output and exits with status 0.
+.TP
+.B "\-v, \-\-version"
+Writes tripe's version number to standard output and exits with status
+0.
+.TP
+.B "\-u, \-\-usage"
+Writes a brief usage summary to standard output and exits with status 0.
+.TP
+.BI "\-t, \-\-timeout=" timeout
+Sets the time to wait for a reply, in seconds. If no reply or error is
+received within the timeout, it is assumed that the attempt to send a
+packet was successful. The timeout can be fractional; the default is
+five seconds.
+.TP
+.BI "\-H, \-\-header=" header
+Sets the packet header, in hexadecimal. If you set an explicit port
+number, it may be worth setting the packet header too, so as not to
+alarm anything which might be listening on that port. The default
+packet contents are a fixed pseudorandomly-generated block of data.
+.
+.\"--------------------------------------------------------------------------
+.SH "BUGS"
+.
+The
+.B pathmtu
+program currently only works on Linux. Code for other operating systems
+is welcome.
+.
+.\"--------------------------------------------------------------------------
+.SH "AUTHOR"
+.
+Mark Wooding, <mdw@distorted.org.uk>
+.
+.\"----- That's all, folks --------------------------------------------------
~mdw / tripe / blobdiff