~mdw / tripe / blame
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|---|---|---|
| c64d8cd5 MW |
1 | .\" -*-nroff-*- |
| 2 | .\" | |
| 3 | .\" Documentation for pathmtu | |
| 4 | .\" | |
| 5 | .\" (c) 2008 Straylight/Edgeware. | |
| 6 | .\" | |
| 7 | ||
| 8 | .\"----- Licensing notice --------------------------------------------------- | |
| 9 | .\" | |
| 10 | .\" This file is part of Trivial IP Encryption (TrIPE). | |
| 11 | .\" | |
| 12 | .\" TrIPE is free software; you can redistribute it and/or modify | |
| 13 | .\" it under the terms of the GNU General Public License as published by | |
| 14 | .\" the Free Software Foundation; either version 2 of the License, or | |
| 15 | .\" (at your option) any later version. | |
| 16 | .\" | |
| 17 | .\" TrIPE is distributed in the hope that it will be useful, | |
| 18 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 19 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 20 | .\" GNU General Public License for more details. | |
| 21 | .\" | |
| 22 | .\" You should have received a copy of the GNU General Public License | |
| 23 | .\" along with TrIPE; if not, write to the Free Software Foundation, | |
| 24 | .\" Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
| 25 | . | |
| 26 | .\"-------------------------------------------------------------------------- | |
| e99aedcf | 27 | .so ../common/defs.man \" @@@PRE@@@ |
| c64d8cd5 MW |
28 | . |
| 29 | .\"-------------------------------------------------------------------------- | |
| 30 | .TH pathmtu 1 "29 December 2008" "Straylight/Edgeware" "TrIPE: Trivial IP Encryption" | |
| 31 | . | |
| 32 | .\"-------------------------------------------------------------------------- | |
| 33 | .SH "NAME" | |
| 34 | . | |
| 35 | pathmtu \- discover path MTU to a given host | |
| 36 | . | |
| 37 | .\"-------------------------------------------------------------------------- | |
| 38 | .SH "SYNOPSIS" | |
| 39 | . | |
| 40 | .B pathmtu | |
| 41 | .RB [ \-t | |
| 42 | .IR timeout ] | |
| 43 | .RB [ \-H | |
| 44 | .IR header ] | |
| 45 | .I host | |
| 46 | .RI [ port ] | |
| 47 | . | |
| 48 | .\"-------------------------------------------------------------------------- | |
| 49 | .SH "DESCRIPTION" | |
| 50 | . | |
| 51 | The | |
| 52 | .B pathmtu | |
| 53 | program discovers the size of the largest IP packet which can be sent to | |
| 54 | a given | |
| 55 | .I host | |
| 56 | (specified as a dotted-quad IP address or host name) without being | |
| 57 | fragmented. This is useful information, particularly when setting up | |
| 58 | VPN tunnel interfaces. | |
| 59 | .PP | |
| 60 | The program works by sending UDP packets and finding out whether they | |
| 61 | get fragmented. The packets are sent to a specified | |
| 62 | .I port | |
| 63 | (specified as a number or service name) on the destination host. The | |
| 64 | destination does not need to be listening on the given port \(en indeed, | |
| 65 | it doesn't matter if the port is firewalled. The default port is 7 | |
| 66 | (echo), chosen because if it is active, we'll get an answer. | |
| 67 | .PP | |
| 68 | If the local host or some intermediate router is configured to drop ICMP | |
| 69 | fragmentation-required errors then the discovery attempt will silently | |
| 70 | fail. It is likely that TCP connections with the destination host will | |
| 71 | fail in unexpected ways if this is the case. Don't drop | |
| 72 | fragmentation-required errors! | |
| 73 | .PP | |
| 74 | Command-line options are as follows. | |
| 75 | .TP | |
| 76 | .B "\-h, \-\-help" | |
| 77 | Writes a brief description of the command-line options available to | |
| 78 | standard output and exits with status 0. | |
| 79 | .TP | |
| 80 | .B "\-v, \-\-version" | |
| 81 | Writes tripe's version number to standard output and exits with status | |
| 82 | 0. | |
| 83 | .TP | |
| 84 | .B "\-u, \-\-usage" | |
| 85 | Writes a brief usage summary to standard output and exits with status 0. | |
| 86 | .TP | |
| 87 | .BI "\-t, \-\-timeout=" timeout | |
| 88 | Sets the time to wait for a reply, in seconds. If no reply or error is | |
| 89 | received within the timeout, it is assumed that the attempt to send a | |
| 90 | packet was successful. The timeout can be fractional; the default is | |
| 91 | five seconds. | |
| 92 | .TP | |
| 93 | .BI "\-H, \-\-header=" header | |
| 94 | Sets the packet header, in hexadecimal. If you set an explicit port | |
| 95 | number, it may be worth setting the packet header too, so as not to | |
| 96 | alarm anything which might be listening on that port. The default | |
| 97 | packet contents are a fixed pseudorandomly-generated block of data. | |
| 98 | . | |
| 99 | .\"-------------------------------------------------------------------------- | |
| 100 | .SH "BUGS" | |
| 101 | . | |
| 102 | The | |
| 103 | .B pathmtu | |
| 104 | program currently only works on Linux. Code for other operating systems | |
| 105 | is welcome. | |
| 106 | . | |
| 107 | .\"-------------------------------------------------------------------------- | |
| 108 | .SH "AUTHOR" | |
| 109 | . | |
| 110 | Mark Wooding, <mdw@distorted.org.uk> | |
| 111 | . | |
| 112 | .\"----- That's all, folks -------------------------------------------------- |