| 1 | .\" -*-nroff-*- |
| 2 | .\" |
| 3 | .\" Documentation for uslip |
| 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 | .\"-------------------------------------------------------------------------- |
| 27 | .so ../common/defs.man \" @@@PRE@@@ |
| 28 | . |
| 29 | .\"-------------------------------------------------------------------------- |
| 30 | .TH tripe-uslip 1 "7 April 2008" "Straylight/Edgeware" "TrIPE: Trivial IP Encryption" |
| 31 | . |
| 32 | .\"-------------------------------------------------------------------------- |
| 33 | .SH "NAME" |
| 34 | . |
| 35 | tripe-uslip \- fake SLIP interface for testing tripe |
| 36 | . |
| 37 | .\"-------------------------------------------------------------------------- |
| 38 | .SH "SYNOPSIS" |
| 39 | . |
| 40 | .B tripe-uslip |
| 41 | .RB [ \-fgps ] |
| 42 | .I socket |
| 43 | . |
| 44 | .\"-------------------------------------------------------------------------- |
| 45 | .SH "DESCRIPTION" |
| 46 | . |
| 47 | The |
| 48 | .B tripe-uslip |
| 49 | provides a mechanism for pushing packets of data into a |
| 50 | .BR tripe (8) |
| 51 | server, and extracting them. This is useful for testing the server; it |
| 52 | isn't useful in a production environment. |
| 53 | .SS "Overview and theory of operation" |
| 54 | Testing the |
| 55 | .BR tripe (8) |
| 56 | server is difficult: configuring network interfaces and creating tunnels |
| 57 | requires root privileges (undesirable for a program under development!) |
| 58 | and testing that it successfully transports network packets needs two |
| 59 | separate instances running on separate machines. (If both ends of a |
| 60 | tunnel are on the same host then the packets won't actually go over the |
| 61 | tunnel: the kernel will just loop them back internally.) |
| 62 | .PP |
| 63 | The |
| 64 | .B tripe-uslip |
| 65 | program implements the interface required of a dynamic allocation script |
| 66 | (see the |
| 67 | .BR tripe (8) |
| 68 | manual for details). However, it doesn't actually make a network |
| 69 | interface. |
| 70 | .PP |
| 71 | You use it by setting |
| 72 | .IP |
| 73 | .BI TRIPE_SLIPIF= dir /tripe-uslip |
| 74 | .PP |
| 75 | in the environment passed to the |
| 76 | .BR tripe (8) |
| 77 | server (and, typically, passing it the |
| 78 | .B \-tslip |
| 79 | command-line option). When you add a new peer with the |
| 80 | .B ADD |
| 81 | .I peer |
| 82 | .IR address ... |
| 83 | administration command, the server runs |
| 84 | .IB dir /tripe-uslip |
| 85 | .IR peer , |
| 86 | which in turn creates a Unix-domain socket called |
| 87 | .I peer |
| 88 | in the server's current directory. If you run |
| 89 | .IP |
| 90 | .B tripe-uslip |
| 91 | .B \-p |
| 92 | .I peer |
| 93 | .BI < file |
| 94 | .PP |
| 95 | in this directory, then the contents of |
| 96 | .I file |
| 97 | are sent to |
| 98 | .B tripe |
| 99 | as if they were a network packet to be encrypted and transmitted over |
| 100 | its tunnel. (Any method of providing the data on standard input is |
| 101 | acceptable: it doesn't have to be a regular file. In particular, pipes |
| 102 | are fine. Note also that |
| 103 | .B tripe |
| 104 | doesn't actually care that the data it receives is actually network |
| 105 | packets: it can be absolutely anything you like.) |
| 106 | .PP |
| 107 | If you run |
| 108 | .IP |
| 109 | .B tripe-uslip |
| 110 | .B \-g |
| 111 | .I peer |
| 112 | .BI > file |
| 113 | .PP |
| 114 | then the contents of the next network packet the server decrypts will be |
| 115 | written to the |
| 116 | .IR file . |
| 117 | (Again, you can use pipes or whatever.) |
| 118 | .PP |
| 119 | The |
| 120 | .B tripe-uslip |
| 121 | program is fully nonblocking. This means that you won't deadlock the |
| 122 | server by attaching duff scripts to it via |
| 123 | .BR tripe-uslip . |
| 124 | .SS "Technical details" |
| 125 | Without options, |
| 126 | .B tripe-uslip |
| 127 | performs the following actions. |
| 128 | .hP \*o |
| 129 | It creates a Unix-domain socket with name |
| 130 | .I socket |
| 131 | (which will typically be the name of the peer that |
| 132 | .BR tripe (8) |
| 133 | created this interface for). |
| 134 | .hP \*o |
| 135 | It writes the string |
| 136 | .BI tripe-uslip- socket |
| 137 | to its standard output, followed by a newline. |
| 138 | .hP \*o |
| 139 | It reads and discards up to two bytes with value 192 (SLIP |
| 140 | .BR END ) |
| 141 | on stdin. |
| 142 | .hP \*o |
| 143 | It enters its main loop, during which it accepts and processes client |
| 144 | connections, and reads and writes SLIP-encoded packets on standard input |
| 145 | and output. Unless a fatal error occurs, the main loop continues until |
| 146 | it (a) has no connected clients, (b) has no packets queued for output to |
| 147 | clients or to standard output, and (c) has seen end-of-file on its |
| 148 | standard input. |
| 149 | .PP |
| 150 | The main loop works as follows. When a SLIP-encoded packet arrives on |
| 151 | standard input, it is decoded and placed on a queue waiting to be read |
| 152 | from a client. If a client connects and writes a packet, the packet is |
| 153 | SLIP-encoded and written to standard output. |
| 154 | .PP |
| 155 | Clients connecting to the |
| 156 | Unix-domain socket send an initial character |
| 157 | .RB ` < ' |
| 158 | to read a packet or |
| 159 | .RB ` > ' |
| 160 | to write. Packets, as far as clients are concerned, consist of |
| 161 | uninterpreted strings of octets and continue until end-of-file. It is |
| 162 | not possible to read or write more than one packet in a single connection. |
| 163 | .PP |
| 164 | The command-line options allow |
| 165 | .B tripe-uslip |
| 166 | to be used from scripts to inject or collect packets. They are as follows. |
| 167 | .TP |
| 168 | .B \-g, \-\-get |
| 169 | Connect to |
| 170 | .IR socket , |
| 171 | read a packet from the socket and write it to standard output. |
| 172 | .TP |
| 173 | .B \-p, \-\-put |
| 174 | Connect to |
| 175 | .IR socket , |
| 176 | read a packet from standard input and write it to the socket. |
| 177 | .TP |
| 178 | .B \-f, \-\-flood |
| 179 | Connect to |
| 180 | .IR socket , |
| 181 | and send packets as fast as possible. The packets sent aren't very |
| 182 | interesting, and there's no way to configure their contents. |
| 183 | .TP |
| 184 | .B \-s, \-\-sink |
| 185 | Connect to |
| 186 | .IR socket |
| 187 | and read packets as the become available. The packets are discarded, |
| 188 | though if stdout is a terminal, a simple spinning-baton animation is |
| 189 | updated once for each group of packets. If you are flooding one end of |
| 190 | a TrIPE connection, it's advisable to attach a sink to the other: |
| 191 | otherwise the destination |
| 192 | .B tripe-uslip |
| 193 | will attempt to consume all available memory, storing incoming packets |
| 194 | until someone retrieves them. |
| 195 | . |
| 196 | .\"-------------------------------------------------------------------------- |
| 197 | .SH "BUGS" |
| 198 | . |
| 199 | The |
| 200 | .B tripe-uslip |
| 201 | program is intended as a tool for testing the |
| 202 | .BR tripe (8) |
| 203 | server. It is not expected to be useful in production environments. In |
| 204 | particular, it intentionally imposes no limits on queue lengths or |
| 205 | packet sizes, and its internals and interface (one packet per client |
| 206 | connection) are not well-suited for high performance. That said, the |
| 207 | flood option has worked well enough to expose bugs in |
| 208 | .BR tripe 's |
| 209 | behaviour under heavy loads. |
| 210 | .PP |
| 211 | If |
| 212 | .B tripe-uslip |
| 213 | turns out to be useful in other contexts then it might be improved. |
| 214 | Patches are, of course, welcome. |
| 215 | .PP |
| 216 | The initial ignoring of |
| 217 | .B END |
| 218 | bytes is unpleasant but necessary to cope with the |
| 219 | .BR tripe (8) |
| 220 | server, which sends this sequence in order to ensure that it's properly |
| 221 | synchronized with the SLIP interface. |
| 222 | . |
| 223 | .\"-------------------------------------------------------------------------- |
| 224 | .SH "SEE ALSO" |
| 225 | . |
| 226 | .BR tripe (8). |
| 227 | . |
| 228 | .\"-------------------------------------------------------------------------- |
| 229 | .SH "AUTHOR" |
| 230 | . |
| 231 | Mark Wooding, <mdw@distorted.org.uk> |
| 232 | . |
| 233 | .\"----- That's all, folks -------------------------------------------------- |