<html> <head> <title>ipsvd-instruct(5) manual page</title> </head> <body bgcolor='white'> <a href='http://smarden.org/pape/'>G. Pape</a><br><a href='index.html'>ipsvd</a><hr> <h2><a name='sect0'>Name</a></h2> ipsvd-instruct - format of the <i>ipsvd(8)</i> instructions directory <h2><a name='sect1'>Description</a></h2> The internet protocol service daemons, <i><b>ipsvd</b>(7)</i>, can be told to read and follow instructions from a directory on incoming connections to the socket they listen on. <p> For mostly static instructions or for performance reasons, it is possible to compile the instructions from a directory into a constant database (cdb) with <i><b>ipsvd-cdb</b>(8)</i> for faster lookup, and to tell <i><b>ipsvd</b>(7)</i> to read the instructions from there. <h2><a name='sect2'>Matching</a></h2> On each incoming connection, the <i><b>ipsvd</b>(7)</i> matches the client’s IP address against files in the instructions directory. For example, the IP address <i>a.b.c.d</i> which reverse resolves to <i>moa.bit.smarden.org</i> is matched against the following files in the instructions directory, in this order, first match wins: <ol> .<li><i>a.b.c.d</i> </li>.<li><i>a.b.c</i> </li>.<li><i>a.b</i> </li>.<li><i>a</i> </li> </ol> <p> If the client’s hostname has been successfully looked up in DNS: <ol> .<li><i>moa.bit.smarden.org</i> </li>.<li><i>bit.smarden.org</i> </li>.<li><i>smarden.org</i> </li>.<li><i>org</i> </li> </ol> <p> And finally the catchall file ‘‘0’’ (zero): <ol> .<li><i>0</i> </li> </ol> <p> After successfully matching a client’s IP address or hostname against the instructions directory, <i><b>ipsvd</b>(7)</i> examines the file that matched the IP address or hostname, and acts accordingly: <ol> .<li>If neither the user’s read permission, nor the user’s execute permission is set for the file, the connection is closed immediately. </li>.<li>If the file has the user’s execute permission set, <i><b>ipsvd</b>(7)</i> reads the contents of the file and runs <i>/bin/sh</i> -c ’<contents>’ instead of the default program <i>prog</i> given at the command line for this connection. </li>.<li>If the file has the user’s read permission set, <i><b>ipsvd</b>(7)</i> reads the contents of the file and interprets each line as an instruction for this connection (see below). </li> </ol> <p> If the client’s IP address or hostname doesn’t match any file in the instructions directory, the default action is taken (the program <i>prog</i> is run to handle the connection). <h2><a name='sect3'>Instructions</a></h2> If <i><b>ipsvd</b>(7)</i> is given instructions for an incoming connection, it reads the corresponding file and interprets each line as follows. The file may be empty, meaning that there is no special instruction. <dl> <dt><b>+</b><i>VAR=VALUE</i> </dt> <dd>environment. If the line starts with a plus (‘‘+’’), and the string following the plus contains a ‘‘=’’, <i><b>ipsvd</b>(7)</i> puts the string following the plus into the environment before starting <i>prog</i> to handle the connection. If the string following the plus doesn’t contain a ‘‘=’’, <i><b>ipsvd</b>(7)</i> makes sure that the environment variable with the name string is not set. </dd> <dt><b>C</b><i>num[:<i>msg</i>]</i> </dt> <dd>concurrency. If the line starts with a ‘‘C’’, and is followed by a number, the per host concurrency limit for the IP address that initiated the connection is set to this number. If <i>num</i> is zero, per host concurrency limit is disabled. If <i>num</i> is followed by ‘‘:<i>msg’’,</i> the message <i>msg</i> is written to this client if possible, if the per host concurrency limit is reached. <p> <i>msg</i> may contain backslash-escaped characters as follows: ‘‘\\’’ is converted to a single backslash, ‘‘\n’’ is converted to a new line character, and ‘‘\r’’ is converted to a carriage return. <p> On multiple concurrency instructions the last processed concurrency instruction is considered. Not all <i><b>ipsvd</b>(7)</i>’s support per host concurrency. </dd> <dt><b>=</b><i>hostname[:<i>forward</i>]</i> </dt> <dd>check hostname. If the line starts with a ‘‘=’’, and is followed by a hostname, <i><b>ipsvd</b>(7)</i> looks up the IP addresses for <i>hostname</i> in DNS and checks if the client’s IP address matches one of these IP addresses. If so, <i><i>ipsvd</i>(7)</i> stops processing the instructions here and runs <i>prog</i>. If <i>hostname</i> is followed a colon and <i>forward</i>, <i><b>ipsvd</b>(7)</i> now examines the file <i>forward</i> and acts accordingly, instead of running <i>prog</i>. All check hostname instructions in <i>forward</i> are ignored. If <i>forward</i> does not exist, the connection is closed. <p> <i>hostname</i> may be ‘‘0’’ (zero), matching any IP address. <p> Note: Using check hostname instructions can cause significant delay while responding to connection attempts, caused by DNS lookups. </dd> </dl> <p> If <i><b>ipsvd</b>(7)</i> cannot interpret a line, it prints a warning, discards the line, and continues with the next instruction if any. <p> After processing all instructions, <i><b>ipsvd</b>(7)</i> runs <i>prog</i>. If the file contains at least one check hostname instruction, and none was successful, it closes the connection instead of running <i>prog</i>. <h2><a name='sect4'>Example Instructions</a></h2> <dl> <dt>+MEMORY=20000 </dt> <dd>This instruction causes the environment variable ‘‘MEMORY’’ with the value ‘‘20000’’ to be available to the program <i>prog</i> that handles the connection. </dd> <dt>+DEBUG= </dt> <dd>This instruction adds the variable ‘‘DEBUG’’ with an empty value to the environment. </dd> <dt>+LOGNAME </dt> <dd>This instructions makes sure that the environment variable ‘‘LOGNAME’’ is unset when running <i>prog</i>. </dd> <dt>C16 </dt> <dd>Set the per host concurrency to 16. A connection will be closed silently if there are already 16 active connections from this client’s IP address. </dd> <dt>=floyd.dyn.smarden.org:127.0.0.1 </dt> <dd>Check IP address of the dynamic hostname <i>floyd.dyn.smarden.org</i>. If one of the IP addresses <i>floyd.dyn.smarden.org</i> currently resolves to matches the client’s IP address, handle the connection through the file <i>127.0.0.1</i> in the instructions directory. </dd> </dl> <h2><a name='sect5'>See Also</a></h2> <i>ipsvd(7)</i>, <i>ipsvd-cdb(8)</i>, <i>tcpsvd(8)</i>, <i>sslsvd(8)</i>, <i>udpsvd(8)</i>, <i>sslio(8)</i> <p> <i>http://smarden.org/ipsvd/</i> <h2><a name='sect6'>Author</a></h2> Gerrit Pape <pape@smarden.org> <p> <hr><p> <a name='toc'><b>Table of Contents</b></a><p> <ul> <li><a name='toc0' href='#sect0'>Name</a></li> <li><a name='toc1' href='#sect1'>Description</a></li> <li><a name='toc2' href='#sect2'>Matching</a></li> <li><a name='toc3' href='#sect3'>Instructions</a></li> <li><a name='toc4' href='#sect4'>Example Instructions</a></li> <li><a name='toc5' href='#sect5'>See Also</a></li> <li><a name='toc6' href='#sect6'>Author</a></li> </ul> </body> </html>
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