tcprules(1)						      General Commands Manual						       tcprules(1)

NAME

       tcprules - compile rules for tcpserver

SYNOPSIS

       tcprules rules.cdb rules.tmp

OVERVIEW

       tcpserver optionally follows rules to decide whether a TCP connection is acceptable.  For example, a rule of

	  18.23.0.32:deny

       prohibits connections from IP address 18.23.0.32.

       tcprules reads rules from its standard input and writes them into rules.cdb in a binary format suited for quick access by tcpserver.

       tcprules  can be used while tcpserver is running: it ensures that rules.cdb is updated atomically.  It does this by first writing the rules
       to rules.tmp and then moving rules.tmp on top of rules.cdb.  If rules.tmp already exists, it  is  destroyed.   The  directories	containing
       rules.cdb and rules.tmp must be writable to tcprules; they must also be on the same filesystem.

       If there is a problem with the input, tcprules complains and leaves rules.cdb alone.

       The binary rules.cdb format is portable across machines.

RULE FORMAT

       A rule takes up one line.  A file containing rules may also contain comments: lines beginning with # are ignored.

       Each  rule  contains an address, a colon, and a list of instructions, with no extra spaces.  When tcpserver receives a connection from that
       address, it follows the instructions.

ADDRESSES

       tcpserver starts by looking for a rule with address TCPREMOTEINFO@TCPREMOTEIP.  If it doesn't find one, or if TCPREMOTEINFO is not set,	it
       tries  the  address TCPREMOTEIP.  If that doesn't work, it tries shorter and shorter prefixes of TCPREMOTEIP ending with a dot.	If none of
       them work, it tries the empty string.

       For example, here are some rules:

	  joe@127.0.0.1:first
	  18.23.0.32:second
	  127.:third
	  :fourth
	  ::1:fifth

       If TCPREMOTEIP is 10.119.75.38, tcpserver will follow the fourth instructions.

       If TCPREMOTEIP is ::1, tcpserver will follow the fifth instructions.  Note that	you  cannot  detect  IPv4  mapped  addresses  by  matching
       "::ffff", as those addresses will be converted to IPv4 before looking at the rules.

       If TCPREMOTEIP is 18.23.0.32, tcpserver will follow the second instructions.

       If TCPREMOTEINFO is bill and TCPREMOTEIP is 127.0.0.1, tcpserver will follow the third instructions.

       If TCPREMOTEINFO is joe and TCPREMOTEIP is 127.0.0.1, tcpserver will follow the first instructions.

ADDRESS RANGES

       tcprules treats 1.2.3.37-53:ins as an abbreviation for the rules 1.2.3.37:ins, 1.2.3.38:ins, and so on up through 1.2.3.53:ins.	Similarly,
       10.2-3.:ins is an abbreviation for 10.2.:ins and 10.3.:ins.

INSTRUCTIONS

       The instructions in a rule must begin with either allow or deny.  deny tells tcpserver to drop the  connection  without	running  anything.
       For example, the rule

	  :deny

       tells tcpserver to drop all connections that aren't handled by more specific rules.

       The  instructions  may continue with some environment variables, in the format ,VAR="VALUE".  tcpserver adds VAR=VALUE to the current envi-
       ronment.  For example,

	  10.0.:allow,RELAYCLIENT="@fix.me"

       adds RELAYCLIENT=@fix.me to the environment.  The quotes here may be replaced by any repeated character:

	  10.0.:allow,RELAYCLIENT=/@fix.me/

       Any number of variables may be listed:

	  127.0.0.1:allow,RELAYCLIENT="",TCPLOCALHOST="movie.edu"

SEE ALSO

       tcprulescheck(1), tcpserver(1), tcp-environ(5)

																       tcprules(1)