ipsvd-instruct(5)						File Formats Manual						 ipsvd-instruct(5)

NAME

       ipsvd-instruct - format of the ipsvd(8) instructions directory

DESCRIPTION

       The  internet  protocol	service daemons, ipsvd(7), can be told to read and follow instructions from a directory on incoming connections to
       the socket they listen on.

       For mostly static instructions or for performance reasons, it is possible to compile the instructions from  a  directory  into  a  constant
       database (cdb) with ipsvd-cdb(8) for faster lookup, and to tell ipsvd(7) to read the instructions from there.

MATCHING

       On each incoming connection, the ipsvd(7) matches the client's IP address against files in the instructions directory.  For example, the IP
       address a.b.c.d which reverse resolves to moa.bit.smarden.org is matched against the following files in the instructions directory, in this
       order, first match wins:

       1.     a.b.c.d

       2.     a.b.c

       3.     a.b

       4.     a

       If the client's hostname has been successfully looked up in DNS:

       5.     moa.bit.smarden.org

       6.     bit.smarden.org

       7.     smarden.org

       8.     org

       And finally the catchall file ``0'' (zero):

       9.     0

       After  successfully  matching a client's IP address or hostname against the instructions directory, ipsvd(7) examines the file that matched
       the IP address or hostname, and acts accordingly:

       1.     If neither the user's read permission, nor the user's execute permission is set for the file, the connection is closed immediately.

       2.     If the file has the user's execute permission set, ipsvd(7) reads the contents of the file and runs /bin/sh -c '<contents>'  instead
	      of the default program prog given at the command line for this connection.

       3.     If  the  file has the user's read permission set, ipsvd(7) reads the contents of the file and interprets each line as an instruction
	      for this connection (see below).

       If the client's IP address or hostname doesn't match any file in the instructions directory, the default action is taken (the program  prog
       is run to handle the connection).

INSTRUCTIONS

       If  ipsvd(7)  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.

       Empty lines and lines starting with ``#'' are ignored.

       +VAR=VALUE
	      environment.  If the line starts with a plus (``+''), and the string following the plus contains a ``='', ipsvd(7) puts  the  string
	      following  the  plus  into  the environment before starting prog to handle the connection.  If the string following the plus doesn't
	      contain a ``='', ipsvd(7) makes sure that the environment variable with the name string is not set.

       Cnum[:msg]
	      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 num is zero, per host concurrency limit is disabled.  If num is followed by
	      ``:msg'', the message msg is written to this client if possible, if the per host concurrency limit is reached.

	      msg may contain backslash-escaped characters as follows: ``\'' is converted to a single backslash, ``
'' is  converted	to  a  new
	      line character, and ``
'' is converted to a carriage return.

	      On  multiple concurrency instructions the last processed concurrency instruction is considered.  Not all ipsvd(7)'s support per host
	      concurrency.

       =hostname[:forward]
	      check hostname.  If the line starts with a ``='', and is followed by a hostname, ipsvd(7) looks up the IP addresses for hostname	in
	      DNS and checks if the client's IP address matches one of these IP addresses.  If so, ipsvd(7) stops processing the instructions here
	      and runs prog.  If hostname is followed a colon and forward, ipsvd(7) now examines the file forward and acts accordingly, instead of
	      running prog.  All check hostname instructions in forward are ignored.  If forward does not exist, the connection is closed.

	      hostname may be ``0'' (zero), matching any IP address.

	      Note: Using check hostname instructions can cause significant delay while responding to connection attempts, caused by DNS lookups.

       If ipsvd(7) cannot interpret a line, it prints a warning, discards the line, and continues with the next instruction if any.

       After processing all instructions, ipsvd(7) runs prog.  If the file contains at least one check hostname instruction, and none was success-
       ful, it closes the connection instead of running prog.

EXAMPLE INSTRUCTIONS

       +MEMORY=20000
	      This instruction causes the environment variable ``MEMORY'' with the value ``20000'' to be available to the program prog	that  han-
	      dles the connection.

       +DEBUG=
	      This instruction adds the variable ``DEBUG'' with an empty value to the environment.

       +LOGNAME
	      This instructions makes sure that the environment variable ``LOGNAME'' is unset when running prog.

       C16    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.

       =floyd.dyn.smarden.org:127.0.0.1
	      Check IP address of the dynamic hostname floyd.dyn.smarden.org.  If one of the IP addresses floyd.dyn.smarden.org currently resolves
	      to matches the client's IP address, handle the connection through the file 127.0.0.1 in the instructions directory.

SEE ALSO

       ipsvd(7), ipsvd-cdb(8), tcpsvd(8), sslsvd(8), udpsvd(8), sslio(8)

       http://smarden.org/ipsvd/

AUTHOR

       Gerrit Pape <pape@smarden.org>

																 ipsvd-instruct(5)