# 2.11BSD#431 - /usr/man/cat3/hosts_access.0

    HOSTS_ACCESS(3)     UNIX Programmer's Manual	  HOSTS_ACCESS(3)

    NAME
         hosts_access, hosts_ctl, request_init, request_set - access
         control library

    SYNOPSIS
         #include "tcpd.h"

         extern int allow_severity;
         extern int deny_severity;

         struct request_info *request_init(request, key, value, ..., 0)
         struct request_info *request;

         struct request_info *request_set(request, key, value, ..., 0)
         struct request_info *request;

         int hosts_access(request)
         struct request_info *request;

         int hosts_ctl(daemon, client_name, client_addr, client_user)
         char *daemon;
         char *client_name;
         char *client_addr;
         char *client_user;

    DESCRIPTION
         The routines described in this document are part of the
         libwrap.a library. They implement a rule-based access con-
         trol language with optional shell commands that are executed
         when a rule fires.

         request_init() initializes a structure with information
         about a client request. request_set() updates an already
         initialized request structure. Both functions take a
         variable-length list of key-value pairs and return their
         first argument.  The argument lists are terminated with a
         zero key value. All string-valued arguments are copied. The
         expected keys (and corresponding value types) are:

         RQ_FILEDES (int)
    	  The file descriptor associated with the request.

         RQ_CLIENT_NAME (char *)
    	  The client host name.

         RQ_CLIENT_ADDRESS (char *)
    	  A printable representation of the client network
    	  address.

         RQ_CLIENT_SOCKADDR (struct sockaddr_in *)
    	  An internal representation of the client network
    	  address and port.  The contents of the structure are

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    HOSTS_ACCESS(3)     UNIX Programmer's Manual	  HOSTS_ACCESS(3)

    	  not copied.

         RQ_SERVER_NAME (char *)
    	  The hostname associated with the server endpoint
    	  address.

         RQ_SERVER_ADDRESS (char *)
    	  A printable representation of the server endpoint
    	  address.

         RQ_SERVER_SOCKADDR (struct sockaddr_in *)
    	  An internal representation of the server endpoint
    	  address and port.  The contents of the structure are
    	  not copied.

         RQ_USER_NAME (char *)
    	  The name of the user on whose behalf the client host
    	  makes the request.

         hosts_access() consults the access control tables described
         in the hosts_access(5) manual page.  When internal endpoint
         information is available, host names and client user names
         are looked up on demand, using the request structure as a
         cache.  hosts_access() returns zero if access should be
         denied.

         hosts_ctl() is a wrapper around the request_init() and
         hosts_access() routines with a perhaps more convenient
         interface (though it does not pass on enough information to
         support automated client username lookups).  The client host
         address, client host name and username arguments should con-
         tain valid data or STRING_UNKNOWN.  hosts_ctl() returns zero
         if access should be denied.

         The allow_severity and deny_severity variables determine how
         accepted and rejected requests may be logged. They must be
         provided by the caller and may be modified by rules in the
         access control tables.

    DIAGNOSTICS
         Problems are reported via the syslog daemon.

    SEE ALSO
         hosts_access(5), format of the access control tables.
         hosts_options(5), optional extensions to the base language.

    FILES
         /etc/hosts.access, /etc/hosts.deny, access control tables.

    BUGS
         hosts_access() uses the strtok() library function. This may
         interfere with other code that relies on strtok().

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    HOSTS_ACCESS(3)     UNIX Programmer's Manual	  HOSTS_ACCESS(3)

    AUTHOR
         Wietse Venema (wietse@wzv.win.tue.nl)
         Department of Mathematics and Computing Science
         Eindhoven University of Technology
         Den Dolech 2, P.O. Box 513,
         5600 MB Eindhoven, The Netherlands

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