TCP Wrappers Release Notes

What’s in This Version
TCP Wrapper Features
Chapter 1 11
This API initializes the request_info structure with information
about the client request.
— request_set()
This API updates an initialized request_info structure.
Both request_init() and request_set() APIs take the
request_info structure and a variable-length list of key-value
pairs as input parameters and return the first argument which is
the request_info structure defined in the tcpd.h header file. The
argument lists are terminated with a zero key value.
— hosts_access()
This API reads the ACLs and returns either ‘1’ or ‘0’ indicating
the access granted or denied respectively.
— hosts_ctl()
This API is a wrapper around request_init() and hosts_access()
routines. It takes the daemon name, client’s hostname, client’s
address and username as input parameters. The client
hostname, address and username arguments should contain
valid data or STRING_UNKNOWN defined in the tcpd.h file.
The hosts_ctl() API returns zero if access should be denied.
The following are the methods to implement access control checks in
a daemon program:
1. Fill the request_info structure’s variable elements using
request_init ( ) and request_set ( ) routines and call the
hosts_access( ) routine to verify these elements with ACLs.
2. Call hosts_ctl ( ) function with appropriate input parameters
to check with ACLs.
NOTE Refer to hosts_access(3) man page for more information on these
APIs.
• tcpdchk
tcpdchk is a tool that can be used to examine the validity of entries in
the /etc/inetd.conf file and ACLs.