c linux tcpd api example

c_linux_tcpd_api_example.c

/*
simple usage of the tcpd/tcp wrapper API

a full-fledged program would probalby call hosts_access() upon accepting a new 
connection and if denied it would close() 
the established connection with FIN,ACK or most preferably RST

build with :

gcc -c tcpd_test.c

static libs
gcc -o tcpd_test tcpd_test.o /usr/lib/libwrap.a /usr/lib/libnsl.a

dynamic libs
gcc -o tcpd_test tcpd_test.o /usr/lib/libwrap.so /usr/lib/libnsl.so


for denying access add this line to /etc/hosts.deny

8888: *

*/

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <tcpd.h>


int main( int argc, char *argv[] ) {
        struct request_info rq;
        struct sockaddr_in myserver_address;
        int rc = 0;

        /* setup the criteria */
        myserver_address.sin_family = AF_INET;
        myserver_address.sin_port = htons( 8888 );
        myserver_address.sin_addr.s_addr = INADDR_ANY;

        /* initialize the request structure with our criteria */
        request_init( &rq, RQ_SERVER_SIN, &myserver_address, 0 );

        /* call fromhosts() before calling hosts_access() as mentioned in the manual */
        fromhost( &rq );

        rc = hosts_access( &rq );

        fprintf( stderr, "access %s (%d)\n", (rc) ? "granted" : "denied", rc );

        return rc;
}