/*
*****************************************************************

* Copyright (c) 2005 Sun Microsystems, Inc. All Rights Reserved.
*

* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY
* OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT
* LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE
* LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING,
* MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
*
*****************************************************************
*/

/*================================================================*/
/* Name: pb_623.c (Port blocker for port 623)                     */
/* Description: Simple UDP server code that listens on port 623   */
/*----------------------------------------------------------------*/
/* Changes:                                                       */
/*================================================================*/
/* INCLUDES-------------------------------------------------------*/
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <unistd.h> /* close() */
#include <string.h> /* memset() */
#include <fcntl.h>
#include <syslog.h>
/* Global Definitions --------------------------------------------*/
#define LOCAL_SERVER_PORT 623
#define MAX_MSG 100
/*----------------------------------------------------------------*/
/* Function writelog: Writes errors and messages to logs.         */
/*----------------------------------------------------------------*/
void writelog(char errmsg[])
{
syslog(LOG_INFO, errmsg);
}
/*----------------------------------------------------------------*/
/* Function daemonize: Forks the process and turns it into a      */
/* daemon.                                                        */ 
/*----------------------------------------------------------------*/
int daemonize(void)
{
pid_t pid;
int fd;
/* if we are started from init no need to become daemon */
if (getppid() == 1)
{
writelog("Portblocker: Instance already running");
return;
}
pid = (pid_t) fork();
if (pid < 0 || pid > 0)
{
writelog("Portblocker: Unable to fork");
exit(0);
}
if (setpgrp() == -1)
{
writelog("Portblocker: Unable to set process group");
exit(1);
}
pid = (pid_t) fork();
if (pid < 0 || pid > 0)
{
writelog("Portblocker: Unable to fork");
exit(0);
}
chdir("/");
umask(0);
for (fd=0; fd<64; fd++)
close(fd);
open("/dev/null", O_RDWR);
dup(0);
dup(0);
return(pid);
}
/*----------------------------------------------------------------*/
/* Main: Opens UDP listener on port 623 and then loops. Uses      */
/* daemonize to fork as a daemon if not started at boot time.     */
/*----------------------------------------------------------------*/
int main(int argc, char *argv[])
{
int sd, rc, n, cliLen;
int pid;
struct sockaddr_in cliAddr, servAddr;
char msg[MAX_MSG];
pid = daemonize();
/* socket creation */
if ( (sd=socket(AF_INET, SOCK_DGRAM, 0)) <0 )
{
writelog("Portblocker: cannot open socket");
exit(1);
}
/* bind local server port */
servAddr.sin_family = AF_INET;
servAddr.sin_addr.s_addr = htonl(INADDR_ANY);
servAddr.sin_port = htons(LOCAL_SERVER_PORT);
if ( (rc = bind (sd, (struct sockaddr *)
&servAddr,sizeof(servAddr))) <0 )
{
writelog("Portblocker: cannot bind to port");
exit(1);
}
writelog("Portblocker: Started successfully");
/* loop - keep the port alive */
while(1)
{
/* init buffer */
memset(msg,0x0,MAX_MSG);
/* receive message */
cliLen = sizeof(cliAddr);
if ( (n = recvfrom(sd, msg, MAX_MSG, 0, (struct sockaddr *)
&cliAddr, &cliLen)) <0 )
{
writelog("Portblocker: cannot receive data");
continue;
}
}/* end while loop */
return 0;
} /* end main */