static int vipalias_lock()
{
	int ret = -1;
	/*
		we create a symlink with our PID (a dummy symlink).
		If this fails, we do a readlink and check if the process is
		alive. If not, we erase the symlink and try again.

		If the process is alive, we sleep 2 seconds.
	*/
	char pidstr[10];
	snprintf (pidstr,sizeof(pidstr)-1,"%u",getpid());
	while (1){
		if (symlink(pidstr,lockfile)!=-1){
			ret = 0;
			break;
		}else if (errno != EEXIST){
			fprintf (stderr,"Can't create lockfile %s (%s)\n"
				,lockfile,strerror(errno));
			break;
		}else{
			char buf[100];
			int len = readlink(lockfile,buf,sizeof(buf));
			if (len > 0){
				buf[len] = '\0';
				pid_t pid = atoi(buf);
				if (kill(pid,0)==-1){
					unlink (lockfile);
				}else{
					// Process exist
					fprintf (stderr,"vipalias can't lock %s, waiting for process %u\n"
						,lockfile,pid);
					sleep(2);
				}
			}
		}
	}
	
	return ret;
}

static void vipalias_unlock()
{
	unlink (lockfile);
}