/*
* 
* dumpcache-expire v0.2
*
* quick and dirty hacked tool to expire an entry in djbdns dnscache's cache 
* by setting expiration time to 0.
* needs the dumpcache-patch from http://www.efge.org/djbdns/
*
* http://plonk.de/sw/djb/dumpcache-expire.c
* (C) 2003 Jakob Hirsch (dumpcache@plonk.de)
*
* 
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* 
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
* 
* [http://www.fsf.org/licenses/gpl.txt]
* 
*/

#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>

void name(char * p, char * hostname);

int main(int argc, char *argv[])
{
	/* the path to your dnscache dumpfile */
	const char dumpcache[] = "/service/dnscache/root/dump/dumpcache";
	/* expiration time (seconds since 1970-1-1) */
	const char expiration[8] = "\000\000\000\000\000\000\000\000";
	
	int fd;
	char *start, *end, *p;
	int *key_len, *data_len;
	char hostname[255]; /* hostnames should not be longer than that... */
	struct stat st;
	time_t mtime;
	int i, count;

	if (argc<2) {
		printf("Usage: dumpcache-expire <record> [records...]\n");
		exit(-1);
	}
	
	/* wait for dnscache to dump */
	stat(dumpcache, &st);
	mtime = st.st_mtime;
 	system("svc -a /service/dnscache");
	count = 0;
	while (mtime == st.st_mtime) {
		if (count++ > 10) {
			printf("timeout waiting for dnscache dump\n");
			exit(-1);
		}
		usleep(100000);
		stat(dumpcache, &st);
	}
	
	fd = open(dumpcache, O_RDWR);
	if (fd == -1)
	{
		printf("open %s: %s\n", dumpcache, strerror(errno));
		exit(-1);
	}
	fstat(fd, &st);
	start = p = mmap(0, st.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
	if (p == MAP_FAILED) {
		printf("mmap: %s\n", strerror(errno));
		exit(-1);
	} 
	end = p + st.st_size;	
	
	count = 0;
	while (p < end) {
		key_len  = (int*) p;
		data_len = (int*) p+1;

		name(p+18, hostname);

		for (i=1; i < argc; i++)
			if (strcasecmp(hostname, argv[i]) == 0) {
			       memcpy(p+8, expiration, 8);
			       count++;
			}
					       
		p += *data_len + *key_len + 16;
	}
	
	munmap(start, st.st_size);
	close(fd);
	
	if (count)
		system("svc -h /service/dnscache");
	printf("%i records expired\n", count);
	exit(count);
}

/* build the hostname (no bounds checking) */
void name(char *p, char *hostname) {
	while (*p != 0) {
		memcpy(hostname, p+1, *p);
		hostname[*p] = '.';
		hostname += (*p) + 1;
		p += (*p) + 1;
	}
	*(hostname-1) = 0;
}