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/* vi: set sw=4 ts=4: */
/*
* Mini nslookup implementation for busybox
*
* Copyright (C) 1999,2000 by Lineo, inc. and John Beppu
* Copyright (C) 1999,2000,2001 by John Beppu <beppu@codepoet.org>
*
* Correct default name server display and explicit name server option
* added by Ben Zeckel <bzeckel@hmc.edu> June 2001
*
* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
*/
#include <ctype.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <resolv.h>
#include <arpa/inet.h>
#include "busybox.h"
/*
| I'm only implementing non-interactive mode;
| I totally forgot nslookup even had an interactive mode.
*/
/* only works for IPv4 */
static int addr_fprint(char *addr)
{
uint8_t split[4];
uint32_t ip;
uint32_t *x = (uint32_t *) addr;
ip = ntohl(*x);
split[0] = (ip & 0xff000000) >> 24;
split[1] = (ip & 0x00ff0000) >> 16;
split[2] = (ip & 0x0000ff00) >> 8;
split[3] = (ip & 0x000000ff);
printf("%d.%d.%d.%d", split[0], split[1], split[2], split[3]);
return 0;
}
/* takes the NULL-terminated array h_addr_list, and
* prints its contents appropriately
*/
static int addr_list_fprint(char **h_addr_list)
{
int i, j;
char *addr_string = (h_addr_list[1])
? "Addresses: " : "Address: ";
printf("%s ", addr_string);
for (i = 0, j = 0; h_addr_list[i]; i++, j++) {
addr_fprint(h_addr_list[i]);
/* real nslookup does this */
if (j == 4) {
if (h_addr_list[i + 1]) {
printf("\n ");
}
j = 0;
} else {
if (h_addr_list[i + 1]) {
printf(", ");
}
}
}
puts("");
return 0;
}
/* print the results as nslookup would */
static struct hostent *hostent_fprint(struct hostent *host, const char *server_host)
{
if (host) {
printf("%s %s\n", server_host, host->h_name);
addr_list_fprint(host->h_addr_list);
} else {
printf("*** Unknown host\n");
}
return host;
}
/* changes a c-string matching the perl regex \d+\.\d+\.\d+\.\d+
* into a uint32_t
*/
static uint32_t str_to_addr(const char *addr)
{
uint32_t split[4];
uint32_t ip;
sscanf(addr, "%d.%d.%d.%d",
&split[0], &split[1], &split[2], &split[3]);
/* assuming sscanf worked */
ip = (split[0] << 24) |
(split[1] << 16) | (split[2] << 8) | (split[3]);
return htonl(ip);
}
/* gethostbyaddr wrapper */
static struct hostent *gethostbyaddr_wrapper(const char *address)
{
struct in_addr addr;
addr.s_addr = str_to_addr(address);
return gethostbyaddr((char *) &addr, 4, AF_INET); /* IPv4 only for now */
}
/* lookup the default nameserver and display it */
static inline void server_print(void)
{
struct sockaddr_in def = _res.nsaddr_list[0];
char *ip = inet_ntoa(def.sin_addr);
hostent_fprint(gethostbyaddr_wrapper(ip), "Server:");
puts("");
}
/* alter the global _res nameserver structure to use
an explicit dns server instead of what is in /etc/resolv.h */
static inline void set_default_dns(char *server)
{
struct in_addr server_in_addr;
if(inet_aton(server,&server_in_addr))
{
_res.nscount = 1;
_res.nsaddr_list[0].sin_addr = server_in_addr;
}
}
/* naive function to check whether char *s is an ip address */
static int is_ip_address(const char *s)
{
while (*s) {
if ((isdigit(*s)) || (*s == '.')) {
s++;
continue;
}
return 0;
}
return 1;
}
/* ________________________________________________________________________ */
int nslookup_main(int argc, char **argv)
{
struct hostent *host;
/*
* initialize DNS structure _res used in printing the default
* name server and in the explicit name server option feature.
*/
res_init();
/*
* We allow 1 or 2 arguments.
* The first is the name to be looked up and the second is an
* optional DNS server with which to do the lookup.
* More than 3 arguments is an error to follow the pattern of the
* standard nslookup
*/
if (argc < 2 || *argv[1]=='-' || argc > 3)
bb_show_usage();
else if(argc == 3)
set_default_dns(argv[2]);
server_print();
if (is_ip_address(argv[1])) {
host = gethostbyaddr_wrapper(argv[1]);
} else {
host = xgethostbyname(argv[1]);
}
hostent_fprint(host, "Name: ");
if (host) {
return EXIT_SUCCESS;
}
return EXIT_FAILURE;
}
/* $Id: nslookup.c,v 1.33 2004/10/13 07:25:01 andersen Exp $ */
|
