/* 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 * * 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. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * */ #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(", "); } } } printf("\n"); 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:"); printf("\n"); } /* 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 $ */