path: root/libc/inet/resolv.c

/* resolv.c: DNS Resolver
 *
 * Copyright (C) 1998  Kenneth Albanowski <kjahds@kjahds.com>,
 *                     The Silver Hammer Group, Ltd.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 *  5-Oct-2000 W. Greathouse  wgreathouse@smva.com
 *                              Fix memory leak and memory corruption.
 *                              -- Every name resolution resulted in
 *                                 a new parse of resolv.conf and new
 *                                 copy of nameservers allocated by
 *                                 strdup.
 *                              -- Every name resolution resulted in
 *                                 a new read of resolv.conf without
 *                                 resetting index from prior read...
 *                                 resulting in exceeding array bounds.
 *
 *                              Limit nameservers read from resolv.conf
 *
 *                              Add "search" domains from resolv.conf
 *
 *                              Some systems will return a security
 *                              signature along with query answer for
 *                              dynamic DNS entries.
 *                              -- skip/ignore this answer
 *
 *                              Include arpa/nameser.h for defines.
 *
 *                              General cleanup
 *
 * 20-Jun-2001 Michal Moskal <malekith@pld.org.pl>
 *   partial IPv6 support (i.e. gethostbyname2() and resolve_address2()
 *   functions added), IPv6 nameservers are also supported.
 *
 * 6-Oct-2001 Jari Korva <jari.korva@iki.fi>
 *   more IPv6 support (IPv6 support for gethostbyaddr();
 *   address family parameter and improved IPv6 support for get_hosts_byname
 *   and read_etc_hosts; getnameinfo() port from glibc; defined
 *   defined ip6addr_any and in6addr_loopback)
 */

#define __FORCE_GLIBC
#include <features.h>
#include <string.h>
#include <stdio.h>
#include <signal.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <resolv.h>
#include <netdb.h>
#include <ctype.h>
#include <arpa/nameser.h>
#include <sys/utsname.h>
#include <sys/un.h>

#define MAX_RECURSE 5
#define REPLY_TIMEOUT 10
#define MAX_RETRIES 15
#define MAX_SERVERS 3
#define MAX_SEARCH 4

#undef DEBUG
/*#define DEBUG*/

#ifdef DEBUG
#define DPRINTF(X,args...) fprintf(stderr, X, ##args)
#else
#define DPRINTF(X,args...)
#endif /* DEBUG */


struct resolv_header {
	int id;
	int qr,opcode,aa,tc,rd,ra,rcode;
	int qdcount;
	int ancount;
	int nscount;
	int arcount;
};

struct resolv_question {
	char * dotted;
	int qtype;
	int qclass;
};

struct resolv_answer {
	char * dotted;
	int atype;
	int aclass;
	int ttl;
	int rdlength;
	unsigned char * rdata;
	int rdoffset;
};

extern int nameservers;
extern char * nameserver[MAX_SERVERS];
extern int searchdomains;
extern char * searchdomain[MAX_SEARCH];
extern struct hostent * get_hosts_byname(const char * name, int type);
extern struct hostent * get_hosts_byaddr(const char * addr, int len, int type);
extern struct hostent * read_etc_hosts(const char * name, int type, int ip);
extern int resolve_address(const char * address, int nscount, 
	char ** nsip, struct in_addr * in);
extern int resolve_mailbox(const char * address, int nscount, 
	char ** nsip, struct in_addr * in);
extern int dns_lookup(const char * name, int type, int nscount, 
	char ** nsip, unsigned char ** outpacket, struct resolv_answer * a);

int encode_dotted(const char * dotted, unsigned char * dest, int maxlen);
int decode_dotted(const unsigned char * message, int offset, 
	char * dest, int maxlen);
int length_dotted(const unsigned char * message, int offset);
int encode_header(struct resolv_header * h, unsigned char * dest, int maxlen);
int decode_header(unsigned char * data, struct resolv_header * h);
int encode_question(struct resolv_question * q,
	unsigned char * dest, int maxlen);
int decode_question(unsigned char * message, int offset,
	struct resolv_question * q);
int encode_answer(struct resolv_answer * a,
	unsigned char * dest, int maxlen);
int decode_answer(unsigned char * message, int offset,
	struct resolv_answer * a);
int length_question(unsigned char * message, int offset);
extern int open_nameservers(void);


#ifdef L_encodeh
int encode_header(struct resolv_header *h, unsigned char *dest, int maxlen)
{
	if (maxlen < HFIXEDSZ)
		return -1;

	dest[0] = (h->id & 0xff00) >> 8;
	dest[1] = (h->id & 0x00ff) >> 0;
	dest[2] = (h->qr ? 0x80 : 0) |
		((h->opcode & 0x0f) << 3) |
		(h->aa ? 0x04 : 0) | 
		(h->tc ? 0x02 : 0) | 
		(h->rd ? 0x01 : 0);
	dest[3] = (h->ra ? 0x80 : 0) | (h->rcode & 0x0f);
	dest[4] =