/*
 * Copyright (c) 1995 - 2006 Kungliga Tekniska Högskolan
 * (Royal Institute of Technology, Stockholm, Sweden).
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 
 * 3. Neither the name of the Institute nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <roken.h>
#ifdef HAVE_ARPA_NAMESER_H
#include <arpa/nameser.h>
#endif
#ifdef HAVE_RESOLV_H
#include <resolv.h>
#endif
#include "resolve.h"

#include <assert.h>

RCSID("$Id: resolve.c 19869 2007-01-12 16:03:14Z lha $");

#ifdef _AIX /* AIX have broken res_nsearch() in 5.1 (5.0 also ?) */
#undef HAVE_RES_NSEARCH
#endif

#define DECL(X) {#X, rk_ns_t_##X}

static struct stot{
    const char *name;
    int type;
}stot[] = {
    DECL(a),
    DECL(aaaa),
    DECL(ns),
    DECL(cname),
    DECL(soa),
    DECL(ptr),
    DECL(mx),
    DECL(txt),
    DECL(afsdb),
    DECL(sig),
    DECL(key),
    DECL(srv),
    DECL(naptr),
    DECL(sshfp),
    DECL(ds),
    {NULL, 	0}
};

int _resolve_debug = 0;

int ROKEN_LIB_FUNCTION
dns_string_to_type(const char *name)
{
    struct stot *p = stot;
    for(p = stot; p->name; p++)
	if(strcasecmp(name, p->name) == 0)
	    return p->type;
    return -1;
}

const char * ROKEN_LIB_FUNCTION
dns_type_to_string(int type)
{
    struct stot *p = stot;
    for(p = stot; p->name; p++)
	if(type == p->type)
	    return p->name;
    return NULL;
}

#if (defined(HAVE_RES_SEARCH) || defined(HAVE_RES_NSEARCH)) && defined(HAVE_DN_EXPAND)

static void
dns_free_rr(struct resource_record *rr)
{
    if(rr->domain)
	free(rr->domain);
    if(rr->u.data)
	free(rr->u.data);
    free(rr);
}

void ROKEN_LIB_FUNCTION
dns_free_data(struct dns_reply *r)
{
    struct resource_record *rr;
    if(r->q.domain)
	free(r->q.domain);
    for(rr = r->head; rr;){
	struct resource_record *tmp = rr;
	rr = rr->next;
	dns_free_rr(tmp);
    }
    free (r);
}

static int
parse_record(const unsigned char *data, const unsigned char *end_data, 
	     const unsigned char **pp, struct resource_record **ret_rr)
{
    struct resource_record *rr;
    int type, class, ttl, size;
    int status;
    char host[MAXDNAME];
    const unsigned char *p = *pp;

    *ret_rr = NULL;

    status = dn_expand(data, end_data, p, host, sizeof(host));
    if(status < 0) 
	return -1;
    if (p + status + 10 > end_data)
	return -1;

    p += status;
    type = (p[0] << 8) | p[1];
    p += 2;
    class = (p[0] << 8) | p[1];
    p += 2;
    ttl = (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];
    p += 4;
    size = (p[0] << 8) | p[1];
    p += 2;

    if (p + size > end_data)
	return -1;

    rr = calloc(1, sizeof(*rr));
    if(rr == NULL) 
	return -1;
    rr->domain = strdup(host);
    if(rr->domain == NULL) {
	dns_free_rr(rr);
	return -1;
    }
    rr->type = type;
    rr->class = class;
    rr->ttl = ttl;
    rr->size = size;
    switch(type){
    case rk_ns_t_ns:
    case rk_ns_t_cname:
    case rk_ns_t_ptr:
	status = dn_expand(data, end_data, p, host, sizeof(host));
	if(status < 0) {
	    dns_free_rr(rr);
	    return -1;
	}
	rr->u.txt = strdup(host);
	if(rr->u.txt == NULL) {
	    dns_free_rr(rr);
	    return -1;
	}
	break;
    case rk_ns_t_mx:
    case rk_ns_t_afsdb:{
	size_t hostlen;

	status = dn_expand(data, end_data, p + 2, host, sizeof(host));
	if(status < 0){
	    dns_free_rr(rr);
	    return -1;
	}
	if (status + 2 > size) {
	    dns_free_rr(rr);
	    return -1;
	}

	hostlen = strlen(host);
	rr->u.mx = (struct mx_record*)malloc(sizeof(struct mx_record) + 
						hostlen);
	if(rr->u.mx == NULL) {
	    dns_free_rr(rr);
	    return -1;
	}
	rr->u.mx->preference = (p[0] << 8) | p[1];
	strlcpy(rr->u.mx->domain, host, hostlen + 1);
	break;
    }
    case rk_ns_t_srv:{
	size_t hostlen;
	status = dn_expand(data, end_data, p + 6, host, sizeof(host));
	if(status < 0){
	    dns_free_rr(rr);
	    return -1;
	}
	if (status + 6 > size) {
	    dns_free_rr(rr);
	    return -1;
	}

	hostlen = strlen(host);
	rr->u.srv = 
	    (struct srv_record*)malloc(sizeof(struct srv_record) + 
				       hostlen);
	if(rr->u.srv == NULL) {
	    dns_free_rr(rr);
	    return -1;
	}
	rr->u.srv->priority = (p[0] << 8) | p[1];
	rr->u.srv->weight = (p[2] << 8) | p[3];
	rr->u.srv->port = (p[4] << 8) | p[5];
	strlcpy(rr->u.srv->target, host, hostlen + 1);
	break;
    }
    case rk_ns_t_txt:{
	if(size == 0 || size < *p + 1) {
	    dns_free_rr(rr);
	    return -1;
	}
	rr->u.txt = (char*)malloc(*p + 1);
	if(rr->u.txt == NULL) {
	    dns_free_rr(rr);
	    return -1;
	}
	strncpy(rr->u.txt, (const char*)(p + 1), *p);
	rr->u.txt[*p] = '\0';
	break;
    }
    case rk_ns_t_key : {
	size_t key_len;

	if (size < 4) {
	    dns_free_rr(rr);
	    return -1;
	}

	key_len = size - 4;
	rr->u.key = malloc (sizeof(*rr->u.key) + key_len - 1);
	if (rr->u.key == NULL) {
	    dns_free_rr(rr);
	    return -1;
	}

	rr->u.key->flags     = (p[0] << 8) | p[1];
	rr->u.key->protocol  = p[2];
	rr->u.key->algorithm = p[3];
	rr->u.key->key_len   = key_len;
	memcpy (rr->u.key->key_data, p + 4, key_len);
	break;
    }
    case rk_ns_t_sig : {
	size_t sig_len, hostlen;

	if(size <= 18) {
	    dns_free_rr(rr);
	    return -1;
	}
	status = dn_expand (data, end_data, p + 18, host, sizeof(host));
	if (status < 0) {
	    dns_free_rr(rr);
	    return -1;
	}
	if (status + 18 > size) {
	    dns_free_rr(rr);
	    return -1;
	}

	/* the signer name is placed after the sig_data, to make it
           easy to free this structure; the size calculation below
           includes the zero-termination if the structure itself.
	   don't you just love C?
	*/
	sig_len = size - 18 - status;
	hostlen = strlen(host);
	rr->u.sig = malloc(sizeof(*rr->u.sig)
			      + hostlen + sig_len);
	if (rr->u.sig == NULL) {
	    dns_free_rr(rr);
	    return -1;
	}
	rr->u.sig->type           = (p[0] << 8) | p[1];
	rr->u.sig->algorithm      = p[2];
	rr->u.sig->labels         = p[3];
	rr->u.sig->orig_ttl       = (p[4] << 24) | (p[5] << 16)
	    | (p[6] << 8) | p[7];
	rr->u.sig->sig_expiration = (p[8] << 24) | (p[9] << 16)
	    | (p[10] << 8) | p[11];
	rr->u.sig->sig_inception  = (p[12] << 24) | (p[13] << 16)
	    | (p[14] << 8) | p[15];
	rr->u.sig->key_tag        = (p[16] << 8) | p[17];
	rr->u.sig->sig_len        = sig_len;
	memcpy (rr->u.sig->sig_data, p + 18 + status, sig_len);
	rr->u.sig->signer         = &rr->u.sig->sig_data[sig_len];
	strlcpy(rr->u.sig->signer, host, hostlen + 1);
	break;
    }

    case rk_ns_t_cert : {
	size_t cert_len;

	if (size < 5) {
	    dns_free_rr(rr);
	    return -1;
	}

	cert_len = size - 5;
	rr->u.cert = malloc (sizeof(*rr->u.cert) + cert_len - 1);
	if (rr->u.cert == NULL) {
	    dns_free_rr(rr);
	    return -1;
	}

	rr->u.cert->type      = (p[0] << 8) | p[1];
	rr->u.cert->tag       = (p[2] << 8) | p[3];
	rr->u.cert->algorithm = p[4];
	rr->u.cert->cert_len  = cert_len;
	memcpy (rr->u.cert->cert_data, p + 5, cert_len);
	break;
    }
    case rk_ns_t_sshfp : {
	size_t sshfp_len;

	if (size < 2) {
	    dns_free_rr(rr);
	    return -1;
	}

	sshfp_len = size - 2;

	rr->u.sshfp = malloc (sizeof(*rr->u.sshfp) + sshfp_len - 1);
	if (rr->u.sshfp == NULL) {
	    dns_free_rr(rr);
	    return -1;
	}

	rr->u.sshfp->algorithm = p[0];
	rr->u.sshfp->type      = p[1];
	rr->u.sshfp->sshfp_len  = sshfp_len;
	memcpy (rr->u.sshfp->sshfp_data, p + 2, sshfp_len);
	break;
    }
    case rk_ns_t_ds: {
	size_t digest_len;

	if (size < 4) {
	    dns_free_rr(rr);
	    return -1;
	}

	digest_len = size - 4;

	rr->u.ds = malloc (sizeof(*rr->u.ds) + digest_len - 1);
	if (rr->u.ds == NULL) {
	    dns_free_rr(rr);
	    return -1;
	}

	rr->u.ds->key_tag     = (p[0] << 8) | p[1];
	rr->u.ds->algorithm   = p[2];
	rr->u.ds->digest_type = p[3];
	rr->u.ds->digest_len  = digest_len;
	memcpy (rr->u.ds->digest_data, p + 4, digest_len);
	break;
    }
    default:
	rr->u.data = (unsigned char*)malloc(size);
	if(size != 0 && rr->u.data == NULL) {
	    dns_free_rr(rr);
	    return -1;
	}
	if (size)
	    memcpy(rr->u.data, p, size);
    }
    *pp = p + size;
    *ret_rr = rr;

    return 0;
}

#ifndef TEST_RESOLVE
static
#endif
struct dns_reply*
parse_reply(const unsigned char *data, size_t len)
{
    const unsigned char *p;
    int status;
    int i;
    char host[MAXDNAME];
    const unsigned char *end_data = data + len;
    struct dns_reply *r;
    struct resource_record **rr;
    
    r = calloc(1, sizeof(*r));
    if (r == NULL)
	return NULL;

    p = data;

    r->h.id = (p[0] << 8) | p[1];
    r->h.flags = 0;
    if (p[2] & 0x01)
	r->h.flags |= rk_DNS_HEADER_RESPONSE_FLAG;
    r->h.opcode = (p[2] >> 1) & 0xf;
    if (p[2] & 0x20)
	r->h.flags |= rk_DNS_HEADER_AUTHORITIVE_ANSWER;
    if (p[2] & 0x40)
	r->h.flags |= rk_DNS_HEADER_TRUNCATED_MESSAGE;
    if (p[2] & 0x80)
	r->h.flags |= rk_DNS_HEADER_RECURSION_DESIRED;
    if (p[3] & 0x01)
	r->h.flags |= rk_DNS_HEADER_RECURSION_AVAILABLE;
    if (p[3] & 0x04)
	r->h.flags |= rk_DNS_HEADER_AUTHORITIVE_ANSWER;
    if (p[3] & 0x08)
	r->h.flags |= rk_DNS_HEADER_CHECKING_DISABLED;
    r->h.response_code = (p[3] >> 4) & 0xf;
    r->h.qdcount = (p[4] << 8) | p[5];
    r->h.ancount = (p[6] << 8) | p[7];
    r->h.nscount = (p[8] << 8) | p[9];
    r->h.arcount = (p[10] << 8) | p[11];

    p += 12;

    if(r->h.qdcount != 1) {
	free(r);
	return NULL;
    }
    status = dn_expand(data, end_data, p, host, sizeof(host));
    if(status < 0){
	dns_free_data(r);
	return NULL;
    }
    r->q.domain = strdup(host);
    if(r->q.domain == NULL) {
	dns_free_data(r);
	return NULL;
    }
    if (p + status + 4 > end_data) {
	dns_free_data(r);
	return NULL;
    }
    p += status;
    r->q.type = (p[0] << 8 | p[1]);
    p += 2;
    r->q.class = (p[0] << 8 | p[1]);
    p += 2;
    
    rr = &r->head;
    for(i = 0; i < r->h.ancount; i++) {
	if(parse_record(data, end_data, &p, rr) != 0) {
	    dns_free_data(r);
	    return NULL;
	}
	rr = &(*rr)->next;
    }
    for(i = 0; i < r->h.nscount; i++) {
	if(parse_record(data, end_data, &p, rr) != 0) {
	    dns_free_data(r);
	    return NULL;
	}
	rr = &(*rr)->next;
    }
    for(i = 0; i < r->h.arcount; i++) {
	if(parse_record(data, end_data, &p, rr) != 0) {
	    dns_free_data(r);
	    return NULL;
	}
	rr = &(*rr)->next;
    }
    *rr = NULL;
    return r;
}

#ifdef HAVE_RES_NSEARCH
#ifdef HAVE_RES_NDESTROY
#define rk_res_free(x) res_ndestroy(x)
#else
#define rk_res_free(x) res_nclose(x)
#endif
#endif

static struct dns_reply *
dns_lookup_int(const char *domain, int rr_class, int rr_type)
{
    struct dns_reply *r;
    unsigned char *reply = NULL;
    int size;
    int len;
#ifdef HAVE_RES_NSEARCH
    struct __res_state state;
    memset(&state, 0, sizeof(state));
    if(res_ninit(&state))
	return NULL; /* is this the best we can do? */
#elif defined(HAVE__RES)
    u_long old_options = 0;
#endif
    
    size = 0;
    len = 1000;
    do {
	if (reply) {
	    free(reply);
	    reply = NULL;
	}
	if (size <= len)
	    size = len;
	if (_resolve_debug) {
#ifdef HAVE_RES_NSEARCH
	    state.options |= RES_DEBUG;
#elif defined(HAVE__RES)
	    old_options = _res.options;
	    _res.options |= RES_DEBUG;
#endif
	    fprintf(stderr, "dns_lookup(%s, %d, %s), buffer size %d\n", domain,
		    rr_class, dns_type_to_string(rr_type), size);
	}
	reply = malloc(size);
	if (reply == NULL) {
#ifdef HAVE_RES_NSEARCH
	    rk_res_free(&state);
#endif
	    return NULL;
	}
#ifdef HAVE_RES_NSEARCH
	len = res_nsearch(&state, domain, rr_class, rr_type, reply, size);
#else
	len = res_search(domain, rr_class, rr_type, reply, size);
#endif
	if (_resolve_debug) {
#if defined(HAVE__RES) && !defined(HAVE_RES_NSEARCH)
	    _res.options = old_options;
#endif
	    fprintf(stderr, "dns_lookup(%s, %d, %s) --> %d\n",
		    domain, rr_class, dns_type_to_string(rr_type), len);
	}
	if (len < 0) {
#ifdef HAVE_RES_NSEARCH
	    rk_res_free(&state);
#endif
	    free(reply);
	    return NULL;
	}
    } while (size < len && len < rk_DNS_MAX_PACKET_SIZE);
#ifdef HAVE_RES_NSEARCH
    rk_res_free(&state);
#endif

    len = min(len, size);
    r = parse_reply(reply, len);
    free(reply);
    return r;
}

struct dns_reply * ROKEN_LIB_FUNCTION
dns_lookup(const char *domain, const char *type_name)
{
    int type;
    
    type = dns_string_to_type(type_name);
    if(type == -1) {
	if(_resolve_debug)
	    fprintf(stderr, "dns_lookup: unknown resource type: `%s'\n", 
		    type_name);
	return NULL;
    }
    return dns_lookup_int(domain, C_IN, type);
}

static int
compare_srv(const void *a, const void *b)
{
    const struct resource_record *const* aa = a, *const* bb = b;

    if((*aa)->u.srv->priority == (*bb)->u.srv->priority)
	return ((*aa)->u.srv->weight - (*bb)->u.srv->weight);
    return ((*aa)->u.srv->priority - (*bb)->u.srv->priority);
}

#ifndef HAVE_RANDOM
#define random() rand()
#endif

/* try to rearrange the srv-records by the algorithm in RFC2782 */
void ROKEN_LIB_FUNCTION
dns_srv_order(struct dns_reply *r)
{
    struct resource_record **srvs, **ss, **headp;
    struct resource_record *rr;
    int num_srv = 0;

#if defined(HAVE_INITSTATE) && defined(HAVE_SETSTATE)
    int state[256 / sizeof(int)];
    char *oldstate;
#endif

    for(rr = r->head; rr; rr = rr->next) 
	if(rr->type == rk_ns_t_srv)
	    num_srv++;

    if(num_srv == 0)
	return;

    srvs = malloc(num_srv * sizeof(*srvs));
    if(srvs == NULL)
	return; /* XXX not much to do here */
    
    /* unlink all srv-records from the linked list and put them in
       a vector */
    for(ss = srvs, headp = &r->head; *headp; )
	if((*headp)->type == rk_ns_t_srv) {
	    *ss = *headp;
	    *headp = (*headp)->next;
	    (*ss)->next = NULL;
	    ss++;
	} else
	    headp = &(*headp)->next;
    
    /* sort them by priority and weight */
    qsort(srvs, num_srv, sizeof(*srvs), compare_srv);

#if defined(HAVE_INITSTATE) && defined(HAVE_SETSTATE)
    oldstate = initstate(time(NULL), (char*)state, sizeof(state));
#endif

    headp = &r->head;
    
    for(ss = srvs; ss < srvs + num_srv; ) {
	int sum, rnd, count;
	struct resource_record **ee, **tt;
	/* find the last record with the same priority and count the
           sum of all weights */
	for(sum = 0, tt = ss; tt < srvs + num_srv; tt++) {
	    assert(*tt != NULL);
	    if((*tt)->u.srv->priority != (*ss)->u.srv->priority)
		break;
	    sum += (*tt)->u.srv->weight;
	}
	ee = tt;
	/* ss is now the first record of this priority and ee is the
           first of the next */
	while(ss < ee) {
	    rnd = random() % (sum + 1);
	    for(count = 0, tt = ss; ; tt++) {
		if(*tt == NULL)
		    continue;
		count += (*tt)->u.srv->weight;
		if(count >= rnd)
		    break;
	    }

	    assert(tt < ee);

	    /* insert the selected record at the tail (of the head) of
               the list */
	    (*tt)->next = *headp;
	    *headp = *tt;
	    headp = &(*tt)->next;
	    sum -= (*tt)->u.srv->weight;
	    *tt = NULL;
	    while(ss < ee && *ss == NULL)
		ss++;
	}
    }
    
#if defined(HAVE_INITSTATE) && defined(HAVE_SETSTATE)
    setstate(oldstate);
#endif
    free(srvs);
    return;
}

#else /* NOT defined(HAVE_RES_SEARCH) && defined(HAVE_DN_EXPAND) */

struct dns_reply * ROKEN_LIB_FUNCTION
dns_lookup(const char *domain, const char *type_name)
{
    return NULL;
}

void ROKEN_LIB_FUNCTION
dns_free_data(struct dns_reply *r)
{
}

void ROKEN_LIB_FUNCTION
dns_srv_order(struct dns_reply *r)
{
}

#endif
