/* $Id$*/

 /*
  *
  * Copyright (C) 2001-2003 Fhg Fokus
  *
  * This file is part of ser, a free SIP server.
  *
  * ser 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
  *
  * For a license to use the ser software under conditions
  * other than those described here, or to purchase support for this
  * software, please contact iptel.org by e-mail at the following addresses:
  *    info@iptel.org
  *
  * ser 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
  */

 /*
  * History:
  * -------
  *  2003-02-13  added proto to sip_resolvehost, for SRV lookups (andrei)
  */ 

 #include <sys/types.h>

 #include <netinet/in.h>

 #include <arpa/nameser.h>

 #include <resolv.h>
 #include <string.h>
 
 #include "resolve.h"
 #include "dprint.h"
 #include "mem/mem.h"

 #include "ip_addr.h"

 
 
 
 /* mallocs for local stuff */
 #define local_malloc pkg_malloc
 #define local_free   pkg_free
 
 
 
  /*  skips over a domain name in a dns message
  *  (it can be  a sequence of labels ending in \0, a pointer or
  *   a sequence of labels ending in a pointer -- see rfc1035
  *   returns pointer after the domain name or null on error*/
 unsigned char* dns_skipname(unsigned char* p, unsigned char* end)
 {
 	while(p<end){
 		/* check if \0 (root label length) */
 		if (*p==0){
 			p+=1;
 			break;
 		}
 		/* check if we found a pointer */
 		if (((*p)&0xc0)==0xc0){
 			/* if pointer skip over it (2 bytes) & we found the end */
 			p+=2;
 			break;
 		}
 		/* normal label */
 		p+=*p+1;
 	}

 	return (p>=end)?0:p;

 }
 
 
 
 /* parses the srv record into a srv_rdata structure
  *   msg   - pointer to the dns message
  *   end   - pointer to the end of the message
  *   rdata - pointer  to the rdata part of the srv answer
  * returns 0 on error, or a dyn. alloc'ed srv_rdata structure */
 /* SRV rdata format:
  *            111111
  *  0123456789012345
  * +----------------+
  * |     priority   |
  * |----------------|
  * |     weight     |
  * |----------------|
  * |   port number  |
  * |----------------|
  * |                |
  * ~      name      ~
  * |                |
  * +----------------+
  */
 struct srv_rdata* dns_srv_parser( unsigned char* msg, unsigned char* end,
 								  unsigned char* rdata)
 {
 	struct srv_rdata* srv;
 	int len;
 	
 	srv=0;

 	if ((rdata+6)>=end) goto error;

 	srv=(struct srv_rdata*)local_malloc(sizeof(struct srv_rdata));
 	if (srv==0){

 		LOG(L_ERR, "ERROR: dns_srv_parser: out of memory\n");

 		goto error;
 	}
 	
 	memcpy((void*)&srv->priority, rdata, 2);
 	memcpy((void*)&srv->weight,   rdata+2, 2);
 	memcpy((void*)&srv->port,     rdata+4, 2);
 	rdata+=6;
 	srv->priority=ntohs(srv->priority);
 	srv->weight=ntohs(srv->weight);
 	srv->port=ntohs(srv->port);

 	if ((len=dn_expand(msg, end, rdata, srv->name, MAX_DNS_NAME-1))==-1)

 		goto error;

 	/* add terminating 0 ? (warning: len=compressed name len) */

 	return srv;
 error:
 	if (srv) local_free(srv);
 	return 0;
 }
 
 

 /* parses the naptr record into a naptr_rdata structure
  *   msg   - pointer to the dns message
  *   end   - pointer to the end of the message
  *   rdata - pointer  to the rdata part of the naptr answer
  * returns 0 on error, or a dyn. alloc'ed naptr_rdata structure */
 /* NAPTR rdata format:
  *            111111
  *  0123456789012345
  * +----------------+
  * |      order     |
  * |----------------|
  * |   preference   |
  * |----------------|
  * ~     flags      ~
  * |   (string)     |
  * |----------------|
  * ~    services    ~
  * |   (string)     |
  * |----------------|
  * ~    regexp      ~
  * |   (string)     |
  * |----------------|
  * ~  replacement   ~
    |    (name)      |
  * +----------------+
  */
 struct naptr_rdata* dns_naptr_parser( unsigned char* msg, unsigned char* end,
 								  unsigned char* rdata)
 {
 	struct naptr_rdata* naptr;
 	int len;
 	
 	naptr = 0;
 	if ((rdata + 7) >= end) goto error;
 	naptr=(struct naptr_rdata*)local_malloc(sizeof(struct naptr_rdata));
 	if (naptr == 0){
 		LOG(L_ERR, "ERROR: dns_naptr_parser: out of memory\n");
 		goto error;
 	}
 	
 	memcpy((void*)&naptr->order, rdata, 2);
 	naptr->order=ntohs(naptr->order);
 	memcpy((void*)&naptr->pref, rdata + 2, 2);
 	naptr->pref=ntohs(naptr->pref);
 	naptr->flags_len = (int)rdata[4];
 	if ((rdata + 7 +  naptr->flags_len) >= end) goto error;
 	memcpy((void*)&naptr->flags, rdata + 5, naptr->flags_len);
 	naptr->services_len = (int)rdata[5 + naptr->flags_len];
 	if ((rdata + 7 + naptr->flags_len + naptr->services_len) >= end) goto error;
 	memcpy((void*)&naptr->services, rdata + 6 + naptr->flags_len, naptr->services_len);
 	naptr->regexp_len = (int)rdata[6 + naptr->flags_len + naptr->services_len];
 	if ((rdata + 7 + naptr->flags_len + naptr->services_len +
 					naptr->regexp_len) >= end) goto error;
 	memcpy((void*)&naptr->regexp, rdata + 7 + naptr->flags_len +
 				naptr->services_len, naptr->regexp_len);
 	rdata = rdata + 7 + naptr->flags_len + naptr->services_len + 
 			naptr->regexp_len;
 	if ((len=dn_expand(msg, end, rdata, naptr->repl, MAX_DNS_NAME-1)) == -1)
 		goto error;
 	/* add terminating 0 ? (warning: len=compressed name len) */
 	return naptr;
 error:
 	if (naptr) local_free(naptr);
 	return 0;
 }
 
 

 /* parses a CNAME record into a cname_rdata structure */
 struct cname_rdata* dns_cname_parser( unsigned char* msg, unsigned char* end,
 									  unsigned char* rdata)
 {
 	struct cname_rdata* cname;
 	int len;
 	
 	cname=0;
 	cname=(struct cname_rdata*)local_malloc(sizeof(struct cname_rdata));
 	if(cname==0){
 		LOG(L_ERR, "ERROR: dns_cname_parser: out of memory\n");
 		goto error;
 	}
 	if ((len=dn_expand(msg, end, rdata, cname->name, MAX_DNS_NAME-1))==-1)
 		goto error;
 	return cname;
 error:
 	if (cname) local_free(cname);
 	return 0;
 }
 
 
 

 /* parses an A record rdata into an a_rdata structure
  * returns 0 on error or a dyn. alloc'ed a_rdata struct
  */
 struct a_rdata* dns_a_parser(unsigned char* rdata, unsigned char* end)
 {
 	struct a_rdata* a;
 	

 	if (rdata+4>=end) goto error;

 	a=(struct a_rdata*)local_malloc(sizeof(struct a_rdata));
 	if (a==0){
 		LOG(L_ERR, "ERROR: dns_a_parser: out of memory\n");
 		goto error;
 	}
 	memcpy(a->ip, rdata, 4);
 	return a;
 error:
 	return 0;
 }
 
 
 
 /* parses an AAAA (ipv6) record rdata into an aaaa_rdata structure
  * returns 0 on error or a dyn. alloc'ed aaaa_rdata struct */
 struct aaaa_rdata* dns_aaaa_parser(unsigned char* rdata, unsigned char* end)
 {
 	struct aaaa_rdata* aaaa;
 	

 	if (rdata+16>=end) goto error;

 	aaaa=(struct aaaa_rdata*)local_malloc(sizeof(struct aaaa_rdata));
 	if (aaaa==0){
 		LOG(L_ERR, "ERROR: dns_aaaa_parser: out of memory\n");
 		goto error;
 	}
 	memcpy(aaaa->ip6, rdata, 16);
 	return aaaa;
 error:
 	return 0;
 }
 
 
 
 /* frees completely a struct rdata list */
 void free_rdata_list(struct rdata* head)
 {
 	struct rdata* l;
 	for(l=head; l; l=l->next){
 		/* free the parsed rdata*/
 		if (l->rdata) local_free(l->rdata);
 		local_free(l);
 	}
 }
 
 
 
 /* gets the DNS records for name:type
  * returns a dyn. alloc'ed struct rdata linked list with the parsed responses
  * or 0 on error
  * see rfc1035 for the query/response format */
 struct rdata* get_record(char* name, int type)
 {
 	int size;
 	int qno, answers_no;

 	int r;

 	int ans_len;
 	static union dns_query buff;
 	unsigned char* p;
 	unsigned char* t;
 	unsigned char* end;
 	static unsigned char answer[ANS_SIZE];
 	unsigned short rtype, class, rdlength;
 	unsigned int ttl;
 	struct rdata* head;
 	struct rdata** crt;

 	struct rdata** last;

 	struct rdata* rd;
 	struct srv_rdata* srv_rd;
 	struct srv_rdata* crt_srv;
 	
 	size=res_search(name, C_IN, type, buff.buff, sizeof(buff));

 	if (size<0) {

 		DBG("get_record: lookup(%s, %d) failed\n", name, type);
 		goto not_found;

 	}

 	else if (size > sizeof(buff)) size=sizeof(buff);

 	head=rd=0;
 	last=crt=&head;

 	
 	p=buff.buff+DNS_HDR_SIZE;
 	end=buff.buff+size;

 	if (p>=end) goto error_boundary;

 	qno=ntohs((unsigned short)buff.hdr.qdcount);
 
 	for (r=0; r<qno; r++){
 		/* skip the name of the question */

 		if ((p=dns_skipname(p, end))==0) {
 			LOG(L_ERR, "ERROR: get_record: skipname==0\n");
 			goto error;
 		}

 		p+=2+2; /* skip QCODE & QCLASS */
 	#if 0
 		for (;(p<end && (*p)); p++);
 		p+=1+2+2; /* skip the ending  '\0, QCODE and QCLASS */
 	#endif

 		if (p>=end) {
 			LOG(L_ERR, "ERROR: get_record: p>=end\n");

 			goto error;
 		}

 	};
 	answers_no=ntohs((unsigned short)buff.hdr.ancount);
 	ans_len=ANS_SIZE;
 	t=answer;
 	for (r=0; (r<answers_no) && (p<end); r++){
 		/*  ignore it the default domain name */

 		if ((p=dns_skipname(p, end))==0) {
 			LOG(L_ERR, "ERROR: get_record: skip_name=0 (#2)\n");
 			goto error;
 		}

 		/*
 		skip=dn_expand(buff.buff, end, p, t, ans_len);
 		p+=skip;
 		*/

 		/* check if enough space is left for type, class, ttl & size */
 		if ((p+2+2+4+2)>=end) goto error_boundary;

 		/* get type */
 		memcpy((void*) &rtype, (void*)p, 2);
 		rtype=ntohs(rtype);
 		p+=2;
 		/* get  class */
 		memcpy((void*) &class, (void*)p, 2);
 		class=ntohs(class);
 		p+=2;
 		/* get ttl*/
 		memcpy((void*) &ttl, (void*)p, 4);
 		ttl=ntohl(ttl);
 		p+=4;
 		/* get size */
 		memcpy((void*)&rdlength, (void*)p, 2);
 		rdlength=ntohs(rdlength);
 		p+=2;
 		/* check for type */

 		/*

 		if (rtype!=type){

 			LOG(L_ERR, "WARNING: get_record: wrong type in answer (%d!=%d)\n",
 					rtype, type);

 			p+=rdlength;
 			continue;
 		}
 		*/

 		/* expand the "type" record  (rdata)*/
 		

 		rd=(struct rdata*) local_malloc(sizeof(struct rdata));
 		if (rd==0){
 			LOG(L_ERR, "ERROR: get_record: out of memory\n");
 			goto error;
 		}
 		rd->type=rtype;
 		rd->class=class;
 		rd->ttl=ttl;

 		rd->next=0;
 		switch(rtype){

 			case T_SRV:
 				srv_rd= dns_srv_parser(buff.buff, end, p);
 				rd->rdata=(void*)srv_rd;
 				if (srv_rd==0) goto error_parse;
 				

 				/* insert sorted into the list */

 				for (crt=&head; *crt; crt= &((*crt)->next)){
 					crt_srv=(struct srv_rdata*)(*crt)->rdata;
 					if ((srv_rd->priority <  crt_srv->priority) ||
 					   ( (srv_rd->priority == crt_srv->priority) && 
 							 (srv_rd->weight > crt_srv->weight) ) ){
 						/* insert here */

 						goto skip;

 					}
 				}

 				last=&(rd->next); /*end of for => this will be the last elem*/
 			skip:

 				/* insert here */
 				rd->next=*crt;
 				*crt=rd;
 				
 				break;
 			case T_A:
 				rd->rdata=(void*) dns_a_parser(p,end);
 				if (rd->rdata==0) goto error_parse;

 				*last=rd; /* last points to the last "next" or the list head*/
 				last=&(rd->next);

 				break;
 			case T_AAAA:
 				rd->rdata=(void*) dns_aaaa_parser(p,end);
 				if (rd->rdata==0) goto error_parse;

 				*last=rd;
 				last=&(rd->next);

 				break;

 			case T_CNAME:
 				rd->rdata=(void*) dns_cname_parser(buff.buff, end, p);
 				if(rd->rdata==0) goto error_parse;

 				*last=rd;
 				last=&(rd->next);

 				break;

 			case T_NAPTR:
 				rd->rdata=(void*) dns_naptr_parser(buff.buff, end, p);
 				if(rd->rdata==0) goto error_parse;
 				*last=rd;
 				last=&(rd->next);
 				break;

 			default:

 				LOG(L_ERR, "WARNING: get_record: unknown type %d\n", rtype);

 				rd->rdata=0;

 				*last=rd;
 				last=&(rd->next);

 		}
 		
 		p+=rdlength;
 		
 	}
 	return head;
 error_boundary:
 		LOG(L_ERR, "ERROR: get_record: end of query buff reached\n");
 		return 0;
 error_parse:
 		LOG(L_ERR, "ERROR: get_record: rdata parse error \n");
 		if (rd) local_free(rd); /* rd->rdata=0 & rd is not linked yet into
 								   the list */
 error:
 		LOG(L_ERR, "ERROR: get_record \n");
 		if (head) free_rdata_list(head);

 not_found:

 	return 0;
 }
 

 
 
 /* resolves a host name trying SRV lookup if *port==0 or normal A/AAAA lookup
  * if *port!=0.

  * when performing SRV lookup (*port==0) it will use proto to look for
  * tcp or udp hosts, otherwise proto is unused; if proto==0 => no SRV lookup

  * returns: hostent struct & *port filled with the port from the SRV record;
  *  0 on error
  */

 struct hostent* sip_resolvehost(str* name, unsigned short* port, int proto)

 {
 	struct hostent* he;
 	struct rdata* head;
 	struct rdata* l;
 	struct srv_rdata* srv;

 	struct ip_addr* ip;

 	static char tmp[MAX_DNS_NAME]; /* tmp. buff. for SRV lookups */
 
 	/* try SRV if no port specified (draft-ietf-sip-srv-06) */
 	if ((port)&&(*port==0)){
 		*port=SIP_PORT; /* just in case we don't find another */

 		if ((name->len+SRV_PREFIX_LEN+1)>MAX_DNS_NAME){

 			LOG(L_WARN, "WARNING: sip_resolvehost: domain name too long (%d),"

 						" unable to perform SRV lookup\n", name->len);

 		}else{

 			/* check if it's an ip address */

 			if ( ((ip=str2ip(name))!=0)

 #ifdef	USE_IPV6

 				  || ((ip=str2ip6(name))!=0)

 #endif
 				){
 				/* we are lucky, this is an ip address */

 				return ip_addr2he(name,ip);

 			}
 			

 			switch(proto){
 				case PROTO_NONE: /* no proto specified, use udp */
 					goto skip_srv;
 				case PROTO_UDP:
 					memcpy(tmp, SRV_UDP_PREFIX, SRV_PREFIX_LEN);
 					memcpy(tmp+SRV_PREFIX_LEN, name->s, name->len);
 					tmp[SRV_PREFIX_LEN + name->len] = '\0';
 					break;
 				case PROTO_TCP:
 					memcpy(tmp, SRV_TCP_PREFIX, SRV_PREFIX_LEN);
 					memcpy(tmp+SRV_PREFIX_LEN, name->s, name->len);
 					tmp[SRV_PREFIX_LEN + name->len] = '\0';
 					break;
 				default:
 					LOG(L_CRIT, "BUG: sip_resolvehost: unknown proto %d\n",
 							proto);
 					return 0;
 			}

 			head=get_record(tmp, T_SRV);
 			for(l=head; l; l=l->next){
 				if (l->type!=T_SRV) continue; /*should never happen*/
 				srv=(struct srv_rdata*) l->rdata;
 				if (srv==0){
 					LOG(L_CRIT, "sip_resolvehost: BUG: null rdata\n");
 					free_rdata_list(head);
 					break;
 				}
 				he=resolvehost(srv->name);
 				if (he!=0){
 					/* we found it*/
 					DBG("sip_resolvehost: SRV(%s) = %s:%d\n",
 							tmp, srv->name, srv->port);
 					*port=srv->port;
 					free_rdata_list(head); /*clean up*/
 					return he;
 				}
 			}

 			DBG("sip_resolvehost: not SRV record found for %.*s," 
 					" trying 'normal' lookup...\n", name->len, name->s);

 		}
 	}

 skip_srv:

 	if (name->len >= MAX_DNS_NAME) {
 		LOG(L_ERR, "sip_resolvehost: domain name too long\n");
 		return 0;
 	}
 	memcpy(tmp, name->s, name->len);
 	tmp[name->len] = '\0';
 	he=resolvehost(tmp);

 	return he;
 }