/* $Id$*/
/* #include <arpa/nameser.h> -- included from resolve.h*/
#include <netinet/in.h>
#include <resolv.h>
#include <string.h>
#include "resolve.h"
#include "dprint.h"
#include "mem/mem.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 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 fot 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;
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.
* returns: hostent struct & *port filled with the port from the SRV record;
* 0 on error
*/
struct hostent* sip_resolvehost(char* name, unsigned short* port)
{
struct hostent* he;
struct rdata* head;
struct rdata* l;
struct srv_rdata* srv;
static char tmp[MAX_DNS_NAME]; /* tmp. buff. for SRV lookups */
int len;
/* 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 */
len=strlen(name);
if ((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", len);
}else{
memcpy(tmp, SRV_PREFIX, SRV_PREFIX_LEN);
memcpy(tmp+SRV_PREFIX_LEN, name, len+1); /*include the ending 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);
}
}
he=resolvehost(name);
return he;
}