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#include "stralloc.h"
#include "uint_t.h"
#include "byte.h"
#include "ip.h"
#include "case.h"
#include "dnsresolv.h"
/**
@file dns_cname.c
@author feh
@brief DNS cname lookup
*/
static char *q = 0;
int dns_cname_packet(stralloc *out,const char *buf,unsigned int len)
{
unsigned int pos;
char header[12];
uint16 numanswers;
uint16 datalen;
int ranswers = 0;
if (!stralloc_copys(out,"")) return DNS_MEM;
pos = dns_packet_copy(buf,len,0,header,12); if (!pos) return DNS_ERR;
uint16_unpack_big(header + 6,&numanswers);
pos = dns_packet_skipname(buf,len,pos); if (!pos) return DNS_ERR;
pos += 4;
while (numanswers--) {
pos = dns_packet_skipname(buf,len,pos); if (!pos) return DNS_ERR;
pos = dns_packet_copy(buf,len,pos,header,10); if (!pos) return DNS_ERR;
uint16_unpack_big(header + 8,&datalen);
if (byte_equal(header,2,DNS_T_CNAME))
if (byte_equal(header + 2,2,DNS_C_IN)) {
if (!dns_packet_getname(buf,len,pos,&q)) return DNS_ERR;
if (dns_domain_todot_cat(out,q) <= 0) return DNS_ERR;
}
pos += datalen;
++ranswers;
}
return ranswers;
}
int dns_cname(stralloc *out,stralloc *fqdn)
{
int rc;
if (dns_domain_fromdot(&q,fqdn->s,fqdn->len) <= 0) return DNS_ERR;
if (dns_resolve(q,DNS_T_CNAME) < 0) return DNS_ERR;
if ((rc = dns_cname_packet(out,dns_resolve_tx.packet,dns_resolve_tx.packetlen)) < 0) return DNS_ERR;
dns_transmit_free(&dns_resolve_tx);
dns_domain_free(&q);
if (case_equals(out->s,fqdn->s)) rc = -6; // loop DNS_HARD
return rc;
}
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