#include "byte.h"
#include "case.h"
#include "dnsresolv.h"
#include "ip.h"
#include "stralloc.h"
#include "uint_t.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;
}