#include "byte.h"
#include "dnsresolv.h"
#include "ip.h"
#include "stralloc.h"
#include "uint_t.h"

/**
	@file dns_ip.c
	@authors djb, fefe, feh
	@ref ucspi-tcp6
	@brief DNS IP query
*/

static char *q = 0;

int dns_ip4_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_A))
      if (byte_equal(header + 2, 2, DNS_C_IN))
        if (datalen == 4) {
          if (!dns_packet_copy(buf, len, pos, header, 4)) return DNS_ERR;
          if (!stralloc_catb(out, header, 4)) return DNS_MEM;
        }
    pos += datalen;
    ++ranswers;
  }

  dns_sortip4(out->s, out->len);
  return ranswers;
}

int dns_ip4(stralloc *out, stralloc *fqdn)
{
  unsigned int i;
  char code = 0;
  int dot = 0;
  char ch;
  char ip[4];
  int r;
  int rc = 0;

  if (!stralloc_copys(out, "")) return DNS_MEM;
  if (!stralloc_readyplus(fqdn, 1)) return DNS_MEM;

  fqdn->s[fqdn->len] = 0; /* test FQDN string */
  for (i = 1; i < fqdn->len; i++) {
    if (fqdn->s[i] >= '_') {
      code = 127;
      break;
    }
    if (fqdn->s[i] == '.') dot++;
  }

  if (code != 127 && dot == 3) /* if FQDN is just IPv4 */
    if (ip4_scan(fqdn->s, ip) || ip4_scanbracket(fqdn->s, ip)) {
      if (!stralloc_copyb(out, ip, 4)) return DNS_MEM;
      return 1;
    }

  code = 0;
  for (i = 0; i <= fqdn->len; ++i) {
    if (i < fqdn->len)
      ch = fqdn->s[i];
    else
      ch = '.';

    if ((ch == '[') || (ch == ']')) continue;
    if (ch == '.') {
      if (!stralloc_append(out, &code)) return DNS_MEM;
      code = 0;
      continue;
    }
    if ((ch >= '0') && (ch <= '9')) {
      code *= 10;
      code += ch - '0';
      continue;
    }

    if (dns_domain_fromdot(&q, fqdn->s, fqdn->len) <= 0) return DNS_ERR;  // fdqn -> A query -> response
    if (dns_resolve(q, DNS_T_A) >= 0) {
      if ((r = dns_ip4_packet(out, dns_resolve_tx.packet, dns_resolve_tx.packetlen)) < 0) return DNS_ERR;
      dns_transmit_free(&dns_resolve_tx);
      dns_domain_free(&q);
      rc += r;
    }

    return rc;
  }

  out->len &= ~3;
  return 0;
}

int dns_ip6_packet(stralloc *out, const char *buf, unsigned int len)
{
  unsigned int pos;
  char header[16];
  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_AAAA)) {
      if (byte_equal(header + 2, 2, DNS_C_IN))
        if (datalen == 16) {
          if (!dns_packet_copy(buf, len, pos, header, 16)) return DNS_ERR;
          if (!stralloc_catb(out, header, 16)) return DNS_MEM;
        }
    } else if (byte_equal(header, 2, DNS_T_A))
      if (byte_equal(header + 2, 2, DNS_C_IN))
        if (datalen == 4) {
          byte_copy(header, 12, V4mappedprefix);
          if (!dns_packet_copy(buf, len, pos, header + 12, 4)) return DNS_ERR;
          if (!stralloc_catb(out, header, 16)) return DNS_MEM;
        }
    pos += datalen;
    ++ranswers;
  }

  dns_sortip6(out->s, out->len);
  return ranswers;
}

int dns_ip6(stralloc *out, stralloc *fqdn)
{
  unsigned int i;
  char code;
  char ch;
  char ip[16];
  int r;
  int rc = 0;

  if (!stralloc_copys(out, "")) return DNS_MEM;
  if (!stralloc_readyplus(fqdn, 1)) return DNS_MEM;

  fqdn->s[fqdn->len] = 0; /* if FQDN is just IPv6 */
  if (ip6_scan(fqdn->s, ip) || ip6_scanbracket(fqdn->s, ip)) {
    if (!stralloc_copyb(out, ip, 16)) return DNS_MEM;
    return 1;
  }

  code = 0;
  for (i = 0; i <= fqdn->len; ++i) {
    if (i < fqdn->len)
      ch = fqdn->s[i];
    else
      ch = '.';

    if ((ch == '[') || (ch == ']')) continue;
    if (ch == '.') {
      if (!stralloc_append(out, &code)) return DNS_MEM;
      code = 0;
      continue;
    }
    if ((ch >= '0') && (ch <= '9')) {
      code *= 10;
      code += ch - '0';
      continue;
    }

    if (dns_domain_fromdot(&q, fqdn->s, fqdn->len) <= 0)
      return DNS_ERR;  // fqdn -> AAAA query -> response
    if (dns_resolve(q, DNS_T_AAAA) >= 0) {
      if ((r = dns_ip6_packet(out, dns_resolve_tx.packet, dns_resolve_tx.packetlen)) < 0) return DNS_ERR;
      dns_transmit_free(&dns_resolve_tx);
      dns_domain_free(&q);
      rc += r;
    }

    return rc;
  }

  out->len &= ~3;
  return 0;
}