void DNSServer::onReceive(pbuf* buf, IPAddress remoteIP, uint16_t remotePort)
{
if (_buffer != NULL) free(_buffer);
_buffer = (char*)malloc(buf->tot_len * sizeof(char));
if (_buffer == NULL) return;
pbuf_copy_partial(buf, _buffer, buf->tot_len, 0);
debugf("DNS REQ for %s from %s:%d", getDomainNameWithoutWwwPrefix().c_str(), remoteIP.toString().c_str(), remotePort);
_dnsHeader = (DNSHeader*) _buffer;
if (_dnsHeader->QR == DNS_QR_QUERY &&
_dnsHeader->OPCode == DNS_OPCODE_QUERY &&
requestIncludesOnlyOneQuestion() &&
(_domainName == "*" || getDomainNameWithoutWwwPrefix() == _domainName)
)
{
char response[buf->tot_len+16];
int idx = buf->tot_len;
_dnsHeader->QR = DNS_QR_RESPONSE;
_dnsHeader->ANCount = _dnsHeader->QDCount;
_dnsHeader->QDCount = _dnsHeader->QDCount;
memcpy(response, _buffer, idx);
//Set a pointer to the domain name in the question section
response[idx] = 0xC0;
response[idx+1] = 0x0C;
//Type: "Host Address"
response[idx+2] = 0x00;
response[idx+3] = 0x01;
//Set the response class to IN
response[idx+4] = 0x00;
response[idx+5] = 0x01;
//TTL
response[idx+6] = _ttl >> 24;
response[idx+7] = _ttl >> 16;
response[idx+8] = _ttl >> 8;
response[idx+9] = _ttl;
//RDATA length
response[idx+10] = 0x00;
response[idx+11] = 0x04; //4 byte IP address
//The IP address
response[idx+12] = _resolvedIP[0];
response[idx+13] = _resolvedIP[1];
response[idx+14] = _resolvedIP[2];
response[idx+15] = _resolvedIP[3];
sendTo(remoteIP, remotePort, response, idx+16);
}
void DNSServer::processNextRequest()
{
_currentPacketSize = _udp.parsePacket();
if (_currentPacketSize)
{
_buffer = (unsigned char*)malloc(_currentPacketSize * sizeof(char));
_udp.read(_buffer, _currentPacketSize);
_dnsHeader = (DNSHeader*) _buffer;
if (_dnsHeader->QR == DNS_QR_QUERY &&
_dnsHeader->OPCode == DNS_OPCODE_QUERY &&
requestIncludesOnlyOneQuestion() &&
(_domainName == "*" || getDomainNameWithoutWwwPrefix() == _domainName)
)
{
replyWithIP();
}
else if (_dnsHeader->QR == DNS_QR_QUERY)
{
replyWithCustomCode();
}
free(_buffer);
}
}
void DNSServer::replyWithIP()
{
_dnsHeader->QR = DNS_QR_RESPONSE;
_dnsHeader->ANCount = _dnsHeader->QDCount;
_dnsHeader->QDCount = _dnsHeader->QDCount;
//_dnsHeader->RA = 1;
_udp.beginPacket(_udp.remoteIP(), _udp.remotePort());
_udp.write(_buffer, _currentPacketSize);
_udp.write((uint8_t)192); // answer name is a pointer
_udp.write((uint8_t)12); // pointer to offset at 0x00c
_udp.write((uint8_t)0); // 0x0001 answer is type A query (host address)
_udp.write((uint8_t)1);
_udp.write((uint8_t)0); //0x0001 answer is class IN (internet address)
_udp.write((uint8_t)1);
_udp.write((unsigned char*)&_ttl, 4);
// Length of RData is 4 bytes (because, in this case, RData is IPv4)
_udp.write((uint8_t)0);
_udp.write((uint8_t)4);
_udp.write(_resolvedIP, sizeof(_resolvedIP));
_udp.endPacket();
#ifdef DEBUG
DEBUG_OUTPUT.print("DNS responds: ");
DEBUG_OUTPUT.print(_resolvedIP[0]);
DEBUG_OUTPUT.print(".");
DEBUG_OUTPUT.print(_resolvedIP[1]);
DEBUG_OUTPUT.print(".");
DEBUG_OUTPUT.print(_resolvedIP[2]);
DEBUG_OUTPUT.print(".");
DEBUG_OUTPUT.print(_resolvedIP[3]);
DEBUG_OUTPUT.print(" for ");
DEBUG_OUTPUT.println(getDomainNameWithoutWwwPrefix());
#endif
}
