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#include "dnsserver.h"
DNSServer::DNSServer()
{
_ttl = htonl(600);
_errorReplyCode = DNSReplyCode::NonExistentDomain;
}
bool DNSServer::start(const IPAddress &resolvedIP)
{
_buffer = NULL;
_resolvedIP[0] = resolvedIP[0];
_resolvedIP[1] = resolvedIP[1];
_resolvedIP[2] = resolvedIP[2];
_resolvedIP[3] = resolvedIP[3];
return _udp.begin(53) == 1;
}
void DNSServer::stop()
{
_udp.stop();
free(_buffer);
_buffer = NULL;
}
void DNSServer::processNextRequest()
{
_currentPacketSize = _udp.parsePacket();
if (_currentPacketSize)
{
if (_buffer != NULL) free(_buffer);
_buffer = (unsigned char*)malloc(_currentPacketSize * sizeof(char));
if (_buffer == NULL) return;
_udp.read(_buffer, _currentPacketSize);
_dnsHeader = (DNSHeader*) _buffer;
if (_dnsHeader->QR == DNS_QR_QUERY &&
_dnsHeader->OPCode == DNS_OPCODE_QUERY &&
requestIncludesOnlyOneQuestion())
{
replyWithIP(); // reply with the same ip regardless of request
}
}
}
bool DNSServer::requestIncludesOnlyOneQuestion()
{
return ntohs(_dnsHeader->QDCount) == 1 &&
_dnsHeader->ANCount == 0 &&
_dnsHeader->NSCount == 0 &&
_dnsHeader->ARCount == 0;
}
void DNSServer::replyWithIP()
{
if (_buffer == NULL) return;
_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();
}
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