144 lines
3.6 KiB
C++
144 lines
3.6 KiB
C++
#include "./DNSServer.h"
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#include <lwip/def.h>
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#include <Arduino.h>
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#define DEBUG
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#define DEBUG_OUTPUT Serial
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DNSServer::DNSServer() {
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_ttl = htonl(60);
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_errorReplyCode = DNSReplyCode::NonExistentDomain;
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}
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bool DNSServer::start(const uint16_t &port, const String &domainName,
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const IPAddress &resolvedIP) {
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_port = port;
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_domainName = domainName;
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_resolvedIP[0] = resolvedIP[0];
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_resolvedIP[1] = resolvedIP[1];
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_resolvedIP[2] = resolvedIP[2];
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_resolvedIP[3] = resolvedIP[3];
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downcaseAndRemoveWwwPrefix(_domainName);
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return _udp.begin(_port) == 1;
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}
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void DNSServer::setErrorReplyCode(const DNSReplyCode &replyCode) {
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_errorReplyCode = replyCode;
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}
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void DNSServer::setTTL(const uint32_t &ttl) {
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_ttl = htonl(ttl);
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}
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void DNSServer::stop() {
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_udp.stop();
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}
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void DNSServer::downcaseAndRemoveWwwPrefix(String &domainName) {
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domainName.toLowerCase();
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domainName.replace("www.", "");
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}
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void DNSServer::processNextRequest() {
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_currentPacketSize = _udp.parsePacket();
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if (_currentPacketSize) {
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_buffer = (unsigned char*) malloc(_currentPacketSize * sizeof(char));
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_udp.read(_buffer, _currentPacketSize);
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_dnsHeader = (DNSHeader*) _buffer;
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if (_dnsHeader->QR == DNS_QR_QUERY &&
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_dnsHeader->OPCode == DNS_OPCODE_QUERY &&
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requestIncludesOnlyOneQuestion() &&
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(_domainName == "*" || getDomainNameWithoutWwwPrefix() == _domainName)
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) {
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replyWithIP();
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} else if (_dnsHeader->QR == DNS_QR_QUERY) {
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replyWithCustomCode();
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}
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free(_buffer);
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}
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}
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bool DNSServer::requestIncludesOnlyOneQuestion() {
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return ntohs(_dnsHeader->QDCount) == 1 &&
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_dnsHeader->ANCount == 0 &&
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_dnsHeader->NSCount == 0 &&
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_dnsHeader->ARCount == 0;
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}
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String DNSServer::getDomainNameWithoutWwwPrefix() {
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String parsedDomainName = "";
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unsigned char *start = _buffer + 12;
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if (*start == 0) {
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return parsedDomainName;
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}
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int pos = 0;
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while (true) {
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unsigned char labelLength = *(start + pos);
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for (int i = 0; i < labelLength; i++) {
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pos++;
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parsedDomainName += (char)*(start + pos);
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}
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pos++;
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if (*(start + pos) == 0) {
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downcaseAndRemoveWwwPrefix(parsedDomainName);
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return parsedDomainName;
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} else {
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parsedDomainName += ".";
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}
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}
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}
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void DNSServer::replyWithIP() {
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_dnsHeader->QR = DNS_QR_RESPONSE;
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_dnsHeader->ANCount = _dnsHeader->QDCount;
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_dnsHeader->QDCount = _dnsHeader->QDCount;
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//_dnsHeader->RA = 1;
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_udp.beginPacket(_udp.remoteIP(), _udp.remotePort());
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_udp.write(_buffer, _currentPacketSize);
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_udp.write((uint8_t) 192); // answer name is a pointer
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_udp.write((uint8_t) 12); // pointer to offset at 0x00c
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_udp.write((uint8_t) 0); // 0x0001 answer is type A query (host address)
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_udp.write((uint8_t) 1);
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_udp.write((uint8_t) 0); //0x0001 answer is class IN (internet address)
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_udp.write((uint8_t) 1);
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_udp.write((unsigned char*) &_ttl, 4);
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// Length of RData is 4 bytes (because, in this case, RData is IPv4)
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_udp.write((uint8_t) 0);
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_udp.write((uint8_t) 4);
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_udp.write(_resolvedIP, sizeof(_resolvedIP));
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_udp.endPacket();
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#ifdef DEBUG
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DEBUG_OUTPUT.print("DNS responds: ");
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DEBUG_OUTPUT.print(_resolvedIP[0]);
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DEBUG_OUTPUT.print(".");
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DEBUG_OUTPUT.print(_resolvedIP[1]);
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DEBUG_OUTPUT.print(".");
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DEBUG_OUTPUT.print(_resolvedIP[2]);
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DEBUG_OUTPUT.print(".");
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DEBUG_OUTPUT.print(_resolvedIP[3]);
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DEBUG_OUTPUT.print(" for ");
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DEBUG_OUTPUT.println(getDomainNameWithoutWwwPrefix());
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#endif
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}
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void DNSServer::replyWithCustomCode() {
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_dnsHeader->QR = DNS_QR_RESPONSE;
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_dnsHeader->RCode = (unsigned char) _errorReplyCode;
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_dnsHeader->QDCount = 0;
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_udp.beginPacket(_udp.remoteIP(), _udp.remotePort());
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_udp.write(_buffer, sizeof(DNSHeader));
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_udp.endPacket();
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}
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