DnsServer.h

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/****
 * Sming Framework Project - Open Source framework for high efficiency native ESP8266 development.
 * Created 2015 by Skurydin Alexey
 * http://github.com/SmingHub/Sming
 * All files of the Sming Core are provided under the LGPL v3 license.
 *
 * DnsServer.h
 *
 * File Author: https://github.com/patrickjahns
 *
 * The code is a port of the following projects
 * https://github.com/israellot/esp-ginx/tree/master/app/dns
 * https://github.com/esp8266/Arduino/tree/master/libraries/DNSServer
 * Created on March 4, 2016
 *
 ****/

#pragma once

#include "UdpConnection.h"
#include <WString.h>
#include <IpAddress.h>

#define DNS_QR_QUERY 0
#define DNS_QR_RESPONSE 1
#define DNS_OPCODE_QUERY 0

enum class DnsReplyCode {
    NoError = 0,
    FormError = 1,
    ServerFailure = 2,
    NonExistentDomain = 3,
    NotImplemented = 4,
    Refused = 5,
    YXDomain = 6,
    YXRRSet = 7,
    NXRRSet = 8
};

struct DnsHeader {
    uint16_t ID;      // identification number
    char RD : 1;      // recursion desired
    char TC : 1;      // truncated message
    char AA : 1;      // authoritative answer
    char OPCode : 4;  // message_type
    char QR : 1;      // query/response flag
    char RCode : 4;   // response code
    char Z : 3;       // its z! reserved
    char RA : 1;      // recursion available
    uint16_t QDCount; // number of question entries
    uint16_t ANCount; // number of answer entries
    uint16_t NSCount; // number of authority entries
    uint16_t ARCount; // number of resource entries
};

class DnsServer : public UdpConnection
{
public:
    DnsServer()
    {
    }

    void setErrorReplyCode(DnsReplyCode replyCode)
    {
        errorReplyCode = replyCode;
    }

    void setTTL(uint32_t ttl)
    {
        this->ttl = ttl;
    }

    bool start(uint16_t port, const String& domainName, const IpAddress& resolvedIP);

    void stop();

protected:
    void onReceive(pbuf* buf, IpAddress remoteIP, uint16_t remotePort) override;

private:
    uint16_t port = 0;
    String domainName;
    IpAddress resolvedIP;
    char* buffer = nullptr;
    DnsHeader* dnsHeader = nullptr;
    uint32_t ttl = 60;
    DnsReplyCode errorReplyCode = DnsReplyCode::NonExistentDomain;

    static void downcaseAndRemoveWwwPrefix(String& domainName);
    String getDomainNameWithoutWwwPrefix();
    bool requestIncludesOnlyOneQuestion();
};