MDNS/src/include/Network/Mdns/Message.h

Go to the documentation of this file.

/****
 * 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.
 *
 * Message.h
 *
 ****/

#pragma once

#include "Question.h"
#include "Answer.h"

namespace mDNS
{
constexpr uint32_t MDNS_IP{0xFB0000E0}; // 224.0.0.251
constexpr uint16_t MDNS_TARGET_PORT{5353};
constexpr uint16_t MDNS_SOURCE_PORT{5353};
constexpr uint16_t MDNS_TTL{255};

constexpr uint16_t MAX_PACKET_SIZE{1024};

class Message
{
public:
    enum class Type {
        query,
        reply,
    };

    Message(IpAddress remoteIp, uint16_t remotePort, void* data, uint16_t size)
        : remoteIp(remoteIp), remotePort(remotePort), data(static_cast<uint8_t*>(data)), size(size)
    {
    }

    Message(const Message& other)
        : Message(other.getRemoteIp(), other.getRemotePort(), other.getData(), other.getSize())
    {
    }

    bool parse();

    IpAddress getRemoteIp() const
    {
        return remoteIp;
    }

    uint16_t getRemotePort() const
    {
        return remotePort;
    }

    bool isReply() const
    {
        return data[2] & 0x80;
    }

    Type getType() const
    {
        return isReply() ? Type::reply : Type::query;
    }

    bool isTruncated() const
    {
        return data[2] & 0x02;
    }

    uint8_t getResponseCode() const
    {
        return data[3] & 0x0f;
    }

    uint8_t* getData() const
    {
        return data;
    }

    uint16_t getSize() const
    {
        return size;
    }

    Answer* operator[](ResourceType type);

    // Writing
    void allocate(uint16_t recordSize)
    {
        size += recordSize;
    }

    /*
     * Resolve a 16-bit 'pointer' to a memory location
     *
     * Value represents a 16-bit offset from the start of the message data.
     * DNS names may contain pointers, but we use this approach internally to improve
     * data portability, reduce memory consumption and avoid data duplication during
     * message parsing and construction.
     */
    uint8_t* resolvePointer(uint16_t pointer) const
    {
        return data + pointer;
    }

    Question::OwnedList questions;
    Answer::OwnedList answers;

protected:
    IpAddress remoteIp;
    uint16_t remotePort;
    uint8_t* data;
    uint16_t size;
};

} // namespace mDNS