/*
 *  Copyright (c) 2016, The OpenThread Authors.
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. Neither the name of the copyright holder nor the
 *     names of its contributors may be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * @file
 *   This file includes definitions for ICMPv6.
 */

#ifndef ICMP6_HPP_
#define ICMP6_HPP_

#include "openthread-core-config.h"

#include <openthread/icmp6.h>

#include "common/encoding.hpp"
#include "common/linked_list.hpp"
#include "common/locator.hpp"
#include "net/ip6_headers.hpp"

namespace ot {
namespace Ip6 {

using ot::Encoding::BigEndian::HostSwap16;

/**
 * @addtogroup core-ip6-icmp6
 *
 * @brief
 *   This module includes definitions for ICMPv6.
 *
 * @{
 *
 */

/*
 * This class implements ICMPv6 header generation and parsing.
 *
 */
OT_TOOL_PACKED_BEGIN
class IcmpHeader : public otIcmp6Header
{
public:
    /**
     * This method initializes the ICMPv6 header to all zeros.
     *
     */
    void Init(void)
    {
        mType        = 0;
        mCode        = 0;
        mChecksum    = 0;
        mData.m32[0] = 0;
    }

    /**
     * ICMPv6 Message Types
     *
     */
    enum Type
    {
        kTypeDstUnreach   = OT_ICMP6_TYPE_DST_UNREACH,   ///< Destination Unreachable
        kTypePacketToBig  = OT_ICMP6_TYPE_PACKET_TO_BIG, ///< Packet To Big
        kTypeTimeExceeded = OT_ICMP6_TYPE_TIME_EXCEEDED, ///< Time Exceeded
        kTypeEchoRequest  = OT_ICMP6_TYPE_ECHO_REQUEST,  ///< Echo Request
        kTypeEchoReply    = OT_ICMP6_TYPE_ECHO_REPLY,    ///< Echo Reply
    };

    /**
     * ICMPv6 Message Codes
     *
     */
    enum Code
    {
        kCodeDstUnreachNoRoute = OT_ICMP6_CODE_DST_UNREACH_NO_ROUTE, ///< Destination Unreachable No Route
        kCodeFragmReasTimeEx   = OT_ICMP6_CODE_FRAGM_REAS_TIME_EX,   ///< Fragment Reassembly Time Exceeded
    };

    /**
     * This method returns the ICMPv6 message type.
     *
     * @returns The ICMPv6 message type.
     *
     */
    Type GetType(void) const { return static_cast<Type>(mType); }

    /**
     * This method sets the ICMPv6 message type.
     *
     * @param[in]  aType  The ICMPv6 message type.
     *
     */
    void SetType(Type aType) { mType = static_cast<uint8_t>(aType); }

    /**
     * This method returns the ICMPv6 message code.
     *
     * @returns The ICMPv6 message code.
     *
     */
    Code GetCode(void) const { return static_cast<Code>(mCode); }

    /**
     * This method sets the ICMPv6 message code.
     *
     * @param[in]  aCode  The ICMPv6 message code.
     */
    void SetCode(Code aCode) { mCode = static_cast<uint8_t>(aCode); }

    /**
     * This method returns the ICMPv6 message checksum.
     *
     * @returns The ICMPv6 message checksum.
     *
     */
    uint16_t GetChecksum(void) const { return HostSwap16(mChecksum); }

    /**
     * This method sets the ICMPv6 message checksum.
     *
     * @param[in]  aChecksum  The ICMPv6 message checksum.
     *
     */
    void SetChecksum(uint16_t aChecksum) { mChecksum = HostSwap16(aChecksum); }

    /**
     * This method returns the ICMPv6 message ID for Echo Requests and Replies.
     *
     * @returns The ICMPv6 message ID.
     *
     */
    uint16_t GetId(void) const { return HostSwap16(mData.m16[0]); }

    /**
     * This method sets the ICMPv6 message ID for Echo Requests and Replies.
     *
     * @param[in]  aId  The ICMPv6 message ID.
     *
     */
    void SetId(uint16_t aId) { mData.m16[0] = HostSwap16(aId); }

    /**
     * This method returns the ICMPv6 message sequence for Echo Requests and Replies.
     *
     * @returns The ICMPv6 message sequence.
     *
     */
    uint16_t GetSequence(void) const { return HostSwap16(mData.m16[1]); }

    /**
     * This method sets the ICMPv6 message sequence for Echo Requests and Replies.
     *
     * @param[in]  aSequence  The ICMPv6 message sequence.
     *
     */
    void SetSequence(uint16_t aSequence) { mData.m16[1] = HostSwap16(aSequence); }

    /**
     * This static method returns the byte offset of the Checksum field in the ICMPv6 header.
     *
     * @returns The byte offset of the Checksum field.
     *
     */
    static uint8_t GetChecksumOffset(void) { return offsetof(otIcmp6Header, mChecksum); }

    /**
     * This static method returns the byte offset of the ICMPv6 payload.
     *
     * @returns The Byte offset of the ICMPv6 payload.
     *
     */
    static uint8_t GetDataOffset(void) { return offsetof(otIcmp6Header, mData); }

} OT_TOOL_PACKED_END;

/**
 * This class implements ICMPv6 message handlers.
 *
 */
class IcmpHandler : public otIcmp6Handler, public LinkedListEntry<IcmpHandler>
{
    friend class Icmp;

public:
    /**
     * This constructor creates an ICMPv6 message handler.
     *
     * @param[in]  aCallback  A pointer to the function that is called when receiving an ICMPv6 message.
     * @param[in]  aContext   A pointer to arbitrary context information.
     *
     */
    IcmpHandler(otIcmp6ReceiveCallback aCallback, void *aContext)
    {
        mReceiveCallback = aCallback;
        mContext         = aContext;
        mNext            = NULL;
    }

private:
    void HandleReceiveMessage(Message &aMessage, const MessageInfo &aMessageInfo, const IcmpHeader &aIcmp6Header)
    {
        mReceiveCallback(mContext, &aMessage, &aMessageInfo, &aIcmp6Header);
    }
};

/**
 * This class implements ICMPv6.
 *
 */
class Icmp : public InstanceLocator
{
public:
    /**
     * This constructor initializes the object.
     *
     * @param[in]  aInstance A reference to the OpenThread instance.
     *
     */
    explicit Icmp(Instance &aInstance);

    /**
     * This method returns a new ICMP message with sufficient header space reserved.
     *
     * @param[in]  aReserved  The number of header bytes to reserve after the ICMP header.
     *
     * @returns A pointer to the message or NULL if no buffers are available.
     *
     */
    Message *NewMessage(uint16_t aReserved);

    /**
     * This method registers ICMPv6 handler.
     *
     * @param[in]  aHandler  A reference to the ICMPv6 handler.
     *
     * @retval OT_ERROR_NONE     Successfully registered the ICMPv6 handler.
     * @retval OT_ERROR_ALREADY  The ICMPv6 handler is already registered.
     *
     */
    otError RegisterHandler(IcmpHandler &aHandler);

    /**
     * This method sends an ICMPv6 Echo Request message.
     *
     * @param[in]  aMessage      A reference to the Echo Request payload.
     * @param[in]  aMessageInfo  A reference to the message info associated with @p aMessage.
     * @param[in]  aIdentifier   An identifier to aid in matching Echo Replies to this Echo Request.
     *                           May be zero.
     *
     * @retval OT_ERROR_NONE     Successfully enqueued the ICMPv6 Echo Request message.
     * @retval OT_ERROR_NO_BUFS  Insufficient buffers available to generate an ICMPv6 Echo Request message.
     *
     */
    otError SendEchoRequest(Message &aMessage, const MessageInfo &aMessageInfo, uint16_t aIdentifier);

    /**
     * This method sends an ICMPv6 error message.
     *
     * @param[in]  aType         The ICMPv6 message type.
     * @param[in]  aCode         The ICMPv6 message code.
     * @param[in]  aMessageInfo  A reference to the message info.
     * @param[in]  aHeader       The IPv6 header of the error-causing message.
     *
     * @retval OT_ERROR_NONE     Successfully enqueued the ICMPv6 error message.
     * @retval OT_ERROR_NO_BUFS  Insufficient buffers available.
     *
     */
    otError SendError(IcmpHeader::Type   aType,
                      IcmpHeader::Code   aCode,
                      const MessageInfo &aMessageInfo,
                      const Header &     aHeader);

    /**
     * This method handles an ICMPv6 message.
     *
     * @param[in]  aMessage      A reference to the ICMPv6 message.
     * @param[in]  aMessageInfo  A reference to the message info associated with @p aMessage.
     *
     * @retval OT_ERROR_NONE     Successfully processed the ICMPv6 message.
     * @retval OT_ERROR_NO_BUFS  Insufficient buffers available to generate the reply.
     * @retval OT_ERROR_DROP     The ICMPv6 message was invalid and dropped.
     *
     */
    otError HandleMessage(Message &aMessage, MessageInfo &aMessageInfo);

    /**
     * This method updates the ICMPv6 checksum.
     *
     * @param[in]  aMessage   A reference to the ICMPv6 message.
     * @param[in]  aChecksum  The pseudo-header checksum value.
     *
     */
    void UpdateChecksum(Message &aMessage, uint16_t aChecksum);

    /**
     * This method indicates whether or not ICMPv6 Echo processing is enabled.
     *
     * @retval TRUE   ICMPv6 Echo processing is enabled.
     * @retval FALSE  ICMPv6 Echo processing is disabled.
     *
     */
    otIcmp6EchoMode GetEchoMode(void) const { return mEchoMode; }

    /**
     * This method sets whether or not ICMPv6 Echo processing is enabled.
     *
     * @param[in]  aEnabled  TRUE to enable ICMPv6 Echo processing, FALSE otherwise.
     *
     */
    void SetEchoMode(otIcmp6EchoMode aMode) { mEchoMode = aMode; }

    /**
     * This method indicates whether or not the ICMPv6 Echo Request should be handled.
     *
     * @retval TRUE if OpenThread should respond with an ICMPv6 Echo Reply.
     * @retval FALSE if OpenThread should not respond with an ICMPv6 Echo Reply.
     *
     */
    bool ShouldHandleEchoRequest(const MessageInfo &aMessageInfo);

private:
    otError HandleEchoRequest(Message &aRequestMessage, const MessageInfo &aMessageInfo);

    LinkedList<IcmpHandler> mHandlers;

    uint16_t        mEchoSequence;
    otIcmp6EchoMode mEchoMode;
};

/**
 * @}
 *
 */

} // namespace Ip6
} // namespace ot

#endif // ICMP6_HPP_