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 *     notice, this list of conditions and the following disclaimer in the
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 *     names of its contributors may be used to endorse or promote products
 *     derived from this software without specific prior written permission.
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/**
 * @file
 *   This file includes implementations for IPv6 Neighbor Discovery (ND6).
 *
 */

#include "nd6.hpp"

#include "common/as_core_type.hpp"
#include "common/code_utils.hpp"

namespace ot {
namespace Ip6 {
namespace Nd {

//----------------------------------------------------------------------------------------------------------------------
// Option::Iterator

Option::Iterator::Iterator(void)
    : mOption(nullptr)
    , mEnd(nullptr)
{
    // An empty iterator (used to indicate `end()` of list).
}

Option::Iterator::Iterator(const void *aStart, const void *aEnd)
    : mOption(nullptr)
    , mEnd(reinterpret_cast<const Option *>(aEnd))
{
    // Note that `Validate()` uses `mEnd` so can only be called after
    // `mEnd` is set.

    mOption = Validate(reinterpret_cast<const Option *>(aStart));
}

const Option *Option::Iterator::Next(const Option *aOption)
{
    return reinterpret_cast<const Option *>(reinterpret_cast<const uint8_t *>(aOption) + aOption->GetSize());
}

void Option::Iterator::Advance(void)
{
    mOption = (mOption != nullptr) ? Validate(Next(mOption)) : nullptr;
}

const Option *Option::Iterator::Validate(const Option *aOption) const
{
    // Check if `aOption` is well-formed and fits in the range
    // up to `mEnd`. Returns `aOption` if it is valid, `nullptr`
    // otherwise.

    return ((aOption != nullptr) && ((aOption + 1) <= mEnd) && aOption->IsValid() && (Next(aOption) <= mEnd)) ? aOption
                                                                                                              : nullptr;
}

//----------------------------------------------------------------------------------------------------------------------
// PrefixInfoOption

void PrefixInfoOption::Init(void)
{
    Clear();
    SetType(kTypePrefixInfo);
    SetSize(sizeof(PrefixInfoOption));

    OT_UNUSED_VARIABLE(mReserved2);
}

void PrefixInfoOption::SetPrefix(const Prefix &aPrefix)
{
    mPrefixLength = aPrefix.mLength;
    mPrefix       = AsCoreType(&aPrefix.mPrefix);
}

void PrefixInfoOption::GetPrefix(Prefix &aPrefix) const
{
    aPrefix.Set(mPrefix.GetBytes(), mPrefixLength);
}

bool PrefixInfoOption::IsValid(void) const
{
    return (GetSize() >= sizeof(*this)) && (mPrefixLength <= Prefix::kMaxLength) &&
           (GetPreferredLifetime() <= GetValidLifetime());
}

//----------------------------------------------------------------------------------------------------------------------
// RouteInfoOption

void RouteInfoOption::Init(void)
{
    Clear();
    SetType(kTypeRouteInfo);
}

void RouteInfoOption::SetPreference(RoutePreference aPreference)
{
    mResvdPrf &= ~kPreferenceMask;
    mResvdPrf |= (NetworkData::RoutePreferenceToValue(aPreference) << kPreferenceOffset) & kPreferenceMask;
}

RoutePreference RouteInfoOption::GetPreference(void) const
{
    return NetworkData::RoutePreferenceFromValue((mResvdPrf & kPreferenceMask) >> kPreferenceOffset);
}

void RouteInfoOption::SetPrefix(const Prefix &aPrefix)
{
    SetLength(OptionLengthForPrefix(aPrefix.mLength));
    mPrefixLength = aPrefix.mLength;
    memcpy(GetPrefixBytes(), aPrefix.GetBytes(), aPrefix.GetBytesSize());
}

void RouteInfoOption::GetPrefix(Prefix &aPrefix) const
{
    aPrefix.Set(GetPrefixBytes(), mPrefixLength);
}

bool RouteInfoOption::IsValid(void) const
{
    return (GetSize() >= kMinSize) && (mPrefixLength <= Prefix::kMaxLength) &&
           (GetLength() >= OptionLengthForPrefix(mPrefixLength)) &&
           NetworkData::IsRoutePreferenceValid(GetPreference());
}

uint8_t RouteInfoOption::OptionLengthForPrefix(uint8_t aPrefixLength)
{
    static constexpr uint8_t kMaxPrefixLenForOptionLen1 = 0;
    static constexpr uint8_t kMaxPrefixLenForOptionLen2 = 64;

    uint8_t length;

    // The Option Length can be 1, 2, or 3 depending on the prefix
    // length
    //
    // - 1 when prefix len is zero.
    // - 2 when prefix len is less then or equal to 64.
    // - 3 otherwise.

    if (aPrefixLength == kMaxPrefixLenForOptionLen1)
    {
        length = 1;
    }
    else if (aPrefixLength <= kMaxPrefixLenForOptionLen2)
    {
        length = 2;
    }
    else
    {
        length = 3;
    }

    return length;
}

//----------------------------------------------------------------------------------------------------------------------
// RouterAdverMessage::Header

void RouterAdvertMessage::Header::SetToDefault(void)
{
    OT_UNUSED_VARIABLE(mCode);
    OT_UNUSED_VARIABLE(mCurHopLimit);
    OT_UNUSED_VARIABLE(mReachableTime);
    OT_UNUSED_VARIABLE(mRetransTimer);

    Clear();
    mType = Icmp::Header::kTypeRouterAdvert;
}

RoutePreference RouterAdvertMessage::Header::GetDefaultRouterPreference(void) const
{
    return NetworkData::RoutePreferenceFromValue((mFlags & kPreferenceMask) >> kPreferenceOffset);
}

void RouterAdvertMessage::Header::SetDefaultRouterPreference(RoutePreference aPreference)
{
    mFlags &= ~kPreferenceMask;
    mFlags |= (NetworkData::RoutePreferenceToValue(aPreference) << kPreferenceOffset) & kPreferenceMask;
}

//----------------------------------------------------------------------------------------------------------------------
// RouterAdverMessage

Option *RouterAdvertMessage::AppendOption(uint16_t aOptionSize)
{
    // This method appends an option with a given size to the RA
    // message by reserving space in the data buffer if there is
    // room. On success returns pointer to the option, on failure
    // returns `nullptr`. The returned option needs to be
    // initialized and populated by the caller.

    Option * option    = nullptr;
    uint32_t newLength = mData.GetLength();

    newLength += aOptionSize;
    VerifyOrExit(newLength <= mMaxLength);

    option = reinterpret_cast<Option *>(AsNonConst(GetDataEnd()));
    mData.SetLength(static_cast<uint16_t>(newLength));

exit:
    return option;
}

Error RouterAdvertMessage::AppendPrefixInfoOption(const Prefix &aPrefix,
                                                  uint32_t      aValidLifetime,
                                                  uint32_t      aPreferredLifetime)
{
    Error             error = kErrorNone;
    PrefixInfoOption *pio;

    pio = static_cast<PrefixInfoOption *>(AppendOption(sizeof(PrefixInfoOption)));
    VerifyOrExit(pio != nullptr, error = kErrorNoBufs);

    pio->Init();
    pio->SetOnLinkFlag();
    pio->SetAutoAddrConfigFlag();
    pio->SetValidLifetime(aValidLifetime);
    pio->SetPreferredLifetime(aPreferredLifetime);
    pio->SetPrefix(aPrefix);

exit:
    return error;
}

Error RouterAdvertMessage::AppendRouteInfoOption(const Prefix &  aPrefix,
                                                 uint32_t        aRouteLifetime,
                                                 RoutePreference aPreference)
{
    Error            error = kErrorNone;
    RouteInfoOption *rio;

    rio = static_cast<RouteInfoOption *>(AppendOption(RouteInfoOption::OptionSizeForPrefix(aPrefix.GetLength())));
    VerifyOrExit(rio != nullptr, error = kErrorNoBufs);

    rio->Init();
    rio->SetRouteLifetime(aRouteLifetime);
    rio->SetPreference(aPreference);
    rio->SetPrefix(aPrefix);

exit:
    return error;
}

//----------------------------------------------------------------------------------------------------------------------
// RouterAdvMessage

RouterSolicitMessage::RouterSolicitMessage(void)
{
    mHeader.Clear();
    mHeader.SetType(Icmp::Header::kTypeRouterSolicit);
}

} // namespace Nd
} // namespace Ip6
} // namespace ot