multi-link-element.cc

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/*
 * Copyright (c) 2021 Universita' degli Studi di Napoli Federico II
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Author: Stefano Avallone <stavallo@unina.it>
 */
 
#include "multi-link-element.h"
 
#include "ns3/address-utils.h"
#include "ns3/log.h"
#include "ns3/mgt-headers.h"
 
#include <utility>
 
NS_LOG_COMPONENT_DEFINE("MultiLinkElement");
 
namespace ns3
{
 
MultiLinkElement::MultiLinkElement(ContainingFrame frame)
    : m_containingFrame(frame),
      m_commonInfo(std::in_place_type<std::monostate>) // initialize as UNSET
{
}
 
MultiLinkElement::MultiLinkElement(Variant variant, ContainingFrame frame)
    : MultiLinkElement(frame)
{
    NS_ASSERT(variant != UNSET);
    SetVariant(variant);
}
 
WifiInformationElementId
MultiLinkElement::ElementId() const
{
    return IE_EXTENSION;
}
 
WifiInformationElementId
MultiLinkElement::ElementIdExt() const
{
    return IE_EXT_MULTI_LINK_ELEMENT;
}
 
MultiLinkElement::Variant
MultiLinkElement::GetVariant() const
{
    return static_cast<Variant>(m_commonInfo.index());
}
 
void
MultiLinkElement::SetVariant(Variant variant)
{
    NS_ABORT_MSG_IF(GetVariant() != UNSET, "Multi-Link Element variant already set");
    NS_ABORT_MSG_IF(variant == UNSET, "Invalid variant");
 
    switch (variant)
    {
    case BASIC_VARIANT:
        m_commonInfo = CommonInfoBasicMle();
        break;
    case PROBE_REQUEST_VARIANT:
        m_commonInfo = CommonInfoProbeReqMle();
        break;
    default:
        NS_ABORT_MSG("Unsupported variant: " << +variant);
    }
}
 
CommonInfoBasicMle&
MultiLinkElement::GetCommonInfoBasic()
{
    return std::get<BASIC_VARIANT>(m_commonInfo);
}
 
const CommonInfoBasicMle&
MultiLinkElement::GetCommonInfoBasic() const
{
    return std::get<BASIC_VARIANT>(m_commonInfo);
}
 
void
MultiLinkElement::SetMldMacAddress(Mac48Address address)
{
    std::get<BASIC_VARIANT>(m_commonInfo).m_mldMacAddress = address;
}
 
Mac48Address
MultiLinkElement::GetMldMacAddress() const
{
    return std::get<BASIC_VARIANT>(m_commonInfo).m_mldMacAddress;
}
 
void
MultiLinkElement::SetLinkIdInfo(uint8_t linkIdInfo)
{
    std::get<BASIC_VARIANT>(m_commonInfo).m_linkIdInfo = (linkIdInfo & 0x0f);
}
 
bool
MultiLinkElement::HasLinkIdInfo() const
{
    return std::get<BASIC_VARIANT>(m_commonInfo).m_linkIdInfo.has_value();
}
 
uint8_t
MultiLinkElement::GetLinkIdInfo() const
{
    return std::get<BASIC_VARIANT>(m_commonInfo).m_linkIdInfo.value();
}
 
void
MultiLinkElement::SetBssParamsChangeCount(uint8_t count)
{
    std::get<BASIC_VARIANT>(m_commonInfo).m_bssParamsChangeCount = count;
}
 
bool
MultiLinkElement::HasBssParamsChangeCount() const
{
    return std::get<BASIC_VARIANT>(m_commonInfo).m_bssParamsChangeCount.has_value();
}
 
uint8_t
MultiLinkElement::GetBssParamsChangeCount() const
{
    return std::get<BASIC_VARIANT>(m_commonInfo).m_bssParamsChangeCount.value();
}
 
void
MultiLinkElement::SetEmlsrSupported(bool supported)
{
    auto& emlCapabilities = std::get<BASIC_VARIANT>(m_commonInfo).m_emlCapabilities;
    if (!emlCapabilities.has_value())
    {
        emlCapabilities = CommonInfoBasicMle::EmlCapabilities{};
    }
    emlCapabilities->emlsrSupport = supported ? 1 : 0;
}
 
void
MultiLinkElement::SetEmlsrPaddingDelay(Time delay)
{
    auto& emlCapabilities = std::get<BASIC_VARIANT>(m_commonInfo).m_emlCapabilities;
    if (!emlCapabilities.has_value())
    {
        emlCapabilities = CommonInfoBasicMle::EmlCapabilities{};
    }
    emlCapabilities->emlsrPaddingDelay = CommonInfoBasicMle::EncodeEmlsrPaddingDelay(delay);
}
 
void
MultiLinkElement::SetEmlsrTransitionDelay(Time delay)
{
    auto& emlCapabilities = std::get<BASIC_VARIANT>(m_commonInfo).m_emlCapabilities;
    if (!emlCapabilities.has_value())
    {
        emlCapabilities = CommonInfoBasicMle::EmlCapabilities{};
    }
    emlCapabilities->emlsrTransitionDelay = CommonInfoBasicMle::EncodeEmlsrTransitionDelay(delay);
}
 
void
MultiLinkElement::SetTransitionTimeout(Time timeout)
{
    auto& emlCapabilities = std::get<BASIC_VARIANT>(m_commonInfo).m_emlCapabilities;
    if (!emlCapabilities.has_value())
    {
        emlCapabilities = CommonInfoBasicMle::EmlCapabilities{};
    }
    auto timeoutUs = timeout.GetMicroSeconds();
 
    if (timeoutUs == 0)
    {
        emlCapabilities->transitionTimeout = 0;
    }
    else
    {
        uint8_t i;
        for (i = 1; i <= 10; i++)
        {
            if (1 << (i + 6) == timeoutUs)
            {
                emlCapabilities->transitionTimeout = i;
                break;
            }
        }
        NS_ABORT_MSG_IF(i > 10, "Value not allowed (" << timeout.As(Time::US) << ")");
    }
}
 
bool
MultiLinkElement::HasEmlCapabilities() const
{
    return std::get<BASIC_VARIANT>(m_commonInfo).m_emlCapabilities.has_value();
}
 
bool
MultiLinkElement::IsEmlsrSupported() const
{
    return std::get<BASIC_VARIANT>(m_commonInfo).m_emlCapabilities->emlsrSupport;
}
 
Time
MultiLinkElement::GetEmlsrPaddingDelay() const
{
    auto& emlCapabilities = std::get<BASIC_VARIANT>(m_commonInfo).m_emlCapabilities;
    NS_ASSERT(emlCapabilities);
    return CommonInfoBasicMle::DecodeEmlsrPaddingDelay(emlCapabilities->emlsrPaddingDelay);
}
 
Time
MultiLinkElement::GetEmlsrTransitionDelay() const
{
    auto& emlCapabilities = std::get<BASIC_VARIANT>(m_commonInfo).m_emlCapabilities;
    NS_ASSERT(emlCapabilities);
    return CommonInfoBasicMle::DecodeEmlsrTransitionDelay(emlCapabilities->emlsrTransitionDelay);
}
 
Time
MultiLinkElement::GetTransitionTimeout() const
{
    auto& emlCapabilities = std::get<BASIC_VARIANT>(m_commonInfo).m_emlCapabilities;
    NS_ASSERT(emlCapabilities);
    if (emlCapabilities->transitionTimeout == 0)
    {
        return MicroSeconds(0);
    }
    return MicroSeconds(1 << (6 + emlCapabilities->transitionTimeout));
}
 
void
MultiLinkElement::SetApMldId(uint8_t id)
{
    const auto variant = GetVariant();
    switch (variant)
    {
    case BASIC_VARIANT:
        std::get<CommonInfoBasicMle>(m_commonInfo).m_apMldId = id;
        return;
    case PROBE_REQUEST_VARIANT:
        std::get<CommonInfoProbeReqMle>(m_commonInfo).m_apMldId = id;
        return;
    default:
        NS_ABORT_MSG("AP MLD ID field not present in input variant " << variant);
    }
}
 
std::optional<uint8_t>
MultiLinkElement::GetApMldId() const
{
    const auto variant = GetVariant();
    switch (variant)
    {
    case BASIC_VARIANT:
        return std::get<CommonInfoBasicMle>(m_commonInfo).m_apMldId;
    case PROBE_REQUEST_VARIANT:
        return std::get<CommonInfoProbeReqMle>(m_commonInfo).m_apMldId;
    default:
        NS_LOG_DEBUG("AP MLD ID field not present in input variant");
    }
    return std::nullopt;
}
 
MultiLinkElement::PerStaProfileSubelement::PerStaProfileSubelement(Variant variant)
    : m_variant(variant),
      m_staControl(0)
{
}
 
MultiLinkElement::PerStaProfileSubelement::PerStaProfileSubelement(
    const PerStaProfileSubelement& perStaProfile)
    : m_variant(perStaProfile.m_variant),
      m_staControl(perStaProfile.m_staControl),
      m_staMacAddress(perStaProfile.m_staMacAddress),
      m_bssParamsChgCnt(perStaProfile.m_bssParamsChgCnt)
{
    // deep copy of the STA Profile field
    auto staProfileCopy = [&](auto&& frame) {
        using Ptr = std::decay_t<decltype(frame)>;
        if constexpr (std::is_same_v<Ptr, std::monostate>)
        {
            return;
        }
        else
        {
            using T = std::decay_t<decltype(*frame.get())>;
            m_staProfile = std::make_unique<T>(*frame.get());
        }
    };
    std::visit(staProfileCopy, perStaProfile.m_staProfile);
}
 
MultiLinkElement::PerStaProfileSubelement&
MultiLinkElement::PerStaProfileSubelement::operator=(const PerStaProfileSubelement& perStaProfile)
{
    // check for self-assignment
    if (&perStaProfile == this)
    {
        return *this;
    }
 
    m_variant = perStaProfile.m_variant;
    m_staControl = perStaProfile.m_staControl;
    m_staMacAddress = perStaProfile.m_staMacAddress;
    m_bssParamsChgCnt = perStaProfile.m_bssParamsChgCnt;
 
    // deep copy of the STA Profile field
    auto staProfileCopy = [&](auto&& frame) {
        using Ptr = std::decay_t<decltype(frame)>;
        if constexpr (std::is_same_v<Ptr, std::monostate>)
        {
            return;
        }
        else
        {
            using T = std::decay_t<decltype(*frame.get())>;
            m_staProfile = std::make_unique<T>(*frame.get());
        }
    };
    std::visit(staProfileCopy, perStaProfile.m_staProfile);
 
    return *this;
}
 
void
MultiLinkElement::PerStaProfileSubelement::SetLinkId(uint8_t linkId)
{
    m_staControl &= 0xfff0; // reset Link ID subfield in the STA Control field
    m_staControl |= (linkId & 0x0f);
}
 
uint8_t
MultiLinkElement::PerStaProfileSubelement::GetLinkId() const
{
    return static_cast<uint8_t>(m_staControl & 0x000f);
}
 
void
MultiLinkElement::PerStaProfileSubelement::SetCompleteProfile()
{
    m_staControl |= 0x0010;
}
 
bool
MultiLinkElement::PerStaProfileSubelement::IsCompleteProfileSet() const
{
    return (m_staControl & 0x0010) != 0;
}
 
void
MultiLinkElement::PerStaProfileSubelement::SetStaMacAddress(Mac48Address address)
{
    NS_ABORT_IF(m_variant != BASIC_VARIANT);
    m_staMacAddress = address;
    m_staControl |= 0x0020;
}
 
bool
MultiLinkElement::PerStaProfileSubelement::HasStaMacAddress() const
{
    return (m_staControl & 0x0020) != 0;
}
 
Mac48Address
MultiLinkElement::PerStaProfileSubelement::GetStaMacAddress() const
{
    NS_ABORT_IF(!HasStaMacAddress());
    return m_staMacAddress;
}
 
void
MultiLinkElement::PerStaProfileSubelement::SetBssParamsChgCnt(uint8_t count)
{
    NS_ABORT_MSG_IF(m_variant != BASIC_VARIANT,
                    "Expected Basic Variant, variant:" << +static_cast<uint8_t>(m_variant));
    m_bssParamsChgCnt = count;
    m_staControl |= 0x0800;
}
 
bool
MultiLinkElement::PerStaProfileSubelement::HasBssParamsChgCnt() const
{
    return (m_staControl & 0x0800) != 0;
}
 
uint8_t
MultiLinkElement::PerStaProfileSubelement::GetBssParamsChgCnt() const
{
    NS_ASSERT_MSG(m_bssParamsChgCnt.has_value(), "No value set for m_bssParamsChgCnt");
    NS_ASSERT_MSG(HasBssParamsChgCnt(), "BSS Parameters Change count bit not set");
    return m_bssParamsChgCnt.value();
}
 
void
MultiLinkElement::PerStaProfileSubelement::SetAssocRequest(
    const std::variant<MgtAssocRequestHeader, MgtReassocRequestHeader>& assoc)
{
    std::visit(
        [&](auto&& frame) {
            m_staProfile = std::make_unique<std::decay_t<decltype(frame)>>(frame);
        },
        assoc);
}
 
void
MultiLinkElement::PerStaProfileSubelement::SetAssocRequest(
    std::variant<MgtAssocRequestHeader, MgtReassocRequestHeader>&& assoc)
{
    std::visit(
        [&](auto&& frame) {
            using T = std::decay_t<decltype(frame)>;
            m_staProfile = std::make_unique<T>(std::forward<T>(frame));
        },
        assoc);
}
 
bool
MultiLinkElement::PerStaProfileSubelement::HasAssocRequest() const
{
    return std::holds_alternative<std::unique_ptr<MgtAssocRequestHeader>>(m_staProfile);
}
 
bool
MultiLinkElement::PerStaProfileSubelement::HasReassocRequest() const
{
    return std::holds_alternative<std::unique_ptr<MgtReassocRequestHeader>>(m_staProfile);
}
 
AssocReqRefVariant
MultiLinkElement::PerStaProfileSubelement::GetAssocRequest() const
{
    if (HasAssocRequest())
    {
        return *std::get<std::unique_ptr<MgtAssocRequestHeader>>(m_staProfile);
    }
    NS_ABORT_UNLESS(HasReassocRequest());
    return *std::get<std::unique_ptr<MgtReassocRequestHeader>>(m_staProfile);
}
 
void
MultiLinkElement::PerStaProfileSubelement::SetAssocResponse(const MgtAssocResponseHeader& assoc)
{
    m_staProfile = std::make_unique<MgtAssocResponseHeader>(assoc);
}
 
void
MultiLinkElement::PerStaProfileSubelement::SetAssocResponse(MgtAssocResponseHeader&& assoc)
{
    m_staProfile = std::make_unique<MgtAssocResponseHeader>(std::move(assoc));
}
 
bool
MultiLinkElement::PerStaProfileSubelement::HasAssocResponse() const
{
    return std::holds_alternative<std::unique_ptr<MgtAssocResponseHeader>>(m_staProfile);
}
 
MgtAssocResponseHeader&
MultiLinkElement::PerStaProfileSubelement::GetAssocResponse() const
{
    NS_ABORT_IF(!HasAssocResponse());
    return *std::get<std::unique_ptr<MgtAssocResponseHeader>>(m_staProfile);
}
 
void
MultiLinkElement::PerStaProfileSubelement::SetProbeResponse(const MgtProbeResponseHeader& probeResp)
{
    m_staProfile = std::make_unique<MgtProbeResponseHeader>(probeResp);
}
 
void
MultiLinkElement::PerStaProfileSubelement::SetProbeResponse(MgtProbeResponseHeader&& probeResp)
{
    m_staProfile = std::make_unique<MgtProbeResponseHeader>(std::move(probeResp));
}
 
bool
MultiLinkElement::PerStaProfileSubelement::HasProbeResponse() const
{
    return std::holds_alternative<std::unique_ptr<MgtProbeResponseHeader>>(m_staProfile);
}
 
MgtProbeResponseHeader&
MultiLinkElement::PerStaProfileSubelement::GetProbeResponse() const
{
    NS_ABORT_IF(!HasProbeResponse());
    return *std::get<std::unique_ptr<MgtProbeResponseHeader>>(m_staProfile);
}
 
uint8_t
MultiLinkElement::PerStaProfileSubelement::GetStaInfoLength() const
{
    if (m_variant == PROBE_REQUEST_VARIANT)
    {
        return 0; // IEEE 802.11be 6.0 Figure 9-1072s
    }
 
    uint8_t ret = 1; // STA Info Length
 
    if (HasStaMacAddress())
    {
        ret += 6;
    }
    if (HasBssParamsChgCnt())
    {
        ret += 1;
    }
    // TODO add other subfields of the STA Info field
    return ret;
}
 
WifiInformationElementId
MultiLinkElement::PerStaProfileSubelement::ElementId() const
{
    return PER_STA_PROFILE_SUBELEMENT_ID;
}
 
uint16_t
MultiLinkElement::PerStaProfileSubelement::GetInformationFieldSize() const
{
    uint16_t ret = 2; // STA Control field
 
    ret += GetStaInfoLength();
 
    auto staProfileSize = [&](auto&& frame) {
        using T = std::decay_t<decltype(frame)>;
        if constexpr (std::is_same_v<T, std::monostate>)
        {
            NS_ASSERT_MSG(std::holds_alternative<std::monostate>(m_containingFrame),
                          "Missing management frame for Per-STA Profile subelement");
            return static_cast<uint32_t>(0);
        }
        else
        {
            using U = std::decay_t<decltype(*frame)>;
            NS_ASSERT_MSG(
                std::holds_alternative<std::reference_wrapper<const U>>(m_containingFrame),
                "Containing frame type and frame type in Per-STA Profile do not match");
            const auto& containing = std::get<std::reference_wrapper<const U>>(m_containingFrame);
            return frame->GetSerializedSizeInPerStaProfile(containing);
        }
    };
    ret += std::visit(staProfileSize, m_staProfile);
 
    return ret;
}
 
void
MultiLinkElement::PerStaProfileSubelement::SerializeInformationField(Buffer::Iterator start) const
{
    if (m_variant == PROBE_REQUEST_VARIANT)
    {
        NS_ASSERT_MSG(IsCompleteProfileSet(), "Encoding of STA Profile not supported");
        start.WriteHtolsbU16(m_staControl);
        return;
    }
 
    start.WriteHtolsbU16(m_staControl);
    start.WriteU8(GetStaInfoLength());
 
    if (HasStaMacAddress())
    {
        WriteTo(start, m_staMacAddress);
    }
    if (HasBssParamsChgCnt())
    {
        start.WriteU8(GetBssParamsChgCnt());
    }
    // TODO add other subfields of the STA Info field
    auto staProfileSerialize = [&](auto&& frame) {
        using T = std::decay_t<decltype(frame)>;
        if constexpr (std::is_same_v<T, std::monostate>)
        {
            NS_ASSERT_MSG(std::holds_alternative<std::monostate>(m_containingFrame),
                          "Missing management frame for Per-STA Profile subelement");
            return;
        }
        else
        {
            using U = std::decay_t<decltype(*frame)>;
            NS_ASSERT_MSG(
                std::holds_alternative<std::reference_wrapper<const U>>(m_containingFrame),
                "Containing frame type and frame type in Per-STA Profile do not match");
            const auto& containing = std::get<std::reference_wrapper<const U>>(m_containingFrame);
            frame->SerializeInPerStaProfile(start, containing);
        }
    };
    std::visit(staProfileSerialize, m_staProfile);
}
 
uint16_t
MultiLinkElement::PerStaProfileSubelement::DeserializeInformationField(Buffer::Iterator start,
                                                                       uint16_t length)
{
    if (m_variant == PROBE_REQUEST_VARIANT)
    {
        return DeserProbeReqMlePerSta(start, length);
    }
 
    Buffer::Iterator i = start;
 
    m_staControl = i.ReadLsbtohU16();
    i.ReadU8(); // STA Info Length
 
    if (HasStaMacAddress())
    {
        ReadFrom(i, m_staMacAddress);
    }
    if (HasBssParamsChgCnt())
    {
        m_bssParamsChgCnt = i.ReadU8();
    }
 
    // TODO add other subfields of the STA Info field
    uint16_t count = i.GetDistanceFrom(start);
 
    NS_ASSERT_MSG(count <= length,
                  "Bytes read (" << count << ") exceed expected number (" << length << ")");
 
    if (count == length)
    {
        return count;
    }
 
    auto staProfileDeserialize = [&](auto&& frame) {
        using T = std::decay_t<decltype(frame)>;
        if constexpr (!std::is_same_v<T, std::monostate>)
        {
            using U = std::decay_t<decltype(frame.get())>;
            U assoc;
            count += assoc.DeserializeFromPerStaProfile(i, length - count, frame.get());
            m_staProfile = std::make_unique<U>(std::move(assoc));
        }
    };
    std::visit(staProfileDeserialize, m_containingFrame);
 
    return count;
}
 
uint16_t
MultiLinkElement::PerStaProfileSubelement::DeserProbeReqMlePerSta(ns3::Buffer::Iterator start,
                                                                  uint16_t length)
{
    NS_ASSERT_MSG(m_variant == PROBE_REQUEST_VARIANT,
                  "Invalid Multi-link Element variant = " << static_cast<uint8_t>(m_variant));
    Buffer::Iterator i = start;
    uint16_t count = 0;
 
    m_staControl = i.ReadLsbtohU16();
    count += 2;
 
    NS_ASSERT_MSG(count <= length,
                  "Incorrect decoded size count =" << count << ", length=" << length);
    if (count == length)
    {
        return count;
    }
 
    // TODO: Support decoding of Partial Per-STA Profile
    // IEEE 802.11be D5.0 9.4.2.312.3 Probe Request Multi-Link element
    // If the Complete Profile Requested subfield is set to 0 and the STA Profile field
    // is present in a Per-STA Profile subelement,
    // the STA Profile field includes exactly one of the following:
    // - one Request element (see 9.4.2.9 (Request element)), or
    // — one Extended Request element (see 9.4.2.10 (Extended Request element)), or
    // — one Request element and one Extended Request element
    NS_LOG_DEBUG("Decoding of STA Profile in Per-STA Profile subelement not supported");
    while (count < length)
    {
        i.ReadU8();
        count++;
    }
    return count;
}
 
void
MultiLinkElement::PerStaProfileSubelement::Print(std::ostream& os) const
{
    os << "Per-STA Profile Subelement=[";
    os << "Variant: " << +static_cast<uint8_t>(m_variant);
    os << ", STA Control: " << +m_staControl;
    if (HasStaMacAddress())
    {
        os << ", STA MAC Address: " << m_staMacAddress;
    }
    if (m_bssParamsChgCnt)
    {
        os << ", BSS Params Change Count: " << +m_bssParamsChgCnt.value();
    }
    os << "]";
}
 
void
MultiLinkElement::AddPerStaProfileSubelement()
{
    auto variant = GetVariant();
    NS_ABORT_IF(variant == UNSET);
    m_perStaProfileSubelements.emplace_back(variant);
}
 
std::size_t
MultiLinkElement::GetNPerStaProfileSubelements() const
{
    return m_perStaProfileSubelements.size();
}
 
MultiLinkElement::PerStaProfileSubelement&
MultiLinkElement::GetPerStaProfile(std::size_t i)
{
    return m_perStaProfileSubelements.at(i);
}
 
const MultiLinkElement::PerStaProfileSubelement&
MultiLinkElement::GetPerStaProfile(std::size_t i) const
{
    return m_perStaProfileSubelements.at(i);
}
 
uint16_t
MultiLinkElement::GetInformationFieldSize() const
{
    uint16_t ret = 3; // ElementIdExt (1) + Multi-Link Control (2)
 
    // add the Common Info field size (dependent on the Multi-Link Element variant)
    ret += std::visit(
        [](auto&& arg) -> uint8_t {
            using T = std::decay_t<decltype(arg)>;
            if constexpr (std::is_same_v<T, std::monostate>)
            {
                NS_ABORT_MSG("Multi-Link Element variant not set");
                return 0;
            }
            else
            {
                return arg.GetSize();
            }
        },
        m_commonInfo);
 
    for (const auto& subelement : m_perStaProfileSubelements)
    {
        subelement.m_containingFrame = m_containingFrame;
        ret += subelement.GetSerializedSize();
    }
 
    return ret;
}
 
void
MultiLinkElement::SerializeInformationField(Buffer::Iterator start) const
{
    // serialize the Multi-Link Control and Common Info fields
    std::visit(
        [this, &start](auto&& arg) {
            using T = std::decay_t<decltype(arg)>;
            if constexpr (std::is_same_v<T, std::monostate>)
            {
                NS_ABORT_MSG("Multi-Link Element variant not set");
            }
            else
            {
                uint16_t mlControl =
                    static_cast<uint8_t>(GetVariant()) + (arg.GetPresenceBitmap() << 4);
                start.WriteHtolsbU16(mlControl);
                arg.Serialize(start);
            }
        },
        m_commonInfo);
 
    for (const auto& subelement : m_perStaProfileSubelements)
    {
        start = subelement.Serialize(start);
    }
}
 
uint16_t
MultiLinkElement::DeserializeInformationField(Buffer::Iterator start, uint16_t length)
{
    Buffer::Iterator i = start;
    uint16_t count = 0;
 
    uint16_t mlControl = i.ReadLsbtohU16();
    count += 2;
 
    SetVariant(static_cast<Variant>(mlControl & 0x0007));
    uint16_t presence = mlControl >> 4;
 
    uint8_t nBytes = std::visit(
        [&i, &presence](auto&& arg) -> uint8_t {
            using T = std::decay_t<decltype(arg)>;
            if constexpr (std::is_same_v<T, std::monostate>)
            {
                NS_ABORT_MSG("Multi-Link Element variant not set");
                return 0;
            }
            else
            {
                return arg.Deserialize(i, presence);
            }
        },
        m_commonInfo);
    i.Next(nBytes);
    count += nBytes;
 
    while (count < length)
    {
        switch (static_cast<SubElementId>(i.PeekU8()))
        {
        case PER_STA_PROFILE_SUBELEMENT_ID: {
            AddPerStaProfileSubelement();
            auto& perStaProfile = GetPerStaProfile(GetNPerStaProfileSubelements() - 1);
            perStaProfile.m_containingFrame = m_containingFrame;
            i = perStaProfile.Deserialize(i);
            count = i.GetDistanceFrom(start);
        }
        break;
        default:
            NS_ABORT_MSG("Unsupported Subelement ID: " << +i.PeekU8());
        }
    }
 
    return count;
}
 
void
MultiLinkElement::Print(std::ostream& os) const
{
    os << "Multi-Link Element=[Per-STA Profile Subelements: {";
    for (const auto& subelement : m_perStaProfileSubelements)
    {
        subelement.Print(os);
    }
    os << "}]";
}
 
} // namespace ns3