5 files changed, 602 insertions, 33 deletions

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index e404063f0..b894564b6 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -139,6 +139,7 @@ set(SRCS
             hle/service/nwm/nwm_soc.cpp
             hle/service/nwm/nwm_tst.cpp
             hle/service/nwm/nwm_uds.cpp
+            hle/service/nwm/uds_beacon.cpp
             hle/service/pm_app.cpp
             hle/service/ptm/ptm.cpp
             hle/service/ptm/ptm_gets.cpp
@@ -326,6 +327,7 @@ set(HEADERS
             hle/service/nwm/nwm_soc.h
             hle/service/nwm/nwm_tst.h
             hle/service/nwm/nwm_uds.h
+            hle/service/nwm/uds_beacon.h
             hle/service/pm_app.h
             hle/service/ptm/ptm.h
             hle/service/ptm/ptm_gets.h
diff --git a/src/core/hle/service/nwm/nwm_uds.cpp b/src/core/hle/service/nwm/nwm_uds.cpp
index ef6c5ebe3..581816e81 100644
--- a/src/core/hle/service/nwm/nwm_uds.cpp
+++ b/src/core/hle/service/nwm/nwm_uds.cpp
@@ -2,6 +2,7 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
+#include <array>
 #include <cstring>
 #include <unordered_map>
 #include <vector>
@@ -12,6 +13,7 @@
 #include "core/hle/kernel/shared_memory.h"
 #include "core/hle/result.h"
 #include "core/hle/service/nwm/nwm_uds.h"
+#include "core/hle/service/nwm/uds_beacon.h"
 #include "core/memory.h"
 
 namespace Service {
@@ -27,10 +29,12 @@ static Kernel::SharedPtr<Kernel::SharedMemory> recv_buffer_memory;
 // Connection status of this 3DS.
 static ConnectionStatus connection_status{};
 
-// Node information about the current 3DS.
-// TODO(Subv): Keep an array of all nodes connected to the network,
-// that data has to be retransmitted in every beacon frame.
-static NodeInfo node_info;
+/* Node information about the current network.
+ * The amount of elements in this vector is always the maximum number
+ * of nodes specified in the network configuration.
+ * The first node is always the host, so this always contains at least 1 entry.
+ */
+static NodeList node_info(1);
 
 // Mapping of bind node ids to their respective events.
 static std::unordered_map<u32, Kernel::SharedPtr<Kernel::Event>> bind_node_events;
@@ -82,29 +86,70 @@ static void Shutdown(Interface* self) {
  *      1 : Result of function, 0 on success, otherwise error code
  */
 static void RecvBeaconBroadcastData(Interface* self) {
-    u32* cmd_buff = Kernel::GetCommandBuffer();
-    u32 out_buffer_size = cmd_buff[1];
-    u32 unk1 = cmd_buff[2];
-    u32 unk2 = cmd_buff[3];
-    u32 mac_address = cmd_buff[4];
+    IPC::RequestParser rp(Kernel::GetCommandBuffer(), 0x0F, 16, 4);
 
-    u32 unk3 = cmd_buff[6];
+    u32 out_buffer_size = rp.Pop<u32>();
+    u32 unk1 = rp.Pop<u32>();
+    u32 unk2 = rp.Pop<u32>();
 
-    u32 wlan_comm_id = cmd_buff[15];
-    u32 ctr_gen_id = cmd_buff[16];
-    u32 value = cmd_buff[17];
-    u32 input_handle = cmd_buff[18];
-    u32 new_buffer_size = cmd_buff[19];
-    u32 out_buffer_ptr = cmd_buff[20];
+    MacAddress mac_address;
+    rp.PopRaw(mac_address);
 
-    cmd_buff[1] = RESULT_SUCCESS.raw;
+    rp.Skip(9, false);
 
-    LOG_WARNING(Service_NWM,
-                "(STUBBED) called out_buffer_size=0x%08X, unk1=0x%08X, unk2=0x%08X,"
-                "mac_address=0x%08X, unk3=0x%08X, wlan_comm_id=0x%08X, ctr_gen_id=0x%08X,"
-                "value=%u, input_handle=0x%08X, new_buffer_size=0x%08X, out_buffer_ptr=0x%08X",
-                out_buffer_size, unk1, unk2, mac_address, unk3, wlan_comm_id, ctr_gen_id, value,
-                input_handle, new_buffer_size, out_buffer_ptr);
+    u32 wlan_comm_id = rp.Pop<u32>();
+    u32 id = rp.Pop<u32>();
+    Kernel::Handle input_handle = rp.PopHandle();
+
+    size_t desc_size;
+    const VAddr out_buffer_ptr = rp.PopMappedBuffer(&desc_size);
+    ASSERT(desc_size == out_buffer_size);
+
+    VAddr current_buffer_pos = out_buffer_ptr;
+    u32 total_size = sizeof(BeaconDataReplyHeader);
+
+    // Retrieve all beacon frames that were received from the desired mac address.
+    std::deque<WifiPacket> beacons =
+        GetReceivedPackets(WifiPacket::PacketType::Beacon, mac_address);
+
+    BeaconDataReplyHeader data_reply_header{};
+    data_reply_header.total_entries = beacons.size();
+    data_reply_header.max_output_size = out_buffer_size;
+
+    Memory::WriteBlock(current_buffer_pos, &data_reply_header, sizeof(BeaconDataReplyHeader));
+    current_buffer_pos += sizeof(BeaconDataReplyHeader);
+
+    // Write each of the received beacons into the buffer
+    for (const auto& beacon : beacons) {
+        BeaconEntryHeader entry{};
+        // TODO(Subv): Figure out what this size is used for.
+        entry.unk_size = sizeof(BeaconEntryHeader) + beacon.data.size();
+        entry.total_size = sizeof(BeaconEntryHeader) + beacon.data.size();
+        entry.wifi_channel = beacon.channel;
+        entry.header_size = sizeof(BeaconEntryHeader);
+        entry.mac_address = beacon.transmitter_address;
+
+        ASSERT(current_buffer_pos < out_buffer_ptr + out_buffer_size);
+
+        Memory::WriteBlock(current_buffer_pos, &entry, sizeof(BeaconEntryHeader));
+        current_buffer_pos += sizeof(BeaconEntryHeader);
+
+        Memory::WriteBlock(current_buffer_pos, beacon.data.data(), beacon.data.size());
+        current_buffer_pos += beacon.data.size();
+
+        total_size += sizeof(BeaconEntryHeader) + beacon.data.size();
+    }
+
+    // Update the total size in the structure and write it to the buffer again.
+    data_reply_header.total_size = total_size;
+    Memory::WriteBlock(out_buffer_ptr, &data_reply_header, sizeof(BeaconDataReplyHeader));
+
+    IPC::RequestBuilder rb = rp.MakeBuilder(1, 0);
+    rb.Push(RESULT_SUCCESS);
+
+    LOG_DEBUG(Service_NWM, "called out_buffer_size=0x%08X, wlan_comm_id=0x%08X, id=0x%08X,"
+                           "input_handle=0x%08X, out_buffer_ptr=0x%08X, unk1=0x%08X, unk2=0x%08X",
+              out_buffer_size, wlan_comm_id, id, input_handle, out_buffer_ptr, unk1, unk2);
 }
 
 /**
@@ -127,10 +172,10 @@ static void InitializeWithVersion(Interface* self) {
     u32 sharedmem_size = rp.Pop<u32>();
 
     // Update the node information with the data the game gave us.
-    rp.PopRaw(node_info);
+    rp.PopRaw(node_info[0]);
+
+    u16 version = rp.Pop<u16>();
 
-    u16 version;
-    rp.PopRaw(version);
     Kernel::Handle sharedmem_handle = rp.PopHandle();
 
     recv_buffer_memory = Kernel::g_handle_table.Get<Kernel::SharedMemory>(sharedmem_handle);
@@ -191,10 +236,8 @@ static void Bind(Interface* self) {
 
     u32 bind_node_id = rp.Pop<u32>();
     u32 recv_buffer_size = rp.Pop<u32>();
-    u8 data_channel;
-    rp.PopRaw(data_channel);
-    u16 network_node_id;
-    rp.PopRaw(network_node_id);
+    u8 data_channel = rp.Pop<u8>();
+    u16 network_node_id = rp.Pop<u16>();
 
     // TODO(Subv): Store the data channel and verify it when receiving data frames.
 
@@ -251,13 +294,25 @@ static void BeginHostingNetwork(Interface* self) {
     ASSERT_MSG(network_info.max_nodes > 1, "Trying to host a network of only one member.");
 
     connection_status.status = static_cast<u32>(NetworkStatus::ConnectedAsHost);
+
+    // Ensure the application data size is less than the maximum value.
+    ASSERT_MSG(network_info.application_data_size <= ApplicationDataSize, "Data size is too big.");
+
+    // Set up basic information for this network.
+    network_info.oui_value = NintendoOUI;
+    network_info.oui_type = static_cast<u8>(NintendoTagId::NetworkInfo);
+
     connection_status.max_nodes = network_info.max_nodes;
 
+    // Resize the nodes list to hold max_nodes.
+    node_info.resize(network_info.max_nodes);
+
     // There's currently only one node in the network (the host).
     connection_status.total_nodes = 1;
+    network_info.total_nodes = 1;
     // The host is always the first node
     connection_status.network_node_id = 1;
-    node_info.network_node_id = 1;
+    node_info[0].network_node_id = 1;
     // Set the bit 0 in the nodes bitmask to indicate that node 1 is already taken.
     connection_status.node_bitmask |= 1;
 
@@ -325,7 +380,7 @@ static void GetChannel(Interface* self) {
     u8 channel = is_connected ? network_channel : 0;
 
     rb.Push(RESULT_SUCCESS);
-    rb.PushRaw(channel);
+    rb.Push(channel);
 
     LOG_DEBUG(Service_NWM, "called");
 }
@@ -373,7 +428,8 @@ static void BeaconBroadcastCallback(u64 userdata, int cycles_late) {
     if (connection_status.status != static_cast<u32>(NetworkStatus::ConnectedAsHost))
         return;
 
-    // TODO(Subv): Actually generate the beacon and send it.
+    // TODO(Subv): Actually send the beacon.
+    std::vector<u8> frame = GenerateBeaconFrame(network_info, node_info);
 
     // Start broadcasting the network, send a beacon frame every 102.4ms.
     CoreTiming::ScheduleEvent(msToCycles(DefaultBeaconInterval * MillisecondsPerTU) - cycles_late,
diff --git a/src/core/hle/service/nwm/nwm_uds.h b/src/core/hle/service/nwm/nwm_uds.h
index 65349f9fd..29b146569 100644
--- a/src/core/hle/service/nwm/nwm_uds.h
+++ b/src/core/hle/service/nwm/nwm_uds.h
@@ -6,6 +6,7 @@
 
 #include <array>
 #include <cstddef>
+#include <vector>
 #include "common/common_types.h"
 #include "common/swap.h"
 #include "core/hle/service/service.h"
@@ -33,6 +34,8 @@ struct NodeInfo {
 
 static_assert(sizeof(NodeInfo) == 40, "NodeInfo has incorrect size.");
 
+using NodeList = std::vector<NodeInfo>;
+
 enum class NetworkStatus {
     NotConnected = 3,
     ConnectedAsHost = 6,
@@ -75,6 +78,8 @@ struct NetworkInfo {
     std::array<u8, ApplicationDataSize> application_data;
 };
 
+static_assert(offsetof(NetworkInfo, oui_value) == 0xC, "oui_value is at the wrong offset.");
+static_assert(offsetof(NetworkInfo, wlan_comm_id) == 0x10, "wlancommid is at the wrong offset.");
 static_assert(sizeof(NetworkInfo) == 0x108, "NetworkInfo has incorrect size.");
 
 class NWM_UDS final : public Interface {
diff --git a/src/core/hle/service/nwm/uds_beacon.cpp b/src/core/hle/service/nwm/uds_beacon.cpp
new file mode 100644
index 000000000..c6e5bc5f1
--- /dev/null
+++ b/src/core/hle/service/nwm/uds_beacon.cpp
@@ -0,0 +1,333 @@
+// Copyright 2017 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <cstring>
+
+#include "core/hle/service/nwm/nwm_uds.h"
+#include "core/hle/service/nwm/uds_beacon.h"
+
+#include <cryptopp/aes.h>
+#include <cryptopp/md5.h>
+#include <cryptopp/modes.h>
+#include <cryptopp/sha.h>
+
+namespace Service {
+namespace NWM {
+
+// 802.11 broadcast MAC address
+constexpr MacAddress BroadcastMac = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
+
+constexpr u64 DefaultNetworkUptime = 900000000; // 15 minutes in microseconds.
+
+// Note: These values were taken from a packet capture of an o3DS XL
+// broadcasting a Super Smash Bros. 4 lobby.
+constexpr u16 DefaultExtraCapabilities = 0x0431;
+
+// Size of the SSID broadcast by an UDS beacon frame.
+constexpr u8 UDSBeaconSSIDSize = 8;
+
+// The maximum size of the data stored in the EncryptedData0 tag (24).
+constexpr u32 EncryptedDataSizeCutoff = 0xFA;
+
+/**
+ * NWM Beacon data encryption key, taken from the NWM module code.
+ * We stub this with an all-zeros key as that is enough for Citra's purpose.
+ * The real key can be used here to generate beacons that will be accepted by
+ * a real 3ds.
+ */
+constexpr std::array<u8, CryptoPP::AES::BLOCKSIZE> nwm_beacon_key = {};
+
+/**
+ * Generates a buffer with the fixed parameters of an 802.11 Beacon frame
+ * using dummy values.
+ * @returns A buffer with the fixed parameters of the beacon frame.
+ */
+std::vector<u8> GenerateFixedParameters() {
+    std::vector<u8> buffer(sizeof(BeaconFrameHeader));
+
+    BeaconFrameHeader header{};
+    // Use a fixed default time for now.
+    // TODO(Subv): Perhaps use the difference between now and the time the network was started?
+    header.timestamp = DefaultNetworkUptime;
+    header.beacon_interval = DefaultBeaconInterval;
+    header.capabilities = DefaultExtraCapabilities;
+
+    std::memcpy(buffer.data(), &header, sizeof(header));
+
+    return buffer;
+}
+
+/**
+ * Generates an SSID tag of an 802.11 Beacon frame with an 8-byte all-zero SSID value.
+ * @returns A buffer with the SSID tag.
+ */
+std::vector<u8> GenerateSSIDTag() {
+    std::vector<u8> buffer(sizeof(TagHeader) + UDSBeaconSSIDSize);
+
+    TagHeader tag_header{};
+    tag_header.tag_id = static_cast<u8>(TagId::SSID);
+    tag_header.length = UDSBeaconSSIDSize;
+
+    std::memcpy(buffer.data(), &tag_header, sizeof(TagHeader));
+
+    // The rest of the buffer is already filled with zeros.
+
+    return buffer;
+}
+
+/**
+ * Generates a buffer with the basic tagged parameters of an 802.11 Beacon frame
+ * such as SSID, Rate Information, Country Information, etc.
+ * @returns A buffer with the tagged parameters of the beacon frame.
+ */
+std::vector<u8> GenerateBasicTaggedParameters() {
+    // Append the SSID tag
+    std::vector<u8> buffer = GenerateSSIDTag();
+
+    // TODO(Subv): Add the SupportedRates tag.
+    // TODO(Subv): Add the DSParameterSet tag.
+    // TODO(Subv): Add the TrafficIndicationMap tag.
+    // TODO(Subv): Add the CountryInformation tag.
+    // TODO(Subv): Add the ERPInformation tag.
+
+    return buffer;
+}
+
+/**
+ * Generates a buffer with the Dummy Nintendo tag.
+ * It is currently unknown what this tag does.
+ * TODO(Subv): Figure out if this is needed and what it does.
+ * @returns A buffer with the Nintendo tagged parameters of the beacon frame.
+ */
+std::vector<u8> GenerateNintendoDummyTag() {
+    // Note: These values were taken from a packet capture of an o3DS XL
+    // broadcasting a Super Smash Bros. 4 lobby.
+    constexpr std::array<u8, 3> dummy_data = {0x0A, 0x00, 0x00};
+
+    DummyTag tag{};
+    tag.header.tag_id = static_cast<u8>(TagId::VendorSpecific);
+    tag.header.length = sizeof(DummyTag) - sizeof(TagHeader);
+    tag.oui_type = static_cast<u8>(NintendoTagId::Dummy);
+    tag.oui = NintendoOUI;
+    tag.data = dummy_data;
+
+    std::vector<u8> buffer(sizeof(DummyTag));
+    std::memcpy(buffer.data(), &tag, sizeof(DummyTag));
+
+    return buffer;
+}
+
+/**
+ * Generates a buffer with the Network Info Nintendo tag.
+ * This tag contains the network information of the network that is being broadcast.
+ * It also contains the application data provided by the application that opened the network.
+ * @returns A buffer with the Nintendo network info parameter of the beacon frame.
+ */
+std::vector<u8> GenerateNintendoNetworkInfoTag(const NetworkInfo& network_info) {
+    NetworkInfoTag tag{};
+    tag.header.tag_id = static_cast<u8>(TagId::VendorSpecific);
+    tag.header.length =
+        sizeof(NetworkInfoTag) - sizeof(TagHeader) + network_info.application_data_size;
+    tag.appdata_size = network_info.application_data_size;
+    // Set the hash to zero initially, it will be updated once we calculate it.
+    tag.sha_hash = {};
+
+    // Ensure the network structure has the correct OUI and OUI type.
+    ASSERT(network_info.oui_type == static_cast<u8>(NintendoTagId::NetworkInfo));
+    ASSERT(network_info.oui_value == NintendoOUI);
+
+    // Ensure the application data size is less than the maximum value.
+    ASSERT_MSG(network_info.application_data_size <= ApplicationDataSize, "Data size is too big.");
+
+    // This tag contains the network info structure starting at the OUI.
+    std::memcpy(tag.network_info.data(), &network_info.oui_value, tag.network_info.size());
+
+    // Copy the tag and the data so we can calculate the SHA1 over it.
+    std::vector<u8> buffer(sizeof(tag) + network_info.application_data_size);
+    std::memcpy(buffer.data(), &tag, sizeof(tag));
+    std::memcpy(buffer.data() + sizeof(tag), network_info.application_data.data(),
+                network_info.application_data_size);
+
+    // Calculate the SHA1 of the contents of the tag.
+    std::array<u8, CryptoPP::SHA1::DIGESTSIZE> hash;
+    CryptoPP::SHA1().CalculateDigest(hash.data(),
+                                     buffer.data() + offsetof(NetworkInfoTag, network_info),
+                                     buffer.size() - sizeof(TagHeader));
+
+    // Copy it directly into the buffer, overwriting the zeros that we had previously placed there.
+    std::memcpy(buffer.data() + offsetof(NetworkInfoTag, sha_hash), hash.data(), hash.size());
+
+    return buffer;
+}
+
+/*
+ * Calculates the CTR used for the AES-CTR encryption of the data stored in the
+ * EncryptedDataTags.
+ * @returns The CTR used for beacon crypto.
+ */
+std::array<u8, CryptoPP::AES::BLOCKSIZE> GetBeaconCryptoCTR(const NetworkInfo& network_info) {
+    BeaconDataCryptoCTR data{};
+
+    data.host_mac = network_info.host_mac_address;
+    data.wlan_comm_id = network_info.wlan_comm_id;
+    data.id = network_info.id;
+    data.network_id = network_info.network_id;
+
+    std::array<u8, CryptoPP::AES::BLOCKSIZE> hash;
+    std::memcpy(hash.data(), &data, sizeof(data));
+
+    return hash;
+}
+
+/*
+ * Serializes the node information into the format needed for network transfer,
+ * and then encrypts it with the NWM key.
+ * @returns The serialized and encrypted node information.
+ */
+std::vector<u8> GeneratedEncryptedData(const NetworkInfo& network_info, const NodeList& nodes) {
+    std::vector<u8> buffer(sizeof(BeaconData));
+
+    BeaconData data{};
+    std::memcpy(buffer.data(), &data, sizeof(BeaconData));
+
+    for (const NodeInfo& node : nodes) {
+        // Serialize each node and convert the data from
+        // host byte-order to Big Endian.
+        BeaconNodeInfo info{};
+        info.friend_code_seed = node.friend_code_seed;
+        info.network_node_id = node.network_node_id;
+        for (int i = 0; i < info.username.size(); ++i)
+            info.username[i] = node.username[i];
+
+        buffer.insert(buffer.end(), reinterpret_cast<u8*>(&info),
+                      reinterpret_cast<u8*>(&info) + sizeof(info));
+    }
+
+    // Calculate the MD5 hash of the data in the buffer, not including the hash field.
+    std::array<u8, CryptoPP::MD5::DIGESTSIZE> hash;
+    CryptoPP::MD5().CalculateDigest(hash.data(), buffer.data() + offsetof(BeaconData, bitmask),
+                                    buffer.size() - sizeof(data.md5_hash));
+
+    // Copy the hash into the buffer.
+    std::memcpy(buffer.data(), hash.data(), hash.size());
+
+    // Encrypt the data using AES-CTR and the NWM beacon key.
+    using CryptoPP::AES;
+    std::array<u8, AES::BLOCKSIZE> counter = GetBeaconCryptoCTR(network_info);
+    CryptoPP::CTR_Mode<AES>::Encryption aes;
+    aes.SetKeyWithIV(nwm_beacon_key.data(), AES::BLOCKSIZE, counter.data());
+    aes.ProcessData(buffer.data(), buffer.data(), buffer.size());
+
+    return buffer;
+}
+
+void DecryptBeaconData(const NetworkInfo& network_info, std::vector<u8>& buffer) {
+    // Decrypt the data using AES-CTR and the NWM beacon key.
+    using CryptoPP::AES;
+    std::array<u8, AES::BLOCKSIZE> counter = GetBeaconCryptoCTR(network_info);
+    CryptoPP::CTR_Mode<AES>::Decryption aes;
+    aes.SetKeyWithIV(nwm_beacon_key.data(), AES::BLOCKSIZE, counter.data());
+    aes.ProcessData(buffer.data(), buffer.data(), buffer.size());
+}
+
+/**
+ * Generates a buffer with the Network Info Nintendo tag.
+ * This tag contains the first portion of the encrypted payload in the 802.11 beacon frame.
+ * The encrypted payload contains information about the nodes currently connected to the network.
+ * @returns A buffer with the first Nintendo encrypted data parameters of the beacon frame.
+ */
+std::vector<u8> GenerateNintendoFirstEncryptedDataTag(const NetworkInfo& network_info,
+                                                      const NodeList& nodes) {
+    const size_t payload_size =
+        std::min<size_t>(EncryptedDataSizeCutoff, nodes.size() * sizeof(NodeInfo));
+
+    EncryptedDataTag tag{};
+    tag.header.tag_id = static_cast<u8>(TagId::VendorSpecific);
+    tag.header.length = sizeof(tag) - sizeof(TagHeader) + payload_size;
+    tag.oui_type = static_cast<u8>(NintendoTagId::EncryptedData0);
+    tag.oui = NintendoOUI;
+
+    std::vector<u8> buffer(sizeof(tag) + payload_size);
+    std::memcpy(buffer.data(), &tag, sizeof(tag));
+
+    std::vector<u8> encrypted_data = GeneratedEncryptedData(network_info, nodes);
+    std::memcpy(buffer.data() + sizeof(tag), encrypted_data.data(), payload_size);
+
+    return buffer;
+}
+
+/**
+ * Generates a buffer with the Network Info Nintendo tag.
+ * This tag contains the second portion of the encrypted payload in the 802.11 beacon frame.
+ * The encrypted payload contains information about the nodes currently connected to the network.
+ * This tag is only present if the payload size is greater than EncryptedDataSizeCutoff (0xFA)
+ * bytes.
+ * @returns A buffer with the second Nintendo encrypted data parameters of the beacon frame.
+ */
+std::vector<u8> GenerateNintendoSecondEncryptedDataTag(const NetworkInfo& network_info,
+                                                       const NodeList& nodes) {
+    // This tag is only present if the payload is larger than EncryptedDataSizeCutoff (0xFA).
+    if (nodes.size() * sizeof(NodeInfo) <= EncryptedDataSizeCutoff)
+        return {};
+
+    const size_t payload_size = nodes.size() * sizeof(NodeInfo) - EncryptedDataSizeCutoff;
+
+    const size_t tag_length = sizeof(EncryptedDataTag) - sizeof(TagHeader) + payload_size;
+
+    // TODO(Subv): What does the 3DS do when a game has too much data to fit into the tag?
+    ASSERT_MSG(tag_length <= 255, "Data is too big.");
+
+    EncryptedDataTag tag{};
+    tag.header.tag_id = static_cast<u8>(TagId::VendorSpecific);
+    tag.header.length = tag_length;
+    tag.oui_type = static_cast<u8>(NintendoTagId::EncryptedData1);
+    tag.oui = NintendoOUI;
+
+    std::vector<u8> buffer(sizeof(tag) + payload_size);
+    std::memcpy(buffer.data(), &tag, sizeof(tag));
+
+    std::vector<u8> encrypted_data = GeneratedEncryptedData(network_info, nodes);
+    std::memcpy(buffer.data() + sizeof(tag), encrypted_data.data() + EncryptedDataSizeCutoff,
+                payload_size);
+
+    return buffer;
+}
+
+/**
+ * Generates a buffer with the Nintendo tagged parameters of an 802.11 Beacon frame
+ * for UDS communication.
+ * @returns A buffer with the Nintendo tagged parameters of the beacon frame.
+ */
+std::vector<u8> GenerateNintendoTaggedParameters(const NetworkInfo& network_info,
+                                                 const NodeList& nodes) {
+    ASSERT_MSG(network_info.max_nodes == nodes.size(), "Inconsistent network state.");
+
+    std::vector<u8> buffer = GenerateNintendoDummyTag();
+    std::vector<u8> network_info_tag = GenerateNintendoNetworkInfoTag(network_info);
+    std::vector<u8> first_data_tag = GenerateNintendoFirstEncryptedDataTag(network_info, nodes);
+    std::vector<u8> second_data_tag = GenerateNintendoSecondEncryptedDataTag(network_info, nodes);
+
+    buffer.insert(buffer.end(), network_info_tag.begin(), network_info_tag.end());
+    buffer.insert(buffer.end(), first_data_tag.begin(), first_data_tag.end());
+    buffer.insert(buffer.end(), second_data_tag.begin(), second_data_tag.end());
+
+    return buffer;
+}
+
+std::vector<u8> GenerateBeaconFrame(const NetworkInfo& network_info, const NodeList& nodes) {
+    std::vector<u8> buffer = GenerateFixedParameters();
+    std::vector<u8> basic_tags = GenerateBasicTaggedParameters();
+    std::vector<u8> nintendo_tags = GenerateNintendoTaggedParameters(network_info, nodes);
+
+    buffer.insert(buffer.end(), basic_tags.begin(), basic_tags.end());
+    buffer.insert(buffer.end(), nintendo_tags.begin(), nintendo_tags.end());
+
+    return buffer;
+}
+
+std::deque<WifiPacket> GetReceivedPackets(WifiPacket::PacketType type, const MacAddress& sender) {
+    return {};
+}
+} // namespace NWM
+} // namespace Service
diff --git a/src/core/hle/service/nwm/uds_beacon.h b/src/core/hle/service/nwm/uds_beacon.h
new file mode 100644
index 000000000..6df4c4f47
--- /dev/null
+++ b/src/core/hle/service/nwm/uds_beacon.h
@@ -0,0 +1,173 @@
+// Copyright 2017 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <array>
+#include <deque>
+#include <vector>
+#include "common/common_types.h"
+#include "common/swap.h"
+#include "core/hle/service/service.h"
+
+namespace Service {
+namespace NWM {
+
+using MacAddress = std::array<u8, 6>;
+
+/// The maximum number of nodes that can exist in an UDS session.
+constexpr u32 UDSMaxNodes = 16;
+constexpr std::array<u8, 3> NintendoOUI = {0x00, 0x1F, 0x32};
+
+/// Additional block tag ids in the Beacon frames
+enum class TagId : u8 {
+    SSID = 0,
+    SupportedRates = 1,
+    DSParameterSet = 2,
+    TrafficIndicationMap = 5,
+    CountryInformation = 7,
+    ERPInformation = 42,
+    VendorSpecific = 221
+};
+
+/**
+ * Internal vendor-specific tag ids as stored inside
+ * VendorSpecific blocks in the Beacon frames.
+ */
+enum class NintendoTagId : u8 {
+    Dummy = 20,
+    NetworkInfo = 21,
+    EncryptedData0 = 24,
+    EncryptedData1 = 25,
+};
+
+struct BeaconEntryHeader {
+    u32_le total_size;
+    INSERT_PADDING_BYTES(1);
+    u8 wifi_channel;
+    INSERT_PADDING_BYTES(2);
+    MacAddress mac_address;
+    INSERT_PADDING_BYTES(6);
+    u32_le unk_size;
+    u32_le header_size;
+};
+
+static_assert(sizeof(BeaconEntryHeader) == 0x1C, "BeaconEntryHeader has incorrect size.");
+
+struct BeaconDataReplyHeader {
+    u32_le max_output_size;
+    u32_le total_size;
+    u32_le total_entries;
+};
+
+static_assert(sizeof(BeaconDataReplyHeader) == 12, "BeaconDataReplyHeader has incorrect size.");
+
+#pragma pack(push, 1)
+struct BeaconFrameHeader {
+    // Number of microseconds the AP has been active.
+    u64_le timestamp;
+    // Interval between beacon transmissions, expressed in TU.
+    u16_le beacon_interval;
+    // Indicates the presence of optional capabilities.
+    u16_le capabilities;
+};
+#pragma pack(pop)
+
+static_assert(sizeof(BeaconFrameHeader) == 12, "BeaconFrameHeader has incorrect size.");
+
+struct TagHeader {
+    u8 tag_id;
+    u8 length;
+};
+
+static_assert(sizeof(TagHeader) == 2, "TagHeader has incorrect size.");
+
+struct DummyTag {
+    TagHeader header;
+    std::array<u8, 3> oui;
+    u8 oui_type;
+    std::array<u8, 3> data;
+};
+
+static_assert(sizeof(DummyTag) == 9, "DummyTag has incorrect size.");
+
+struct NetworkInfoTag {
+    TagHeader header;
+    std::array<u8, 0x1F> network_info;
+    std::array<u8, 0x14> sha_hash;
+    u8 appdata_size;
+};
+
+static_assert(sizeof(NetworkInfoTag) == 54, "NetworkInfoTag has incorrect size.");
+
+struct EncryptedDataTag {
+    TagHeader header;
+    std::array<u8, 3> oui;
+    u8 oui_type;
+};
+
+static_assert(sizeof(EncryptedDataTag) == 6, "EncryptedDataTag has incorrect size.");
+
+#pragma pack(push, 1)
+// The raw bytes of this structure are the CTR used in the encryption (AES-CTR)
+// of the beacon data stored in the EncryptedDataTags.
+struct BeaconDataCryptoCTR {
+    MacAddress host_mac;
+    u32_le wlan_comm_id;
+    u8 id;
+    INSERT_PADDING_BYTES(1);
+    u32_le network_id;
+};
+
+static_assert(sizeof(BeaconDataCryptoCTR) == 0x10, "BeaconDataCryptoCTR has incorrect size.");
+
+struct BeaconNodeInfo {
+    u64_be friend_code_seed;
+    std::array<u16_be, 10> username;
+    u16_be network_node_id;
+};
+
+static_assert(sizeof(BeaconNodeInfo) == 0x1E, "BeaconNodeInfo has incorrect size.");
+
+struct BeaconData {
+    std::array<u8, 0x10> md5_hash;
+    u16_be bitmask;
+};
+#pragma pack(pop)
+
+static_assert(sizeof(BeaconData) == 0x12, "BeaconData has incorrect size.");
+
+/// Information about a received WiFi packet.
+/// Acts as our own 802.11 header.
+struct WifiPacket {
+    enum class PacketType { Beacon, Data };
+
+    PacketType type; ///< The type of 802.11 frame, Beacon / Data.
+
+    /// Raw 802.11 frame data, starting at the management frame header for management frames.
+    std::vector<u8> data;
+    MacAddress transmitter_address; ///< Mac address of the transmitter.
+    MacAddress destination_address; ///< Mac address of the receiver.
+    u8 channel;                     ///< WiFi channel where this frame was transmitted.
+};
+
+/**
+ * Decrypts the beacon data buffer for the network described by `network_info`.
+ */
+void DecryptBeaconData(const NetworkInfo& network_info, std::vector<u8>& buffer);
+
+/**
+ * Generates an 802.11 beacon frame starting at the management frame header.
+ * This frame contains information about the network and its connected clients.
+ * @returns The generated frame.
+ */
+std::vector<u8> GenerateBeaconFrame(const NetworkInfo& network_info, const NodeList& nodes);
+
+/**
+ * Returns a list of received 802.11 frames from the specified sender
+ * matching the type since the last call.
+ */
+std::deque<WifiPacket> GetReceivedPackets(WifiPacket::PacketType type, const MacAddress& sender);
+} // namespace NWM
+} // namespace Service