feat(quic): replace probe UDP data plane with QUIC datagrams

backend/shared/MoShiro.Protocol/Wire/MeasurementDatagram.cs

@@ -3,7 +3,7 @@ using System.Security.Cryptography;
 
 namespace MoShiro.Protocol;
 
-public enum UdpPacketType : byte
+public enum MeasurementDatagramType : byte
 {
     EchoRequest = 1,
     EchoReply = 2,
@@ -12,7 +12,7 @@ public enum UdpPacketType : byte
     Data = 3,
 }
 
-public readonly record struct UdpHeader(UdpPacketType Type, long SessionId, uint StreamId, uint Seq, long SendTsUs);
+public readonly record struct MeasurementDatagramHeader(MeasurementDatagramType Type, long SessionId, uint StreamId, uint Seq, long SendTsUs);
 
 /// <summary>
 /// 数据面的 UDP 包（Fleet 之外的线格式）：
@@ -20,7 +20,7 @@ public readonly record struct UdpHeader(UdpPacketType Type, long SessionId, uint
 /// mac = HMAC-SHA256(session_key, 前面全部字节) 截断到 16 字节。所有整数小端。
 /// 接收方对不合法的包静默丢弃并计数，不回复（防放大）。
 /// </summary>
-public static class UdpPacket
+public static class MeasurementDatagram
 {
     public const ushort Magic = 0x4D4E; // "MN"
     public const byte Version = 1;
@@ -30,19 +30,19 @@ public static class UdpPacket
     public const int MaxBytes = 1472;
 
     /// <summary>检查长度、magic、version、type 并解析头部（不校验 MAC）。</summary>
-    public static bool TryParseHeader(ReadOnlySpan<byte> packet, out UdpHeader header)
+    public static bool TryParseHeader(ReadOnlySpan<byte> packet, out MeasurementDatagramHeader header)
     {
         header = default;
         if (packet.Length is < MinBytes or > MaxBytes
             || BinaryPrimitives.ReadUInt16LittleEndian(packet) != Magic
             || packet[2] != Version
-            || packet[3] is < (byte)UdpPacketType.EchoRequest or > (byte)UdpPacketType.Data)
+            || packet[3] is < (byte)MeasurementDatagramType.EchoRequest or > (byte)MeasurementDatagramType.Data)
         {
             return false;
         }
 
-        header = new UdpHeader(
-            (UdpPacketType)packet[3],
+        header = new MeasurementDatagramHeader(
+            (MeasurementDatagramType)packet[3],
             BinaryPrimitives.ReadInt64LittleEndian(packet[4..]),
             BinaryPrimitives.ReadUInt32LittleEndian(packet[12..]),
             BinaryPrimitives.ReadUInt32LittleEndian(packet[16..]),
@@ -51,7 +51,7 @@ public static class UdpPacket
     }
 
     /// <summary>写入整个包（长度就是 <paramref name="destination"/> 的长度），填充为零，末尾是 MAC。</summary>
-    public static void Write(Span<byte> destination, in UdpHeader header, ReadOnlySpan<byte> key)
+    public static void Write(Span<byte> destination, in MeasurementDatagramHeader header, ReadOnlySpan<byte> key)
     {
         if (destination.Length is < MinBytes or > MaxBytes)
         {

backend/shared/MoShiro.Protocol/Wire/TcpWire.cs

@@ -19,8 +19,8 @@ public static class TcpWire
 
     public static void WriteAuth(Span<byte> destination, long sessionId, uint streamId, ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> key)
     {
-        BinaryPrimitives.WriteUInt16LittleEndian(destination, UdpPacket.Magic);
-        destination[2] = UdpPacket.Version;
+        BinaryPrimitives.WriteUInt16LittleEndian(destination, MeasurementDatagram.Magic);
+        destination[2] = MeasurementDatagram.Version;
         BinaryPrimitives.WriteInt64LittleEndian(destination[3..], sessionId);
         BinaryPrimitives.WriteUInt32LittleEndian(destination[11..], streamId);
         nonce[..NonceBytes].CopyTo(destination[15..]);
@@ -35,7 +35,7 @@ public static class TcpWire
         sessionId = 0;
         streamId = 0;
         nonce = default;
-        if (frame.Length != AuthBytes || BinaryPrimitives.ReadUInt16LittleEndian(frame) != UdpPacket.Magic || frame[2] != UdpPacket.Version)
+        if (frame.Length != AuthBytes || BinaryPrimitives.ReadUInt16LittleEndian(frame) != MeasurementDatagram.Magic || frame[2] != MeasurementDatagram.Version)
         {
             return false;
         }