feat(lite): merge TUN mode with IPv6 routing

lite/rrpp_core/uot_protocol.py

@@ -0,0 +1,120 @@
+"""SagerNet UDP over TCP v2 帧编解码。
+
+UoT 只负责把 UDP 数据报装入已有的可靠 TCP 字节流；外层连接仍由
+HTTP CONNECT + TLS 建立。此模块不依赖 sing-box。
+"""
+
+from __future__ import annotations
+
+import ipaddress
+import socket
+import struct
+from dataclasses import dataclass
+
+MAGIC_ADDRESS = "sp.v2.udp-over-tcp.arpa"
+MAX_DATAGRAM = 65535
+
+
+@dataclass(frozen=True)
+class Address:
+    host: str
+    port: int
+
+
+def encode_address(host: str, port: int) -> bytes:
+    host = str(host).strip()
+    if not 0 <= int(port) <= 65535:
+        raise ValueError("端口超出范围")
+    try:
+        addr = ipaddress.ip_address(host)
+    except ValueError:
+        raw = host.encode("idna")
+        if not 1 <= len(raw) <= 255:
+            raise ValueError("域名长度超出 UoT 限制")
+        return b"\x02" + bytes([len(raw)]) + raw + struct.pack("!H", int(port))
+    if addr.version == 4:
+        return b"\x00" + addr.packed + struct.pack("!H", int(port))
+    return b"\x01" + addr.packed + struct.pack("!H", int(port))
+
+
+def decode_address(data: bytes, offset: int = 0) -> tuple[Address, int]:
+    if offset >= len(data):
+        raise ValueError("UoT 地址头不完整")
+    atyp = data[offset]
+    offset += 1
+    if atyp == 0:
+        size = 4
+    elif atyp == 1:
+        size = 16
+    elif atyp == 2:
+        if offset >= len(data):
+            raise ValueError("UoT 域名长度缺失")
+        size = data[offset]
+        offset += 1
+    else:
+        raise ValueError(f"未知 UoT 地址类型: {atyp}")
+    end = offset + size
+    if end + 2 > len(data):
+        raise ValueError("UoT 地址头不完整")
+    raw = data[offset:end]
+    port = struct.unpack("!H", data[end:end + 2])[0]
+    if atyp == 0:
+        host = str(ipaddress.IPv4Address(raw))
+    elif atyp == 1:
+        host = str(ipaddress.IPv6Address(raw))
+    else:
+        host = raw.decode("idna")
+    return Address(host, port), end + 2
+
+
+def encode_request(is_connect: bool, destination: Address) -> bytes:
+    return (b"\x01" if is_connect else b"\x00") + encode_address(
+        destination.host, destination.port
+    )
+
+
+def encode_connect_frame(payload: bytes) -> bytes:
+    if len(payload) > MAX_DATAGRAM:
+        raise ValueError("UoT 数据报超过 65535 字节")
+    return struct.pack("!H", len(payload)) + payload
+
+
+def encode_datagram_frame(destination: Address, payload: bytes) -> bytes:
+    if len(payload) > MAX_DATAGRAM:
+        raise ValueError("UoT 数据报超过 65535 字节")
+    return encode_address(destination.host, destination.port) + struct.pack("!H", len(payload)) + payload
+
+
+def read_exact(stream, size: int) -> bytes:
+    chunks = []
+    remaining = size
+    while remaining:
+        chunk = stream.recv(remaining)
+        if not chunk:
+            raise ConnectionError("UoT TCP 流已关闭")
+        chunks.append(chunk)
+        remaining -= len(chunk)
+    return b"".join(chunks)
+
+
+def read_connect_frame(stream) -> bytes:
+    size = struct.unpack("!H", read_exact(stream, 2))[0]
+    return read_exact(stream, size)
+
+
+def read_datagram_frame(stream) -> tuple[Address, bytes]:
+    # 地址是变长的，只能先读 ATYP，再按类型补齐。
+    head = read_exact(stream, 1)
+    atyp = head[0]
+    if atyp == 0:
+        rest = read_exact(stream, 6)
+    elif atyp == 1:
+        rest = read_exact(stream, 18)
+    elif atyp == 2:
+        length = read_exact(stream, 1)
+        rest = length + read_exact(stream, length[0] + 2)
+    else:
+        raise ValueError(f"未知 UoT 地址类型: {atyp}")
+    address, _ = decode_address(head + rest)
+    size = struct.unpack("!H", read_exact(stream, 2))[0]
+    return address, read_exact(stream, size)