Add client abridged protocol

wrappers/packetack/proxy.go

@@ -0,0 +1,99 @@
+package packetack
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"net"
+
+	"github.com/9seconds/mtg/config"
+	"github.com/9seconds/mtg/conntypes"
+	"github.com/9seconds/mtg/hub"
+	"github.com/9seconds/mtg/mtproto/rpc"
+	"github.com/9seconds/mtg/protocol"
+)
+
+type wrapperProxy struct {
+	flags        rpc.ProxyRequestFlags
+	request      *protocol.TelegramRequest
+	clientIPPort []byte
+	ourIPPort    []byte
+	channelRead  hub.ChannelReadCloser
+}
+
+func (w *wrapperProxy) Write(packet conntypes.Packet, acks *conntypes.ConnectionAcks) error {
+	buf := bytes.Buffer{}
+
+	flags := w.flags
+	if acks.Quick {
+		flags |= rpc.ProxyRequestFlagsQuickAck
+	}
+	if bytes.HasPrefix(packet, rpc.ProxyRequestFlagsEncryptedPrefix[:]) {
+		flags |= rpc.ProxyRequestFlagsEncrypted
+	}
+
+	buf.Write(rpc.TagProxyRequest)
+	buf.Write(flags.Bytes())
+	buf.Write(w.request.ConnID[:])
+	buf.Write(w.clientIPPort)
+	buf.Write(w.ourIPPort)
+	buf.Write(rpc.ProxyRequestExtraSize)
+	buf.Write(rpc.ProxyRequestProxyTag)
+	buf.WriteByte(byte(len(config.C.AdTag)))
+	buf.Write(config.C.AdTag)
+	buf.Write(make([]byte, (4-buf.Len()%4)%4))
+	buf.Write(packet)
+
+	return hub.Hub.Write(buf.Bytes(), w.request)
+}
+
+func (w *wrapperProxy) Read(acks *conntypes.ConnectionAcks) (conntypes.Packet, error) {
+	resp, err := w.channelRead.Read()
+	if err != nil {
+		return nil, fmt.Errorf("cannot read a response: %w", err)
+	}
+
+	if resp.Type == rpc.ProxyResponseTypeSimpleAck {
+		acks.Simple = true
+	}
+
+	return resp.Payload, nil
+}
+
+func (w *wrapperProxy) Close() error {
+	return w.channelRead.Close()
+}
+
+func NewProxy(request *protocol.TelegramRequest) conntypes.PacketAckReadWriteCloser {
+	flags := rpc.ProxyRequestFlagsHasAdTag | rpc.ProxyRequestFlagsMagic | rpc.ProxyRequestFlagsExtMode2
+
+	switch request.ClientProtocol.ConnectionType() {
+	case conntypes.ConnectionTypeAbridged:
+		flags |= rpc.ProxyRequestFlagsAbdridged
+	case conntypes.ConnectionTypeIntermediate:
+		flags |= rpc.ProxyRequestFlagsIntermediate
+	case conntypes.ConnectionTypeSecure:
+		flags |= rpc.ProxyRequestFlagsIntermediate | rpc.ProxyRequestFlagsPad
+	default:
+		panic("unknown connection type")
+	}
+
+	return &wrapperProxy{
+		flags:        flags,
+		request:      request,
+		channelRead:  hub.Registry.Register(request.ConnID),
+		clientIPPort: proxyGetIPPort(request.ClientConn.RemoteAddr()),
+		ourIPPort:    proxyGetIPPort(request.ClientConn.LocalAddr()),
+	}
+}
+
+func proxyGetIPPort(addr *net.TCPAddr) []byte {
+	rv := [16 + 4]byte{}
+	port := [4]byte{}
+
+	copy(rv[:16], addr.IP.To16())
+	binary.LittleEndian.PutUint32(port[:], uint32(addr.Port))
+	copy(rv[16:], port[:])
+
+	return rv[:]
+}