Make min, max, and padding lengths configurable

README.md

@@ -103,7 +103,7 @@ need to make some adjustments to the WireGuard client configuration:
 * Use the address of the `udptlspipe` client as an endpoint in your WireGuard
   client configuration.
 * Add `MTU = 1280` to the `[Peer]` section of both WireGuard client and server
-  configuration files.
+  configuration files. The MTU can be increased by passing custom values for `--max-message-length`, `--min-message-length`, and `--max-padding-length`.
 * Exclude the `udptlspipe` server IP from `AllowedIPs` in the WireGuard client
   configuration. This [calculator][wireguardcalculator] may help you.
 
@@ -237,6 +237,9 @@ Application Options:
       --tls-keyfile=<path-to-key-file>                      Path to the private key for the cert specified in tls-certfile.
       --probe-reverseproxyurl=<hostname>                    Unauthorized requests and probes will be proxied to the URL.
   -v, --verbose                                             Verbose output (optional).
+      --max-message-length=<int length>                     Max message length (default 1320)
+      --min-message-length=<int length>                     Min message length (default 100)
+      --max-padding-length=<int length>                     Max padding length (default 256)
 
 Help Options:
   -h, --help                                                Show this help message
@@ -248,4 +251,4 @@ Help Options:
 * [X] Certificate configuration.
 * [X] Use WebSocket for transport instead of the custom binary proto.
 * [ ] Use several upstream connections instead of a single one.
-* [ ] Automatic TLS certs generation (let's encrypt, lego).
+* [ ] Automatic TLS certs generation (let's encrypt, lego).

internal/cmd/cmd.go

@@ -43,6 +43,18 @@ func Main() {
 		log.SetLevel(log.DEBUG)
 	}
 
+	if o.MaxMessageLength == 0 {
+		o.MaxMessageLength = 1320
+	}
+
+	if o.MaxPaddingLength == 0 {
+		o.MaxPaddingLength = 256
+	}
+
+	if o.MinMessageLength == 0 {
+		o.MinMessageLength = 100
+	}
+
 	log.Info("Configuration:\n%s", o)
 
 	cfg := &pipe.Config{
@@ -54,6 +66,9 @@ func Main() {
 		VerifyCertificate:    o.VerifyCertificate,
 		TLSServerName:        o.TLSServerName,
 		ProbeReverseProxyURL: o.ProbeReverseProxyURL,
+		MaxMessageLength:     o.MaxMessageLength,
+		MinMessageLength:     o.MinMessageLength,
+		MaxPaddingLength:     o.MaxPaddingLength,
 	}
 
 	if o.TLSCertPath != "" {

internal/cmd/options.go

@@ -61,6 +61,17 @@ type Options struct {
 
 	// Verbose defines whether we should write the DEBUG-level log or not.
 	Verbose bool `yaml:"verbose" short:"v" long:"verbose" description:"Verbose output (optional)." optional:"yes" optional-value:"true"`
+
+	// MaxMessageLength is the maximum length that is safe to use.
+	MaxMessageLength int `yaml:"max-message-length" long:"max-message-length" description:"Max message length (default 1320)" value-name:"<int length>" optional:"yes"`
+
+	// MinMessageLength is the minimum message size. If the message is smaller, it
+	// will be padded with random bytes.
+	MinMessageLength int `yaml:"min-message-length" long:"min-message-length" description:"Min message length (default 100)" value-name:"<int length>" optional:"yes"`
+
+	// MaxPaddingLength is the maximum size of a random padding that's added to
+	// every message.
+	MaxPaddingLength int `yaml:"max-padding-length" long:"max-padding-length" description:"Max padding length (default 256)" value-name:"<int length>" optional:"yes"`
 }
 
 // type check

internal/pipe/server.go

@@ -75,6 +75,17 @@ type Server struct {
 	// wg tracks active workers. Stop won't finish until there is at least
 	// won't finish until there's at least one active worker.
 	wg sync.WaitGroup
+
+	// maxMessageLength is the maximum length that is safe to use.
+	maxMessageLength int
+
+	// minMessageLength is the minimum message size. If the message is smaller, it
+	// will be padded with random bytes.
+	minMessageLength int
+
+	// maxPaddingLength is the maximum size of a random padding that's added to
+	// every message.
+	maxPaddingLength int
 }
 
 // Config represents the server configuration.
@@ -125,6 +136,17 @@ type Config struct {
 	// proxy to respond to unauthorized or proxy requests. If not specified,
 	// it will respond with a stub page 403 Forbidden.
 	ProbeReverseProxyURL string
+
+	// MaxMessageLength is the maximum length that is safe to use.
+	MaxMessageLength int
+
+	// MinMessageLength is the minimum message size. If the message is smaller, it
+	// will be padded with random bytes.
+	MinMessageLength int
+
+	// MaxPaddingLength is the maximum size of a random padding that's added to
+	// every message.
+	MaxPaddingLength int
 }
 
 // createTLSConfig creates a TLS configuration as per the server configuration.
@@ -175,6 +197,9 @@ func NewServer(config *Config) (s *Server, err error) {
 		srcConnsMu:           &sync.Mutex{},
 		dstConns:             map[net.Conn]struct{}{},
 		dstConnsMu:           &sync.Mutex{},
+		maxMessageLength:     config.MaxMessageLength,
+		minMessageLength:     config.MinMessageLength,
+		maxPaddingLength:     config.MaxPaddingLength,
 	}
 
 	s.tlsConfig, err = createTLSConfig(config)
@@ -649,9 +674,9 @@ func (s *Server) processConn(rwc io.ReadWriteCloser) {
 	// connection between them needs to be wrapped. In server mode it is the
 	// source connection, in client mode it is the destination connection.
 	if s.serverMode {
-		srcRw = tunnel.NewMsgReadWriter(srcRw)
+		srcRw = tunnel.NewMsgReadWriter(srcRw, s.maxMessageLength, s.minMessageLength, s.maxPaddingLength)
 	} else {
-		dstRw = tunnel.NewMsgReadWriter(dstRw)
+		dstRw = tunnel.NewMsgReadWriter(dstRw, s.maxMessageLength, s.minMessageLength, s.maxPaddingLength)
 	}
 
 	tunnel.Tunnel(s.String(), srcRw, dstRw)

internal/tunnel/msgreadwriter.go

@@ -9,27 +9,26 @@ import (
 	"github.com/AdguardTeam/golibs/log"
 )
 
-// MaxMessageLength is the maximum length that is safe to use.
-// TODO(ameshkov): Make it configurable.
-const MaxMessageLength = 1320
-
-// MinMessageLength is the minimum message size. If the message is smaller, it
-// will be padded with random bytes.
-const MinMessageLength = 100
-
-// MaxPaddingLength is the maximum size of a random padding that's added to
-// every message.
-const MaxPaddingLength = 256
-
-// MsgReadWriter is a wrapper over io.ReadWriter that encodes messages written
-// to and read from the base writer.
 type MsgReadWriter struct {
 	base io.ReadWriter
+	// MaxMessageLength is the maximum length that is safe to use.
+	maxMessageLength int
+	// MaxPaddingLength is the maximum size of a random padding that's added to
+	// every message.
+	maxPaddingLength int
+	// MinMessageLength is the minimum message size. If the message is smaller, it
+	// will be padded with random bytes.
+	minMessageLength int
 }
 
 // NewMsgReadWriter creates a new instance of *MsgReadWriter.
-func NewMsgReadWriter(base io.ReadWriter) (rw *MsgReadWriter) {
-	return &MsgReadWriter{base: base}
+func NewMsgReadWriter(base io.ReadWriter, maxMessageLength, minMessageLength, maxPaddingLength int) (rw *MsgReadWriter) {
+	return &MsgReadWriter{
+		base:             base,
+		maxMessageLength: maxMessageLength,
+		minMessageLength: minMessageLength,
+		maxPaddingLength: maxPaddingLength,
+	}
 }
 
 // type check
@@ -38,13 +37,13 @@ var _ io.ReadWriter = (*MsgReadWriter)(nil)
 // Read implements the io.ReadWriter interface for *MsgReadWriter.
 func (rw *MsgReadWriter) Read(b []byte) (n int, err error) {
 	// Read the main message (always goes first).
-	msg, err := readPrefixed(rw.base)
+	msg, err := rw.readPrefixed(rw.base)
 	if err != nil {
 		return 0, err
 	}
 
 	// Skip padding.
-	_, err = readPrefixed(rw.base)
+	_, err = rw.readPrefixed(rw.base)
 	if err != nil {
 		return 0, err
 	}
@@ -62,11 +61,11 @@ func (rw *MsgReadWriter) Read(b []byte) (n int, err error) {
 func (rw *MsgReadWriter) Write(b []byte) (n int, err error) {
 	// Create random padding to make it harder to understand what's inside
 	// the tunnel.
-	minLength := MinMessageLength - len(b)
+	minLength := rw.minMessageLength - len(b)
 	if minLength <= 0 {
 		minLength = 1
 	}
-	maxLength := MaxPaddingLength
+	maxLength := rw.maxPaddingLength
 	if maxLength <= minLength {
 		maxLength = minLength + 1
 	}
@@ -103,19 +102,19 @@ func pack(b, padding []byte) (msg []byte) {
 }
 
 // readPrefixed reads a 2-byte prefixed byte array from the reader.
-func readPrefixed(r io.Reader) (b []byte, err error) {
+func (rw *MsgReadWriter) readPrefixed(r io.Reader) (b []byte, err error) {
 	var length uint16
 	err = binary.Read(r, binary.BigEndian, &length)
 	if err != nil {
 		return nil, err
 	}
 
-	if length > MaxMessageLength {
+	if length > uint16(rw.maxMessageLength) {
 		// Warn the user that this may not work correctly.
 		log.Error(
 			"Warning: received message of length %d larger than %d, considering reducing the MTU",
 			length,
-			MaxMessageLength,
+			rw.maxMessageLength,
 		)
 	}