Concatenate header and first upstream payload

shadowsocks/client.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"io"
 	"net"
+	"time"
 
 	onet "github.com/Jigsaw-Code/outline-ss-server/net"
 	"github.com/shadowsocks/go-shadowsocks2/core"
@@ -46,6 +47,18 @@ type ssClient struct {
 	cipher    shadowaead.Cipher
 }
 
+// This code contains an optimization to send the initial client payload along with
+// the Shadowsocks handshake.  This saves one packet during connection, and also
+// reduces the distinctiveness of the connection pattern.
+//
+// Normally, the initial payload will be sent as soon as the socket is connected,
+// except for delays due to inter-process communication.  However, some protocols
+// expect the server to send data first, in which case there is no client payload.
+// We therefore use a short delay, longer than any reasonable IPC but similar to
+// typical network latency.  (In an Android emulator, the 90th percentile delay
+// was ~1 ms.)  If no client payload is received by this time, we connect without it.
+const helloWait = 20 * time.Millisecond
+
 func (c *ssClient) DialTCP(laddr *net.TCPAddr, raddr string) (onet.DuplexConn, error) {
 	socksTargetAddr := socks.ParseAddr(raddr)
 	if socksTargetAddr == nil {
@@ -57,11 +70,14 @@ func (c *ssClient) DialTCP(laddr *net.TCPAddr, raddr string) (onet.DuplexConn, e
 		return nil, err
 	}
 	ssw := NewShadowsocksWriter(proxyConn, c.cipher)
-	_, err = ssw.Write(socksTargetAddr)
+	_, err = ssw.LazyWrite(socksTargetAddr)
 	if err != nil {
 		proxyConn.Close()
 		return nil, errors.New("Failed to write target address")
 	}
+	time.AfterFunc(helloWait, func() {
+		ssw.Flush()
+	})
 	ssr := NewShadowsocksReader(proxyConn, c.cipher)
 	return onet.WrapConn(proxyConn, ssr, ssw), nil
 }

shadowsocks/client_test.go

@@ -38,6 +38,28 @@ func TestShadowsocksClient_DialTCP(t *testing.T) {
 	expectEchoPayload(conn, MakeTestPayload(1024), make([]byte, 1024), t)
 }
 
+func TestShadowsocksClient_DialTCPNoPayload(t *testing.T) {
+	proxyAddr := startShadowsocksTCPEchoProxy(testTargetAddr, t)
+	proxyHost, proxyPort, err := splitHostPortNumber(proxyAddr.String())
+	if err != nil {
+		t.Fatalf("Failed to parse proxy address: %v", err)
+	}
+	d, err := NewClient(proxyHost, proxyPort, testPassword, testCipher)
+	if err != nil {
+		t.Fatalf("Failed to create ShadowsocksClient: %v", err)
+	}
+	conn, err := d.DialTCP(nil, testTargetAddr)
+	if err != nil {
+		t.Fatalf("ShadowsocksClient.DialTCP failed: %v", err)
+	}
+
+	// Wait for more than 20 milliseconds to ensure that the target
+	// address is sent.
+	time.Sleep(40 * time.Millisecond)
+	// Force the echo server to verify the target address.
+	conn.Close()
+}
+
 func TestShadowsocksClient_ListenUDP(t *testing.T) {
 	proxyAddr := startShadowsocksUDPEchoServer(testTargetAddr, t)
 	proxyHost, proxyPort, err := splitHostPortNumber(proxyAddr.String())

shadowsocks/stream.go

@@ -21,6 +21,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
+	"sync"
 
 	"github.com/shadowsocks/go-shadowsocks2/shadowaead"
 )
@@ -30,17 +31,35 @@ const payloadSizeMask = 0x3FFF // 16*1024 - 1
 
 // Writer is an io.Writer that also implements io.ReaderFrom to
 // allow for piping the data without extra allocations and copies.
+// The LazyWrite and Flush methods allow a header to be
+// added but delayed until the first write, for concatenation.
+// All methods except Flush must be called from a single thread.
 type Writer interface {
 	io.Writer
 	io.ReaderFrom
+	// LazyWrite queues p to be written, but doesn't send it until
+	// Flush() is called, a non-lazy write is made, or the buffer
+	// is filled.
+	LazyWrite(p []byte) (int, error)
+	// Flush sends the pending data, if any.  This method is
+	// thread-safe, but must not be the first method called.
+	Flush() error
 }
 
 type shadowsocksWriter struct {
-	writer   io.Writer
-	ssCipher shadowaead.Cipher
+	// This type is single-threaded except when needFlush is true.
+	// mu protects needFlush, and also protects everything
+	// else while needFlush could be true.
+	mu sync.Mutex
+	// Indicates that a concurrent flush is currently allowed.
+	needFlush bool
+	writer    io.Writer
+	ssCipher  shadowaead.Cipher
 	// Wrapper for input that arrives as a slice.
 	byteWrapper bytes.Reader
-	// These are lazily initialized:
+	// Number of plaintext bytes that are currently buffered.
+	pending int
+	// These are populated by init():
 	buf  []byte
 	aead cipher.AEAD
 	// Index of the next encrypted chunk to write.
@@ -91,6 +110,42 @@ func (sw *shadowsocksWriter) Write(p []byte) (int, error) {
 	return int(n), err
 }
 
+func (sw *shadowsocksWriter) LazyWrite(p []byte) (int, error) {
+	if err := sw.init(); err != nil {
+		return 0, err
+	}
+
+	// Locking is needed due to potential concurrency with the Flush()
+	// for a previous call to LazyWrite().
+	sw.mu.Lock()
+	defer sw.mu.Unlock()
+
+	queued := 0
+	for {
+		n := sw.enqueue(p)
+		queued += n
+		p = p[n:]
+		if len(p) == 0 {
+			sw.needFlush = true
+			return queued, nil
+		}
+		// p didn't fit in the buffer.  Flush the buffer and try
+		// again.
+		if err := sw.flush(); err != nil {
+			return queued, err
+		}
+	}
+}
+
+func (sw *shadowsocksWriter) Flush() error {
+	sw.mu.Lock()
+	defer sw.mu.Unlock()
+	if !sw.needFlush {
+		return nil
+	}
+	return sw.flush()
+}
+
 func isZero(b []byte) bool {
 	for _, v := range b {
 		if v != 0 {
@@ -100,12 +155,81 @@ func isZero(b []byte) bool {
 	return true
 }
 
+// Returns the slices of sw.buf in which to place plaintext for encryption.
+func (sw *shadowsocksWriter) buffers() (sizeBuf, payloadBuf []byte) {
+	// sw.buf starts with the salt.
+	saltSize := sw.ssCipher.SaltSize()
+
+	// Each Shadowsocks-TCP message consists of a fixed-length size block,
+	// followed by a variable-length payload block.
+	sizeBuf = sw.buf[saltSize : saltSize+2]
+	payloadStart := saltSize + 2 + sw.aead.Overhead()
+	payloadBuf = sw.buf[payloadStart : payloadStart+payloadSizeMask]
+	return
+}
+
 func (sw *shadowsocksWriter) ReadFrom(r io.Reader) (int64, error) {
 	if err := sw.init(); err != nil {
 		return 0, err
 	}
 	var written int64
+	var err error
+	_, payloadBuf := sw.buffers()
 
+	// Special case: one thread-safe read, if necessary
+	sw.mu.Lock()
+	if sw.needFlush {
+		pending := sw.pending
+
+		sw.mu.Unlock()
+		// It's not safe to read into payloadBuf, which may be
+		// modified on the flush thread.
+		// Any size is acceptable here, but this is the largest value
+		// for which a single call to enqueue() is sufficient.
+		readBuf := make([]byte, len(payloadBuf)-pending)
+		var plaintextSize int
+		plaintextSize, err = r.Read(readBuf)
+		written = int64(plaintextSize)
+		sw.mu.Lock()
+
+		sw.enqueue(readBuf[:plaintextSize])
+		readBuf = nil // Release memory before blocking I/O.
+		if flushErr := sw.flush(); flushErr != nil {
+			err = flushErr
+		}
+		sw.needFlush = false
+	}
+	sw.mu.Unlock()
+
+	// Main transfer loop
+	for err == nil {
+		sw.pending, err = r.Read(payloadBuf)
+		written += int64(sw.pending)
+		if flushErr := sw.flush(); flushErr != nil {
+			err = flushErr
+		}
+	}
+
+	if err == io.EOF { // ignore EOF as per io.ReaderFrom contract
+		return written, nil
+	}
+	return written, fmt.Errorf("Failed to read payload: %v", err)
+}
+
+// Adds as much of `plaintext` into the buffer as will fit, and increases
+// sw.pending accordingly.  Returns the number of bytes consumed.
+func (sw *shadowsocksWriter) enqueue(plaintext []byte) int {
+	_, payloadBuf := sw.buffers()
+	n := copy(payloadBuf[sw.pending:], plaintext)
+	sw.pending += n
+	return n
+}
+
+// Encrypts all pending data and writes it to the output.
+func (sw *shadowsocksWriter) flush() error {
+	if sw.pending == 0 {
+		return nil
+	}
 	// sw.buf starts with the salt.
 	saltSize := sw.ssCipher.SaltSize()
 	// Normally we ignore the salt at the beginning of sw.buf.
@@ -117,27 +241,13 @@ func (sw *shadowsocksWriter) ReadFrom(r io.Reader) (int64, error) {
 		start = 0
 	}
 
-	// Each Shadowsocks-TCP message consists of a fixed-length size block, followed by
-	// a variable-length payload block.
-	sizeBuf := sw.buf[saltSize : saltSize+2+sw.aead.Overhead()]
-	payloadBuf := sw.buf[saltSize+len(sizeBuf):]
-	for {
-		plaintextSize, err := r.Read(payloadBuf[:payloadSizeMask])
-		if plaintextSize > 0 {
-			binary.BigEndian.PutUint16(sizeBuf, uint16(plaintextSize))
-			sw.encryptBlock(sizeBuf[:2])
-			payloadSize := sw.encryptBlock(payloadBuf[:plaintextSize])
-			_, err = sw.writer.Write(sw.buf[start : saltSize+len(sizeBuf)+payloadSize])
-			written += int64(plaintextSize)
-			start = saltSize // Skip the salt for all writes except the first.
-		}
-		if err != nil {
-			if err == io.EOF { // ignore EOF as per io.ReaderFrom contract
-				return written, nil
-			}
-			return written, fmt.Errorf("Failed to read payload: %v", err)
-		}
-	}
+	sizeBuf, payloadBuf := sw.buffers()
+	binary.BigEndian.PutUint16(sizeBuf, uint16(sw.pending))
+	sizeBlockSize := sw.encryptBlock(sizeBuf)
+	payloadSize := sw.encryptBlock(payloadBuf[:sw.pending])
+	_, err := sw.writer.Write(sw.buf[start : saltSize+sizeBlockSize+payloadSize])
+	sw.pending = 0
+	return err
 }
 
 // ChunkReader is similar to io.Reader, except that it controls its own