#73: Add shadowsocks UDP relay support

cmd/gost/vendor/github.com/Yawning/chacha20/LICENSE

@@ -0,0 +1,122 @@
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cmd/gost/vendor/github.com/Yawning/chacha20/README.md

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+### chacha20 - ChaCha20
+#### Yawning Angel (yawning at schwanenlied dot me)
+
+Yet another Go ChaCha20 implementation.  Everything else I found  was slow,
+didn't support all the variants I need to use, or relied on cgo to go fast.
+
+Features:
+
+ * 20 round, 256 bit key only.  Everything else is pointless and stupid.
+ * IETF 96 bit nonce variant.
+ * XChaCha 24 byte nonce variant.
+ * SSE2 and AVX2 support on amd64 targets.
+ * Incremental encrypt/decrypt support, unlike golang.org/x/crypto/salsa20.
+

cmd/gost/vendor/github.com/Yawning/chacha20/chacha20.go

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+// chacha20.go - A ChaCha stream cipher implementation.
+//
+// To the extent possible under law, Yawning Angel has waived all copyright
+// and related or neighboring rights to chacha20, using the Creative
+// Commons "CC0" public domain dedication. See LICENSE or
+// <http://creativecommons.org/publicdomain/zero/1.0/> for full details.
+
+package chacha20
+
+import (
+	"crypto/cipher"
+	"encoding/binary"
+	"errors"
+	"math"
+	"runtime"
+)
+
+const (
+	// KeySize is the ChaCha20 key size in bytes.
+	KeySize = 32
+
+	// NonceSize is the ChaCha20 nonce size in bytes.
+	NonceSize = 8
+
+	// INonceSize is the IETF ChaCha20 nonce size in bytes.
+	INonceSize = 12
+
+	// XNonceSize is the XChaCha20 nonce size in bytes.
+	XNonceSize = 24
+
+	// HNonceSize is the HChaCha20 nonce size in bytes.
+	HNonceSize = 16
+
+	// BlockSize is the ChaCha20 block size in bytes.
+	BlockSize = 64
+
+	stateSize    = 16
+	chachaRounds = 20
+
+	// The constant "expand 32-byte k" as little endian uint32s.
+	sigma0 = uint32(0x61707865)
+	sigma1 = uint32(0x3320646e)
+	sigma2 = uint32(0x79622d32)
+	sigma3 = uint32(0x6b206574)
+)
+
+var (
+	// ErrInvalidKey is the error returned when the key is invalid.
+	ErrInvalidKey = errors.New("key length must be KeySize bytes")
+
+	// ErrInvalidNonce is the error returned when the nonce is invalid.
+	ErrInvalidNonce = errors.New("nonce length must be NonceSize/INonceSize/XNonceSize bytes")
+
+	// ErrInvalidCounter is the error returned when the counter is invalid.
+	ErrInvalidCounter = errors.New("block counter is invalid (out of range)")
+
+	useUnsafe    = false
+	usingVectors = false
+	blocksFn     = blocksRef
+)
+
+// A Cipher is an instance of ChaCha20/XChaCha20 using a particular key and
+// nonce.
+type Cipher struct {
+	state [stateSize]uint32
+
+	buf  [BlockSize]byte
+	off  int
+	ietf bool
+}
+
+// Reset zeros the key data so that it will no longer appear in the process's
+// memory.
+func (c *Cipher) Reset() {
+	for i := range c.state {
+		c.state[i] = 0
+	}
+	for i := range c.buf {
+		c.buf[i] = 0
+	}
+}
+
+// XORKeyStream sets dst to the result of XORing src with the key stream.  Dst
+// and src may be the same slice but otherwise should not overlap.
+func (c *Cipher) XORKeyStream(dst, src []byte) {
+	if len(dst) < len(src) {
+		src = src[:len(dst)]
+	}
+
+	for remaining := len(src); remaining > 0; {
+		// Process multiple blocks at once.
+		if c.off == BlockSize {
+			nrBlocks := remaining / BlockSize
+			directBytes := nrBlocks * BlockSize
+			if nrBlocks > 0 {
+				blocksFn(&c.state, src, dst, nrBlocks, c.ietf)
+				remaining -= directBytes
+				if remaining == 0 {
+					return
+				}
+				dst = dst[directBytes:]
+				src = src[directBytes:]
+			}
+
+			// If there's a partial block, generate 1 block of keystream into
+			// the internal buffer.
+			blocksFn(&c.state, nil, c.buf[:], 1, c.ietf)
+			c.off = 0
+		}
+
+		// Process partial blocks from the buffered keystream.
+		toXor := BlockSize - c.off
+		if remaining < toXor {
+			toXor = remaining
+		}
+		if toXor > 0 {
+			for i, v := range src[:toXor] {
+				dst[i] = v ^ c.buf[c.off+i]
+			}
+			dst = dst[toXor:]
+			src = src[toXor:]
+
+			remaining -= toXor
+			c.off += toXor
+		}
+	}
+}
+
+// KeyStream sets dst to the raw keystream.
+func (c *Cipher) KeyStream(dst []byte) {
+	for remaining := len(dst); remaining > 0; {
+		// Process multiple blocks at once.
+		if c.off == BlockSize {
+			nrBlocks := remaining / BlockSize
+			directBytes := nrBlocks * BlockSize
+			if nrBlocks > 0 {
+				blocksFn(&c.state, nil, dst, nrBlocks, c.ietf)
+				remaining -= directBytes
+				if remaining == 0 {
+					return
+				}
+				dst = dst[directBytes:]
+			}
+
+			// If there's a partial block, generate 1 block of keystream into
+			// the internal buffer.
+			blocksFn(&c.state, nil, c.buf[:], 1, c.ietf)
+			c.off = 0
+		}
+
+		// Process partial blocks from the buffered keystream.
+		toCopy := BlockSize - c.off
+		if remaining < toCopy {
+			toCopy = remaining
+		}
+		if toCopy > 0 {
+			copy(dst[:toCopy], c.buf[c.off:c.off+toCopy])
+			dst = dst[toCopy:]
+			remaining -= toCopy
+			c.off += toCopy
+		}
+	}
+}
+
+// ReKey reinitializes the ChaCha20/XChaCha20 instance with the provided key
+// and nonce.
+func (c *Cipher) ReKey(key, nonce []byte) error {
+	if len(key) != KeySize {
+		return ErrInvalidKey
+	}
+
+	switch len(nonce) {
+	case NonceSize:
+	case INonceSize:
+	case XNonceSize:
+		var subkey [KeySize]byte
+		var subnonce [HNonceSize]byte
+		copy(subnonce[:], nonce[0:16])
+		HChaCha(key, &subnonce, &subkey)
+		key = subkey[:]
+		nonce = nonce[16:24]
+		defer func() {
+			for i := range subkey {
+				subkey[i] = 0
+			}
+		}()
+	default:
+		return ErrInvalidNonce
+	}
+
+	c.Reset()
+	c.state[0] = sigma0
+	c.state[1] = sigma1
+	c.state[2] = sigma2
+	c.state[3] = sigma3
+	c.state[4] = binary.LittleEndian.Uint32(key[0:4])
+	c.state[5] = binary.LittleEndian.Uint32(key[4:8])
+	c.state[6] = binary.LittleEndian.Uint32(key[8:12])
+	c.state[7] = binary.LittleEndian.Uint32(key[12:16])
+	c.state[8] = binary.LittleEndian.Uint32(key[16:20])
+	c.state[9] = binary.LittleEndian.Uint32(key[20:24])
+	c.state[10] = binary.LittleEndian.Uint32(key[24:28])
+	c.state[11] = binary.LittleEndian.Uint32(key[28:32])
+	c.state[12] = 0
+	if len(nonce) == INonceSize {
+		c.state[13] = binary.LittleEndian.Uint32(nonce[0:4])
+		c.state[14] = binary.LittleEndian.Uint32(nonce[4:8])
+		c.state[15] = binary.LittleEndian.Uint32(nonce[8:12])
+		c.ietf = true
+	} else {
+		c.state[13] = 0
+		c.state[14] = binary.LittleEndian.Uint32(nonce[0:4])
+		c.state[15] = binary.LittleEndian.Uint32(nonce[4:8])
+		c.ietf = false
+	}
+	c.off = BlockSize
+	return nil
+
+}
+
+// Seek sets the block counter to a given offset.
+func (c *Cipher) Seek(blockCounter uint64) error {
+	if c.ietf {
+		if blockCounter > math.MaxUint32 {
+			return ErrInvalidCounter
+		}
+		c.state[12] = uint32(blockCounter)
+	} else {
+		c.state[12] = uint32(blockCounter)
+		c.state[13] = uint32(blockCounter >> 32)
+	}
+	c.off = BlockSize
+	return nil
+}
+
+// NewCipher returns a new ChaCha20/XChaCha20 instance.
+func NewCipher(key, nonce []byte) (*Cipher, error) {
+	c := new(Cipher)
+	if err := c.ReKey(key, nonce); err != nil {
+		return nil, err
+	}
+	return c, nil
+}
+
+// HChaCha is the HChaCha20 hash function used to make XChaCha.
+func HChaCha(key []byte, nonce *[HNonceSize]byte, out *[32]byte) {
+	var x [stateSize]uint32 // Last 4 slots unused, sigma hardcoded.
+	x[0] = binary.LittleEndian.Uint32(key[0:4])
+	x[1] = binary.LittleEndian.Uint32(key[4:8])
+	x[2] = binary.LittleEndian.Uint32(key[8:12])
+	x[3] = binary.LittleEndian.Uint32(key[12:16])
+	x[4] = binary.LittleEndian.Uint32(key[16:20])
+	x[5] = binary.LittleEndian.Uint32(key[20:24])
+	x[6] = binary.LittleEndian.Uint32(key[24:28])
+	x[7] = binary.LittleEndian.Uint32(key[28:32])
+	x[8] = binary.LittleEndian.Uint32(nonce[0:4])
+	x[9] = binary.LittleEndian.Uint32(nonce[4:8])
+	x[10] = binary.LittleEndian.Uint32(nonce[8:12])
+	x[11] = binary.LittleEndian.Uint32(nonce[12:16])
+	hChaChaRef(&x, out)
+}
+
+func init() {
+	switch runtime.GOARCH {
+	case "386", "amd64":
+		// Abuse unsafe to skip calling binary.LittleEndian.PutUint32
+		// in the critical path.  This is a big boost on systems that are
+		// little endian and not overly picky about alignment.
+		useUnsafe = true
+	}
+}
+
+var _ cipher.Stream = (*Cipher)(nil)

cmd/gost/vendor/github.com/Yawning/chacha20/chacha20_amd64.go

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+// chacha20_amd64.go - AMD64 optimized chacha20.
+//
+// To the extent possible under law, Yawning Angel has waived all copyright
+// and related or neighboring rights to chacha20, using the Creative
+// Commons "CC0" public domain dedication. See LICENSE or
+// <http://creativecommons.org/publicdomain/zero/1.0/> for full details.
+
+// +build amd64,!gccgo,!appengine
+
+package chacha20
+
+import (
+	"math"
+)
+
+var usingAVX2 = false
+
+func blocksAmd64SSE2(x *uint32, inp, outp *byte, nrBlocks uint)
+
+func blocksAmd64AVX2(x *uint32, inp, outp *byte, nrBlocks uint)
+
+func cpuidAmd64(cpuidParams *uint32)
+
+func xgetbv0Amd64(xcrVec *uint32)
+
+func blocksAmd64(x *[stateSize]uint32, in []byte, out []byte, nrBlocks int, isIetf bool) {
+	// Probably unneeded, but stating this explicitly simplifies the assembly.
+	if nrBlocks == 0 {
+		return
+	}
+
+	if isIetf {
+		var totalBlocks uint64
+		totalBlocks = uint64(x[8]) + uint64(nrBlocks)
+		if totalBlocks > math.MaxUint32 {
+			panic("chacha20: Exceeded keystream per nonce limit")
+		}
+	}
+
+	if in == nil {
+		for i := range out {
+			out[i] = 0
+		}
+		in = out
+	}
+
+	// Pointless to call the AVX2 code for just a single block, since half of
+	// the output gets discarded...
+	if usingAVX2 && nrBlocks > 1 {
+		blocksAmd64AVX2(&x[0], &in[0], &out[0], uint(nrBlocks))
+	} else {
+		blocksAmd64SSE2(&x[0], &in[0], &out[0], uint(nrBlocks))
+	}
+}
+
+func supportsAVX2() bool {
+	// https://software.intel.com/en-us/articles/how-to-detect-new-instruction-support-in-the-4th-generation-intel-core-processor-family
+	const (
+		osXsaveBit = 1 << 27
+		avx2Bit    = 1 << 5
+	)
+
+	// Check to see if CPUID actually supports the leaf that indicates AVX2.
+	// CPUID.(EAX=0H, ECX=0H) >= 7
+	regs := [4]uint32{0x00}
+	cpuidAmd64(&regs[0])
+	if regs[0] < 7 {
+		return false
+	}
+
+	// Check to see if the OS knows how to save/restore XMM/YMM state.
+	// CPUID.(EAX=01H, ECX=0H):ECX.OSXSAVE[bit 27]==1
+	regs = [4]uint32{0x01}
+	cpuidAmd64(&regs[0])
+	if regs[2]&osXsaveBit == 0 {
+		return false
+	}
+	xcrRegs := [2]uint32{}
+	xgetbv0Amd64(&xcrRegs[0])
+	if xcrRegs[0]&6 != 6 {
+		return false
+	}
+
+	// Check for AVX2 support.
+	// CPUID.(EAX=07H, ECX=0H):EBX.AVX2[bit 5]==1
+	regs = [4]uint32{0x07}
+	cpuidAmd64(&regs[0])
+	return regs[1]&avx2Bit != 0
+}
+
+func init() {
+	blocksFn = blocksAmd64
+	usingVectors = true
+	usingAVX2 = supportsAVX2()
+}

cmd/gost/vendor/github.com/Yawning/chacha20/chacha20_ref.go

@@ -0,0 +1,392 @@
+// chacha20_ref.go - Reference ChaCha20.
+//
+// To the extent possible under law, Yawning Angel has waived all copyright
+// and related or neighboring rights to chacha20, using the Creative
+// Commons "CC0" public domain dedication. See LICENSE or
+// <http://creativecommons.org/publicdomain/zero/1.0/> for full details.
+
+package chacha20
+
+import (
+	"encoding/binary"
+	"math"
+	"unsafe"
+)
+
+func blocksRef(x *[stateSize]uint32, in []byte, out []byte, nrBlocks int, isIetf bool) {
+	if isIetf {
+		var totalBlocks uint64
+		totalBlocks = uint64(x[8]) + uint64(nrBlocks)
+		if totalBlocks > math.MaxUint32 {
+			panic("chacha20: Exceeded keystream per nonce limit")
+		}
+	}
+
+	// This routine ignores x[0]...x[4] in favor the const values since it's
+	// ever so slightly faster.
+
+	for n := 0; n < nrBlocks; n++ {
+		x0, x1, x2, x3 := sigma0, sigma1, sigma2, sigma3
+		x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15 := x[4], x[5], x[6], x[7], x[8], x[9], x[10], x[11], x[12], x[13], x[14], x[15]
+
+		for i := chachaRounds; i > 0; i -= 2 {
+			// quarterround(x, 0, 4, 8, 12)
+			x0 += x4
+			x12 ^= x0
+			x12 = (x12 << 16) | (x12 >> 16)
+			x8 += x12
+			x4 ^= x8
+			x4 = (x4 << 12) | (x4 >> 20)
+			x0 += x4
+			x12 ^= x0
+			x12 = (x12 << 8) | (x12 >> 24)
+			x8 += x12
+			x4 ^= x8
+			x4 = (x4 << 7) | (x4 >> 25)
+
+			// quarterround(x, 1, 5, 9, 13)
+			x1 += x5
+			x13 ^= x1
+			x13 = (x13 << 16) | (x13 >> 16)
+			x9 += x13
+			x5 ^= x9
+			x5 = (x5 << 12) | (x5 >> 20)
+			x1 += x5
+			x13 ^= x1
+			x13 = (x13 << 8) | (x13 >> 24)
+			x9 += x13
+			x5 ^= x9
+			x5 = (x5 << 7) | (x5 >> 25)
+
+			// quarterround(x, 2, 6, 10, 14)
+			x2 += x6
+			x14 ^= x2
+			x14 = (x14 << 16) | (x14 >> 16)
+			x10 += x14
+			x6 ^= x10
+			x6 = (x6 << 12) | (x6 >> 20)
+			x2 += x6
+			x14 ^= x2
+			x14 = (x14 << 8) | (x14 >> 24)
+			x10 += x14
+			x6 ^= x10
+			x6 = (x6 << 7) | (x6 >> 25)
+
+			// quarterround(x, 3, 7, 11, 15)
+			x3 += x7
+			x15 ^= x3
+			x15 = (x15 << 16) | (x15 >> 16)
+			x11 += x15
+			x7 ^= x11
+			x7 = (x7 << 12) | (x7 >> 20)
+			x3 += x7
+			x15 ^= x3
+			x15 = (x15 << 8) | (x15 >> 24)
+			x11 += x15
+			x7 ^= x11
+			x7 = (x7 << 7) | (x7 >> 25)
+
+			// quarterround(x, 0, 5, 10, 15)
+			x0 += x5
+			x15 ^= x0
+			x15 = (x15 << 16) | (x15 >> 16)
+			x10 += x15
+			x5 ^= x10
+			x5 = (x5 << 12) | (x5 >> 20)
+			x0 += x5
+			x15 ^= x0
+			x15 = (x15 << 8) | (x15 >> 24)
+			x10 += x15
+			x5 ^= x10
+			x5 = (x5 << 7) | (x5 >> 25)
+
+			// quarterround(x, 1, 6, 11, 12)
+			x1 += x6
+			x12 ^= x1
+			x12 = (x12 << 16) | (x12 >> 16)
+			x11 += x12
+			x6 ^= x11
+			x6 = (x6 << 12) | (x6 >> 20)
+			x1 += x6
+			x12 ^= x1
+			x12 = (x12 << 8) | (x12 >> 24)
+			x11 += x12
+			x6 ^= x11
+			x6 = (x6 << 7) | (x6 >> 25)
+
+			// quarterround(x, 2, 7, 8, 13)
+			x2 += x7
+			x13 ^= x2
+			x13 = (x13 << 16) | (x13 >> 16)
+			x8 += x13
+			x7 ^= x8
+			x7 = (x7 << 12) | (x7 >> 20)
+			x2 += x7
+			x13 ^= x2
+			x13 = (x13 << 8) | (x13 >> 24)
+			x8 += x13
+			x7 ^= x8
+			x7 = (x7 << 7) | (x7 >> 25)
+
+			// quarterround(x, 3, 4, 9, 14)
+			x3 += x4
+			x14 ^= x3
+			x14 = (x14 << 16) | (x14 >> 16)
+			x9 += x14
+			x4 ^= x9
+			x4 = (x4 << 12) | (x4 >> 20)
+			x3 += x4
+			x14 ^= x3
+			x14 = (x14 << 8) | (x14 >> 24)
+			x9 += x14
+			x4 ^= x9
+			x4 = (x4 << 7) | (x4 >> 25)
+		}
+
+		// On amd64 at least, this is a rather big boost.
+		if useUnsafe {
+			if in != nil {
+				inArr := (*[16]uint32)(unsafe.Pointer(&in[n*BlockSize]))
+				outArr := (*[16]uint32)(unsafe.Pointer(&out[n*BlockSize]))
+				outArr[0] = inArr[0] ^ (x0 + sigma0)
+				outArr[1] = inArr[1] ^ (x1 + sigma1)
+				outArr[2] = inArr[2] ^ (x2 + sigma2)
+				outArr[3] = inArr[3] ^ (x3 + sigma3)
+				outArr[4] = inArr[4] ^ (x4 + x[4])
+				outArr[5] = inArr[5] ^ (x5 + x[5])
+				outArr[6] = inArr[6] ^ (x6 + x[6])
+				outArr[7] = inArr[7] ^ (x7 + x[7])
+				outArr[8] = inArr[8] ^ (x8 + x[8])
+				outArr[9] = inArr[9] ^ (x9 + x[9])
+				outArr[10] = inArr[10] ^ (x10 + x[10])
+				outArr[11] = inArr[11] ^ (x11 + x[11])
+				outArr[12] = inArr[12] ^ (x12 + x[12])
+				outArr[13] = inArr[13] ^ (x13 + x[13])
+				outArr[14] = inArr[14] ^ (x14 + x[14])
+				outArr[15] = inArr[15] ^ (x15 + x[15])
+			} else {
+				outArr := (*[16]uint32)(unsafe.Pointer(&out[n*BlockSize]))
+				outArr[0] = x0 + sigma0
+				outArr[1] = x1 + sigma1
+				outArr[2] = x2 + sigma2
+				outArr[3] = x3 + sigma3
+				outArr[4] = x4 + x[4]
+				outArr[5] = x5 + x[5]
+				outArr[6] = x6 + x[6]
+				outArr[7] = x7 + x[7]
+				outArr[8] = x8 + x[8]
+				outArr[9] = x9 + x[9]
+				outArr[10] = x10 + x[10]
+				outArr[11] = x11 + x[11]
+				outArr[12] = x12 + x[12]
+				outArr[13] = x13 + x[13]
+				outArr[14] = x14 + x[14]
+				outArr[15] = x15 + x[15]
+			}
+		} else {
+			// Slow path, either the architecture cares about alignment, or is not little endian.
+			x0 += sigma0
+			x1 += sigma1
+			x2 += sigma2
+			x3 += sigma3
+			x4 += x[4]
+			x5 += x[5]
+			x6 += x[6]
+			x7 += x[7]
+			x8 += x[8]
+			x9 += x[9]
+			x10 += x[10]
+			x11 += x[11]
+			x12 += x[12]
+			x13 += x[13]
+			x14 += x[14]
+			x15 += x[15]
+			if in != nil {
+				binary.LittleEndian.PutUint32(out[0:4], binary.LittleEndian.Uint32(in[0:4])^x0)
+				binary.LittleEndian.PutUint32(out[4:8], binary.LittleEndian.Uint32(in[4:8])^x1)
+				binary.LittleEndian.PutUint32(out[8:12], binary.LittleEndian.Uint32(in[8:12])^x2)
+				binary.LittleEndian.PutUint32(out[12:16], binary.LittleEndian.Uint32(in[12:16])^x3)
+				binary.LittleEndian.PutUint32(out[16:20], binary.LittleEndian.Uint32(in[16:20])^x4)
+				binary.LittleEndian.PutUint32(out[20:24], binary.LittleEndian.Uint32(in[20:24])^x5)
+				binary.LittleEndian.PutUint32(out[24:28], binary.LittleEndian.Uint32(in[24:28])^x6)
+				binary.LittleEndian.PutUint32(out[28:32], binary.LittleEndian.Uint32(in[28:32])^x7)
+				binary.LittleEndian.PutUint32(out[32:36], binary.LittleEndian.Uint32(in[32:36])^x8)
+				binary.LittleEndian.PutUint32(out[36:40], binary.LittleEndian.Uint32(in[36:40])^x9)
+				binary.LittleEndian.PutUint32(out[40:44], binary.LittleEndian.Uint32(in[40:44])^x10)
+				binary.LittleEndian.PutUint32(out[44:48], binary.LittleEndian.Uint32(in[44:48])^x11)
+				binary.LittleEndian.PutUint32(out[48:52], binary.LittleEndian.Uint32(in[48:52])^x12)
+				binary.LittleEndian.PutUint32(out[52:56], binary.LittleEndian.Uint32(in[52:56])^x13)
+				binary.LittleEndian.PutUint32(out[56:60], binary.LittleEndian.Uint32(in[56:60])^x14)
+				binary.LittleEndian.PutUint32(out[60:64], binary.LittleEndian.Uint32(in[60:64])^x15)
+				in = in[BlockSize:]
+			} else {
+				binary.LittleEndian.PutUint32(out[0:4], x0)
+				binary.LittleEndian.PutUint32(out[4:8], x1)
+				binary.LittleEndian.PutUint32(out[8:12], x2)
+				binary.LittleEndian.PutUint32(out[12:16], x3)
+				binary.LittleEndian.PutUint32(out[16:20], x4)
+				binary.LittleEndian.PutUint32(out[20:24], x5)
+				binary.LittleEndian.PutUint32(out[24:28], x6)
+				binary.LittleEndian.PutUint32(out[28:32], x7)
+				binary.LittleEndian.PutUint32(out[32:36], x8)
+				binary.LittleEndian.PutUint32(out[36:40], x9)
+				binary.LittleEndian.PutUint32(out[40:44], x10)
+				binary.LittleEndian.PutUint32(out[44:48], x11)
+				binary.LittleEndian.PutUint32(out[48:52], x12)
+				binary.LittleEndian.PutUint32(out[52:56], x13)
+				binary.LittleEndian.PutUint32(out[56:60], x14)
+				binary.LittleEndian.PutUint32(out[60:64], x15)
+			}
+			out = out[BlockSize:]
+		}
+
+		// Stoping at 2^70 bytes per nonce is the user's responsibility.
+		ctr := uint64(x[13])<<32 | uint64(x[12])
+		ctr++
+		x[12] = uint32(ctr)
+		x[13] = uint32(ctr >> 32)
+	}
+}
+
+func hChaChaRef(x *[stateSize]uint32, out *[32]byte) {
+	x0, x1, x2, x3 := sigma0, sigma1, sigma2, sigma3
+	x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15 := x[0], x[1], x[2], x[3], x[4], x[5], x[6], x[7], x[8], x[9], x[10], x[11]
+
+	for i := chachaRounds; i > 0; i -= 2 {
+		// quarterround(x, 0, 4, 8, 12)
+		x0 += x4
+		x12 ^= x0
+		x12 = (x12 << 16) | (x12 >> 16)
+		x8 += x12
+		x4 ^= x8
+		x4 = (x4 << 12) | (x4 >> 20)
+		x0 += x4
+		x12 ^= x0
+		x12 = (x12 << 8) | (x12 >> 24)
+		x8 += x12
+		x4 ^= x8
+		x4 = (x4 << 7) | (x4 >> 25)
+
+		// quarterround(x, 1, 5, 9, 13)
+		x1 += x5
+		x13 ^= x1
+		x13 = (x13 << 16) | (x13 >> 16)
+		x9 += x13
+		x5 ^= x9
+		x5 = (x5 << 12) | (x5 >> 20)
+		x1 += x5
+		x13 ^= x1
+		x13 = (x13 << 8) | (x13 >> 24)
+		x9 += x13
+		x5 ^= x9
+		x5 = (x5 << 7) | (x5 >> 25)
+
+		// quarterround(x, 2, 6, 10, 14)
+		x2 += x6
+		x14 ^= x2
+		x14 = (x14 << 16) | (x14 >> 16)
+		x10 += x14
+		x6 ^= x10
+		x6 = (x6 << 12) | (x6 >> 20)
+		x2 += x6
+		x14 ^= x2
+		x14 = (x14 << 8) | (x14 >> 24)
+		x10 += x14
+		x6 ^= x10
+		x6 = (x6 << 7) | (x6 >> 25)
+
+		// quarterround(x, 3, 7, 11, 15)
+		x3 += x7
+		x15 ^= x3
+		x15 = (x15 << 16) | (x15 >> 16)
+		x11 += x15
+		x7 ^= x11
+		x7 = (x7 << 12) | (x7 >> 20)
+		x3 += x7
+		x15 ^= x3
+		x15 = (x15 << 8) | (x15 >> 24)
+		x11 += x15
+		x7 ^= x11
+		x7 = (x7 << 7) | (x7 >> 25)
+
+		// quarterround(x, 0, 5, 10, 15)
+		x0 += x5
+		x15 ^= x0
+		x15 = (x15 << 16) | (x15 >> 16)
+		x10 += x15
+		x5 ^= x10
+		x5 = (x5 << 12) | (x5 >> 20)
+		x0 += x5
+		x15 ^= x0
+		x15 = (x15 << 8) | (x15 >> 24)
+		x10 += x15
+		x5 ^= x10
+		x5 = (x5 << 7) | (x5 >> 25)
+
+		// quarterround(x, 1, 6, 11, 12)
+		x1 += x6
+		x12 ^= x1
+		x12 = (x12 << 16) | (x12 >> 16)
+		x11 += x12
+		x6 ^= x11
+		x6 = (x6 << 12) | (x6 >> 20)
+		x1 += x6
+		x12 ^= x1
+		x12 = (x12 << 8) | (x12 >> 24)
+		x11 += x12
+		x6 ^= x11
+		x6 = (x6 << 7) | (x6 >> 25)
+
+		// quarterround(x, 2, 7, 8, 13)
+		x2 += x7
+		x13 ^= x2
+		x13 = (x13 << 16) | (x13 >> 16)
+		x8 += x13
+		x7 ^= x8
+		x7 = (x7 << 12) | (x7 >> 20)
+		x2 += x7
+		x13 ^= x2
+		x13 = (x13 << 8) | (x13 >> 24)
+		x8 += x13
+		x7 ^= x8
+		x7 = (x7 << 7) | (x7 >> 25)
+
+		// quarterround(x, 3, 4, 9, 14)
+		x3 += x4
+		x14 ^= x3
+		x14 = (x14 << 16) | (x14 >> 16)
+		x9 += x14
+		x4 ^= x9
+		x4 = (x4 << 12) | (x4 >> 20)
+		x3 += x4
+		x14 ^= x3
+		x14 = (x14 << 8) | (x14 >> 24)
+		x9 += x14
+		x4 ^= x9
+		x4 = (x4 << 7) | (x4 >> 25)
+	}
+
+	// HChaCha returns x0...x3 | x12...x15, which corresponds to the
+	// indexes of the ChaCha constant and the indexes of the IV.
+	if useUnsafe {
+		outArr := (*[16]uint32)(unsafe.Pointer(&out[0]))
+		outArr[0] = x0
+		outArr[1] = x1
+		outArr[2] = x2
+		outArr[3] = x3
+		outArr[4] = x12
+		outArr[5] = x13
+		outArr[6] = x14
+		outArr[7] = x15
+	} else {
+		binary.LittleEndian.PutUint32(out[0:4], x0)
+		binary.LittleEndian.PutUint32(out[4:8], x1)
+		binary.LittleEndian.PutUint32(out[8:12], x2)
+		binary.LittleEndian.PutUint32(out[12:16], x3)
+		binary.LittleEndian.PutUint32(out[16:20], x12)
+		binary.LittleEndian.PutUint32(out[20:24], x13)
+		binary.LittleEndian.PutUint32(out[24:28], x14)
+		binary.LittleEndian.PutUint32(out[28:32], x15)
+	}
+	return
+}

cmd/gost/vendor/github.com/ginuerzh/gost/forward.go

@@ -63,15 +63,15 @@ func (s *TcpForwardServer) handleTcpForward(conn net.Conn, raddr net.Addr) {
 }
 
 type packet struct {
-	srcAddr *net.UDPAddr // src address
+	srcAddr string // src address
-	dstAddr *net.UDPAddr // dest address
+	dstAddr string // dest address
 	data    []byte
 }
 
 type cnode struct {
 	chain            *ProxyChain
 	conn             net.Conn
-	srcAddr, dstAddr *net.UDPAddr
+	srcAddr, dstAddr string
 	rChan, wChan     chan *packet
 	err              error
 	ttl              time.Duration
@@ -146,13 +146,9 @@ func (node *cnode) run() {
 				timer.Reset(node.ttl)
 				glog.V(LDEBUG).Infof("[udp] %s <<< %s : length %d", node.srcAddr, addr, n)
 
-				if node.dstAddr.String() != addr.String() {
-					glog.V(LWARNING).Infof("[udp] %s <- %s : dst-addr mismatch (%s)", node.srcAddr, node.dstAddr, addr)
-					break
-				}
 				select {
 				// swap srcAddr with dstAddr
-				case node.rChan <- &packet{srcAddr: node.dstAddr, dstAddr: node.srcAddr, data: b[:n]}:
+				case node.rChan <- &packet{srcAddr: addr.String(), dstAddr: node.srcAddr, data: b[:n]}:
 				case <-time.After(time.Second * 3):
 					glog.V(LWARNING).Infof("[udp] %s <- %s : %s", node.srcAddr, node.dstAddr, "recv queue is full, discard")
 				}
@@ -169,13 +165,9 @@ func (node *cnode) run() {
 				timer.Reset(node.ttl)
 				glog.V(LDEBUG).Infof("[udp-tun] %s <<< %s : length %d", node.srcAddr, dgram.Header.Addr.String(), len(dgram.Data))
 
-				if dgram.Header.Addr.String() != node.dstAddr.String() {
-					glog.V(LWARNING).Infof("[udp-tun] %s <- %s : dst-addr mismatch (%s)", node.srcAddr, node.dstAddr, dgram.Header.Addr)
-					break
-				}
 				select {
 				// swap srcAddr with dstAddr
-				case node.rChan <- &packet{srcAddr: node.dstAddr, dstAddr: node.srcAddr, data: dgram.Data}:
+				case node.rChan <- &packet{srcAddr: dgram.Header.Addr.String(), dstAddr: node.srcAddr, data: dgram.Data}:
 				case <-time.After(time.Second * 3):
 					glog.V(LWARNING).Infof("[udp-tun] %s <- %s : %s", node.srcAddr, node.dstAddr, "recv queue is full, discard")
 				}
@@ -187,9 +179,15 @@ func (node *cnode) run() {
 		for pkt := range node.wChan {
 			timer.Reset(node.ttl)
 
+			dstAddr, err := net.ResolveUDPAddr("udp", pkt.dstAddr)
+			if err != nil {
+				glog.V(LWARNING).Infof("[udp] %s -> %s : %s", pkt.srcAddr, pkt.dstAddr, err)
+				continue
+			}
+
 			switch c := node.conn.(type) {
 			case *net.UDPConn:
-				if _, err := c.WriteToUDP(pkt.data, pkt.dstAddr); err != nil {
+				if _, err := c.WriteToUDP(pkt.data, dstAddr); err != nil {
 					glog.V(LWARNING).Infof("[udp] %s -> %s : %s", pkt.srcAddr, pkt.dstAddr, err)
 					node.err = err
 					errChan <- err
@@ -198,7 +196,7 @@ func (node *cnode) run() {
 				glog.V(LDEBUG).Infof("[udp] %s >>> %s : length %d", pkt.srcAddr, pkt.dstAddr, len(pkt.data))
 
 			default:
-				dgram := gosocks5.NewUDPDatagram(gosocks5.NewUDPHeader(uint16(len(pkt.data)), 0, ToSocksAddr(pkt.dstAddr)), pkt.data)
+				dgram := gosocks5.NewUDPDatagram(gosocks5.NewUDPHeader(uint16(len(pkt.data)), 0, ToSocksAddr(dstAddr)), pkt.data)
 				if err := dgram.Write(c); err != nil {
 					glog.V(LWARNING).Infof("[udp-tun] %s -> %s : %s", pkt.srcAddr, pkt.dstAddr, err)
 					node.err = err
@@ -255,7 +253,7 @@ func (s *UdpForwardServer) ListenAndServe() error {
 			}
 
 			select {
-			case ch <- &packet{srcAddr: addr, dstAddr: raddr, data: b[:n]}:
+			case ch <- &packet{srcAddr: addr.String(), dstAddr: raddr.String(), data: b[:n]}:
 			case <-time.After(time.Second * 3):
 				glog.V(LWARNING).Infof("[udp] %s -> %s : %s", addr, raddr, "send queue is full, discard")
 			}
@@ -264,7 +262,12 @@ func (s *UdpForwardServer) ListenAndServe() error {
 	// start recv queue
 	go func(ch <-chan *packet) {
 		for pkt := range ch {
-			if _, err := conn.WriteToUDP(pkt.data, pkt.dstAddr); err != nil {
+			dstAddr, err := net.ResolveUDPAddr("udp", pkt.dstAddr)
+			if err != nil {
+				glog.V(LWARNING).Infof("[udp] %s <- %s : %s", pkt.dstAddr, pkt.srcAddr, err)
+				continue
+			}
+			if _, err := conn.WriteToUDP(pkt.data, dstAddr); err != nil {
 				glog.V(LWARNING).Infof("[udp] %s <- %s : %s", pkt.dstAddr, pkt.srcAddr, err)
 				return
 			}
@@ -285,7 +288,7 @@ func (s *UdpForwardServer) ListenAndServe() error {
 			}
 		}
 
-		node, ok := m[pkt.srcAddr.String()]
+		node, ok := m[pkt.srcAddr]
 		if !ok {
 			node = &cnode{
 				chain:   s.Base.Chain,
@@ -295,7 +298,7 @@ func (s *UdpForwardServer) ListenAndServe() error {
 				wChan:   make(chan *packet, 32),
 				ttl:     time.Duration(s.TTL) * time.Second,
 			}
-			m[pkt.srcAddr.String()] = node
+			m[pkt.srcAddr] = node
 			go node.run()
 			glog.V(LINFO).Infof("[udp] %s -> %s : new client (%d)", pkt.srcAddr, pkt.dstAddr, len(m))
 		}

cmd/gost/vendor/github.com/ginuerzh/gost/gost.go

@@ -11,7 +11,7 @@ import (
 )
 
 const (
-	Version = "2.3"
+	Version = "2.4-dev"
 )
 
 // Log level for glog

cmd/gost/vendor/github.com/ginuerzh/gost/node.go

@@ -71,7 +71,7 @@ func ParseProxyNode(s string) (node ProxyNode, err error) {
 	}
 
 	switch node.Transport {
-	case "ws", "wss", "tls", "http2", "ssu", "quic", "kcp", "redirect":
+	case "ws", "wss", "tls", "http2", "quic", "kcp", "redirect", "ssu":
 	case "https":
 		node.Protocol = "http"
 		node.Transport = "tls"

cmd/gost/vendor/github.com/ginuerzh/gost/server.go

@@ -32,7 +32,7 @@ func NewProxyServer(node ProxyNode, chain *ProxyChain, config *tls.Config) *Prox
 
 	var cipher *ss.Cipher
 	var ota bool
-	if node.Protocol == "ss" {
+	if node.Protocol == "ss" || node.Transport == "ssu" {
 		var err error
 		var method, password string
 
@@ -98,8 +98,6 @@ func (s *ProxyServer) Serve() error {
 		return NewRTcpForwardServer(s).Serve()
 	case "rudp": // Remote UDP port forwarding
 		return NewRUdpForwardServer(s).Serve()
-	case "ssu": // TODO: shadowsocks udp relay
-		return NewShadowUdpServer(s).ListenAndServe()
 	case "quic":
 		return NewQuicServer(s).ListenAndServeTLS(s.TLSConfig)
 	case "kcp":
@@ -118,6 +116,12 @@ func (s *ProxyServer) Serve() error {
 		return NewKCPServer(s, config).ListenAndServe()
 	case "redirect":
 		return NewRedsocksTCPServer(s).ListenAndServe()
+	case "ssu": // shadowsocks udp relay
+		ttl, _ := strconv.Atoi(s.Node.Get("ttl"))
+		if ttl <= 0 {
+			ttl = DefaultTTL
+		}
+		return NewShadowUdpServer(s, ttl).ListenAndServe()
 	default:
 		ln, err = net.Listen("tcp", node.Addr)
 	}

cmd/gost/vendor/github.com/ginuerzh/gost/ss.go

@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"github.com/ginuerzh/gosocks5"
 	"github.com/golang/glog"
 	ss "github.com/shadowsocks/shadowsocks-go/shadowsocks"
 	"io"
@@ -65,47 +66,6 @@ func (s *ShadowServer) Serve() {
 	glog.V(LINFO).Infof("[ss] %s >-< %s", s.conn.RemoteAddr(), addr)
 }
 
-type ShadowUdpServer struct {
-	Base    *ProxyServer
-	Handler func(conn *net.UDPConn, addr *net.UDPAddr, data []byte)
-}
-
-func NewShadowUdpServer(base *ProxyServer) *ShadowUdpServer {
-	return &ShadowUdpServer{Base: base}
-}
-
-func (s *ShadowUdpServer) ListenAndServe() error {
-	laddr, err := net.ResolveUDPAddr("udp", s.Base.Node.Addr)
-	if err != nil {
-		return err
-	}
-	lconn, err := net.ListenUDP("udp", laddr)
-	if err != nil {
-		return err
-	}
-	defer lconn.Close()
-
-	if s.Handler == nil {
-		s.Handler = s.HandleConn
-	}
-
-	for {
-		b := make([]byte, LargeBufferSize)
-		n, addr, err := lconn.ReadFromUDP(b)
-		if err != nil {
-			glog.V(LWARNING).Infoln(err)
-			continue
-		}
-
-		go s.Handler(lconn, addr, b[:n])
-	}
-}
-
-// TODO: shadowsocks udp relay handler
-func (s *ShadowUdpServer) HandleConn(conn *net.UDPConn, addr *net.UDPAddr, data []byte) {
-
-}
-
 // This function is copied from shadowsocks library with some modification.
 func (s *ShadowServer) getRequest() (host string, ota bool, err error) {
 	// buf size should at least have the same size with the largest possible
@@ -276,3 +236,109 @@ func (c *shadowConn) SetReadDeadline(t time.Time) error {
 func (c *shadowConn) SetWriteDeadline(t time.Time) error {
 	return c.conn.SetWriteDeadline(t)
 }
+
+type ShadowUdpServer struct {
+	Base *ProxyServer
+	TTL  int
+}
+
+func NewShadowUdpServer(base *ProxyServer, ttl int) *ShadowUdpServer {
+	return &ShadowUdpServer{Base: base, TTL: ttl}
+}
+
+func (s *ShadowUdpServer) ListenAndServe() error {
+	laddr, err := net.ResolveUDPAddr("udp", s.Base.Node.Addr)
+	if err != nil {
+		return err
+	}
+	lconn, err := net.ListenUDP("udp", laddr)
+	if err != nil {
+		return err
+	}
+	defer lconn.Close()
+
+	conn := ss.NewSecurePacketConn(lconn, s.Base.cipher.Copy(), true) // force OTA on
+
+	rChan, wChan := make(chan *packet, 128), make(chan *packet, 128)
+	// start send queue
+	go func(ch chan<- *packet) {
+		for {
+			b := make([]byte, MediumBufferSize)
+			n, addr, err := conn.ReadFrom(b[3:]) // add rsv and frag fields to make it the standard SOCKS5 UDP datagram
+			if err != nil {
+				glog.V(LWARNING).Infof("[ssu] %s -> %s : %s", addr, laddr, err)
+				continue
+			}
+
+			if b[3]&ss.OneTimeAuthMask > 0 {
+				glog.V(LWARNING).Infof("[ssu] %s -> %s : client does not support OTA", addr, laddr)
+				continue
+			}
+			b[3] &= ss.AddrMask
+
+			dgram, err := gosocks5.ReadUDPDatagram(bytes.NewReader(b[:n+3]))
+			if err != nil {
+				glog.V(LWARNING).Infof("[ssu] %s -> %s : %s", addr, laddr, err)
+				continue
+			}
+
+			select {
+			case ch <- &packet{srcAddr: addr.String(), dstAddr: dgram.Header.Addr.String(), data: b[:n+3]}:
+			case <-time.After(time.Second * 3):
+				glog.V(LWARNING).Infof("[ssu] %s -> %s : %s", addr, dgram.Header.Addr.String(), "send queue is full, discard")
+			}
+		}
+	}(wChan)
+	// start recv queue
+	go func(ch <-chan *packet) {
+		for pkt := range ch {
+			dstAddr, err := net.ResolveUDPAddr("udp", pkt.dstAddr)
+			if err != nil {
+				glog.V(LWARNING).Infof("[ssu] %s <- %s : %s", pkt.dstAddr, pkt.srcAddr, err)
+				continue
+			}
+			if _, err := conn.WriteTo(pkt.data, dstAddr); err != nil {
+				glog.V(LWARNING).Infof("[ssu] %s <- %s : %s", pkt.dstAddr, pkt.srcAddr, err)
+				return
+			}
+		}
+	}(rChan)
+
+	// mapping client to node
+	m := make(map[string]*cnode)
+
+	// start dispatcher
+	for pkt := range wChan {
+		// clear obsolete nodes
+		for k, node := range m {
+			if node != nil && node.err != nil {
+				close(node.wChan)
+				delete(m, k)
+				glog.V(LINFO).Infof("[ssu] clear node %s", k)
+			}
+		}
+
+		node, ok := m[pkt.srcAddr]
+		if !ok {
+			node = &cnode{
+				chain:   s.Base.Chain,
+				srcAddr: pkt.srcAddr,
+				dstAddr: pkt.dstAddr,
+				rChan:   rChan,
+				wChan:   make(chan *packet, 32),
+				ttl:     time.Duration(s.TTL) * time.Second,
+			}
+			m[pkt.srcAddr] = node
+			go node.run()
+			glog.V(LINFO).Infof("[ssu] %s -> %s : new client (%d)", pkt.srcAddr, pkt.dstAddr, len(m))
+		}
+
+		select {
+		case node.wChan <- pkt:
+		case <-time.After(time.Second * 3):
+			glog.V(LWARNING).Infof("[ssu] %s -> %s : %s", pkt.srcAddr, pkt.dstAddr, "node send queue is full, discard")
+		}
+	}
+
+	return nil
+}

cmd/gost/vendor/github.com/shadowsocks/shadowsocks-go/shadowsocks/encrypt.go

@@ -12,7 +12,7 @@ import (
 	"io"
 	"strings"
 
-	"github.com/codahale/chacha20"
+	"github.com/Yawning/chacha20"
 	"golang.org/x/crypto/blowfish"
 	"golang.org/x/crypto/cast5"
 	"golang.org/x/crypto/salsa20/salsa"
@@ -65,11 +65,19 @@ func newStream(block cipher.Block, err error, key, iv []byte,
 	}
 }
 
-func newAESStream(key, iv []byte, doe DecOrEnc) (cipher.Stream, error) {
+func newAESCFBStream(key, iv []byte, doe DecOrEnc) (cipher.Stream, error) {
 	block, err := aes.NewCipher(key)
 	return newStream(block, err, key, iv, doe)
 }
 
+func newAESCTRStream(key, iv []byte, doe DecOrEnc) (cipher.Stream, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	return cipher.NewCTR(block, iv), nil
+}
+
 func newDESStream(key, iv []byte, doe DecOrEnc) (cipher.Stream, error) {
 	block, err := des.NewCipher(key)
 	return newStream(block, err, key, iv, doe)
@@ -95,7 +103,11 @@ func newRC4MD5Stream(key, iv []byte, _ DecOrEnc) (cipher.Stream, error) {
 }
 
 func newChaCha20Stream(key, iv []byte, _ DecOrEnc) (cipher.Stream, error) {
-	return chacha20.New(key, iv)
+	return chacha20.NewCipher(key, iv)
+}
+
+func newChaCha20IETFStream(key, iv []byte, _ DecOrEnc) (cipher.Stream, error) {
+	return chacha20.NewCipher(key, iv)
 }
 
 type salsaStreamCipher struct {
@@ -145,15 +157,19 @@ type cipherInfo struct {
 }
 
 var cipherMethod = map[string]*cipherInfo{
-	"aes-128-cfb": {16, 16, newAESStream},
+	"aes-128-cfb":   {16, 16, newAESCFBStream},
-	"aes-192-cfb": {24, 16, newAESStream},
+	"aes-192-cfb":   {24, 16, newAESCFBStream},
-	"aes-256-cfb": {32, 16, newAESStream},
+	"aes-256-cfb":   {32, 16, newAESCFBStream},
-	"des-cfb":     {8, 8, newDESStream},
+	"aes-128-ctr":   {16, 16, newAESCTRStream},
-	"bf-cfb":      {16, 8, newBlowFishStream},
+	"aes-192-ctr":   {24, 16, newAESCTRStream},
-	"cast5-cfb":   {16, 8, newCast5Stream},
+	"aes-256-ctr":   {32, 16, newAESCTRStream},
-	"rc4-md5":     {16, 16, newRC4MD5Stream},
+	"des-cfb":       {8, 8, newDESStream},
-	"chacha20":    {32, 8, newChaCha20Stream},
+	"bf-cfb":        {16, 8, newBlowFishStream},
-	"salsa20":     {32, 8, newSalsa20Stream},
+	"cast5-cfb":     {16, 8, newCast5Stream},
+	"rc4-md5":       {16, 16, newRC4MD5Stream},
+	"chacha20":      {32, 8, newChaCha20Stream},
+	"chacha20-ietf": {32, 12, newChaCha20IETFStream},
+	"salsa20":       {32, 8, newSalsa20Stream},
 }
 
 func CheckCipherMethod(method string) error {

cmd/gost/vendor/github.com/shadowsocks/shadowsocks-go/shadowsocks/udp.go

@@ -0,0 +1,135 @@
+package shadowsocks
+
+import (
+	"bytes"
+	"fmt"
+	"net"
+	"time"
+)
+
+const (
+	maxPacketSize = 4096 // increase it if error occurs
+)
+
+var (
+	errPacketTooSmall  = fmt.Errorf("[udp]read error: cannot decrypt, received packet is smaller than ivLen")
+	errPacketTooLarge  = fmt.Errorf("[udp]read error: received packet is latger than maxPacketSize(%d)", maxPacketSize)
+	errBufferTooSmall  = fmt.Errorf("[udp]read error: given buffer is too small to hold data")
+	errPacketOtaFailed = fmt.Errorf("[udp]read error: received packet has invalid ota")
+)
+
+type SecurePacketConn struct {
+	net.PacketConn
+	*Cipher
+	ota bool
+}
+
+func NewSecurePacketConn(c net.PacketConn, cipher *Cipher, ota bool) *SecurePacketConn {
+	return &SecurePacketConn{
+		PacketConn: c,
+		Cipher:     cipher,
+		ota:        ota,
+	}
+}
+
+func (c *SecurePacketConn) Close() error {
+	return c.PacketConn.Close()
+}
+
+func (c *SecurePacketConn) ReadFrom(b []byte) (n int, src net.Addr, err error) {
+	ota := false
+	cipher := c.Copy()
+	buf := make([]byte, 4096)
+	n, src, err = c.PacketConn.ReadFrom(buf)
+	if err != nil {
+		return
+	}
+
+	if n < c.info.ivLen {
+		return 0, nil, errPacketTooSmall
+	}
+
+	if len(b) < n-c.info.ivLen {
+		err = errBufferTooSmall // just a warning
+	}
+
+	iv := make([]byte, c.info.ivLen)
+	copy(iv, buf[:c.info.ivLen])
+
+	if err = cipher.initDecrypt(iv); err != nil {
+		return
+	}
+
+	cipher.decrypt(b[0:], buf[c.info.ivLen:n])
+	n -= c.info.ivLen
+	if b[idType]&OneTimeAuthMask > 0 {
+		ota = true
+	}
+
+	if c.ota && !ota {
+		return 0, src, errPacketOtaFailed
+	}
+
+	if ota {
+		key := cipher.key
+		actualHmacSha1Buf := HmacSha1(append(iv, key...), b[:n-lenHmacSha1])
+		if !bytes.Equal(b[n-lenHmacSha1:n], actualHmacSha1Buf) {
+			Debug.Printf("verify one time auth failed, iv=%v key=%v data=%v", iv, key, b)
+			return 0, src, errPacketOtaFailed
+		}
+		n -= lenHmacSha1
+	}
+
+	return
+}
+
+func (c *SecurePacketConn) WriteTo(b []byte, dst net.Addr) (n int, err error) {
+	cipher := c.Copy()
+	iv, err := cipher.initEncrypt()
+	if err != nil {
+		return
+	}
+	packetLen := len(b) + len(iv)
+
+	if c.ota {
+		b[idType] |= OneTimeAuthMask
+		packetLen += lenHmacSha1
+		key := cipher.key
+		actualHmacSha1Buf := HmacSha1(append(iv, key...), b)
+		b = append(b, actualHmacSha1Buf...)
+	}
+
+	cipherData := make([]byte, packetLen)
+	copy(cipherData, iv)
+
+	cipher.encrypt(cipherData[len(iv):], b)
+	n, err = c.PacketConn.WriteTo(cipherData, dst)
+	if c.ota {
+		n -= lenHmacSha1
+	}
+	return
+}
+
+func (c *SecurePacketConn) LocalAddr() net.Addr {
+	return c.PacketConn.LocalAddr()
+}
+
+func (c *SecurePacketConn) SetDeadline(t time.Time) error {
+	return c.PacketConn.SetDeadline(t)
+}
+
+func (c *SecurePacketConn) SetReadDeadline(t time.Time) error {
+	return c.PacketConn.SetReadDeadline(t)
+}
+
+func (c *SecurePacketConn) SetWriteDeadline(t time.Time) error {
+	return c.PacketConn.SetWriteDeadline(t)
+}
+
+func (c *SecurePacketConn) IsOta() bool {
+	return c.ota
+}
+
+func (c *SecurePacketConn) ForceOTA() net.PacketConn {
+	return NewSecurePacketConn(c.PacketConn, c.Cipher.Copy(), true)
+}

cmd/gost/vendor/github.com/shadowsocks/shadowsocks-go/shadowsocks/udprelay.go

@@ -0,0 +1,265 @@
+package shadowsocks
+
+import (
+	"encoding/binary"
+	"fmt"
+	"net"
+	"strconv"
+	"strings"
+	"sync"
+	"syscall"
+	"time"
+)
+
+const (
+	idType  = 0 // address type index
+	idIP0   = 1 // ip addres start index
+	idDmLen = 1 // domain address length index
+	idDm0   = 2 // domain address start index
+
+	typeIPv4 = 1 // type is ipv4 address
+	typeDm   = 3 // type is domain address
+	typeIPv6 = 4 // type is ipv6 address
+
+	lenIPv4     = 1 + net.IPv4len + 2 // 1addrType + ipv4 + 2port
+	lenIPv6     = 1 + net.IPv6len + 2 // 1addrType + ipv6 + 2port
+	lenDmBase   = 1 + 1 + 2           // 1addrType + 1addrLen + 2port, plus addrLen
+	lenHmacSha1 = 10
+)
+
+var (
+	reqList            = newReqList()
+	natlist            = newNatTable()
+	udpTimeout         = 30 * time.Second
+	reqListRefreshTime = 5 * time.Minute
+)
+
+type natTable struct {
+	sync.Mutex
+	conns map[string]net.PacketConn
+}
+
+func newNatTable() *natTable {
+	return &natTable{conns: map[string]net.PacketConn{}}
+}
+
+func (table *natTable) Delete(index string) net.PacketConn {
+	table.Lock()
+	defer table.Unlock()
+	c, ok := table.conns[index]
+	if ok {
+		delete(table.conns, index)
+		return c
+	}
+	return nil
+}
+
+func (table *natTable) Get(index string) (c net.PacketConn, ok bool, err error) {
+	table.Lock()
+	defer table.Unlock()
+	c, ok = table.conns[index]
+	if !ok {
+		c, err = net.ListenPacket("udp", "")
+		if err != nil {
+			return nil, false, err
+		}
+		table.conns[index] = c
+	}
+	return
+}
+
+type requestHeaderList struct {
+	sync.Mutex
+	List map[string]([]byte)
+}
+
+func newReqList() *requestHeaderList {
+	ret := &requestHeaderList{List: map[string]([]byte){}}
+	go func() {
+		for {
+			time.Sleep(reqListRefreshTime)
+			ret.Refresh()
+		}
+	}()
+	return ret
+}
+
+func (r *requestHeaderList) Refresh() {
+	r.Lock()
+	defer r.Unlock()
+	for k, _ := range r.List {
+		delete(r.List, k)
+	}
+}
+
+func (r *requestHeaderList) Get(dstaddr string) (req []byte, ok bool) {
+	r.Lock()
+	defer r.Unlock()
+	req, ok = r.List[dstaddr]
+	return
+}
+
+func (r *requestHeaderList) Put(dstaddr string, req []byte) {
+	r.Lock()
+	defer r.Unlock()
+	r.List[dstaddr] = req
+	return
+}
+
+func parseHeaderFromAddr(addr net.Addr) ([]byte, int) {
+	// if the request address type is domain, it cannot be reverselookuped
+	ip, port, err := net.SplitHostPort(addr.String())
+	if err != nil {
+		return nil, 0
+	}
+	buf := make([]byte, 20)
+	IP := net.ParseIP(ip)
+	b1 := IP.To4()
+	iplen := 0
+	if b1 == nil { //ipv6
+		b1 = IP.To16()
+		buf[0] = typeIPv6
+		iplen = net.IPv6len
+	} else { //ipv4
+		buf[0] = typeIPv4
+		iplen = net.IPv4len
+	}
+	copy(buf[1:], b1)
+	port_i, _ := strconv.Atoi(port)
+	binary.BigEndian.PutUint16(buf[1+iplen:], uint16(port_i))
+	return buf[:1+iplen+2], 1 + iplen + 2
+}
+
+func Pipeloop(write net.PacketConn, writeAddr net.Addr, readClose net.PacketConn) {
+	buf := leakyBuf.Get()
+	defer leakyBuf.Put(buf)
+	defer readClose.Close()
+	for {
+		readClose.SetDeadline(time.Now().Add(udpTimeout))
+		n, raddr, err := readClose.ReadFrom(buf)
+		if err != nil {
+			if ne, ok := err.(*net.OpError); ok {
+				if ne.Err == syscall.EMFILE || ne.Err == syscall.ENFILE {
+					// log too many open file error
+					// EMFILE is process reaches open file limits, ENFILE is system limit
+					Debug.Println("[udp]read error:", err)
+				}
+			}
+			Debug.Printf("[udp]closed pipe %s<-%s\n", writeAddr, readClose.LocalAddr())
+			return
+		}
+		// need improvement here
+		if req, ok := reqList.Get(raddr.String()); ok {
+			write.WriteTo(append(req, buf[:n]...), writeAddr)
+		} else {
+			header, hlen := parseHeaderFromAddr(raddr)
+			write.WriteTo(append(header[:hlen], buf[:n]...), writeAddr)
+		}
+	}
+}
+
+func handleUDPConnection(handle *SecurePacketConn, n int, src net.Addr, receive []byte) {
+	var dstIP net.IP
+	var reqLen int
+	var ota bool
+	addrType := receive[idType]
+	defer leakyBuf.Put(receive)
+
+	if addrType&OneTimeAuthMask > 0 {
+		ota = true
+	}
+	receive[idType] &= ^OneTimeAuthMask
+	compatiblemode := !handle.IsOta() && ota
+
+	switch addrType & AddrMask {
+	case typeIPv4:
+		reqLen = lenIPv4
+		if len(receive) < reqLen {
+			Debug.Println("[udp]invalid received message.")
+		}
+		dstIP = net.IP(receive[idIP0 : idIP0+net.IPv4len])
+	case typeIPv6:
+		reqLen = lenIPv6
+		if len(receive) < reqLen {
+			Debug.Println("[udp]invalid received message.")
+		}
+		dstIP = net.IP(receive[idIP0 : idIP0+net.IPv6len])
+	case typeDm:
+		reqLen = int(receive[idDmLen]) + lenDmBase
+		if len(receive) < reqLen {
+			Debug.Println("[udp]invalid received message.")
+		}
+		name := string(receive[idDm0 : idDm0+int(receive[idDmLen])])
+		// avoid panic: syscall: string with NUL passed to StringToUTF16 on windows.
+		if strings.ContainsRune(name, 0x00) {
+			fmt.Println("[udp]invalid domain name.")
+			return
+		}
+		dIP, err := net.ResolveIPAddr("ip", name) // carefully with const type
+		if err != nil {
+			Debug.Printf("[udp]failed to resolve domain name: %s\n", string(receive[idDm0:idDm0+receive[idDmLen]]))
+			return
+		}
+		dstIP = dIP.IP
+	default:
+		Debug.Printf("[udp]addrType %d not supported", addrType)
+		return
+	}
+	dst := &net.UDPAddr{
+		IP:   dstIP,
+		Port: int(binary.BigEndian.Uint16(receive[reqLen-2 : reqLen])),
+	}
+	if _, ok := reqList.Get(dst.String()); !ok {
+		req := make([]byte, reqLen)
+		copy(req, receive)
+		reqList.Put(dst.String(), req)
+	}
+
+	remote, exist, err := natlist.Get(src.String())
+	if err != nil {
+		return
+	}
+	if !exist {
+		Debug.Printf("[udp]new client %s->%s via %s ota=%v\n", src, dst, remote.LocalAddr(), ota)
+		go func() {
+			if compatiblemode {
+				Pipeloop(handle.ForceOTA(), src, remote)
+			} else {
+				Pipeloop(handle, src, remote)
+			}
+
+			natlist.Delete(src.String())
+		}()
+	} else {
+		Debug.Printf("[udp]using cached client %s->%s via %s ota=%v\n", src, dst, remote.LocalAddr(), ota)
+	}
+	if remote == nil {
+		fmt.Println("WTF")
+	}
+	remote.SetDeadline(time.Now().Add(udpTimeout))
+	_, err = remote.WriteTo(receive[reqLen:n], dst)
+	if err != nil {
+		if ne, ok := err.(*net.OpError); ok && (ne.Err == syscall.EMFILE || ne.Err == syscall.ENFILE) {
+			// log too many open file error
+			// EMFILE is process reaches open file limits, ENFILE is system limit
+			Debug.Println("[udp]write error:", err)
+		} else {
+			Debug.Println("[udp]error connecting to:", dst, err)
+		}
+		if conn := natlist.Delete(src.String()); conn != nil {
+			conn.Close()
+		}
+	}
+	// Pipeloop
+	return
+}
+
+func ReadAndHandleUDPReq(c *SecurePacketConn) error {
+	buf := leakyBuf.Get()
+	n, src, err := c.ReadFrom(buf[0:])
+	if err != nil {
+		return err
+	}
+	go handleUDPConnection(c, n, src, buf)
+	return nil
+}

cmd/gost/vendor/github.com/shadowsocks/shadowsocks-go/shadowsocks/util.go

@@ -1,16 +1,16 @@
 package shadowsocks
 
 import (
-	"errors"
-	"fmt"
-	"os"
 	"crypto/hmac"
 	"crypto/sha1"
 	"encoding/binary"
+	"errors"
+	"fmt"
+	"os"
 )
 
 func PrintVersion() {
-	const version = "1.1.5"
+	const version = "1.2.0"
 	fmt.Println("shadowsocks-go version", version)
 }
 

cmd/gost/vendor/vendor.json

@@ -2,6 +2,12 @@
 	"comment": "",
 	"ignore": "test",
 	"package": [
+		{
+			"checksumSHA1": "IFJyJgPCjumDG37lEb0lyRBBGZE=",
+			"path": "github.com/Yawning/chacha20",
+			"revision": "c91e78db502ff629614837aacb7aa4efa61c651a",
+			"revisionTime": "2016-04-30T09:49:23Z"
+		},
 		{
 			"checksumSHA1": "QPs3L3mjPoi+a9GJCjW8HhyJczM=",
 			"path": "github.com/codahale/chacha20",
@@ -15,10 +21,10 @@
 			"revisionTime": "2017-01-19T05:34:58Z"
 		},
 		{
-			"checksumSHA1": "b0uHAM/lCGCJ9GeKfClvrMMWXQM=",
+			"checksumSHA1": "idpL1fpHpfntk74IVfWtkP1PMZs=",
 			"path": "github.com/ginuerzh/gost",
-			"revision": "358f57add6087d77b1d978e92e2f7c8073c2f544",
+			"revision": "321b03712af504981d35a47c50c2cfe4dd788a9d",
-			"revisionTime": "2017-01-21T03:14:59Z"
+			"revisionTime": "2017-01-21T03:16:33Z"
 		},
 		{
 			"checksumSHA1": "URsJa4y/sUUw/STmbeYx9EKqaYE=",
@@ -153,10 +159,10 @@
 			"revisionTime": "2016-10-02T05:25:12Z"
 		},
 		{
-			"checksumSHA1": "o0WHRL8mNIhfsoWlzhdJ8du6+C8=",
+			"checksumSHA1": "MRsfMrdZwnnCTfIzT3czcj0lb0s=",
 			"path": "github.com/shadowsocks/shadowsocks-go/shadowsocks",
-			"revision": "5c9897ecdf623f385ccb8c2c78e32c5256961b41",
+			"revision": "97a5c71f80ba5f5b3e549f14a619fe557ff4f3c9",
-			"revisionTime": "2016-06-15T15:25:08Z"
+			"revisionTime": "2017-01-21T20:35:16Z"
 		},
 		{
 			"checksumSHA1": "JsJdKXhz87gWenMwBeejTOeNE7k=",

forward.go

@@ -63,15 +63,15 @@ func (s *TcpForwardServer) handleTcpForward(conn net.Conn, raddr net.Addr) {
 }
 
 type packet struct {
-	srcAddr *net.UDPAddr // src address
+	srcAddr string // src address
-	dstAddr *net.UDPAddr // dest address
+	dstAddr string // dest address
 	data    []byte
 }
 
 type cnode struct {
 	chain            *ProxyChain
 	conn             net.Conn
-	srcAddr, dstAddr *net.UDPAddr
+	srcAddr, dstAddr string
 	rChan, wChan     chan *packet
 	err              error
 	ttl              time.Duration
@@ -146,13 +146,9 @@ func (node *cnode) run() {
 				timer.Reset(node.ttl)
 				glog.V(LDEBUG).Infof("[udp] %s <<< %s : length %d", node.srcAddr, addr, n)
 
-				if node.dstAddr.String() != addr.String() {
-					glog.V(LWARNING).Infof("[udp] %s <- %s : dst-addr mismatch (%s)", node.srcAddr, node.dstAddr, addr)
-					break
-				}
 				select {
 				// swap srcAddr with dstAddr
-				case node.rChan <- &packet{srcAddr: node.dstAddr, dstAddr: node.srcAddr, data: b[:n]}:
+				case node.rChan <- &packet{srcAddr: addr.String(), dstAddr: node.srcAddr, data: b[:n]}:
 				case <-time.After(time.Second * 3):
 					glog.V(LWARNING).Infof("[udp] %s <- %s : %s", node.srcAddr, node.dstAddr, "recv queue is full, discard")
 				}
@@ -169,13 +165,9 @@ func (node *cnode) run() {
 				timer.Reset(node.ttl)
 				glog.V(LDEBUG).Infof("[udp-tun] %s <<< %s : length %d", node.srcAddr, dgram.Header.Addr.String(), len(dgram.Data))
 
-				if dgram.Header.Addr.String() != node.dstAddr.String() {
-					glog.V(LWARNING).Infof("[udp-tun] %s <- %s : dst-addr mismatch (%s)", node.srcAddr, node.dstAddr, dgram.Header.Addr)
-					break
-				}
 				select {
 				// swap srcAddr with dstAddr
-				case node.rChan <- &packet{srcAddr: node.dstAddr, dstAddr: node.srcAddr, data: dgram.Data}:
+				case node.rChan <- &packet{srcAddr: dgram.Header.Addr.String(), dstAddr: node.srcAddr, data: dgram.Data}:
 				case <-time.After(time.Second * 3):
 					glog.V(LWARNING).Infof("[udp-tun] %s <- %s : %s", node.srcAddr, node.dstAddr, "recv queue is full, discard")
 				}
@@ -187,9 +179,15 @@ func (node *cnode) run() {
 		for pkt := range node.wChan {
 			timer.Reset(node.ttl)
 
+			dstAddr, err := net.ResolveUDPAddr("udp", pkt.dstAddr)
+			if err != nil {
+				glog.V(LWARNING).Infof("[udp] %s -> %s : %s", pkt.srcAddr, pkt.dstAddr, err)
+				continue
+			}
+
 			switch c := node.conn.(type) {
 			case *net.UDPConn:
-				if _, err := c.WriteToUDP(pkt.data, pkt.dstAddr); err != nil {
+				if _, err := c.WriteToUDP(pkt.data, dstAddr); err != nil {
 					glog.V(LWARNING).Infof("[udp] %s -> %s : %s", pkt.srcAddr, pkt.dstAddr, err)
 					node.err = err
 					errChan <- err
@@ -198,7 +196,7 @@ func (node *cnode) run() {
 				glog.V(LDEBUG).Infof("[udp] %s >>> %s : length %d", pkt.srcAddr, pkt.dstAddr, len(pkt.data))
 
 			default:
-				dgram := gosocks5.NewUDPDatagram(gosocks5.NewUDPHeader(uint16(len(pkt.data)), 0, ToSocksAddr(pkt.dstAddr)), pkt.data)
+				dgram := gosocks5.NewUDPDatagram(gosocks5.NewUDPHeader(uint16(len(pkt.data)), 0, ToSocksAddr(dstAddr)), pkt.data)
 				if err := dgram.Write(c); err != nil {
 					glog.V(LWARNING).Infof("[udp-tun] %s -> %s : %s", pkt.srcAddr, pkt.dstAddr, err)
 					node.err = err
@@ -255,7 +253,7 @@ func (s *UdpForwardServer) ListenAndServe() error {
 			}
 
 			select {
-			case ch <- &packet{srcAddr: addr, dstAddr: raddr, data: b[:n]}:
+			case ch <- &packet{srcAddr: addr.String(), dstAddr: raddr.String(), data: b[:n]}:
 			case <-time.After(time.Second * 3):
 				glog.V(LWARNING).Infof("[udp] %s -> %s : %s", addr, raddr, "send queue is full, discard")
 			}
@@ -264,7 +262,12 @@ func (s *UdpForwardServer) ListenAndServe() error {
 	// start recv queue
 	go func(ch <-chan *packet) {
 		for pkt := range ch {
-			if _, err := conn.WriteToUDP(pkt.data, pkt.dstAddr); err != nil {
+			dstAddr, err := net.ResolveUDPAddr("udp", pkt.dstAddr)
+			if err != nil {
+				glog.V(LWARNING).Infof("[udp] %s <- %s : %s", pkt.dstAddr, pkt.srcAddr, err)
+				continue
+			}
+			if _, err := conn.WriteToUDP(pkt.data, dstAddr); err != nil {
 				glog.V(LWARNING).Infof("[udp] %s <- %s : %s", pkt.dstAddr, pkt.srcAddr, err)
 				return
 			}
@@ -285,7 +288,7 @@ func (s *UdpForwardServer) ListenAndServe() error {
 			}
 		}
 
-		node, ok := m[pkt.srcAddr.String()]
+		node, ok := m[pkt.srcAddr]
 		if !ok {
 			node = &cnode{
 				chain:   s.Base.Chain,
@@ -295,7 +298,7 @@ func (s *UdpForwardServer) ListenAndServe() error {
 				wChan:   make(chan *packet, 32),
 				ttl:     time.Duration(s.TTL) * time.Second,
 			}
-			m[pkt.srcAddr.String()] = node
+			m[pkt.srcAddr] = node
 			go node.run()
 			glog.V(LINFO).Infof("[udp] %s -> %s : new client (%d)", pkt.srcAddr, pkt.dstAddr, len(m))
 		}

gost.go

@@ -11,7 +11,7 @@ import (
 )
 
 const (
-	Version = "2.3"
+	Version = "2.4-dev"
 )
 
 // Log level for glog

node.go

@@ -71,7 +71,7 @@ func ParseProxyNode(s string) (node ProxyNode, err error) {
 	}
 
 	switch node.Transport {
-	case "ws", "wss", "tls", "http2", "ssu", "quic", "kcp", "redirect":
+	case "ws", "wss", "tls", "http2", "quic", "kcp", "redirect", "ssu":
 	case "https":
 		node.Protocol = "http"
 		node.Transport = "tls"

server.go

@@ -32,7 +32,7 @@ func NewProxyServer(node ProxyNode, chain *ProxyChain, config *tls.Config) *Prox
 
 	var cipher *ss.Cipher
 	var ota bool
-	if node.Protocol == "ss" {
+	if node.Protocol == "ss" || node.Transport == "ssu" {
 		var err error
 		var method, password string
 
@@ -98,8 +98,6 @@ func (s *ProxyServer) Serve() error {
 		return NewRTcpForwardServer(s).Serve()
 	case "rudp": // Remote UDP port forwarding
 		return NewRUdpForwardServer(s).Serve()
-	case "ssu": // TODO: shadowsocks udp relay
-		return NewShadowUdpServer(s).ListenAndServe()
 	case "quic":
 		return NewQuicServer(s).ListenAndServeTLS(s.TLSConfig)
 	case "kcp":
@@ -118,6 +116,12 @@ func (s *ProxyServer) Serve() error {
 		return NewKCPServer(s, config).ListenAndServe()
 	case "redirect":
 		return NewRedsocksTCPServer(s).ListenAndServe()
+	case "ssu": // shadowsocks udp relay
+		ttl, _ := strconv.Atoi(s.Node.Get("ttl"))
+		if ttl <= 0 {
+			ttl = DefaultTTL
+		}
+		return NewShadowUdpServer(s, ttl).ListenAndServe()
 	default:
 		ln, err = net.Listen("tcp", node.Addr)
 	}

ss.go

@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"github.com/ginuerzh/gosocks5"
 	"github.com/golang/glog"
 	ss "github.com/shadowsocks/shadowsocks-go/shadowsocks"
 	"io"
@@ -65,47 +66,6 @@ func (s *ShadowServer) Serve() {
 	glog.V(LINFO).Infof("[ss] %s >-< %s", s.conn.RemoteAddr(), addr)
 }
 
-type ShadowUdpServer struct {
-	Base    *ProxyServer
-	Handler func(conn *net.UDPConn, addr *net.UDPAddr, data []byte)
-}
-
-func NewShadowUdpServer(base *ProxyServer) *ShadowUdpServer {
-	return &ShadowUdpServer{Base: base}
-}
-
-func (s *ShadowUdpServer) ListenAndServe() error {
-	laddr, err := net.ResolveUDPAddr("udp", s.Base.Node.Addr)
-	if err != nil {
-		return err
-	}
-	lconn, err := net.ListenUDP("udp", laddr)
-	if err != nil {
-		return err
-	}
-	defer lconn.Close()
-
-	if s.Handler == nil {
-		s.Handler = s.HandleConn
-	}
-
-	for {
-		b := make([]byte, LargeBufferSize)
-		n, addr, err := lconn.ReadFromUDP(b)
-		if err != nil {
-			glog.V(LWARNING).Infoln(err)
-			continue
-		}
-
-		go s.Handler(lconn, addr, b[:n])
-	}
-}
-
-// TODO: shadowsocks udp relay handler
-func (s *ShadowUdpServer) HandleConn(conn *net.UDPConn, addr *net.UDPAddr, data []byte) {
-
-}
-
 // This function is copied from shadowsocks library with some modification.
 func (s *ShadowServer) getRequest() (host string, ota bool, err error) {
 	// buf size should at least have the same size with the largest possible
@@ -276,3 +236,109 @@ func (c *shadowConn) SetReadDeadline(t time.Time) error {
 func (c *shadowConn) SetWriteDeadline(t time.Time) error {
 	return c.conn.SetWriteDeadline(t)
 }
+
+type ShadowUdpServer struct {
+	Base *ProxyServer
+	TTL  int
+}
+
+func NewShadowUdpServer(base *ProxyServer, ttl int) *ShadowUdpServer {
+	return &ShadowUdpServer{Base: base, TTL: ttl}
+}
+
+func (s *ShadowUdpServer) ListenAndServe() error {
+	laddr, err := net.ResolveUDPAddr("udp", s.Base.Node.Addr)
+	if err != nil {
+		return err
+	}
+	lconn, err := net.ListenUDP("udp", laddr)
+	if err != nil {
+		return err
+	}
+	defer lconn.Close()
+
+	conn := ss.NewSecurePacketConn(lconn, s.Base.cipher.Copy(), true) // force OTA on
+
+	rChan, wChan := make(chan *packet, 128), make(chan *packet, 128)
+	// start send queue
+	go func(ch chan<- *packet) {
+		for {
+			b := make([]byte, MediumBufferSize)
+			n, addr, err := conn.ReadFrom(b[3:]) // add rsv and frag fields to make it the standard SOCKS5 UDP datagram
+			if err != nil {
+				glog.V(LWARNING).Infof("[ssu] %s -> %s : %s", addr, laddr, err)
+				continue
+			}
+
+			if b[3]&ss.OneTimeAuthMask > 0 {
+				glog.V(LWARNING).Infof("[ssu] %s -> %s : client does not support OTA", addr, laddr)
+				continue
+			}
+			b[3] &= ss.AddrMask
+
+			dgram, err := gosocks5.ReadUDPDatagram(bytes.NewReader(b[:n+3]))
+			if err != nil {
+				glog.V(LWARNING).Infof("[ssu] %s -> %s : %s", addr, laddr, err)
+				continue
+			}
+
+			select {
+			case ch <- &packet{srcAddr: addr.String(), dstAddr: dgram.Header.Addr.String(), data: b[:n+3]}:
+			case <-time.After(time.Second * 3):
+				glog.V(LWARNING).Infof("[ssu] %s -> %s : %s", addr, dgram.Header.Addr.String(), "send queue is full, discard")
+			}
+		}
+	}(wChan)
+	// start recv queue
+	go func(ch <-chan *packet) {
+		for pkt := range ch {
+			dstAddr, err := net.ResolveUDPAddr("udp", pkt.dstAddr)
+			if err != nil {
+				glog.V(LWARNING).Infof("[ssu] %s <- %s : %s", pkt.dstAddr, pkt.srcAddr, err)
+				continue
+			}
+			if _, err := conn.WriteTo(pkt.data, dstAddr); err != nil {
+				glog.V(LWARNING).Infof("[ssu] %s <- %s : %s", pkt.dstAddr, pkt.srcAddr, err)
+				return
+			}
+		}
+	}(rChan)
+
+	// mapping client to node
+	m := make(map[string]*cnode)
+
+	// start dispatcher
+	for pkt := range wChan {
+		// clear obsolete nodes
+		for k, node := range m {
+			if node != nil && node.err != nil {
+				close(node.wChan)
+				delete(m, k)
+				glog.V(LINFO).Infof("[ssu] clear node %s", k)
+			}
+		}
+
+		node, ok := m[pkt.srcAddr]
+		if !ok {
+			node = &cnode{
+				chain:   s.Base.Chain,
+				srcAddr: pkt.srcAddr,
+				dstAddr: pkt.dstAddr,
+				rChan:   rChan,
+				wChan:   make(chan *packet, 32),
+				ttl:     time.Duration(s.TTL) * time.Second,
+			}
+			m[pkt.srcAddr] = node
+			go node.run()
+			glog.V(LINFO).Infof("[ssu] %s -> %s : new client (%d)", pkt.srcAddr, pkt.dstAddr, len(m))
+		}
+
+		select {
+		case node.wChan <- pkt:
+		case <-time.After(time.Second * 3):
+			glog.V(LWARNING).Infof("[ssu] %s -> %s : %s", pkt.srcAddr, pkt.dstAddr, "node send queue is full, discard")
+		}
+	}
+
+	return nil
+}