feat: Add rate limiting to fallback handling via token bucket

README.en.md

@@ -45,7 +45,12 @@ TODO List: TODO
                     "shortIds": [ // Required, the acceptable shortId list, which can be used to distinguish different clients
                         "", // If there is this item, the client shortId can be empty
                         "0123456789abcdef" // 0 to f, the length is a multiple of 2, the maximum length is 16
-                    ]
+                    ],
+                    // The following four Limits are optional and limit the rate of falling REALITY connections in bytes/second. Default is 0, i.e. not enabled
+                    "limitUploadRate": 0, // Uplink base rate
+                    "limitUploadBrust": 0, // Uplink burst rate
+                    "limitDownloadRate": 0, // Downlink base rate
+                    "limitDownloadBrust": 0 // Downlink burst rate
                 }
             }
         }

README.md

@@ -45,7 +45,12 @@ TODO List: TODO
                     "shortIds": [ // 必填，客户端可用的 shortId 列表，可用于区分不同的客户端
                         "", // 若有此项，客户端 shortId 可为空
                         "0123456789abcdef" // 0 到 f，长度为 2 的倍数，长度上限为 16
-                    ]
+                    ],
+                    // 下列四个 Limit 为选填，可对回落的 REALITY 连接限速，单位是字节/秒。默认为 0 即不启用
+                    "limitUploadRate": 0, // 上行基准速率
+                    "limitUploadBrust": 0, // 上行突发速率
+                    "limitDownloadRate": 0, // 下行基准速率
+                    "limitDownloadBrust": 0 // 下行突发速率
                 }
             }
         }

common.go

@@ -556,6 +556,11 @@ type Config struct {
 	MaxTimeDiff  time.Duration
 	ShortIds     map[[8]byte]bool
 
+	LimitUploadRate    float64
+	LimitUploadBrust   int64
+	LimitDownloadRate  float64
+	LimitDownloadBrust int64
+
 	// Rand provides the source of entropy for nonces and RSA blinding.
 	// If Rand is nil, TLS uses the cryptographic random reader in package
 	// crypto/rand.
@@ -971,6 +976,10 @@ func (c *Config) Clone() *Config {
 		MaxClientVer:                        c.MaxClientVer,
 		MaxTimeDiff:                         c.MaxTimeDiff,
 		ShortIds:                            c.ShortIds,
+		LimitUploadRate:                     c.LimitUploadRate,
+		LimitUploadBrust:                    c.LimitUploadBrust,
+		LimitDownloadRate:                   c.LimitDownloadRate,
+		LimitDownloadBrust:                  c.LimitDownloadBrust,
 		Rand:                                c.Rand,
 		Time:                                c.Time,
 		Certificates:                        c.Certificates,

go.mod

@@ -3,6 +3,7 @@ module github.com/xtls/reality
 go 1.24
 
 require (
+	github.com/juju/ratelimit v1.0.2
 	github.com/pires/go-proxyproto v0.8.1
 	github.com/refraction-networking/utls v1.7.3
 	golang.org/x/crypto v0.39.0

go.sum

@@ -1,3 +1,5 @@
+github.com/juju/ratelimit v1.0.2 h1:sRxmtRiajbvrcLQT7S+JbqU0ntsb9W2yhSdNN8tWfaI=
+github.com/juju/ratelimit v1.0.2/go.mod h1:qapgC/Gy+xNh9UxzV13HGGl/6UXNN+ct+vwSgWNm/qk=
 github.com/pires/go-proxyproto v0.8.1 h1:9KEixbdJfhrbtjpz/ZwCdWDD2Xem0NZ38qMYaASJgp0=
 github.com/pires/go-proxyproto v0.8.1/go.mod h1:ZKAAyp3cgy5Y5Mo4n9AlScrkCZwUy0g3Jf+slqQVcuU=
 github.com/refraction-networking/utls v1.7.3 h1:L0WRhHY7Oq1T0zkdzVZMR6zWZv+sXbHB9zcuvsAEqCo=

tls.go

@@ -50,6 +50,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/juju/ratelimit"
 	"github.com/pires/go-proxyproto"
 	"golang.org/x/crypto/curve25519"
 	"golang.org/x/crypto/hkdf"
@@ -100,6 +101,19 @@ func (c *MirrorConn) SetWriteDeadline(t time.Time) error {
 	return nil
 }
 
+type RatelimitedConn struct {
+	net.Conn
+	Bucket *ratelimit.Bucket
+}
+
+func (c *RatelimitedConn) Read(b []byte) (int, error) {
+	n, err := c.Conn.Read(b)
+	if n != 0 {
+		c.Bucket.Wait(int64(n))
+	}
+	return n, err
+}
+
 var (
 	size  = 8192
 	empty = make([]byte, size)
@@ -228,7 +242,15 @@ func Server(ctx context.Context, conn net.Conn, config *Config) (*Conn, error) {
 			if config.Show && hs.clientHello != nil {
 				fmt.Printf("REALITY remoteAddr: %v\tforwarded SNI: %v\n", remoteAddr, hs.clientHello.serverName)
 			}
+			if config.LimitUploadRate == 0 || config.LimitUploadBrust == 0 {
 				io.Copy(target, underlying)
+			} else {
+				// Limit upload speed for fallback connection
+				io.Copy(target, &RatelimitedConn{
+					Conn:   underlying,
+					Bucket: ratelimit.NewBucketWithRate(config.LimitUploadRate, config.LimitUploadBrust),
+				})
+			}
 		}
 		waitGroup.Done()
 	}()
@@ -359,12 +381,28 @@ func Server(ctx context.Context, conn net.Conn, config *Config) (*Conn, error) {
 			if hs.c.conn == conn { // if we processed the Client Hello successfully but the target did not
 				waitGroup.Add(1)
 				go func() {
+					if config.LimitUploadRate == 0 || config.LimitUploadBrust == 0 {
 						io.Copy(target, underlying)
+					} else {
+						// Limit upload speed for fallback connection (handshake ok but hello failed)
+						io.Copy(target, &RatelimitedConn{
+							Conn:   underlying,
+							Bucket: ratelimit.NewBucketWithRate(config.LimitUploadRate, config.LimitUploadBrust),
+						})
+					}
 					waitGroup.Done()
 				}()
 			}
 			conn.Write(s2cSaved)
+			if config.LimitDownloadRate == 0 || config.LimitDownloadBrust == 0 {
 				io.Copy(underlying, target)
+			} else {
+				// Limit download speed for fallback connection
+				io.Copy(underlying, &RatelimitedConn{
+					Conn:   target,
+					Bucket: ratelimit.NewBucketWithRate(config.LimitDownloadRate, config.LimitDownloadBrust),
+				})
+			}
 			// Here is bidirectional direct forwarding:
 			// client ---underlying--- server ---target--- dest
 			// Call `underlying.CloseWrite()` once `io.Copy()` returned