From b25f90c55e98fa997022db9c5eacaef53a4640ae Mon Sep 17 00:00:00 2001
From: ginuerzh <ginuerzh@gmail.com>
Date: Thu, 21 Apr 2022 21:40:08 +0800
Subject: [PATCH] add limiter

---
 limiter/rate.go             |  12 ++++
 limiter/wrapper/conn.go     | 130 ++++++++++++++++++++++++++++++++++++
 limiter/wrapper/listener.go |  32 +++++++++
 listener/option.go          |  24 ++++---
 4 files changed, 190 insertions(+), 8 deletions(-)
 create mode 100644 limiter/rate.go
 create mode 100644 limiter/wrapper/conn.go
 create mode 100644 limiter/wrapper/listener.go

diff --git a/limiter/rate.go b/limiter/rate.go
new file mode 100644
index 0000000..1edd939
--- /dev/null
+++ b/limiter/rate.go
@@ -0,0 +1,12 @@
+package limiter
+
+type Limiter interface {
+	// Limit checks the requested size b and returns the limit size,
+	// the returned value is less or equal to b.
+	Limit(b int) int
+}
+
+type RateLimiter interface {
+	Input() Limiter
+	Output() Limiter
+}
diff --git a/limiter/wrapper/conn.go b/limiter/wrapper/conn.go
new file mode 100644
index 0000000..29d044c
--- /dev/null
+++ b/limiter/wrapper/conn.go
@@ -0,0 +1,130 @@
+package wrapper
+
+import (
+	"bytes"
+	"errors"
+	"net"
+	"syscall"
+
+	"github.com/go-gost/core/limiter"
+)
+
+var (
+	errUnsupport = errors.New("unsupported operation")
+)
+
+// serverConn is a server side Conn with metrics supported.
+type serverConn struct {
+	net.Conn
+	rlimiter limiter.RateLimiter
+	rbuf     bytes.Buffer
+}
+
+func WrapConn(rlimiter limiter.RateLimiter, c net.Conn) net.Conn {
+	if rlimiter == nil {
+		return c
+	}
+	return &serverConn{
+		Conn:     c,
+		rlimiter: rlimiter,
+	}
+}
+
+func (c *serverConn) Read(b []byte) (n int, err error) {
+	if c.rlimiter == nil || c.rlimiter.Input() == nil {
+		return c.Conn.Read(b)
+	}
+
+	burst := len(b)
+	if c.rbuf.Len() > 0 {
+		if c.rbuf.Len() < burst {
+			burst = c.rbuf.Len()
+		}
+		return c.rbuf.Read(b[:c.rlimiter.Input().Limit(burst)])
+	}
+
+	nn, err := c.Conn.Read(b)
+	if err != nil {
+		return nn, err
+	}
+
+	n = c.rlimiter.Input().Limit(nn)
+	if n < nn {
+		if _, err = c.rbuf.Write(b[n:nn]); err != nil {
+			return 0, err
+		}
+	}
+
+	return
+}
+
+func (c *serverConn) Write(b []byte) (n int, err error) {
+	if c.rlimiter == nil || c.rlimiter.Output() == nil {
+		return c.Conn.Write(b)
+	}
+
+	nn := 0
+	for len(b) > 0 {
+		nn, err = c.Conn.Write(b[:c.rlimiter.Output().Limit(len(b))])
+		n += nn
+		if err != nil {
+			return
+		}
+		b = b[nn:]
+	}
+
+	return
+}
+
+func (c *serverConn) SyscallConn() (rc syscall.RawConn, err error) {
+	if sc, ok := c.Conn.(syscall.Conn); ok {
+		rc, err = sc.SyscallConn()
+		return
+	}
+	err = errUnsupport
+	return
+}
+
+type packetConn struct {
+	net.PacketConn
+	rlimiter limiter.RateLimiter
+}
+
+func WrapPacketConn(rlimiter limiter.RateLimiter, pc net.PacketConn) net.PacketConn {
+	if rlimiter == nil {
+		return pc
+	}
+	return &packetConn{
+		PacketConn: pc,
+		rlimiter:   rlimiter,
+	}
+}
+
+func (c *packetConn) ReadFrom(p []byte) (n int, addr net.Addr, err error) {
+	for {
+		n, addr, err = c.PacketConn.ReadFrom(p)
+		if err != nil {
+			return
+		}
+		if c.rlimiter == nil || c.rlimiter.Input() == nil {
+			return
+		}
+
+		if c.rlimiter.Input().Limit(n) < n {
+			continue
+		}
+
+		return
+	}
+}
+
+func (c *packetConn) WriteTo(p []byte, addr net.Addr) (n int, err error) {
+	if c.rlimiter != nil &&
+		c.rlimiter.Output() != nil &&
+		c.rlimiter.Output().Limit(len(p)) < len(p) {
+		n = len(p)
+		return
+	}
+
+	return c.PacketConn.WriteTo(p, addr)
+}
diff --git a/limiter/wrapper/listener.go b/limiter/wrapper/listener.go
new file mode 100644
index 0000000..42a2c8a
--- /dev/null
+++ b/limiter/wrapper/listener.go
@@ -0,0 +1,32 @@
+package wrapper
+
+import (
+	"net"
+
+	"github.com/go-gost/core/limiter"
+)
+
+type listener struct {
+	net.Listener
+	rlimiter limiter.RateLimiter
+}
+
+func WrapListener(rlimiter limiter.RateLimiter, ln net.Listener) net.Listener {
+	if rlimiter == nil {
+		return ln
+	}
+
+	return &listener{
+		rlimiter: rlimiter,
+		Listener: ln,
+	}
+}
+
+func (ln *listener) Accept() (net.Conn, error) {
+	c, err := ln.Listener.Accept()
+	if err != nil {
+		return nil, err
+	}
+
+	return WrapConn(ln.rlimiter, c), nil
+}
diff --git a/listener/option.go b/listener/option.go
index 5a553c8..9424061 100644
--- a/listener/option.go
+++ b/listener/option.go
@@ -7,18 +7,20 @@ import (
 	"github.com/go-gost/core/admission"
 	"github.com/go-gost/core/auth"
 	"github.com/go-gost/core/chain"
+	"github.com/go-gost/core/limiter"
 	"github.com/go-gost/core/logger"
 )
 
 type Options struct {
-	Addr      string
-	Auther    auth.Authenticator
-	Auth      *url.Userinfo
-	TLSConfig *tls.Config
-	Admission admission.Admission
-	Chain     chain.Chainer
-	Logger    logger.Logger
-	Service   string
+	Addr        string
+	Auther      auth.Authenticator
+	Auth        *url.Userinfo
+	TLSConfig   *tls.Config
+	Admission   admission.Admission
+	RateLimiter limiter.RateLimiter
+	Chain       chain.Chainer
+	Logger      logger.Logger
+	Service     string
 }
 
 type Option func(opts *Options)
@@ -53,6 +55,12 @@ func AdmissionOption(admission admission.Admission) Option {
 	}
 }
 
+func RateLimiterOption(rlimiter limiter.RateLimiter) Option {
+	return func(opts *Options) {
+		opts.RateLimiter = rlimiter
+	}
+}
+
 func ChainOption(chain chain.Chainer) Option {
 	return func(opts *Options) {
 		opts.Chain = chain