chore: decrease direct udp read memory used for no-windows platform

common/net/packet.go

@@ -0,0 +1,68 @@
+package net
+
+import (
+	"net"
+
+	"github.com/Dreamacro/clash/common/pool"
+)
+
+type EnhancePacketConn interface {
+	net.PacketConn
+	WaitReadFrom() (data []byte, put func(), addr net.Addr, err error)
+	Upstream() any
+}
+
+func NewEnhancePacketConn(pc net.PacketConn) EnhancePacketConn {
+	if udpConn, isUDPConn := pc.(*net.UDPConn); isUDPConn {
+		return &enhanceUDPConn{UDPConn: udpConn}
+	}
+	return &enhancePacketConn{PacketConn: pc}
+}
+
+type enhancePacketConn struct {
+	net.PacketConn
+}
+
+func (c *enhancePacketConn) WaitReadFrom() (data []byte, put func(), addr net.Addr, err error) {
+	return waitReadFrom(c.PacketConn)
+}
+
+func (c *enhancePacketConn) Upstream() any {
+	return c.PacketConn
+}
+
+func (c *enhancePacketConn) WriterReplaceable() bool {
+	return true
+}
+
+func (c *enhancePacketConn) ReaderReplaceable() bool {
+	return true
+}
+
+func (c *enhanceUDPConn) Upstream() any {
+	return c.UDPConn
+}
+
+func (c *enhanceUDPConn) WriterReplaceable() bool {
+	return true
+}
+
+func (c *enhanceUDPConn) ReaderReplaceable() bool {
+	return true
+}
+
+func waitReadFrom(pc net.PacketConn) (data []byte, put func(), addr net.Addr, err error) {
+	readBuf := pool.Get(pool.UDPBufferSize)
+	put = func() {
+		_ = pool.Put(readBuf)
+	}
+	var readN int
+	readN, addr, err = pc.ReadFrom(readBuf)
+	if readN > 0 {
+		data = readBuf[:readN]
+	} else {
+		put()
+		put = nil
+	}
+	return
+}

common/net/packet_posix.go

@@ -0,0 +1,64 @@
+//go:build !windows
+
+package net
+
+import (
+	"io"
+	"net"
+	"strconv"
+	"syscall"
+
+	"github.com/Dreamacro/clash/common/pool"
+)
+
+type enhanceUDPConn struct {
+	*net.UDPConn
+	rawConn syscall.RawConn
+}
+
+func (c *enhanceUDPConn) WaitReadFrom() (data []byte, put func(), addr net.Addr, err error) {
+	if c.rawConn == nil {
+		c.rawConn, _ = c.UDPConn.SyscallConn()
+	}
+	var readErr error
+	err = c.rawConn.Read(func(fd uintptr) (done bool) {
+		readBuf := pool.Get(pool.UDPBufferSize)
+		put = func() {
+			_ = pool.Put(readBuf)
+		}
+		var readFrom syscall.Sockaddr
+		var readN int
+		readN, _, _, readFrom, readErr = syscall.Recvmsg(int(fd), readBuf, nil, 0)
+		if readN > 0 {
+			data = readBuf[:readN]
+		} else {
+			put()
+			put = nil
+		}
+		if readErr == syscall.EAGAIN {
+			return false
+		}
+		if readFrom != nil {
+			switch from := readFrom.(type) {
+			case *syscall.SockaddrInet4:
+				ip := from.Addr // copy from.Addr; ip escapes, so this line allocates 4 bytes
+				addr = &net.UDPAddr{IP: ip[:], Port: from.Port}
+			case *syscall.SockaddrInet6:
+				ip := from.Addr // copy from.Addr; ip escapes, so this line allocates 16 bytes
+				addr = &net.UDPAddr{IP: ip[:], Port: from.Port, Zone: strconv.FormatInt(int64(from.ZoneId), 10)}
+			}
+		}
+		if readN == 0 {
+			readErr = io.EOF
+		}
+		return true
+	})
+	if err != nil {
+		return
+	}
+	if readErr != nil {
+		err = readErr
+		return
+	}
+	return
+}

common/net/packet_windows.go

@@ -0,0 +1,15 @@
+//go:build windows
+
+package net
+
+import (
+	"net"
+)
+
+type enhanceUDPConn struct {
+	*net.UDPConn
+}
+
+func (c *enhanceUDPConn) WaitReadFrom() (data []byte, put func(), addr net.Addr, err error) {
+	return waitReadFrom(c.UDPConn)
+}