Add UDPEgressPool

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/sagernet/gvisor v0.0.0-20250811.0-sing-box-mod.1
 	github.com/sagernet/netlink v0.0.0-20240612041022-b9a21c07ac6a
 	github.com/sagernet/nftables v0.3.0-mod.2
-	github.com/sagernet/sing v0.8.12-0.20260716111929-074fc9988b34
+	github.com/sagernet/sing v0.8.12-0.20260717023913-84ab32b56cb8
 	github.com/stretchr/testify v1.11.1
 	go4.org/netipx v0.0.0-20231129151722-fdeea329fbba
 	golang.org/x/exp v0.0.0-20240613232115-7f521ea00fb8

go.sum

@@ -24,8 +24,8 @@ github.com/sagernet/netlink v0.0.0-20240612041022-b9a21c07ac6a h1:ObwtHN2VpqE0ZN
 github.com/sagernet/netlink v0.0.0-20240612041022-b9a21c07ac6a/go.mod h1:xLnfdiJbSp8rNqYEdIW/6eDO4mVoogml14Bh2hSiFpM=
 github.com/sagernet/nftables v0.3.0-mod.2 h1:ck2KMU02OxL1eDFgGaWYglMDpoOZ7OHzxje+vW5Q0OQ=
 github.com/sagernet/nftables v0.3.0-mod.2/go.mod h1:8kslHG4VvYNihcco+i6uxIX7qbT8A56T0y5q7U44ZaQ=
-github.com/sagernet/sing v0.8.12-0.20260716111929-074fc9988b34 h1:rgSs2ttiz8EaubsOt0SkzsqciY0m0PRp3w/fOisPoNo=
+github.com/sagernet/sing v0.8.12-0.20260717023913-84ab32b56cb8 h1:dyRIj+MZ2rc9JVzJoG04jxu+MpvHrLIZLJr0QjNAMGg=
-github.com/sagernet/sing v0.8.12-0.20260716111929-074fc9988b34/go.mod h1:olXxWQNqRW/l2Q6JI3b2Qmz8iQnIFlOeeH8bx6JhgUA=
+github.com/sagernet/sing v0.8.12-0.20260717023913-84ab32b56cb8/go.mod h1:olXxWQNqRW/l2Q6JI3b2Qmz8iQnIFlOeeH8bx6JhgUA=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 github.com/vishvananda/netns v0.0.4 h1:Oeaw1EM2JMxD51g9uhtC0D7erkIjgmj8+JZc26m1YX8=

udp_egress.go

@@ -0,0 +1,287 @@
+package tun
+
+import (
+	"context"
+	"net"
+	"net/netip"
+	"runtime"
+	"slices"
+	"sync"
+	"sync/atomic"
+
+	"github.com/sagernet/sing/common/buf"
+	"github.com/sagernet/sing/common/control"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	"github.com/sagernet/sing/common/x/list"
+)
+
+const udpEgressBufferSize = 65535
+
+type UDPEgressPoolOptions struct {
+	Logger           logger.Logger
+	Network          string
+	Control          control.Func
+	InterfaceFinder  control.InterfaceFinder
+	InterfaceMonitor DefaultInterfaceMonitor
+	ExcludeInterface string
+	IsExempt         func() bool
+}
+
+type UDPEgressPool struct {
+	logger               logger.Logger
+	network              string
+	control              control.Func
+	interfaceFinder      control.InterfaceFinder
+	interfaceMonitor     DefaultInterfaceMonitor
+	excludeInterface     string
+	isExempt             func() bool
+	access               sync.Mutex
+	port                 uint16
+	anchorInterfaceIndex int
+	receiveDone          chan struct{}
+	members              map[udpEgressSpec]*udpEgressMember
+	state                atomic.Pointer[[]*udpEgressMember]
+	packetChan           chan udpEgressPacket
+	memberReaders        sync.WaitGroup
+	finderElement        *list.Element[control.InterfaceUpdateCallback]
+}
+
+type udpEgressSpec struct {
+	interfaceIndex int
+	interfaceName  string
+	prefix         netip.Prefix
+}
+
+type udpEgressMember struct {
+	prefix netip.Prefix
+	conn   *net.UDPConn
+}
+
+type udpEgressPacket struct {
+	buffer *buf.Buffer
+	source netip.AddrPort
+}
+
+func NewUDPEgressPool(options UDPEgressPoolOptions) *UDPEgressPool {
+	return &UDPEgressPool{
+		logger:               options.Logger,
+		network:              options.Network,
+		control:              options.Control,
+		interfaceFinder:      options.InterfaceFinder,
+		interfaceMonitor:     options.InterfaceMonitor,
+		excludeInterface:     options.ExcludeInterface,
+		isExempt:             options.IsExempt,
+		anchorInterfaceIndex: -1,
+		members:              make(map[udpEgressSpec]*udpEgressMember),
+		packetChan:           make(chan udpEgressPacket, 128),
+	}
+}
+
+func (p *UDPEgressPool) Close() {
+	p.SetEgressPort(0)
+	p.access.Lock()
+	defer p.access.Unlock()
+	if p.finderElement != nil {
+		p.interfaceFinder.UnregisterInterfaceUpdateCallback(p.finderElement)
+		p.finderElement = nil
+	}
+}
+
+func (p *UDPEgressPool) SetEgressPort(port uint16) bool {
+	p.access.Lock()
+	defer p.access.Unlock()
+	if p.port == port {
+		return p.state.Load() != nil
+	}
+	if p.receiveDone != nil {
+		close(p.receiveDone)
+		p.receiveDone = nil
+	}
+	p.port = 0
+	p.state.Store(nil)
+	for spec, member := range p.members {
+		delete(p.members, spec)
+		member.conn.Close()
+	}
+	p.memberReaders.Wait()
+	for {
+		select {
+		case packet := <-p.packetChan:
+			packet.buffer.Release()
+		default:
+			goto drained
+		}
+	}
+drained:
+	p.anchorInterfaceIndex = -1
+	if port == 0 {
+		return false
+	}
+	p.port = port
+	defaultInterface := p.interfaceMonitor.DefaultInterface()
+	if defaultInterface != nil {
+		p.anchorInterfaceIndex = defaultInterface.Index
+	}
+	p.receiveDone = make(chan struct{})
+	if p.finderElement == nil {
+		p.finderElement = p.interfaceFinder.RegisterInterfaceUpdateCallback(func(interfaces []control.Interface) {
+			p.access.Lock()
+			defer p.access.Unlock()
+			p.rebuildLocked()
+		})
+	}
+	p.rebuildLocked()
+	return p.state.Load() != nil
+}
+
+func (p *UDPEgressPool) LookupEgress(destination netip.AddrPort) *net.UDPConn {
+	members := p.state.Load()
+	if members == nil {
+		return nil
+	}
+	address := destination.Addr().Unmap()
+	for _, member := range *members {
+		if member.prefix.Contains(address) {
+			return member.conn
+		}
+	}
+	return nil
+}
+
+func (p *UDPEgressPool) ReceiveEgress(buffer []byte) (int, netip.AddrPort, error) {
+	p.access.Lock()
+	receiveDone := p.receiveDone
+	p.access.Unlock()
+	if receiveDone == nil {
+		return 0, netip.AddrPort{}, net.ErrClosed
+	}
+	select {
+	case <-receiveDone:
+		return 0, netip.AddrPort{}, net.ErrClosed
+	default:
+	}
+	select {
+	case packet := <-p.packetChan:
+		copied := copy(buffer, packet.buffer.Bytes())
+		packet.buffer.Release()
+		return copied, packet.source, nil
+	case <-receiveDone:
+		return 0, netip.AddrPort{}, net.ErrClosed
+	}
+}
+
+func (p *UDPEgressPool) rebuildLocked() {
+	if p.port == 0 {
+		return
+	}
+	specs := make(map[udpEgressSpec]struct{})
+	if !p.isExempt() {
+		for _, networkInterface := range p.interfaceFinder.Interfaces() {
+			if networkInterface.Flags&net.FlagUp == 0 ||
+				networkInterface.Flags&net.FlagLoopback != 0 ||
+				networkInterface.Flags&net.FlagPointToPoint != 0 ||
+				networkInterface.Flags&net.FlagBroadcast == 0 ||
+				networkInterface.Index == p.anchorInterfaceIndex ||
+				networkInterface.Name == p.excludeInterface {
+				continue
+			}
+			for _, prefix := range networkInterface.Addresses {
+				if !prefix.Addr().IsGlobalUnicast() {
+					continue
+				}
+				if p.network == "udp4" && !prefix.Addr().Is4() {
+					continue
+				}
+				if p.network == "udp6" && prefix.Addr().Is4() {
+					continue
+				}
+				specs[udpEgressSpec{
+					interfaceIndex: networkInterface.Index,
+					interfaceName:  networkInterface.Name,
+					prefix:         prefix,
+				}] = struct{}{}
+			}
+		}
+	}
+	for spec, member := range p.members {
+		_, loaded := specs[spec]
+		if loaded {
+			continue
+		}
+		delete(p.members, spec)
+		member.conn.Close()
+	}
+	for spec := range specs {
+		_, loaded := p.members[spec]
+		if loaded {
+			continue
+		}
+		memberConn, err := p.listenMember(spec)
+		if err != nil {
+			p.logger.Warn(E.Cause(err, "listen egress member on ", spec.interfaceName, " (", spec.prefix.Addr(), ")"))
+			continue
+		}
+		member := &udpEgressMember{
+			prefix: spec.prefix.Masked(),
+			conn:   memberConn,
+		}
+		p.members[spec] = member
+		p.memberReaders.Add(1)
+		go p.readMember(member, p.receiveDone)
+	}
+	members := make([]*udpEgressMember, 0, len(p.members))
+	for _, member := range p.members {
+		members = append(members, member)
+	}
+	slices.SortFunc(members, func(firstMember, secondMember *udpEgressMember) int {
+		return secondMember.prefix.Bits() - firstMember.prefix.Bits()
+	})
+	if len(members) == 0 {
+		p.state.Store(nil)
+	} else {
+		p.state.Store(&members)
+	}
+}
+
+func (p *UDPEgressPool) listenMember(spec udpEgressSpec) (*net.UDPConn, error) {
+	var listenConfig net.ListenConfig
+	if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+		listenConfig.Control = control.ReuseAddrOnly()
+	}
+	listenConfig.Control = control.Append(listenConfig.Control, control.DisableUDPNetReset())
+	listenConfig.Control = control.Append(listenConfig.Control, control.BindToInterface(p.interfaceFinder, spec.interfaceName, spec.interfaceIndex))
+	listenConfig.Control = control.Append(listenConfig.Control, p.control)
+	var network string
+	if spec.prefix.Addr().Is4() {
+		network = "udp4"
+	} else {
+		network = "udp6"
+	}
+	packetConn, err := listenConfig.ListenPacket(context.Background(), network, netip.AddrPortFrom(spec.prefix.Addr(), p.port).String())
+	if err != nil {
+		return nil, err
+	}
+	return packetConn.(*net.UDPConn), nil
+}
+
+func (p *UDPEgressPool) readMember(member *udpEgressMember, doneChan <-chan struct{}) {
+	defer p.memberReaders.Done()
+	for {
+		buffer := buf.NewSize(udpEgressBufferSize)
+		dataLength, source, err := member.conn.ReadFromUDPAddrPort(buffer.FreeBytes())
+		if err != nil {
+			buffer.Release()
+			return
+		}
+		buffer.Extend(dataLength)
+		select {
+		case p.packetChan <- udpEgressPacket{buffer: buffer, source: source}:
+		case <-doneChan:
+			buffer.Release()
+			return
+		default:
+			buffer.Release()
+		}
+	}
+}

udp_egress_conn.go

@@ -0,0 +1,124 @@
+package tun
+
+import (
+	"net"
+	"net/netip"
+	"sync"
+	"time"
+
+	"github.com/sagernet/sing/common/buf"
+	E "github.com/sagernet/sing/common/exceptions"
+)
+
+type UDPEgressConn struct {
+	anchor     *net.UDPConn
+	pool       *UDPEgressPool
+	packetChan chan udpEgressConnPacket
+	doneChan   chan struct{}
+	closeOnce  sync.Once
+	readWait   sync.WaitGroup
+}
+
+type udpEgressConnPacket struct {
+	buffer *buf.Buffer
+	source netip.AddrPort
+	err    error
+}
+
+func NewUDPEgressConn(anchor *net.UDPConn, pool *UDPEgressPool) *UDPEgressConn {
+	conn := &UDPEgressConn{
+		anchor:     anchor,
+		pool:       pool,
+		packetChan: make(chan udpEgressConnPacket, 64),
+		doneChan:   make(chan struct{}),
+	}
+	conn.readWait.Add(2)
+	go conn.read(anchor.ReadFromUDPAddrPort)
+	go conn.read(pool.ReceiveEgress)
+	return conn
+}
+
+func (c *UDPEgressConn) read(readPacket func([]byte) (int, netip.AddrPort, error)) {
+	defer c.readWait.Done()
+	for {
+		buffer := buf.NewSize(udpEgressBufferSize)
+		dataLength, source, err := readPacket(buffer.FreeBytes())
+		if err != nil {
+			buffer.Release()
+			if E.IsClosed(err) {
+				return
+			}
+			select {
+			case c.packetChan <- udpEgressConnPacket{err: err}:
+			case <-c.doneChan:
+				return
+			}
+			continue
+		}
+		buffer.Extend(dataLength)
+		select {
+		case c.packetChan <- udpEgressConnPacket{buffer: buffer, source: source}:
+		case <-c.doneChan:
+			buffer.Release()
+			return
+		}
+	}
+}
+
+func (c *UDPEgressConn) ReadFromUDPAddrPort(buffer []byte) (int, netip.AddrPort, error) {
+	select {
+	case packet := <-c.packetChan:
+		if packet.err != nil {
+			return 0, netip.AddrPort{}, packet.err
+		}
+		copied := copy(buffer, packet.buffer.Bytes())
+		packet.buffer.Release()
+		return copied, packet.source, nil
+	case <-c.doneChan:
+		return 0, netip.AddrPort{}, net.ErrClosed
+	}
+}
+
+func (c *UDPEgressConn) WriteToUDPAddrPort(buffer []byte, destination netip.AddrPort) (int, error) {
+	memberConn := c.pool.LookupEgress(destination)
+	if memberConn != nil {
+		return memberConn.WriteToUDPAddrPort(buffer, destination)
+	}
+	return c.anchor.WriteToUDPAddrPort(buffer, destination)
+}
+
+func (c *UDPEgressConn) LocalAddr() net.Addr {
+	return c.anchor.LocalAddr()
+}
+
+func (c *UDPEgressConn) SetDeadline(t time.Time) error {
+	return c.anchor.SetDeadline(t)
+}
+
+func (c *UDPEgressConn) SetReadDeadline(t time.Time) error {
+	return c.anchor.SetReadDeadline(t)
+}
+
+func (c *UDPEgressConn) SetWriteDeadline(t time.Time) error {
+	return c.anchor.SetWriteDeadline(t)
+}
+
+func (c *UDPEgressConn) Close() error {
+	c.closeOnce.Do(func() {
+		close(c.doneChan)
+		c.anchor.Close()
+		c.pool.Close()
+		c.readWait.Wait()
+		for {
+			select {
+			case packet := <-c.packetChan:
+				if packet.buffer != nil {
+					packet.buffer.Release()
+				}
+			default:
+				return
+			}
+		}
+	})
+	return nil
+}