From 717872ef6d233637fce536b14359037e2911e1ef Mon Sep 17 00:00:00 2001
From: HystericalDragon <HystericalDragons@proton.me>
Date: Tue, 1 Oct 2024 12:08:34 +0800
Subject: [PATCH 1/2] feat: add anchor, a protocol to share proxy in Lan

Signed-off-by: HystericalDragon <HystericalDragons@proton.me>
---
 .../java/io/nekohasekai/sagernet/Constants.kt |   1 +
 .../sagernet/bg/NativeInterface.kt            |   4 +
 .../sagernet/database/DataStore.kt            |   1 +
 .../sagernet/ui/SettingsPreferenceFragment.kt |  13 ++
 app/src/main/res/values-zh-rCN/strings.xml    |   1 +
 app/src/main/res/values/strings.xml           |   1 +
 app/src/main/res/xml/global_preferences.xml   |   4 +
 libcore/anchor/option.go                      |  12 ++
 libcore/anchor/service.go                     | 120 ++++++++++++++++++
 libcore/box.go                                |  30 +++++
 libcore/go.mod                                |   1 +
 libcore/go.sum                                |   2 +
 libcore/platform_java.go                      |   1 +
 13 files changed, 191 insertions(+)
 create mode 100644 libcore/anchor/option.go
 create mode 100644 libcore/anchor/service.go

diff --git a/app/src/main/java/io/nekohasekai/sagernet/Constants.kt b/app/src/main/java/io/nekohasekai/sagernet/Constants.kt
index 4290737d..b4becb35 100644
--- a/app/src/main/java/io/nekohasekai/sagernet/Constants.kt
+++ b/app/src/main/java/io/nekohasekai/sagernet/Constants.kt
@@ -49,6 +49,7 @@ object Key {
 
     const val MIXED_PORT = "mixedPort"
     const val ALLOW_ACCESS = "allowAccess"
+    const val DISCOVERY_IN_LAN = "discoveryInLan"
     const val SPEED_INTERVAL = "speedInterval"
     const val SHOW_DIRECT_SPEED = "showDirectSpeed"
     const val LOCAL_DNS_PORT = "portLocalDns"
diff --git a/app/src/main/java/io/nekohasekai/sagernet/bg/NativeInterface.kt b/app/src/main/java/io/nekohasekai/sagernet/bg/NativeInterface.kt
index bb30849e..49281cdb 100644
--- a/app/src/main/java/io/nekohasekai/sagernet/bg/NativeInterface.kt
+++ b/app/src/main/java/io/nekohasekai/sagernet/bg/NativeInterface.kt
@@ -164,4 +164,8 @@ class NativeInterface : PlatformInterface {
         return SDK_INT >= Build.VERSION_CODES.R // SDK 30 (Android 11)
     }
 
+    override fun allowDiscoveryByLan(): Boolean {
+        return DataStore.discoveryInLan
+    }
+
 }
diff --git a/app/src/main/java/io/nekohasekai/sagernet/database/DataStore.kt b/app/src/main/java/io/nekohasekai/sagernet/database/DataStore.kt
index 72858134..999f7b70 100644
--- a/app/src/main/java/io/nekohasekai/sagernet/database/DataStore.kt
+++ b/app/src/main/java/io/nekohasekai/sagernet/database/DataStore.kt
@@ -112,6 +112,7 @@ object DataStore : OnPreferenceDataStoreChangeListener {
     var inboundPassword by configurationStore.string(Key.INBOUND_PASSWORD) { "" }
 
     var allowAccess by configurationStore.boolean(Key.ALLOW_ACCESS)
+    var discoveryInLan by configurationStore.boolean(Key.DISCOVERY_IN_LAN)
     var speedInterval by configurationStore.stringToInt(Key.SPEED_INTERVAL)
     var showGroupInNotification by configurationStore.boolean("showGroupInNotification")
 
diff --git a/app/src/main/java/io/nekohasekai/sagernet/ui/SettingsPreferenceFragment.kt b/app/src/main/java/io/nekohasekai/sagernet/ui/SettingsPreferenceFragment.kt
index e649d75e..b4fc2880 100644
--- a/app/src/main/java/io/nekohasekai/sagernet/ui/SettingsPreferenceFragment.kt
+++ b/app/src/main/java/io/nekohasekai/sagernet/ui/SettingsPreferenceFragment.kt
@@ -64,6 +64,9 @@ class SettingsPreferenceFragment : PreferenceFragmentCompat() {
         lateinit var bypassLan: SwitchPreference
         lateinit var bypassLanInCore: SwitchPreference
 
+        lateinit var allowAccess: SwitchPreference
+        lateinit var discoveryInLan: SwitchPreference
+
         lateinit var logLevel: LongClickListPreference
         lateinit var alwaysShowAddress: SwitchPreference
         lateinit var blurredAddress: SwitchPreference
@@ -177,6 +180,8 @@ class SettingsPreferenceFragment : PreferenceFragmentCompat() {
                 Key.INBOUND_SETTINGS -> preferenceCategory.forEach { preference ->
                     when (preference.key) {
                         Key.MIXED_PORT, Key.LOCAL_DNS_PORT -> (preference as EditTextPreference).setPortEdit()
+                        Key.ALLOW_ACCESS -> allowAccess = preference as SwitchPreference
+                        Key.DISCOVERY_IN_LAN -> discoveryInLan = preference as SwitchPreference
                         else -> preference.onPreferenceChangeListener = reloadListener
                     }
                 }
@@ -275,6 +280,14 @@ class SettingsPreferenceFragment : PreferenceFragmentCompat() {
             true
         }
 
+        discoveryInLan.isEnabled = bypassLan.isChecked
+        discoveryInLan.onPreferenceChangeListener = reloadListener
+        allowAccess.setOnPreferenceChangeListener { _, newValue ->
+            discoveryInLan.isEnabled = newValue as Boolean
+            needReload()
+            true
+        }
+
         blurredAddress.isEnabled = alwaysShowAddress.isChecked
         alwaysShowAddress.setOnPreferenceChangeListener { _, newValue ->
             blurredAddress.isEnabled = newValue as Boolean
diff --git a/app/src/main/res/values-zh-rCN/strings.xml b/app/src/main/res/values-zh-rCN/strings.xml
index 8deba375..d1a92f65 100644
--- a/app/src/main/res/values-zh-rCN/strings.xml
+++ b/app/src/main/res/values-zh-rCN/strings.xml
@@ -588,4 +588,5 @@
     <string name="override_port">覆写端口</string>
     <string name="allow_apps_bypass_vpn">允许应用绕过 VPN</string>
     <string name="clash_mode">Clash 模式</string>
+    <string name="enable_local_network_discovery">允许局域网发现</string>
 </resources>
\ No newline at end of file
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 006aad86..690a7159 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -655,4 +655,5 @@
     <string name="override_port">Override Port</string>
     <string name="allow_apps_bypass_vpn">Allow Apps to bypass VPN</string>
     <string name="clash_mode">Clash Mode</string>
+    <string name="enable_local_network_discovery">Enable Local Network Discovery</string>
 </resources>
\ No newline at end of file
diff --git a/app/src/main/res/xml/global_preferences.xml b/app/src/main/res/xml/global_preferences.xml
index 17193179..0ee3b2ab 100644
--- a/app/src/main/res/xml/global_preferences.xml
+++ b/app/src/main/res/xml/global_preferences.xml
@@ -267,6 +267,10 @@
             app:key="allowAccess"
             app:summary="@string/allow_access_sum"
             app:title="@string/allow_access" />
+        <SwitchPreference
+            app:icon="@drawable/ic_baseline_location_on_24"
+            app:key="discoveryInLan"
+            app:title="@string/enable_local_network_discovery" />
         <EditTextPreference
             app:icon="@drawable/ic_baseline_person_24"
             app:key="inboundUsername"
diff --git a/libcore/anchor/option.go b/libcore/anchor/option.go
new file mode 100644
index 00000000..979c83f5
--- /dev/null
+++ b/libcore/anchor/option.go
@@ -0,0 +1,12 @@
+package anchor
+
+import (
+	"github.com/sagernet/sing/common/auth"
+)
+
+type Options struct {
+	SocksPort  uint16
+	User       auth.User
+	DnsPort    uint16
+	DeviceName string
+}
diff --git a/libcore/anchor/service.go b/libcore/anchor/service.go
new file mode 100644
index 00000000..a1536426
--- /dev/null
+++ b/libcore/anchor/service.go
@@ -0,0 +1,120 @@
+// Package anchor provides anchor API server.
+package anchor
+
+import (
+	"context"
+	"net"
+	"os"
+
+	"github.com/sagernet/sing-box/adapter"
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/buf"
+	E "github.com/sagernet/sing/common/exceptions"
+	"github.com/sagernet/sing/common/logger"
+	N "github.com/sagernet/sing/common/network"
+
+	"github.com/xchacha20-poly1305/anchor"
+)
+
+var (
+	_ adapter.Service = (*Anchor)(nil)
+	_ E.Handler       = (*Anchor)(nil)
+)
+
+type Anchor struct {
+	ctx        context.Context
+	logger     logger.ContextLogger
+	packetConn net.PacketConn
+	response   []byte
+	done       chan struct{}
+}
+
+func New(ctx context.Context, ctxLogger logger.ContextLogger, options Options) (*Anchor, error) {
+	packetConn, err := net.ListenUDP(N.NetworkUDP+"4", &net.UDPAddr{
+		IP:   net.IPv4zero, // Not listen IPv6
+		Port: anchor.Port,
+	})
+	if err != nil {
+		return nil, E.Cause(err, "listen anchor API")
+	}
+	if ctxLogger == nil {
+		ctxLogger = logger.NOP()
+	}
+	response, _ := (&anchor.Response{
+		Version:    anchor.Version,
+		DnsPort:    options.DnsPort,
+		DeviceName: options.DeviceName,
+		SocksPort:  options.SocksPort,
+		User:       options.User,
+	}).MarshalBinary()
+	return &Anchor{
+		ctx:        ctx,
+		logger:     ctxLogger,
+		response:   response,
+		packetConn: packetConn,
+		done:       make(chan struct{}),
+	}, nil
+}
+
+func (a *Anchor) Start() error {
+	go a.loop()
+	return nil
+}
+
+func (a *Anchor) loop() {
+	a.logger.InfoContext(a.ctx, "Anchor: started loop")
+	stop := context.AfterFunc(a.ctx, func() {
+		_ = a.Close()
+	})
+	for {
+		select {
+		case <-a.ctx.Done():
+			return
+		case <-a.done:
+			return
+		default:
+		}
+		buffer := buf.NewSize(anchor.MaxQuerySize)
+		_, source, err := buffer.ReadPacketFrom(a.packetConn)
+		if err != nil {
+			stop()
+			buffer.Release()
+			a.NewError(a.ctx, err)
+			return
+		}
+		go a.handle(source, buffer)
+	}
+}
+
+func (a *Anchor) handle(source net.Addr, buffer *buf.Buffer) {
+	defer buffer.Release()
+	a.logger.TraceContext(a.ctx, "Anchor: new query from: ", source)
+	query, err := anchor.ParseQuery(buffer.Bytes())
+	if err != nil {
+		a.NewError(a.ctx, err)
+		return
+	}
+	a.logger.TraceContext(a.ctx, "Anchor: device name: ", query.DeviceName)
+	_, err = a.packetConn.WriteTo(a.response, source)
+	if err != nil {
+		a.NewError(a.ctx, err)
+		return
+	}
+}
+
+func (a *Anchor) NewError(ctx context.Context, err error) {
+	if E.IsClosedOrCanceled(err) {
+		return
+	}
+	a.logger.InfoContext(ctx, "Anchor: ", err)
+}
+
+func (a *Anchor) Close() error {
+	select {
+	case <-a.done:
+		return os.ErrClosed
+	default:
+		close(a.done)
+	}
+	return common.Close(a.packetConn)
+}
diff --git a/libcore/box.go b/libcore/box.go
index ebdf3751..2cf7d5a9 100644
--- a/libcore/box.go
+++ b/libcore/box.go
@@ -2,6 +2,7 @@ package libcore
 
 import (
 	"context"
+	"net/netip"
 	"time"
 
 	box "github.com/sagernet/sing-box"
@@ -19,6 +20,7 @@ import (
 	"github.com/sagernet/sing/service"
 	"github.com/sagernet/sing/service/pause"
 
+	"libcore/anchor"
 	"libcore/protect"
 	"libcore/v2rayapilite"
 )
@@ -110,6 +112,34 @@ func NewBoxInstance(config string, platformInterface PlatformInterface) (b *BoxI
 			}
 		}
 
+		if platformInterface.AllowDiscoveryByLan() {
+			var anchorOptions anchor.Options
+			for _, inbound := range options.Inbounds {
+				switch inbound.Type {
+				case C.TypeMixed:
+					listen := (*netip.Addr)(inbound.MixedOptions.Listen)
+					if !listen.IsUnspecified() {
+						break
+					}
+					anchorOptions.SocksPort = inbound.MixedOptions.ListenPort
+					if len(inbound.MixedOptions.Users) > 0 {
+						anchorOptions.User = inbound.MixedOptions.Users[0]
+					}
+				case C.TypeDirect:
+					if inbound.Tag != "dns-in" {
+						continue
+					}
+					anchorOptions.DnsPort = inbound.DirectOptions.OverridePort
+				}
+			}
+			anchorServer, err := anchor.New(ctx, log.StdLogger(), anchorOptions)
+			if err != nil {
+				log.WarnContext(ctx, "create anchor service: ", err)
+			} else {
+				b.services = append(b.services, anchorServer)
+			}
+		}
+
 		// Protect
 		protectServer, err := protect.New(ctx, log.StdLogger(), ProtectPath, func(fd int) error {
 			return platformInterface.AutoDetectInterfaceControl(int32(fd))
diff --git a/libcore/go.mod b/libcore/go.mod
index 361e8811..44373f5f 100644
--- a/libcore/go.mod
+++ b/libcore/go.mod
@@ -12,6 +12,7 @@ require (
 	github.com/sagernet/sing-dns v0.3.0-beta.14
 	github.com/sagernet/sing-tun v0.4.0-beta.16
 	github.com/xchacha20-poly1305/TLS-scribe v0.6.1
+	github.com/xchacha20-poly1305/anchor v0.2.0-beta.0
 	github.com/xchacha20-poly1305/cazilla v0.3.3
 	github.com/xchacha20-poly1305/libping v0.7.1
 	golang.org/x/crypto v0.27.0
diff --git a/libcore/go.sum b/libcore/go.sum
index 797d6c50..85767a1f 100644
--- a/libcore/go.sum
+++ b/libcore/go.sum
@@ -154,6 +154,8 @@ github.com/vishvananda/netns v0.0.4 h1:Oeaw1EM2JMxD51g9uhtC0D7erkIjgmj8+JZc26m1Y
 github.com/vishvananda/netns v0.0.4/go.mod h1:SpkAiCQRtJ6TvvxPnOSyH3BMl6unz3xZlaprSwhNNJM=
 github.com/xchacha20-poly1305/TLS-scribe v0.6.1 h1:eMe562VUOSjoumbom/XS1O5mw0A3/QOKPyLgwAjVDgo=
 github.com/xchacha20-poly1305/TLS-scribe v0.6.1/go.mod h1:2suBWLi3ESUbkp97tMz1okYK6Dh9XpjRzyO7eMA5s6Q=
+github.com/xchacha20-poly1305/anchor v0.2.0-beta.0 h1:qic4oHg2TNeOaRSyDIPkeEDqAXzgITjiR01FIFhqm18=
+github.com/xchacha20-poly1305/anchor v0.2.0-beta.0/go.mod h1:/QUPDmgmJ0q7m5vuPte9Bve9vXLS/SNophSntKuCrX4=
 github.com/xchacha20-poly1305/cazilla v0.3.3 h1:9qKZHKexlzGHmXeAHVOwj0dnc9/WEftGSwwWC3703wM=
 github.com/xchacha20-poly1305/cazilla v0.3.3/go.mod h1:CRNqqSLuWw8gStu7qDwjPYmsLE91OCVWazN9AH4LyWc=
 github.com/xchacha20-poly1305/libping v0.7.1 h1:MQkq6gxn67SZlBgG2Wp7ek0QYQsxKnKSbg0h235S6+o=
diff --git a/libcore/platform_java.go b/libcore/platform_java.go
index 3e2820d1..3a3aed91 100644
--- a/libcore/platform_java.go
+++ b/libcore/platform_java.go
@@ -14,6 +14,7 @@ type PlatformInterface interface {
 	GetInterfaces() (NetworkInterfaceIterator, error)
 	UsePlatformInterfaceGetter() bool
 
+	AllowDiscoveryByLan() bool
 	SelectorCallback(tag string)
 	ClashModeCallback(mode string)
 }

From f70887f0ac8026193a45b46e4ede59f132cdfbf3 Mon Sep 17 00:00:00 2001
From: "coderabbitai[bot]"
 <136622811+coderabbitai[bot]@users.noreply.github.com>
Date: Fri, 4 Oct 2024 16:43:52 +0800
Subject: [PATCH 2/2] Fix break loop

---
 libcore/box.go | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libcore/box.go b/libcore/box.go
index 2cf7d5a9..bd96e1ef 100644
--- a/libcore/box.go
+++ b/libcore/box.go
@@ -114,12 +114,13 @@ func NewBoxInstance(config string, platformInterface PlatformInterface) (b *BoxI
 
 		if platformInterface.AllowDiscoveryByLan() {
 			var anchorOptions anchor.Options
+		Find:
 			for _, inbound := range options.Inbounds {
 				switch inbound.Type {
 				case C.TypeMixed:
 					listen := (*netip.Addr)(inbound.MixedOptions.Listen)
 					if !listen.IsUnspecified() {
-						break
+						break Find
 					}
 					anchorOptions.SocksPort = inbound.MixedOptions.ListenPort
 					if len(inbound.MixedOptions.Users) > 0 {