Support FreeBSD

.gitignore

@@ -1,5 +1,6 @@
 /.idea/
 /vendor/
 .DS_Store
+.worktrees/
 !/README.md
 /*.md

Makefile

@@ -6,7 +6,9 @@ build:
 	GOOS=linux GOARCH=386 go build -v -tags with_gvisor .
 	GOOS=linux GOARCH=arm go build -v -tags with_gvisor .
 	GOOS=android GOARCH=arm64 go build -v -tags with_gvisor .
+	GOOS=freebsd GOARCH=amd64 go build -v -tags with_gvisor .
 	GOOS=windows GOARCH=amd64 go build -v -tags with_gvisor .
+	GOOS=freebsd GOARCH=amd64 go build -v -tags with_gvisor .
 
 fmt:
 	@gofumpt -l -w .

monitor_freebsd.go

@@ -0,0 +1,174 @@
+package tun
+
+import (
+	"net"
+	"net/netip"
+	"os"
+	"sync"
+
+	"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"
+	"golang.org/x/net/route"
+	"golang.org/x/sys/unix"
+)
+
+var _ NetworkUpdateMonitor = (*networkUpdateMonitor)(nil)
+
+type networkUpdateMonitor struct {
+	access          sync.Mutex
+	callbacks       list.List[NetworkUpdateCallback]
+	routeSocketFile *os.File
+	closeOnce       sync.Once
+	done            chan struct{}
+	logger          logger.Logger
+}
+
+func NewNetworkUpdateMonitor(logger logger.Logger) (NetworkUpdateMonitor, error) {
+
+	return &networkUpdateMonitor{
+		logger: logger,
+		done:   make(chan struct{}),
+	}, nil
+}
+
+// Close implements NetworkUpdateMonitor.
+func (m *networkUpdateMonitor) Close() error {
+	m.closeOnce.Do(func() {
+		close(m.done)
+	})
+	return nil
+}
+
+// Start implements NetworkUpdateMonitor.
+func (m *networkUpdateMonitor) Start() error {
+	go m.loopUpdate()
+	return nil
+}
+
+func (m *networkUpdateMonitor) loopUpdate() {
+	for {
+		select {
+		case <-m.done:
+			return
+		default:
+		}
+		err := m.loopUpdate0()
+		if err != nil {
+			m.logger.Error("listen network update: ", err)
+			return
+		}
+	}
+}
+
+func (m *networkUpdateMonitor) loopUpdate0() error {
+	routeSocket, err := unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, 0)
+	if err != nil {
+		return err
+	}
+	err = unix.SetNonblock(routeSocket, true)
+	if err != nil {
+		unix.Close(routeSocket)
+		return err
+	}
+	routeSocketFile := os.NewFile(uintptr(routeSocket), "route")
+	defer routeSocketFile.Close()
+	m.routeSocketFile = routeSocketFile
+	m.loopUpdate1(routeSocketFile)
+	return nil
+}
+
+func (m *networkUpdateMonitor) loopUpdate1(routeSocketFile *os.File) {
+	buffer := buf.NewPacket()
+	defer buffer.Release()
+
+	done := make(chan struct{})
+	go func() {
+		select {
+		case <-m.done:
+			routeSocketFile.Close()
+		case <-done:
+		}
+	}()
+	n, err := routeSocketFile.Read(buffer.FreeBytes())
+	close(done)
+	if err != nil {
+		return
+	}
+	buffer.Truncate(n)
+
+	messages, err := route.ParseRIB(route.RIBTypeRoute, buffer.Bytes())
+	if err != nil {
+		return
+	}
+
+	for _, message := range messages {
+		if _, isRouteMessage := message.(*route.RouteMessage); isRouteMessage {
+			m.emit()
+			return
+		}
+	}
+}
+
+// checkUpdate finds the first IPv4 default gateway and emits an update event.
+func (m *defaultInterfaceMonitor) checkUpdate() error {
+	var defaultInterface *control.Interface
+	ribMessage, err := route.FetchRIB(unix.AF_INET, route.RIBTypeRoute, 0)
+	if err != nil {
+		return err
+	}
+	routeMessages, err := route.ParseRIB(route.RIBTypeRoute, ribMessage)
+	if err != nil {
+		return err
+	}
+
+	for _, rawRouteMessage := range routeMessages {
+		routeMessage := rawRouteMessage.(*route.RouteMessage)
+		if len(routeMessage.Addrs) <= unix.RTAX_NETMASK {
+			continue
+		}
+		destination, isIPv4Destination := routeMessage.Addrs[unix.RTAX_DST].(*route.Inet4Addr)
+		if !isIPv4Destination || destination.IP != netip.IPv4Unspecified().As4() {
+			continue
+		}
+		mask, isIPv4Mask := routeMessage.Addrs[unix.RTAX_NETMASK].(*route.Inet4Addr)
+		if !isIPv4Mask {
+			continue
+		}
+		if ones, _ := net.IPMask(mask.IP[:]).Size(); ones != 0 {
+			continue
+		}
+		flag := unix.RTF_UP | unix.RTF_GATEWAY | unix.RTF_STATIC
+		if routeMessage.Flags&(flag) != flag {
+			continue
+		}
+		routeInterface, err := m.interfaceFinder.ByIndex(routeMessage.Index)
+		if err != nil {
+			return err
+		}
+		if routeInterface.Flags&net.FlagLoopback != 0 {
+			continue
+		}
+		defaultInterface = routeInterface
+		break
+	}
+
+	if defaultInterface == nil {
+		if m.underNetworkExtension {
+			m.logger.Warn("Not implemented: UnderNetworkExtension")
+		}
+		return ErrNoRoute
+	}
+	newInterface, err := m.interfaceFinder.ByIndex(defaultInterface.Index)
+	if err != nil {
+		return E.Cause(err, "find updated interface: ", defaultInterface.Name)
+	}
+	oldInterface := m.defaultInterface.Swap(newInterface)
+	if oldInterface != nil && oldInterface.Equals(*newInterface) {
+		return nil
+	}
+	m.emit(newInterface, 0)
+	return nil
+}

monitor_other.go

@@ -1,4 +1,4 @@
-//go:build !(linux || windows || darwin)
+//go:build !(linux || windows || darwin || freebsd)
 
 package tun
 

monitor_shared.go

@@ -1,4 +1,4 @@
-//go:build linux || windows || darwin
+//go:build linux || windows || darwin || freebsd
 
 package tun