Add netns support

netns_linux.go

@@ -0,0 +1,73 @@
+package tun
+
+import (
+	"context"
+	"net"
+	"runtime"
+	"strings"
+
+	"github.com/sagernet/sing/common/control"
+	E "github.com/sagernet/sing/common/exceptions"
+
+	"golang.org/x/sys/unix"
+)
+
+func listenNetworkNamespace(ctx context.Context, nameOrPath string, config net.ListenConfig, network, address string) (net.Listener, error) {
+	return execInNetworkNamespace(nameOrPath, func() (net.Listener, error) {
+		return config.Listen(ctx, network, address)
+	})
+}
+
+type networkNamespaceInterfaceFinder struct {
+	control.InterfaceFinder
+	options *Options
+}
+
+func (f *networkNamespaceInterfaceFinder) Update() error {
+	return runInNetworkNamespace(f.options.NetNs, f.InterfaceFinder.Update)
+}
+
+func execInNetworkNamespace[T any](nameOrPath string, block func() (T, error)) (T, error) {
+	if nameOrPath == "" {
+		return block()
+	}
+	type blockResult struct {
+		value T
+		err   error
+	}
+	resultChannel := make(chan blockResult, 1)
+	go func() {
+		runtime.LockOSThread()
+		value, err := execInNetworkNamespaceThread(nameOrPath, block)
+		resultChannel <- blockResult{value, err}
+	}()
+	result := <-resultChannel
+	return result.value, result.err
+}
+
+func execInNetworkNamespaceThread[T any](nameOrPath string, block func() (T, error)) (T, error) {
+	var defaultValue T
+	var path string
+	if strings.HasPrefix(nameOrPath, "/") {
+		path = nameOrPath
+	} else {
+		path = "/run/netns/" + nameOrPath
+	}
+	targetFd, err := unix.Open(path, unix.O_RDONLY|unix.O_CLOEXEC, 0)
+	if err != nil {
+		return defaultValue, E.Cause(err, "open netns ", nameOrPath)
+	}
+	defer unix.Close(targetFd)
+	err = unix.Setns(targetFd, unix.CLONE_NEWNET)
+	if err != nil {
+		return defaultValue, E.Cause(err, "set netns to ", nameOrPath)
+	}
+	return block()
+}
+
+func runInNetworkNamespace(nameOrPath string, block func() error) error {
+	_, err := execInNetworkNamespace(nameOrPath, func() (struct{}, error) {
+		return struct{}{}, block()
+	})
+	return err
+}