[client] Refactor/iface pkg (#2646)

Refactor the flat code structure

client/iface/netstack/tun.go

@@ -0,0 +1,74 @@
+package netstack
+
+import (
+	"net/netip"
+
+	log "github.com/sirupsen/logrus"
+	"golang.zx2c4.com/wireguard/tun"
+	"golang.zx2c4.com/wireguard/tun/netstack"
+)
+
+type NetStackTun struct { //nolint:revive
+	address       string
+	mtu           int
+	listenAddress string
+
+	proxy  *Proxy
+	tundev tun.Device
+}
+
+func NewNetStackTun(listenAddress string, address string, mtu int) *NetStackTun {
+	return &NetStackTun{
+		address:       address,
+		mtu:           mtu,
+		listenAddress: listenAddress,
+	}
+}
+
+func (t *NetStackTun) Create() (tun.Device, error) {
+	nsTunDev, tunNet, err := netstack.CreateNetTUN(
+		[]netip.Addr{netip.MustParseAddr(t.address)},
+		[]netip.Addr{},
+		t.mtu)
+	if err != nil {
+		return nil, err
+	}
+	t.tundev = nsTunDev
+
+	dialer := NewNSDialer(tunNet)
+	t.proxy, err = NewSocks5(dialer)
+	if err != nil {
+		_ = t.tundev.Close()
+		return nil, err
+	}
+
+	go func() {
+		err := t.proxy.ListenAndServe(t.listenAddress)
+		if err != nil {
+			log.Errorf("error in socks5 proxy serving: %s", err)
+		}
+	}()
+
+	return nsTunDev, nil
+}
+
+func (t *NetStackTun) Close() error {
+	var err error
+	if t.proxy != nil {
+		pErr := t.proxy.Close()
+		if pErr != nil {
+			log.Errorf("failed to close socks5 proxy: %s", pErr)
+			err = pErr
+		}
+	}
+
+	if t.tundev != nil {
+		dErr := t.tundev.Close()
+		if dErr != nil {
+			log.Errorf("failed to close netstack tun device: %s", dErr)
+			err = dErr
+		}
+	}
+
+	return err
+}