Netstack (#1403)

Add netstack support for the agent to run it without privileges.

- use interface for tun device
- use common IPC for userspace WireGuard integration
- move udpmux creation and sharedsock to tun layer

iface/tun_kernel_linux.go

@@ -0,0 +1,209 @@
+//go:build linux && !android
+
+package iface
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"os"
+
+	"github.com/pion/transport/v3"
+	log "github.com/sirupsen/logrus"
+	"github.com/vishvananda/netlink"
+
+	"github.com/netbirdio/netbird/iface/bind"
+	"github.com/netbirdio/netbird/sharedsock"
+)
+
+type tunKernelDevice struct {
+	name         string
+	address      WGAddress
+	wgPort       int
+	key          string
+	mtu          int
+	ctx          context.Context
+	ctxCancel    context.CancelFunc
+	transportNet transport.Net
+
+	link       *wgLink
+	udpMuxConn net.PacketConn
+	udpMux     *bind.UniversalUDPMuxDefault
+}
+
+func newTunDevice(name string, address WGAddress, wgPort int, key string, mtu int, transportNet transport.Net) wgTunDevice {
+	ctx, cancel := context.WithCancel(context.Background())
+	return &tunKernelDevice{
+		ctx:          ctx,
+		ctxCancel:    cancel,
+		name:         name,
+		address:      address,
+		wgPort:       wgPort,
+		key:          key,
+		mtu:          mtu,
+		transportNet: transportNet,
+	}
+}
+
+func (t *tunKernelDevice) Create() (wgConfigurer, error) {
+	link := newWGLink(t.name)
+
+	// check if interface exists
+	l, err := netlink.LinkByName(t.name)
+	if err != nil {
+		switch err.(type) {
+		case netlink.LinkNotFoundError:
+			break
+		default:
+			return nil, err
+		}
+	}
+
+	// remove if interface exists
+	if l != nil {
+		err = netlink.LinkDel(link)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	log.Debugf("adding device: %s", t.name)
+	err = netlink.LinkAdd(link)
+	if os.IsExist(err) {
+		log.Infof("interface %s already exists. Will reuse.", t.name)
+	} else if err != nil {
+		return nil, err
+	}
+
+	t.link = link
+
+	err = t.assignAddr()
+	if err != nil {
+		return nil, err
+	}
+
+	// todo do a discovery
+	log.Debugf("setting MTU: %d interface: %s", t.mtu, t.name)
+	err = netlink.LinkSetMTU(link, t.mtu)
+	if err != nil {
+		log.Errorf("error setting MTU on interface: %s", t.name)
+		return nil, err
+	}
+
+	configurer := newWGConfigurer(t.name)
+	err = configurer.configureInterface(t.key, t.wgPort)
+	if err != nil {
+		return nil, err
+	}
+	return configurer, nil
+}
+
+func (t *tunKernelDevice) Up() (*bind.UniversalUDPMuxDefault, error) {
+	if t.udpMux != nil {
+		return t.udpMux, nil
+	}
+
+	if t.link == nil {
+		return nil, fmt.Errorf("device is not ready yet")
+	}
+
+	log.Debugf("bringing up interface: %s", t.name)
+	err := netlink.LinkSetUp(t.link)
+	if err != nil {
+		log.Errorf("error bringing up interface: %s", t.name)
+		return nil, err
+	}
+
+	rawSock, err := sharedsock.Listen(t.wgPort, sharedsock.NewIncomingSTUNFilter())
+	if err != nil {
+		return nil, err
+	}
+	bindParams := bind.UniversalUDPMuxParams{
+		UDPConn: rawSock,
+		Net:     t.transportNet,
+	}
+	mux := bind.NewUniversalUDPMuxDefault(bindParams)
+	go mux.ReadFromConn(t.ctx)
+	t.udpMuxConn = rawSock
+	t.udpMux = mux
+
+	log.Debugf("device is ready to use: %s", t.name)
+	return t.udpMux, nil
+}
+
+func (t *tunKernelDevice) UpdateAddr(address WGAddress) error {
+	t.address = address
+	return t.assignAddr()
+}
+
+func (t *tunKernelDevice) Close() error {
+	if t.link == nil {
+		return nil
+	}
+
+	t.ctxCancel()
+
+	var closErr error
+	if err := t.link.Close(); err != nil {
+		log.Debugf("failed to close link: %s", err)
+		closErr = err
+	}
+
+	if t.udpMux != nil {
+		if err := t.udpMux.Close(); err != nil {
+			log.Debugf("failed to close udp mux: %s", err)
+			closErr = err
+		}
+
+		if err := t.udpMuxConn.Close(); err != nil {
+			log.Debugf("failed to close udp mux connection: %s", err)
+			closErr = err
+		}
+	}
+
+	return closErr
+}
+
+func (t *tunKernelDevice) WgAddress() WGAddress {
+	return t.address
+}
+
+func (t *tunKernelDevice) DeviceName() string {
+	return t.name
+}
+
+func (t *tunKernelDevice) Wrapper() *DeviceWrapper {
+	return nil
+}
+
+// assignAddr Adds IP address to the tunnel interface
+func (t *tunKernelDevice) assignAddr() error {
+	link := newWGLink(t.name)
+
+	//delete existing addresses
+	list, err := netlink.AddrList(link, 0)
+	if err != nil {
+		return err
+	}
+	if len(list) > 0 {
+		for _, a := range list {
+			addr := a
+			err = netlink.AddrDel(link, &addr)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	log.Debugf("adding address %s to interface: %s", t.address.String(), t.name)
+	addr, _ := netlink.ParseAddr(t.address.String())
+	err = netlink.AddrAdd(link, addr)
+	if os.IsExist(err) {
+		log.Infof("interface %s already has the address: %s", t.name, t.address.String())
+	} else if err != nil {
+		return err
+	}
+	// On linux, the link must be brought up
+	err = netlink.LinkSetUp(link)
+	return err
+}