nebula/overlay/tun_linux.go

554 lines
12 KiB
Go

//go:build !android && !e2e_testing
// +build !android,!e2e_testing
package overlay
import (
"bytes"
"fmt"
"io"
"net"
"os"
"strings"
"sync/atomic"
"unsafe"
"github.com/sirupsen/logrus"
"github.com/slackhq/nebula/cidr"
"github.com/slackhq/nebula/config"
"github.com/slackhq/nebula/iputil"
"github.com/slackhq/nebula/util"
"github.com/vishvananda/netlink"
"golang.org/x/sys/unix"
)
type tun struct {
io.ReadWriteCloser
fd int
Device string
cidr *net.IPNet
MaxMTU int
DefaultMTU int
TXQueueLen int
deviceIndex int
ioctlFd uintptr
Routes atomic.Pointer[[]Route]
routeTree atomic.Pointer[cidr.Tree4[iputil.VpnIp]]
routeChan chan struct{}
useSystemRoutes bool
l *logrus.Logger
}
type ifReq struct {
Name [16]byte
Flags uint16
pad [8]byte
}
type ifreqAddr struct {
Name [16]byte
Addr unix.RawSockaddrInet4
pad [8]byte
}
type ifreqMTU struct {
Name [16]byte
MTU int32
pad [8]byte
}
type ifreqQLEN struct {
Name [16]byte
Value int32
pad [8]byte
}
func newTunFromFd(c *config.C, l *logrus.Logger, deviceFd int, cidr *net.IPNet) (*tun, error) {
file := os.NewFile(uintptr(deviceFd), "/dev/net/tun")
t, err := newTunGeneric(c, l, file, cidr)
if err != nil {
return nil, err
}
t.Device = "tun0"
return t, nil
}
func newTun(c *config.C, l *logrus.Logger, cidr *net.IPNet, multiqueue bool) (*tun, error) {
fd, err := unix.Open("/dev/net/tun", os.O_RDWR, 0)
if err != nil {
// If /dev/net/tun doesn't exist, try to create it (will happen in docker)
if os.IsNotExist(err) {
err = os.MkdirAll("/dev/net", 0755)
if err != nil {
return nil, fmt.Errorf("/dev/net/tun doesn't exist, failed to mkdir -p /dev/net: %w", err)
}
err = unix.Mknod("/dev/net/tun", unix.S_IFCHR|0600, int(unix.Mkdev(10, 200)))
if err != nil {
return nil, fmt.Errorf("failed to create /dev/net/tun: %w", err)
}
fd, err = unix.Open("/dev/net/tun", os.O_RDWR, 0)
if err != nil {
return nil, fmt.Errorf("created /dev/net/tun, but still failed: %w", err)
}
} else {
return nil, err
}
}
var req ifReq
req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI)
if multiqueue {
req.Flags |= unix.IFF_MULTI_QUEUE
}
copy(req.Name[:], c.GetString("tun.dev", ""))
if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
return nil, err
}
name := strings.Trim(string(req.Name[:]), "\x00")
file := os.NewFile(uintptr(fd), "/dev/net/tun")
t, err := newTunGeneric(c, l, file, cidr)
if err != nil {
return nil, err
}
t.Device = name
return t, nil
}
func newTunGeneric(c *config.C, l *logrus.Logger, file *os.File, cidr *net.IPNet) (*tun, error) {
t := &tun{
ReadWriteCloser: file,
fd: int(file.Fd()),
cidr: cidr,
TXQueueLen: c.GetInt("tun.tx_queue", 500),
useSystemRoutes: c.GetBool("tun.use_system_route_table", false),
l: l,
}
err := t.reload(c, true)
if err != nil {
return nil, err
}
c.RegisterReloadCallback(func(c *config.C) {
err := t.reload(c, false)
if err != nil {
util.LogWithContextIfNeeded("failed to reload tun device", err, t.l)
}
})
return t, nil
}
func (t *tun) reload(c *config.C, initial bool) error {
routeChange, routes, err := getAllRoutesFromConfig(c, t.cidr, initial)
if err != nil {
return err
}
if !initial && !routeChange && !c.HasChanged("tun.mtu") {
return nil
}
routeTree, err := makeRouteTree(t.l, routes, true)
if err != nil {
return err
}
oldDefaultMTU := t.DefaultMTU
oldMaxMTU := t.MaxMTU
newDefaultMTU := c.GetInt("tun.mtu", DefaultMTU)
newMaxMTU := newDefaultMTU
for i, r := range routes {
if r.MTU == 0 {
routes[i].MTU = newDefaultMTU
}
if r.MTU > t.MaxMTU {
newMaxMTU = r.MTU
}
}
t.MaxMTU = newMaxMTU
t.DefaultMTU = newDefaultMTU
// Teach nebula how to handle the routes before establishing them in the system table
oldRoutes := t.Routes.Swap(&routes)
t.routeTree.Store(routeTree)
if !initial {
if oldMaxMTU != newMaxMTU {
t.setMTU()
t.l.Infof("Set max MTU to %v was %v", t.MaxMTU, oldMaxMTU)
}
if oldDefaultMTU != newDefaultMTU {
err := t.setDefaultRoute()
if err != nil {
t.l.Warn(err)
} else {
t.l.Infof("Set default MTU to %v was %v", t.DefaultMTU, oldDefaultMTU)
}
}
// Remove first, if the system removes a wanted route hopefully it will be re-added next
t.removeRoutes(findRemovedRoutes(routes, *oldRoutes))
// Ensure any routes we actually want are installed
err = t.addRoutes(true)
if err != nil {
// This should never be called since addRoutes should log its own errors in a reload condition
util.LogWithContextIfNeeded("Failed to refresh routes", err, t.l)
}
}
return nil
}
func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
fd, err := unix.Open("/dev/net/tun", os.O_RDWR, 0)
if err != nil {
return nil, err
}
var req ifReq
req.Flags = uint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_MULTI_QUEUE)
copy(req.Name[:], t.Device)
if err = ioctl(uintptr(fd), uintptr(unix.TUNSETIFF), uintptr(unsafe.Pointer(&req))); err != nil {
return nil, err
}
file := os.NewFile(uintptr(fd), "/dev/net/tun")
return file, nil
}
func (t *tun) RouteFor(ip iputil.VpnIp) iputil.VpnIp {
_, r := t.routeTree.Load().MostSpecificContains(ip)
return r
}
func (t *tun) Write(b []byte) (int, error) {
var nn int
max := len(b)
for {
n, err := unix.Write(t.fd, b[nn:max])
if n > 0 {
nn += n
}
if nn == len(b) {
return nn, err
}
if err != nil {
return nn, err
}
if n == 0 {
return nn, io.ErrUnexpectedEOF
}
}
}
func (t *tun) deviceBytes() (o [16]byte) {
for i, c := range t.Device {
o[i] = byte(c)
}
return
}
func (t *tun) Activate() error {
devName := t.deviceBytes()
if t.useSystemRoutes {
t.watchRoutes()
}
var addr, mask [4]byte
copy(addr[:], t.cidr.IP.To4())
copy(mask[:], t.cidr.Mask)
s, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
unix.IPPROTO_IP,
)
if err != nil {
return err
}
t.ioctlFd = uintptr(s)
ifra := ifreqAddr{
Name: devName,
Addr: unix.RawSockaddrInet4{
Family: unix.AF_INET,
Addr: addr,
},
}
// Set the device ip address
if err = ioctl(t.ioctlFd, unix.SIOCSIFADDR, uintptr(unsafe.Pointer(&ifra))); err != nil {
return fmt.Errorf("failed to set tun address: %s", err)
}
// Set the device network
ifra.Addr.Addr = mask
if err = ioctl(t.ioctlFd, unix.SIOCSIFNETMASK, uintptr(unsafe.Pointer(&ifra))); err != nil {
return fmt.Errorf("failed to set tun netmask: %s", err)
}
// Set the device name
ifrf := ifReq{Name: devName}
if err = ioctl(t.ioctlFd, unix.SIOCGIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil {
return fmt.Errorf("failed to set tun device name: %s", err)
}
// Setup our default MTU
t.setMTU()
// Set the transmit queue length
ifrq := ifreqQLEN{Name: devName, Value: int32(t.TXQueueLen)}
if err = ioctl(t.ioctlFd, unix.SIOCSIFTXQLEN, uintptr(unsafe.Pointer(&ifrq))); err != nil {
// If we can't set the queue length nebula will still work but it may lead to packet loss
t.l.WithError(err).Error("Failed to set tun tx queue length")
}
// Bring up the interface
ifrf.Flags = ifrf.Flags | unix.IFF_UP
if err = ioctl(t.ioctlFd, unix.SIOCSIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil {
return fmt.Errorf("failed to bring the tun device up: %s", err)
}
link, err := netlink.LinkByName(t.Device)
if err != nil {
return fmt.Errorf("failed to get tun device link: %s", err)
}
t.deviceIndex = link.Attrs().Index
if err = t.setDefaultRoute(); err != nil {
return err
}
// Set the routes
if err = t.addRoutes(false); err != nil {
return err
}
// Run the interface
ifrf.Flags = ifrf.Flags | unix.IFF_UP | unix.IFF_RUNNING
if err = ioctl(t.ioctlFd, unix.SIOCSIFFLAGS, uintptr(unsafe.Pointer(&ifrf))); err != nil {
return fmt.Errorf("failed to run tun device: %s", err)
}
return nil
}
func (t *tun) setMTU() {
// Set the MTU on the device
ifm := ifreqMTU{Name: t.deviceBytes(), MTU: int32(t.MaxMTU)}
if err := ioctl(t.ioctlFd, unix.SIOCSIFMTU, uintptr(unsafe.Pointer(&ifm))); err != nil {
// This is currently a non fatal condition because the route table must have the MTU set appropriately as well
t.l.WithError(err).Error("Failed to set tun mtu")
}
}
func (t *tun) setDefaultRoute() error {
// Default route
dr := &net.IPNet{IP: t.cidr.IP.Mask(t.cidr.Mask), Mask: t.cidr.Mask}
nr := netlink.Route{
LinkIndex: t.deviceIndex,
Dst: dr,
MTU: t.DefaultMTU,
AdvMSS: t.advMSS(Route{}),
Scope: unix.RT_SCOPE_LINK,
Src: t.cidr.IP,
Protocol: unix.RTPROT_KERNEL,
Table: unix.RT_TABLE_MAIN,
Type: unix.RTN_UNICAST,
}
err := netlink.RouteReplace(&nr)
if err != nil {
return fmt.Errorf("failed to set mtu %v on the default route %v; %v", t.DefaultMTU, dr, err)
}
return nil
}
func (t *tun) addRoutes(logErrors bool) error {
// Path routes
routes := *t.Routes.Load()
for _, r := range routes {
if !r.Install {
continue
}
nr := netlink.Route{
LinkIndex: t.deviceIndex,
Dst: r.Cidr,
MTU: r.MTU,
AdvMSS: t.advMSS(r),
Scope: unix.RT_SCOPE_LINK,
}
if r.Metric > 0 {
nr.Priority = r.Metric
}
err := netlink.RouteReplace(&nr)
if err != nil {
retErr := util.NewContextualError("Failed to add route", map[string]interface{}{"route": r}, err)
if logErrors {
retErr.Log(t.l)
} else {
return retErr
}
} else {
t.l.WithField("route", r).Info("Added route")
}
}
return nil
}
func (t *tun) removeRoutes(routes []Route) {
for _, r := range routes {
if !r.Install {
continue
}
nr := netlink.Route{
LinkIndex: t.deviceIndex,
Dst: r.Cidr,
MTU: r.MTU,
AdvMSS: t.advMSS(r),
Scope: unix.RT_SCOPE_LINK,
}
if r.Metric > 0 {
nr.Priority = r.Metric
}
err := netlink.RouteDel(&nr)
if err != nil {
t.l.WithError(err).WithField("route", r).Error("Failed to remove route")
} else {
t.l.WithField("route", r).Info("Removed route")
}
}
}
func (t *tun) Cidr() *net.IPNet {
return t.cidr
}
func (t *tun) Name() string {
return t.Device
}
func (t *tun) advMSS(r Route) int {
mtu := r.MTU
if r.MTU == 0 {
mtu = t.DefaultMTU
}
// We only need to set advmss if the route MTU does not match the device MTU
if mtu != t.MaxMTU {
return mtu - 40
}
return 0
}
func (t *tun) watchRoutes() {
rch := make(chan netlink.RouteUpdate)
doneChan := make(chan struct{})
if err := netlink.RouteSubscribe(rch, doneChan); err != nil {
t.l.WithError(err).Errorf("failed to subscribe to system route changes")
return
}
t.routeChan = doneChan
go func() {
for {
select {
case r := <-rch:
t.updateRoutes(r)
case <-doneChan:
// netlink.RouteSubscriber will close the rch for us
return
}
}
}()
}
func (t *tun) updateRoutes(r netlink.RouteUpdate) {
if r.Gw == nil {
// Not a gateway route, ignore
t.l.WithField("route", r).Debug("Ignoring route update, not a gateway route")
return
}
if !t.cidr.Contains(r.Gw) {
// Gateway isn't in our overlay network, ignore
t.l.WithField("route", r).Debug("Ignoring route update, not in our network")
return
}
if x := r.Dst.IP.To4(); x == nil {
// Nebula only handles ipv4 on the overlay currently
t.l.WithField("route", r).Debug("Ignoring route update, destination is not ipv4")
return
}
newTree := cidr.NewTree4[iputil.VpnIp]()
if r.Type == unix.RTM_NEWROUTE {
for _, oldR := range t.routeTree.Load().List() {
newTree.AddCIDR(oldR.CIDR, oldR.Value)
}
t.l.WithField("destination", r.Dst).WithField("via", r.Gw).Info("Adding route")
newTree.AddCIDR(r.Dst, iputil.Ip2VpnIp(r.Gw))
} else {
gw := iputil.Ip2VpnIp(r.Gw)
for _, oldR := range t.routeTree.Load().List() {
if bytes.Equal(oldR.CIDR.IP, r.Dst.IP) && bytes.Equal(oldR.CIDR.Mask, r.Dst.Mask) && oldR.Value == gw {
// This is the record to delete
t.l.WithField("destination", r.Dst).WithField("via", r.Gw).Info("Removing route")
continue
}
newTree.AddCIDR(oldR.CIDR, oldR.Value)
}
}
t.routeTree.Store(newTree)
}
func (t *tun) Close() error {
if t.routeChan != nil {
close(t.routeChan)
}
if t.ReadWriteCloser != nil {
t.ReadWriteCloser.Close()
}
if t.ioctlFd > 0 {
os.NewFile(t.ioctlFd, "ioctlFd").Close()
}
return nil
}