nebula/overlay/tun_openbsd.go

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//go:build !e2e_testing
// +build !e2e_testing
package overlay
import (
"fmt"
"io"
"net"
"os"
"os/exec"
"regexp"
"strconv"
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"sync/atomic"
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"syscall"
"github.com/sirupsen/logrus"
"github.com/slackhq/nebula/cidr"
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"github.com/slackhq/nebula/config"
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"github.com/slackhq/nebula/iputil"
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"github.com/slackhq/nebula/util"
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)
type tun struct {
Device string
cidr *net.IPNet
MTU int
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Routes atomic.Pointer[[]Route]
routeTree atomic.Pointer[cidr.Tree4[iputil.VpnIp]]
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l *logrus.Logger
io.ReadWriteCloser
// cache out buffer since we need to prepend 4 bytes for tun metadata
out []byte
}
func (t *tun) Close() error {
if t.ReadWriteCloser != nil {
return t.ReadWriteCloser.Close()
}
return nil
}
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func newTunFromFd(_ *config.C, _ *logrus.Logger, _ int, _ *net.IPNet) (*tun, error) {
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return nil, fmt.Errorf("newTunFromFd not supported in OpenBSD")
}
var deviceNameRE = regexp.MustCompile(`^tun[0-9]+$`)
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func newTun(c *config.C, l *logrus.Logger, cidr *net.IPNet, _ bool) (*tun, error) {
deviceName := c.GetString("tun.dev", "")
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if deviceName == "" {
return nil, fmt.Errorf("a device name in the format of tunN must be specified")
}
if !deviceNameRE.MatchString(deviceName) {
return nil, fmt.Errorf("a device name in the format of tunN must be specified")
}
file, err := os.OpenFile("/dev/"+deviceName, os.O_RDWR, 0)
if err != nil {
return nil, err
}
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t := &tun{
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ReadWriteCloser: file,
Device: deviceName,
cidr: cidr,
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MTU: c.GetInt("tun.mtu", DefaultMTU),
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l: l,
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}
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 {
change, routes, err := getAllRoutesFromConfig(c, t.cidr, initial)
if err != nil {
return err
}
if !initial && !change {
return nil
}
routeTree, err := makeRouteTree(t.l, routes, false)
if err != nil {
return err
}
// 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 {
// Remove first, if the system removes a wanted route hopefully it will be re-added next
err := t.removeRoutes(findRemovedRoutes(routes, *oldRoutes))
if err != nil {
util.LogWithContextIfNeeded("Failed to remove routes", err, t.l)
}
// Ensure any routes we actually want are installed
err = t.addRoutes(true)
if err != nil {
// Catch any stray logs
util.LogWithContextIfNeeded("Failed to add routes", err, t.l)
}
}
return nil
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}
func (t *tun) Activate() error {
var err error
// TODO use syscalls instead of exec.Command
cmd := exec.Command("/sbin/ifconfig", t.Device, t.cidr.String(), t.cidr.IP.String())
t.l.Debug("command: ", cmd.String())
if err = cmd.Run(); err != nil {
return fmt.Errorf("failed to run 'ifconfig': %s", err)
}
cmd = exec.Command("/sbin/ifconfig", t.Device, "mtu", strconv.Itoa(t.MTU))
t.l.Debug("command: ", cmd.String())
if err = cmd.Run(); err != nil {
return fmt.Errorf("failed to run 'ifconfig': %s", err)
}
cmd = exec.Command("/sbin/route", "-n", "add", "-inet", t.cidr.String(), t.cidr.IP.String())
t.l.Debug("command: ", cmd.String())
if err = cmd.Run(); err != nil {
return fmt.Errorf("failed to run 'route add': %s", err)
}
// Unsafe path routes
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return t.addRoutes(false)
}
func (t *tun) RouteFor(ip iputil.VpnIp) iputil.VpnIp {
_, r := t.routeTree.Load().MostSpecificContains(ip)
return r
}
func (t *tun) addRoutes(logErrors bool) error {
routes := *t.Routes.Load()
for _, r := range routes {
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if r.Via == nil || !r.Install {
// We don't allow route MTUs so only install routes with a via
continue
}
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cmd := exec.Command("/sbin/route", "-n", "add", "-inet", r.Cidr.String(), t.cidr.IP.String())
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t.l.Debug("command: ", cmd.String())
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if err := cmd.Run(); err != nil {
retErr := util.NewContextualError("failed to run 'route add' for unsafe_route", map[string]interface{}{"route": r}, err)
if logErrors {
retErr.Log(t.l)
} else {
return retErr
}
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}
}
return nil
}
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func (t *tun) removeRoutes(routes []Route) error {
for _, r := range routes {
if !r.Install {
continue
}
cmd := exec.Command("/sbin/route", "-n", "delete", "-inet", r.Cidr.String(), t.cidr.IP.String())
t.l.Debug("command: ", cmd.String())
if err := cmd.Run(); err != nil {
t.l.WithError(err).WithField("route", r).Error("Failed to remove route")
} else {
t.l.WithField("route", r).Info("Removed route")
}
}
return nil
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}
func (t *tun) Cidr() *net.IPNet {
return t.cidr
}
func (t *tun) Name() string {
return t.Device
}
func (t *tun) NewMultiQueueReader() (io.ReadWriteCloser, error) {
return nil, fmt.Errorf("TODO: multiqueue not implemented for freebsd")
}
func (t *tun) Read(to []byte) (int, error) {
buf := make([]byte, len(to)+4)
n, err := t.ReadWriteCloser.Read(buf)
copy(to, buf[4:])
return n - 4, err
}
// Write is only valid for single threaded use
func (t *tun) Write(from []byte) (int, error) {
buf := t.out
if cap(buf) < len(from)+4 {
buf = make([]byte, len(from)+4)
t.out = buf
}
buf = buf[:len(from)+4]
if len(from) == 0 {
return 0, syscall.EIO
}
// Determine the IP Family for the NULL L2 Header
ipVer := from[0] >> 4
if ipVer == 4 {
buf[3] = syscall.AF_INET
} else if ipVer == 6 {
buf[3] = syscall.AF_INET6
} else {
return 0, fmt.Errorf("unable to determine IP version from packet")
}
copy(buf[4:], from)
n, err := t.ReadWriteCloser.Write(buf)
return n - 4, err
}