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tailscale/wgengine/router_openbsd.go

264 lines
6.5 KiB
Go

// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package wgengine
import (
"bytes"
"fmt"
"io/ioutil"
"log"
"os"
"os/exec"
"path/filepath"
"strings"
"github.com/tailscale/wireguard-go/device"
"github.com/tailscale/wireguard-go/tun"
"github.com/tailscale/wireguard-go/wgcfg"
"tailscale.com/atomicfile"
"tailscale.com/types/logger"
)
// For now this router only supports the WireGuard userspace implementation.
// There is an experimental kernel version in the works for OpenBSD:
// https://git.zx2c4.com/wireguard-openbsd.
const DefaultTunName = "tun"
type openbsdRouter struct {
logf logger.Logf
tunname string
local wgcfg.CIDR
routes map[wgcfg.CIDR]struct{}
}
func newUserspaceRouter(logf logger.Logf, _ *device.Device, tundev tun.Device) (Router, error) {
tunname, err := tundev.Name()
if err != nil {
return nil, err
}
return &openbsdRouter{
logf: logf,
tunname: tunname,
}, nil
}
func cmd(args ...string) *exec.Cmd {
if len(args) == 0 {
log.Fatalf("exec.Cmd(%#v) invalid; need argv[0]\n", args)
}
return exec.Command(args[0], args[1:]...)
}
func (r *openbsdRouter) Up() error {
ifup := []string{"ifconfig", r.tunname, "up"}
if out, err := cmd(ifup...).CombinedOutput(); err != nil {
r.logf("running ifconfig failed: %v\n%s", err, out)
return err
}
return nil
}
func (r *openbsdRouter) SetRoutes(rs RouteSettings) error {
var errq error
if rs.LocalAddr != r.local {
if r.local != (wgcfg.CIDR{}) {
addrdel := []string{"ifconfig", r.tunname,
"inet", r.local.String(), "-alias"}
out, err := cmd(addrdel...).CombinedOutput()
if err != nil {
r.logf("addr del failed: %v: %v\n%s", addrdel, err, out)
if errq == nil {
errq = err
}
}
routedel := []string{"route", "-q", "-n",
"del", "-inet", r.local.String(),
"-iface", r.local.IP.String()}
if out, err := cmd(routedel...).CombinedOutput(); err != nil {
r.logf("route del failed: %v: %v\n%s", routedel, err, out)
if errq == nil {
errq = err
}
}
}
addradd := []string{"ifconfig", r.tunname,
"inet", rs.LocalAddr.String(), "alias"}
out, err := cmd(addradd...).CombinedOutput()
if err != nil {
r.logf("addr add failed: %v: %v\n%s", addradd, err, out)
if errq == nil {
errq = err
}
}
routeadd := []string{"route", "-q", "-n",
"add", "-inet", rs.LocalAddr.String(),
"-iface", rs.LocalAddr.IP.String()}
if out, err := cmd(routeadd...).CombinedOutput(); err != nil {
r.logf("route add failed: %v: %v\n%s", routeadd, err, out)
if errq == nil {
errq = err
}
}
}
newRoutes := make(map[wgcfg.CIDR]struct{})
for _, peer := range rs.Cfg.Peers {
for _, route := range peer.AllowedIPs {
newRoutes[route] = struct{}{}
}
}
for route := range r.routes {
if _, keep := newRoutes[route]; !keep {
net := route.IPNet()
nip := net.IP.Mask(net.Mask)
nstr := fmt.Sprintf("%v/%d", nip, route.Mask)
routedel := []string{"route", "-q", "-n",
"del", "-inet", nstr,
"-iface", rs.LocalAddr.IP.String()}
out, err := cmd(routedel...).CombinedOutput()
if err != nil {
r.logf("route del failed: %v: %v\n%s", routedel, err, out)
if errq == nil {
errq = err
}
}
}
}
for route := range newRoutes {
if _, exists := r.routes[route]; !exists {
net := route.IPNet()
nip := net.IP.Mask(net.Mask)
nstr := fmt.Sprintf("%v/%d", nip, route.Mask)
routeadd := []string{"route", "-q", "-n",
"add", "-inet", nstr,
"-iface", rs.LocalAddr.IP.String()}
out, err := cmd(routeadd...).CombinedOutput()
if err != nil {
r.logf("addr add failed: %v: %v\n%s", routeadd, err, out)
if errq == nil {
errq = err
}
}
}
}
r.local = rs.LocalAddr
r.routes = newRoutes
if err := r.replaceResolvConf(rs.DNS, rs.DNSDomains); err != nil {
errq = fmt.Errorf("replacing resolv.conf failed: %v", err)
}
return errq
}
func (r *openbsdRouter) Close() error {
out, err := cmd("ifconfig", r.tunname, "down").CombinedOutput()
if err != nil {
r.logf("running ifconfig failed: %v\n%s", err, out)
}
if err := r.restoreResolvConf(); err != nil {
r.logf("failed to restore system resolv.conf: %v", err)
}
return nil
}
const (
tsConf = "/etc/resolv.tailscale.conf"
backupConf = "/etc/resolv.pre-tailscale-backup.conf"
resolvConf = "/etc/resolv.conf"
)
func (r *openbsdRouter) replaceResolvConf(servers []wgcfg.IP, domains []string) error {
if len(servers) == 0 {
return r.restoreResolvConf()
}
// Write the tsConf file.
buf := new(bytes.Buffer)
fmt.Fprintf(buf, "# resolv.conf(5) file generated by tailscale\n")
fmt.Fprintf(buf, "# DO NOT EDIT THIS FILE BY HAND -- CHANGES WILL BE OVERWRITTEN\n\n")
for _, ns := range servers {
fmt.Fprintf(buf, "nameserver %s\n", ns)
}
if len(domains) > 0 {
fmt.Fprintf(buf, "search "+strings.Join(domains, " ")+"\n")
}
tf, err := ioutil.TempFile(filepath.Dir(tsConf), filepath.Base(tsConf)+".*")
if err != nil {
return err
}
tempName := tf.Name()
tf.Close()
if err := atomicfile.WriteFile(tempName, buf.Bytes(), 0644); err != nil {
return err
}
if err := os.Rename(tempName, tsConf); err != nil {
return err
}
if linkPath, err := os.Readlink(resolvConf); err != nil {
// Remove any old backup that may exist.
os.Remove(backupConf)
// Backup the existing /etc/resolv.conf file.
contents, err := ioutil.ReadFile(resolvConf)
if os.IsNotExist(err) {
// No existing /etc/resolv.conf file to backup.
// Nothing to do.
return nil
} else if err != nil {
return err
}
if err := atomicfile.WriteFile(backupConf, contents, 0644); err != nil {
return err
}
} else if linkPath != tsConf {
// Backup the existing symlink.
os.Remove(backupConf)
if err := os.Symlink(linkPath, backupConf); err != nil {
return err
}
} else {
// Nothing to do, resolvConf already points to tsConf.
return nil
}
os.Remove(resolvConf)
if err := os.Symlink(tsConf, resolvConf); err != nil {
return nil
}
return nil
}
func (r *openbsdRouter) restoreResolvConf() error {
if _, err := os.Stat(backupConf); err != nil {
if os.IsNotExist(err) {
return nil // No backup resolv.conf to restore.
}
return err
}
if ln, err := os.Readlink(resolvConf); err != nil {
return err
} else if ln != tsConf {
return fmt.Errorf("resolv.conf is not a symlink to %s", tsConf)
}
if err := os.Rename(backupConf, resolvConf); err != nil {
return err
}
os.Remove(tsConf) // Best effort removal.
return nil
}