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wgengine/router: support multiple levels of netfilter involvement.

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Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson 2020-05-13 22:35:22 +00:00 committed by Dave Anderson
parent cff53c6e6d
commit 292606a975
6 changed files with 493 additions and 240 deletions
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28
cmd/tailscale/tailscale.go
View File

@ -54,10 +54,14 @@ func main() {
upf.BoolVar(&upArgs.acceptRoutes, "accept-routes", false, "accept routes advertised by other Tailscale nodes")
upf.BoolVar(&upArgs.noSingleRoutes, "no-single-routes", false, "don't install routes to single nodes")
upf.BoolVar(&upArgs.shieldsUp, "shields-up", false, "don't allow incoming connections")
upf.StringVar(&upArgs.advertiseRoutes, "advertise-routes", "", "routes to advertise to other nodes (comma-separated, e.g. 10.0.0.0/8,192.168.0.0/24)")
upf.StringVar(&upArgs.advertiseTags, "advertise-tags", "", "ACL tags to request (comma-separated, e.g. eng,montreal,ssh)")
upf.BoolVar(&upArgs.noSNAT, "no-snat", false, "disable SNAT of traffic to local routes advertised with -advertise-routes")
upf.StringVar(&upArgs.authKey, "authkey", "", "node authorization key")
if runtime.GOOS == "linux" {
upf.StringVar(&upArgs.advertiseRoutes, "advertise-routes", "", "routes to advertise to other nodes (comma-separated, e.g. 10.0.0.0/8,192.168.0.0/24)")
upf.BoolVar(&upArgs.noSNAT, "no-snat", false, "disable SNAT of traffic to local routes advertised with -advertise-routes")
upf.BoolVar(&upArgs.noNetfilterCalls, "no-netfilter-calls", false, "don't call Tailscale netfilter chains from the main netfilter chains")
upf.BoolVar(&upArgs.noNetfilter, "no-netfilter", false, "disable all netfilter rule management")
}
upCmd := &ffcli.Command{
Name: "up",
ShortUsage: "up [flags]",
@ -100,14 +104,16 @@ change in the future.
}
var upArgs struct {
server string
acceptRoutes bool
noSingleRoutes bool
shieldsUp bool
advertiseRoutes string
advertiseTags string
noSNAT bool
authKey string
server string
acceptRoutes bool
noSingleRoutes bool
shieldsUp bool
advertiseRoutes string
advertiseTags string
noSNAT bool
noNetfilterCalls bool
noNetfilter bool
authKey string
}
// parseIPOrCIDR parses an IP address or a CIDR prefix. If the input
@ -194,6 +200,8 @@ func runUp(ctx context.Context, args []string) error {
prefs.AdvertiseRoutes = routes
prefs.AdvertiseTags = tags
prefs.NoSNAT = upArgs.noSNAT
prefs.NoNetfilter = upArgs.noNetfilter
prefs.NoNetfilterCalls = upArgs.noNetfilterCalls
c, bc, ctx, cancel := connect(ctx)
defer cancel()

18
ipn/local.go
View File

@ -734,11 +734,19 @@ func routerConfig(cfg *wgcfg.Config, prefs *Prefs, dnsDomains []string) *router.
}
rs := &router.Config{
LocalAddrs: wgCIDRToNetaddr(addrs),
DNS: wgIPToNetaddr(cfg.DNS),
DNSDomains: dnsDomains,
SubnetRoutes: wgCIDRToNetaddr(prefs.AdvertiseRoutes),
NoSNAT: prefs.NoSNAT,
LocalAddrs: wgCIDRToNetaddr(addrs),
DNS: wgIPToNetaddr(cfg.DNS),
DNSDomains: dnsDomains,
SubnetRoutes: wgCIDRToNetaddr(prefs.AdvertiseRoutes),
SNATSubnetRoutes: !prefs.NoSNAT,
}
switch {
case prefs.NoNetfilter:
rs.NetfilterMode = router.NetfilterOff
case prefs.NoNetfilterCalls:
rs.NetfilterMode = router.NetfilterNoDivert
default:
rs.NetfilterMode = router.NetfilterOn
}
for _, peer := range cfg.Peers {

46
ipn/prefs.go
View File

@ -44,24 +44,12 @@ type Prefs struct {
// use the packet filter as provided. If true, we block incoming
// connections.
ShieldsUp bool
// AdvertiseRoutes specifies CIDR prefixes to advertise into the
// Tailscale network as reachable through the current node.
AdvertiseRoutes []wgcfg.CIDR
// AdvertiseTags specifies groups that this node wants to join, for
// purposes of ACL enforcement. These can be referenced from the ACL
// security policy. Note that advertising a tag doesn't guarantee that
// the control server will allow you to take on the rights for that
// tag.
AdvertiseTags []string
// NoSNAT specifies whether to source NAT traffic going to
// destinations in AdvertiseRoutes. The default is to apply source
// NAT, which makes the traffic appear to come from the router
// machine rather than the peer's Tailscale IP.
//
// Disabling SNAT requires additional manual configuration in your
// network to route Tailscale traffic back to the subnet relay
// machine.
NoSNAT bool
// NotepadURLs is a debugging setting that opens OAuth URLs in
// notepad.exe on Windows, rather than loading them in a browser.
@ -74,6 +62,34 @@ type Prefs struct {
// DisableDERP prevents DERP from being used.
DisableDERP bool
// The following block of options only have an effect on Linux.
// AdvertiseRoutes specifies CIDR prefixes to advertise into the
// Tailscale network as reachable through the current
// node.
AdvertiseRoutes []wgcfg.CIDR
// NoSNAT specifies whether to source NAT traffic going to
// destinations in AdvertiseRoutes. The default is to apply source
// NAT, which makes the traffic appear to come from the router
// machine rather than the peer's Tailscale IP.
//
// Disabling SNAT requires additional manual configuration in your
// network to route Tailscale traffic back to the subnet relay
// machine.
//
// Linux-only.
NoSNAT bool
// NoNetfilter, if set, disables all management of firewall rules
// for Tailscale traffic. The resulting configuration is not
// secure, and it is the user's responsibility to correct that.
NoNetfilter bool
// NoNetfilterDivert, if set, disables calling Tailscale netfilter
// chains from the main netfilter chains, but still manages the
// contents of the Tailscale chains. The resulting configuration
// is not secure, and it is the user's responsibility to insert
// calls to Tailscale's chains at the right place.
NoNetfilterCalls bool
// The Persist field is named 'Config' in the file for backward
// compatibility with earlier versions.
// TODO(apenwarr): We should move this out of here, it's not a pref.
@ -92,9 +108,9 @@ func (p *Prefs) Pretty() string {
} else {
pp = "Persist=nil"
}
return fmt.Sprintf("Prefs{ra=%v mesh=%v dns=%v want=%v notepad=%v derp=%v shields=%v routes=%v snat=%v %v}",
return fmt.Sprintf("Prefs{ra=%v mesh=%v dns=%v want=%v notepad=%v derp=%v shields=%v routes=%v snat=%v nf=%v nfd=%v %v}",
p.RouteAll, p.AllowSingleHosts, p.CorpDNS, p.WantRunning,
p.NotepadURLs, !p.DisableDERP, p.ShieldsUp, p.AdvertiseRoutes, !p.NoSNAT, pp)
p.NotepadURLs, !p.DisableDERP, p.ShieldsUp, p.AdvertiseRoutes, !p.NoSNAT, !p.NoNetfilter, !p.NoNetfilterCalls, pp)
}
func (p *Prefs) ToBytes() []byte {
@ -123,6 +139,8 @@ func (p *Prefs) Equals(p2 *Prefs) bool {
p.DisableDERP == p2.DisableDERP &&
p.ShieldsUp == p2.ShieldsUp &&
p.NoSNAT == p2.NoSNAT &&
p.NoNetfilter == p2.NoNetfilter &&
p.NoNetfilterCalls == p2.NoNetfilterCalls &&
compareIPNets(p.AdvertiseRoutes, p2.AdvertiseRoutes) &&
compareStrings(p.AdvertiseTags, p2.AdvertiseTags) &&
p.Persist.Equals(p2.Persist)

24
ipn/prefs_test.go
View File

@ -23,7 +23,7 @@ func fieldsOf(t reflect.Type) (fields []string) {
func TestPrefsEqual(t *testing.T) {
tstest.PanicOnLog()
prefsHandles := []string{"ControlURL", "RouteAll", "AllowSingleHosts", "CorpDNS", "WantRunning", "ShieldsUp", "AdvertiseRoutes", "AdvertiseTags", "NoSNAT", "NotepadURLs", "DisableDERP", "Persist"}
prefsHandles := []string{"ControlURL", "RouteAll", "AllowSingleHosts", "CorpDNS", "WantRunning", "ShieldsUp", "AdvertiseTags", "NotepadURLs", "DisableDERP", "AdvertiseRoutes", "NoSNAT", "NoNetfilter", "NoNetfilterCalls", "Persist"}
if have := fieldsOf(reflect.TypeOf(Prefs{})); !reflect.DeepEqual(have, prefsHandles) {
t.Errorf("Prefs.Equal check might be out of sync\nfields: %q\nhandled: %q\n",
have, prefsHandles)
@ -173,6 +173,28 @@ func TestPrefsEqual(t *testing.T) {
true,
},
{
&Prefs{NoNetfilter: true},
&Prefs{NoNetfilter: false},
false,
},
{
&Prefs{NoNetfilter: true},
&Prefs{NoNetfilter: true},
true,
},
{
&Prefs{NoNetfilterCalls: true},
&Prefs{NoNetfilterCalls: false},
false,
},
{
&Prefs{NoNetfilterCalls: true},
&Prefs{NoNetfilterCalls: true},
true,
},
{
&Prefs{Persist: &controlclient.Persist{}},
&Prefs{Persist: &controlclient.Persist{LoginName: "dave"}},

30
wgengine/router/router.go
View File

@ -35,22 +35,30 @@ func New(logf logger.Logf, wgdev *device.Device, tundev tun.Device) (Router, err
return newUserspaceRouter(logf, wgdev, tundev)
}
type NetfilterMode int
const (
NetfilterOff NetfilterMode = iota // remove all tailscale netfilter state
NetfilterNoDivert // manage tailscale chains, but don't call them
NetfilterOn // manage tailscale chains and call them from main chains
)
// Config is the subset of Tailscale configuration that is relevant to
// the OS's network stack.
type Config struct {
LocalAddrs []netaddr.IPPrefix
DNS []netaddr.IP
DNSDomains []string
Routes []netaddr.IPPrefix // routes to point into the Tailscale interface
SubnetRoutes []netaddr.IPPrefix // subnets being advertised to other Tailscale nodes
NoSNAT bool // don't SNAT traffic to local subnets
LocalAddrs []netaddr.IPPrefix
DNS []netaddr.IP
DNSDomains []string
Routes []netaddr.IPPrefix // routes to point into the Tailscale interface
// Linux-only things below, ignored on other platforms.
SubnetRoutes []netaddr.IPPrefix // subnets being advertised to other Tailscale nodes
SNATSubnetRoutes bool // SNAT traffic to local subnets
NetfilterMode NetfilterMode // how much to manage netfilter rules
}
// shutdownConfig is a routing configuration that removes all router
// state from the OS. It's the config used when callers pass in a nil
// Config.
var shutdownConfig = Config{
// TODO(danderson): set more things in here to disable all
// firewall rules and routing overrides when nil.
NoSNAT: true,
}
var shutdownConfig = Config{}

587
wgengine/router/router_linux.go
View File

@ -48,13 +48,19 @@ const (
tailscaleBypassMark = "0x20000/0x20000"
)
// chromeOSVMRange is the subset of the CGNAT IPv4 range used by
// ChromeOS to interconnect the host OS to containers and VMs. We
// avoid allocating Tailscale IPs from it, to avoid conflicts.
const chromeOSVMRange = "100.115.92.0/23"
type linuxRouter struct {
logf func(fmt string, args ...interface{})
tunname string
addrs map[netaddr.IPPrefix]bool
routes map[netaddr.IPPrefix]bool
subnetRoutes map[netaddr.IPPrefix]bool
noSNAT bool
logf func(fmt string, args ...interface{})
tunname string
addrs map[netaddr.IPPrefix]bool
routes map[netaddr.IPPrefix]bool
subnetRoutes map[netaddr.IPPrefix]bool
snatSubnetRoutes bool
netfilterMode NetfilterMode
ipt4 *iptables.IPTables
}
@ -71,10 +77,10 @@ func newUserspaceRouter(logf logger.Logf, _ *device.Device, tunDev tun.Device) (
}
return &linuxRouter{
logf: logf,
tunname: tunname,
noSNAT: true,
ipt4: ipt4,
logf: logf,
tunname: tunname,
netfilterMode: NetfilterOff,
ipt4: ipt4,
}, nil
}
@ -92,12 +98,16 @@ func cmd(args ...string) error {
}
func (r *linuxRouter) Up() error {
if err := r.deleteLegacyNetfilter(); err != nil {
if err := r.delLegacyNetfilter(); err != nil {
return err
}
if err := r.addBaseNetfilter4(); err != nil {
if err := r.delNetfilterHooks(); err != nil {
return err
}
if err := r.delNetfilterBase(); err != nil {
return err
}
if err := r.addBypassRule(); err != nil {
return err
}
@ -115,7 +125,10 @@ func (r *linuxRouter) down() error {
if err := r.delBypassRule(); err != nil {
return err
}
if err := r.delNetfilter4(); err != nil {
if err := r.delNetfilterHooks(); err != nil {
return err
}
if err := r.delNetfilterBase(); err != nil {
return err
}
@ -146,84 +159,129 @@ func (r *linuxRouter) Set(cfg *Config) error {
cfg = &shutdownConfig
}
// cidrDiff calls add and del as needed to make the set of prefixes in
// old and new match. Returns a map version of new, and the first
// error encountered while reconfiguring, if any.
cidrDiff := func(kind string, old map[netaddr.IPPrefix]bool, new []netaddr.IPPrefix, add, del func(netaddr.IPPrefix) error) (map[netaddr.IPPrefix]bool, error) {
var (
ret = make(map[netaddr.IPPrefix]bool, len(new))
errq error
)
for _, cidr := range new {
ret[cidr] = true
}
for cidr := range old {
if ret[cidr] {
continue
}
if err := del(cidr); err != nil {
r.logf("%s del failed: %v", kind, err)
if errq == nil {
errq = err
}
}
}
for cidr := range ret {
if old[cidr] {
continue
}
if err := add(cidr); err != nil {
r.logf("%s add failed: %v", kind, err)
if errq == nil {
errq = err
}
}
}
return ret, errq
if err := r.setNetfilterMode(cfg.NetfilterMode); err != nil {
return err
}
var errq error
newAddrs, err := cidrDiff("addr", r.addrs, cfg.LocalAddrs, r.addAddress, r.delAddress, r.logf)
if err != nil {
return err
}
r.addrs = newAddrs
newAddrs, err := cidrDiff("addr", r.addrs, cfg.LocalAddrs, r.addAddress, r.delAddress)
if err != nil && errq == nil {
errq = err
newRoutes, err := cidrDiff("route", r.routes, cfg.Routes, r.addRoute, r.delRoute, r.logf)
if err != nil {
return err
}
newRoutes, err := cidrDiff("route", r.routes, cfg.Routes, r.addRoute, r.delRoute)
if err != nil && errq == nil {
errq = err
}
newSubnetRoutes, err := cidrDiff("subnet rule", r.subnetRoutes, cfg.SubnetRoutes, r.addSubnetRule, r.delSubnetRule)
if err != nil && errq == nil {
errq = err
r.routes = newRoutes
newSubnetRoutes, err := cidrDiff("subnet rule", r.subnetRoutes, cfg.SubnetRoutes, r.addSubnetRule, r.delSubnetRule, r.logf)
if err != nil {
return err
}
r.subnetRoutes = newSubnetRoutes
switch {
case cfg.NoSNAT == r.noSNAT:
case cfg.SNATSubnetRoutes == r.snatSubnetRoutes:
// state already correct, nothing to do.
case cfg.NoSNAT:
if err := r.delSNATRule(); err != nil && errq == nil {
errq = err
case cfg.SNATSubnetRoutes:
if err := r.addSNATRule(); err != nil {
return err
}
default:
if err := r.addSNATRule(); err != nil && errq == nil {
errq = err
if err := r.delSNATRule(); err != nil {
return err
}
}
r.addrs = newAddrs
r.routes = newRoutes
r.subnetRoutes = newSubnetRoutes
r.noSNAT = cfg.NoSNAT
r.snatSubnetRoutes = cfg.SNATSubnetRoutes
// TODO: this:
if false {
if err := r.replaceResolvConf(cfg.DNS, cfg.DNSDomains); err != nil {
errq = fmt.Errorf("replacing resolv.conf failed: %v", err)
return fmt.Errorf("replacing resolv.conf failed: %v", err)
}
}
return errq
return nil
}
// setNetfilterMode switches the router to the given netfilter
// mode. Netfilter state is created or deleted appropriately to
// reflect the new mode, and r.snatSubnetRoutes is updated to reflect
// the current state of subnet SNATing.
func (r *linuxRouter) setNetfilterMode(mode NetfilterMode) error {
if r.netfilterMode == mode {
return nil
}
// Depending on the netfilter mode we switch from and to, we may
// have created the Tailscale netfilter chains. If so, we have to
// go back through existing router state, and add the netfilter
// rules for that state.
//
// This bool keeps track of whether the current state transition
// is one that requires adding rules of existing state.
reprocess := false
switch mode {
case NetfilterOff:
if err := r.delNetfilterHooks(); err != nil {
return err
}
if err := r.delNetfilterBase(); err != nil {
return err
}
r.snatSubnetRoutes = false
case NetfilterNoDivert:
switch r.netfilterMode {
case NetfilterOff:
reprocess = true
if err := r.addNetfilterBase(); err != nil {
return err
}
r.snatSubnetRoutes = false
case NetfilterOn:
if err := r.delNetfilterHooks(); err != nil {
return err
}
}
case NetfilterOn:
switch r.netfilterMode {
case NetfilterOff:
reprocess = true
if err := r.addNetfilterBase(); err != nil {
return err
}
if err := r.addNetfilterHooks(); err != nil {
return err
}
r.snatSubnetRoutes = false
case NetfilterNoDivert:
if err := r.addNetfilterHooks(); err != nil {
return err
}
}
default:
panic("unhandled netfilter mode")
}
r.netfilterMode = mode
if !reprocess {
return nil
}
for cidr := range r.addrs {
if err := r.addLoopbackRule(cidr.IP); err != nil {
return err
}
}
for cidr := range r.subnetRoutes {
if err := r.addSubnetRule(cidr); err != nil {
return err
}
}
return nil
}
const (
@ -322,38 +380,54 @@ func (r *linuxRouter) restoreResolvConf() error {
return nil
}
// addAddress adds an IP/mask to the tunnel interface, and firewall
// rules to permit loopback traffic. Fails if the address is already
// assigned to the interface, or if the addition fails.
// addAddress adds an IP/mask to the tunnel interface. Fails if the
// address is already assigned to the interface, or if the addition
// fails.
func (r *linuxRouter) addAddress(addr netaddr.IPPrefix) error {
if err := cmd("ip", "addr", "add", addr.String(), "dev", r.tunname); err != nil {
return err
return fmt.Errorf("adding address %q to tunnel interface: %v", addr, err)
}
if err := r.ipt4.Insert("filter", "ts-input", 1, "-i", "lo", "-s", addr.IP.String(), "-j", "ACCEPT"); err != nil {
if err := r.addLoopbackRule(addr.IP); err != nil {
return err
}
return nil
}
// delAddress removes an IP/mask from the tunnel interface, and
// firewall rules permitting loopback traffic. Fails if the address is
// not assigned to the interface, or if the removal fails.
// delAddress removes an IP/mask from the tunnel interface. Fails if
// the address is not assigned to the interface, or if the removal
// fails.
func (r *linuxRouter) delAddress(addr netaddr.IPPrefix) error {
if err := r.ipt4.Delete("filter", "ts-input", "-i", "lo", "-s", addr.IP.String(), "-j", "ACCEPT"); err != nil {
if err := r.delLoopbackRule(addr.IP); err != nil {
return err
}
if err := cmd("ip", "addr", "del", addr.String(), "dev", r.tunname); err != nil {
return err
return fmt.Errorf("deleting address %q from tunnel interface: %v", addr, err)
}
return nil
}
// normalizeCIDR returns cidr as an ip/mask string, with the host bits
// of the IP address zeroed out.
func normalizeCIDR(cidr netaddr.IPPrefix) string {
ncidr := cidr.IPNet()
nip := ncidr.IP.Mask(ncidr.Mask)
return fmt.Sprintf("%s/%d", nip, cidr.Bits)
// addLoopbackRule adds a firewall rule to permit loopback traffic to
// a local Tailscale IP.
func (r *linuxRouter) addLoopbackRule(addr netaddr.IP) error {
if r.netfilterMode == NetfilterOff {
return nil
}
if err := r.ipt4.Insert("filter", "ts-input", 1, "-i", "lo", "-s", addr.String(), "-j", "ACCEPT"); err != nil {
return fmt.Errorf("adding loopback allow rule for %q: %v", addr, err)
}
return nil
}
// delLoopbackRule removes the firewall rule permitting loopback
// traffic to a Tailscale IP.
func (r *linuxRouter) delLoopbackRule(addr netaddr.IP) error {
if r.netfilterMode == NetfilterOff {
return nil
}
if err := r.ipt4.Delete("filter", "ts-input", "-i", "lo", "-s", addr.String(), "-j", "ACCEPT"); err != nil {
return fmt.Errorf("deleting loopback allow rule for %q: %v", addr, err)
}
return nil
}
// addRoute adds a route for cidr, pointing to the tunnel
@ -371,9 +445,12 @@ func (r *linuxRouter) delRoute(cidr netaddr.IPPrefix) error {
}
// addSubnetRule adds a netfilter rule that allows traffic to flow
// from Tailscale to cidr. Fails if the rule already exists, or if
// adding the route fails.
// from Tailscale to cidr.
func (r *linuxRouter) addSubnetRule(cidr netaddr.IPPrefix) error {
if r.netfilterMode == NetfilterOff {
return nil
}
if err := r.ipt4.Insert("filter", "ts-forward", 1, "-i", r.tunname, "-d", normalizeCIDR(cidr), "-j", "MARK", "--set-mark", tailscaleSubnetRouteMark); err != nil {
return fmt.Errorf("adding subnet mark rule for %q: %v", cidr, err)
}
@ -384,9 +461,13 @@ func (r *linuxRouter) addSubnetRule(cidr netaddr.IPPrefix) error {
}
// delSubnetRule deletes the netfilter subnet forwarding rule for
// cidr. Fails if the rule doesn't exist, or if removing the rule
// cidr. Fails if the rule doesn't exist, or if removing the route
// fails.
func (r *linuxRouter) delSubnetRule(cidr netaddr.IPPrefix) error {
if r.netfilterMode == NetfilterOff {
return nil
}
if err := r.ipt4.Delete("filter", "ts-forward", "-i", r.tunname, "-d", normalizeCIDR(cidr), "-j", "MARK", "--set-mark", tailscaleSubnetRouteMark); err != nil {
return fmt.Errorf("deleting subnet mark rule for %q: %v", cidr, err)
}
@ -445,133 +526,39 @@ func (r *linuxRouter) delBypassRule() error {
return cmd("ip", "rule", "del", "priority", "10000")
}
// deleteLegacyNetfilter removes the netfilter rules installed by
// older versions of Tailscale, if they exist.
func (r *linuxRouter) deleteLegacyNetfilter() error {
del := func(table, chain string, args ...string) error {
exists, err := r.ipt4.Exists(table, chain, args...)
if err != nil {
return fmt.Errorf("checking for %v in %s/%s: %v", args, table, chain, err)
}
if exists {
if err := r.ipt4.Delete(table, chain, args...); err != nil {
return fmt.Errorf("deleting %v in %s/%s: %v", args, table, chain, err)
}
}
return nil
}
if err := del("filter", "FORWARD", "-m", "comment", "--comment", "tailscale", "-i", r.tunname, "-j", "ACCEPT"); err != nil {
return err
}
if err := del("nat", "POSTROUTING", "-m", "comment", "--comment", "tailscale", "-o", "eth0", "-j", "MASQUERADE"); err != nil {
return err
}
return nil
}
// deleteNetfilter4 removes custom Tailscale chains and processing
// hooks from netfilter.
func (r *linuxRouter) delNetfilter4() error {
del := func(table, chain string) error {
tsChain := "ts-" + strings.ToLower(chain)
args := []string{"-j", tsChain}
exists, err := r.ipt4.Exists(table, chain, args...)
if err != nil {
return fmt.Errorf("checking for %v in %s/%s: %v", args, table, chain, err)
}
if exists {
if err := r.ipt4.Delete(table, chain, "-j", tsChain); err != nil {
return fmt.Errorf("deleting %v in %s/%s: %v", args, table, chain, err)
}
}
chains, err := r.ipt4.ListChains(table)
if err != nil {
return fmt.Errorf("listing iptables chains: %v", err)
}
for _, chain := range chains {
if chain == tsChain {
if err := r.ipt4.DeleteChain(table, tsChain); err != nil {
return fmt.Errorf("deleting %s/%s: %v", table, tsChain, err)
}
break
}
}
return nil
}
if err := del("filter", "INPUT"); err != nil {
return err
}
if err := del("filter", "FORWARD"); err != nil {
return err
}
if err := del("nat", "POSTROUTING"); err != nil {
return err
}
return nil
}
// chromeOSVMRange is the subset of the CGNAT IPv4 range used by
// ChromeOS to interconnect the host OS to containers and VMs. We
// avoid allocating Tailscale IPs from it, to avoid conflicts.
const chromeOSVMRange = "100.115.92.0/23"
// addBaseNetfilter4 installs the basic IPv4 netfilter framework for
// Tailscale, in preparation for inserting more rules later.
func (r *linuxRouter) addBaseNetfilter4() error {
// Create our own filtering chains, and hook them into the head of
// various main tables. If the hooks already exist, we don't try
// to fight for first place, because other software does the
// same. We're happy with "someplace up before most other stuff".
divert := func(table, chain string) error {
tsChain := "ts-" + strings.ToLower(chain)
// addNetfilterBase adds custom Tailscale chains to netfilter, along
// with some basic processing rules to be supplemented by later calls
// to other helpers.
func (r *linuxRouter) addNetfilterBase() error {
create := func(table, chain string) error {
chains, err := r.ipt4.ListChains(table)
if err != nil {
return fmt.Errorf("listing iptables chains: %v", err)
}
found := false
for _, chain := range chains {
if chain == tsChain {
for _, ch := range chains {
if ch == chain {
found = true
break
}
}
if found {
err = r.ipt4.ClearChain(table, tsChain)
err = r.ipt4.ClearChain(table, chain)
} else {
err = r.ipt4.NewChain(table, tsChain)
err = r.ipt4.NewChain(table, chain)
}
if err != nil {
return fmt.Errorf("setting up %s/%s: %v", table, tsChain, err)
}
args := []string{"-j", tsChain}
exists, err := r.ipt4.Exists(table, chain, args...)
if err != nil {
return fmt.Errorf("checking for %v in %s/%s: %v", args, table, chain, err)
}
if exists {
return nil
}
if err := r.ipt4.Insert(table, chain, 1, args...); err != nil {
return fmt.Errorf("adding %v in %s/%s: %v", args, table, chain, err)
return fmt.Errorf("setting up %s/%s: %v", table, chain, err)
}
return nil
}
if err := divert("filter", "INPUT"); err != nil {
if err := create("filter", "ts-input"); err != nil {
return err
}
if err := divert("filter", "FORWARD"); err != nil {
if err := create("filter", "ts-forward"); err != nil {
return err
}
if err := divert("nat", "POSTROUTING"); err != nil {
if err := create("nat", "ts-postrouting"); err != nil {
return err
}
@ -614,9 +601,127 @@ func (r *linuxRouter) addBaseNetfilter4() error {
return nil
}
// delNetfilterBase removes custom Tailscale chains from netfilter.
func (r *linuxRouter) delNetfilterBase() error {
del := func(table, chain string) error {
chains, err := r.ipt4.ListChains(table)
if err != nil {
return fmt.Errorf("listing iptables chains: %v", err)
}
for _, ch := range chains {
if ch == chain {
if err := r.ipt4.ClearChain(table, chain); err != nil {
return fmt.Errorf("flushing %s/%s: %v", table, chain, err)
}
if err := r.ipt4.DeleteChain(table, chain); err != nil {
return fmt.Errorf("deleting %s/%s: %v", table, chain, err)
}
return nil
}
}
return nil
}
if err := del("filter", "ts-input"); err != nil {
return err
}
if err := del("filter", "ts-forward"); err != nil {
return err
}
if err := del("nat", "ts-postrouting"); err != nil {
return err
}
return nil
}
// addNetfilterHooks inserts calls to tailscale's netfilter chains in
// the relevant main netfilter chains. The tailscale chains must
// already exist.
func (r *linuxRouter) addNetfilterHooks() error {
divert := func(table, chain string) error {
tsChain := tsChain(chain)
chains, err := r.ipt4.ListChains(table)
if err != nil {
return fmt.Errorf("listing iptables chains: %v", err)
}
found := false
for _, chain := range chains {
if chain == tsChain {
found = true
break
}
}
if !found {
return fmt.Errorf("chain %q does not exist, cannot divert to it", tsChain)
}
args := []string{"-j", tsChain}
exists, err := r.ipt4.Exists(table, chain, args...)
if err != nil {
return fmt.Errorf("checking for %v in %s/%s: %v", args, table, chain, err)
}
if exists {
return nil
}
if err := r.ipt4.Insert(table, chain, 1, args...); err != nil {
return fmt.Errorf("adding %v in %s/%s: %v", args, table, chain, err)
}
return nil
}
if err := divert("filter", "INPUT"); err != nil {
return err
}
if err := divert("filter", "FORWARD"); err != nil {
return err
}
if err := divert("nat", "POSTROUTING"); err != nil {
return err
}
return nil
}
// delNetfilterHooks deletes the calls to tailscale's netfilter chains
// in the relevant main netfilter chains.
func (r *linuxRouter) delNetfilterHooks() error {
del := func(table, chain string) error {
tsChain := tsChain(chain)
args := []string{"-j", tsChain}
exists, err := r.ipt4.Exists(table, chain, args...)
if err != nil {
return fmt.Errorf("checking for %v in %s/%s: %v", args, table, chain, err)
}
if !exists {
return nil
}
if err := r.ipt4.Delete(table, chain, args...); err != nil {
return fmt.Errorf("deleting %v in %s/%s: %v", args, table, chain, err)
}
return nil
}
if err := del("filter", "INPUT"); err != nil {
return err
}
if err := del("filter", "FORWARD"); err != nil {
return err
}
if err := del("nat", "POSTROUTING"); err != nil {
return err
}
return nil
}
// addSNATRule adds a netfilter rule to SNAT traffic destined for
// local subnets.
func (r *linuxRouter) addSNATRule() error {
if r.netfilterMode == NetfilterOff {
return nil
}
args := []string{"-m", "mark", "--mark", tailscaleSubnetRouteMark, "-j", "MASQUERADE"}
if err := r.ipt4.Append("nat", "ts-postrouting", args...); err != nil {
return fmt.Errorf("adding %v in nat/ts-postrouting: %v", args, err)
@ -627,9 +732,93 @@ func (r *linuxRouter) addSNATRule() error {
// delSNATRule removes the netfilter rule to SNAT traffic destined for
// local subnets. Fails if the rule does not exist.
func (r *linuxRouter) delSNATRule() error {
if r.netfilterMode == NetfilterOff {
return nil
}
args := []string{"-m", "mark", "--mark", tailscaleSubnetRouteMark, "-j", "MASQUERADE"}
if err := r.ipt4.Delete("nat", "ts-postrouting", args...); err != nil {
return fmt.Errorf("deleting %v in nat/ts-postrouting: %v", args, err)
}
return nil
}
func (r *linuxRouter) delLegacyNetfilter() error {
del := func(table, chain string, args ...string) error {
exists, err := r.ipt4.Exists(table, chain, args...)
if err != nil {
return fmt.Errorf("checking for %v in %s/%s: %v", args, table, chain, err)
}
if exists {
if err := r.ipt4.Delete(table, chain, args...); err != nil {
return fmt.Errorf("deleting %v in %s/%s: %v", args, table, chain, err)
}
}
return nil
}
if err := del("filter", "FORWARD", "-m", "comment", "--comment", "tailscale", "-i", r.tunname, "-j", "ACCEPT"); err != nil {
return err
}
if err := del("nat", "POSTROUTING", "-m", "comment", "--comment", "tailscale", "-o", "eth0", "-j", "MASQUERADE"); err != nil {
return err
}
return nil
}
// cidrDiff calls add and del as needed to make the set of prefixes in
// old and new match. Returns a map reflecting the actual new state
// (which may be somewhere in between old and new if some commands
// failed), and any error encountered while reconfiguring.
func cidrDiff(kind string, old map[netaddr.IPPrefix]bool, new []netaddr.IPPrefix, add, del func(netaddr.IPPrefix) error, logf logger.Logf) (map[netaddr.IPPrefix]bool, error) {
newMap := make(map[netaddr.IPPrefix]bool, len(new))
for _, cidr := range new {
newMap[cidr] = true
}
// ret starts out as a copy of old, and updates as we
// add/delete. That way we can always return it and have it be the
// true state of what we've done so far.
ret := make(map[netaddr.IPPrefix]bool, len(old))
for cidr := range old {
ret[cidr] = true
}
for cidr := range old {
if newMap[cidr] {
continue
}
if err := del(cidr); err != nil {
logf("%s del failed: %v", kind, err)
return ret, err
}
delete(ret, cidr)
}
for cidr := range newMap {
if old[cidr] {
continue
}
if err := add(cidr); err != nil {
logf("%s add failed: %v", kind, err)
return ret, err
}
ret[cidr] = true
}
return ret, nil
}
// tsChain returns the name of the tailscale sub-chain corresponding
// to the given "parent" chain (e.g. INPUT, FORWARD, ...).
func tsChain(chain string) string {
return "ts-" + strings.ToLower(chain)
}
// normalizeCIDR returns cidr as an ip/mask string, with the host bits
// of the IP address zeroed out.
func normalizeCIDR(cidr netaddr.IPPrefix) string {
ncidr := cidr.IPNet()
nip := ncidr.IP.Mask(ncidr.Mask)
return fmt.Sprintf("%s/%d", nip, cidr.Bits)
}