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https://github.com/tailscale/tailscale.git
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util/linuxfw: decoupling IPTables logic from linux router
This change is introducing new netfilterRunner interface and moving iptables manipulation to a lower leveled iptables runner. For #391 Signed-off-by: KevinLiang10 <kevinliang@tailscale.com>
This commit is contained in:
KevinLiang10
committed by
KevinLiang10
KevinLiang10
parent
9c64e015e5
commit
243ce6ccc1
475
util/linuxfw/iptables_runner.go
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475
util/linuxfw/iptables_runner.go
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@@ -0,0 +1,475 @@
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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//go:build linux
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package linuxfw
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import (
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"fmt"
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"net/netip"
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"strings"
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"github.com/coreos/go-iptables/iptables"
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"tailscale.com/net/tsaddr"
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"tailscale.com/types/logger"
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"tailscale.com/util/multierr"
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)
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type iptablesInterface interface {
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// Adding this interface for testing purposes so we can mock out
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// the iptables library, in reality this is a wrapper to *iptables.IPTables.
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Insert(table, chain string, pos int, args ...string) error
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Append(table, chain string, args ...string) error
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Exists(table, chain string, args ...string) (bool, error)
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Delete(table, chain string, args ...string) error
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ClearChain(table, chain string) error
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NewChain(table, chain string) error
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DeleteChain(table, chain string) error
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}
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type iptablesRunner struct {
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ipt4 iptablesInterface
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ipt6 iptablesInterface
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v6Available bool
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v6NATAvailable bool
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}
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// NewIPTablesRunner constructs a NetfilterRunner that programs iptables rules.
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// If the underlying iptables library fails to initialize, that error is
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// returned. The runner probes for IPv6 support once at initialization time and
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// if not found, no IPv6 rules will be modified for the lifetime of the runner.
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func NewIPTablesRunner(logf logger.Logf) (*iptablesRunner, error) {
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ipt4, err := iptables.NewWithProtocol(iptables.ProtocolIPv4)
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if err != nil {
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return nil, err
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}
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supportsV6, supportsV6NAT := false, false
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v6err := checkIPv6(logf)
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if v6err != nil {
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logf("disabling tunneled IPv6 due to system IPv6 config: %v", v6err)
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} else {
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supportsV6 = true
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supportsV6NAT = supportsV6 && checkSupportsV6NAT()
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logf("v6nat = %v", supportsV6NAT)
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}
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var ipt6 *iptables.IPTables
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if supportsV6 {
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ipt6, err = iptables.NewWithProtocol(iptables.ProtocolIPv6)
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if err != nil {
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return nil, err
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}
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}
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return &iptablesRunner{ipt4, ipt6, supportsV6, supportsV6NAT}, nil
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}
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// HasIPV6 returns true if the system supports IPv6.
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func (i *iptablesRunner) HasIPV6() bool {
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return i.v6Available
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}
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// HasIPV6NAT returns true if the system supports IPv6 NAT.
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func (i *iptablesRunner) HasIPV6NAT() bool {
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return i.v6NATAvailable
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}
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func isErrChainNotExist(err error) bool {
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return errCode(err) == 1
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}
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// getIPTByAddr returns the iptablesInterface with correct IP family
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// that we will be using for the given address.
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func (i *iptablesRunner) getIPTByAddr(addr netip.Addr) iptablesInterface {
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nf := i.ipt4
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if addr.Is6() {
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nf = i.ipt6
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}
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return nf
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}
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// AddLoopbackRule adds an iptables rule to permit loopback traffic to
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// a local Tailscale IP.
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func (i *iptablesRunner) AddLoopbackRule(addr netip.Addr) error {
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if err := i.getIPTByAddr(addr).Insert("filter", "ts-input", 1, "-i", "lo", "-s", addr.String(), "-j", "ACCEPT"); err != nil {
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return fmt.Errorf("adding loopback allow rule for %q: %w", addr, err)
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}
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return nil
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}
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// tsChain returns the name of the tailscale sub-chain corresponding
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// to the given "parent" chain (e.g. INPUT, FORWARD, ...).
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func tsChain(chain string) string {
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return "ts-" + strings.ToLower(chain)
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}
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// DelLoopbackRule removes the iptables rule permitting loopback
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// traffic to a Tailscale IP.
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func (i *iptablesRunner) DelLoopbackRule(addr netip.Addr) error {
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if err := i.getIPTByAddr(addr).Delete("filter", "ts-input", "-i", "lo", "-s", addr.String(), "-j", "ACCEPT"); err != nil {
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return fmt.Errorf("deleting loopback allow rule for %q: %w", addr, err)
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}
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return nil
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}
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// getTables gets the available iptablesInterface in iptables runner.
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func (i *iptablesRunner) getTables() []iptablesInterface {
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if i.HasIPV6() {
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return []iptablesInterface{i.ipt4, i.ipt6}
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}
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return []iptablesInterface{i.ipt4}
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}
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// getNATTables gets the available iptablesInterface in iptables runner.
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// If the system does not support IPv6 NAT, only the IPv4 iptablesInterface
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// is returned.
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func (i *iptablesRunner) getNATTables() []iptablesInterface {
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if i.HasIPV6NAT() {
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return i.getTables()
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}
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return []iptablesInterface{i.ipt4}
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}
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// AddHooks inserts calls to tailscale's netfilter chains in
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// the relevant main netfilter chains. The tailscale chains must
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// already exist. If they do not, an error is returned.
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func (i *iptablesRunner) AddHooks() error {
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// divert inserts a jump to the tailscale chain in the given table/chain.
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// If the jump already exists, it is a no-op.
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divert := func(ipt iptablesInterface, table, chain string) error {
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tsChain := tsChain(chain)
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args := []string{"-j", tsChain}
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exists, err := ipt.Exists(table, chain, args...)
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if err != nil {
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return fmt.Errorf("checking for %v in %s/%s: %w", args, table, chain, err)
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}
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if exists {
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return nil
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}
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if err := ipt.Insert(table, chain, 1, args...); err != nil {
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return fmt.Errorf("adding %v in %s/%s: %w", args, table, chain, err)
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}
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return nil
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}
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for _, ipt := range i.getTables() {
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if err := divert(ipt, "filter", "INPUT"); err != nil {
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return err
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}
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if err := divert(ipt, "filter", "FORWARD"); err != nil {
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return err
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}
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}
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for _, ipt := range i.getNATTables() {
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if err := divert(ipt, "nat", "POSTROUTING"); err != nil {
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return err
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}
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}
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return nil
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}
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// AddChains creates custom Tailscale chains in netfilter via iptables
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// if the ts-chain doesn't already exist.
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func (i *iptablesRunner) AddChains() error {
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// create creates a chain in the given table if it doesn't already exist.
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// If the chain already exists, it is a no-op.
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create := func(ipt iptablesInterface, table, chain string) error {
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err := ipt.ClearChain(table, chain)
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if isErrChainNotExist(err) {
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// nonexistent chain. let's create it!
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return ipt.NewChain(table, chain)
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}
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if err != nil {
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return fmt.Errorf("setting up %s/%s: %w", table, chain, err)
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}
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return nil
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}
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for _, ipt := range i.getTables() {
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if err := create(ipt, "filter", "ts-input"); err != nil {
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return err
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}
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if err := create(ipt, "filter", "ts-forward"); err != nil {
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return err
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}
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}
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for _, ipt := range i.getNATTables() {
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if err := create(ipt, "nat", "ts-postrouting"); err != nil {
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return err
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}
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}
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return nil
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}
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// AddBase adds some basic processing rules to be supplemented by
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// later calls to other helpers.
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func (i *iptablesRunner) AddBase(tunname string) error {
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if err := i.addBase4(tunname); err != nil {
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return err
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}
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if i.HasIPV6() {
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if err := i.addBase6(tunname); err != nil {
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return err
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}
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}
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return nil
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}
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// addBase4 adds some basic IPv6 processing rules to be
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// supplemented by later calls to other helpers.
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func (i *iptablesRunner) addBase4(tunname string) error {
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// Only allow CGNAT range traffic to come from tailscale0. There
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// is an exception carved out for ranges used by ChromeOS, for
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// which we fall out of the Tailscale chain.
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//
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// Note, this will definitely break nodes that end up using the
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// CGNAT range for other purposes :(.
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args := []string{"!", "-i", tunname, "-s", tsaddr.ChromeOSVMRange().String(), "-j", "RETURN"}
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if err := i.ipt4.Append("filter", "ts-input", args...); err != nil {
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return fmt.Errorf("adding %v in v4/filter/ts-input: %w", args, err)
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}
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args = []string{"!", "-i", tunname, "-s", tsaddr.CGNATRange().String(), "-j", "DROP"}
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if err := i.ipt4.Append("filter", "ts-input", args...); err != nil {
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return fmt.Errorf("adding %v in v4/filter/ts-input: %w", args, err)
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}
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// Forward all traffic from the Tailscale interface, and drop
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// traffic to the tailscale interface by default. We use packet
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// marks here so both filter/FORWARD and nat/POSTROUTING can match
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// on these packets of interest.
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//
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// In particular, we only want to apply SNAT rules in
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// nat/POSTROUTING to packets that originated from the Tailscale
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// interface, but we can't match on the inbound interface in
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// POSTROUTING. So instead, we match on the inbound interface in
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// filter/FORWARD, and set a packet mark that nat/POSTROUTING can
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// use to effectively run that same test again.
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args = []string{"-i", tunname, "-j", "MARK", "--set-mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask}
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if err := i.ipt4.Append("filter", "ts-forward", args...); err != nil {
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return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
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}
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args = []string{"-m", "mark", "--mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask, "-j", "ACCEPT"}
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if err := i.ipt4.Append("filter", "ts-forward", args...); err != nil {
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return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
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}
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args = []string{"-o", tunname, "-s", tsaddr.CGNATRange().String(), "-j", "DROP"}
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if err := i.ipt4.Append("filter", "ts-forward", args...); err != nil {
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return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
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}
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args = []string{"-o", tunname, "-j", "ACCEPT"}
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if err := i.ipt4.Append("filter", "ts-forward", args...); err != nil {
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return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
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}
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return nil
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}
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// addBase6 adds some basic IPv4 processing rules to be
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// supplemented by later calls to other helpers.
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func (i *iptablesRunner) addBase6(tunname string) error {
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// TODO: only allow traffic from Tailscale's ULA range to come
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// from tailscale0.
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args := []string{"-i", tunname, "-j", "MARK", "--set-mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask}
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if err := i.ipt6.Append("filter", "ts-forward", args...); err != nil {
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return fmt.Errorf("adding %v in v6/filter/ts-forward: %w", args, err)
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}
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args = []string{"-m", "mark", "--mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask, "-j", "ACCEPT"}
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if err := i.ipt6.Append("filter", "ts-forward", args...); err != nil {
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return fmt.Errorf("adding %v in v6/filter/ts-forward: %w", args, err)
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}
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// TODO: drop forwarded traffic to tailscale0 from tailscale's ULA
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// (see corresponding IPv4 CGNAT rule).
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args = []string{"-o", tunname, "-j", "ACCEPT"}
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if err := i.ipt6.Append("filter", "ts-forward", args...); err != nil {
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return fmt.Errorf("adding %v in v6/filter/ts-forward: %w", args, err)
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}
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return nil
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}
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// DelChains removes the custom Tailscale chains from netfilter via iptables.
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func (i *iptablesRunner) DelChains() error {
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for _, ipt := range i.getTables() {
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if err := delChain(ipt, "filter", "ts-input"); err != nil {
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return err
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}
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if err := delChain(ipt, "filter", "ts-forward"); err != nil {
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return err
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}
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}
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for _, ipt := range i.getNATTables() {
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if err := delChain(ipt, "nat", "ts-postrouting"); err != nil {
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return err
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}
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}
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return nil
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}
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// DelBase empties but does not remove custom Tailscale chains from
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// netfilter via iptables.
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func (i *iptablesRunner) DelBase() error {
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del := func(ipt iptablesInterface, table, chain string) error {
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if err := ipt.ClearChain(table, chain); err != nil {
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if isErrChainNotExist(err) {
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// nonexistent chain. That's fine, since it's
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// the desired state anyway.
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return nil
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}
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return fmt.Errorf("flushing %s/%s: %w", table, chain, err)
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}
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return nil
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}
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for _, ipt := range i.getTables() {
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if err := del(ipt, "filter", "ts-input"); err != nil {
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return err
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}
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if err := del(ipt, "filter", "ts-forward"); err != nil {
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return err
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}
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}
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for _, ipt := range i.getNATTables() {
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if err := del(ipt, "nat", "ts-postrouting"); err != nil {
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return err
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}
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}
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return nil
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}
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// DelHooks deletes the calls to tailscale's netfilter chains
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// in the relevant main netfilter chains.
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func (i *iptablesRunner) DelHooks(logf logger.Logf) error {
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for _, ipt := range i.getTables() {
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if err := delTSHook(ipt, "filter", "INPUT", logf); err != nil {
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return err
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}
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if err := delTSHook(ipt, "filter", "FORWARD", logf); err != nil {
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return err
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}
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}
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for _, ipt := range i.getNATTables() {
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if err := delTSHook(ipt, "nat", "POSTROUTING", logf); err != nil {
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return err
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}
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}
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return nil
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}
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// AddSNATRule adds a netfilter rule to SNAT traffic destined for
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// local subnets.
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func (i *iptablesRunner) AddSNATRule() error {
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args := []string{"-m", "mark", "--mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask, "-j", "MASQUERADE"}
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for _, ipt := range i.getNATTables() {
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if err := ipt.Append("nat", "ts-postrouting", args...); err != nil {
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return fmt.Errorf("adding %v in nat/ts-postrouting: %w", args, err)
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}
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}
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return nil
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}
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// DelSNATRule removes the netfilter rule to SNAT traffic destined for
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// local subnets. An error is returned if the rule does not exist.
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func (i *iptablesRunner) DelSNATRule() error {
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args := []string{"-m", "mark", "--mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask, "-j", "MASQUERADE"}
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for _, ipt := range i.getNATTables() {
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if err := ipt.Delete("nat", "ts-postrouting", args...); err != nil {
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return fmt.Errorf("deleting %v in nat/ts-postrouting: %w", args, err)
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}
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}
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return nil
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}
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// IPTablesCleanup removes all Tailscale added iptables rules.
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// Any errors that occur are logged to the provided logf.
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func IPTablesCleanup(logf logger.Logf) {
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err := clearRules(iptables.ProtocolIPv4, logf)
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if err != nil {
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logf("linuxfw: clear iptables: %v", err)
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}
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err = clearRules(iptables.ProtocolIPv6, logf)
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if err != nil {
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logf("linuxfw: clear ip6tables: %v", err)
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}
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}
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// delTSHook deletes hook in a chain that jumps to a ts-chain. If the hook does not
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// exist, it's a no-op since the desired state is already achieved but we log the
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// error because error code from the iptables module resists unwrapping.
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func delTSHook(ipt iptablesInterface, table, chain string, logf logger.Logf) error {
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tsChain := tsChain(chain)
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args := []string{"-j", tsChain}
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if err := ipt.Delete(table, chain, args...); err != nil {
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// TODO(apenwarr): check for errCode(1) here.
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// Unfortunately the error code from the iptables
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// module resists unwrapping, unlike with other
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// calls. So we have to assume if Delete fails,
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// it's because there is no such rule.
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logf("deleting %v in %s/%s: %v", args, table, chain, err)
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return nil
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}
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return nil
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}
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// delChain flushs and deletes a chain. If the chain does not exist, it's a no-op
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// since the desired state is already achieved. otherwise, it returns an error.
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func delChain(ipt iptablesInterface, table, chain string) error {
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if err := ipt.ClearChain(table, chain); err != nil {
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if isErrChainNotExist(err) {
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// nonexistent chain. nothing to do.
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return nil
|
||||
}
|
||||
return fmt.Errorf("flushing %s/%s: %w", table, chain, err)
|
||||
}
|
||||
if err := ipt.DeleteChain(table, chain); err != nil {
|
||||
return fmt.Errorf("deleting %s/%s: %w", table, chain, err)
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
// clearRules clears all the iptables rules created by Tailscale
|
||||
// for the given protocol. If error occurs, it's logged but not returned.
|
||||
func clearRules(proto iptables.Protocol, logf logger.Logf) error {
|
||||
ipt, err := iptables.NewWithProtocol(proto)
|
||||
if err != nil {
|
||||
return err
|
||||
}
|
||||
|
||||
var errs []error
|
||||
|
||||
if err := delTSHook(ipt, "filter", "INPUT", logf); err != nil {
|
||||
errs = append(errs, err)
|
||||
}
|
||||
if err := delTSHook(ipt, "filter", "FORWARD", logf); err != nil {
|
||||
errs = append(errs, err)
|
||||
}
|
||||
if err := delTSHook(ipt, "nat", "POSTROUTING", logf); err != nil {
|
||||
errs = append(errs, err)
|
||||
}
|
||||
|
||||
if err := delChain(ipt, "filter", "ts-input"); err != nil {
|
||||
errs = append(errs, err)
|
||||
}
|
||||
if err := delChain(ipt, "filter", "ts-forward"); err != nil {
|
||||
errs = append(errs, err)
|
||||
}
|
||||
|
||||
if err := delChain(ipt, "nat", "ts-postrouting"); err != nil {
|
||||
errs = append(errs, err)
|
||||
}
|
||||
|
||||
return multierr.New(errs...)
|
||||
}
|
||||
Reference in New Issue
Block a user