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tailscale/util/linuxfw/iptables_runner.go

728 lines
25 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
//go:build linux
package linuxfw
import (
"bytes"
"errors"
"fmt"
"net/netip"
"os"
"os/exec"
"slices"
"strconv"
"strings"
"github.com/coreos/go-iptables/iptables"
"tailscale.com/net/tsaddr"
"tailscale.com/types/logger"
"tailscale.com/util/multierr"
)
// isNotExistError needs to be overridden in tests that rely on distinguishing
// this error, because we don't have a good way how to create a new
// iptables.Error of that type.
var isNotExistError = func(err error) bool {
var e *iptables.Error
return errors.As(err, &e) && e.IsNotExist()
}
type iptablesInterface interface {
// Adding this interface for testing purposes so we can mock out
// the iptables library, in reality this is a wrapper to *iptables.IPTables.
Insert(table, chain string, pos int, args ...string) error
Append(table, chain string, args ...string) error
Exists(table, chain string, args ...string) (bool, error)
Delete(table, chain string, args ...string) error
List(table, chain string) ([]string, error)
ClearChain(table, chain string) error
NewChain(table, chain string) error
DeleteChain(table, chain string) error
}
type iptablesRunner struct {
ipt4 iptablesInterface
ipt6 iptablesInterface
v6Available bool
v6NATAvailable bool
v6FilterAvailable bool
}
func checkIP6TablesExists() error {
// Some distros ship ip6tables separately from iptables.
if _, err := exec.LookPath("ip6tables"); err != nil {
return fmt.Errorf("path not found: %w", err)
}
return nil
}
// newIPTablesRunner constructs a NetfilterRunner that programs iptables rules.
// If the underlying iptables library fails to initialize, that error is
// returned. The runner probes for IPv6 support once at initialization time and
// if not found, no IPv6 rules will be modified for the lifetime of the runner.
func newIPTablesRunner(logf logger.Logf) (*iptablesRunner, error) {
ipt4, err := iptables.NewWithProtocol(iptables.ProtocolIPv4)
if err != nil {
return nil, err
}
supportsV6, supportsV6NAT, supportsV6Filter := false, false, false
v6err := CheckIPv6(logf)
ip6terr := checkIP6TablesExists()
var ipt6 *iptables.IPTables
switch {
case v6err != nil:
logf("disabling tunneled IPv6 due to system IPv6 config: %v", v6err)
case ip6terr != nil:
logf("disabling tunneled IPv6 due to missing ip6tables: %v", ip6terr)
default:
supportsV6 = true
ipt6, err = iptables.NewWithProtocol(iptables.ProtocolIPv6)
if err != nil {
return nil, err
}
supportsV6Filter = checkSupportsV6Filter(ipt6, logf)
supportsV6NAT = checkSupportsV6NAT(ipt6, logf)
logf("netfilter running in iptables mode v6 = %v, v6filter = %v, v6nat = %v", supportsV6, supportsV6Filter, supportsV6NAT)
}
return &iptablesRunner{
ipt4: ipt4,
ipt6: ipt6,
v6Available: supportsV6,
v6NATAvailable: supportsV6NAT,
v6FilterAvailable: supportsV6Filter}, nil
}
// checkSupportsV6Filter returns whether the system has a "filter" table in the
// IPv6 tables. Some container environments such as GitHub codespaces have
// limited local IPv6 support, and containers containing ip6tables, but do not
// have kernel support for IPv6 filtering.
// We will not set ip6tables rules in these instances.
func checkSupportsV6Filter(ipt *iptables.IPTables, logf logger.Logf) bool {
if ipt == nil {
return false
}
_, filterListErr := ipt.ListChains("filter")
if filterListErr == nil {
return true
}
logf("ip6tables filtering is not supported on this host: %v", filterListErr)
return false
}
// checkSupportsV6NAT returns whether the system has a "nat" table in the
// IPv6 netfilter stack.
//
// The nat table was added after the initial release of ipv6
// netfilter, so some older distros ship a kernel that can't NAT IPv6
// traffic.
// ipt must be initialized for IPv6.
func checkSupportsV6NAT(ipt *iptables.IPTables, logf logger.Logf) bool {
if ipt == nil || ipt.Proto() != iptables.ProtocolIPv6 {
return false
}
_, natListErr := ipt.ListChains("nat")
if natListErr == nil {
return true
}
// TODO (irbekrm): the following two checks were added before the check
// above that verifies that nat chains can be listed. It is a
// container-friendly check (see
// https://github.com/tailscale/tailscale/issues/11344), but also should
// be good enough on its own in other environments. If we never observe
// it falsely succeed, let's remove the other two checks.
bs, err := os.ReadFile("/proc/net/ip6_tables_names")
if err != nil {
return false
}
if bytes.Contains(bs, []byte("nat\n")) {
logf("[unexpected] listing nat chains failed, but /proc/net/ip6_tables_name reports a nat table existing")
return true
}
if exec.Command("modprobe", "ip6table_nat").Run() == nil {
logf("[unexpected] listing nat chains failed, but modprobe ip6table_nat succeeded")
return true
}
return false
}
// HasIPV6 reports true if the system supports IPv6.
func (i *iptablesRunner) HasIPV6() bool {
return i.v6Available
}
// HasIPV6Filter reports true if the system supports ip6tables filter table.
func (i *iptablesRunner) HasIPV6Filter() bool {
return i.v6FilterAvailable
}
// HasIPV6NAT reports true if the system supports IPv6 NAT.
func (i *iptablesRunner) HasIPV6NAT() bool {
return i.v6NATAvailable
}
// getIPTByAddr returns the iptablesInterface with correct IP family
// that we will be using for the given address.
func (i *iptablesRunner) getIPTByAddr(addr netip.Addr) iptablesInterface {
nf := i.ipt4
if addr.Is6() {
nf = i.ipt6
}
return nf
}
// AddLoopbackRule adds an iptables rule to permit loopback traffic to
// a local Tailscale IP.
func (i *iptablesRunner) AddLoopbackRule(addr netip.Addr) error {
if err := i.getIPTByAddr(addr).Insert("filter", "ts-input", 1, "-i", "lo", "-s", addr.String(), "-j", "ACCEPT"); err != nil {
return fmt.Errorf("adding loopback allow rule for %q: %w", addr, err)
}
return 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)
}
// DelLoopbackRule removes the iptables rule permitting loopback
// traffic to a Tailscale IP.
func (i *iptablesRunner) DelLoopbackRule(addr netip.Addr) error {
if err := i.getIPTByAddr(addr).Delete("filter", "ts-input", "-i", "lo", "-s", addr.String(), "-j", "ACCEPT"); err != nil {
return fmt.Errorf("deleting loopback allow rule for %q: %w", addr, err)
}
return nil
}
// getTables gets the available iptablesInterface in iptables runner.
func (i *iptablesRunner) getTables() []iptablesInterface {
if i.HasIPV6Filter() {
return []iptablesInterface{i.ipt4, i.ipt6}
}
return []iptablesInterface{i.ipt4}
}
// getNATTables gets the available iptablesInterface in iptables runner.
// If the system does not support IPv6 NAT, only the IPv4 iptablesInterface
// is returned.
func (i *iptablesRunner) getNATTables() []iptablesInterface {
if i.HasIPV6NAT() {
return i.getTables()
}
return []iptablesInterface{i.ipt4}
}
// AddHooks inserts calls to tailscale's netfilter chains in
// the relevant main netfilter chains. The tailscale chains must
// already exist. If they do not, an error is returned.
func (i *iptablesRunner) AddHooks() error {
// divert inserts a jump to the tailscale chain in the given table/chain.
// If the jump already exists, it is a no-op.
divert := func(ipt iptablesInterface, table, chain string) error {
tsChain := tsChain(chain)
args := []string{"-j", tsChain}
exists, err := ipt.Exists(table, chain, args...)
if err != nil {
return fmt.Errorf("checking for %v in %s/%s: %w", args, table, chain, err)
}
if exists {
return nil
}
if err := ipt.Insert(table, chain, 1, args...); err != nil {
return fmt.Errorf("adding %v in %s/%s: %w", args, table, chain, err)
}
return nil
}
for _, ipt := range i.getTables() {
if err := divert(ipt, "filter", "INPUT"); err != nil {
return err
}
if err := divert(ipt, "filter", "FORWARD"); err != nil {
return err
}
}
for _, ipt := range i.getNATTables() {
if err := divert(ipt, "nat", "POSTROUTING"); err != nil {
return err
}
}
return nil
}
// AddChains creates custom Tailscale chains in netfilter via iptables
// if the ts-chain doesn't already exist.
func (i *iptablesRunner) AddChains() error {
// create creates a chain in the given table if it doesn't already exist.
// If the chain already exists, it is a no-op.
create := func(ipt iptablesInterface, table, chain string) error {
err := ipt.ClearChain(table, chain)
if isNotExistError(err) {
// nonexistent chain. let's create it!
return ipt.NewChain(table, chain)
}
if err != nil {
return fmt.Errorf("setting up %s/%s: %w", table, chain, err)
}
return nil
}
for _, ipt := range i.getTables() {
if err := create(ipt, "filter", "ts-input"); err != nil {
return err
}
if err := create(ipt, "filter", "ts-forward"); err != nil {
return err
}
}
for _, ipt := range i.getNATTables() {
if err := create(ipt, "nat", "ts-postrouting"); err != nil {
return err
}
}
return nil
}
// AddBase adds some basic processing rules to be supplemented by
// later calls to other helpers.
func (i *iptablesRunner) AddBase(tunname string) error {
if err := i.addBase4(tunname); err != nil {
return err
}
if i.HasIPV6Filter() {
if err := i.addBase6(tunname); err != nil {
return err
}
}
return nil
}
// addBase4 adds some basic IPv4 processing rules to be
// supplemented by later calls to other helpers.
func (i *iptablesRunner) addBase4(tunname string) error {
// Only allow CGNAT range traffic to come from tailscale0. There
// is an exception carved out for ranges used by ChromeOS, for
// which we fall out of the Tailscale chain.
//
// Note, this will definitely break nodes that end up using the
// CGNAT range for other purposes :(.
args := []string{"!", "-i", tunname, "-s", tsaddr.ChromeOSVMRange().String(), "-j", "RETURN"}
if err := i.ipt4.Append("filter", "ts-input", args...); err != nil {
return fmt.Errorf("adding %v in v4/filter/ts-input: %w", args, err)
}
args = []string{"!", "-i", tunname, "-s", tsaddr.CGNATRange().String(), "-j", "DROP"}
if err := i.ipt4.Append("filter", "ts-input", args...); err != nil {
return fmt.Errorf("adding %v in v4/filter/ts-input: %w", args, err)
}
// Explicitly allow all other inbound traffic to the tun interface
args = []string{"-i", tunname, "-j", "ACCEPT"}
if err := i.ipt4.Append("filter", "ts-input", args...); err != nil {
return fmt.Errorf("adding %v in v4/filter/ts-input: %w", args, err)
}
// Forward all traffic from the Tailscale interface, and drop
// traffic to the tailscale interface by default. We use packet
// marks here so both filter/FORWARD and nat/POSTROUTING can match
// on these packets of interest.
//
// In particular, we only want to apply SNAT rules in
// nat/POSTROUTING to packets that originated from the Tailscale
// interface, but we can't match on the inbound interface in
// POSTROUTING. So instead, we match on the inbound interface in
// filter/FORWARD, and set a packet mark that nat/POSTROUTING can
// use to effectively run that same test again.
args = []string{"-i", tunname, "-j", "MARK", "--set-mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask}
if err := i.ipt4.Append("filter", "ts-forward", args...); err != nil {
return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
}
args = []string{"-m", "mark", "--mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask, "-j", "ACCEPT"}
if err := i.ipt4.Append("filter", "ts-forward", args...); err != nil {
return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
}
args = []string{"-o", tunname, "-s", tsaddr.CGNATRange().String(), "-j", "DROP"}
if err := i.ipt4.Append("filter", "ts-forward", args...); err != nil {
return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
}
args = []string{"-o", tunname, "-j", "ACCEPT"}
if err := i.ipt4.Append("filter", "ts-forward", args...); err != nil {
return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
}
return nil
}
func (i *iptablesRunner) AddDNATRule(origDst, dst netip.Addr) error {
table := i.getIPTByAddr(dst)
return table.Insert("nat", "PREROUTING", 1, "--destination", origDst.String(), "-j", "DNAT", "--to-destination", dst.String())
}
func (i *iptablesRunner) AddSNATRuleForDst(src, dst netip.Addr) error {
table := i.getIPTByAddr(dst)
return table.Insert("nat", "POSTROUTING", 1, "--destination", dst.String(), "-j", "SNAT", "--to-source", src.String())
}
func (i *iptablesRunner) DNATNonTailscaleTraffic(tun string, dst netip.Addr) error {
table := i.getIPTByAddr(dst)
return table.Insert("nat", "PREROUTING", 1, "!", "-i", tun, "-j", "DNAT", "--to-destination", dst.String())
}
// DNATWithLoadBalancer adds iptables rules to forward all traffic received for
// originDst to the backend dsts. Traffic will be load balanced using round robin.
func (i *iptablesRunner) DNATWithLoadBalancer(origDst netip.Addr, dsts []netip.Addr) error {
table := i.getIPTByAddr(dsts[0])
if err := table.ClearChain("nat", "PREROUTING"); err != nil && !isNotExistError(err) {
// If clearing the PREROUTING chain fails, fail the whole operation. This
// rule is currently only used in Kubernetes containers where a
// failed container gets restarted which should hopefully fix things.
return fmt.Errorf("error clearing nat PREROUTING chain: %w", err)
}
// If dsts contain more than one address, for n := n in range(len(dsts)..2) route packets for every nth connection to dsts[n].
for i := len(dsts); i >= 2; i-- {
dst := dsts[i-1] // the order in which rules for addrs are installed does not matter
if err := table.Append("nat", "PREROUTING", "--destination", origDst.String(), "-m", "statistic", "--mode", "nth", "--every", fmt.Sprint(i), "--packet", "0", "-j", "DNAT", "--to-destination", dst.String()); err != nil {
return fmt.Errorf("error adding DNAT rule for %s: %w", dst.String(), err)
}
}
// If the packet falls through to this rule, we route to the first destination in the list unconditionally.
return table.Append("nat", "PREROUTING", "--destination", origDst.String(), "-j", "DNAT", "--to-destination", dsts[0].String())
}
func (i *iptablesRunner) ClampMSSToPMTU(tun string, addr netip.Addr) error {
table := i.getIPTByAddr(addr)
return table.Append("mangle", "FORWARD", "-o", tun, "-p", "tcp", "--tcp-flags", "SYN,RST", "SYN", "-j", "TCPMSS", "--clamp-mss-to-pmtu")
}
// addBase6 adds some basic IPv6 processing rules to be
// supplemented by later calls to other helpers.
func (i *iptablesRunner) addBase6(tunname string) error {
// TODO: only allow traffic from Tailscale's ULA range to come
// from tailscale0.
// Explicitly allow all other inbound traffic to the tun interface
args := []string{"-i", tunname, "-j", "ACCEPT"}
if err := i.ipt6.Append("filter", "ts-input", args...); err != nil {
return fmt.Errorf("adding %v in v6/filter/ts-input: %w", args, err)
}
args = []string{"-i", tunname, "-j", "MARK", "--set-mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask}
if err := i.ipt6.Append("filter", "ts-forward", args...); err != nil {
return fmt.Errorf("adding %v in v6/filter/ts-forward: %w", args, err)
}
args = []string{"-m", "mark", "--mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask, "-j", "ACCEPT"}
if err := i.ipt6.Append("filter", "ts-forward", args...); err != nil {
return fmt.Errorf("adding %v in v6/filter/ts-forward: %w", args, err)
}
// TODO: drop forwarded traffic to tailscale0 from tailscale's ULA
// (see corresponding IPv4 CGNAT rule).
args = []string{"-o", tunname, "-j", "ACCEPT"}
if err := i.ipt6.Append("filter", "ts-forward", args...); err != nil {
return fmt.Errorf("adding %v in v6/filter/ts-forward: %w", args, err)
}
return nil
}
// DelChains removes the custom Tailscale chains from netfilter via iptables.
func (i *iptablesRunner) DelChains() error {
for _, ipt := range i.getTables() {
if err := delChain(ipt, "filter", "ts-input"); err != nil {
return err
}
if err := delChain(ipt, "filter", "ts-forward"); err != nil {
return err
}
}
for _, ipt := range i.getNATTables() {
if err := delChain(ipt, "nat", "ts-postrouting"); err != nil {
return err
}
}
return nil
}
// DelBase empties but does not remove custom Tailscale chains from
// netfilter via iptables.
func (i *iptablesRunner) DelBase() error {
del := func(ipt iptablesInterface, table, chain string) error {
if err := ipt.ClearChain(table, chain); err != nil {
if isNotExistError(err) {
// nonexistent chain. That's fine, since it's
// the desired state anyway.
return nil
}
return fmt.Errorf("flushing %s/%s: %w", table, chain, err)
}
return nil
}
for _, ipt := range i.getTables() {
if err := del(ipt, "filter", "ts-input"); err != nil {
return err
}
if err := del(ipt, "filter", "ts-forward"); err != nil {
return err
}
}
for _, ipt := range i.getNATTables() {
if err := del(ipt, "nat", "ts-postrouting"); err != nil {
return err
}
}
return nil
}
// DelHooks deletes the calls to tailscale's netfilter chains
// in the relevant main netfilter chains.
func (i *iptablesRunner) DelHooks(logf logger.Logf) error {
for _, ipt := range i.getTables() {
if err := delTSHook(ipt, "filter", "INPUT", logf); err != nil {
return err
}
if err := delTSHook(ipt, "filter", "FORWARD", logf); err != nil {
return err
}
}
for _, ipt := range i.getNATTables() {
if err := delTSHook(ipt, "nat", "POSTROUTING", logf); err != nil {
return err
}
}
return nil
}
// AddSNATRule adds a netfilter rule to SNAT traffic destined for
// local subnets.
func (i *iptablesRunner) AddSNATRule() error {
args := []string{"-m", "mark", "--mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask, "-j", "MASQUERADE"}
for _, ipt := range i.getNATTables() {
if err := ipt.Append("nat", "ts-postrouting", args...); err != nil {
return fmt.Errorf("adding %v in nat/ts-postrouting: %w", args, err)
}
}
return nil
}
// DelSNATRule removes the netfilter rule to SNAT traffic destined for
// local subnets. An error is returned if the rule does not exist.
func (i *iptablesRunner) DelSNATRule() error {
args := []string{"-m", "mark", "--mark", TailscaleSubnetRouteMark + "/" + TailscaleFwmarkMask, "-j", "MASQUERADE"}
for _, ipt := range i.getNATTables() {
if err := ipt.Delete("nat", "ts-postrouting", args...); err != nil {
return fmt.Errorf("deleting %v in nat/ts-postrouting: %w", args, err)
}
}
return nil
}
func statefulRuleArgs(tunname string) []string {
return []string{"-o", tunname, "-m", "conntrack", "!", "--ctstate", "ESTABLISHED,RELATED", "-j", "DROP"}
}
// AddStatefulRule adds a netfilter rule for stateful packet filtering using
// conntrack.
func (i *iptablesRunner) AddStatefulRule(tunname string) error {
// Drop packets that are destined for the tailscale interface if
// they're a new connection, per conntrack, to prevent hosts on the
// same subnet from being able to use this device as a way to forward
// packets on to the Tailscale network.
//
// The conntrack states are:
// NEW A packet which creates a new connection.
// ESTABLISHED A packet which belongs to an existing connection
// (i.e., a reply packet, or outgoing packet on a
// connection which has seen replies).
// RELATED A packet which is related to, but not part of, an
// existing connection, such as an ICMP error.
// INVALID A packet which could not be identified for some
// reason: this includes running out of memory and ICMP
// errors which don't correspond to any known
// connection. Generally these packets should be
// dropped.
//
// We drop NEW packets to prevent connections from coming "into"
// Tailscale from other hosts on the same network segment; we drop
// INVALID packets as well.
args := statefulRuleArgs(tunname)
for _, ipt := range i.getTables() {
// First, find the final "accept" rule.
rules, err := ipt.List("filter", "ts-forward")
if err != nil {
return fmt.Errorf("listing rules in filter/ts-forward: %w", err)
}
want := fmt.Sprintf("-A %s -o %s -j ACCEPT", "ts-forward", tunname)
pos := slices.Index(rules, want)
if pos < 0 {
return fmt.Errorf("couldn't find final ACCEPT rule in filter/ts-forward")
}
if err := ipt.Insert("filter", "ts-forward", pos, args...); err != nil {
return fmt.Errorf("adding %v in filter/ts-forward: %w", args, err)
}
}
return nil
}
// DelStatefulRule removes the netfilter rule for stateful packet filtering
// using conntrack.
func (i *iptablesRunner) DelStatefulRule(tunname string) error {
args := statefulRuleArgs(tunname)
for _, ipt := range i.getTables() {
if err := ipt.Delete("filter", "ts-forward", args...); err != nil {
return fmt.Errorf("deleting %v in filter/ts-forward: %w", args, err)
}
}
return nil
}
// buildMagicsockPortRule generates the string slice containing the arguments
// to describe a rule accepting traffic on a particular port to iptables. It is
// separated out here to avoid repetition in AddMagicsockPortRule and
// RemoveMagicsockPortRule, since it is important that the same rule is passed
// to Append() and Delete().
func buildMagicsockPortRule(port uint16) []string {
return []string{"-p", "udp", "--dport", strconv.FormatUint(uint64(port), 10), "-j", "ACCEPT"}
}
// AddMagicsockPortRule adds a rule to iptables to allow incoming traffic on
// the specified UDP port, so magicsock can accept incoming connections.
// network must be either "udp4" or "udp6" - this determines whether the rule
// is added for IPv4 or IPv6.
func (i *iptablesRunner) AddMagicsockPortRule(port uint16, network string) error {
var ipt iptablesInterface
switch network {
case "udp4":
ipt = i.ipt4
case "udp6":
ipt = i.ipt6
default:
return fmt.Errorf("unsupported network %s", network)
}
args := buildMagicsockPortRule(port)
if err := ipt.Append("filter", "ts-input", args...); err != nil {
return fmt.Errorf("adding %v in filter/ts-input: %w", args, err)
}
return nil
}
// DelMagicsockPortRule removes a rule added by AddMagicsockPortRule to accept
// incoming traffic on a particular UDP port.
// network must be either "udp4" or "udp6" - this determines whether the rule
// is removed for IPv4 or IPv6.
func (i *iptablesRunner) DelMagicsockPortRule(port uint16, network string) error {
var ipt iptablesInterface
switch network {
case "udp4":
ipt = i.ipt4
case "udp6":
ipt = i.ipt6
default:
return fmt.Errorf("unsupported network %s", network)
}
args := buildMagicsockPortRule(port)
if err := ipt.Delete("filter", "ts-input", args...); err != nil {
return fmt.Errorf("removing %v in filter/ts-input: %w", args, err)
}
return nil
}
// IPTablesCleanUp removes all Tailscale added iptables rules.
// Any errors that occur are logged to the provided logf.
func IPTablesCleanUp(logf logger.Logf) {
err := clearRules(iptables.ProtocolIPv4, logf)
if err != nil {
logf("linuxfw: clear iptables: %v", err)
}
err = clearRules(iptables.ProtocolIPv6, logf)
if err != nil {
logf("linuxfw: clear ip6tables: %v", err)
}
}
// delTSHook deletes hook in a chain that jumps to a ts-chain. If the hook does not
// exist, it's a no-op since the desired state is already achieved but we log the
// error because error code from the iptables module resists unwrapping.
func delTSHook(ipt iptablesInterface, table, chain string, logf logger.Logf) error {
tsChain := tsChain(chain)
args := []string{"-j", tsChain}
if err := ipt.Delete(table, chain, args...); err != nil && !isNotExistError(err) {
return fmt.Errorf("deleting %v in %s/%s: %v", args, table, chain, err)
}
return nil
}
// delChain flushs and deletes a chain. If the chain does not exist, it's a no-op
// since the desired state is already achieved. otherwise, it returns an error.
func delChain(ipt iptablesInterface, table, chain string) error {
if err := ipt.ClearChain(table, chain); err != nil {
if isNotExistError(err) {
// nonexistent chain. nothing to do.
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...)
}