mirror of
https://github.com/tailscale/tailscale.git
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c493e5804f
Signed-off-by: David Anderson <danderson@tailscale.com>
1028 lines
30 KiB
Go
1028 lines
30 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package router
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import (
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"bytes"
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"fmt"
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"io/ioutil"
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"os"
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"os/exec"
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"strconv"
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"strings"
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"github.com/coreos/go-iptables/iptables"
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"github.com/go-multierror/multierror"
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"github.com/tailscale/wireguard-go/device"
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"github.com/tailscale/wireguard-go/tun"
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"inet.af/netaddr"
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"tailscale.com/net/tsaddr"
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"tailscale.com/types/logger"
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"tailscale.com/version/distro"
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"tailscale.com/wgengine/router/dns"
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)
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// The following bits are added to packet marks for Tailscale use.
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//
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// We tried to pick bits sufficiently out of the way that it's
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// unlikely to collide with existing uses. We have 4 bytes of mark
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// bits to play with. We leave the lower byte alone on the assumption
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// that sysadmins would use those. Kubernetes uses a few bits in the
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// second byte, so we steer clear of that too.
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//
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// Empirically, most of the documentation on packet marks on the
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// internet gives the impression that the marks are 16 bits
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// wide. Based on this, we theorize that the upper two bytes are
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// relatively unused in the wild, and so we consume bits starting at
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// the 17th.
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//
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// The constants are in the iptables/iproute2 string format for
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// matching and setting the bits, so they can be directly embedded in
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// commands.
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const (
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// Packet is from Tailscale and to a subnet route destination, so
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// is allowed to be routed through this machine.
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tailscaleSubnetRouteMark = "0x40000"
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// Packet was originated by tailscaled itself, and must not be
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// routed over the Tailscale network.
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//
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// Keep this in sync with tailscaleBypassMark in
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// net/netns/netns_linux.go.
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tailscaleBypassMark = "0x80000"
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)
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// tailscaleRouteTable is the routing table number for Tailscale
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// network routes. See addIPRules for the detailed policy routing
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// logic that ends up doing lookups within that table.
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//
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// NOTE(danderson): We chose 52 because those are the digits above the
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// letters "TS" on a qwerty keyboard, and 52 is sufficiently unlikely
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// to be picked by other software.
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//
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// NOTE(danderson): You might wonder why we didn't pick some high
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// table number like 5252, to further avoid the potential for
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// collisions with other software. Unfortunately, Busybox's `ip`
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// implementation believes that table numbers are 8-bit integers, so
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// for maximum compatibility we have to stay in the 0-255 range even
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// though linux itself supports larger numbers.
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const tailscaleRouteTable = "52"
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// netfilterRunner abstracts helpers to run netfilter commands. It
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// exists purely to swap out go-iptables for a fake implementation in
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// tests.
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type netfilterRunner interface {
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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 linuxRouter struct {
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logf func(fmt string, args ...interface{})
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tunname string
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addrs map[netaddr.IPPrefix]bool
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routes map[netaddr.IPPrefix]bool
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snatSubnetRoutes bool
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netfilterMode NetfilterMode
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// Various feature checks for the network stack.
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ipRuleAvailable bool
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v6Available bool
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v6NATAvailable bool
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dns *dns.Manager
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ipt4 netfilterRunner
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ipt6 netfilterRunner
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cmd commandRunner
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}
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func newUserspaceRouter(logf logger.Logf, _ *device.Device, tunDev tun.Device) (Router, error) {
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tunname, err := tunDev.Name()
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if err != nil {
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return nil, err
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}
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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 := supportsV6()
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supportsV6NAT := supportsV6 && supportsV6NAT()
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var ipt6 netfilterRunner
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if supportsV6 {
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// The iptables package probes for `ip6tables` and errors out
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// if unavailable. We want that to be a non-fatal error.
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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 newUserspaceRouterAdvanced(logf, tunname, ipt4, ipt6, osCommandRunner{}, supportsV6, supportsV6NAT)
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}
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func newUserspaceRouterAdvanced(logf logger.Logf, tunname string, netfilter4, netfilter6 netfilterRunner, cmd commandRunner, supportsV6, supportsV6NAT bool) (Router, error) {
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ipRuleAvailable := (cmd.run("ip", "rule") == nil)
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mconfig := dns.ManagerConfig{
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Logf: logf,
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InterfaceName: tunname,
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}
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return &linuxRouter{
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logf: logf,
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tunname: tunname,
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netfilterMode: NetfilterOff,
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ipRuleAvailable: ipRuleAvailable,
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v6Available: supportsV6,
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v6NATAvailable: supportsV6NAT,
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ipt4: netfilter4,
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ipt6: netfilter6,
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cmd: cmd,
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dns: dns.NewManager(mconfig),
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}, nil
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}
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func (r *linuxRouter) Up() error {
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if err := r.delLegacyNetfilter(); err != nil {
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return err
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}
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if err := r.addIPRules(); err != nil {
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return err
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}
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if err := r.setNetfilterMode(NetfilterOff); err != nil {
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return err
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}
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if err := r.upInterface(); err != nil {
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return err
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}
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return nil
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}
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func (r *linuxRouter) Close() error {
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if err := r.dns.Down(); err != nil {
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return fmt.Errorf("dns down: %w", err)
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}
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if err := r.downInterface(); err != nil {
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return err
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}
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if err := r.delIPRules(); err != nil {
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return err
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}
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if err := r.setNetfilterMode(NetfilterOff); err != nil {
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return err
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}
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r.addrs = nil
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r.routes = nil
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return nil
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}
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// Set implements the Router interface.
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func (r *linuxRouter) Set(cfg *Config) error {
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var errs []error
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if cfg == nil {
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cfg = &shutdownConfig
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}
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if err := r.dns.Set(cfg.DNS); err != nil {
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errs = append(errs, fmt.Errorf("dns set: %w", err))
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}
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if err := r.setNetfilterMode(cfg.NetfilterMode); err != nil {
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errs = append(errs, err)
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}
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newRoutes, err := cidrDiff("route", r.routes, cfg.Routes, r.addRoute, r.delRoute, r.logf)
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if err != nil {
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errs = append(errs, err)
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}
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r.routes = newRoutes
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newAddrs, err := cidrDiff("addr", r.addrs, cfg.LocalAddrs, r.addAddress, r.delAddress, r.logf)
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if err != nil {
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errs = append(errs, err)
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}
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r.addrs = newAddrs
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switch {
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case cfg.SNATSubnetRoutes == r.snatSubnetRoutes:
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// state already correct, nothing to do.
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case cfg.SNATSubnetRoutes:
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if err := r.addSNATRule(); err != nil {
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errs = append(errs, err)
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}
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default:
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if err := r.delSNATRule(); err != nil {
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errs = append(errs, err)
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}
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}
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r.snatSubnetRoutes = cfg.SNATSubnetRoutes
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return multierror.New(errs)
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}
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// setNetfilterMode switches the router to the given netfilter
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// mode. Netfilter state is created or deleted appropriately to
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// reflect the new mode, and r.snatSubnetRoutes is updated to reflect
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// the current state of subnet SNATing.
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func (r *linuxRouter) setNetfilterMode(mode NetfilterMode) error {
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if distro.Get() == distro.Synology {
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mode = NetfilterOff
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}
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if r.netfilterMode == mode {
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return nil
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}
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// Depending on the netfilter mode we switch from and to, we may
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// have created the Tailscale netfilter chains. If so, we have to
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// go back through existing router state, and add the netfilter
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// rules for that state.
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//
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// This bool keeps track of whether the current state transition
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// is one that requires adding rules of existing state.
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reprocess := false
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switch mode {
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case NetfilterOff:
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switch r.netfilterMode {
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case NetfilterNoDivert:
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if err := r.delNetfilterBase(); err != nil {
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return err
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}
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if err := r.delNetfilterChains(); err != nil {
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r.logf("note: %v", err)
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// harmless, continue.
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// This can happen if someone left a ref to
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// this table somewhere else.
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}
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case NetfilterOn:
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if err := r.delNetfilterHooks(); err != nil {
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return err
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}
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if err := r.delNetfilterBase(); err != nil {
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return err
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}
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if err := r.delNetfilterChains(); err != nil {
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r.logf("note: %v", err)
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// harmless, continue.
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// This can happen if someone left a ref to
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// this table somewhere else.
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}
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}
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r.snatSubnetRoutes = false
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case NetfilterNoDivert:
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switch r.netfilterMode {
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case NetfilterOff:
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reprocess = true
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if err := r.addNetfilterChains(); err != nil {
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return err
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}
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if err := r.addNetfilterBase(); err != nil {
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return err
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}
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r.snatSubnetRoutes = false
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case NetfilterOn:
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if err := r.delNetfilterHooks(); err != nil {
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return err
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}
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}
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case NetfilterOn:
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// Because of bugs in old version of iptables-compat,
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// we can't add a "-j ts-forward" rule to FORWARD
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// while ts-forward contains an "-m mark" rule. But
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// we can add the row *before* populating ts-forward.
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// So we have to delNetFilterBase, then add the hooks,
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// then re-addNetFilterBase, just in case.
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switch r.netfilterMode {
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case NetfilterOff:
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reprocess = true
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if err := r.addNetfilterChains(); err != nil {
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return err
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}
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if err := r.delNetfilterBase(); err != nil {
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return err
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}
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if err := r.addNetfilterHooks(); err != nil {
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return err
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}
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if err := r.addNetfilterBase(); err != nil {
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return err
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}
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r.snatSubnetRoutes = false
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case NetfilterNoDivert:
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reprocess = true
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if err := r.delNetfilterBase(); err != nil {
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return err
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}
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if err := r.addNetfilterHooks(); err != nil {
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return err
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}
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if err := r.addNetfilterBase(); err != nil {
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return err
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}
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r.snatSubnetRoutes = false
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}
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default:
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panic("unhandled netfilter mode")
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}
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r.netfilterMode = mode
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if !reprocess {
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return nil
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}
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for cidr := range r.addrs {
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if err := r.addLoopbackRule(cidr.IP); 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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// addAddress adds an IP/mask to the tunnel interface. Fails if the
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// address is already assigned to the interface, or if the addition
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// fails.
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func (r *linuxRouter) addAddress(addr netaddr.IPPrefix) error {
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if err := r.cmd.run("ip", "addr", "add", addr.String(), "dev", r.tunname); err != nil {
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return fmt.Errorf("adding address %q to tunnel interface: %w", addr, err)
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}
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if err := r.addLoopbackRule(addr.IP); err != nil {
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return err
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}
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return nil
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}
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// delAddress removes an IP/mask from the tunnel interface. Fails if
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// the address is not assigned to the interface, or if the removal
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// fails.
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func (r *linuxRouter) delAddress(addr netaddr.IPPrefix) error {
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if err := r.delLoopbackRule(addr.IP); err != nil {
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return err
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}
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if err := r.cmd.run("ip", "addr", "del", addr.String(), "dev", r.tunname); err != nil {
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return fmt.Errorf("deleting address %q from tunnel interface: %w", addr, err)
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}
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return nil
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}
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// addLoopbackRule adds a firewall rule to permit loopback traffic to
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// a local Tailscale IP.
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func (r *linuxRouter) addLoopbackRule(addr netaddr.IP) error {
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if r.netfilterMode == NetfilterOff {
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return nil
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}
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if err := r.ipt4.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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// delLoopbackRule removes the firewall rule permitting loopback
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// traffic to a Tailscale IP.
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func (r *linuxRouter) delLoopbackRule(addr netaddr.IP) error {
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if r.netfilterMode == NetfilterOff {
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return nil
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}
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if err := r.ipt4.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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// addRoute adds a route for cidr, pointing to the tunnel
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// interface. Fails if the route already exists, or if adding the
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// route fails.
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func (r *linuxRouter) addRoute(cidr netaddr.IPPrefix) error {
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args := []string{
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"ip", "route", "add",
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normalizeCIDR(cidr),
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"dev", r.tunname,
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}
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if r.ipRuleAvailable {
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args = append(args, "table", tailscaleRouteTable)
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}
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return r.cmd.run(args...)
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}
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// delRoute removes the route for cidr pointing to the tunnel
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// interface. Fails if the route doesn't exist, or if removing the
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// route fails.
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func (r *linuxRouter) delRoute(cidr netaddr.IPPrefix) error {
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args := []string{
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"ip", "route", "del",
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normalizeCIDR(cidr),
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"dev", r.tunname,
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}
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if r.ipRuleAvailable {
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args = append(args, "table", tailscaleRouteTable)
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}
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return r.cmd.run(args...)
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}
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// upInterface brings up the tunnel interface.
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func (r *linuxRouter) upInterface() error {
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return r.cmd.run("ip", "link", "set", "dev", r.tunname, "up")
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}
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// downInterface sets the tunnel interface administratively down.
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func (r *linuxRouter) downInterface() error {
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return r.cmd.run("ip", "link", "set", "dev", r.tunname, "down")
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}
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func (r *linuxRouter) iprouteFamilies() []string {
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if r.v6Available {
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return []string{"-4", "-6"}
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}
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return []string{"-4"}
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}
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// addIPRules adds the policy routing rule that avoids tailscaled
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// routing loops. If the rule exists and appears to be a
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// tailscale-managed rule, it is gracefully replaced.
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func (r *linuxRouter) addIPRules() error {
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if !r.ipRuleAvailable {
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return nil
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}
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// Clear out old rules. After that, any error adding a rule is fatal,
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// because there should be no reason we add a duplicate.
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if err := r.delIPRules(); err != nil {
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return err
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}
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rg := newRunGroup(nil, r.cmd)
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for _, family := range r.iprouteFamilies() {
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// NOTE(apenwarr): We leave spaces between each pref number.
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// This is so the sysadmin can override by inserting rules in
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// between if they want.
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// NOTE(apenwarr): This sequence seems complicated, right?
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// If we could simply have a rule that said "match packets that
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// *don't* have this fwmark", then we would only need to add one
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// link to table 52 and we'd be done. Unfortunately, older kernels
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// and 'ip rule' implementations (including busybox), don't support
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// checking for the lack of a fwmark, only the presence. The technique
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// below works even on very old kernels.
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// Packets from us, tagged with our fwmark, first try the kernel's
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// main routing table.
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rg.Run(
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"ip", family, "rule", "add",
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"pref", tailscaleRouteTable+"10",
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"fwmark", tailscaleBypassMark,
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"table", "main",
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)
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// ...and then we try the 'default' table, for correctness,
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// even though it's been empty on every Linux system I've ever seen.
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rg.Run(
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"ip", family, "rule", "add",
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"pref", tailscaleRouteTable+"30",
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"fwmark", tailscaleBypassMark,
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"table", "default",
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)
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// If neither of those matched (no default route on this system?)
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// then packets from us should be aborted rather than falling through
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// to the tailscale routes, because that would create routing loops.
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rg.Run(
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"ip", family, "rule", "add",
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"pref", tailscaleRouteTable+"50",
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"fwmark", tailscaleBypassMark,
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"type", "unreachable",
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)
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// If we get to this point, capture all packets and send them
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// through to the tailscale route table. For apps other than us
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// (ie. with no fwmark set), this is the first routing table, so
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// it takes precedence over all the others, ie. VPN routes always
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// beat non-VPN routes.
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//
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// NOTE(apenwarr): tables >255 are not supported in busybox, so we
|
|
// can't use a table number that aligns with the rule preferences.
|
|
rg.Run(
|
|
"ip", family, "rule", "add",
|
|
"pref", tailscaleRouteTable+"70",
|
|
"table", tailscaleRouteTable,
|
|
)
|
|
// If that didn't match, then non-fwmark packets fall through to the
|
|
// usual rules (pref 32766 and 32767, ie. main and default).
|
|
}
|
|
|
|
return rg.ErrAcc
|
|
}
|
|
|
|
// delBypassrule removes the policy routing rules that avoid
|
|
// tailscaled routing loops, if it exists.
|
|
func (r *linuxRouter) delIPRules() error {
|
|
if !r.ipRuleAvailable {
|
|
return nil
|
|
}
|
|
|
|
// Error codes: 'ip rule' returns error code 2 if the rule is a
|
|
// duplicate (add) or not found (del). It returns a different code
|
|
// for syntax errors. This is also true of busybox.
|
|
//
|
|
// Some older versions of iproute2 also return error code 254 for
|
|
// unknown rules during deletion.
|
|
rg := newRunGroup([]int{2, 254}, r.cmd)
|
|
|
|
for _, family := range r.iprouteFamilies() {
|
|
// When deleting rules, we want to be a bit specific (mention which
|
|
// table we were routing to) but not *too* specific (fwmarks, etc).
|
|
// That leaves us some flexibility to change these values in later
|
|
// versions without having ongoing hacks for every possible
|
|
// combination.
|
|
|
|
// Delete old-style tailscale rules
|
|
// (never released in a stable version, so we can drop this
|
|
// support eventually).
|
|
rg.Run(
|
|
"ip", family, "rule", "del",
|
|
"pref", "10000",
|
|
"table", "main",
|
|
)
|
|
|
|
// Delete new-style tailscale rules.
|
|
rg.Run(
|
|
"ip", family, "rule", "del",
|
|
"pref", tailscaleRouteTable+"10",
|
|
"table", "main",
|
|
)
|
|
rg.Run(
|
|
"ip", family, "rule", "del",
|
|
"pref", tailscaleRouteTable+"30",
|
|
"table", "default",
|
|
)
|
|
rg.Run(
|
|
"ip", family, "rule", "del",
|
|
"pref", tailscaleRouteTable+"50",
|
|
"type", "unreachable",
|
|
)
|
|
rg.Run(
|
|
"ip", family, "rule", "del",
|
|
"pref", tailscaleRouteTable+"70",
|
|
"table", tailscaleRouteTable,
|
|
)
|
|
}
|
|
|
|
return rg.ErrAcc
|
|
}
|
|
|
|
func (r *linuxRouter) netfilterFamilies() []netfilterRunner {
|
|
if r.v6Available {
|
|
return []netfilterRunner{r.ipt4, r.ipt6}
|
|
}
|
|
return []netfilterRunner{r.ipt4}
|
|
}
|
|
|
|
// addNetfilterChains creates custom Tailscale chains in netfilter.
|
|
func (r *linuxRouter) addNetfilterChains() error {
|
|
create := func(ipt netfilterRunner, table, chain string) error {
|
|
err := ipt.ClearChain(table, chain)
|
|
if errCode(err) == 1 {
|
|
// 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 r.netfilterFamilies() {
|
|
if err := create(ipt, "filter", "ts-input"); err != nil {
|
|
return err
|
|
}
|
|
if err := create(ipt, "filter", "ts-forward"); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
if err := create(r.ipt4, "nat", "ts-postrouting"); err != nil {
|
|
return err
|
|
}
|
|
if r.v6NATAvailable {
|
|
if err := create(r.ipt6, "nat", "ts-postrouting"); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// addNetfilterBase adds some basic processing rules to be
|
|
// supplemented by later calls to other helpers.
|
|
func (r *linuxRouter) addNetfilterBase() error {
|
|
if err := r.addNetfilterBase4(); err != nil {
|
|
return err
|
|
}
|
|
if r.v6Available {
|
|
if err := r.addNetfilterBase6(); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// addNetfilterBase4 adds some basic IPv4 processing rules to be
|
|
// supplemented by later calls to other helpers.
|
|
func (r *linuxRouter) addNetfilterBase4() 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", r.tunname, "-s", tsaddr.ChromeOSVMRange().String(), "-j", "RETURN"}
|
|
if err := r.ipt4.Append("filter", "ts-input", args...); err != nil {
|
|
return fmt.Errorf("adding %v in v4/filter/ts-input: %w", args, err)
|
|
}
|
|
args = []string{"!", "-i", r.tunname, "-s", tsaddr.CGNATRange().String(), "-j", "DROP"}
|
|
if err := r.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", r.tunname, "-j", "MARK", "--set-mark", tailscaleSubnetRouteMark}
|
|
if err := r.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, "-j", "ACCEPT"}
|
|
if err := r.ipt4.Append("filter", "ts-forward", args...); err != nil {
|
|
return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
|
|
}
|
|
args = []string{"-o", r.tunname, "-s", tsaddr.CGNATRange().String(), "-j", "DROP"}
|
|
if err := r.ipt4.Append("filter", "ts-forward", args...); err != nil {
|
|
return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
|
|
}
|
|
args = []string{"-o", r.tunname, "-j", "ACCEPT"}
|
|
if err := r.ipt4.Append("filter", "ts-forward", args...); err != nil {
|
|
return fmt.Errorf("adding %v in v4/filter/ts-forward: %w", args, err)
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// addNetfilterBase4 adds some basic IPv6 processing rules to be
|
|
// supplemented by later calls to other helpers.
|
|
func (r *linuxRouter) addNetfilterBase6() error {
|
|
// TODO: only allow traffic from Tailscale's ULA range to come
|
|
// from tailscale0.
|
|
|
|
args := []string{"-i", r.tunname, "-j", "MARK", "--set-mark", tailscaleSubnetRouteMark}
|
|
if err := r.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, "-j", "ACCEPT"}
|
|
if err := r.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", r.tunname, "-j", "ACCEPT"}
|
|
if err := r.ipt6.Append("filter", "ts-forward", args...); err != nil {
|
|
return fmt.Errorf("adding %v in v6/filter/ts-forward: %w", args, err)
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// delNetfilterChains removes the custom Tailscale chains from netfilter.
|
|
func (r *linuxRouter) delNetfilterChains() error {
|
|
del := func(ipt netfilterRunner, table, chain string) error {
|
|
if err := ipt.ClearChain(table, chain); err != nil {
|
|
if errCode(err) == 1 {
|
|
// nonexistent chain. That's fine, since it's
|
|
// the desired state anyway.
|
|
return nil
|
|
}
|
|
return fmt.Errorf("flushing %s/%s: %w", table, chain, err)
|
|
}
|
|
if err := ipt.DeleteChain(table, chain); err != nil {
|
|
// this shouldn't fail, because if the chain didn't
|
|
// exist, we would have returned after ClearChain.
|
|
return fmt.Errorf("deleting %s/%s: %v", table, chain, err)
|
|
}
|
|
return nil
|
|
}
|
|
|
|
for _, ipt := range r.netfilterFamilies() {
|
|
if err := del(ipt, "filter", "ts-input"); err != nil {
|
|
return err
|
|
}
|
|
if err := del(ipt, "filter", "ts-forward"); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
if err := del(r.ipt4, "nat", "ts-postrouting"); err != nil {
|
|
return err
|
|
}
|
|
if r.v6NATAvailable {
|
|
if err := del(r.ipt6, "nat", "ts-postrouting"); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// delNetfilterBase empties but does not remove custom Tailscale chains from
|
|
// netfilter.
|
|
func (r *linuxRouter) delNetfilterBase() error {
|
|
del := func(ipt netfilterRunner, table, chain string) error {
|
|
if err := ipt.ClearChain(table, chain); err != nil {
|
|
if errCode(err) == 1 {
|
|
// 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 r.netfilterFamilies() {
|
|
if err := del(ipt, "filter", "ts-input"); err != nil {
|
|
return err
|
|
}
|
|
if err := del(ipt, "filter", "ts-forward"); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
if err := del(r.ipt4, "nat", "ts-postrouting"); err != nil {
|
|
return err
|
|
}
|
|
if r.v6NATAvailable {
|
|
if err := del(r.ipt6, "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(ipt netfilterRunner, 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 r.netfilterFamilies() {
|
|
if err := divert(ipt, "filter", "INPUT"); err != nil {
|
|
return err
|
|
}
|
|
if err := divert(ipt, "filter", "FORWARD"); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
if err := divert(r.ipt4, "nat", "POSTROUTING"); err != nil {
|
|
return err
|
|
}
|
|
if r.v6NATAvailable {
|
|
if err := divert(r.ipt6, "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(ipt netfilterRunner, table, chain string) error {
|
|
tsChain := tsChain(chain)
|
|
args := []string{"-j", tsChain}
|
|
if err := ipt.Delete(table, chain, args...); err != nil {
|
|
// TODO(apenwarr): check for errCode(1) here.
|
|
// Unfortunately the error code from the iptables
|
|
// module resists unwrapping, unlike with other
|
|
// calls. So we have to assume if Delete fails,
|
|
// it's because there is no such rule.
|
|
r.logf("note: deleting %v in %s/%s: %w", args, table, chain, err)
|
|
return nil
|
|
}
|
|
return nil
|
|
}
|
|
|
|
for _, ipt := range r.netfilterFamilies() {
|
|
if err := del(ipt, "filter", "INPUT"); err != nil {
|
|
return err
|
|
}
|
|
if err := del(ipt, "filter", "FORWARD"); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
if err := del(r.ipt4, "nat", "POSTROUTING"); err != nil {
|
|
return err
|
|
}
|
|
if r.v6NATAvailable {
|
|
if err := del(r.ipt6, "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 v4/nat/ts-postrouting: %w", args, err)
|
|
}
|
|
if r.v6NATAvailable {
|
|
if err := r.ipt6.Append("nat", "ts-postrouting", args...); err != nil {
|
|
return fmt.Errorf("adding %v in v6/nat/ts-postrouting: %w", args, err)
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// 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 v4/nat/ts-postrouting: %w", args, err)
|
|
}
|
|
if r.v6NATAvailable {
|
|
if err := r.ipt6.Delete("nat", "ts-postrouting", args...); err != nil {
|
|
return fmt.Errorf("deleting %v in v6/nat/ts-postrouting: %w", 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: %w", args, table, chain, err)
|
|
}
|
|
if exists {
|
|
if err := r.ipt4.Delete(table, chain, args...); err != nil {
|
|
return fmt.Errorf("deleting %v in %s/%s: %w", args, table, chain, err)
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
if err := del("filter", "FORWARD", "-m", "comment", "--comment", "tailscale", "-i", r.tunname, "-j", "ACCEPT"); err != nil {
|
|
r.logf("failed to delete legacy rule, continuing anyway: %v", err)
|
|
}
|
|
if err := del("nat", "POSTROUTING", "-m", "comment", "--comment", "tailscale", "-o", "eth0", "-j", "MASQUERADE"); err != nil {
|
|
r.logf("failed to delete legacy rule, continuing anyway: %v", 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)
|
|
}
|
|
|
|
func cleanup(logf logger.Logf, interfaceName string) {
|
|
// TODO(dmytro): clean up iptables.
|
|
}
|
|
|
|
// supportsV6 returns whether the system appears to have a working
|
|
// IPv6 network stack.
|
|
func supportsV6() bool {
|
|
_, err := os.Stat("/proc/sys/net/ipv6")
|
|
if os.IsNotExist(err) {
|
|
return false
|
|
}
|
|
bs, err := ioutil.ReadFile("/proc/sys/net/ipv6/conf/all/disable_ipv6")
|
|
if err != nil {
|
|
// Be conservative if we can't find the ipv6 configuration knob.
|
|
return false
|
|
}
|
|
disabled, err := strconv.ParseBool(strings.TrimSpace(string(bs)))
|
|
if err != nil {
|
|
return false
|
|
}
|
|
if disabled {
|
|
return false
|
|
}
|
|
|
|
// Some distros ship ip6tables separately from iptables.
|
|
if _, err := exec.LookPath("ip6tables"); err != nil {
|
|
return false
|
|
}
|
|
|
|
return true
|
|
}
|
|
|
|
// supportsV6NAT 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.
|
|
func supportsV6NAT() bool {
|
|
bs, err := ioutil.ReadFile("/proc/net/ip6_tables_names")
|
|
if err != nil {
|
|
// Can't read the file. Assume SNAT works.
|
|
return true
|
|
}
|
|
|
|
return bytes.Contains(bs, []byte("nat\n"))
|
|
}
|