mirror of
https://github.com/tailscale/tailscale.git
synced 2024-12-04 23:45:34 +00:00
4a531a0aed
Signed-off-by: Maisem Ali <maisem@tailscale.com>
(cherry picked from commit 53199738fb
)
1304 lines
38 KiB
Go
1304 lines
38 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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"errors"
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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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"time"
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"github.com/coreos/go-iptables/iptables"
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"github.com/go-multierror/multierror"
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"golang.org/x/time/rate"
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"golang.zx2c4.com/wireguard/tun"
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"inet.af/netaddr"
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"tailscale.com/net/tsaddr"
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"tailscale.com/syncs"
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"tailscale.com/types/logger"
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"tailscale.com/types/preftype"
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"tailscale.com/version/distro"
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"tailscale.com/wgengine/monitor"
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)
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const (
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netfilterOff = preftype.NetfilterOff
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netfilterNoDivert = preftype.NetfilterNoDivert
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netfilterOn = preftype.NetfilterOn
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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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const (
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defaultRouteTable = "default"
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mainRouteTable = "main"
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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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tailscaleRouteTable = "52"
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)
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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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closed syncs.AtomicBool
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logf func(fmt string, args ...interface{})
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tunname string
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linkMon *monitor.Mon
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unregLinkMon func()
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addrs map[netaddr.IPPrefix]bool
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routes map[netaddr.IPPrefix]bool
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localRoutes map[netaddr.IPPrefix]bool
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snatSubnetRoutes bool
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netfilterMode preftype.NetfilterMode
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// ruleRestorePending is whether a timer has been started to
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// restore deleted ip rules.
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ruleRestorePending syncs.AtomicBool
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ipRuleFixLimiter *rate.Limiter
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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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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, tunDev tun.Device, linkMon *monitor.Mon) (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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v6err := checkIPv6()
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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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}
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supportsV6 := v6err == nil
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supportsV6NAT := supportsV6 && supportsV6NAT()
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if supportsV6 {
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logf("v6nat = %v", supportsV6NAT)
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}
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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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cmd := osCommandRunner{
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ambientCapNetAdmin: useAmbientCaps(),
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}
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return newUserspaceRouterAdvanced(logf, tunname, linkMon, ipt4, ipt6, cmd, supportsV6, supportsV6NAT)
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}
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func newUserspaceRouterAdvanced(logf logger.Logf, tunname string, linkMon *monitor.Mon, netfilter4, netfilter6 netfilterRunner, cmd commandRunner, supportsV6, supportsV6NAT bool) (Router, error) {
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ipRuleAvailable := (cmd.run("ip", "rule") == nil)
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r := &linuxRouter{
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logf: logf,
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tunname: tunname,
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netfilterMode: netfilterOff,
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linkMon: linkMon,
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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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ipRuleFixLimiter: rate.NewLimiter(rate.Every(5*time.Second), 10),
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}
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return r, nil
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}
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func useAmbientCaps() bool {
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if distro.Get() != distro.Synology {
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return false
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}
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v, err := strconv.Atoi(os.Getenv("SYNOPKG_DSM_VERSION_MAJOR"))
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if err != nil {
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return false
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}
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return v >= 7
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}
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// onIPRuleDeleted is the callback from the link monitor for when an IP policy
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// rule is deleted. See Issue 1591.
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//
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// If an ip rule is deleted (with pref number 52xx, as Tailscale sets), then
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// set a timer to restore our rules, in case they were deleted. The timer lets
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// us do one fixup in response to a batch of rule deletes. It also lets us
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// delay arbitrarily to prevent a high-speed fight over the rule between
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// competiting processes. (Although empirically, systemd doesn't fight us
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// like that... yet.)
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//
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// Note that we don't care about the table number. We don't strictly even care
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// about the priority number. We could just do this in response to any netlink
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// change. Filtering by known priority ranges cuts back on some logspam.
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func (r *linuxRouter) onIPRuleDeleted(table uint8, priority uint32) {
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if priority < 5200 || priority >= 5300 {
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// Not our rule.
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return
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}
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if !r.ruleRestorePending.Swap(true) {
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// Another timer is already pending.
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return
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}
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rr := r.ipRuleFixLimiter.Reserve()
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if !rr.OK() {
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r.ruleRestorePending.Swap(false)
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return
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}
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time.AfterFunc(rr.Delay()+250*time.Millisecond, func() {
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if r.ruleRestorePending.Swap(false) && !r.closed.Get() {
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r.logf("somebody (likely systemd-networkd) deleted ip rules; restoring Tailscale's")
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r.justAddIPRules()
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}
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})
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}
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func (r *linuxRouter) Up() error {
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if r.unregLinkMon == nil && r.linkMon != nil {
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r.unregLinkMon = r.linkMon.RegisterRuleDeleteCallback(r.onIPRuleDeleted)
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}
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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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r.closed.Set(true)
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if r.unregLinkMon != nil {
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r.unregLinkMon()
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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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if err := r.delRoutes(); 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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r.localRoutes = 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.setNetfilterMode(cfg.NetfilterMode); err != nil {
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errs = append(errs, err)
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}
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newLocalRoutes, err := cidrDiff("localRoute", r.localRoutes, cfg.LocalRoutes, r.addThrowRoute, r.delThrowRoute, 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.localRoutes = newLocalRoutes
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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 preftype.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 !r.v6Available && addr.IP().Is6() {
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return nil
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}
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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 !r.v6Available && addr.IP().Is6() {
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return nil
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}
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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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nf := r.ipt4
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if addr.Is6() {
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if !r.v6Available {
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// IPv6 not available, ignore.
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return nil
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}
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nf = r.ipt6
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}
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if err := nf.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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nf := r.ipt4
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if addr.Is6() {
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if !r.v6Available {
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// IPv6 not available, ignore.
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return nil
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}
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nf = r.ipt6
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}
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if err := nf.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
|
|
// route fails.
|
|
func (r *linuxRouter) addRoute(cidr netaddr.IPPrefix) error {
|
|
return r.addRouteDef([]string{normalizeCIDR(cidr), "dev", r.tunname}, cidr)
|
|
}
|
|
|
|
// addThrowRoute adds a throw route for the provided cidr.
|
|
// This has the effect that lookup in the routing table is terminated
|
|
// pretending that no route was found. Fails if the route already exists,
|
|
// or if adding the route fails.
|
|
func (r *linuxRouter) addThrowRoute(cidr netaddr.IPPrefix) error {
|
|
if !r.ipRuleAvailable {
|
|
return nil
|
|
}
|
|
return r.addRouteDef([]string{"throw", normalizeCIDR(cidr)}, cidr)
|
|
}
|
|
|
|
func (r *linuxRouter) addRouteDef(routeDef []string, cidr netaddr.IPPrefix) error {
|
|
if !r.v6Available && cidr.IP().Is6() {
|
|
return nil
|
|
}
|
|
args := append([]string{"ip", "route", "add"}, routeDef...)
|
|
if r.ipRuleAvailable {
|
|
args = append(args, "table", tailscaleRouteTable)
|
|
}
|
|
err := r.cmd.run(args...)
|
|
if err == nil {
|
|
return nil
|
|
}
|
|
|
|
// TODO(bradfitz): remove this ugly hack to detect failure to
|
|
// add a route that already exists (as happens in when we're
|
|
// racing to add kernel-maintained routes when enabling exit
|
|
// nodes w/o Local LAN access, Issue 3060) and use netlink
|
|
// directly instead (Issue 391).
|
|
if errCode(err) == 2 && strings.Contains(err.Error(), "RTNETLINK answers: File exists") {
|
|
r.logf("ignoring route add of %v; already exists", cidr)
|
|
return nil
|
|
}
|
|
return err
|
|
}
|
|
|
|
// delRoute removes the route for cidr pointing to the tunnel
|
|
// interface. Fails if the route doesn't exist, or if removing the
|
|
// route fails.
|
|
func (r *linuxRouter) delRoute(cidr netaddr.IPPrefix) error {
|
|
return r.delRouteDef([]string{normalizeCIDR(cidr), "dev", r.tunname}, cidr)
|
|
}
|
|
|
|
// delThrowRoute removes the throw route for the cidr. Fails if the route
|
|
// doesn't exist, or if removing the route fails.
|
|
func (r *linuxRouter) delThrowRoute(cidr netaddr.IPPrefix) error {
|
|
if !r.ipRuleAvailable {
|
|
return nil
|
|
}
|
|
return r.delRouteDef([]string{"throw", normalizeCIDR(cidr)}, cidr)
|
|
}
|
|
|
|
func (r *linuxRouter) delRouteDef(routeDef []string, cidr netaddr.IPPrefix) error {
|
|
if !r.v6Available && cidr.IP().Is6() {
|
|
return nil
|
|
}
|
|
args := append([]string{"ip", "route", "del"}, routeDef...)
|
|
if r.ipRuleAvailable {
|
|
args = append(args, "table", tailscaleRouteTable)
|
|
}
|
|
err := r.cmd.run(args...)
|
|
if err != nil {
|
|
ok, err := r.hasRoute(routeDef, cidr)
|
|
if err != nil {
|
|
r.logf("warning: error checking whether %v even exists after error deleting it: %v", err)
|
|
} else {
|
|
if !ok {
|
|
r.logf("warning: tried to delete route %v but it was already gone; ignoring error", cidr)
|
|
return nil
|
|
}
|
|
}
|
|
}
|
|
return err
|
|
}
|
|
|
|
func dashFam(ip netaddr.IP) string {
|
|
if ip.Is6() {
|
|
return "-6"
|
|
}
|
|
return "-4"
|
|
}
|
|
|
|
func (r *linuxRouter) hasRoute(routeDef []string, cidr netaddr.IPPrefix) (bool, error) {
|
|
args := append([]string{"ip", dashFam(cidr.IP()), "route", "show"}, routeDef...)
|
|
if r.ipRuleAvailable {
|
|
args = append(args, "table", tailscaleRouteTable)
|
|
}
|
|
out, err := r.cmd.output(args...)
|
|
if err != nil {
|
|
return false, err
|
|
}
|
|
return len(out) > 0, nil
|
|
}
|
|
|
|
// upInterface brings up the tunnel interface.
|
|
func (r *linuxRouter) upInterface() error {
|
|
return r.cmd.run("ip", "link", "set", "dev", r.tunname, "up")
|
|
}
|
|
|
|
// downInterface sets the tunnel interface administratively down.
|
|
func (r *linuxRouter) downInterface() error {
|
|
return r.cmd.run("ip", "link", "set", "dev", r.tunname, "down")
|
|
}
|
|
|
|
func (r *linuxRouter) iprouteFamilies() []string {
|
|
if r.v6Available {
|
|
return []string{"-4", "-6"}
|
|
}
|
|
return []string{"-4"}
|
|
}
|
|
|
|
// addIPRules adds the policy routing rule that avoids tailscaled
|
|
// routing loops. If the rule exists and appears to be a
|
|
// tailscale-managed rule, it is gracefully replaced.
|
|
func (r *linuxRouter) addIPRules() error {
|
|
if !r.ipRuleAvailable {
|
|
return nil
|
|
}
|
|
|
|
// Clear out old rules. After that, any error adding a rule is fatal,
|
|
// because there should be no reason we add a duplicate.
|
|
if err := r.delIPRules(); err != nil {
|
|
return err
|
|
}
|
|
|
|
return r.justAddIPRules()
|
|
}
|
|
|
|
// justAddIPRules adds policy routing rule without deleting any first.
|
|
func (r *linuxRouter) justAddIPRules() error {
|
|
if !r.ipRuleAvailable {
|
|
return nil
|
|
}
|
|
|
|
rg := newRunGroup(nil, r.cmd)
|
|
|
|
for _, family := range r.iprouteFamilies() {
|
|
// NOTE(apenwarr): We leave spaces between each pref number.
|
|
// This is so the sysadmin can override by inserting rules in
|
|
// between if they want.
|
|
|
|
// NOTE(apenwarr): This sequence seems complicated, right?
|
|
// If we could simply have a rule that said "match packets that
|
|
// *don't* have this fwmark", then we would only need to add one
|
|
// link to table 52 and we'd be done. Unfortunately, older kernels
|
|
// and 'ip rule' implementations (including busybox), don't support
|
|
// checking for the lack of a fwmark, only the presence. The technique
|
|
// below works even on very old kernels.
|
|
|
|
// Packets from us, tagged with our fwmark, first try the kernel's
|
|
// main routing table.
|
|
rg.Run(
|
|
"ip", family, "rule", "add",
|
|
"pref", tailscaleRouteTable+"10",
|
|
"fwmark", tailscaleBypassMark,
|
|
"table", mainRouteTable,
|
|
)
|
|
// ...and then we try the 'default' table, for correctness,
|
|
// even though it's been empty on every Linux system I've ever seen.
|
|
rg.Run(
|
|
"ip", family, "rule", "add",
|
|
"pref", tailscaleRouteTable+"30",
|
|
"fwmark", tailscaleBypassMark,
|
|
"table", defaultRouteTable,
|
|
)
|
|
// If neither of those matched (no default route on this system?)
|
|
// then packets from us should be aborted rather than falling through
|
|
// to the tailscale routes, because that would create routing loops.
|
|
rg.Run(
|
|
"ip", family, "rule", "add",
|
|
"pref", tailscaleRouteTable+"50",
|
|
"fwmark", tailscaleBypassMark,
|
|
"type", "unreachable",
|
|
)
|
|
// If we get to this point, capture all packets and send them
|
|
// through to the tailscale route table. For apps other than us
|
|
// (ie. with no fwmark set), this is the first routing table, so
|
|
// it takes precedence over all the others, ie. VPN routes always
|
|
// beat non-VPN routes.
|
|
//
|
|
// 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
|
|
}
|
|
|
|
// delRoutes removes any local routes that we added that would not be
|
|
// cleaned up on interface down.
|
|
func (r *linuxRouter) delRoutes() error {
|
|
for rt := range r.localRoutes {
|
|
if err := r.delThrowRoute(rt); err != nil {
|
|
r.logf("failed to delete throw route(%q): %v", rt, err)
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// delIPRules 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 {
|
|
if distro.Get() == distro.Synology {
|
|
// We don't support netfilter on Synology, and unlike other platforms
|
|
// the following commands error out as the `comment` module doesn't
|
|
// exist in the iptables binary present on Synology. Albeit the errors
|
|
// are ignored it's nice to not have logspam.
|
|
return nil
|
|
}
|
|
|
|
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
|
|
}
|
|
|
|
var delFail []error
|
|
for cidr := range old {
|
|
if newMap[cidr] {
|
|
continue
|
|
}
|
|
if err := del(cidr); err != nil {
|
|
logf("%s del failed: %v", kind, err)
|
|
delFail = append(delFail, err)
|
|
} else {
|
|
delete(ret, cidr)
|
|
}
|
|
}
|
|
if len(delFail) == 1 {
|
|
return ret, delFail[0]
|
|
}
|
|
if len(delFail) > 0 {
|
|
return ret, fmt.Errorf("%d delete %s failures; first was: %w", len(delFail), kind, delFail[0])
|
|
}
|
|
|
|
var addFail []error
|
|
for cidr := range newMap {
|
|
if old[cidr] {
|
|
continue
|
|
}
|
|
if err := add(cidr); err != nil {
|
|
logf("%s add failed: %v", kind, err)
|
|
addFail = append(addFail, err)
|
|
} else {
|
|
ret[cidr] = true
|
|
}
|
|
}
|
|
|
|
if len(addFail) == 1 {
|
|
return ret, addFail[0]
|
|
}
|
|
if len(addFail) > 0 {
|
|
return ret, fmt.Errorf("%d add %s failures; first was: %w", len(addFail), kind, addFail[0])
|
|
}
|
|
|
|
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 {
|
|
return cidr.Masked().String()
|
|
}
|
|
|
|
func cleanup(logf logger.Logf, interfaceName string) {
|
|
// TODO(dmytro): clean up iptables.
|
|
}
|
|
|
|
// checkIPv6 checks whether the system appears to have a working IPv6
|
|
// network stack. It returns an error explaining what looks wrong or
|
|
// missing. It does not check that IPv6 is currently functional or
|
|
// that there's a global address, just that the system would support
|
|
// IPv6 if it were on an IPv6 network.
|
|
func checkIPv6() error {
|
|
_, err := os.Stat("/proc/sys/net/ipv6")
|
|
if os.IsNotExist(err) {
|
|
return err
|
|
}
|
|
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 err
|
|
}
|
|
disabled, err := strconv.ParseBool(strings.TrimSpace(string(bs)))
|
|
if err != nil {
|
|
return errors.New("disable_ipv6 has invalid bool")
|
|
}
|
|
if disabled {
|
|
return errors.New("disable_ipv6 is set")
|
|
}
|
|
|
|
// Older kernels don't support IPv6 policy routing. Some kernels
|
|
// support policy routing but don't have this knob, so absence of
|
|
// the knob is not fatal.
|
|
bs, err = ioutil.ReadFile("/proc/sys/net/ipv6/conf/all/disable_policy")
|
|
if err == nil {
|
|
disabled, err = strconv.ParseBool(strings.TrimSpace(string(bs)))
|
|
if err != nil {
|
|
return errors.New("disable_policy has invalid bool")
|
|
}
|
|
if disabled {
|
|
return errors.New("disable_policy is set")
|
|
}
|
|
}
|
|
|
|
if err := checkIPRuleSupportsV6(); err != nil {
|
|
return fmt.Errorf("kernel doesn't support IPv6 policy routing: %w", err)
|
|
}
|
|
|
|
// Some distros ship ip6tables separately from iptables.
|
|
if _, err := exec.LookPath("ip6tables"); err != nil {
|
|
return err
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// 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"))
|
|
}
|
|
|
|
func checkIPRuleSupportsV6() error {
|
|
add := []string{"-6", "rule", "add", "pref", "1234", "fwmark", tailscaleBypassMark, "table", tailscaleRouteTable}
|
|
del := []string{"-6", "rule", "del", "pref", "1234", "fwmark", tailscaleBypassMark, "table", tailscaleRouteTable}
|
|
|
|
// First delete the rule unconditionally, and don't check for
|
|
// errors. This is just cleaning up anything that might be already
|
|
// there.
|
|
exec.Command("ip", del...).Run()
|
|
|
|
// Try adding the rule. This will fail on systems that support
|
|
// IPv6, but not IPv6 policy routing.
|
|
out, err := exec.Command("ip", add...).CombinedOutput()
|
|
if err != nil {
|
|
out = bytes.TrimSpace(out)
|
|
var detail interface{} = out
|
|
if len(out) == 0 {
|
|
detail = err.Error()
|
|
}
|
|
return fmt.Errorf("ip -6 rule failed: %s", detail)
|
|
}
|
|
|
|
// Delete again.
|
|
exec.Command("ip", del...).Run()
|
|
return nil
|
|
}
|