net/dns, feature/featuretags: make NetworkManager, systemd-resolved, and DBus modular

Saves 360 KB (19951800 => 19591352 on linux/amd64 --extra-small --box binary)

Updates #12614
Updates #17206

Change-Id: Iafd5b2536dd735111b447546cba335a7a64379ed
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscaled/deps_test.go

@@ -161,3 +161,16 @@ func TestOmitOutboundProxy(t *testing.T) {
 		},
 	}.Check(t)
 }
+
+func TestOmitDBus(t *testing.T) {
+	deptest.DepChecker{
+		GOOS:   "linux",
+		GOARCH: "amd64",
+		Tags:   "ts_omit_networkmanager,ts_omit_dbus,ts_omit_resolved,ts_omit_systray,ts_omit_ssh,ts_include_cli",
+		OnDep: func(dep string) {
+			if strings.Contains(dep, "dbus") {
+				t.Errorf("unexpected DBus dep: %q", dep)
+			}
+		},
+	}.Check(t)
+}

feature/buildfeatures/feature_dbus_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build ts_omit_dbus
+
+package buildfeatures
+
+// HasDBus is whether the binary was built with support for modular feature "Linux DBus support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_dbus" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasDBus = false

feature/buildfeatures/feature_dbus_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build !ts_omit_dbus
+
+package buildfeatures
+
+// HasDBus is whether the binary was built with support for modular feature "Linux DBus support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_dbus" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasDBus = true

feature/buildfeatures/feature_networkmanager_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build ts_omit_networkmanager
+
+package buildfeatures
+
+// HasNetworkManager is whether the binary was built with support for modular feature "Linux NetworkManager integration".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_networkmanager" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasNetworkManager = false

feature/buildfeatures/feature_networkmanager_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build !ts_omit_networkmanager
+
+package buildfeatures
+
+// HasNetworkManager is whether the binary was built with support for modular feature "Linux NetworkManager integration".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_networkmanager" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasNetworkManager = true

feature/buildfeatures/feature_resolved_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build ts_omit_resolved
+
+package buildfeatures
+
+// HasResolved is whether the binary was built with support for modular feature "Linux systemd-resolved integration".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_resolved" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasResolved = false

feature/buildfeatures/feature_resolved_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build !ts_omit_resolved
+
+package buildfeatures
+
+// HasResolved is whether the binary was built with support for modular feature "Linux systemd-resolved integration".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_resolved" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasResolved = true

feature/featuretags/featuretags.go

@@ -97,6 +97,7 @@ var Features = map[FeatureTag]FeatureMeta{
 	"capture":       {"Capture", "Packet capture", nil},
 	"cli":           {"CLI", "embed the CLI into the tailscaled binary", nil},
 	"completion":    {"Completion", "CLI shell completion", nil},
+	"dbus":          {"DBus", "Linux DBus support", nil},
 	"debugeventbus": {"DebugEventBus", "eventbus debug support", nil},
 	"debugportmapper": {
 		Sym:  "DebugPortMapper",
@@ -115,7 +116,17 @@ var Features = map[FeatureTag]FeatureMeta{
 	},
 	"portmapper": {"PortMapper", "NAT-PMP/PCP/UPnP port mapping support", nil},
 	"netstack":   {"Netstack", "gVisor netstack (userspace networking) support (TODO; not yet omittable)", nil},
+	"networkmanager": {
+		Sym:  "NetworkManager",
+		Desc: "Linux NetworkManager integration",
+		Deps: []FeatureTag{"dbus"},
+	},
 	"relayserver": {"RelayServer", "Relay server", nil},
+	"resolved": {
+		Sym:  "Resolved",
+		Desc: "Linux systemd-resolved integration",
+		Deps: []FeatureTag{"dbus"},
+	},
 	"serve": {
 		Sym:  "Serve",
 		Desc: "Serve and Funnel support",
@@ -124,10 +135,14 @@ var Features = map[FeatureTag]FeatureMeta{
 	"ssh": {
 		Sym:  "SSH",
 		Desc: "Tailscale SSH support",
-		Deps: []FeatureTag{"netstack"},
+		Deps: []FeatureTag{"dbus", "netstack"},
 	},
 	"syspolicy": {"SystemPolicy", "System policy configuration (MDM) support", nil},
-	"systray":     {"SysTray", "Linux system tray", nil},
+	"systray": {
+		Sym:  "SysTray",
+		Desc: "Linux system tray",
+		Deps: []FeatureTag{"dbus"},
+	},
 	"taildrop":    {"Taildrop", "Taildrop (file sending) support", nil},
 	"tailnetlock": {"TailnetLock", "Tailnet Lock support", nil},
 	"tap":         {"Tap", "Experimental Layer 2 (ethernet) support", nil},

net/dns/dbus.go

@@ -0,0 +1,59 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux && !android && !ts_omit_dbus
+
+package dns
+
+import (
+	"context"
+	"time"
+
+	"github.com/godbus/dbus/v5"
+)
+
+func init() {
+	optDBusPing.Set(dbusPing)
+	optDBusReadString.Set(dbusReadString)
+}
+
+func dbusPing(name, objectPath string) error {
+	conn, err := dbus.SystemBus()
+	if err != nil {
+		// DBus probably not running.
+		return err
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	obj := conn.Object(name, dbus.ObjectPath(objectPath))
+	call := obj.CallWithContext(ctx, "org.freedesktop.DBus.Peer.Ping", 0)
+	return call.Err
+}
+
+// dbusReadString reads a string property from the provided name and object
+// path. property must be in "interface.member" notation.
+func dbusReadString(name, objectPath, iface, member string) (string, error) {
+	conn, err := dbus.SystemBus()
+	if err != nil {
+		// DBus probably not running.
+		return "", err
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	obj := conn.Object(name, dbus.ObjectPath(objectPath))
+
+	var result dbus.Variant
+	err = obj.CallWithContext(ctx, "org.freedesktop.DBus.Properties.Get", 0, iface, member).Store(&result)
+	if err != nil {
+		return "", err
+	}
+
+	if s, ok := result.Value().(string); ok {
+		return s, nil
+	}
+	return result.String(), nil
+}

net/dns/manager_linux.go

@@ -7,7 +7,6 @@ package dns
 
 import (
 	"bytes"
-	"context"
 	"errors"
 	"fmt"
 	"os"
@@ -15,13 +14,12 @@ import (
 	"sync"
 	"time"
 
-	"github.com/godbus/dbus/v5"
 	"tailscale.com/control/controlknobs"
+	"tailscale.com/feature"
 	"tailscale.com/health"
 	"tailscale.com/net/netaddr"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/clientmetric"
-	"tailscale.com/util/cmpver"
 	"tailscale.com/util/syspolicy/policyclient"
 	"tailscale.com/version/distro"
 )
@@ -36,6 +34,31 @@ func (kv kv) String() string {
 
 var publishOnce sync.Once
 
+// reconfigTimeout is the time interval within which Manager.{Up,Down} should complete.
+//
+// This is particularly useful because certain conditions can cause indefinite hangs
+// (such as improper dbus auth followed by contextless dbus.Object.Call).
+// Such operations should be wrapped in a timeout context.
+const reconfigTimeout = time.Second
+
+// Set unless ts_omit_networkmanager
+var (
+	optNewNMManager      feature.Hook[func(ifName string) (OSConfigurator, error)]
+	optNMIsUsingResolved feature.Hook[func() error]
+	optNMVersionBetween  feature.Hook[func(v1, v2 string) (bool, error)]
+)
+
+// Set unless ts_omit_resolved
+var (
+	optNewResolvedManager feature.Hook[func(logf logger.Logf, health *health.Tracker, interfaceName string) (OSConfigurator, error)]
+)
+
+// Set unless ts_omit_dbus
+var (
+	optDBusPing       feature.Hook[func(name, objectPath string) error]
+	optDBusReadString feature.Hook[func(name, objectPath, iface, member string) (string, error)]
+)
+
 // NewOSConfigurator created a new OS configurator.
 //
 // The health tracker may be nil; the knobs may be nil and are ignored on this platform.
@@ -46,12 +69,24 @@ func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ policyclient.
 
 	env := newOSConfigEnv{
 		fs:              directFS{},
-		dbusPing:          dbusPing,
-		dbusReadString:    dbusReadString,
-		nmIsUsingResolved: nmIsUsingResolved,
-		nmVersionBetween:  nmVersionBetween,
 		resolvconfStyle: resolvconfStyle,
 	}
+	if f, ok := optDBusPing.GetOk(); ok {
+		env.dbusPing = f
+	} else {
+		env.dbusPing = func(_, _ string) error { return errors.ErrUnsupported }
+	}
+	if f, ok := optDBusReadString.GetOk(); ok {
+		env.dbusReadString = f
+	} else {
+		env.dbusReadString = func(_, _, _, _ string) (string, error) { return "", errors.ErrUnsupported }
+	}
+	if f, ok := optNMIsUsingResolved.GetOk(); ok {
+		env.nmIsUsingResolved = f
+	} else {
+		env.nmIsUsingResolved = func() error { return errors.ErrUnsupported }
+	}
+	env.nmVersionBetween, _ = optNMVersionBetween.GetOk() // GetOk to not panic if nil; unused if optNMIsUsingResolved returns an error
 	mode, err := dnsMode(logf, health, env)
 	if err != nil {
 		return nil, err
@@ -66,17 +101,24 @@ func NewOSConfigurator(logf logger.Logf, health *health.Tracker, _ policyclient.
 	case "direct":
 		return newDirectManagerOnFS(logf, health, env.fs), nil
 	case "systemd-resolved":
-		return newResolvedManager(logf, health, interfaceName)
+		if f, ok := optNewResolvedManager.GetOk(); ok {
+			return f(logf, health, interfaceName)
+		}
+		return nil, fmt.Errorf("tailscaled was built without DNS %q support", mode)
 	case "network-manager":
-		return newNMManager(interfaceName)
+		if f, ok := optNewNMManager.GetOk(); ok {
+			return f(interfaceName)
+		}
+		return nil, fmt.Errorf("tailscaled was built without DNS %q support", mode)
 	case "debian-resolvconf":
 		return newDebianResolvconfManager(logf)
 	case "openresolv":
 		return newOpenresolvManager(logf)
 	default:
 		logf("[unexpected] detected unknown DNS mode %q, using direct manager as last resort", mode)
-		return newDirectManagerOnFS(logf, health, env.fs), nil
 	}
+
+	return newDirectManagerOnFS(logf, health, env.fs), nil
 }
 
 // newOSConfigEnv are the funcs newOSConfigurator needs, pulled out for testing.
@@ -292,50 +334,6 @@ func dnsMode(logf logger.Logf, health *health.Tracker, env newOSConfigEnv) (ret
 	}
 }
 
-func nmVersionBetween(first, last string) (bool, error) {
-	conn, err := dbus.SystemBus()
-	if err != nil {
-		// DBus probably not running.
-		return false, err
-	}
-
-	nm := conn.Object("org.freedesktop.NetworkManager", dbus.ObjectPath("/org/freedesktop/NetworkManager"))
-	v, err := nm.GetProperty("org.freedesktop.NetworkManager.Version")
-	if err != nil {
-		return false, err
-	}
-
-	version, ok := v.Value().(string)
-	if !ok {
-		return false, fmt.Errorf("unexpected type %T for NM version", v.Value())
-	}
-
-	outside := cmpver.Compare(version, first) < 0 || cmpver.Compare(version, last) > 0
-	return !outside, nil
-}
-
-func nmIsUsingResolved() error {
-	conn, err := dbus.SystemBus()
-	if err != nil {
-		// DBus probably not running.
-		return err
-	}
-
-	nm := conn.Object("org.freedesktop.NetworkManager", dbus.ObjectPath("/org/freedesktop/NetworkManager/DnsManager"))
-	v, err := nm.GetProperty("org.freedesktop.NetworkManager.DnsManager.Mode")
-	if err != nil {
-		return fmt.Errorf("getting NM mode: %w", err)
-	}
-	mode, ok := v.Value().(string)
-	if !ok {
-		return fmt.Errorf("unexpected type %T for NM DNS mode", v.Value())
-	}
-	if mode != "systemd-resolved" {
-		return errors.New("NetworkManager is not using systemd-resolved for DNS")
-	}
-	return nil
-}
-
 // resolvedIsActuallyResolver reports whether the system is using
 // systemd-resolved as the resolver. There are two different ways to
 // use systemd-resolved:
@@ -396,44 +394,3 @@ func isLibnssResolveUsed(env newOSConfigEnv) error {
 	}
 	return fmt.Errorf("libnss_resolve not used")
 }
-
-func dbusPing(name, objectPath string) error {
-	conn, err := dbus.SystemBus()
-	if err != nil {
-		// DBus probably not running.
-		return err
-	}
-
-	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
-	defer cancel()
-
-	obj := conn.Object(name, dbus.ObjectPath(objectPath))
-	call := obj.CallWithContext(ctx, "org.freedesktop.DBus.Peer.Ping", 0)
-	return call.Err
-}
-
-// dbusReadString reads a string property from the provided name and object
-// path. property must be in "interface.member" notation.
-func dbusReadString(name, objectPath, iface, member string) (string, error) {
-	conn, err := dbus.SystemBus()
-	if err != nil {
-		// DBus probably not running.
-		return "", err
-	}
-
-	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
-	defer cancel()
-
-	obj := conn.Object(name, dbus.ObjectPath(objectPath))
-
-	var result dbus.Variant
-	err = obj.CallWithContext(ctx, "org.freedesktop.DBus.Properties.Get", 0, iface, member).Store(&result)
-	if err != nil {
-		return "", err
-	}
-
-	if s, ok := result.Value().(string); ok {
-		return s, nil
-	}
-	return result.String(), nil
-}

net/dns/nm.go

@@ -1,13 +1,14 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux && !android
+//go:build linux && !android && !ts_omit_networkmanager
 
 package dns
 
 import (
 	"context"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"net"
 	"net/netip"
@@ -16,6 +17,7 @@ import (
 
 	"github.com/godbus/dbus/v5"
 	"tailscale.com/net/tsaddr"
+	"tailscale.com/util/cmpver"
 	"tailscale.com/util/dnsname"
 )
 
@@ -25,13 +27,6 @@ const (
 	lowerPriority   = int32(200) // lower than all builtin auto priorities
 )
 
-// reconfigTimeout is the time interval within which Manager.{Up,Down} should complete.
-//
-// This is particularly useful because certain conditions can cause indefinite hangs
-// (such as improper dbus auth followed by contextless dbus.Object.Call).
-// Such operations should be wrapped in a timeout context.
-const reconfigTimeout = time.Second
-
 // nmManager uses the NetworkManager DBus API.
 type nmManager struct {
 	interfaceName string
@@ -39,7 +34,13 @@ type nmManager struct {
 	dnsManager    dbus.BusObject
 }
 
-func newNMManager(interfaceName string) (*nmManager, error) {
+func init() {
+	optNewNMManager.Set(newNMManager)
+	optNMIsUsingResolved.Set(nmIsUsingResolved)
+	optNMVersionBetween.Set(nmVersionBetween)
+}
+
+func newNMManager(interfaceName string) (OSConfigurator, error) {
 	conn, err := dbus.SystemBus()
 	if err != nil {
 		return nil, err
@@ -389,3 +390,47 @@ func (m *nmManager) Close() error {
 	// settings when the tailscale interface goes away.
 	return nil
 }
+
+func nmVersionBetween(first, last string) (bool, error) {
+	conn, err := dbus.SystemBus()
+	if err != nil {
+		// DBus probably not running.
+		return false, err
+	}
+
+	nm := conn.Object("org.freedesktop.NetworkManager", dbus.ObjectPath("/org/freedesktop/NetworkManager"))
+	v, err := nm.GetProperty("org.freedesktop.NetworkManager.Version")
+	if err != nil {
+		return false, err
+	}
+
+	version, ok := v.Value().(string)
+	if !ok {
+		return false, fmt.Errorf("unexpected type %T for NM version", v.Value())
+	}
+
+	outside := cmpver.Compare(version, first) < 0 || cmpver.Compare(version, last) > 0
+	return !outside, nil
+}
+
+func nmIsUsingResolved() error {
+	conn, err := dbus.SystemBus()
+	if err != nil {
+		// DBus probably not running.
+		return err
+	}
+
+	nm := conn.Object("org.freedesktop.NetworkManager", dbus.ObjectPath("/org/freedesktop/NetworkManager/DnsManager"))
+	v, err := nm.GetProperty("org.freedesktop.NetworkManager.DnsManager.Mode")
+	if err != nil {
+		return fmt.Errorf("getting NM mode: %w", err)
+	}
+	mode, ok := v.Value().(string)
+	if !ok {
+		return fmt.Errorf("unexpected type %T for NM DNS mode", v.Value())
+	}
+	if mode != "systemd-resolved" {
+		return errors.New("NetworkManager is not using systemd-resolved for DNS")
+	}
+	return nil
+}

net/dns/resolved.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux && !android
+//go:build linux && !android && !ts_omit_resolved
 
 package dns
 
@@ -70,7 +70,11 @@ type resolvedManager struct {
 	configCR chan changeRequest // tracks OSConfigs changes and error responses
 }
 
-func newResolvedManager(logf logger.Logf, health *health.Tracker, interfaceName string) (*resolvedManager, error) {
+func init() {
+	optNewResolvedManager.Set(newResolvedManager)
+}
+
+func newResolvedManager(logf logger.Logf, health *health.Tracker, interfaceName string) (OSConfigurator, error) {
 	iface, err := net.InterfaceByName(interfaceName)
 	if err != nil {
 		return nil, err