net/netmon, add: add netmon.State type alias of interfaces.State

... in prep for merging the net/interfaces package into net/netmon.

This is a no-op change that updates a bunch of the API signatures ahead of
a future change to actually move things (and remove the type alias)

Updates tailscale/corp#10910
Updates tailscale/corp#18960
Updates #7967
Updates #3299

Change-Id: I477613388f09389214db0d77ccf24a65bff2199c
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

net/netcheck/netcheck.go

@@ -27,7 +27,6 @@ import (
 	"tailscale.com/derp/derphttp"
 	"tailscale.com/envknob"
 	"tailscale.com/net/dnscache"
-	"tailscale.com/net/interfaces"
 	"tailscale.com/net/neterror"
 	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
@@ -389,7 +388,7 @@ const numIncrementalRegions = 3
 
 // makeProbePlan generates the probe plan for a DERPMap, given the most
 // recent report and whether IPv6 is configured on an interface.
-func makeProbePlan(dm *tailcfg.DERPMap, ifState *interfaces.State, last *Report) (plan probePlan) {
+func makeProbePlan(dm *tailcfg.DERPMap, ifState *State, last *Report) (plan probePlan) {
 	if last == nil || len(last.RegionLatency) == 0 {
 		return makeProbePlanInitial(dm, ifState)
 	}
@@ -469,7 +468,7 @@ func makeProbePlan(dm *tailcfg.DERPMap, ifState *interfaces.State, last *Report)
 	return plan
 }
 
-func makeProbePlanInitial(dm *tailcfg.DERPMap, ifState *interfaces.State) (plan probePlan) {
+func makeProbePlanInitial(dm *tailcfg.DERPMap, ifState *netmon.State) (plan probePlan) {
 	plan = make(probePlan)
 
 	for _, reg := range dm.Regions {

net/netcheck/netcheck_test.go

@@ -18,7 +18,6 @@ import (
 	"testing"
 	"time"
 
-	"tailscale.com/net/interfaces"
 	"tailscale.com/net/netmon"
 	"tailscale.com/net/stun"
 	"tailscale.com/net/stun/stuntest"
@@ -673,7 +672,7 @@ func TestMakeProbePlan(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			ifState := &interfaces.State{
+			ifState := &netmon.State{
 				HaveV6: tt.have6if,
 				HaveV4: !tt.no4,
 			}

net/netmon/netmon.go

@@ -64,7 +64,7 @@ type Monitor struct {
 	mu         sync.Mutex // guards all following fields
 	cbs        set.HandleSet[ChangeFunc]
 	ruleDelCB  set.HandleSet[RuleDeleteCallback]
-	ifState    *interfaces.State
+	ifState    *State
 	gwValid    bool       // whether gw and gwSelfIP are valid
 	gw         netip.Addr // our gateway's IP
 	gwSelfIP   netip.Addr // our own IP address (that corresponds to gw)
@@ -88,12 +88,12 @@ type ChangeDelta struct {
 	// Old is the old interface state, if known.
 	// It's nil if the old state is unknown.
 	// Do not mutate it.
-	Old *interfaces.State
+	Old *State
 
 	// New is the new network state.
 	// It is always non-nil.
 	// Do not mutate it.
-	New *interfaces.State
+	New *State
 
 	// Major is our legacy boolean of whether the network changed in some major
 	// way.
@@ -155,13 +155,13 @@ func NewStatic() *Monitor {
 // interfaces.
 //
 // The returned value is owned by Mon; it must not be modified.
-func (m *Monitor) InterfaceState() *interfaces.State {
+func (m *Monitor) InterfaceState() *State {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	return m.ifState
 }
 
-func (m *Monitor) interfaceStateUncached() (*interfaces.State, error) {
+func (m *Monitor) interfaceStateUncached() (*State, error) {
 	return interfaces.GetState()
 }
 
@@ -421,7 +421,7 @@ var (
 // up callers and updates the monitor's state if so.
 //
 // If forceCallbacks is true, they're always notified.
-func (m *Monitor) handlePotentialChange(newState *interfaces.State, forceCallbacks bool) {
+func (m *Monitor) handlePotentialChange(newState *State, forceCallbacks bool) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	oldState := m.ifState
@@ -476,7 +476,7 @@ func (m *Monitor) handlePotentialChange(newState *interfaces.State, forceCallbac
 // a bunch of connections and rebinding.
 //
 // TODO(bradiftz): tigten this definition.
-func (m *Monitor) IsMajorChangeFrom(s1, s2 *interfaces.State) bool {
+func (m *Monitor) IsMajorChangeFrom(s1, s2 *State) bool {
 	if s1 == nil && s2 == nil {
 		return false
 	}

net/netmon/state.go

@@ -0,0 +1,8 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package netmon
+
+import "tailscale.com/net/interfaces"
+
+type State = interfaces.State // temporary (2024-04-27) alias during multi-step removal of net/interfaces

net/netutil/ip_forward.go

@@ -16,13 +16,13 @@ import (
 	"strconv"
 	"strings"
 
-	"tailscale.com/net/interfaces"
+	"tailscale.com/net/netmon"
 )
 
 // protocolsRequiredForForwarding reports whether IPv4 and/or IPv6 protocols are
 // required to forward the specified routes.
 // The state param must be specified.
-func protocolsRequiredForForwarding(routes []netip.Prefix, state *interfaces.State) (v4, v6 bool) {
+func protocolsRequiredForForwarding(routes []netip.Prefix, state *netmon.State) (v4, v6 bool) {
 	if len(routes) == 0 {
 		// Nothing to route, so no need to warn.
 		return false, false
@@ -59,7 +59,7 @@ func protocolsRequiredForForwarding(routes []netip.Prefix, state *interfaces.Sta
 // It returns an error if it is unable to determine if IP forwarding is enabled.
 // It returns a warning describing configuration issues if IP forwarding is
 // non-functional or partly functional.
-func CheckIPForwarding(routes []netip.Prefix, state *interfaces.State) (warn, err error) {
+func CheckIPForwarding(routes []netip.Prefix, state *netmon.State) (warn, err error) {
 	if runtime.GOOS != "linux" {
 		switch runtime.GOOS {
 		case "dragonfly", "freebsd", "netbsd", "openbsd":
@@ -152,7 +152,7 @@ func CheckIPForwarding(routes []netip.Prefix, state *interfaces.State) (warn, er
 // This function returns an error if it is unable to determine whether reverse
 // path filtering is enabled, or a warning describing configuration issues if
 // reverse path fitering is non-functional or partly functional.
-func CheckReversePathFiltering(state *interfaces.State) (warn []string, err error) {
+func CheckReversePathFiltering(state *netmon.State) (warn []string, err error) {
 	if runtime.GOOS != "linux" {
 		return nil, nil
 	}