wgengine: quiet some engine reconfig logging, make more consistent

Updates #282

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

ipn/local.go

@@ -610,6 +610,8 @@ func (b *LocalBackend) SetPrefs(new *Prefs) {
 	cli := b.c
 	b.mu.Unlock()
 
+	b.logf("SetPrefs: %v\n", new.Pretty())
+
 	if cli != nil && !oldHi.Equal(newHi) {
 		cli.SetHostinfo(newHi)
 	}
@@ -620,7 +622,6 @@ func (b *LocalBackend) SetPrefs(new *Prefs) {
 		b.authReconfig()
 	}
 
-	b.logf("SetPrefs: %v\n", new.Pretty())
 	b.send(Notify{Prefs: new})
 }
 
@@ -657,7 +658,6 @@ func (b *LocalBackend) authReconfig() {
 		b.logf("authReconfig: skipping because !WantRunning.\n")
 		return
 	}
-	b.logf("Configuring wireguard connection.\n")
 
 	uflags := controlclient.UDefault
 	if uc.RouteAll {
@@ -674,7 +674,6 @@ func (b *LocalBackend) authReconfig() {
 	if uc.AllowSingleHosts {
 		uflags |= controlclient.UAllowSingleHosts
 	}
-	b.logf("reconfig: ra=%v dns=%v 0x%02x\n", uc.RouteAll, uc.CorpDNS, uflags)
 
 	dns := nm.DNS
 	dom := nm.DNSDomains
@@ -688,9 +687,10 @@ func (b *LocalBackend) authReconfig() {
 	}
 
 	err = b.e.Reconfig(cfg, dom)
-	if err != nil {
+	if err == wgengine.ErrNoChanges {
-		b.logf("reconfig: %v", err)
+		return
 	}
+	b.logf("authReconfig: ra=%v dns=%v 0x%02x: %v\n", uc.RouteAll, uc.CorpDNS, uflags, err)
 }
 
 func (b *LocalBackend) enterState(newState State) {

wgengine/userspace.go

@@ -311,7 +311,6 @@ func (e *userspaceEngine) pinger(peerKey wgcfg.Key, ips []wgcfg.IP) {
 // the traditional wireguard config format. On the other hand, wireguard
 // itself doesn't use the traditional 'dns =' setting either.
 func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, dnsDomains []string) error {
-	e.logf("Reconfig(): configuring userspace wireguard engine.\n")
 	e.wgLock.Lock()
 	defer e.wgLock.Unlock()
 
@@ -330,9 +329,10 @@ func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, dnsDomains []string) error
 
 	rc := uapi + "\x00" + strings.Join(dnsDomains, "\x00")
 	if rc == e.lastReconfig {
-		e.logf("...unchanged config, skipping.\n")
+		return ErrNoChanges
-		return nil
 	}
+
+	e.logf("wgengine: Reconfig: configuring userspace wireguard engine")
 	e.lastReconfig = rc
 	e.lastCfg = cfg.Copy()
 
@@ -374,7 +374,7 @@ func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, dnsDomains []string) error
 	// just what's absolutely needed (the set of actual routes).
 	rss := rs.OnlyRelevantParts()
 	if rss != e.lastRoutes {
-		e.logf("Reconfiguring router. la=%v dns=%v dom=%v; new routes: %v\n",
+		e.logf("wgengine: Reconfig: reconfiguring router. la=%v dns=%v dom=%v; new routes: %v",
 			rs.LocalAddr, rs.DNS, rs.DNSDomains, rss)
 		e.lastRoutes = rss
 		err = e.router.SetRoutes(rs)
@@ -383,7 +383,7 @@ func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, dnsDomains []string) error
 		}
 	}
 
-	e.logf("Reconfig() done.\n")
+	e.logf("wgengine: Reconfig done")
 	return nil
 }
 

wgengine/wgengine.go

@@ -5,6 +5,7 @@
 package wgengine
 
 import (
+	"errors"
 	"fmt"
 	"time"
 
@@ -92,6 +93,9 @@ type Router interface {
 	Close() error
 }
 
+// ErrNoChanges is returned by Engine.Reconfig if no changes were made.
+var ErrNoChanges = errors.New("no changes made to Engine config")
+
 // Engine is the Tailscale WireGuard engine interface.
 type Engine interface {
 	// Reconfig reconfigures WireGuard and makes sure it's running.
@@ -102,6 +106,8 @@ type Engine interface {
 	//
 	// This is called whenever the tailcontrol (control plane)
 	// sends an updated network map.
+	//
+	// The returned error is ErrNoChanges if no changes were made.
 	Reconfig(cfg *wgcfg.Config, dnsDomains []string) error
 
 	// GetFilter returns the current packet filter, if any.