wgengine/magicsock,ipn/ipnlocal: store and load homeDERP from cache (#19491)

With netmap caching, the home DERP of the self node was neither saved to the cache or loaded from it, making nodes not stick to a DERP when starting without a connection to control. Instead, make sure that when a cache is available, load that cache, before looking for DERP servers. This is implemented by allowing a skip of ReSTUN in setting the DERP map (we must have a DERP map before setting the home DERP), so the DERP from cache will set itself and be sticky until a connection to control is established. Making DERP only change when connected to control is handled by existing code from f072d017bd. Updates #19490 Signed-off-by: Claus Lensbøl <claus@tailscale.com>
2026-04-29 10:24:09 -04:00
parent 1841a93ab2
commit 78627c132f
9 changed files with 493 additions and 20 deletions
@@ -4,9 +4,15 @@
 package magicsock

 import (
+	"fmt"
 	"testing"

+	"tailscale.com/health"
 	"tailscale.com/net/netcheck"
+	"tailscale.com/tailcfg"
+	"tailscale.com/tstest"
+	"tailscale.com/util/eventbus"
+	"tailscale.com/util/eventbus/eventbustest"
 )

 func CheckDERPHeuristicTimes(t *testing.T) {
@@ -14,3 +20,111 @@ func CheckDERPHeuristicTimes(t *testing.T) {
 		t.Errorf("PreferredDERPFrameTime too low; should be at least frameReceiveRecordRate")
 	}
 }
+
+func TestForceSetNearestDERP(t *testing.T) {
+	derpMap := &tailcfg.DERPMap{
+		Regions: map[int]*tailcfg.DERPRegion{
+			7: {
+				RegionID:   7,
+				RegionCode: "test",
+				Nodes: []*tailcfg.DERPNode{
+					{
+						Name:     "7a",
+						RegionID: 7,
+						HostName: "derp7.test.unused",
+						IPv4:     "127.0.0.1",
+						IPv6:     "none",
+					},
+				},
+			},
+		},
+	}
+
+	// Force the real control health check so we can verify force=true bypasses it.
+	tstest.Replace(t, &checkControlHealthDuringNearestDERPInTests, true)
+
+	bus := eventbustest.NewBus(t)
+	ht := health.NewTracker(bus)
+	c := newConn(t.Logf)
+	ec := bus.Client("magicsock.Conn.Test")
+	c.eventClient = ec
+	c.homeDERPChangedPub = eventbus.Publish[HomeDERPChanged](ec)
+	c.eventBus = bus
+	c.derpMap = derpMap
+	c.health = ht
+
+	ht.SetOutOfPollNetMap()
+
+	tw := eventbustest.NewWatcher(t, bus)
+
+	got := c.ForceSetNearestDERP(7)
+	if got != 7 {
+		t.Fatalf("ForceSetNearestDERP(7) = %d, want 7", got)
+	}
+	if c.myDerp != 7 {
+		t.Errorf("c.myDerp = %d after ForceSetNearestDERP, want 7", c.myDerp)
+	}
+
+	if err := eventbustest.Expect(tw, func(e HomeDERPChanged) error {
+		if e.Old != 0 || e.New != 7 {
+			return fmt.Errorf("got HomeDERPChanged{Old:%d, New:%d}, want {Old:0, New:7}", e.Old, e.New)
+		}
+		return nil
+	}); err != nil {
+		t.Errorf("expected HomeDERPChanged event: %v", err)
+	}
+}
+
+func TestSetDERPMapDoReStun(t *testing.T) {
+	derpMap1 := &tailcfg.DERPMap{
+		Regions: map[int]*tailcfg.DERPRegion{
+			1: {
+				RegionID:   1,
+				RegionCode: "cph",
+				Nodes: []*tailcfg.DERPNode{
+					{Name: "1a", RegionID: 1, HostName: "cph.test.unused", IPv4: "127.0.0.1", IPv6: "none"},
+				},
+			},
+		},
+	}
+	derpMap2 := &tailcfg.DERPMap{
+		Regions: map[int]*tailcfg.DERPRegion{
+			2: {
+				RegionID:   2,
+				RegionCode: "inc",
+				Nodes: []*tailcfg.DERPNode{
+					{Name: "2a", RegionID: 2, HostName: "inc.test.unused", IPv4: "127.0.0.1", IPv6: "none"},
+				},
+			},
+		},
+	}
+
+	var reSTUNCalls int
+	tstest.Replace(t, &reSTUNHookForTests, func(_ string) {
+		reSTUNCalls++
+	})
+
+	bus := eventbustest.NewBus(t)
+	ht := health.NewTracker(bus)
+	c := newConn(t.Logf)
+	ec := bus.Client("magicsock.Conn.Test")
+	c.eventClient = ec
+	c.homeDERPChangedPub = eventbus.Publish[HomeDERPChanged](ec)
+	c.eventBus = bus
+	c.health = ht
+	// With a zero private key and everHadKey=true, ReSTUN returns early without
+	// spawning updateEndpoints.
+	c.everHadKey = true
+
+	// Should not trigger a ReSTUN.
+	c.SetDERPMap(derpMap1, false)
+	if reSTUNCalls != 0 {
+		t.Errorf("SetDERPMap(dm, doReStun=false): got %d ReSTUN calls, want 0", reSTUNCalls)
+	}
+
+	// doReStun=true: should trigger a ReSTUN.
+	c.SetDERPMap(derpMap2, true)
+	if reSTUNCalls != 1 {
+		t.Errorf("SetDERPMap(dm, doReStun=true): got %d ReSTUN calls, want 1", reSTUNCalls)
+	}
+}