change: do not echo a node's own report back to it

An endpoint or DERP report came back to the node as a self update;
SaaS sends it to the node's peers only.

hscontrol/mapper/batcher_concurrency_test.go

@@ -274,7 +274,7 @@ func TestAddToBatchDifferential(t *testing.T) {
 		lb.b.nodes.Store(99, nil)
 	}
 
-	endpoint := change.EndpointOrDERPUpdate(1, &tailcfg.PeerChange{
+	endpoint := change.EndpointOrDERPUpdate(&tailcfg.PeerChange{
 		NodeID: 1, DERPRegion: 7, Online: new(true),
 	})
 	ping := change.PingNode(2, &tailcfg.PingRequest{URL: "https://example.com/one"})

hscontrol/servertest/mapstream_compat_test.go

@@ -59,10 +59,6 @@ var mapStreamSkipReasons = map[string]string{
 	"map-delivery/S3.5-remove/db1/frames":  policyResponseToEveryNode,
 	"map-delivery/S3.5-restore/db1/frames": policyResponseToEveryNode,
 
-	"map-delivery/S2.1/laptop/frames":         ownReportEchoed,
-	"map-delivery/S2.3/laptop/frames":         ownReportEchoed,
-	"map-delivery/S2.5/laptop/self-endpoints": ownReportEchoed,
-
 	"map-delivery/S2.5/laptop/endpoints-gap-bystander": restartEndpointsKept,
 	"map-delivery/S2.5/laptop/endpoints-gap-svc":       restartEndpointsKept,
 
@@ -121,7 +117,6 @@ var mapStreamSkipReasons = map[string]string{
 
 const (
 	policyResponseToEveryNode = "POLICY_RESPONSE_TO_EVERY_NODE: headscale sends every connected node a policy response when the policy, a node's tags or approved routes, or the set of nodes change; SaaS sends only the nodes whose peers or filter change"
-	ownReportEchoed           = "OWN_REPORT_ECHOED: headscale sends a node its own endpoint or DERP report back; SaaS sends it nothing, so its own entry keeps the endpoints of its last full map"
 	restartEndpointsKept      = "RESTART_ENDPOINTS_KEPT: headscale keeps a restarted node's last endpoints at its peers until it reports new ones; SaaS sends peers the node without endpoints until then"
 	reconnectAnnounced        = "RECONNECT_ANNOUNCED: headscale tells peers a node is online after a stream gap of a few seconds; SaaS sends them nothing"
 	routerReconnectRecompute  = "ROUTER_RECONNECT_RECOMPUTE: headscale sends every node a policy response when a subnet router's stream comes back after a few seconds; SaaS sends nothing"

hscontrol/state/state.go

@@ -4207,7 +4207,7 @@ func buildMapRequestChangeResponse(
 			patch.DERPRegion = currentDERP
 		}
 
-		return change.EndpointOrDERPUpdate(id, patch)
+		return change.EndpointOrDERPUpdate(patch)
 	}
 
 	return change.Change{}

hscontrol/types/change/change.go

@@ -595,13 +595,12 @@ func KeyExpiryFor(id types.NodeID, expiry time.Time) Change {
 	return c
 }
 
-// EndpointOrDERPUpdate returns a [Change] for when a node's endpoints or DERP region changes.
-// The [Change.OriginNode] field enables self-update detection by the mapper.
-func EndpointOrDERPUpdate(id types.NodeID, patch *tailcfg.PeerChange) Change {
-	c := PeerPatched("endpoint/DERP update", patch)
-	c.OriginNode = id
-
-	return c
+// EndpointOrDERPUpdate returns a [Change] for when a node reports new
+// endpoints or a new DERP region. It has no [Change.OriginNode]: the node
+// already knows what it reported, so, as on Tailscale SaaS, only its peers
+// are sent the patch.
+func EndpointOrDERPUpdate(patch *tailcfg.PeerChange) Change {
+	return PeerPatched("endpoint/DERP update", patch)
 }
 
 // NodeKeyRotated returns a [Change] for a node re-logging in: its NodeKey (and