Revert "ipnlocal, magicsock: store last suggested exit node id in loc…

…al backend (#11959)"

This reverts commit 35872e8.

ipn/ipnlocal/local.go

@@ -151,12 +151,6 @@ type watchSession struct {
 	sessionID string
 }
 
-// lastSuggestedExitNode stores the last suggested exit node ID and name in local backend.
-type lastSuggestedExitNode struct {
-	id   tailcfg.StableNodeID
-	name string
-}
-
 // LocalBackend is the glue between the major pieces of the Tailscale
 // network software: the cloud control plane (via controlclient), the
 // network data plane (via wgengine), and the user-facing UIs and CLIs
@@ -330,10 +324,6 @@ type LocalBackend struct {
 
 	// outgoingFiles keeps track of Taildrop outgoing files keyed to their OutgoingFile.ID
 	outgoingFiles map[string]*ipn.OutgoingFile
-
-	// lastSuggestedExitNode stores the last suggested exit node ID and name.
-	// lastSuggestedExitNode updates whenever the suggestion changes.
-	lastSuggestedExitNode lastSuggestedExitNode
 }
 
 // HealthTracker returns the health tracker for the backend.
@@ -5967,8 +5957,7 @@ func (b *LocalBackend) resetForProfileChangeLockedOnEntry(unlock unlockOnce) err
 	}
 	b.lastServeConfJSON = mem.B(nil)
 	b.serveConfig = ipn.ServeConfigView{}
-	b.lastSuggestedExitNode = lastSuggestedExitNode{} // Reset last suggested exit node.
-	b.enterStateLockedOnEntry(ipn.NoState, unlock)    // Reset state; releases b.mu
+	b.enterStateLockedOnEntry(ipn.NoState, unlock) // Reset state; releases b.mu
 	b.health.SetLocalLogConfigHealth(nil)
 	return b.Start(ipn.Options{})
 }
@@ -6345,7 +6334,6 @@ func mayDeref[T any](p *T) (v T) {
 
 var ErrNoPreferredDERP = errors.New("no preferred DERP, try again later")
 var ErrCannotSuggestExitNode = errors.New("unable to suggest an exit node, try again later")
-var ErrUnableToSuggestLastExitNode = errors.New("unable to suggest last exit node")
 
 // SuggestExitNode computes a suggestion based on the current netmap and last netcheck report. If
 // there are multiple equally good options, one is selected at random, so the result is not stable. To be
@@ -6358,41 +6346,13 @@ func (b *LocalBackend) SuggestExitNode() (response apitype.ExitNodeSuggestionRes
 	b.mu.Lock()
 	lastReport := b.MagicConn().GetLastNetcheckReport(b.ctx)
 	netMap := b.netMap
-	lastSuggestedExitNode := b.lastSuggestedExitNode
 	b.mu.Unlock()
 	if lastReport == nil || netMap == nil {
-		last, err := suggestLastExitNode(lastSuggestedExitNode)
-		if err != nil {
-			return response, ErrCannotSuggestExitNode
-		}
-		return last, err
+		return response, ErrCannotSuggestExitNode
 	}
 	seed := time.Now().UnixNano()
 	r := rand.New(rand.NewSource(seed))
-	res, err := suggestExitNode(lastReport, netMap, r)
-	if err != nil {
-		last, err := suggestLastExitNode(lastSuggestedExitNode)
-		if err != nil {
-			return response, ErrCannotSuggestExitNode
-		}
-		return last, err
-	}
-	b.mu.Lock()
-	b.lastSuggestedExitNode.id = res.ID
-	b.lastSuggestedExitNode.name = res.Name
-	b.mu.Unlock()
-	return res, err
-}
-
-// suggestLastExitNode formats a response with the last suggested exit node's ID and name.
-// Used as a fallback before returning a nil response and error.
-func suggestLastExitNode(lastSuggestedExitNode lastSuggestedExitNode) (res apitype.ExitNodeSuggestionResponse, err error) {
-	if lastSuggestedExitNode.id != "" && lastSuggestedExitNode.name != "" {
-		res.ID = lastSuggestedExitNode.id
-		res.Name = lastSuggestedExitNode.name
-		return res, nil
-	}
-	return res, ErrUnableToSuggestLastExitNode
+	return suggestExitNode(lastReport, netMap, r)
 }
 
 func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, r *rand.Rand) (res apitype.ExitNodeSuggestionResponse, err error) {