control/controlclient: don't clone self node on each NetworkMap

Drop in the bucket, but have to start somewhere.

Real wins will come once this is done for peers.

                                 │     before     │                after                │
                                 │      B/op      │     B/op       vs base              │
    MapSessionDelta/size_10-8      10.213Ki ± ∞ ¹   9.650Ki ± ∞ ¹  -5.51% (p=0.008 n=5)
    MapSessionDelta/size_100-8      83.64Ki ± ∞ ¹   83.08Ki ± ∞ ¹  -0.67% (p=0.008 n=5)
    MapSessionDelta/size_1000-8     800.8Ki ± ∞ ¹   800.3Ki ± ∞ ¹  -0.07% (p=0.008 n=5)
    MapSessionDelta/size_10000-8    7.712Mi ± ∞ ¹   7.711Mi ± ∞ ¹  -0.01% (p=0.008 n=5)
    geomean                         271.1Ki         266.8Ki        -1.59%

                                 │    before    │               after                │
                                 │  allocs/op   │  allocs/op    vs base              │
    MapSessionDelta/size_10-8       73.00 ± ∞ ¹    72.00 ± ∞ ¹  -1.37% (p=0.008 n=5)
    MapSessionDelta/size_100-8      524.0 ± ∞ ¹    523.0 ± ∞ ¹  -0.19% (p=0.008 n=5)
    MapSessionDelta/size_1000-8    5.025k ± ∞ ¹   5.024k ± ∞ ¹  -0.02% (p=0.008 n=5)
    MapSessionDelta/size_10000-8   50.02k ± ∞ ¹   50.02k ± ∞ ¹  -0.00% (p=0.040 n=5)
    geomean                        1.761k         1.754k        -0.40%

Updates #1909

Change-Id: Ie19dea3371de251d64d4373dd00422f53c2675ea
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/map.go

@@ -62,7 +62,7 @@ type mapSession struct {
 	onSelfNodeChanged func(*netmap.NetworkMap)
 
 	// Fields storing state over the course of multiple MapResponses.
-	lastNode               *tailcfg.Node
+	lastNode               tailcfg.NodeView
 	lastDNSConfig          *tailcfg.DNSConfig
 	lastDERPMap            *tailcfg.DERPMap
 	lastUserProfile        map[tailcfg.UserID]tailcfg.UserProfile
@@ -182,7 +182,7 @@ func (ms *mapSession) HandleNonKeepAliveMapResponse(ctx context.Context, resp *t
 	}
 
 	// Call Node.InitDisplayNames on any changed nodes.
-	initDisplayNames(cmpx.Or(resp.Node, ms.lastNode).View(), resp)
+	initDisplayNames(cmpx.Or(resp.Node.View(), ms.lastNode), resp)
 
 	nm := ms.netmapForResponse(resp)
 
@@ -312,17 +312,17 @@ func (ms *mapSession) netmapForResponse(resp *tailcfg.MapResponse) *netmap.Netwo
 	}
 
 	if resp.Node != nil {
-		ms.lastNode = resp.Node
+		ms.lastNode = resp.Node.View()
-	}
+	}
-	if node := ms.lastNode.Clone(); node != nil {
+	if node := ms.lastNode; node.Valid() {
-		nm.SelfNode = node.View()
+		nm.SelfNode = node
-		nm.Expiry = node.KeyExpiry
+		nm.Expiry = node.KeyExpiry()
-		nm.Name = node.Name
+		nm.Name = node.Name()
-		nm.Addresses = filterSelfAddresses(node.Addresses)
+		nm.Addresses = filterSelfAddresses(node.Addresses().AsSlice())
-		if node.Hostinfo.Valid() {
+		if node.Hostinfo().Valid() {
-			nm.Hostinfo = *node.Hostinfo.AsStruct()
+			nm.Hostinfo = *node.Hostinfo().AsStruct()
 		}
-		if node.MachineAuthorized {
+		if node.MachineAuthorized() {
 			nm.MachineStatus = tailcfg.MachineAuthorized
 		} else {
 			nm.MachineStatus = tailcfg.MachineUnauthorized