control/controlclient: support delta userprofiles from control

I was going to make support for this advertised from the client, but
turns out only "tailscale status" even uses the UserProfiles field and
fails gracefully (omits that field) if a user profile for a user is
missing, so I think we can just reuse the DeltaPeers field from the
client to ask the control server to also delta encode the user
profiles.

For the few users running 1.1.x (unstable) versions between DeltaPeers
support (1.1.82) and this (~1.1.541), they'll just sometimes have
missing names in "tailscale status --json" or "tailscale status --web"
(the only places the UserProfile is used).

control/controlclient/direct.go

@@ -616,6 +616,7 @@ func (c *Direct) PollNetMap(ctx context.Context, maxPolls int, cb func(*NetworkM
 	}()
 
 	var lastDERPMap *tailcfg.DERPMap
+	var lastUserProfile = map[tailcfg.UserID]tailcfg.UserProfile{}
 
 	// If allowStream, then the server will use an HTTP long poll to
 	// return incremental results. There is always one response right
@@ -665,6 +666,9 @@ func (c *Direct) PollNetMap(ctx context.Context, maxPolls int, cb func(*NetworkM
 
 		undeltaPeers(&resp, previousPeers)
 		previousPeers = cloneNodes(resp.Peers) // defensive/lazy clone, since this escapes to who knows where
+		for _, up := range resp.UserProfiles {
+			lastUserProfile[up.ID] = up
+		}
 
 		if resp.DERPMap != nil {
 			vlogf("netmap: new map contains DERP map")
@@ -708,8 +712,15 @@ func (c *Direct) PollNetMap(ctx context.Context, maxPolls int, cb func(*NetworkM
 			DERPMap:      lastDERPMap,
 			Debug:        resp.Debug,
 		}
-		for _, profile := range resp.UserProfiles {
-			nm.UserProfiles[profile.ID] = profile
+		for _, peer := range resp.Peers {
+			userID := peer.User
+			if _, ok := nm.UserProfiles[userID]; ok {
+				// Already populated it from a previous peer.
+				continue
+			}
+			if up, ok := lastUserProfile[userID]; ok {
+				nm.UserProfiles[userID] = up
+			}
 		}
 		if resp.Node.MachineAuthorized {
 			nm.MachineStatus = tailcfg.MachineAuthorized

tailcfg/tailcfg.go

@@ -573,8 +573,8 @@ type MapResponse struct {
 	// ACLs
 	Domain       string
 	PacketFilter []FilterRule
-	UserProfiles []UserProfile
-	Roles        []Role // deprecated; clients should not rely on Roles
+	UserProfiles []UserProfile // as of 1.1.541: may be new or updated user profiles only
+	Roles        []Role        // deprecated; clients should not rely on Roles
 	// TODO: Groups       []Group
 	// TODO: Capabilities []Capability