tailcfg: update node display name fields and methods (#1207)

Signed-off-by: Sonia Appasamy <sonia@tailscale.com>

Consolidates the node display name logic from each of the clients into
tailcfg.Node. UI clients can use these names directly, rather than computing
them independently.

control/controlclient/direct.go

@@ -770,12 +770,12 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*Netw
 		c.mu.Unlock()
 
 		nm := &NetworkMap{
+			SelfNode:        resp.Node,
 			NodeKey:         tailcfg.NodeKey(persist.PrivateNodeKey.Public()),
 			PrivateKey:      persist.PrivateNodeKey,
 			MachineKey:      machinePubKey,
 			Expiry:          resp.Node.KeyExpiry,
 			Name:            resp.Node.Name,
-			DisplayName:     resp.Node.DisplayName,
 			Addresses:       resp.Node.Addresses,
 			Peers:           resp.Peers,
 			LocalPort:       localPort,
@@ -799,10 +799,10 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*Netw
 			}
 		}
 		addUserProfile(nm.User)
+		magicDNSSuffix := nm.MagicDNSSuffix()
+		nm.SelfNode.InitDisplayNames(magicDNSSuffix)
 		for _, peer := range resp.Peers {
-			if peer.DisplayName == "" {
-				peer.DisplayName = peer.DefaultDisplayName()
-			}
+			peer.InitDisplayNames(magicDNSSuffix)
 			if !peer.Sharer.IsZero() {
 				if c.keepSharerAndUserSplit {
 					addUserProfile(peer.Sharer)
@@ -812,9 +812,6 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*Netw
 			}
 			addUserProfile(peer.User)
 		}
-		if resp.Node.DisplayName == "" {
-			nm.DisplayName = resp.Node.DefaultDisplayName()
-		}
 		if resp.Node.MachineAuthorized {
 			nm.MachineStatus = tailcfg.MachineAuthorized
 		} else {

control/controlclient/netmap.go

@@ -24,13 +24,12 @@ import (
 type NetworkMap struct {
 	// Core networking
 
+	SelfNode   *tailcfg.Node
 	NodeKey    tailcfg.NodeKey
 	PrivateKey wgkey.Private
 	Expiry     time.Time
 	// Name is the DNS name assigned to this node.
-	Name string
-	// DisplayName is the title to show for the node in client UIs.
-	DisplayName   string
+	Name          string
 	Addresses     []netaddr.IPPrefix
 	LocalPort     uint16 // used for debugging
 	MachineStatus tailcfg.MachineStatus