tailcfg: add StableID to Node. #1178

Signed-off-by: David Anderson <danderson@tailscale.com>

tailcfg/tailcfg.go

@@ -35,6 +35,8 @@ import (
 //    10: 2021-01-17: client understands MapResponse.PeerSeenChange
 const CurrentMapRequestVersion = 10
 
+type StableID string
+
 type ID int64
 
 type UserID ID
@@ -55,6 +57,12 @@ func (u NodeID) IsZero() bool {
 	return u == 0
 }
 
+type StableNodeID StableID
+
+func (u StableNodeID) IsZero() bool {
+	return u == ""
+}
+
 type GroupID ID
 
 func (u GroupID) IsZero() bool {
@@ -148,8 +156,9 @@ type UserProfile struct {
 }
 
 type Node struct {
-	ID   NodeID
-	Name string // DNS
+	ID       NodeID
+	StableID StableNodeID
+	Name     string // DNS
 
 	// User is the user who created the node. If ACL tags are in
 	// use for the node then it doesn't reflect the ACL identity
@@ -785,6 +794,7 @@ func (n *Node) Equal(n2 *Node) bool {
 	}
 	return n != nil && n2 != nil &&
 		n.ID == n2.ID &&
+		n.StableID == n2.StableID &&
 		n.Name == n2.Name &&
 		n.User == n2.User &&
 		n.Sharer == n2.Sharer &&

tailcfg/tailcfg_clone.go

@@ -62,6 +62,7 @@ func (src *Node) Clone() *Node {
 //   tailscale.com/cmd/cloner -type User,Node,Hostinfo,NetInfo,Group,Role,Capability,Login,DNSConfig,RegisterResponse
 var _NodeNeedsRegeneration = Node(struct {
 	ID                NodeID
+	StableID          StableNodeID
 	Name              string
 	User              UserID
 	Sharer            UserID

tailcfg/tailcfg_test.go

@@ -189,7 +189,7 @@ func TestHostinfoEqual(t *testing.T) {
 
 func TestNodeEqual(t *testing.T) {
 	nodeHandles := []string{
-		"ID", "Name", "User", "Sharer",
+		"ID", "StableID", "Name", "User", "Sharer",
 		"Key", "KeyExpiry", "Machine", "DiscoKey",
 		"Addresses", "AllowedIPs", "Endpoints", "DERP", "Hostinfo",
 		"Created", "LastSeen", "KeepAlive", "MachineAuthorized",
@@ -229,6 +229,31 @@ func TestNodeEqual(t *testing.T) {
 			&Node{},
 			true,
 		},
+		{
+			&Node{},
+			&Node{},
+			true,
+		},
+		{
+			&Node{ID: 1},
+			&Node{},
+			false,
+		},
+		{
+			&Node{ID: 1},
+			&Node{ID: 1},
+			true,
+		},
+		{
+			&Node{StableID: "node-abcd"},
+			&Node{},
+			false,
+		},
+		{
+			&Node{StableID: "node-abcd"},
+			&Node{StableID: "node-abcd"},
+			true,
+		},
 		{
 			&Node{User: 0},
 			&Node{User: 1},