ipn: allow FQDN in exit node selection

To match the format of exit node suggestions and ensure that the result
is not ambiguous, relax exit node CLI selection to permit using a FQDN
including the trailing dot.

Updates #12618

Change-Id: I04b9b36d2743154aa42f2789149b2733f8555d3f
Signed-off-by: Adrian Dewhurst <adrian@tailscale.com>

cmd/tailscale/cli/exitnode.go

@@ -156,8 +156,7 @@ func runExitNodeSuggest(ctx context.Context, args []string) error {
 		fmt.Println("No exit node suggestion is available.")
 		return nil
 	}
-	hostname := strings.TrimSuffix(res.Name, ".")
-	fmt.Printf("Suggested exit node: %v\nTo accept this suggestion, use `tailscale set --exit-node=%v`.\n", hostname, shellquote.Join(hostname))
+	fmt.Printf("Suggested exit node: %v\nTo accept this suggestion, use `tailscale set --exit-node=%v`.\n", res.Name, shellquote.Join(res.Name))
 	return nil
 }
 

ipn/prefs.go

@@ -810,7 +810,7 @@ func exitNodeIPOfArg(s string, st *ipnstate.Status) (ip netip.Addr, err error) {
 	match := 0
 	for _, ps := range st.Peer {
 		baseName := dnsname.TrimSuffix(ps.DNSName, st.MagicDNSSuffix)
-		if !strings.EqualFold(s, baseName) {
+		if !strings.EqualFold(s, baseName) && !strings.EqualFold(s, ps.DNSName) {
 			continue
 		}
 		match++

ipn/prefs_test.go

@@ -914,6 +914,21 @@ func TestExitNodeIPOfArg(t *testing.T) {
 			},
 			want: mustIP("1.0.0.2"),
 		},
+		{
+			name: "name_fqdn",
+			arg:  "skippy.foo.",
+			st: &ipnstate.Status{
+				MagicDNSSuffix: ".foo",
+				Peer: map[key.NodePublic]*ipnstate.PeerStatus{
+					key.NewNode().Public(): {
+						DNSName:        "skippy.foo.",
+						TailscaleIPs:   []netip.Addr{mustIP("1.0.0.2")},
+						ExitNodeOption: true,
+					},
+				},
+			},
+			want: mustIP("1.0.0.2"),
+		},
 		{
 			name: "name_not_exit",
 			arg:  "skippy",
@@ -928,6 +943,20 @@ func TestExitNodeIPOfArg(t *testing.T) {
 			},
 			wantErr: `node "skippy" is not advertising an exit node`,
 		},
+		{
+			name: "name_wrong_fqdn",
+			arg:  "skippy.bar.",
+			st: &ipnstate.Status{
+				MagicDNSSuffix: ".foo",
+				Peer: map[key.NodePublic]*ipnstate.PeerStatus{
+					key.NewNode().Public(): {
+						DNSName:      "skippy.foo.",
+						TailscaleIPs: []netip.Addr{mustIP("1.0.0.2")},
+					},
+				},
+			},
+			wantErr: `invalid value "skippy.bar." for --exit-node; must be IP or unique node name`,
+		},
 		{
 			name: "ambiguous",
 			arg:  "skippy",