From cd34d441be2f277221e81672125f73ec3e8cb16d Mon Sep 17 00:00:00 2001
From: Will Norris <will@tailscale.com>
Date: Thu, 12 Dec 2024 10:33:13 -0800
Subject: [PATCH] cmd/tailscale: add tailnet info to whoami output

Updates #14375

Change-Id: Ia101a4a3005adb9118051b3416f5a64a4a45987d
Signed-off-by: Will Norris <will@tailscale.com>
---
 cmd/tailscale/cli/whoami.go |  2 +-
 cmd/tailscale/cli/whois.go  | 34 +++++++++++++++++++++++++++++++---
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/cmd/tailscale/cli/whoami.go b/cmd/tailscale/cli/whoami.go
index 495cb0c3d..5c7966216 100644
--- a/cmd/tailscale/cli/whoami.go
+++ b/cmd/tailscale/cli/whoami.go
@@ -48,5 +48,5 @@ func runWhoami(ctx context.Context, args []string) error {
 	if err != nil {
 		return err
 	}
-	return printWhoIs(who, whoamiArgs.json)
+	return printWhoIs(who, st.CurrentTailnet, whoamiArgs.json)
 }
diff --git a/cmd/tailscale/cli/whois.go b/cmd/tailscale/cli/whois.go
index 0b8e407d6..c6cae118c 100644
--- a/cmd/tailscale/cli/whois.go
+++ b/cmd/tailscale/cli/whois.go
@@ -4,6 +4,7 @@
 package cli
 
 import (
+	"cmp"
 	"context"
 	"encoding/json"
 	"errors"
@@ -14,6 +15,8 @@
 
 	"github.com/peterbourgon/ff/v3/ffcli"
 	"tailscale.com/client/tailscale/apitype"
+	"tailscale.com/ipn/ipnstate"
+	"tailscale.com/tailcfg"
 )
 
 var whoisCmd = &ffcli.Command{
@@ -47,16 +50,27 @@ func runWhoIs(ctx context.Context, args []string) error {
 	if err != nil {
 		return err
 	}
-	return printWhoIs(who, whoIsArgs.json)
+	return printWhoIs(who, nil, whoIsArgs.json)
+}
+
+// whoisAndTailnet combines a WhoIsResponse and TailnetStatus for display.
+type whoisAndTailnet struct {
+	*apitype.WhoIsResponse
+	CurrentTailnet *ipnstate.TailnetStatus `json:",omitzero"`
 }
 
 // printWhoIs prints the WhoIsResponse to Stdout, either as JSON (if asJSON is
 // true) or in a human-readable form.
-func printWhoIs(who *apitype.WhoIsResponse, asJSON bool) error {
+// If tailnet is non-nil, tailnet information is included in the output.
+func printWhoIs(who *apitype.WhoIsResponse, tailnet *ipnstate.TailnetStatus, asJSON bool) error {
+	wat := whoisAndTailnet{
+		WhoIsResponse:  who,
+		CurrentTailnet: tailnet,
+	}
 	if asJSON {
 		ec := json.NewEncoder(Stdout)
 		ec.SetIndent("", "  ")
-		ec.Encode(who)
+		ec.Encode(wat)
 		return nil
 	}
 
@@ -75,6 +89,20 @@ func printWhoIs(who *apitype.WhoIsResponse, asJSON bool) error {
 		fmt.Fprintf(w, "  Name:\t%s\n", who.UserProfile.LoginName)
 		fmt.Fprintf(w, "  ID:\t%d\n", who.UserProfile.ID)
 	}
+	if tailnet != nil {
+		// use the tailnet display name, if present
+		var displayName string
+		if who.Node.HasCap(tailcfg.NodeAttrTailnetDisplayName) {
+			v, err := tailcfg.UnmarshalNodeCapJSON[string](who.Node.CapMap, tailcfg.NodeAttrTailnetDisplayName)
+			if err == nil && len(v) > 0 {
+				displayName = v[0]
+			}
+		}
+		fmt.Fprintln(w, "Tailnet:")
+		// TODO(will@): plumb through StableTailnetID so we can show that here as well
+		fmt.Fprintf(w, "  Name:\t%s\n", cmp.Or(displayName, tailnet.Name))
+		fmt.Fprintf(w, "  MagicDNS Suffix:\t%s\n", tailnet.MagicDNSSuffix)
+	}
 	w.Flush()
 	w = nil // avoid accidental use