From 77127a24948687c6a22f521a0eb020a78c5ab187 Mon Sep 17 00:00:00 2001
From: Andrew Lytvynov <awly@tailscale.com>
Date: Tue, 17 Oct 2023 14:24:06 -0700
Subject: [PATCH] clientupdate: fix background install for linux tarballs
 (#9852)

Two bug fixes:
1. when tailscale update is executed as root, `os.UserCacheDir` may
   return an error because `$XDG_CACHE_HOME` and `$HOME` are not set;
   fallback to `os.TempDir` in those cases
2. on some weird distros (like my EndeavourOS), `/usr/sbin` is just a
   symlink to `/usr/bin`; when we resolve `tailscale` binary path from
   `tailscaled`, allow `tailscaled` to be in either directory

Updates #755

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>
---
 clientupdate/clientupdate.go | 2 +-
 ipn/ipnlocal/c2n.go          | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/clientupdate/clientupdate.go b/clientupdate/clientupdate.go
index b42d912a9..9f1bc441f 100644
--- a/clientupdate/clientupdate.go
+++ b/clientupdate/clientupdate.go
@@ -911,7 +911,7 @@ func (up *Updater) updateLinuxBinary() error {
 func (up *Updater) downloadLinuxTarball(ver string) (string, error) {
 	dlDir, err := os.UserCacheDir()
 	if err != nil {
-		return "", err
+		dlDir = os.TempDir()
 	}
 	dlDir = filepath.Join(dlDir, "tailscale-update")
 	if err := os.MkdirAll(dlDir, 0700); err != nil {
diff --git a/ipn/ipnlocal/c2n.go b/ipn/ipnlocal/c2n.go
index e5510e2b9..d95c3e7cc 100644
--- a/ipn/ipnlocal/c2n.go
+++ b/ipn/ipnlocal/c2n.go
@@ -305,9 +305,12 @@ func findCmdTailscale() (string, error) {
 	}
 	switch runtime.GOOS {
 	case "linux":
-		if self == "/usr/sbin/tailscaled" {
+		if self == "/usr/sbin/tailscaled" || self == "/usr/bin/tailscaled" {
 			return "/usr/bin/tailscale", nil
 		}
+		if self == "/usr/local/sbin/tailscaled" || self == "/usr/local/bin/tailscaled" {
+			return "/usr/local/bin/tailscale", nil
+		}
 		return "", errors.New("tailscale not found in expected place")
 	case "windows":
 		dir := filepath.Dir(self)