From 84eaef0bbb405b9401c9820ae3d006daedba7e43 Mon Sep 17 00:00:00 2001
From: Brad Fitzpatrick <bradfitz@tailscale.com>
Date: Fri, 23 Dec 2022 12:36:31 -0800
Subject: [PATCH] ssh/tailssh: don't swallow process exit code in be-child

Thanks to @nshalman and @Soypete for debugging!

Updates #6054

Change-Id: I74550cc31f8a257b37351b8152634c768e1e0a8a
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
---
 ssh/tailssh/incubator.go | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/ssh/tailssh/incubator.go b/ssh/tailssh/incubator.go
index 5c975046b..c3e865630 100644
--- a/ssh/tailssh/incubator.go
+++ b/ssh/tailssh/incubator.go
@@ -283,7 +283,20 @@ func beIncubator(args []string) error {
 			Foreground: true,
 		}
 	}
-	return cmd.Run()
+	err = cmd.Run()
+	if ee, ok := err.(*exec.ExitError); ok {
+		ps := ee.ProcessState
+		code := ps.ExitCode()
+		if code < 0 {
+			// TODO(bradfitz): do we need to also check the syscall.WaitStatus
+			// and make our process look like it also died by signal/same signal
+			// as our child process? For now we just do the exit code.
+			fmt.Fprintf(os.Stderr, "[tailscale-ssh: process died: %v]\n", ps.String())
+			code = 1 // for now. so we don't exit with negative
+		}
+		os.Exit(code)
+	}
+	return err
 }
 
 // launchProcess launches an incubator process for the provided session.