From 70ba338cd8314410380b8bdae9e5f302e8e98039 Mon Sep 17 00:00:00 2001
From: Yedaya Katsman <yedaya.ka@gmail.com>
Date: Tue, 23 Apr 2024 21:38:20 +0300
Subject: ip: Exit exec in child process if setup fails

Reference: https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/commit/?id=70ba338cd8314410380b8bdae9e5f302e8e98039

If we forked, returning from the function will make the calling code to
continue in both the child and parent process. Make cmd_exec exit if
setup failed and it forked already.

An example of issues this causes, where a failure in setup causes
multiple unnecessary tries:

```
$ ip netns
ef
ab
$ ip -all netns exec ls

netns: ef
setting the network namespace "ef" failed: Operation not permitted

netns: ab
setting the network namespace "ab" failed: Operation not permitted

netns: ab
setting the network namespace "ab" failed: Operation not permitted
```

Signed-off-by: Yedaya Katsman <yedaya.ka@gmail.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/exec.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/exec.c b/lib/exec.c
index 9b1c8f4..5bd3e2d 100644
--- a/lib/exec.c
+++ b/lib/exec.c
@@ -36,8 +36,13 @@ int cmd_exec(const char *cmd, char **argv, bool do_fork,
 		}
 	}
 
-	if (setup && setup(arg))
+	if (setup && setup(arg)) {
+		if (do_fork) {
+		        /* In child, nothing to do */
+		        _exit(1);
+		}
 		return -1;
+	}
 
 	if (execvp(cmd, argv)  < 0)
 		fprintf(stderr, "exec of \"%s\" failed: %s\n",
-- 
2.27.0