Re: [PATCH 02/10] pasta: Improve error handling on failure to join network namespace

[David Gibson <david@gibson.dropbear.id.au>]

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On Sun, May 14, 2023 at 08:14:07PM +0200, Stefano Brivio wrote:
> In pasta_wait_for_ns(), open() failing with ENOENT is expected: we're
> busy-looping until the network namespace appears. But any other
> failure is not something we're going to recover from: return right
> away if we don't get either success or ENOENT.
> 
> Now that pasta_wait_for_ns() can actually fail, handle that in
> pasta_start_ns() by reporting the issue and exiting.
> 
> Looping on EPERM, when pasta doesn't actually have the permissions to
> join a given namespace, isn't exactly a productive thing to do.
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

Also makes sense regardless of the rest of the series.

> ---
>  pasta.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/pasta.c b/pasta.c
> index 3a4d704..2fa0168 100644
> --- a/pasta.c
> +++ b/pasta.c
> @@ -94,8 +94,11 @@ static int pasta_wait_for_ns(void *arg)
>  	char ns[PATH_MAX];
>  
>  	snprintf(ns, PATH_MAX, "/proc/%i/ns/net", pasta_child_pid);
> -	do
> -		while ((c->pasta_netns_fd = open(ns, flags)) < 0);
> +	while ((c->pasta_netns_fd = open(ns, flags)) < 0) {
> +		if (errno != ENOENT)
> +			return 0;
> +	}
> +
>  	while (setns(c->pasta_netns_fd, CLONE_NEWNET) &&
>  	       !close(c->pasta_netns_fd));
>  
> @@ -252,6 +255,8 @@ void pasta_start_ns(struct ctx *c, uid_t uid, gid_t gid,
>  	}
>  
>  	NS_CALL(pasta_wait_for_ns, c);
> +	if (c->pasta_netns_fd < 0)
> +		die("Failed to join network namespace");
>  }
>  
>  /**

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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