Re: [PATCH v3 02/10] pasta: Improve error handling on failure to join network namespace

[Stefano Brivio <sbrivio@redhat.com>]

On Mon, 22 May 2023 19:45:59 +0200
Stefano Brivio <sbrivio@redhat.com> 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>
> ---
>  pasta.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/pasta.c b/pasta.c
> index b30ce70..2a6fb60 100644
> --- a/pasta.c
> +++ b/pasta.c
> @@ -95,8 +95,11 @@ 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));

Oops, what did I do here... :( On a failed setns(), we need (in most
cases) to close and reopen the file.

The fix and intention are quite obvious so I'm just fixing this up
now as I'm applying it.

-- 
Stefano