On Thu,  8 Sep 2022 13:59:07 +1000
David Gibson <david(a)gibson.dropbear.id.au> wrote:

> Currently --userns is only allowed when pasta is attaching to an existing
> netns or PID, and is prohibited when creating a new netns by spawning a
> command or shell.
> 
> With the new handling of userns, this check isn't neccessary.  I'm not sure
> if there's any use case for --userns with a spawned command, but it's
> strictly more flexible and requires zero extra code, so we might as well.

I think it's helpful because one might not be able to join a network
namespace without first joining a given user namespace.

So, if you want to run any network-ish command in such a network
namespace, using pasta instead of nsenter for whatever reason, this
possibility might be practical.

> Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
> ---
>  conf.c | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/conf.c b/conf.c
> index 27d520e..ec191c2 100644
> --- a/conf.c
> +++ b/conf.c
> @@ -561,11 +561,6 @@ static int conf_pasta_ns(int *netns_only, char *userns, char *netns,
>  		}
>  	}
>  
> -	if (*userns && !*netns) {
> -		err("--userns requires --netns or PID");
> -		return -EINVAL;
> -	}

I guess we should now drop this sentence about --userns from the man
page:

  This option requires --netns or a PID to be specified.

...either drop it, or clarify that a command might also be given
instead, I'm not sure.

-- 
Stefano