netdev - Re: [PATCH 7/8] net: Allow setting the network namespace by fd

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Message-ID: <m18w2sh1vf.fsf@fess.ebiederm.org>
Date:	Thu, 23 Sep 2010 09:16:04 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Brian Haley <brian.haley@...com>
Cc:	linux-kernel@...r.kernel.org,
	Linux Containers <containers@...ts.osdl.org>,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, jamal <hadi@...erus.ca>,
	Daniel Lezcano <daniel.lezcano@...e.fr>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Ulrich Drepper <drepper@...il.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	David Miller <davem@...emloft.net>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Ben Greear <greearb@...delatech.com>,
	Matt Helsley <matthltc@...ibm.com>,
	Jonathan Corbet <corbet@....net>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	Jan Engelhardt <jengelh@...ozas.de>,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH 7/8] net: Allow setting the network namespace by fd

Brian Haley <brian.haley@...com> writes:

> On 09/23/2010 04:51 AM, Eric W. Biederman wrote:
>> 
>> Take advantage of the new abstraction and allow network devices
>> to be placed in any network namespace that we have a fd to talk
>> about.
>> 
> ...
>> +struct net *get_net_ns_by_fd(int fd)
>> +{
>> +	struct proc_inode *ei;
>> +	struct file *file;
>> +	struct net *net;
>> +
>> +	file = NULL;
>
> No need to initialize this.
>
>> +	net = ERR_PTR(-EINVAL);
>
> or this?
>
>> +	file = proc_ns_fget(fd);
>> +	if (!fd)
>> +		goto out;
>> +		return ERR_PTR(-EINVAL);
>
> Shouldn't this be:
>
> 	if (!file)
>
> And the "goto" seems wrong, especially without a {} here.  Unless you
> meant to keep the "goto" and branch below?

I think I changed my mind half way through writing the code and never
did anything about it.  Oops.

Thanks fixed.  It is now:

struct net *get_net_ns_by_fd(int fd)
{
	struct proc_inode *ei;
	struct file *file;
	struct net *net;

	net = ERR_PTR(-EINVAL);
	file = proc_ns_fget(fd);
	if (!file)
		goto out;

	ei = PROC_I(file->f_dentry->d_inode);
	if (ei->ns_ops != &netns_operations)
		goto out;

	net = get_net(ei->ns);
out:
	if (file)
		fput(file);
	return net;
}

Which at least makes sense.  Now to test it to double check it does what
it should do.

Eric
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