netdev - Re: [PATCH 2/2] Virtual ethernet device driver

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Date:	Thu, 12 Jul 2007 15:21:09 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Pavel Emelianov <xemul@...nvz.org>
CC:	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH 2/2] Virtual ethernet device driver

Pavel Emelianov wrote:
> Patrick McHardy wrote:
> 
>>Pavel Emelianov wrote:
>>
>>>+static int veth_newlink(struct net_device *dev,
>>>+			 struct nlattr *tb[], struct nlattr *data[])
>>>+{
>>>+	int err;
>>>+	struct net_device *peer;
>>>+	struct veth_priv *priv;
>>>+	char ifname[IFNAMSIZ];
>>>+
>>>+	/*
>>>+	 * prepare the devices info
>>>+	 */
>>>+
>>>+	if (tb[IFLA_ADDRESS] == NULL)
>>>+		random_ether_addr(dev->dev_addr);
>>>+
>>>+	if (data != NULL && data[VETH_INFO_PEER] != NULL) {
>>>+		err = nla_parse_nested(tb, IFLA_INFO_MAX,
>>>+				data[VETH_INFO_PEER], ifla_policy);
>>>+		if (err < 0)
>>>+			return err;
>>>+	}
>>
>>
>>Not having a peer should be an error, no?
> 
> 
> No. That's the intention - if the user doesn't specify "peer" in the
> command line then two _identical_ devices are created. Of course, if
> he specifies one name - there'll be a collision, but one can say
> "my_own_veth_number_%d" and everything will be ok. Or just use the 
> default name provided. E.g. "ip link add type veth" will send a packet
> with data[VETH_INFO_PEER} == NULL, but this is OK! User just wants a 
> default tunnel and he will get it :)

I see.

> Does this answer your second comment below?


No, to get unique names the sequence has to be:

dev_alloc_name
register_netdevice
dev_alloc_name
register_netdevice

But you have:

dev_alloc_name
dev_alloc_name (<- might allocate same name as first call)
register_netdevice
register_netdevice

>>>+static __exit void veth_exit(void)
>>>+{
>>>+	struct veth_priv *priv, *next;
>>>+
>>>+	rtnl_lock();
>>>+	__rtnl_link_unregister(&veth_link_ops);
>>>+
>>>+	list_for_each_entry_safe(priv, next, &veth_list, list)
>>>+		veth_dellink(priv->dev);
>>>+	rtnl_unlock();
>>
>>
>>Devices are unregistered automatically through the dellink function,
>>rtnl_link_unregister(..) is enough.
> 
> 
> OK. This looks like a minor and not-significant comment, so
> do I need to resend the patch or David is OK to take it and
> I will send an incremental one?


An incremental patch for this is fine I guess, your code is correct,
its merely a simplification.
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