netdev - Re: [PATCH net-next 8/8] 8021q: Check return of dev_set

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Date:	Fri, 20 Jun 2008 12:08:55 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Wang Chen <wangchen@...fujitsu.com>
CC:	"David S. Miller" <davem@...emloft.net>,
	NETDEV <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 8/8] 8021q: Check return of dev_set_promiscuity/allmulti

Wang Chen wrote:
> Patrick McHardy said the following on 2008-6-20 17:47:
>> Wang Chen wrote:
>>> diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
>>> index 5d055c2..1f2669b 100644
>>> --- a/net/8021q/vlan_dev.c
>>> +++ b/net/8021q/vlan_dev.c
>>> @@ -547,12 +547,23 @@ static int vlan_dev_open(struct net_device *dev)
>>>      }
>>>      memcpy(vlan->real_dev_addr, real_dev->dev_addr, ETH_ALEN);
>>>  
>>> -    if (dev->flags & IFF_ALLMULTI)
>>> -        dev_set_allmulti(real_dev, 1);
>>> -    if (dev->flags & IFF_PROMISC)
>>> -        dev_set_promiscuity(real_dev, 1);
>>> +    if (dev->flags & IFF_ALLMULTI) {
>>> +        err = dev_set_allmulti(real_dev, 1);
>>> +        if (err < 0)
>>> +            goto out;
>>> +    }
>>> +    if (dev->flags & IFF_PROMISC) {
>>> +        err = dev_set_promiscuity(real_dev, 1);
>>> +        if (err < 0)
>>> +            goto out;
>>> +    }
>>>  
>>>      return 0;
>>> +
>>> +out:
>>> +    if (compare_ether_addr(dev->dev_addr, real_dev->dev_addr))
>>> +        dev_unicast_delete(real_dev, dev->dev_addr, dev->addr_len);
>>> +    return err;
>> This doesn't undo the operations that already succeeded.
>>
> 
> Why?
> Should I do
>  	dev_mc_unsync(real_dev, dev);
> 	dev_unicast_unsync(real_dev, dev);
> before dev_unicast_delete()?

When returning an error, the state shouldn't change at all,
so you need to:

- remove unicast address if changed
- restore old address in vlan->real_dev_addr
- undo dev_set_allmulti

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