netdev - Re: [PATCH v2 net-next] net/ipv6: Do not allow route add with a device that is down

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Date:   Wed, 24 Jan 2018 10:37:28 -0700
From:   David Ahern <dsahern@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org,
        idosch@...lanox.com, roopa@...ulusnetworks.com
Subject: Re: [PATCH v2 net-next] net/ipv6: Do not allow route add with a
 device that is down

On 1/24/18 10:09 AM, Stephen Hemminger wrote:
> On Wed, 24 Jan 2018 08:29:24 -0800
> David Ahern <dsahern@...il.com> wrote:
> 
>> IPv6 allows routes to be installed when the device is not up (admin up).
>> Worse, it does not mark it as LINKDOWN. IPv4 does not allow it and really
>> there is no reason for IPv6 to allow it, so check the flags and deny if
>> device is admin down.
>>
>> Signed-off-by: David Ahern <dsahern@...il.com>
>> ---
>> v2
>> - missed setting err to -ENETDOWN (thanks for catching that Roopa)
>>
>>  net/ipv6/route.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
>> index f85da2f1e729..4e8fab766018 100644
>> --- a/net/ipv6/route.c
>> +++ b/net/ipv6/route.c
>> @@ -2734,6 +2734,12 @@ static struct rt6_info *ip6_route_info_create(struct fib6_config *cfg,
>>  	if (!dev)
>>  		goto out;
>>  
>> +	err = -ENETDOWN;
>> +	if (!(dev->flags & IFF_UP)) {
>> +		NL_SET_ERR_MSG(extack, "Nexthop device is not up");
>> +		goto out;
>> +	}
>> +
>>  	if (!ipv6_addr_any(&cfg->fc_prefsrc)) {
>>  		if (!ipv6_chk_addr(net, &cfg->fc_prefsrc, dev, 0)) {
>>  			NL_SET_ERR_MSG(extack, "Invalid source address");
> 
> This looks like a good idea.
> 
> There are two equal ways to check for admin up. Either the dev flags or
> look at link state via netif_running().  Maybe the latter would
> be better.
> 

I used dev->flags for consistency with IPv4. Looking at use of
netif_running vs dev->flags in IPv4 and IPv6 code the flag is much more
prevalent.