Le 13/05/2019 à 17:07, David Ahern a écrit :
> On 5/13/19 7:47 AM, Sabrina Dubroca wrote:
>> Currently, nla_put_iflink() doesn't put the IFLA_LINK attribute when
>> iflink == ifindex.
>>
>> In some cases, a device can be created in a different netns with the
>> same ifindex as its parent. That device will not dump its IFLA_LINK
>> attribute, which can confuse some userspace software that expects it.
>> For example, if the last ifindex created in init_net and foo are both
>> 8, these commands will trigger the issue:
>>
>> ip link add parent type dummy # ifindex 9
>> ip link add link parent netns foo type macvlan # ifindex 9 in ns foo
>>
>> So, in case a device puts the IFLA_LINK_NETNSID attribute in a dump,
>> always put the IFLA_LINK attribute as well.
>>
>> Thanks to Dan Winship for analyzing the original OpenShift bug down to
>> the missing netlink attribute.
>>
>> Analyzed-by: Dan Winship <d...@redhat.com>
>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>> Signed-off-by: Sabrina Dubroca <s...@queasysnail.net>
>> Acked-by: Nicolas Dichtel <nicolas.dich...@6wind.com>
>> ---
>> v2: change Fixes tag, it's been here forever as Nicolas said, and add his Ack
>>
>> net/core/rtnetlink.c | 16 ++++++++++------
>> 1 file changed, 10 insertions(+), 6 deletions(-)
>>
>> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>> index 2bd12afb9297..adcc045952c2 100644
>> --- a/net/core/rtnetlink.c
>> +++ b/net/core/rtnetlink.c
>> @@ -1496,14 +1496,15 @@ static int put_master_ifindex(struct sk_buff *skb,
>> struct net_device *dev)
>> return ret;
>> }
>>
>> -static int nla_put_iflink(struct sk_buff *skb, const struct net_device *dev)
>> +static int nla_put_iflink(struct sk_buff *skb, const struct net_device *dev,
>> + bool force)
>> {
>> int ifindex = dev_get_iflink(dev);
>>
>> - if (dev->ifindex == ifindex)
>> - return 0;
>> + if (force || dev->ifindex != ifindex)
>> + return nla_put_u32(skb, IFLA_LINK, ifindex);
>>
>> - return nla_put_u32(skb, IFLA_LINK, ifindex);
>> + return 0;
>> }
>>
>> static noinline_for_stack int nla_put_ifalias(struct sk_buff *skb,
>
> why not always adding the attribute?
>
Adding this attribute may change the output of 'ip link'.
See this patch for example:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=95ec655bc465
Nicolas
