netdev - Re: [PATCH iproute2-next 8/9] utils: Introduce and use print_name_and

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Date:   Wed, 7 Feb 2018 08:59:47 -0700
From:   David Ahern <dsahern@...il.com>
To:     Serhey Popovych <serhe.popovych@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH iproute2-next 8/9] utils: Introduce and use
 print_name_and_link() to print name@...k

On 2/7/18 12:36 AM, Serhey Popovych wrote:
>>
>> This patch is causing a diff on my system:
>>
>> # ip  -br add sh > /tmp/1
>> # ip/ip  -br add sh > /tmp/2
>> # diff /tmp/1 /tmp/2
>> 8c8
>> < veth-out@br3     UP             fe80::18a8:89ff:fee7:55c5/64
>> ---
>>> veth-out@if7     UP             fe80::18a8:89ff:fee7:55c5/64
>>
>> So the current ip resolves ifindex 7 to br3:
>>
>> # ip li sh dev br3
>> 7: br3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master
>> vrf3 state UP mode DEFAULT group default qlen 1000
>>
>> where your patch causes if%d to be printed.
>>
> 
> That's interesting. I guess output comes from ll_idx_n2a() in this
> change when both IFLA_LINK and IFLA_LINK_NETNS is seen.
> 
> My guess about this case is following:
> 
>   1) veth-out is of "veth" rtnl kind. (ip -d li sh dev veth-out).
> 
>   2) according to drivers/net/veth.c veth_get_iflink() and
>      veth_get_link_net() IFLA_LINK and IFLA_LINK_NETNS are taken
>      from peer device.
> 
>   3) seeing @br3 in current ip output looks confusing according to (2)
>      as veth do not link to something other than it's peer that is in
>      different network namespace.
> 
> From (3) I guess @br3 is incorrect value and caused by missing
> IFLA_LINK_NETNS handling in old print_linkinfo_brief(): it always
> calls ll_index_to_name().
> 

you are right; if7 is the right output so the current 'br3' is a bug and
it only happens with the brief output.