Re: [PATCH net v3 2/4] net: add rx_nohandler stat counter

[David Miller <davem@davemloft.net>]

From: Stephen Hemminger <stephen@networkplumber.org>
Date: Sun, 7 Feb 2016 11:37:32 -0800

> On Mon,  1 Feb 2016 18:51:05 -0500
> Jarod Wilson <jarod@redhat.com> wrote:
> 
>> --- a/include/uapi/linux/if_link.h
>> +++ b/include/uapi/linux/if_link.h
>> @@ -35,6 +35,8 @@ struct rtnl_link_stats {
>>  	/* for cslip etc */
>>  	__u32	rx_compressed;
>>  	__u32	tx_compressed;
>> +
>> +	__u32	rx_nohandler;		/* dropped, no handler found	*/
>>  };
>>  
>>  /* The main device statistics structure */
>> @@ -68,6 +70,8 @@ struct rtnl_link_stats64 {
>>  	/* for cslip etc */
>>  	__u64	rx_compressed;
>>  	__u64	tx_compressed;
>> +
>> +	__u64	rx_nohandler;		/* dropped, no handler found	*/
>>  };
> 
> Why was this userspace ABI change allowed?
> The stats structure is exposed to user space via netlink
> and changing the size of responses will break iproute2 commands.
> 
> The code will be expecting one size and the response will vary and
> break existing code.  Yes, the code should check the size
> of the response, but it doesn't and I am sure iproute2 is not
> the only code that does this.

Jarod, please look into this.