Linux Ethernet Bridging - Dec 2019 - [Bridge] [PATCH net-next v2] net: bridge: add STP xstats

From: Vivien Didelot <vivien.didelot at gmail.com>
Date: Wed, 11 Dec 2019 13:41:33 -0500
> Hi David, Nikolay,
> 
> On Wed, 11 Dec 2019 17:42:33 +0200, Nikolay Aleksandrov <nikolay at
cumulusnetworks.com> wrote:
>> >>  /* Bridge multicast database attributes
>> >>   * [MDBA_MDB] = {
>> >>   *     [MDBA_MDB_ENTRY] = {
>> >> @@ -261,6 +270,7 @@ enum {
>> >>  	BRIDGE_XSTATS_UNSPEC,
>> >>  	BRIDGE_XSTATS_VLAN,
>> >>  	BRIDGE_XSTATS_MCAST,
>> >> +	BRIDGE_XSTATS_STP,
>> >>  	BRIDGE_XSTATS_PAD,
>> >>  	__BRIDGE_XSTATS_MAX
>> >>  };
>> > 
>> > Shouldn't the new entry be appended to the end - after
BRIDGE_XSTATS_PAD
>> > 
>> 
>> Oh yes, good catch. That has to be fixed, too.
>> 
> 
> This I don't get. Why new attributes must come between
BRIDGE_XSTATS_PAD
> and __BRIDGE_XSTATS_MAX?
Because, just like any other attribute value, BRIDGE_XSTATS_PAD is an
API and fixed in stone.  You can't add things before it which change
it's value.

Hi David,

On Wed, 11 Dec 2019 12:01:20 -0800 (PST), David Miller <davem at
davemloft.net> wrote:
> >> >>  /* Bridge multicast database attributes
> >> >>   * [MDBA_MDB] = {
> >> >>   *     [MDBA_MDB_ENTRY] = {
> >> >> @@ -261,6 +270,7 @@ enum {
> >> >>  	BRIDGE_XSTATS_UNSPEC,
> >> >>  	BRIDGE_XSTATS_VLAN,
> >> >>  	BRIDGE_XSTATS_MCAST,
> >> >> +	BRIDGE_XSTATS_STP,
> >> >>  	BRIDGE_XSTATS_PAD,
> >> >>  	__BRIDGE_XSTATS_MAX
> >> >>  };
> >> > 
> >> > Shouldn't the new entry be appended to the end - after
BRIDGE_XSTATS_PAD
> >> > 
> >> 
> >> Oh yes, good catch. That has to be fixed, too.
> >> 
> > 
> > This I don't get. Why new attributes must come between
BRIDGE_XSTATS_PAD
> > and __BRIDGE_XSTATS_MAX?
> 
> Because, just like any other attribute value, BRIDGE_XSTATS_PAD is an
> API and fixed in stone.  You can't add things before it which change
> it's value.
I thought the whole point of using enums was to avoid caring about fixed
numeric values, but well. To be more precise, what I don't get is that when
I move the BRIDGE_XSTATS_STP definition *after* BRIDGE_XSTATS_PAD, the STP
xstats don't show up anymore in iproute2.


Thanks,

	Vivien