On 07/21/2015 12:28 AM, Stephen Hemminger wrote:
> On Fri, 10 Jul 2015 08:02:08 -0700
> Nikolay Aleksandrov <niko...@cumulusnetworks.com> wrote:
>
>> diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
>> index eaaea6208b42..3635b7797508 100644
>> --- a/include/uapi/linux/if_bridge.h
>> +++ b/include/uapi/linux/if_bridge.h
>> @@ -182,6 +182,7 @@ struct br_mdb_entry {
>> #define MDB_TEMPORARY 0
>> #define MDB_PERMANENT 1
>> __u8 state;
>> + __u16 vid;
>> struct {
>> union {
>> __be32 ip4;
>
> You added a new field into an unused hole in a data
> structure shared as part of API with user space.
>
> This seems like it might break when newer iproute
> is run on older kernels. The vid would always be 0
> on show and ignored when adding entries.
>
I thought it'd be fine because the vid was 0 anyway and
when it's 0 it's not shown i.e. no vid so the show command
will have the same output. And when set - it'll be ignored
which is again as the behaviour before when it couldn't be
specified.
Here's the new iproute2 on an older kernel:
# ./bridge/bridge mdb add dev virbr0 port vnet1 grp 239.0.0.1 permanent vid 200
# ./bridge/bridge mdb
dev virbr0 port vnet1 grp 239.0.0.1 permanent
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