netdev - Re: [PATCH net-next 1/2] net: bridge: add support for user-controlled bool options

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Message-ID: <e2d49e09-ab36-7daa-9e88-178025bedcc7@cumulusnetworks.com>
Date:   Thu, 22 Nov 2018 18:01:29 +0200
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, roopa@...ulusnetworks.com,
        davem@...emloft.net, bridge@...ts.linux-foundation.org
Subject: Re: [PATCH net-next 1/2] net: bridge: add support for user-controlled
 bool options

On 22/11/2018 17:35, Andrew Lunn wrote:
> On Thu, Nov 22, 2018 at 06:29:24AM +0200, Nikolay Aleksandrov wrote:
>> We have been adding many new bridge options, a big number of which are
>> boolean but still take up netlink attribute ids and waste space in the skb.
>> Recently we discussed learning from link-local packets[1] and decided
>> yet another new boolean option will be needed, thus introducing this API
>> to save some bridge nl space.
>> The API supports changing the value of multiple boolean options at once
>> via the br_boolopt_multi struct which has an optmask (which options to
>> set, bit per opt) and optval (options' new values). Future boolean
>> options will only be added to the br_boolopt_id enum and then will have
>> to be handled in br_boolopt_toggle/get. The API will automatically
>> add the ability to change and export them via netlink, sysfs can use the
>> single boolopt function versions to do the same. The behaviour with
>> failing/succeeding is the same as with normal netlink option changing.
>>
>> If an option requires mapping to internal kernel flag or needs special
>> configuration to be enabled then it should be handled in
>> br_boolopt_toggle. It should also be able to retrieve an option's current
>> state via br_boolopt_get.
>>
>> [1] https://www.spinics.net/lists/netdev/msg532698.html
>>
>> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
>> ---
>>  include/uapi/linux/if_bridge.h | 18 +++++++++
>>  include/uapi/linux/if_link.h   |  1 +
>>  net/bridge/br.c                | 68 ++++++++++++++++++++++++++++++++++
>>  net/bridge/br_netlink.c        | 17 ++++++++-
>>  net/bridge/br_private.h        |  6 +++
>>  net/core/rtnetlink.c           |  2 +-
>>  6 files changed, 110 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
>> index e41eda3c71f1..6dc02c03bdf8 100644
>> --- a/include/uapi/linux/if_bridge.h
>> +++ b/include/uapi/linux/if_bridge.h
>> @@ -292,4 +292,22 @@ struct br_mcast_stats {
>>  	__u64 mcast_bytes[BR_MCAST_DIR_SIZE];
>>  	__u64 mcast_packets[BR_MCAST_DIR_SIZE];
>>  };
>> +
>> +/* bridge boolean options
>> + * IMPORTANT: if adding a new option do not forget to handle
>> + *            it in br_boolopt_toggle/get and bridge sysfs
>> + */
>> +enum br_boolopt_id {
>> +	BR_BOOLOPT_MAX
>> +};
>> +
>> +/* struct br_boolopt_multi - change multiple bridge boolean options
>> + *
>> + * @optval: new option values (bit per option)
>> + * @optmask: options to change (bit per option)
>> + */
>> +struct br_boolopt_multi {
>> +	__u32 optval;
>> +	__u32 optmask;
>> +};
> 
> Hi Nikolay
> 
> Thanks for handling this.
> 
> How many boolean options do we already have? What it the likelihood a
> u32 is going to be too small, in a couple of years time?
> 

It would mean doubling the number of current options and this is only for
boolean options so I think we're safe.

> I recently went through the pain of converting the u32 for
> representing link modes in the phylib API to a linux bitmap.  I'm just
> wondering if in the long run, using a linux bitmap right from the
> beginning would be better?
> 
>> +int br_boolopt_multi_toggle(struct net_bridge *br,
>> +			    struct br_boolopt_multi *bm)
>> +{
>> +	unsigned long bitmap = bm->optmask;
>> +	int err = 0;
>> +	int opt_id;
>> +
>> +	for_each_set_bit(opt_id, &bitmap, BR_BOOLOPT_MAX) {
>> +		bool on = !!(bm->optval & BIT(opt_id));
>> +
>> +		err = br_boolopt_toggle(br, opt_id, on);
>> +		if (err) {
>> +			br_debug(br, "boolopt multi-toggle error: option: %d current: %d new: %d error: %d\n",
>> +				 opt_id, br_boolopt_get(br, opt_id), on, err);
> 
> Would it be possible to return that to userspace using the extended
> error infrastructure?
> 

No, it doesn't support dynamic messages AFAIK.

>       Andrew
>