netdev - Re: [PATCH net-next v4 4/6] net: bridge: Add netlink knobs for number / max learned FDB entries

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Date: Thu, 21 Sep 2023 15:51:45 +0300
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Johannes Nixdorf <jnixdorf-oss@....de>,
 "David S. Miller" <davem@...emloft.net>, Andrew Lunn <andrew@...n.ch>,
 David Ahern <dsahern@...il.com>, Eric Dumazet <edumazet@...gle.com>,
 Florian Fainelli <f.fainelli@...il.com>, Ido Schimmel <idosch@...dia.com>,
 Jakub Kicinski <kuba@...nel.org>, Oleksij Rempel <linux@...pel-privat.de>,
 Paolo Abeni <pabeni@...hat.com>, Roopa Prabhu <roopa@...dia.com>,
 Shuah Khan <shuah@...nel.org>, Vladimir Oltean <vladimir.oltean@....com>
Cc: bridge@...ts.linux-foundation.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v4 4/6] net: bridge: Add netlink knobs for number
 / max learned FDB entries

On 9/21/23 15:41, Nikolay Aleksandrov wrote:
> On 9/19/23 11:12, Johannes Nixdorf wrote:
>> The previous patch added accounting and a limit for the number of
>> dynamically learned FDB entries per bridge. However it did not provide
>> means to actually configure those bounds or read back the count. This
>> patch does that.
>>
>> Two new netlink attributes are added for the accounting and limit of
>> dynamically learned FDB entries:
>>   - IFLA_BR_FDB_N_LEARNED (RO) for the number of entries accounted for
>>     a single bridge.
>>   - IFLA_BR_FDB_MAX_LEARNED (RW) for the configured limit of entries for
>>     the bridge.
>>
>> The new attributes are used like this:
>>
>>   # ip link add name br up type bridge fdb_max_learned 256
>>   # ip link add name v1 up master br type veth peer v2
>>   # ip link set up dev v2
>>   # mausezahn -a rand -c 1024 v2
>>   0.01 seconds (90877 packets per second
>>   # bridge fdb | grep -v permanent | wc -l
>>   256
>>   # ip -d link show dev br
>>   13: br: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 [...]
>>       [...] fdb_n_learned 256 fdb_max_learned 256
>>
>> Signed-off-by: Johannes Nixdorf <jnixdorf-oss@....de>
>> ---
>>   include/uapi/linux/if_link.h |  2 ++
>>   net/bridge/br_netlink.c      | 15 ++++++++++++++-
>>   2 files changed, 16 insertions(+), 1 deletion(-)
[snip]
>> @@ -1670,7 +1680,10 @@ static int br_fill_info(struct sk_buff *skb, 
>> const struct net_device *brdev)
>>           nla_put_u8(skb, IFLA_BR_TOPOLOGY_CHANGE_DETECTED,
>>                  br->topology_change_detected) ||
>>           nla_put(skb, IFLA_BR_GROUP_ADDR, ETH_ALEN, br->group_addr) ||
>> -        nla_put(skb, IFLA_BR_MULTI_BOOLOPT, sizeof(bm), &bm))
>> +        nla_put(skb, IFLA_BR_MULTI_BOOLOPT, sizeof(bm), &bm) ||
>> +        nla_put_u32(skb, IFLA_BR_FDB_N_LEARNED,
>> +            atomic_read(&br->fdb_n_learned)) ||
>> +        nla_put_u32(skb, IFLA_BR_FDB_MAX_LEARNED, br->fdb_max_learned))
>>           return -EMSGSIZE;
>>   #ifdef CONFIG_BRIDGE_VLAN_FILTERING
>>
> 
> Actually you're using atomic for counting, but using a u32 for the 
> limit, you should cap it because the count can overflow. Or you should
> use atomic64 for the counting.
> 

Scratch all that, I'm speaking nonsense. Need to refresh my mind. :)
EVerything's alright. Sorry for the noise.