From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
To: David Ahern <dsahern@gmail.com>, netdev@vger.kernel.org
Cc: bridge@lists.linux-foundation.org, roopa@cumulusnetworks.com,
davem@davemloft.net
Subject: Re: [PATCH net] net: bridge: clear bridge's private skb space on xmit
Date: Fri, 31 Jul 2020 20:38:33 +0300 [thread overview]
Message-ID: <968147d8-616d-364f-cf03-55bb7b08a518@cumulusnetworks.com> (raw)
In-Reply-To: <181931fb-dc60-7db6-60ac-b8ff1402efec@cumulusnetworks.com>
On 31/07/2020 20:37, Nikolay Aleksandrov wrote:
> On 31/07/2020 20:27, David Ahern wrote:
>> On 7/31/20 10:26 AM, Nikolay Aleksandrov wrote:
>>> We need to clear all of the bridge private skb variables as they can be
>>> stale due to the packet being recirculated through the stack and then
>>> transmitted through the bridge device. Similar memset is already done on
>>> bridge's input. We've seen cases where proxyarp_replied was 1 on routed
>>> multicast packets transmitted through the bridge to ports with neigh
>>> suppress which were getting dropped. Same thing can in theory happen with
>>> the port isolation bit as well.
>>>
>>> Fixes: 821f1b21cabb ("bridge: add new BR_NEIGH_SUPPRESS port flag to suppress arp and nd flood")
>>> Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
>>> ---
>>> net/bridge/br_device.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
>>> index 8c7b78f8bc23..9a2fb4aa1a10 100644
>>> --- a/net/bridge/br_device.c
>>> +++ b/net/bridge/br_device.c
>>> @@ -36,6 +36,8 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
>>> const unsigned char *dest;
>>> u16 vid = 0;
>>>
>>> + memset(skb->cb, 0, sizeof(struct br_input_skb_cb));
>>> +
>>> rcu_read_lock();
>>> nf_ops = rcu_dereference(nf_br_ops);
>>> if (nf_ops && nf_ops->br_dev_xmit_hook(skb)) {
>>>
>>
>> What's the performance hit of doing this on every packet?
>>
>> Can you just set a flag that tells the code to reset on recirculation?
>> Seems like br_input_skb_cb has space for that.
>>
>
> Virtually non-existent, we had a patch that turned that field into a 16 byte
> field so that is really 2 8 byte stores. It is already cache hot, we could
err, s/field/struct/
> initialize each individual field separately as br_input does.
>
> I don't want to waste flags on such thing, this makes it future-proof
> and I'll remove the individual field zeroing later which will alleviate
> the cost further.
>
>
next prev parent reply other threads:[~2020-07-31 17:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-31 16:26 [PATCH net] net: bridge: clear bridge's private skb space on xmit Nikolay Aleksandrov
2020-07-31 17:27 ` David Ahern
2020-07-31 17:37 ` Nikolay Aleksandrov
2020-07-31 17:38 ` Nikolay Aleksandrov [this message]
2020-07-31 17:51 ` Nikolay Aleksandrov
2020-07-31 18:10 ` Nikolay Aleksandrov
2020-08-02 12:50 ` [PATCH net v2] net: bridge: clear skb private space on bridge dev xmit Nikolay Aleksandrov
2020-08-03 22:58 ` David Miller
2020-08-03 22:27 ` [PATCH net] net: bridge: clear bridge's private skb space on xmit David Miller
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