linux-kernel - Re: [PATCH net-next v1 2/9] net: dsa: tag

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Date:   Sun, 4 Apr 2021 07:35:26 +0200
From:   Oleksij Rempel <linux@...pel-privat.de>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Oleksij Rempel <o.rempel@...gutronix.de>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org
Subject: Re: [PATCH net-next v1 2/9] net: dsa: tag_ar9331: detect IGMP and MLD
 packets

Am 04.04.21 um 02:02 schrieb Vladimir Oltean:
> On Sat, Apr 03, 2021 at 07:14:56PM +0200, Oleksij Rempel wrote:
>> Am 03.04.21 um 16:49 schrieb Andrew Lunn:
>>>> @@ -31,6 +96,13 @@ static struct sk_buff *ar9331_tag_xmit(struct sk_buff *skb,
>>>>  	__le16 *phdr;
>>>>  	u16 hdr;
>>>>
>>>> +	if (dp->stp_state == BR_STATE_BLOCKING) {
>>>> +		/* TODO: should we reflect it in the stats? */
>>>> +		netdev_warn_once(dev, "%s:%i dropping blocking packet\n",
>>>> +				 __func__, __LINE__);
>>>> +		return NULL;
>>>> +	}
>>>> +
>>>>  	phdr = skb_push(skb, AR9331_HDR_LEN);
>>>>
>>>>  	hdr = FIELD_PREP(AR9331_HDR_VERSION_MASK, AR9331_HDR_VERSION);
>>>
>>> Hi Oleksij
>>>
>>> This change does not seem to fit with what this patch is doing.
>>
>> done
>>
>>> I also think it is wrong. You still need BPDU to pass through a
>>> blocked port, otherwise spanning tree protocol will be unstable.
>>
>> We need a better filter, otherwise, in case of software based STP, we are leaking packages on
>> blocked port. For example DHCP do trigger lots of spam in the kernel log.
>
> I have no idea whatsoever what 'software based STP' is, if you have
> hardware-accelerated forwarding.

I do not mean hardware-accelerated forwarding, i mean
hardware-accelerated STP port state helpers.

>> I'll drop STP patch for now, it will be better to make a generic soft STP for all switches without
>> HW offloading. For example ksz9477 is doing SW based STP in similar way.
>
> How about we discuss first about what your switch is not doing properly?
> Have you debugged more than just watching the bridge change port states?
> As Andrew said, a port needs to accept and send link-local frames
> regardless of the STP state. In the BLOCKING state it must send no other
> frames and have address learning disabled. Is this what's happening, is
> the switch forwarding frames towards a BLOCKING port?

The switch is not forwarding BPDU frame to the CPU port. So, the linux
bridge will stack by cycling different state of the port where loop was
detected.

--
Regards,
Oleksij