linux-kernel - Re: [PATCH net] net: ethernet: ti: am65-cpts: Fix PTPv1 message type on TX packets

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Message-ID: <52c7352f-a91b-3604-5ae0-88d7bb814e51@ti.com>
Date: Tue, 23 Apr 2024 16:36:24 +0530
From: Ravi Gunasekaran <r-gunasekaran@...com>
To: Paolo Abeni <pabeni@...hat.com>, <s-vadapalli@...com>, <rogerq@...nel.org>
CC: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <richardcochran@...il.com>, <jreeder@...com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <srk@...com>,
        Ravi Gunasekaran
	<r-gunasekaran@...com>
Subject: Re: [PATCH net] net: ethernet: ti: am65-cpts: Fix PTPv1 message type
 on TX packets

Paolo,

On 4/23/24 3:31 PM, Paolo Abeni wrote:
> On Fri, 2024-04-19 at 13:35 +0530, Ravi Gunasekaran wrote:
>> From: Jason Reeder <jreeder@...com>
>>
>> The CPTS, by design, captures the messageType (Sync, Delay_Req, etc.)
>> field from the second nibble of the PTP header which is defined in the
>> PTPv2 (1588-2008) specification. In the PTPv1 (1588-2002) specification
>> the first two bytes of the PTP header are defined as the versionType
>> which is always 0x0001. This means that any PTPv1 packets that are
>> tagged for TX timestamping by the CPTS will have their messageType set
>> to 0x0 which corresponds to a Sync message type. This causes issues
>> when a PTPv1 stack is expecting a Delay_Req (messageType: 0x1)
>> timestamp that never appears.
>>
>> Fix this by checking if the ptp_class of the timestamped TX packet is
>> PTP_CLASS_V1 and then matching the PTP sequence ID to the stored
>> sequence ID in the skb->cb data structure. If the sequence IDs match
>> and the packet is of type PTPv1 then there is a chance that the
>> messageType has been incorrectly stored by the CPTS so overwrite the
>> messageType stored by the CPTS with the messageType from the skb->cb
>> data structure. This allows the PTPv1 stack to receive TX timestamps
>> for Delay_Req packets which are necessary to lock onto a PTP Leader.
>>
>> Signed-off-by: Jason Reeder <jreeder@...com>
>> Signed-off-by: Ravi Gunasekaran <r-gunasekaran@...com>
> 
> Please provide a suitable fixes tag, thanks!

am65_cpts_match_tx_ts() was added in the very first commit of the file.
Would that be a suitable fixes tag? I understand that the purpose of
the fixes tag is to know to which all previous kernels, the fix needs to
be applied. 

Please let me know, if it is ok to provide first commit as fixes tag, so that
I can send a v2.

> 
> Paolo
> 

-- 
Regards,
Ravi