netdev - Re: [PATCH v3 1/9] ptp: Add generic ptp v2 header parsing function

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Date:   Wed, 5 Aug 2020 22:15:04 +0300
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Kurt Kanzenbach <kurt@...utronix.de>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>
CC:     Petr Machata <petrm@...lanox.com>,
        Richard Cochran <richardcochran@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jiri Pirko <jiri@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        Samuel Zou <zou_wei@...wei.com>, <netdev@...r.kernel.org>
Subject: Re: [PATCH v3 1/9] ptp: Add generic ptp v2 header parsing function



On 05/08/2020 16:57, Kurt Kanzenbach wrote:
> On Wed Aug 05 2020, Grygorii Strashko wrote:
>> I really do not want touch netcp, sry.
>> There are other internal code based on this even if there is only one hooks in LKML now.
>> + my comment above.
> 
> OK, I see. The use of lists makes more sense now.
> 
>>
>> I'll try use skb_reset_mac_header(skb);
>> As spectrum does:
>>    	skb_reset_mac_header(skb);
>> 	mlxsw_sp1_ptp_got_packet(mlxsw_sp, skb, local_port, true);
>>
>> if doesn't help PATCH 6 is to drop.
> 
> So, only patch 6 is to drop or 5 as well? Anyhow, I'll wait for your
> test results. Thanks!

Patch 5 not affected as all RX packet have timestamp and it's coming different way.
TX not affected as skb come to .xmit() properly initialized.

As I've just replied for patch 6 - skb_reset_mac_header() helps.

Rhetorical question - is below check really required?
Bad packets (short, crc) expected to be discarded by HW

	/* Ensure that the entire header is present in this packet. */
	if (ptr + sizeof(struct ptp_header) > skb->data + skb->len)
		return NULL;


And I'd like to ask you to update ptp_parse_header() documentation
with description of expected SKB state for this function to work.


-- 
Best regards,
grygorii