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

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Message-ID: <09f58c4f-dec5-ebd1-3352-f2e240ddcbe5@ti.com>
Date:   Tue, 4 Aug 2020 23:56:12 +0300
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Kurt Kanzenbach <kurt@...utronix.de>,
        Petr Machata <petrm@...lanox.com>
CC:     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>,
        Russell King <linux@...linux.org.uk>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        Samuel Zou <zou_wei@...wei.com>, <netdev@...r.kernel.org>,
        Russell King <rmk+kernel@...linux.org.uk>
Subject: Re: [PATCH v3 1/9] ptp: Add generic ptp v2 header parsing function



On 31/07/2020 13:06, Kurt Kanzenbach wrote:
> On Thu Jul 30 2020, Petr Machata wrote:
>> Kurt Kanzenbach <kurt@...utronix.de> writes:
>>
>>> @@ -107,6 +107,37 @@ unsigned int ptp_classify_raw(const struct sk_buff *skb)
>>>   }
>>>   EXPORT_SYMBOL_GPL(ptp_classify_raw);
>>>   
>>> +struct ptp_header *ptp_parse_header(struct sk_buff *skb, unsigned int type)
>>> +{
>>> +	u8 *data = skb_mac_header(skb);
>>> +	u8 *ptr = data;
>>
>> One of the "data" and "ptr" variables is superfluous.
> 
> Yeah. Can be shortened to u8 *ptr = skb_mac_header(skb);

Actually usage of skb_mac_header(skb) breaks CPTS RX time-stamping on
am571x platform PATCH 6.

The CPSW RX timestamp requested after full packet put in SKB, but
before calling eth_type_trans().

So, skb->data pints on Eth header, but skb_mac_header() return garbage.

Below diff fixes it for me.

--- a/net/core/ptp_classifier.c
+++ b/net/core/ptp_classifier.c
@@ -109,7 +109,7 @@ EXPORT_SYMBOL_GPL(ptp_classify_raw);
  
  struct ptp_header *ptp_parse_header(struct sk_buff *skb, unsigned int type)
  {
-       u8 *data = skb_mac_header(skb);
+       u8 *data = skb->data;
         u8 *ptr = data;
  
         if (type & PTP_CLASS_VLAN)

> 
> However, I'll wait a bit before sending the next version. So, that the
> other maintainers have time to test their drivers.

-- 
Best regards,
grygorii