On Wed Aug 05 2020, Russell King - ARM Linux admin wrote:

On Wed, Aug 05, 2020 at 01:04:31AM +0300, Grygorii Strashko wrote:

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On 05/08/2020 00:44, Russell King - ARM Linux admin wrote:

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On Wed, Aug 05, 2020 at 12:34:47AM +0300, Grygorii Strashko wrote:

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On 05/08/2020 00:07, Russell King - ARM Linux admin wrote:

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On Tue, Aug 04, 2020 at 11:56:12PM +0300, Grygorii Strashko wrote:

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On 31/07/2020 13:06, Kurt Kanzenbach wrote:

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On Thu Jul 30 2020, Petr Machata wrote:

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Kurt Kanzenbach [off-list ref] writes:

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@@ -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.

However, that's likely to break everyone else.

For example, anyone calling this from the mii_timestamper rxtstamp()
method, the skb will have been classified with the MAC header pushed
and restored, so skb->data points at the network header.

Your change means that ptp_parse_header() expects the MAC header to
also be pushed.

Is it possible to adjust CPTS?

Looking at:
drivers/net/ethernet/ti/cpsw.c... yes.
drivers/net/ethernet/ti/cpsw_new.c... yes.
drivers/net/ethernet/ti/netcp_core.c... unclear.

If not, maybe cpts should remain unconverted - I don't see any reason
to provide a generic function for one user.

Could it be an option to pass "u8 *ptr" instead of "const struct sk_buff *skb" as
input parameter to ptp_parse_header()?

It needs to read from the buffer, and in order to do that, it needs to
validate that the buffer contains sufficient data.  So, at minimum it
needs to be a pointer and size of valid data.

I was thinking about suggesting that as a core function, with a wrapper
for the existing interface.

Then length can be added.

Actually, it needs more than that, because skb->data..skb->len already
may contain the eth header or may not.

quoted

Otherwise not only CPTS can't benefit from this new API, but also
drivers like oki-semi/pch_gbe/pch_gbe_main.c -> pch_ptp_match()

Again, this looks like it can be solved easily by swapping the position
of these two calls:

                        pch_rx_timestamp(adapter, skb);

                        skb->protocol = eth_type_trans(skb, netdev);

quoted

or have to two have two APIs (name?).

ptp_parse_header1(struct sk_buff *skb, unsigned int type)
{
	u8 *data = skb_mac_header(skb);

ptp_parse_header2(struct sk_buff *skb, unsigned int type)
{
	u8 *data = skb->data;

everything else is the same.

Actually, I really don't think we want 99% of users doing:

	hdr = ptp_parse_header(skb_mac_header(skb), skb->data, skb->len, type)

or

	hdr = ptp_parse_header(skb_mac_header(skb), skb->data + skb->len, type);

because that is what it will take, and this is starting to look
really very horrid.

True.

So, I repeat my question again: can netcp_core.c be adjusted to
ensure that the skb mac header field is correctly set by calling
eth_type_trans() prior to calling the rx hooks?  The other two
cpts cases look easy to change, and the oki-semi also looks the
same.

I think it's possible to adjust the netcp core. So, the time stamping is
done via

 gbe_rxhook() -> gbe_rxtstamp() -> cpts_rx_timestamp()

The hooks are called in netcp_process_one_rx_packet(). So, moving
eth_type_trans() before executing the hooks should work. Only one hook
is registered.

What do you think about it?

Thanks,
Kurt