From: Christian Eggers <[email protected]>
For P2P delay measurement, the ingress time stamp of the PDelay_Req is
required for the correction field of the PDelay_Resp. The application
echoes back the correction field of the PDelay_Req when sending the
PDelay_Resp.
Some hardware (like the ZHAW InES PTP time stamping IP core) subtracts
the ingress timestamp autonomously from the correction field, so that
the hardware only needs to add the egress timestamp on tx. Other
hardware (like the Microchip KSZ9563) reports the ingress time stamp via
an interrupt and requires that the software provides this time stamp via
tail-tag on tx.
In order to avoid introducing a further application interface for this,
the driver can simply emulate the behavior of the InES device and
subtract the ingress time stamp in software from the correction field.
On egress, the correction field can either be kept as it is (and the
time stamp field in the tail-tag is set to zero) or move the value from
the correction field back to the tail-tag.
Changing the correction field requires updating the UDP checksum (if UDP
is used as transport).
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Christian Eggers <[email protected]>
---
v1 -> v2
- Fixed compilation issue when PTP_CLASSIFY not selected in menuconfig
---
include/linux/ptp_classify.h | 71 ++++++++++++++++++++++++++++++++++++
1 file changed, 71 insertions(+)
diff --git a/include/linux/ptp_classify.h b/include/linux/ptp_classify.h
index 2b6ea36ad162..6e5869c2504c 100644
--- a/include/linux/ptp_classify.h
+++ b/include/linux/ptp_classify.h
@@ -10,8 +10,12 @@
#ifndef _PTP_CLASSIFY_H_
#define _PTP_CLASSIFY_H_
+#include <asm/unaligned.h>
#include <linux/ip.h>
+#include <linux/ktime.h>
#include <linux/skbuff.h>
+#include <linux/udp.h>
+#include <net/checksum.h>
#define PTP_CLASS_NONE 0x00 /* not a PTP event message */
#define PTP_CLASS_V1 0x01 /* protocol version 1 */
@@ -129,6 +133,67 @@ static inline u8 ptp_get_msgtype(const struct ptp_header *hdr,
return msgtype;
}
+/**
+ * ptp_check_diff8 - Computes new checksum (when altering a 64-bit field)
+ * @old: old field value
+ * @new: new field value
+ * @oldsum: previous checksum
+ *
+ * This function can be used to calculate a new checksum when only a single
+ * field is changed. Similar as ip_vs_check_diff*() in ip_vs.h.
+ *
+ * Return: Updated checksum
+ */
+static inline __wsum ptp_check_diff8(__be64 old, __be64 new, __wsum oldsum)
+{
+ __be64 diff[2] = { ~old, new };
+
+ return csum_partial(diff, sizeof(diff), oldsum);
+}
+
+/**
+ * ptp_header_update_correction - Update PTP header's correction field
+ * @skb: packet buffer
+ * @type: type of the packet (see ptp_classify_raw())
+ * @hdr: ptp header
+ * @correction: new correction value
+ *
+ * This updates the correction field of a PTP header and updates the UDP
+ * checksum (if UDP is used as transport). It is needed for hardware capable of
+ * one-step P2P that does not already modify the correction field of Pdelay_Req
+ * event messages on ingress.
+ */
+static inline
+void ptp_header_update_correction(struct sk_buff *skb, unsigned int type,
+ struct ptp_header *hdr, s64 correction)
+{
+ __be64 correction_old;
+ struct udphdr *uhdr;
+
+ /* previous correction value is required for checksum update. */
+ memcpy(&correction_old, &hdr->correction, sizeof(correction_old));
+
+ /* write new correction value */
+ put_unaligned_be64((u64)correction, &hdr->correction);
+
+ switch (type & PTP_CLASS_PMASK) {
+ case PTP_CLASS_IPV4:
+ case PTP_CLASS_IPV6:
+ /* locate udp header */
+ uhdr = (struct udphdr *)((char *)hdr - sizeof(struct udphdr));
+ break;
+ default:
+ return;
+ }
+
+ /* update checksum */
+ uhdr->check = csum_fold(ptp_check_diff8(correction_old,
+ hdr->correction,
+ ~csum_unfold(uhdr->check)));
+ if (!uhdr->check)
+ uhdr->check = CSUM_MANGLED_0;
+}
+
/**
* ptp_msg_is_sync - Evaluates whether the given skb is a PTP Sync message
* @skb: packet buffer
@@ -166,5 +231,11 @@ static inline bool ptp_msg_is_sync(struct sk_buff *skb, unsigned int type)
{
return false;
}
+
+static inline
+void ptp_header_update_correction(struct sk_buff *skb, unsigned int type,
+ struct ptp_header *hdr, s64 correction)
+{
+}
#endif
#endif /* _PTP_CLASSIFY_H_ */
--
2.36.1
On Tue, Dec 06, 2022 at 02:44:21PM +0530, Arun Ramadoss wrote:
> From: Christian Eggers <[email protected]>
>
> For P2P delay measurement, the ingress time stamp of the PDelay_Req is
> required for the correction field of the PDelay_Resp. The application
> echoes back the correction field of the PDelay_Req when sending the
> PDelay_Resp.
>
> Some hardware (like the ZHAW InES PTP time stamping IP core) subtracts
> the ingress timestamp autonomously from the correction field, so that
> the hardware only needs to add the egress timestamp on tx. Other
> hardware (like the Microchip KSZ9563) reports the ingress time stamp via
> an interrupt and requires that the software provides this time stamp via
> tail-tag on tx.
>
> In order to avoid introducing a further application interface for this,
> the driver can simply emulate the behavior of the InES device and
> subtract the ingress time stamp in software from the correction field.
>
> On egress, the correction field can either be kept as it is (and the
> time stamp field in the tail-tag is set to zero) or move the value from
> the correction field back to the tail-tag.
>
> Changing the correction field requires updating the UDP checksum (if UDP
> is used as transport).
>
> Reported-by: kernel test robot <[email protected]>
How can a test robot report new code additions?
Thanks,
Richard
Hi Richard,
On Tue, 2022-12-06 at 08:38 -0800, Richard Cochran wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
>
> On Tue, Dec 06, 2022 at 02:44:21PM +0530, Arun Ramadoss wrote:
> > From: Christian Eggers <[email protected]>
> >
> >
> > Reported-by: kernel test robot <[email protected]>
>
> How can a test robot report new code additions?
Test robot ran the compilation test for the patch v1 and found
compilation error when CONFIG_NET_PTP_CLASSIFY is not enabled. It is
due to mismatch in function name defined in with and without
PTP_CLASSIFY enabled.
https://lore.kernel.org/netdev/[email protected]/
In the message, it is mentioned like
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <[email protected]>
I initially thought reported-by tag needs to added only for the bug fix
patch. I was in confusion where to add the tag whether in commit
description or in the patch revision message.
Kindly suggest on where to add tag, before signed-off or in the patch
revision list.
Thanks
Arun
>
> Thanks,
> Richard
On Wed, Dec 07, 2022 at 04:15:04AM +0000, [email protected] wrote:
> Kindly suggest on where to add tag, before signed-off or in the patch
> revision list.
Nowhere. Just do it if you fix a problem using the robot for a patch
that has already been merged.