IEEE 1588 Proper way of getting transmitted time stamps

[r315]

I'm trying to port a ptp library (ptp master) to a STM32F769 device on a stm32f769i-disco development board.
Started with ethernetif.c from LwIP example, changed link_output function to call HAL_ETH_PTP_InsertTxTimestamp before HAL_ETH_Transmit_IT, this instructs ETH_DMA to perform time stamping.

After packet being transmitted, HAL_ETH_PTP_GetTxTimestamp is called and the obtained timestamp is passed to ptp library which then use it for FollowUp message.

Using wireshark I'm observing that the FollowUp messages contain timestamp from previous Sync message and not the last one. This looks like as if the tx descriptors index is off by one. I have confirmed that PTP is correctly configured with HAL_ETH_PTP_SetConfig and time set correctly.

The question is what is the proper sequence to transmit and get timestamp or if is there any example with ptp from ST?

I have figure it out, however HAL_ETH_PTP_GetTxTimestamp seams to have a bug, since it is returning time stamp from
dmatxdesc->DESC0 and dmatxdesc->DESC1 intead of dmatxdesc->DESC6 and dmatxdesc->DESC7.