[xdp-hints] Re: [PATCH bpf-next V1 3/5] igc: add XDP hints kfuncs for RX timestamp

["Song, Yoong Siang" <yoong.siang.song@intel.com>]

On Monday, April 17, 2023 10:57 PM, Jesper Dangaard Brouer <brouer@redhat.com> wrote:
>The NIC hardware RX timestamping mechanism adds an optional tailored header
>before the MAC header containing packet reception time. Optional depending on
>RX descriptor TSIP status bit (IGC_RXDADV_STAT_TSIP). In case this bit is set
>driver does offset adjustments to packet data start and extracts the timestamp.
>
>The timestamp need to be extracted before invoking the XDP bpf_prog, because
>this area just before the packet is also accessible by XDP via data_meta context
>pointer (and helper bpf_xdp_adjust_meta). Thus, an XDP bpf_prog can potentially
>overwrite this and corrupt data that we want to extract with the new kfunc for
>reading the timestamp.
>
>Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
>---
> drivers/net/ethernet/intel/igc/igc.h      |    1 +
> drivers/net/ethernet/intel/igc/igc_main.c |   20 ++++++++++++++++++++
> 2 files changed, 21 insertions(+)
>
>diff --git a/drivers/net/ethernet/intel/igc/igc.h
>b/drivers/net/ethernet/intel/igc/igc.h
>index c609a2e648f8..18d4af934d8c 100644
>--- a/drivers/net/ethernet/intel/igc/igc.h
>+++ b/drivers/net/ethernet/intel/igc/igc.h
>@@ -503,6 +503,7 @@ struct igc_rx_buffer {  struct igc_xdp_buff {
> 	struct xdp_buff xdp;
> 	union igc_adv_rx_desc *rx_desc;
>+	ktime_t rx_ts; /* data indication bit IGC_RXDADV_STAT_TSIP */
> };
>
> struct igc_q_vector {
>diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
>b/drivers/net/ethernet/intel/igc/igc_main.c
>index 3a844cf5be3f..862768d5d134 100644
>--- a/drivers/net/ethernet/intel/igc/igc_main.c
>+++ b/drivers/net/ethernet/intel/igc/igc_main.c
>@@ -2552,6 +2552,7 @@ static int igc_clean_rx_irq(struct igc_q_vector *q_vector, const int budget)
> 		if (igc_test_staterr(rx_desc, IGC_RXDADV_STAT_TSIP)) {
> 			timestamp = igc_ptp_rx_pktstamp(q_vector->adapter,
> 							pktbuf);
>+			ctx.rx_ts = timestamp;
> 			pkt_offset = IGC_TS_HDR_LEN;
> 			size -= IGC_TS_HDR_LEN;
> 		}
>@@ -2740,6 +2741,7 @@ static int igc_clean_rx_irq_zc(struct igc_q_vector *q_vector, const int budget)
> 		if (igc_test_staterr(desc, IGC_RXDADV_STAT_TSIP)) {
> 			timestamp = igc_ptp_rx_pktstamp(q_vector->adapter,
> 							bi->xdp->data);
>+			ctx->rx_ts = timestamp;
>
> 			bi->xdp->data += IGC_TS_HDR_LEN;
>
>@@ -6492,6 +6494,23 @@ u32 igc_rd32(struct igc_hw *hw, u32 reg)
> 	return value;
> }
>
>+static int igc_xdp_rx_timestamp(const struct xdp_md *_ctx, u64 *timestamp) {
>+	const struct igc_xdp_buff *ctx = (void *)_ctx;
>+
>+	if (igc_test_staterr(ctx->rx_desc, IGC_RXDADV_STAT_TSIP)) {
>+		*timestamp = ctx->rx_ts;
>+
>+		return 0;
>+	}
>+
>+	return -ENODATA;
>+}
>+
>+const struct xdp_metadata_ops igc_xdp_metadata_ops = {

Since igc_xdp_metadata_ops is used in igc_main.c only, suggest to make it static.

Thanks & Regards
Siang

>+	.xmo_rx_timestamp		= igc_xdp_rx_timestamp,
>+};
>+
> /**
>  * igc_probe - Device Initialization Routine
>  * @pdev: PCI device information struct
>@@ -6565,6 +6584,7 @@ static int igc_probe(struct pci_dev *pdev,
> 	hw->hw_addr = adapter->io_addr;
>
> 	netdev->netdev_ops = &igc_netdev_ops;
>+	netdev->xdp_metadata_ops = &igc_xdp_metadata_ops;
> 	igc_ethtool_set_ops(netdev);
> 	netdev->watchdog_timeo = 5 * HZ;
>
>