igc: Add XDP hints kfuncs for RX timestamp

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>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Yoong Siang <yoong.siang.song@intel.com>
Link: https://lore.kernel.org/bpf/168182465791.616355.2583922957423587914.stgit@firesoul

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 {

drivers/net/ethernet/intel/igc/igc_main.c

@@ -2549,6 +2549,7 @@ 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;
 		}
@@ -2737,6 +2738,7 @@ 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;
 
@@ -6523,8 +6525,22 @@ static int igc_xdp_rx_hash(const struct xdp_md *_ctx, u32 *hash,
 	return 0;
 }
 
+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;
+}
+
 static const struct xdp_metadata_ops igc_xdp_metadata_ops = {
 	.xmo_rx_hash			= igc_xdp_rx_hash,
+	.xmo_rx_timestamp		= igc_xdp_rx_timestamp,
 };
 
 /**