Re: [PATCH RFC v3 1/2] virtio-net: support receive timestamp

Add optional hardware rx timestamp offload for virtio-net.

Introduce virtio feature VIRTIO_NET_F_TSTAMP. If negotiated, the
virtio-net header is expanded with room for a timestamp.

To get and set the hwtstamp the functions ndo_hwtstamp_set/get are
implemented. This allows filtering the packets and only time stamp
the packets where the filter matches. This way, the timestamping can
be en/disabled at runtime.
Currently, timestamping is handled the same for all supported filters and
therefore handled the same for all received packets.

XDP packets are not supported and timestamping is skipped for the XDP path.

Tested:
  guest: ./timestamping eth0 \
          SOF_TIMESTAMPING_RAW_HARDWARE \
          SOF_TIMESTAMPING_RX_HARDWARE
  host: nc -4 -u 192.168.1.1 319

Signed-off-by: Steffen Trumtrar <redacted>

--
  Changes to v2:
  - update filter handling
  - move tstamp into virtio_net_common_hdr
  - remove new struct virtio_net_hdr_v1_hash_tunnel_ts
  Changes to v1:
  - rework series to use flow filters
  - add new struct virtio_net_hdr_v1_hash_tunnel_ts
  - original work done by: Willem de Bruijn [off-list ref]
---
 drivers/net/virtio_net.c        | 127 +++++++++++++++++++++++++++++++++++++++-
 include/uapi/linux/virtio_net.h |   1 +
 2 files changed, 126 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index e34c52d059d39..ef6238cb336b9 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -416,6 +416,12 @@ struct virtnet_info {
 	u32 rss_hash_types_supported;
 	u32 rss_hash_types_saved;
 
+	/* Device passes time stamps to the driver */
+	bool has_tstamp;
+	bool hwts_rx_en;
+
+	struct kernel_hwtstamp_config tstamp_config;
+
 	/* Has control virtqueue */
 	bool has_cvq;
 

@@ -499,6 +505,8 @@ struct virtio_net_common_hdr {
 		struct virtio_net_hdr_v1_hash hash_v1_hdr;
 		struct virtio_net_hdr_v1_hash_tunnel tnl_hdr;
 	};
+
+	__le16 tstamp[4];	/* 64-bit timestamp, 2-byte aligned */
 };