Michael S. Tsirkin wrote:

On Sun, Feb 01, 2026 at 04:05:54PM -0500, Willem de Bruijn wrote:

quoted

Steffen Trumtrar wrote:

quoted

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 need
to be 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.

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>

quoted

quoted

@@ -475,6 +478,8 @@ struct virtnet_info {
 
 	struct control_buf *ctrl;
 
+	struct kernel_hwtstamp_config tstamp_config;
+
 	/* Ethtool settings */
 	u8 duplex;
 	u32 speed;

@@ -511,6 +516,7 @@ struct virtio_net_common_hdr {
 		struct virtio_net_hdr_mrg_rxbuf	mrg_hdr;
 		struct virtio_net_hdr_v1_hash hash_v1_hdr;
 		struct virtio_net_hdr_v1_hash_tunnel tnl_hdr;
+		struct virtio_net_hdr_v1_hash_tunnel_ts ts_hdr;

Jason, Michael: creating a new struct for every field is not very
elegant. Is it time to find a more forward looking approach to
expanding with new fields? Like a TLV, or how netlink structs like
tcp_info are extended with support for legacy users that only use
a truncated struct?

I certainly wouldn't mind, though I suspect tlv is too complex as
hardware implementations can't efficiently follow linked lists.  I'll
try to ping some hardware designers for what works well for offloads.

Great thanks.

Agreed that TLV was probably the wrong suggestion.

We can definitely have a required order of fields. My initial thought
is as said like many user/kernel structures: where both sides agree on
the basic order of the struct, and pass along the length, so that they
agree only to process the min of both their supported lengths. New
fields are added at the tail of the struct. See for instance getsockopt
TCP_INFO.