virtio-net: Add LRO support for TCPv4 and TCPv6 segments

[damanm24]

This PR adds LRO support for our virtio-net device and makes the corresponding changes to the TAP and Consomme backends to take advantage of the new feature.

Burette tests showed ~75% improvement in TCP rx throughput with the TAP backend.
Consomme showed a ~37% reduction in CPU usage while maintaining similar rx throughput. Through further experimentation, the throughput improvements here are bounded by Tcp::ConnectionParams::tx_buffer_size (i.e. increasing this parameter (to 512 kb) showed same level of improvement as the TAP backend)

[Copilot]

Pull request overview

This PR introduces receive-side LRO/GSO plumbing for virtio-net by propagating coalesced-packet metadata from network backends (TAP and Consomme) through net_backend::RxMetadata into the virtio-net header (GUEST_TSO4/6).

Changes:

• Advertise VIRTIO_NET_F_GUEST_TSO4/6 and plumb negotiated guest TSO features into virtio-net RX buffer handling.
• Extend net_backend::RxMetadata with L3/L2/L3/L4 header length + GSO size fields and populate them in TAP and Consomme RX paths.
• Update Consomme TCP send path to optionally emit larger-than-MSS frames with TSO metadata.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
vm/devices/virtio/virtio_net/src/lib.rs	Advertises guest TSO4/6 and passes negotiated features into RX work-pool setup.
vm/devices/virtio/virtio_net/src/buffers.rs	Builds virtio-net RX headers with GSO fields derived from backend-provided metadata.
vm/devices/net/net_tap/src/lib.rs	Enables TAP RX offloads and parses vnet headers into new RX GSO metadata fields.
vm/devices/net/net_consomme/src/lib.rs	Populates new RX GSO metadata (L3 + header lens + MSS) for packets received from Consomme.
vm/devices/net/net_consomme/consomme/src/tcp.rs	Adds ability to emit larger TCP frames flagged as TSO/LRO to downstream client.
vm/devices/net/net_backend/src/lib.rs	Extends RxMetadata with GSO/LRO-related fields and defaults.

[github-actions]

1 Petri tests failed (1 unstable)

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 6 comments.