virtio

Documentation

Overview

Package virtio contains some generic types and concepts related to the virtio protocol.

Index

• Constants
• Variables
• type Feature
• type NetHdr
  • func (v *NetHdr) Decode(data []byte) error
  • func (v *NetHdr) Encode(data []byte) error

Constants

const NetHdrSize = 12

NetHdrSize is the number of bytes needed to store a NetHdr in memory.

Variables

var ErrNetHdrBufferTooSmall = errors.New("the buffer is too small to fit a virtio_net_hdr")

ErrNetHdrBufferTooSmall is returned when a buffer is too small to fit a virtio_net_hdr.

Types

type Feature

type Feature uint64

Feature contains feature bits that describe a virtio device or driver.

const (
	// FeatureIndirectDescriptors indicates that the driver can use descriptors
	// with an additional layer of indirection.
	FeatureIndirectDescriptors Feature = 1 << 28

	// FeatureVersion1 indicates compliance with version 1.0 of the virtio
	// specification.
	FeatureVersion1 Feature = 1 << 32
)

Device-independent feature bits.

Source: https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-6600006

const (
	// FeatureNetDeviceCsum indicates that the device can handle packets with
	// partial checksum (checksum offload).
	FeatureNetDeviceCsum Feature = 1 << 0

	// FeatureNetDriverCsum indicates that the driver can handle packets with
	// partial checksum.
	FeatureNetDriverCsum Feature = 1 << 1

	// FeatureNetCtrlDriverOffloads indicates support for dynamic offload state
	// reconfiguration.
	FeatureNetCtrlDriverOffloads Feature = 1 << 2

	// FeatureNetMTU indicates that the device reports a maximum MTU value.
	FeatureNetMTU Feature = 1 << 3

	// FeatureNetMAC indicates that the device provides a MAC address.
	FeatureNetMAC Feature = 1 << 5

	// FeatureNetDriverTSO4 indicates that the driver supports the TCP
	// segmentation offload for received IPv4 packets.
	FeatureNetDriverTSO4 Feature = 1 << 7

	// FeatureNetDriverTSO6 indicates that the driver supports the TCP
	// segmentation offload for received IPv6 packets.
	FeatureNetDriverTSO6 Feature = 1 << 8

	// FeatureNetDriverECN indicates that the driver supports the TCP
	// segmentation offload with ECN for received packets.
	FeatureNetDriverECN Feature = 1 << 9

	// FeatureNetDriverUFO indicates that the driver supports the UDP
	// fragmentation offload for received packets.
	FeatureNetDriverUFO Feature = 1 << 10

	// FeatureNetDeviceTSO4 indicates that the device supports the TCP
	// segmentation offload for received IPv4 packets.
	FeatureNetDeviceTSO4 Feature = 1 << 11

	// FeatureNetDeviceTSO6 indicates that the device supports the TCP
	// segmentation offload for received IPv6 packets.
	FeatureNetDeviceTSO6 Feature = 1 << 12

	// FeatureNetDeviceECN indicates that the device supports the TCP
	// segmentation offload with ECN for received packets.
	FeatureNetDeviceECN Feature = 1 << 13

	// FeatureNetDeviceUFO indicates that the device supports the UDP
	// fragmentation offload for received packets.
	FeatureNetDeviceUFO Feature = 1 << 14

	// FeatureNetMergeRXBuffers indicates that the driver can handle merged
	// receive buffers.
	// When this feature is negotiated, devices may merge multiple descriptor
	// chains together to transport large received packets. [NetHdr.NumBuffers]
	// will then contain the number of merged descriptor chains.
	FeatureNetMergeRXBuffers Feature = 1 << 15

	// FeatureNetStatus indicates that the device configuration status field is
	// available.
	FeatureNetStatus Feature = 1 << 16

	// FeatureNetCtrlVQ indicates that a control channel virtqueue is
	// available.
	FeatureNetCtrlVQ Feature = 1 << 17

	// FeatureNetCtrlRX indicates support for RX mode control (e.g. promiscuous
	// or all-multicast) for packet receive filtering.
	FeatureNetCtrlRX Feature = 1 << 18

	// FeatureNetCtrlVLAN indicates support for VLAN filtering through the
	// control channel.
	FeatureNetCtrlVLAN Feature = 1 << 19

	// FeatureNetDriverAnnounce indicates that the driver can send gratuitous
	// packets.
	FeatureNetDriverAnnounce Feature = 1 << 21

	// FeatureNetMQ indicates that the device supports multiqueue with automatic
	// receive steering.
	FeatureNetMQ Feature = 1 << 22

	// FeatureNetCtrlMACAddr indicates that the MAC address can be set through
	// the control channel.
	FeatureNetCtrlMACAddr Feature = 1 << 23

	// FeatureNetDeviceUSO indicates that the device supports the UDP
	// segmentation offload for received packets.
	FeatureNetDeviceUSO Feature = 1 << 56

	// FeatureNetHashReport indicates that the device can report a per-packet
	// hash value and type.
	FeatureNetHashReport Feature = 1 << 57

	// FeatureNetDriverHdrLen indicates that the driver can provide the exact
	// header length value (see [NetHdr.HdrLen]).
	// Devices may benefit from knowing the exact header length.
	FeatureNetDriverHdrLen Feature = 1 << 59

	// FeatureNetRSS indicates that the device supports RSS (receive-side
	// scaling) with configurable hash parameters.
	FeatureNetRSS Feature = 1 << 60

	// FeatureNetRSCExt indicates that the device can process duplicated ACKs
	// and report the number of coalesced segments and duplicated ACKs.
	FeatureNetRSCExt Feature = 1 << 61

	// FeatureNetStandby indicates that the device may act as a standby for a
	// primary device with the same MAC address.
	FeatureNetStandby Feature = 1 << 62

	// FeatureNetSpeedDuplex indicates that the device can report link speed and
	// duplex mode.
	FeatureNetSpeedDuplex Feature = 1 << 63
)

Feature bits for networking devices.

Source: https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html#x1-2200003

type NetHdr

type NetHdr struct {
	// Flags that describe the packet.
	// Possible values are:
	//   - [unix.VIRTIO_NET_HDR_F_NEEDS_CSUM]
	//   - [unix.VIRTIO_NET_HDR_F_DATA_VALID]
	//   - [unix.VIRTIO_NET_HDR_F_RSC_INFO]
	Flags uint8
	// GSOType contains the type of segmentation offload that should be used for
	// the packet.
	// Possible values are:
	//   - [unix.VIRTIO_NET_HDR_GSO_NONE]
	//   - [unix.VIRTIO_NET_HDR_GSO_TCPV4]
	//   - [unix.VIRTIO_NET_HDR_GSO_UDP]
	//   - [unix.VIRTIO_NET_HDR_GSO_TCPV6]
	//   - [unix.VIRTIO_NET_HDR_GSO_UDP_L4]
	//   - [unix.VIRTIO_NET_HDR_GSO_ECN]
	GSOType uint8
	// HdrLen contains the length of the headers that need to be replicated by
	// segmentation offloads. It's the number of bytes from the beginning of the
	// packet to the beginning of the transport payload.
	// Only used when [FeatureNetDriverHdrLen] is negotiated.
	HdrLen uint16
	// GSOSize contains the maximum size of each segmented packet beyond the
	// header (payload size). In case of TCP, this is the MSS.
	GSOSize uint16
	// CsumStart contains the offset within the packet from which on the
	// checksum should be computed.
	CsumStart uint16
	// CsumOffset specifies how many bytes after [NetHdr.CsumStart] the computed
	// 16-bit checksum should be inserted.
	CsumOffset uint16
	// NumBuffers contains the number of merged descriptor chains when
	// [FeatureNetMergeRXBuffers] is negotiated.
	// This field is only used for packets received by the driver and should be
	// zero for transmitted packets.
	NumBuffers uint16
}

NetHdr defines the virtio_net_hdr as described by the virtio specification.

func (*NetHdr) Decode

func (v *NetHdr) Decode(data []byte) error

Decode decodes the NetHdr from the given byte slice. The slice must contain at least NetHdrSize bytes.

func (*NetHdr) Encode

func (v *NetHdr) Encode(data []byte) error

Encode encodes the NetHdr into the given byte slice. The slice must have room for at least NetHdrSize bytes.