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vm networking: add flag vnet_hdr #78

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vm networking: add flag vnet_hdr #78

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2 changes: 2 additions & 0 deletions docs/vm-networking.md
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,8 @@ that take the following fields:
VFKIT magic sequence after connecting to the `socket`. Accept any of `1, t, T,
TRUE, true, True, 0, f, F, FALSE, false, False`. Any other value is invalid and
will produce an error.
- `vnet_hdr` (optional, defaults to false): Indicate whether the VMM includes
virtio-net headers along with Ethernet frames.

Note that the first network specified will be used as the default gateway.

Expand Down
18 changes: 17 additions & 1 deletion internal/shim/task/networking_unix.go
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Expand Up @@ -30,6 +30,11 @@ import (
"github.com/containerd/nerdbox/internal/vm"
)

const (
NET_FLAG_VFKIT = 1 << iota // See https://github.com/containers/libkrun/blob/357ec63fee444b973e4fc76d2121fd41631f121e/include/libkrun.h#L271C9-L271C23
NET_FLAG_INCLUDE_VNET_HEADER
)

type networksProvider struct {
nws []network
}
Expand All @@ -43,6 +48,7 @@ type network struct {
addr6 netip.Prefix // addr6 is the IPv6 address + subnet mask of the network interface
features uint32 // features is a bitmask of virtio-net features enabled on this network endpoint
vfkit bool // vfkit is a boolean flag indicating whether libkrun must send the VFKIT magic sequence after connecting to the socket.
vnetHdr bool // vnetHdr is a boolean flag indicating whether libkrun must include virtio-net headers along with Ethernet frames.
}

const (
Expand All @@ -57,6 +63,7 @@ const (
addrField = "addr"
featuresField = "features" // features is a bitwise-OR separated list of virtio-net features. See https://docs.oasis-open.org/virtio/virtio/v1.3/csd01/virtio-v1.3-csd01.html#x1-2370003
vfkitField = "vfkit" // vfkit is a boolean flag indicating whether libkrun must send the VFKIT magic sequence after connecting to the socket.
vnetHdrField = "vnet_hdr"

nwModeUnixgram = "unixgram"
nwModeUnixstream = "unixstream"
Expand Down Expand Up @@ -149,6 +156,12 @@ func parseNetwork(annotation string) (network, error) {
return network{}, fmt.Errorf("parsing vfkit field: %w", err)
}
n.vfkit = vfkit
case vnetHdrField:
vnetHdr, err := strconv.ParseBool(value)
if err != nil {
return network{}, fmt.Errorf("parsing vnet_hdr field: %w", err)
}
n.vnetHdr = vnetHdr
default:
return network{}, fmt.Errorf("unknown network field: %s", key)
}
Expand Down Expand Up @@ -180,7 +193,10 @@ func (p *networksProvider) SetupVM(ctx context.Context, vmi vm.Instance) error {

var flags uint32
if nw.vfkit {
flags = 1 // See https://github.com/containers/libkrun/blob/357ec63fee444b973e4fc76d2121fd41631f121e/include/libkrun.h#L271C9-L271C23
flags = NET_FLAG_VFKIT
}
if nw.vnetHdr {
flags |= NET_FLAG_INCLUDE_VNET_HEADER
}

if err := vmi.AddNIC(ctx, nw.endpoint, nw.mac, nwMode, nw.features, flags); err != nil {
Expand Down