Networking

Volant supports three network modes declared in the plugin manifest (internal/pluginspec/spec.go) and overridable per-VM via vmconfig.Config.

Modes

• vsock

  • No IP networking; host↔guest comms via virtio-vsock only
  • Orchestrator: no tap created; no IP allocated
  • Launcher: configures --vsock cid=

• bridged

  • Host-managed Linux bridge (vbr0) with a per-VM tap device
  • Orchestrator: allocates IP and prepares tap; attaches tap to bridge
  • Launcher: configures --net tap=,mac=,ip=,mask=

• dhcp

  • Similar to bridged, but guest obtains IP via DHCP
  • Orchestrator: prepares tap; no host IP allocation
  • Launcher: configures --net tap=,mac= (no ip/mask)

Bridge/Tap Provisioning

• Code: internal/server/orchestrator/network/bridge.go (linux)
  • Creates tuntap device with TUNTAP_VNET_HDR and attaches it to the bridge
  • Naming: vttap-, constrained to IFNAMSIZ 15 chars
• Non-Linux builds use a noop manager (bridge_stub.go → NewNoop())

Setup Script

• Code: internal/setup/setup.go
  • Creates bridge vbr0, assigns host CIDR, brings it up
  • Enables IP forwarding and sets NAT masquerade for the subnet

Decision Logic (when to create taps, allocate IPs)

• Tested in internal/server/orchestrator/network_test.go
• needsTapDevice(cfg): true for bridged/dhcp; false for vsock; default true if cfg nil/empty
• needsIPAllocation(cfg): true for bridged; false for dhcp/vsock; default true if cfg nil/empty