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Fix Firecracker VM networking: correct ip_forward + /30 prefix #86

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Fix Firecracker VM networking: correct ip_forward + /30 prefix #86

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7 changes: 5 additions & 2 deletions src/nightshift/vm/network.py
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Original file line number Diff line number Diff line change
Expand Up @@ -95,11 +95,14 @@ async def create_tap(vm_id: str) -> TapConfig:
tap_name = f"tap-{vm_id[:8]}"
host_ip = f"172.16.{vm_index}.1"
guest_ip = f"172.16.{vm_index}.2"
mask = "255.255.255.252" # /30 in dotted decimal for kernel ip= boot arg
# Keep dotted netmask for Firecracker kernel boot arg ip=... (see vm/manager.py).
mask = "255.255.255.252"
# iproute2 expects prefix length notation, not dotted netmask.
prefix_len = "30"

# Create TAP device
await _run(f"ip tuntap add dev {tap_name} mode tap")
await _run(f"ip addr add {host_ip}/{mask} dev {tap_name}")
await _run(f"ip addr add {host_ip}/{prefix_len} dev {tap_name}")
await _run(f"ip link set {tap_name} up")

# Enable IP forwarding
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