AkihiroSuda / lima-vm-vde_vmnet

vmnet.framework support for rootless QEMU (without patching QEMU)

vde_vmnet: vmnet.framework support for rootless QEMU

vde_vmnet provides vmnet.framework support for VDE applications such as QEMU.

vde_vmnet does not require QEMU to run as the root user.

(But vde_vmnet itself has to run as the root, in most cases.)

Install

Requires macOS 10.15 or later.

brew install vde

make

sudo make install

The following files will be installed:

• /usr/local/bin/vde_vmnet
• /Library/LaunchDaemons/io.github.virtualsquare.vde-2.vde_switch.plist
• /Library/LaunchDaemons/io.github.AkihiroSuda.vde_vmnet.plist
  • Configured to use 192.168.105.0/24. Modifiy the file if it conflicts with your local network.

See "Testing without launchd" if you don't prefer to use launchd.

Usage

qemu-system-x86_64 \
  -device virtio-net-pci,netdev=net0 -netdev vde,id=net0,sock=/var/run/vde.ctl \
  -m 4096 -accel hvf -cdrom ubuntu-21.04-desktop-amd64.iso

The guest IP is assigned by the DHCP server provided by macOS.

The guest is accessible to the internet, and the guest IP is accessible from the host.

To confirm, run sudo apt-get update && sudo apt-get install -y apache2 in the guest, and access the guest IP via Safari on the host.

Multi VM

Multiple VMs can be connected to a single vde_vmnet instance.

Make sure to specify unique MAC addresses to VMs: -device virtio-net-pci,netdev=net0,mac=de:ad:be:ef:00:01 .

NOTE: don't confuse MAC addresses of VMs with the MAC address of vde_vmnet itself that is printed as vmnet_mac_address in the debug log. You do not need to configure (and you can't, currently) the MAC address of vde_vmnet itself.

Bridged mode

Run sudo make install BRIDGED=en0.

The following additional files will be installed:

• /Library/LaunchDaemons/io.github.virtualsquare.vde-2.vde_switch.bridged.en0.plist
• /Library/LaunchDaemons/io.github.AkihiroSuda.vde_vmnet.bridged.en0.plist

Use /var/run/vde.bridged.en0.ctl as the VDE socket path.

Advanced usage

Testing without launchd

make

make install.bin

vde_switch --unix /tmp/vde.ctl

sudo vde_vmnet --vmnet-gateway=192.168.105.1 /tmp/vde.ctl

Note: make sure to run vde_vmnet with root (sudo). See FAQs for the reason. vde_switch does not need to be executed as root.

PTP mode (Switchless mode)

• Pros: doesn't require the vde_switch process to be running
• Cons: no support for multi-VM

To enable PTP mode, append [] to the socket path argument of vde_vmnet.

sudo vde_vmnet /tmp/vde.ptp[]

QEMU has to be launched with port=65535 without [].

qemu-system-x86_64 -netdev vde,id=net0,sock=/tmp/vde.ptp,port=65535 ...

The "port" number here has nothing to do with TCP/UDP ports.

FAQs

Why does vde_vmnet require root?

Running vde_vmnet without root could be possible by signing the vde_vmnet binary with com.apple.vm.networking entitlement.

However, signing a binary with com.apple.vm.networking entitlement seems to require some contract with Apple. :disappointed:

This entitlement is restricted to developers of virtualization software. To request this entitlement, contact your Apple representative.

https://developer.apple.com/documentation/bundleresources/entitlements/com_apple_vm_networking

Is it possible to run vde_vmnet with SETUID?

Discouraged, as it allows non-root users to write arbitrary files, by specifying certain CLI args and environment variables.

Instead, consider using launchd or sudo.

See ./etc_sudoers.d/vde_vmnet to allow running sudo vde_vmnet with reduced set of args and environment variables.

How is vde_vmnet related to QEMU-builtin vmnet support?

There are proposal to add builtin vmnet support for QEMU:

• https://lore.kernel.org/qemu-devel/[e-mail]/
• https://lore.kernel.org/qemu-devel/[e-mail]/

However, QEMU-builtin vmnet is highly likely to require running the entire QEMU process as root.

On the other hand, vde_vmnet does not require the entire QEMU process to run as root, though vde_vmnet has to run as root.

How to use static IP addresses?

When --vmnet-gateway=IP is set to "192.168.105.1", the whole subnet (192.168.105.2-192.168.105.254) is used as the DHCP range.

To use static IP addresses, limit the DHCP range with --vmnet-dhcp-end=IP.

For example, --vmnet-gateway=192.168.105.1 --vmnet-dhcp-end=192.168.105.100 allows using 192.168.105.101-192.168.105.254 as non-DHCP static addresses.

How to reserve DHCP addresses?

• Decide a unique MAC address for the VM, e.g. de:ad:be:ef:00:01.

• Decide a reserved IP address, e.g., "192.168.105.100"

• Create /etc/bootptab like this. Make sure not to drop the "%%" header.

# bootptab
%%
# hostname      hwtype  hwaddr              ipaddr          bootfile
tmp-vm01        1       de:ad:be:ef:00:01   192.168.105.100

• Reload the DHCP daemon.

sudo /bin/launchctl unload -w /System/Library/LaunchDaemons/bootps.plist
sudo /bin/launchctl load -w /System/Library/LaunchDaemons/bootps.plist

• Run QEMU with the MAC address: -device virtio-net-pci,netdev=net0,mac=de:ad:be:ef:00:01 .

NOTE: don't confuse MAC addresses of VMs with the MAC address of vde_vmnet itself that is printed as vmnet_mac_address in the debug log. You do not need to configure (and you can't, currently) the MAC address of vde_vmnet itself.

Links

• https://developer.apple.com/documentation/vmnet
• https://developer.apple.com/documentation/bundleresources/entitlements/com_apple_vm_networking
• file:///Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks/vmnet.framework/Versions/Current/Headers/vmnet.h

Troubleshooting

• Set environment variable DEBUG=1
• See /var/run/vde_vmnet.{stdout,stderr} (when using launchd)