macOS provides networking API for VMs called 'vmnet.framework':
https://developer.apple.com/documentation/vmnet

We can provide its support as the new QEMU network backends which
represent three different vmnet.framework interface usage modes:

  * `vmnet-shared`:
    allows the guest to communicate with other guests in shared mode and
    also with external network (Internet) via NAT. Has (macOS-provided)
    DHCP server; subnet mask and IP range can be configured;

  * `vmnet-host`:
    allows the guest to communicate with other guests in host mode.
    By default has enabled DHCP as `vmnet-shared`, but providing
    network unique id (uuid) can make `vmnet-host` interfaces isolated
    from each other and also disables DHCP.

  * `vmnet-bridged`:
    bridges the guest with a physical network interface.

This backends cannot work on macOS Catalina 10.15 cause we use
vmnet.framework API provided only with macOS 11 and newer. Seems
that it is not a problem, because QEMU guarantees to work on two most
recent versions of macOS which now are Big Sur (11) and Monterey (12).

Also, we have one inconvenient restriction: vmnet.framework interfaces
can create only privileged user:
`$ sudo qemu-system-x86_64 -nic vmnet-shared`

Attempt of `vmnet-*` netdev creation being unprivileged user fails with
vmnet's 'general failure'.

This happens because vmnet.framework requires `com.apple.vm.networking`
entitlement which is: "restricted to developers of virtualization software.
To request this entitlement, contact your Apple representative." as Apple
documentation says:
https://developer.apple.com/documentation/bundleresources/entitlements/com_apple_vm_networking

One more note: we still have quite useful but not supported
'vmnet.framework' features as creating port forwarding rules, IPv6
NAT prefix specifying and so on.

Nevertheless, new backends work fine and tested within `qemu-system-x86-64`
on macOS Bir Sur 11.5.2 host with such nic models:
  * e1000-82545em
  * virtio-net-pci
  * vmxnet3

The guests were:
  * macOS 10.15.7
  * Ubuntu Bionic (server cloudimg)


This series partially reuses patches by Phillip Tennen:
https://patchew.org/QEMU/20210218134947.1860-1-phillip.ennen@gmail.com/
So I included them signed-off line into one of the commit messages and
also here.

v1 -> v2:
 Since v1 minor typos were fixed, patches rebased onto latest master,
 redundant changes removed (small commits squashed)
v2 -> v3:
 - QAPI style fixes
 - Typos fixes in comments
 - `#include`'s updated to be in sync with recent master
v3 -> v4:
 - Support vmnet interfaces isolation feature
 - Support vmnet-host network uuid setting feature
 - Refactored sources a bit
v4 -> v5:
 - Missed 6.2 boat, now 7.0 candidate
 - Fix qapi netdev descriptions and styles
   (@subnetmask -> @subnet-mask)
 - Support vmnet-shared IPv6 prefix setting feature
v5 -> v6
 - provide detailed commit messages for commits of
   many changes
 - rename properties @dhcpstart and @dhcpend to
   @start-address and @end-address
 - improve qapi documentation about isolation
   features (@isolated, @net-uuid)
v6 -> v7:
 - update MAINTAINERS list
v7 -> v8
 - QAPI code style fixes
v8 -> v9
 - Fix building on Linux: add missing qapi
   `'if': 'CONFIG_VMNET'` statement to Netdev union
v9 -> v10
 - Disable vmnet feature for macOS < 11.0: add
   vmnet.framework API probe into meson.build.
   This fixes QEMU building on macOS < 11.0:
   https://patchew.org/QEMU/20220110034000.20221-1-jasowang@redhat.com/
v10 -> v11
 - Enable vmnet for macOS 10.15 with subset of available
   features. Disable vmnet for macOS < 10.15.
 - Fix typos

Vladislav Yaroshchuk (7):
  net/vmnet: add vmnet dependency and customizable option
  net/vmnet: add vmnet backends to qapi/net
  net/vmnet: implement shared mode (vmnet-shared)
  net/vmnet: implement host mode (vmnet-host)
  net/vmnet: implement bridged mode (vmnet-bridged)
  net/vmnet: update qemu-options.hx
  net/vmnet: update MAINTAINERS list

 MAINTAINERS                   |   5 +
 meson.build                   |  23 ++-
 meson_options.txt             |   2 +
 net/clients.h                 |  11 ++
 net/meson.build               |   7 +
 net/net.c                     |  10 +
 net/vmnet-bridged.m           | 113 ++++++++++++
 net/vmnet-common.m            | 332 ++++++++++++++++++++++++++++++++++
 net/vmnet-host.c              | 108 +++++++++++
 net/vmnet-shared.c            |  94 ++++++++++
 net/vmnet_int.h               |  48 +++++
 qapi/net.json                 | 137 +++++++++++++-
 qemu-options.hx               |  25 +++
 scripts/meson-buildoptions.sh |   3 +
 14 files changed, 915 insertions(+), 3 deletions(-)
 create mode 100644 net/vmnet-bridged.m
 create mode 100644 net/vmnet-common.m
 create mode 100644 net/vmnet-host.c
 create mode 100644 net/vmnet-shared.c
 create mode 100644 net/vmnet_int.h

-- 
2.23.0