When creating an instance via the OS::Nova::Server resource type in a Heat template, specifying a network and a subnet to get a port created on the instance, it fails on Neutron with Unrecognized attribute(s) 'no_fixed_ips'.

Again, the reason why this fails is because for ports without fixed IPs, Neutron expects fixed_ips = [] as it does not understand no_fixed_ips, so Heat should not be passing that. Commit [1] where the no_fixed_ips feature was introduced in Heat, added logic to avoid passing no_fixed_ips to Neutron, but that logic was never added for the case where the port is requested to be created via OS::Nova::Server.

Here's a template reproducing the issue (Heat versions affected: >= Wallaby):

{{heat_template_version: wallaby

resources:

server_test:
type: OS::Nova::Server
properties:
name: server_test
config_drive: true
flavor: m1.small
image: "focal-raw"
networks:

• network: 0924ec50-c1b7-4ea9-bdd2-334772fd3398
  port_extra_properties:
  port_security_enabled: false
  subnet: cb49c91d-62d0-4677-b121-0dcf0476ecf0}}

[1] https://opendev.org/openstack/heat/commit/9292264aa74d6d9e6e8f58045c7e3faf755ea725