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[OpenStack Infra <1987666@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.opendev.org/c/openstack/neutron/+/859143
Committed: https://opendev.org/openstack/neutron/commit/1abb77d7a63cde2aa9640351f663870c14430919
Submitter: "Zuul (22348)"
Branch:    master

commit 1abb77d7a63cde2aa9640351f663870c14430919
Author: Fernando Royo <froyo@xxxxxxxxxx>
Date:   Fri Sep 23 20:53:09 2022 +0200

    Check subnet overlapping after add router interface
    
    When simultaneous attempts are made to add an interface
    to the same router including overlapping networks in cidrs,
    both attempts are successful. There is a check to avoid this
    overlap but is performed when creating the network interface
    and it is done over the ports already attached to the router,
    so at this moment the check is not able to detect the
    overlapping. Furthermore, the create_port operation over the
    ML2 plugin  must be executed in isolated transactions, so
    trying to control the execution context or adding additional
    steps to the transaction is not feasible.
    
    This patch checks once the RouterPort is created on the
    neutron database if there is more than one overlapping port,
    triggering in that case the exception that will remove the
    the culprit of overlapping.
    
    Closes-Bug: #1987666
    Change-Id: I7cec8b53e72e7abf34012906e6adfecf079525af


** Changed in: neutron
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1987666

Title:
  Race condition when adding two subnet with same cidr to router

Status in neutron:
  Fix Released

Bug description:
  When two subnets with the same cidr are connected to a router, the
  second request should fail with an error like this:

  BadRequest: resources._ipv4_gateway_interface: Bad router request:
  Cidr 10.100.130.0/24 of subnet 41626435-77b8-4858-9594-a6709e2de5c5
  overlaps with cidr 10.100.130.0/24 of subnet cd6566de-
  add9-4129-9f5e-5b99cc57194c

  But if those connections are triggered simultaneously, both subnets
  finally are connected to the router without raising the previous
  BadRequest.

  A simple script like this allow to replicate the situation described:

  echo "create resources"
  openstack router create r0
  openstack network create n0-A
  openstack subnet create sn0-A --network n0-A --subnet-range 10.100.0.0/24
  openstack network create n0-B
  openstack subnet create sn0-B --network n0-B --subnet-range 10.100.0.0/24

  echo "connect subnets to routers"
  openstack router add subnet r0 sn0-A&
  openstack router add subnet r0 sn0-B

  as result:

  (overcloud) [stack@undercloud-0 ~]$ openstack router show r0 -c interfaces_info -f value; done
  [{'port_id': '171028ae-3a0d-4690-86fd-09bf3cf9fabe', 'ip_address': '10.100.0.1', 'subnet_id': 'b1f1cfb0-3d8d-41ae-b5e4-4839f4c5d7a4'}, {'port_id': '46596629-a1bc-49d6-903e-45cd27ba6b22', 'ip_address': '10.100.0.1', 'subnet_id': '1f463853-487e-4aeb-b0ec-cd43048bf692'}]

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