Public bug reported: In looking through the IPAM code, I ran across this check [1] which is as a major difference between the pluggable and non-pluggable IPAM code paths. I got to thinking about it, and I don't see a valid use case for this check.
Let's say an ip_address was specified in fixed_ips and the subnet cidr is detected by _get_subnet_for_fixed_ip as the provisional PD prefix (::1/64). That would mean that the IP address specified is contained in ::1/64 (i.e. ::1 or ::dead:beef:1:1) in order for check_subnet_ip to match it [2]. This doesn't make sense in the first place to specify this kind of IP address for a subnet for which the network address isn't even known. We can't allocate such an IP to the port. Now let's look at what happens if even if you do specify such a nonsensical address. This conditional is False and so it drops to the else clause [3]. Here it is checked if it is a router port and if it is an auto address subnet. PD subnets are all auto address subnets, so it depends on if it is a router port. If it is, the subnet is added to the IPs to allocate *without* the ip address! If it isn't, the entire thing is ignored. Either way, the specific IP address that was specified is ignored. All auto address subnets are added to the list later so it doesn't even matter that it *might* have been added here. So, if I understand everything correctly, this check doesn't make sense. [1] https://github.com/openstack/neutron/blob/c5bc5bda34/neutron/db/ipam_non_pluggable_backend.py#L248-249 [2] https://github.com/openstack/neutron/blob/c5bc5bda34/neutron/ipam/utils.py#L28 [3] https://github.com/openstack/neutron/blob/c5bc5bda34/neutron/db/ipam_non_pluggable_backend.py#L268 ** Affects: neutron Importance: Low Assignee: Carl Baldwin (carl-baldwin) Status: In Progress ** Tags: l3-ipam-dhcp ** Changed in: neutron Importance: Undecided => Low ** Tags added: l3-ipam-dhcp -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to neutron. https://bugs.launchpad.net/bugs/1568992 Title: PD adds a non-sensical check to nonpluggable IPAM Status in neutron: In Progress Bug description: In looking through the IPAM code, I ran across this check [1] which is as a major difference between the pluggable and non-pluggable IPAM code paths. I got to thinking about it, and I don't see a valid use case for this check. Let's say an ip_address was specified in fixed_ips and the subnet cidr is detected by _get_subnet_for_fixed_ip as the provisional PD prefix (::1/64). That would mean that the IP address specified is contained in ::1/64 (i.e. ::1 or ::dead:beef:1:1) in order for check_subnet_ip to match it [2]. This doesn't make sense in the first place to specify this kind of IP address for a subnet for which the network address isn't even known. We can't allocate such an IP to the port. Now let's look at what happens if even if you do specify such a nonsensical address. This conditional is False and so it drops to the else clause [3]. Here it is checked if it is a router port and if it is an auto address subnet. PD subnets are all auto address subnets, so it depends on if it is a router port. If it is, the subnet is added to the IPs to allocate *without* the ip address! If it isn't, the entire thing is ignored. Either way, the specific IP address that was specified is ignored. All auto address subnets are added to the list later so it doesn't even matter that it *might* have been added here. So, if I understand everything correctly, this check doesn't make sense. [1] https://github.com/openstack/neutron/blob/c5bc5bda34/neutron/db/ipam_non_pluggable_backend.py#L248-249 [2] https://github.com/openstack/neutron/blob/c5bc5bda34/neutron/ipam/utils.py#L28 [3] https://github.com/openstack/neutron/blob/c5bc5bda34/neutron/db/ipam_non_pluggable_backend.py#L268 To manage notifications about this bug go to: https://bugs.launchpad.net/neutron/+bug/1568992/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : yahoo-eng-team@lists.launchpad.net Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp
