Difference between revisions of "Neutron/enable-to-set-dhcp-port-attributes"
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=== Implementation analysis === | === Implementation analysis === | ||
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* A DHCP port is identified by "device_id" and "device_owner". | * A DHCP port is identified by "device_id" and "device_owner". | ||
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(note: Thus if a user want to assign a dhcp_agent to a network explicitly, | (note: Thus if a user want to assign a dhcp_agent to a network explicitly, | ||
| − | issue "dhcp-agent-network-add" API before the first port creation.) | + | issue "dhcp-agent-network-add" API before the first port creation.) |
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==== Other possible options for this blueprint ==== | ==== Other possible options for this blueprint ==== | ||
Revision as of 22:42, 24 December 2013
Contents
Background and motivation
There is no way for a user to specify an ip address (, mac address and so on) of a DHCP port. This is very inconvenient for a user who wishes to fully control over ip address assignment.
This blueprint is based on such actual user's requirement.
Use cases
Use case1
When a user migrates their on-premises system to a cloud environment, there are cases where the user wants to use the same ip address for their virtual servers. In such a case, the user needs to specify an ip address of the DHCP server to avoid conflict with an existing servers' ip address.
Use case2
A user wants to specify an ip address of a DHCP server for security reasons. They don't want DHCP servers to float around.
Goal
The goal of this blueprint is to enable users to explicitly set DCHP port attributes (especially ip address).
Proposal
Add 'dhcp_port' parameter to "dhcp-agent-network-add" API. If 'dhcp_port' parameter is specified, a DHCP port is created at the same time. A user who wants to control a DCHP port attributes must assign a dhcp-agent explicitly. I think this restriction will not be an issue for such users.
Proposed API
Add 'dhcp_port' input parameter to "dhcp-agent-network-add" API provided by the "dhcpagentscheduler" extension.
action: POST
url: /agents/<agent id>/networks
request body:
- current
{'network_id': <network_id>}
- new
{'network_id': <network_id>,
'dhcp_port': {'fixed_ips': <fixed ips>, 'mac_address': <mac address>, 'name': <name>}}
note:'dhcp_port' is optional. 'fixed_ips', 'mac_address' and 'name' in 'dhcp_port' are optional. the format of 'fixed_ips' is same as port resource.
response body: none
description:
Assign the dhcp-agent specified by <agent id> to the network specified by <network_id>. If 'dhcp_port' is specified the DHCP port is created using the specified attributes.
example of request body:
{'network_id': "df514142-90f4-4ab2-8d35-aaaf0b5c4dee",
'dhcp_port': {'fixed_ips': [{'subnet_id': "fd3bc91d-70e5-4325-8f19-c52f2998953e", 'ip_address': "20.0.0.10"}]}}
Implementation analysis
Current implementation
- A DHCP port is identified by "device_id" and "device_owner".
"device_id" is generated by network_id for the port and dhcp_agent's host. (i.e. unique with network_id and dhcp_agent's host pair) "device_owner" is "network:dhcp".
- A DHCP port is created via "create_dhcp_port" RPC call by a dhcp_agent, if the port does not exist yet.
- A DHCP port creation is triggered by assigning a dhcp_agent to a network. There are two typical cases.
1) explicit assignment via API (eg. when the "neutron dhcp-agent-network-add" CLI is executed.)
2) the first port creation of a network (with one or more dhcp-enabled subnet). if the network is not assigned to a dhcp_agent yet, force dhcp-agent scheduling is done.
(note: Thus if a user want to assign a dhcp_agent to a network explicitly, issue "dhcp-agent-network-add" API before the first port creation.)
Other possible options for this blueprint
There are several implementation options to achieve the goal other than our proposal.
- option 1
Add 'dhcp_ips' attribute to the subnet. (note that it must be a list since multiple dhcp-agent can be assigned to a network) When create_dhcp_port is called, one of the unused ip address in the list is used. Disadvantage of this option is that it needs a large amount of code addition/modification.
- option 2
Create a DHCP port explicitly by a user specifying 'device_id' and 'device_owner' attributes before dhcp-agent assignment to a network. There are two issues for this option.
1) how to generate 'device_id' is not open.
2) a port creation forces dhcp-agent scheduling. A dhcp-agent other than the dhcp-agent represented by specified 'device_id' may be assigned. On the other hand assigning dhcp-agent before creating port causes DHCP port creation by create_dhcp_port RPC call by a dhcp-agent.
Our proposal solves those issues and we believe is the best solution for implementing this blueprint.
TODO (CLI)
I don't think adding explicit option to "neutron dhcp-agent-network-add" CLI is necessary but supporting 'value-specs' is enough.
It seems "neutron dhcp-agent-network-add" CLI does not accept 'value-specs' now. So it needs to support.
