spec for extra-dhcp-opts
Related-bug: #1585170 Change-Id: I2556d75fdf922c3c1a4705bae7c426d32fd98a50
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Eyal Leshem
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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=======================
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Support extra-dhcp-opts
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=======================
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Problem Description
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===================
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For enable to users to configure custom dhcp-options neutron-api
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supply the extra-dhcp-opts extension [1]_.
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According to RFC 2131 [2]_ - dhcp-options is list that composed from
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tags-values pairs - when tag is number in the rage of 0-255,
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and the value is a variable-length byte-sequence.
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(for example RFC 2132 [3]_ defines list dhcp options
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for BOOTP vendor-extensions).
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Neutron spec define the extra-dhcp-opts as a set of pairs
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that each pair combined from opt_name and opt_value [1]_ , but the spec
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didn't not define how opt_name should be translated to dhcp-opt number.
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According to the examples in the spec, and according to neutron reference
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implementation, the format of the option names is derived from the
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configuration file of dnsmsq-dhcp server ( as it used as the server in the
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reference implementation ). In addition that configuration enables to
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configure fields in the dhcp-packet itself (the "server-ip-address"
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as it change the siaddr - that isn't part of the
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options-scope in the dhcp-packet [2]_).
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In dragonflow we are using custom dhcp-app for supporting our
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distributed-dhcp solution [4]_ . This app currently returns a
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pre-defined set of dhcp-optios , ans not using the lports' extra-dhcp-opt
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attribute.
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We want to propose a new implementation that supports the extra-dhcp-option -
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By supporting the opt-name in format of dnsmasq-conf , alongside with other
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configurations format (for example: dhcpd.conf format or by supplying the tags
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directly as a number - "11" for dhcp-opt 11).
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Proposed Change
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===============
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In the proposed change we want to:
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* Define data-base model that will represent dhcp-parameters,
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This model will be used for saving the objects in the NB-API.
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* The model will composed be key and value, when key is a string that's
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represent the parameter name, and the value is an any field-type that
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suite for representing the data.
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* Currently we planning to support the following dhcp-parameters:
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* opt - represent the dhcp-options, value represented by dictionary -
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when the key is value between 0-255 (represents the option-number),
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and the value is string (represents the opt-value).
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* siaddr - represents the siaddr field the dhcp-header. The value
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is represented by ip-address field.
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* In the L2 mech-driver - add code that translate the opt_name from the
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api supported language to the dhcp-parameters object that
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described above (in case of unknown opt_name - port creation should fail).
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* In the DHCP app - add code that answers to the dhcp requests according to
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the configured dhcp-params.
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Execution workflow:
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===================
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* User generates an neutron-lport-create api-request with :
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.. code-block:: json
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{"extra_dhcp_opts":[{"opt_value": "testfile.1", "opt_name": "bootfile-name"},
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{"opt_value": "192.168.0.100", "opt_name": "server-ip-address"}]
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}
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* l2 plugin will translate it to:
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.. code-block:: json
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{
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"dhcp_params":{
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"opts" : {"67": "testfile.1"},
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"siaddr" : "192.168.0.100
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}
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}
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* The lport will be stored in the NB-db with dhcp opt attributes.
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* The dhcp-app will use that value for answering request that ask for
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dhcp-option 67.
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References
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==========
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.. [#] https://specs.openstack.org/openstack/neutron-specs/specs/api/extra_dhcp_options__extra-dhcp-opt\_.html
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.. [#] https://tools.ietf.org/html/rfc2131
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.. [#] https://tools.ietf.org/html/rfc2132
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.. [#] https://github.com/openstack/dragonflow/blob/master/doc/source/distributed_dhcp.rst
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@ -72,6 +72,7 @@ Specs
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bgp_dynamic_routing
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tunneling_app
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logical_port_locality
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extra_dhcp_opts
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Templates
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---------
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