Merge "Specification for Dnsmasq DHCPv6"
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specs/juno/ipv6-dnsmasq-dhcpv6-stateless-stateful.rst
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specs/juno/ipv6-dnsmasq-dhcpv6-stateless-stateful.rst
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=====================================================
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Support DHCPv6 stateless and stateful mode in Dnsmasq
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=====================================================
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As [Spec_RADVD]_ is proposed to use radvd as the preferred reference
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implementation for IPv6 Router Advertisements and SLAAC, this spec is
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to allow tenant VM to obtain stateful dhcpv6 address or stateless
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dhcpv6 address by Dnsmasq when ipv6_address_mode of a tenant subnet is set.
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Launchpad blueprint:
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https://blueprints.launchpad.net/neutron/+spec/dnsmasq-ipv6-dhcpv6-stateless
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https://blueprints.launchpad.net/neutron/+spec/dnsmasq-ipv6-dhcpv6-stateful
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Problem description
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===================
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1. When dhcpv6 stateful is set as IPv6 address mode of a tenant subnet,
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OpenStack admin wishes tenant VMs can obtain IPv6 address and optional
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info (such as DNS info) from OpenStack network service.
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2. When dhcpv6 stateless is set as IPv6 address mode of a tenant subnet,
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router advertisement is taken care of by either external router or
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OpenStack managed RADVD. OpenStack admin wishes tenant VMs can obtain
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IPv6 address by SLAAC and obtain optional info from OpenStack network
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service.
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::
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+----------------------------------------------------------------------+
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| | +---------------------------------+
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| +------------------------------+ +---------------------------+ | | |
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| |dhcp namespace | | router | | | +--------------+ |
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| | +-----------+ | | namespace +----------+ | | | | | |
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| | | dnsmasq | | | | RADVD | | | | | | |
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| | +-+---+-----+--------+ | | +----+--------+++ | | | +-------> | |
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| | | | qdhcp-xxxx | | | | qr-xxxx || | | | | | | |
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| | | +-------+------+ | | +----+---------+ | | | | +-----> VM | |
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| | | | | | | | | | | | | | | |
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| +------------------------------+ +---------------------------+ | | | | +-------+------+ |
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| | | | | | | | | | |
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| | +--+--------------------------------+-+ | | | | | | |
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| | | br-int | | | | | | +--------+--------+ |
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| | +------------------+------------------+ | | | | | | br-int | |
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| | | | | | | | +--------+--------+ |
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| | | | | | | | | |
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| | +------+------+ | | | | | | |
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| | | br-eth0 | | | | | | +---------------+ |
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| | +------+------+ | | | | | | br-eth0 | |
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| | | | | | | | +---------------+ |
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| | | | | | | | | |
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| | +-----+-----+ | | | | | +------+-------+ |
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| | | eth0 | | | | | | | eth0 | |
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+-----------------------------+-----+-----+----------------------------+ +--------+-------+------+---------+
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| +--------------------------------------------------------+
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+------------------------------------------------------------------------+
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IPv6 address/optional info | RA |
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+----------------+
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Proposed change
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===============
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According to [DNSMASQ_MANPAGE]_:
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1. DHCPv6 stateless mode: dnsmasq in ‘static’ mode with ‘–dhcp-optsfile’
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option specified can be leveraged to use dnsmasq as a simple stateless
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dhcp server.
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2. DHCPv6 stateful mode: dnsmasq in ‘static’ mode with ‘–dhcp-hostsfile’
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and ‘–dhcp-optsfile’ options specified can be leveraged to use dnsmasq
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as stateful dhcp server.
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Alternatives
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------------
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None
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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In Icehouse release, ipv6_ra_mode and ipv6_address_mode are introduced
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to subnet API to enable tenant network IPv6 support.
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Rest API change for IPv6 modes in Icehouse reference: [IPv6_MODES_REST]_
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This blueprint will implement the functionality required to satisfy
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IPv6 Subnets with ipv6_address_mode set to ‘dhcpv6-stateful’ or
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‘dhcpv6-stateless’.
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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* This change will require support in python-neutronclient for the two
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IPv6 subnet attributes - which is currently in `review <https://review.openstack.org/#/c/75871/>`_
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Performance Impact
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------------------
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None
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Other deployer impact
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---------------------
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* This change will change the behavior of Neutron in specific
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configurations, when the IPv6 attributes for Subnets are set.
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Previously, the attributes were no-ops.
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Developer impact
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----------------
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None
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Implementation
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==============
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* Subnets will be created with ‘ipv6_address_mode’ set to
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‘dhcpv6-stateful’ or ‘dhcpv6-stateless’.
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* If no dnsmasq process for subnet’s network is launched,
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Neutron will launch new dnsmasq process on subnet’s dhcp port
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in ‘qdhcp-‘ namespace. If previous dnsmasq process is already
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launched, restart dnsmasq with new configuration.
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* Neutron will update dnsmasq process and restart it when subnet gets
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updated.
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Assignee(s)
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-----------
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Primary assignee:
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* Shixiong
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* xuhanp
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Work Items
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----------
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* Break down this `code review <https://review.openstack.org/#/c/70649>`_
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into smaller patches, and submit new code review for dhcpv6
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stateful/stateless mode.
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Dependencies
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============
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* The assumption of this spec is Router Advertisement is provided by
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either provider network router or OpenStack Network Service (One
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implementation is RADVD [Spec_RADVD]_).
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* Bump DNSMASQ version to 2.63 to support IPv6 tag. [DNSMASQ_VERSTION]_
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Testing
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=======
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* Add unit tests to support Subnets created with the ipv6_address_mode
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set to ‘dhcpv6-stateful’ or ‘dhcpv6-stateless.
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* Verify that dnsmasq can be launched with expected mode and options,
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in correct namespace.
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* Add tempest API and scenairo tests for stateful and stateless dhcpv6.
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Reference: [API_TESTS_IPV6]_
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Documentation Impact
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====================
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Documentation about this network configuration will need to be
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written.
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References
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==========
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.. [Spec_RADVD] `Spec for adding support for radvd for IPv6 SLAAC
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<https://review.openstack.org/#/c/101306>`_
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.. [DNSMASQ_MANPAGE] `DNSMASQ man page
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<http://www.thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html>`_
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.. [API_TESTS_IPV6] `Add IPv6 API test cases for Neutron Subnet API 254
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<https://review.openstack.org/100134>`_
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.. [DNSMASQ_VERSTION] `DNSMASQ minimum version for IPv6
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<https://bugs.launchpad.net/neutron/+bug/1233339>`_
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.. [IPv6_MODES_REST] `Rest API change for IPv6 modes in Icehouse`
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<http://docs-draft.openstack.org/43/88043/9/gate/gate-neutron-specs-docs/82c251a/doc/build/html/specs/juno/ipv6-provider-nets-slaac.html#rest-api-impact>_
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