ovn: rewrite redirect-chassis description in ovn-nb.xml
This optional patch addresses offline comments that the documentation
in ovn-nb.xml should not describe southbound constructs or flow
details, since it is user facing documentation.
<column name="options" key="redirect-chassis">
<p>
If set, this indicates that this logical router port represents
- a distributed gateway port. In addition to the southbound
- database port representing this distributed gateway port, another
- port will be created in the southbound database that represents a
- particular instance, bound to a specific chassis, of this
- otherwise distributed logical router port. This additional port
- can then be specified as an <code>outport</code> in some of the
- ingress pipeline flows. This will cause matching packets to be
- directed to a specific chassis to carry out the egress pipeline,
- allowing a subset of logical router functionality to be
- implemented in a centralized manner. At the beginning of the
- egress pipeline, the <code>outport</code> will be reset to the
- value of the distributed port.
+ a distributed gateway port that connects this router to a logical
+ switch with a localnet port. There may be at most one such
+ logical router port on each logical router.
</p>
<p>
- This option specifies the name of the <code>chassis</code> to which
- the additional southbound port binding of type
- <code>chassisredirect</code> will be bound.
+ Even when a <code>redirect-chassis</code> is specified, the
+ logical router port still effectively resides on each chassis.
+ However, due to the implications of the use of L2 learning in the
+ physical network, as well as the need to support advanced features
+ such as one-to-many NAT (aka IP masquerading), a subset of the
+ logical router processing is handled in a centralized manner on
+ the specified <code>redirect-chassis</code>.
</p>
<p>
When this option is specified, the peer logical switch port's
- <ref column="addresses" table="Logical_Switch_Port"/> should be
- set to <code>router</code>, so that the corresponding logical
- switch destination lookup flow is only programmed on the
+ <ref column="addresses" table="Logical_Switch_Port"/> must be
+ set to <code>router</code>. With this setting, the <ref
+ column="external_mac" table="NAT"/>s specified in NAT rules are
+ automatically programmed in the peer logical switch's
+ destination lookup on the chassis where the <ref
+ column="logical_port" table="NAT"/> resides. In addition, the
+ logical router's MAC address is automatically programmed in the
+ peer logical switch's destination lookup flow on the
<code>redirect-chassis</code>.
</p>
</column>
