doc: Add documentation for Flexible-Algorithm support for OSPFv2

This commit adds documentation for Flexible-Algorithm support in OSPFv2 and related configuration and show commands. Signed-off-by: Pushpasis Sarkar <[email protected]>
FRRouting · Aug 24, 2022 · b992c06 · b992c06
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diff --git a/doc/user/ospfd.rst b/doc/user/ospfd.rst
@@ -1055,6 +1055,255 @@ TI-LFA requires a proper Segment Routing configuration.
 
    Note that so far only P2P interfaces are supported.
 
+Flexible Algorithms (Flex-Algo)
+===============================
+
+This is a bare-minimum implementation of : :t:`draft-ietf-lsr-flex-algo`. Currently
+`Shortest Path First` is the only algorithm supported, with `IGP-Metric` and
+`Shortest-Path-First` are the only values supported for `metric-type` and
+`calculation-type` respectively. In future support for more algorithms,
+metric-types and calculation-types shall be added.
+
+Please note, since Flexible Algorithm Definitions (also referred to as FAD)
+are advertised in Opaque LSAs (one ore more), capability to carry Opaque
+Linkstate Information (in the form of Opaque LSAs) should be turned on using
+``capability opaque`` and ``router-info area`` configration commands under
+`router ospf` level.
+
+.. clicmd:: flexible-algorithm (128-255)
+
+   Add a new Flexible Algorithm Definition for the current router to support.
+   This will result in the router advertsing the new flexible-algorithm
+   definition (with the specified algorithm-id) in all relevant types of
+   self-originated LSAs. By default, `calculation-type` and `metric-type`
+   for the new flexible-algorithm shall be set to `Shortest-Path-First` and
+   `IGP-Metric` respectively.
+
+.. clicmd:: no flexible-algorithm (128-255)
+
+   Remove an existing Flexible Algorithm Definition. This will result in the
+   router removing all advertisements for the specified algorithm-id from all
+   the relevant types of self-originated LSAs.
+
+.. clicmd:: flexible-algorithm (128-255) calculation-type (spf)
+
+   Set the `calculation-type` for the Flexible Algorithm Definition specified
+   by the algorithm-id. Currently `spf` (i.e. Shortest-Path-First) is the only
+   allowed value. Support for more metric-types shall be added in future.
+
+.. clicmd:: no flexible-algorithm (128-255) calculation-type
+
+   Reset the `calculation-type` for the Flexible Algorithm Definition specified
+   by the algorithm-id. Default value for calculation-type is `spf`.
+
+.. clicmd:: flexible-algorithm (128-255) metric-type (igp)
+
+   Set the `metric-type` for the Flexible Algorithm Definition specified
+   by the algorithm-id. Currently `igp-metric` is the only allowed value.
+   Support for more metric-types shall be added in future.
+
+.. clicmd:: no flexible-algorithm (128-255) metric-type
+
+   Reset the `metric-type` for the Flexible Algorithm Definition specified
+   by the algorithm-id. Default value for metric-type is `igp-metric`.
+
+.. clicmd:: flexible-algorithm (128-255) priority (0-4294967295)
+
+   Set the `priority` for the Flexible Algorithm Definition specified
+   by the algorithm-id. Default value of priority is 0.
+
+.. clicmd:: no flexible-algorithm (128-255) priority
+
+   Reset the `priority` for the Flexible Algorithm Definition specified
+   by the algorithm-id. Default value for priority is 0.
+
+.. clicmd:: flexible-algorithm (128-255) exclude-admin-group (0-4294967295)
+
+   Add the specified `admin-group` value to the list of Exclude-Admin-Groups
+   for the Flexible Algorithm Definition specified by the algorithm-id.
+   This will add the admin-group to the list of admin-groups advertised in
+   the Exclude-Admin-Group Sub-TLV included in the corresponding Flexible
+   Algorithm Definition TLV (carried inside the Router-Info external LSA).
+
+.. clicmd:: no flexible-algorithm (128-255) exclude-admin-group (0-4294967295)
+
+   Remove the specified `admin-group` from the list of Exclude-Admin-Groups
+   for the Flexible Algorithm Definition specified by the algorithm-id.
+   This will remove the admin-group from the list of admin-groups advertised in
+   the Exclude-Admin-Group Sub-TLV included in the corresponding Flexible
+   Algorithm Definition TLV (carried inside the Router-Info external LSA).
+
+.. clicmd:: flexible-algorithm (128-255) include-any-admin-group (0-4294967295)
+
+   Add the specified `admin-group` to the list of Include-Any-Admin-Groups
+   for the Flexible Algorithm Definition specified by the algorithm-id.
+   This will add the admin-group to the list of admin-groups advertised in
+   the Include-Any-Admin-Group Sub-TLV included in the corresponding Flexible
+   Algorithm Definition TLV (carried inside the Router-Info external LSA).
+
+.. clicmd:: no flexible-algorithm (128-255) include-any-admin-group (0-4294967295)
+
+   Remove the specified `admin-group` from the list of Include-Any-Admin-Groups
+   for the Flexible Algorithm Definition specified by the algorithm-id.
+   This will remove the admin-group from the list of admin-groups advertised in
+   the Include-Any-Admin-Group Sub-TLV included in the corresponding Flexible
+   Algorithm Definition TLV (carried inside the Router-Info external LSA).
+
+.. clicmd:: flexible-algorithm (128-255) include-all-admin-group (0-4294967295)
+
+   Add the specified `admin-group` to the list of Include-All-Admin-Groups
+   for the Flexible Algorithm Definition specified by the algorithm-id.
+   This will add the admin-group to the list of admin-groups advertised in
+   the Include-All-Admin-Group Sub-TLV included in the corresponding Flexible
+   Algorithm Definition TLV (carried inside the Router-Info external LSA).
+
+.. clicmd:: no flexible-algorithm (128-255) include-all-admin-group (0-4294967295)
+
+   Remove the specified `admin-group` from the list of Include-All-Admin-Groups
+   for the Flexible Algorithm Definition specified by the algorithm-id.
+   This will remove the admin-group from the list of admin-groups advertised in
+   the Include-All-Admin-Group Sub-TLV included in the corresponding Flexible
+   Algorithm Definition TLV (carried inside the Router-Info external LSA).
+
+.. clicmd:: flexible-algorithm (128-255) exclude-srlg (0-4294967295)
+
+   Add the specified `srlg` value to the list of Exclude-SRLGs
+   for the Flexible Algorithm Definition specified by the algorithm-id.
+   This will add the SRLG vslue to the list of SRLGs advertised in
+   the Exclude-SRLG Sub-TLV included in the corresponding Flexible
+   Algorithm Definition TLV (carried inside the Router-Info external LSA).
+
+.. clicmd:: no flexible-algorithm (128-255) exclude-srlg (0-4294967295)
+
+   Remove the specified `srlg` from the list of Exclude-SRLGs
+   for the Flexible Algorithm Definition specified by the algorithm-id.
+   This will remove the SRLG value from the list of SRLGs advertised in
+   the Exclude-SRLG Sub-TLV included in the corresponding Flexible
+   Algorithm Definition TLV (carried inside the Router-Info external LSA).
+
+.. clicmd:: flexible-algorithm (128-255) flags (0-4294967295)
+
+   Add the specified `flags` value to the list of flag values for the
+   Flexible Algorithm Definition specified by the algorithm-id.
+   This will add the flags to the list of Flag values advertised in
+   the Flags Sub-TLV included in the corresponding Flexible Algorithm
+   Definition TLV (carried inside the Router-Info external LSA).
+
+.. clicmd:: no flexible-algorithm (128-255) exclude-srlg (0-4294967295)
+
+   Remove the specified `srlg` from the list of flag values for the
+   Flexible Algorithm Definition specified by the algorithm-id.
+   This will remove the flags from the list of Flag values advertised in
+   the Flags Sub-TLV included in the corresponding Flexible Algorithm
+   Definition TLV (carried inside the Router-Info external LSA).
+
+.. clicmd:: flexible-algorithm (128-255) prefix-advertise-metric (0-4294967295)
+
+   Set the `prefix-advertise-metric` for the Flexible Algorithm Definition
+   specified by the algorithm-id. This results in the router advertising
+   the configured value inside a Flexible-Algorithm Prefix-Metric(FAPM)
+   Sub-TLV (carried inside Extended Prefix TLV within a Extended Prefix
+   Opaque LSA), as well as inside a Flexible-Algorithm ASBR Metric(FAAM)
+   Sub-TLV (to be carried in the Extended Inter-Area ASBR TLV within a
+   new Extended Inter-Area LSA). By default no prefix metric is advertised.
+
+.. clicmd:: no flexible-algorithm (128-255) prefix-advertise-metric
+
+   Reset the `prefix-advertise-metric` for the Flexible Algorithm Definition
+   specified by the algorithm-id. This removes advertisement of the
+   previously configured value from all the relevant Sub-TLVs, TLVs and LSAs.
+
+.. clicmd:: show ip ospf [vrf (vrf-name)] database opaque-area
+
+   This existing command's output has been enhanced to display the new
+   Flexible-Algorithm definition LSAs, TLVs and Sub-TLVs.
+
+   Following show command output shows the new Flexible Algoritms Definition
+   LSAs, TLVs and Sub-TLVs advertised.
+
+   .. code-block:: frr
+
+      frr# show ip ospf database opaque-area
+
+            OSPF Router with ID (1.1.1.1)
+
+
+                     Area-Local Opaque-LSA (Area 0.0.0.0)
+
+      LS age: 524
+      Options: 0x42 : *|O|-|-|-|-|E|-
+      LS Flags: 0x1
+      LS Type: Area-Local Opaque-LSA
+      Link State ID: 4.0.0.0 (Area-Local Opaque-Type/ID)
+      Advertising Router: 1.1.1.1
+      LS Seq Number: 8000000b
+      Checksum: 0x9b60
+      Length: 80
+
+      Opaque-Type 4 (Router Information LSA)
+      Opaque-ID   0x0
+      Opaque-Info: 60 octets of data
+      Router Capabilities: 0x10000000
+      Flexible Algorithm Defintion TLV: Length: 48
+         Algorithm-Identifier = 128
+         Priority = 10
+         Metric-Type = Invalid-Metric-Type
+         Calculation-Type = spf
+         FAD Exclude Admin Groups:
+            [ 30 ]
+         FAD Include Any Admin Groups:
+            [ 60, 70 ]
+         FAD Include All Admin Groups:
+            [ 20 ]
+         FAD Flags:
+            [ 10 ]
+         FAD Exclude SRLGs:
+            [ 10 ]
+
+      LS age: 771
+      Options: 0x42 : *|O|-|-|-|-|E|-
+      LS Flags: 0x6
+      LS Type: Area-Local Opaque-LSA
+      Link State ID: 4.0.0.0 (Area-Local Opaque-Type/ID)
+      Advertising Router: 2.2.2.2
+      LS Seq Number: 8000000b
+      Checksum: 0x4d9d
+      Length: 28
+
+      Opaque-Type 7 (Extended Prefix Opaque LSA)
+      Opaque-ID   0x1
+      Opaque-Info: 24 octets of data
+      Extended Prefix TLV: Length 20
+         Route Type: 1
+         Address Family: 0x0
+         Flags: 0x40
+         Address: 1.1.1.1/32
+      Prefix FAPM Sub-TLV: Length 8
+         Algorithm: 128
+         Flags: 0x0
+         Metric: 100
+
+      LS age: 1383
+      Options: 0x42 : *|O|-|-|-|-|E|-
+      LS Flags: 0x1
+      LS Type: Area-Local Opaque-LSA
+      Link State ID: 11.0.0.0 (Area-Local Opaque-Type/ID)
+      Advertising Router: 1.1.1.1
+      LS Seq Number: 8000000a
+      Checksum: 0xc826
+      Length: 40
+
+      Opaque-Type 11 (Extended Inter-Area ASBR Opaque LSA)
+      Opaque-ID   0x0
+      Opaque-Info: 20 octets of data
+      Extended Inter-Area ASBR TLV: Length 16
+         ASBR-Router-Id: 1.1.1.1
+      Flex-Algo ASBR Metric Sub-TLV: Length 8
+         Algorithm: 128
+         Metric:100
+
+      frr#
+
 .. _debugging-ospf:
 
 Debugging OSPF