Add MANUAL proxy-arp mode and manual-ip-prefix leaf-list to openconfig-if-ip IPv4 mode

[jsingh2-c]

…penconfig-if-ip model

Change Scope

• [This change extends the openconfig-if-ip model to support manual/static proxy ARP behavior by adding a manual-ip-prefixes list, placed parallel to the existing config and state containers under the /ipv4/proxy-arp subtree.
  Each list entry (manual-ip-prefix) is keyed by prefix and models both config and state, following the openconfig model.
  The mode enumeration under proxy-arp/config is extended to include a new value: MANUAL. In MANUAL mode, only prefixes defined under manual-ip-prefixes are eligible for proxy ARP responses.]
• [This change is fully backward compatible:
  Existing enum values (DISABLE, REMOTE_ONLY, ALL) remain unchanged.
  Existing clients not using MANUAL mode are unaffected.
  The new list is optional and has no operational effect unless mode=MANUAL.]

Platform Implementations

• Implementation A: Ciena 6500
  The platform requires operator‑controlled manual proxy ARP for deployment scenarios.
  The implementation uses Linux kernel proxy ARP + NFtables filtering.
  link to documentation
• Implementation B: OpenROADM Proxy ARP Model
  OpenROADM models a similar structure for proxy ARP entries as “proxy‑subnet” using CIDR prefixes, which our model aligns with conceptually. link to documentation

Tree View

[Next, cut and paste the relevant portion of the tree with enough context for reviewers to quickly understand the change.]

 module: openconfig-if-ip
    augment /oc-if:interfaces/oc-if:interface/oc-if:subinterfaces/oc-if:subinterface:
     +--rw ipv4
        +--rw addresses
        |  +--rw address* [ip]
        |     +--rw ip        -> ../config/ip
        |     +--rw config
        |     |  +--rw ip?              oc-inet:ipv4-address
        |     |  +--rw prefix-length?   uint8
        |     |  +--rw type?            ipv4-address-type
        |     +--ro state
        |     |  +--ro ip?              oc-inet:ipv4-address
        |     |  +--ro prefix-length?   uint8
        |     |  +--ro type?            ipv4-address-type
        |     |  +--ro origin?          ip-address-origin
        |     +--rw vrrp
        |        +--rw vrrp-group* [virtual-router-id]
        |           +--rw virtual-router-id     -> ../config/virtual-router-id
        |           +--rw config
        |           |  +--rw virtual-router-id?        uint8
        |           |  +--rw virtual-address*          oc-inet:ip-address
        |           |  +--rw priority?                 uint8
        |           |  +--rw preempt?                  boolean
        |           |  +--rw preempt-delay?            uint16
        |           |  +--rw accept-mode?              boolean
        |           |  +--rw advertisement-interval?   uint16
        |           +--ro state
        |           |  +--ro virtual-router-id?        uint8
        |           |  +--ro virtual-address*          oc-inet:ip-address
        |           |  +--ro priority?                 uint8
        |           |  +--ro preempt?                  boolean
        |           |  +--ro preempt-delay?            uint16
        |           |  +--ro accept-mode?              boolean
        |           |  +--ro advertisement-interval?   uint16
        |           |  +--ro current-priority?         uint8
        |           +--rw interface-tracking
        |              +--rw config
        |              |  +--rw track-interface*      -> /oc-if:interfaces/interface/name
        |              |  +--rw priority-decrement?   uint8
        |              +--ro state
        |                 +--ro track-interface*      -> /oc-if:interfaces/interface/name
        |                 +--ro priority-decrement?   uint8
        +--rw proxy-arp
        |  +--rw config
        |  |  +--rw mode?   enumeration
        |  +--ro state
-       |     +--ro mode?   enumeration
+       |  |  +--ro mode?   enumeration
+       |  +--rw manual-ip-prefixes
+       |     +--rw manual-ip-prefix* [prefix]
+       |        +--rw prefix    -> ../config/prefix
+       |        +--rw config
+       |        |  +--rw prefix?   oc-inet:ipv4-prefix
+       |        +--ro state
+       |           +--ro prefix?   oc-inet:ipv4-prefix
        +--rw neighbors
        |  +--rw neighbor* [ip]
        |     +--rw ip        -> ../config/ip
        |     +--rw config
        |     |  +--rw ip?                   oc-inet:ipv4-address
        |     |  +--rw link-layer-address    oc-yang:phys-address
        |     +--ro state
        |        +--ro ip?                   oc-inet:ipv4-address
        |        +--ro link-layer-address    oc-yang:phys-address
        |        +--ro origin?               neighbor-origin

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[gemini-code-assist]

Code Review

This pull request updates the OpenConfig IPv4 proxy ARP model to version 3.10.0, introducing a 'MANUAL' mode and a corresponding 'manual-ip-prefixes' list for explicit prefix configuration. The review feedback suggests improving the clarity of the documentation by explicitly referring to 'proxy ARP mode' in the descriptions of the new configuration elements to ensure consistency and avoid ambiguity.

[gemini-code-assist]

Clarify that "mode" refers to the "proxy ARP mode" in the description for better readability and consistency with other parts of the model.

Suggested change

	"IPv4 prefix for which proxy ARP replies are sent when
	mode is MANUAL.";
	"IPv4 prefix for which proxy ARP replies are sent when the
	proxy ARP mode is MANUAL.";

[gemini-code-assist]

Clarify that "mode" refers to the "proxy ARP mode" in the description to avoid ambiguity.

Suggested change

	"Collection of IPv4 prefixes for which proxy ARP replies are
	sent when mode is MANUAL.";
	"Collection of IPv4 prefixes for which proxy ARP replies are
	sent when the proxy ARP mode is MANUAL.";

[dplore]

Please add more description in the yang model of what the MANUAL mode is. Is this a filter of which client IP address the device will respond to ARP requests when doing proxy-ARP?

The Ciena link only goes to the main website. Please add a link to documentation describing the feature being added.