SRv6 SID L3Adj

Table of Content

• Revision

• Scope

• Definitions/Abbreviations

• Overview

• High-Level Design

  • SRv6Orch Changes

• SAI API

• Testing Requirements/Design

  • Unit Test cases

• Open/Action items

• References

Revision

Scope

Extending the SRv6Orch to support the programming of the L3Adj associated with SRv6 uA, End.X, uDX4, uDX6, End.DX4, and End.DX6 behaviors.

Definitions/Abbreviations

Overview

The support of SRv6 has been defined in this HLD: Segment Routing over IPv6 (SRv6) HLD.

The HLD includes several SRv6 behaviors defined in RFC 8986. The Appl DB was extended to support these behaviors.

The Appl DB includes the L3Adj attributes which is used with these behaviors: uA, End.X, uDX4, uDX6, End.DX4, and End.DX6.

The current implementation of SRv6Orch does not process the L3Adj.

In this HLD, we extend the SRv6Orch to process the L3Adj and program it in the ASIC DB.

High-Level Design

The following diagram shows the SRv6Orch workflow to process an SRv6 SID associated with a L3Adj in SONiC:

• SRv6Orch is an APPL_DB subscriber.

• SRv6Orch receives a SRV6_MY_SID_TABLE update notification about the SID. The SID is associated with a L3 adjacency carried in the adj parameter.

• SRv6Orch gets the nexthop ID of the adjacency from NeighOrch.

• SRv6Orch sets the nexthop ID attribute of the SID.

• SRv6Orch invokes the sairedis sai_srv6_api->create_my_sid_entry() API to create the SRv6 SID entry in the ASIC DB.

The next subsections describe the SRv6Orch changes required to support the HLD described above.

SRv6Orch Changes

We extend SRv6Orch to support the programming of the L3Adj associated with uA, End.X, uDX4, uDX6, End.DX4, and End.DX6 behaviors.

When SRv6Orch receives a SID with the adj parameter set, it calls the function neighOrch->hasNextHop() to make sure a nexthop associated with the adjacency exists.

• If the nexthop exists, SRv6Orch invokes the sairedis API sai_srv6_api->create_my_sid_entry() to create an entry SAI_OBJECT_TYPE_MY_SID_ENTRY into the ASIC DB. The SAI_MY_SID_ENTRY_ATTR_NEXT_HOP_ID of the entry is set to the nexthop ID.

• If the nexthop does not exist or is not ready, SRv6Orch keeps the SID in a new data structure called m_pendingSRv6MySIDEntries.

SRv6Orch subscribes to Neighbor Change notifications. When the neighbor becomes ready, SRv6Orch receives a Neighbor ADD notification, walks through the m_pendingSRv6MySIDEntries list and installs all pending SIDs into the ASIC.

We also handle the case when the neighbor associated with a SID is removed from the system. In this case, SRv6Orch receives a Neighbor DELETE notification, removes the SID from the ASIC and adds the SID to the m_pendingSRv6MySIDEntries. When the neighbor comes back, the SID is installed again into the ASIC.

SAI API

The SAI_OBJECT_TYPE_MY_SID_ENTRY object already supports the SAI_MY_SID_ENTRY_ATTR_NEXT_HOP_ID attribute required to associate a L3Adj to a SID.

/**
 * @brief Attribute list for My SID
 */
typedef enum _sai_my_sid_entry_attr_t
{

...
    /**
     * @brief Next hop for cross-connect functions
     *
     * @type sai_object_id_t
     * @flags CREATE_AND_SET
     * @objects SAI_OBJECT_TYPE_NEXT_HOP, SAI_OBJECT_TYPE_NEXT_HOP_GROUP, SAI_OBJECT_TYPE_ROUTER_INTERFACE
     * @allownull true
     * @default SAI_NULL_OBJECT_ID
     * @validonly SAI_MY_SID_ENTRY_ATTR_ENDPOINT_BEHAVIOR == SAI_MY_SID_ENTRY_ENDPOINT_BEHAVIOR_X or SAI_MY_SID_ENTRY_ATTR_ENDPOINT_BEHAVIOR == SAI_MY_SID_ENTRY_ENDPOINT_BEHAVIOR_DX4 or SAI_MY_SID_ENTRY_ATTR_ENDPOINT_BEHAVIOR == SAI_MY_SID_ENTRY_ENDPOINT_BEHAVIOR_DX6 or SAI_MY_SID_ENTRY_ATTR_ENDPOINT_BEHAVIOR == SAI_MY_SID_ENTRY_ENDPOINT_BEHAVIOR_B6_ENCAPS or SAI_MY_SID_ENTRY_ATTR_ENDPOINT_BEHAVIOR == SAI_MY_SID_ENTRY_ENDPOINT_BEHAVIOR_B6_ENCAPS_RED or SAI_MY_SID_ENTRY_ATTR_ENDPOINT_BEHAVIOR == SAI_MY_SID_ENTRY_ENDPOINT_BEHAVIOR_B6_INSERT or SAI_MY_SID_ENTRY_ATTR_ENDPOINT_BEHAVIOR == SAI_MY_SID_ENTRY_ENDPOINT_BEHAVIOR_B6_INSERT_RED
     */
    SAI_MY_SID_ENTRY_ATTR_NEXT_HOP_ID,
...

} sai_my_sid_entry_attr_t;

There is no SAI modification required to support the L3Adj parameter.

Testing Requirements/Design

Unit Test cases

To validate the SRv6 SID L3Adj parameter, we extend the existing test_mysid test cases contained in the test_srv6.py unit test. We create a new SRv6 SID entry associated with a L3 adjacency into the SRV6_MY_SID_TABLE of the Appl DB and we verify that the SID entry is created into the ASIC DB. This test is performed for all the behaviors that require a L3 adjacency: uA, End.X, End.DX4, End.DX6, uDX4, uDX6.

Open/Action items

The changes proposed in this document depend on the following PRs:

• [orchagent]: Extend the SRv6Orch to support the programming of the L3Adj

References

• Segment Routing over IPv6 (SRv6) Network Programming

• Segment Routing over IPv6 (SRv6) HLD