[Feature Request] Add gNMI target prefix support in TargetConnectionProfile for SONiC compatibility

[reinaldosaraiva]

Summary

SONiC switches require the gNMI target field in the SetRequest prefix to be set to OC-YANG for write operations. Currently, TargetConnectionProfile does not expose this field, making SDC incompatible with SONiC gNMI SET operations.

Environment

• SDC Version: Latest (config-server, data-server)
• Device: Dell SONiC Enterprise 4.4.1
• Protocol: gNMI (port 8080, JSON_IETF encoding)
• Kubernetes: KinD v1.32.0

Problem Description

When using SDC to configure SONiC switches via gNMI, all Config CRDs fail with:

status:
  conditions:
  - reason: Unrecoverable
    message: "runtime error: index out of range [-1]"

After investigation, we discovered that SONiC gNMI requires the -xpath_target OC-YANG parameter for SET operations:

# This WORKS directly on SONiC:
gnmi_set -insecure -username admin -password admin \
  -target_addr 127.0.0.1:8080 \
  -xpath_target OC-YANG \
  -update /openconfig-system:system/config:@./hostname.json

The -xpath_target maps to the target field in the gNMI Path.prefix:

message Path {
  string target = 1;  // <-- This field needs to be configurable
  string origin = 2;
  repeated PathElem elem = 3;
}

Current TargetConnectionProfile Spec

The current TargetConnectionProfile for gNMI does not have a target field:

apiVersion: inv.sdcio.dev/v1alpha1
kind: TargetConnectionProfile
metadata:
  name: gnmi-sonic
  namespace: sdc
spec:
  protocol: gnmi
  port: 8080
  encoding: JSON_IETF
  skipVerify: true
  connectRetry: 30s
  timeout: 30s
  includeNS: true
  # Missing: target or prefixTarget field

Proposed Solution

Add a new field to TargetConnectionProfileSpec for gNMI:

// TargetConnectionProfileSpec
type TargetConnectionProfileSpec struct {
    // ... existing fields ...

    // GNMITarget specifies the target field in gNMI prefix
    // Used by SONiC (OC-YANG) and potentially other vendors
    // +optional
    GNMITarget *string `json:"gnmiTarget,omitempty"`
}

Example usage:

apiVersion: inv.sdcio.dev/v1alpha1
kind: TargetConnectionProfile
metadata:
  name: gnmi-sonic
spec:
  protocol: gnmi
  port: 8080
  encoding: JSON_IETF
  skipVerify: true
  gnmiTarget: "OC-YANG"  # <-- New field

References

• SONiC gNMI Usage Examples
• OpenConfig gNMI Specification - Path.target
• SONiC Management Framework

Impact

This would enable SDC to work with:

• Dell SONiC Enterprise
• SONiC Community Edition
• Any gNMI implementation requiring custom target prefix

Workaround

Currently using gnmic directly with --target OC-YANG parameter, bypassing SDC.

Additional Context

We successfully validated that SONiC gNMI SET works when using the correct target:

# Test result: SUCCESS
docker exec telemetry gnmi_set -insecure -username admin -password admin \
  -target_addr 127.0.0.1:8080 -xpath_target OC-YANG \
  -update /openconfig-system:system/config:@/tmp/hostname.json

# Response: op:UPDATE  path:openconfig-system:system/config
# Hostname changed from "sonic" to "mgc-spine-1"

The configuration is correct; only the gNMI target prefix is missing.

[henderiw]

Should we not set it by default? Meaning without configuration? I believe most devices I interacted with support the target field. We could use the target name which we use to configure the datastore in the data server for this e.g.

This is a combination and name and namespace for the Target CR. What I am suggesting is to support this w/o configuration, since configuration is always cumbersome in my view.

[henderiw]

We are discussing the proposal here as it covers multiple repos.

sdcio/.github#16