feat(n3iwf): add N3IWF-ID support alongside GNB-ID

[andybavier]

Summary

• Extends client.proto with N3iwfId field (backward-compatible addition) and N3IWF_MSG/N3IWF_DISC/N3IWF_CONN message types
• Adds N3iwfId field and SetN3iwfId/RanFindByN3iwfId to the Ran context so N3IWF connections are tracked alongside gNBs
• Updates backend/grpc.go (Send, readFromServer, ConnectToServer) to route messages using N3iwfId when present

Closes #225.

Note: Requires a coordinated update to omec-project/amf to populate N3iwfId in AmfMessage responses for N3IWF NGSetup flows. The proto change is backward-compatible — old AMF deployments leave N3iwfId empty and all existing gNB paths are unaffected.

Testing

• Added context/context_test.go with tests for SetN3iwfId, RanFindByN3iwfId, and the updated RanID() formatting (9 subtests, all pass)

Post-Deploy Monitoring & Validation

• Logs to watch: received N3iwfId: <id> for GnbIpAddress: <ip> from NF — confirms AMF is populating the new field for N3IWF connections
• Failure signal: N3IWF NGAP messages result in couldn't fetch sctp connection log lines — indicates AMF side has not yet been updated
• Rollback: sctplb is safe to deploy first; with an old AMF the N3iwfId field will be empty and all gNB routing is unaffected
• Validation window: After AMF update is deployed, verify N3IWF NGSetup completes end-to-end

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🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds N3IWF-ID support to sctplb so it can track and route N3IWF-associated NGAP traffic alongside existing gNB-ID routing, including proto/schema updates and corresponding context + gRPC backend routing changes.

Changes:

• Extend client.proto (and generated Go bindings) with N3iwfId fields and new N3IWF_* message types.
• Add N3iwfId storage + lookup (SetN3iwfId, RanFindByN3iwfId) and update RanID() formatting/precedence.
• Update gRPC backend send/receive paths to bind and route by N3iwfId when present, with added unit tests for context changes.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
client.proto	Adds N3iwfId fields and N3IWF msg types to the API schema.
sdcoreAmfServer/client.pb.go	Regenerates Go protobuf types for new fields/enums.
sdcoreAmfServer/client_grpc.pb.go	Regenerates Go gRPC stubs for the updated proto.
context/context.go	Extends Ran context with N3iwfId, adds setter/lookup, updates RanID().
context/context_test.go	Adds unit tests covering new context behaviors.
backend/grpc.go	Routes/binds using N3iwfId when present; updates Send/readFromServer/ConnectToServer paths.

Comments suppressed due to low confidence (1)

backend/grpc.go:63

• The log says the RAN details are "not sending" when neither RanId nor N3iwfId is set, but the code still calls stream.Send(&req) (and then waits on stream.Recv()). This can send INIT messages with no identifier and can also block on Recv unnecessarily. Consider skipping the send/recv for this candidate (e.g., return early from the Range callback) when both IDs are absent.

			if candidate.N3iwfId != nil {
				req.N3IwfId = *candidate.N3iwfId
			} else if candidate.RanId != nil {
				req.GnbId = *candidate.RanId
			} else {
				logger.AppLog.Infof("ran connection %v exists without RanId or N3iwfId, so not sending this ran details to NF",
					candidate.GnbIp)
			}
			if err := stream.Send(&req); err != nil {
				logger.AppLog.Warnln("can not send:", err)

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