zebra: add debug in route install around nhg not ready

[chiragshah6]

debug log:

2026/03/20 01:41:09.401823 ZEBRA: [ZSM84-3K06X] dplane_ctx_route_init
route 81.0.0.5/32 op ROUTE_UPDATE nhg id 225 flags 0x5 nh 27.0.0.1 if 4
vrfid 0 not installed nor queued

Tracepoint:

2026-03-20T01:35:06.111 frr_zebra:dplane_ctx_route_kernel_nhg_not_ready
{'op': 2, 'nhe_id': 141, 'nhe_flags': 515, 'vrf_id': 41}
2026-03-20T01:35:10.366 frr_zebra:dplane_ctx_route_kernel_nhg_not_ready
{'op': 2, 'nhe_id': 73529432, 'nhe_flags': 3, 'vrf_id': 31}
2026-03-20T01:35:10.366 frr_zebra:dplane_ctx_route_kernel_nhg_not_ready
{'op': 2, 'nhe_id': 73529444, 'nhe_flags': 3, 'vrf_id': 41}

[greptile-apps]

Greptile Summary

This PR adds observability instrumentation to the zebra dataplane route install path — specifically for the case where a kernel nexthop group (NHG) is not yet installed or queued when a route install/update is attempted.

Changes:

• zebra/zebra_dplane.c: Before returning ENOENT when a kernel NHG is not ready, a new frrtrace call fires the new LTTng tracepoint and a zlog_debug message (gated on IS_ZEBRA_DEBUG_DPLANE_DETAIL or IS_ZEBRA_DEBUG_RIB_DETAILED) logs the route node, operation, NHG id, NHG flags, and first nexthop to aid in diagnosing stalled route installs.
• zebra/zebra_trace.h: Defines the new dplane_ctx_route_kernel_nhg_not_ready LTTng tracepoint with four scalar fields (op, nhe_id, nhe_flags, vrf_id). The tracepoint definition uses 4-space indentation instead of the tab indentation used by every other block in this file — since the file has a /* clang-format off */ guard, this won't be auto-corrected.

Confidence Score: 5/5

• This PR is safe to merge; it adds debug/trace instrumentation only and does not change any control-flow logic.
• The only functional change is adding a tracepoint call and a guarded debug log before an already-existing return ENOENT. No existing behavior is altered. The sole issue is a cosmetic indentation inconsistency in zebra_trace.h.
• zebra/zebra_trace.h — indentation style inconsistency (spaces vs. tabs)

Important Files Changed

Filename	Overview
zebra/zebra_dplane.c	Adds an frrtrace call and a conditional zlog_debug log before returning ENOENT when a kernel NHG is not installed or queued. Logic is correct and consistent with surrounding debug patterns in the file.
zebra/zebra_trace.h	Adds a new dplane_ctx_route_kernel_nhg_not_ready LTTng tracepoint with four scalar fields. The tracepoint definition is logically correct but uses 4-space indentation instead of the tab indentation used by all other tracepoint blocks in the file.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[dplane_ctx_route_init called\nop = INSTALL or UPDATE] --> B{HAVE_NETLINK?}
    B -- No --> E[Continue normal init]
    B -- Yes --> C{kernel_nexthops_enabled\nAND op is INSTALL/UPDATE?}
    C -- No --> E
    C -- Yes --> D{NHG installed\nOR queued?}
    D -- Yes --> E
    D -- No --> F["frrtrace(dplane_ctx_route_kernel_nhg_not_ready)\n[NEW]"]
    F --> G{"IS_ZEBRA_DEBUG_DPLANE_DETAIL\nOR IS_ZEBRA_DEBUG_RIB_DETAILED?\n[NEW]"}
    G -- Yes --> H["zlog_debug: route/op/nhg id/flags/nh\n[NEW]"]
    G -- No --> I[return ENOENT]
    H --> I
    E --> J[return AOK]

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Prompt To Fix All With AI

This is a comment left during a code review.
Path: zebra/zebra_trace.h
Line: 465-479

Comment:
**Inconsistent indentation (spaces vs. tabs)**

The new `TRACEPOINT_EVENT` block uses 4-space indentation, while every other tracepoint event in this file uses tab indentation. Since the file has a `/* clang-format off */` directive at line 40, clang-format won't auto-correct this — the inconsistency will persist as-is. The block should use tabs to match the surrounding code.

```suggestion
TRACEPOINT_EVENT(
	frr_zebra,
	dplane_ctx_route_kernel_nhg_not_ready,
	TP_ARGS(
		enum dplane_op_e, op,
		uint32_t, nhe_id,
		uint32_t, nhe_flags,
		vrf_id_t, vrf_id),
	TP_FIELDS(
		ctf_integer(uint32_t, op, op)
		ctf_integer(uint32_t, nhe_id, nhe_id)
		ctf_integer(uint32_t, nhe_flags, nhe_flags)
		ctf_integer(vrf_id_t, vrf_id, vrf_id)
	)
)
```

How can I resolve this? If you propose a fix, please make it concise.

_{Last reviewed commit: "zebra: add debug rou..."}