bgpd: Format IGP Router-ID in BGP-LS NLRI based on protocol

[cscarpitta]

RFC 9552 defines the IGP Router-ID as an opaque value whose interpretation depends on the combination of Protocol-ID and field length. The IGP Router-ID is currently always emitted as a hex-dot string, ignoring both fields.

Replace the generic hex-dot loop with protocol-aware formatting:

• IS-IS (6 or 7 bytes): %pPN
• OSPF non-pseudonode (4 bytes): %pI4
• DIRECT/STATIC IPv4 (4 bytes): %pI4
• DIRECT/STATIC IPv6 (16 bytes): %pI6

Any unrecognised protocol/length combination is treated as an error and logged via flog_err(EC_BGP_LS_PACKET).

Applied to both the JSON display path (node_desc_to_json) and the string format path (format_node_desc).

[greptile-apps]

Greptile Summary

This PR replaces the generic hex-dot loop for BGP-LS IGP Router-ID display with protocol-aware formatting in both the JSON (node_desc_to_json) and string (format_node_desc) output paths, using %pSY.00/%pPN for IS-IS, %pI4/%pI4:%pI4 for OSPF (including pseudonodes), and %pI4/%pI6 for DIRECT/STATIC, in compliance with RFC 9552.

• The flat uint8_t igp_router_id[16] field is replaced by a typed union (sysid, pseudo_isis, ospf, pseudo_ospf, ipv4, ipv6, raw) across bgp_ls_nlri.h, and all encode/decode/originate/withdraw call sites are updated to use .raw.
• Three inline protocol predicates (bgp_ls_protocol_is_isis, bgp_ls_protocol_is_ospf, bgp_ls_protocol_is_direct_static) are added to bgp_ls.h and used throughout, replacing open-coded protocol_id == OSPFV2 || ... checks.
• Test fixtures are updated to reflect the new IS-IS non-pseudonode representation (0000.0000.0002.00 instead of 0000.0000.0002).

Confidence Score: 5/5

Safe to merge — the union refactor is mechanically consistent across all call sites and all RFC 9552-defined combinations are handled correctly.

All valid protocol/length combinations are handled correctly in both the JSON and format-string paths, including the previously missing OSPF pseudonode case. The VTY display path still omits the 8-byte OSPF pseudonode, but this was a pre-existing gap and not a regression introduced by this PR.

bgpd/bgp_ls_nlri.c — bgp_ls_nlri_display could be brought into parity with the other two output paths by adding the OSPF pseudonode display branch.

Important Files Changed

Filename	Overview
bgpd/bgp_ls.c	Replaced generic hex-dot loop in node_desc_to_json and format_node_desc with protocol+length-aware switch; both paths now correctly handle IS-IS (6/7 byte), OSPF (4/8 byte), DIRECT/STATIC (IPv4/IPv6), falling through to flog_err+ for any unrecognised combination.
bgpd/bgp_ls_nlri.c	Updated bgp_ls_nlri_display and encode/decode helpers to use the new igp_router_id union. The display function dispatches on length only and still has no branch for the 8-byte OSPF pseudonode case, leaving that ID silently unprinted while the parallel JSON and format paths handle it correctly.
bgpd/bgp_ls_nlri.h	Replaced the raw uint8_t[16] array with a named union exposing typed members for type-safe access throughout the codebase.
bgpd/bgp_ls.h	Added three inline protocol predicate helpers to centralise protocol-ID checks.
bgpd/bgp_ls_ted.c	Mechanically updated all memcpy igp_router_id call sites to use .raw and replaced open-coded protocol_id checks with bgp_ls_protocol_is_ospf().

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[IGP Router-ID present] --> B{protocol_id + igp_router_id_len}
    B -->|IS-IS len==6| C[pSY.00]
    B -->|IS-IS len==7| D[pPN]
    B -->|OSPF len==4| E[pI4]
    B -->|OSPF len==8| F[pI4:pI4]
    B -->|DIRECT/STATIC len==4| G[pI4]
    B -->|DIRECT/STATIC len==16| H[pI6]
    B -->|unrecognised| I[flog_err]
    C --> J[node_desc_to_json / format_node_desc]
    D --> J
    E --> J
    F --> J
    G --> J
    H --> J
    I --> J
    K[bgp_ls_nlri_display length-only] -->|len==4| L[Router ID IPv4]
    K -->|len==6| M[ISO Node ID pSY.00]
    K -->|len==7| N[ISO Node ID pPN]
    K -->|len==16| O[Router ID IPv6]
    K -->|len==8| P[silent - not displayed]

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Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
bgpd/bgp_ls_nlri.c:6271-6284
**OSPF pseudonode silently omitted in `bgp_ls_nlri_display`**

`bgp_ls_nlri_display` dispatches on length only (4 / 6 / 7 / 16 bytes) and has no branch for `BGP_LS_IGP_ROUTER_ID_OSPF_PSEUDO_LEN` (8 bytes). Any OSPF Designated Router NLRI received from a BGP-LS peer will silently produce no IGP Router-ID line in the VTY output, even though both `node_desc_to_json` and `format_node_desc` now correctly format the 8-byte pseudo-OSPF case with `pseudo_ospf.router_id` + `pseudo_ospf.ifaddr`. This creates a display gap between the three output paths. Consider adding the corresponding `else if (... == BGP_LS_IGP_ROUTER_ID_OSPF_PSEUDO_LEN)` branch here (and in the remote-node block below) to keep the three output paths consistent.

_{Reviews (4): Last reviewed commit: "tests: Apply clang-format to SRv6 BGP-LS..." | Re-trigger Greptile}

[cscarpitta]

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[cscarpitta]

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[cscarpitta]

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