bgpd: register ENCAP and LINK_STATE in attr_flags_values table

[guoguojia2021]

The attr_flags_values array was missing entries for BGP_ATTR_ENCAP (type 23) and BGP_ATTR_LINK_STATE (type 29). Without a registered entry, bgp_attr_flag_invalid() returns false early and skips all flag validation for these attributes, allowing malformed UPDATE messages with incorrect Optional/Transitive bits to be silently accepted instead of generating a NOTIFICATION.

Add:

• BGP_ATTR_ENCAP: Optional + Transitive (RFC 5512)
• BGP_ATTR_LINK_STATE: Optional (RFC 7752 Section 3.3.1, RFC 9552 Section 4)

[greptile-apps]

Greptile Summary

Fixes a flag-validation gap in bgp_attr_flag_invalid() where BGP_ATTR_ENCAP (type 23) and BGP_ATTR_LINK_STATE (type 29) had no entries in attr_flags_values[], causing the function to hit the early-exit == 0 guard and skip all flag checks for these attribute types.

• Adds [BGP_ATTR_ENCAP] = BGP_ATTR_FLAG_OPTIONAL | BGP_ATTR_FLAG_TRANS (Optional+Transitive, per RFC 5512).
• Adds [BGP_ATTR_LINK_STATE] = BGP_ATTR_FLAG_OPTIONAL (Optional non-transitive, per RFC 9552 §4 / RFC 7752 §3.3.1).

Confidence Score: 5/5

Safe to merge — two-line addition to a designated-initializer table with flag values confirmed against the relevant RFCs.

Both added entries match their RFC-mandated flags: RFC 5512 defines ENCAP (type 23) as Optional+Transitive, and RFC 9552 §4 defines BGP-LS (type 29) as Optional non-transitive. The designated-initializer syntax means no existing entries are disturbed and array bounds are unaffected, since both new indices (23 and 29) fall well within the current array size (largest existing index is BGP_ATTR_PREFIX_SID = 40).

No files require special attention.

Important Files Changed

Filename	Overview
bgpd/bgp_attr.c	Adds BGP_ATTR_ENCAP (type 23, Optional+Transitive per RFC 5512) and BGP_ATTR_LINK_STATE (type 29, Optional non-transitive per RFC 9552) to the attr_flags_values table so bgp_attr_flag_invalid() no longer silently skips flag validation for these two attribute types.

_{Reviews (1): Last reviewed commit: "bgpd: register ENCAP and LINK_STATE in a..." | Re-trigger Greptile}

[riw777]

looks good

[riw777]

@ton31337 should this have a topo test to check that we're not accepting updates with incorrect transitive/optional bits? I can see where this would be useful, but I don't know if it should be included in this pr.

[ton31337]

That would be like a good addition to have a separate topotest to include all well-known attributes to be tested against transitivness, IMO.

[ton31337]

@guoguojia2021, please use real first/last names in the Signed-off-by tag...