Add Want-Repr-Digest / Repr-Digest support to ledger-chunk endpoints

[Copilot]

• Implement Want-Repr-Digest / Repr-Digest in fill_range_response_from_file
• Add snapshot endpoint test (test_snapshot_repr_digest)
• Apply brace style suggestion
• Apply doc suggestion for example header
• Update parse_want_repr_digest comment to reflect best-effort/ignore behavior
• Add gcount() >= range_end check, return 500 on short read
• Return 200 OK (not 206) for GET without Range header; add Range+Digest test cases
• Clarify unsupported algorithms are ignored in doc/changelog/tests
• Default to sha-256 when no supported algorithm matches (RFC 9530 Appendix C.2)
• Return 500 on HEAD path when file read fails with Want-Repr-Digest
• Move parse_want_repr_digest() to src/http/http_digest.h with unit tests
• Move http_digest.h include to top of test file

Closes #7650

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[eddyashton]

@achamayou - Is there a reason this is /ledger-chunk specific, or could we move it inside fill_range_response_from_file to get the same behaviour for /snapshot requests?

[achamayou]

@achamayou - Is there a reason this is /ledger-chunk specific, or could we move it inside fill_range_response_from_file to get the same behaviour for /snapshot requests?

No specific reason, but it's a bit of a questionable coupling, because that behaviour is specifically not affect by the Range? So it seems like a bit of functionality we want for both snapshot and ledger endpoints perhaps (probably more for the latter, where there is a clear use case).

[achamayou]

@copilot could you try to integrate with the fill_range_response_from_file() function, because that already finds, opens, and reads from the file. To compute the repr-digest, you may need to read a longer range, because it's always the digest of the whole file, as opposed to just the range being selected, but in case when the range is the whole file, it's a single read.

And in case where it's a subset, you should be able to use the update_hash() to read what comes before the range, update the digest, what's in range and needs to be set in the body, update the digest, and after the range and update the digest with that too.

That avoids duplicate reads, and means the snapshot endpoint download benefits from the same feature. It will needs it own test as well of course.

[Copilot]

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[achamayou]

@copilot can you try again please?

[Copilot]

@copilot can you try again please?

Moved the Want-Repr-Digest/Repr-Digest handling into fill_range_response_from_file() in d57c8e3 so both /snapshot/{snapshot_name} and /ledger-chunk/{chunk_name} endpoints benefit automatically. When a digest is requested, the full file is read once and the range is extracted from it — avoiding duplicate reads. Split the old compute_repr_digest into parse_want_repr_digest() (header parsing) and format_repr_digest() (hash + formatting). Added test_snapshot_repr_digest for snapshot endpoint coverage, and updated docs/changelog to mention both endpoints.

[Copilot]

Pull request overview

Adds RFC 9530 representation digest negotiation to snapshot and ledger-chunk download endpoints so clients can verify downloaded content (and avoid re-downloads) via Want-Repr-Digest / Repr-Digest.

Changes:

• Introduces want-repr-digest / repr-digest header constants and implements digest computation + selection logic in file-serving handlers.
• Updates file-serving responses to include Repr-Digest for GET/HEAD when requested (digest covers full file even with Range).
• Adds E2E tests for snapshots and ledger chunks, plus public documentation and changelog entry.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
include/ccf/http_consts.h	Adds header name constants for Want-Repr-Digest / Repr-Digest.
src/node/rpc/file_serving_handlers.h	Parses Want-Repr-Digest, computes digest, and injects Repr-Digest header for file-serving endpoints.
tests/e2e_operations.py	Adds E2E coverage for Repr-Digest behavior on snapshot and ledger-chunk endpoints.
doc/operations/ledger_snapshot.rst	Documents new request/response header behavior and supported algorithms.
CHANGELOG.md	Records feature addition in the changelog.

[Copilot]

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