Rewrite submit_block relay communication to support SSZ and JSON#468
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content negotiation. Includes: - SSZ-first request encoding with JSON fallback on 406/415 - Content-Type and Eth-Consensus-Version header handling - Fork-aware SSZ decoding for relay responses - MIME parameter tolerance on relay response Content-Type - v2 to v1 fallback forwards payload to BN (prevents silent block loss) - V2 fallback metric counter - Comprehensive submit_block integration tests for both encodings
- L275 pass headers by ref - L350 / L386 use content_type_header - L508 drop redundant to_string - bump transitive dep versions for CI
- JsonEncode error instead of unwrap() for both submit_block and register_validators - json timeout budget now accounts for prior ssz attempt
…n v1-only relays Content negotiation (Builder API): - Missing Accept defaults the response to JSON instead of inheriting the request Content-Type; request and response encodings are independent. - v2 succeeds with an empty 202 and has no body to negotiate, so it skips Accept entirely -- a bad Accept no longer 406s a v2 submission before it reaches a relay. - An unrecognized request Content-Type returns 415 instead of 400. - Always request SSZ from the relay (JSON fallback) rather than mirroring the caller's format: PBS decodes and re-validates the payload and the route re-encodes to the BN's Accept regardless, so SSZ is the fastest wire format on the relay hop. Fail loud on v1-only relays: - Drop the v2->v1 fallback. It returned the relay's v1 payload as a 200 body, but a v2 caller (Lighthouse, Prysm) requires exactly 202 and never reads the body, so the block was silently dropped. PBS cannot publish the payload itself, so a relay that 404s v2 now fails loud (RELAY_V2_UNSUPPORTED) and other relays still get a chance.
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Summary
Rewrites submit_block relay communication to support SSZ and JSON content negotiation.
What's in this PR
V2_FALLBACK_TO_V1metric counter for observabilityReview notes
The v2→v1 fallback behavior is an intentional change from the previous code which silently discarded the v1 payload. The beacon node needs the unblinded execution payload to broadcast the block (returning an empty 202 on fallback would cause silent block loss).
Part 3 of 4: SSZ types → get_header → submit_block → validation bypassing
Attribution
This work builds on the SSZ builder flow originally implemented by @eserilev
in #252 and ported to the current codebase by @jclapis in #403.
Co-authored-by: Eitan Seri-Levi eserilev@ucsc.edu
Co-authored-by: Joe Clapis jclapis@outlook.com