Support SSZ request body for POST /beacon/blocks endpoints (v1 & v2)

[jimmygchen]

Description

The /eth/v1/beacon/blocks and /eth/v2/beacon/blocks beacon api endpoint supports both ssz and json bodies (spec here). However, Lighthouse only supports json. This can cause missed blocks when a non-lighthouse VC hits that api with a ssz payload. Moreover, we return a 500 error when we should be returning 415 (The supplied content-type is not supported).

There is a separate issue for blinded blocks endpoints in #4262

Version

stable

Steps to resolve

Add SSZ request body support, use the supplied Eth-Consensus-Version HTTP request header to decode the SSZ bytes.

[eserilev]

would adding ssz request body support for these endpoints look something like:

defining post routes where the Content-Type header matches application/octet-stream

in beacon_node/http_api/src/lib.rs starting around line 3879

let routes = warp::get()
.and( ... )
.boxed()
.uor(
    warp::post().and(
       warp::header::exact("Content-Type", "application/octet-stream").and(
           post_beacon_blocks
               .uor(post_beacon_blocks_v2_ssz)
               .uor(post_beacon_blocks_v1_ssz),
                ),
            ),
      )
.uor(...)

then parsing the request body as ssz and executing the post beacon block logic in the relevant 'route handler' i.e. in post_beacon_blocks_v2_ssz and post_beacon_blocks_v1_ssz

[jimmygchen]

Hi @eserilev

I don't think we have any endpoint that supports SSZ request body yet, so I'm not exactly sure how it would look like, will probably need to look into the docs.

I think you got the idea though - we do need to define a separate route(s) for this. In your above example, I think the existing post_beacon_blocks json endpoint should probably be placed outside the application/octet-stream header matcher, otherwise it won't route the json requests to that handler. (I could be wrong though)

[eserilev]

great, I think i have a general understanding of this feature. I'd be happy to work on it

[jimmygchen]

Completed in #4479 🎉 Thanks @eserilev