Future light client protocol extensions may include data from the block
in addition to data from the state, e.g., `ExecutionPayloadHeader`.
To prepare for this, also pass the block to the corresponding functions.
In practice, blocks access is easier than historic state access, meaning
there are no practical limitations due to this change.
For LC gossip, the documentation did not specify what slot number to use
for deriving the gossip objects. This missing documentation is now added
to document using `attested_header.slot`.
While the current Altair specs define structures to aid light client
development, one missing key aspect is the network protocol definition.
Certain implementations have started defining their own REST based APIs,
e.g., Lodestar at https://github.com/ChainSafe/lodestar/blob/master/packages/api/src/routes/lightclient.ts
While such APIs are useful, REST does not seem to be the ideomatic
choice as the sole API available at such a low level for Ethereum.
This patch introduces a libp2p based protocol to allow light clients to
sync to the latest `BeaconBlockHeader` in a trustless and decentralized
manner, building on top of prior work from:
- @hwwhww at https://github.com/ethereum/consensus-specs/pull/2267
- @jinfwhuang at https://github.com/ethereum/consensus-specs/pull/2786
- Lodestar's REST API (also has an endpoint to fetch merkle proofs!)
Etan Kissling
Michael Sproul
Michael Sproul