This patch adds the `eth/65` protocol, documented at
https://github.com/ethereum/devp2p/blob/master/caps/eth.md.
This is an intentionally simple patch, designed to not break, change or depend
on other functionality much, so that the "_old_ sync" methods can be run
usefully again and observed. This patch isn't "new sync" (a different set of
sync algorithms), but it is one of the foundations.
For a while now Nimbus Eth1 only supported protocol `eth/63`. But that's
obsolete, and very few nodes still support it. This meant Nimbus Eth1 would
make slow progress trying to sync, as most up to date clients rejected it.
The current specification is `eth/66`, and the functionality we really need is
in `eth/64`.
So why `eth/65`?
- `eth/64` is essential because of the `forkId` feature. But `eth/64` is on
its way out as well. Many clients, especially the most up to date Geth
running the current hard-forks (Berlin/London) don't talk `eth/64` any more.
- `eth/66` is the current specification, but some clients don't talk `eth/66`
yet. We'd like to have the best peer connectivity during tests, and
currently everything that talks `eth/66` also talks `eth/65`.
- Nimbus Eth1 RLPx only talks one version at a time. (Without changes to the
RLPx module. When those go in we'll add `eth/64..eth/66` for greater peer
reach and testing the `eth/66` behaviour. For simplicity and decoupling,
this patch contains just one version, the most useful.)
What are `eth/64` and `eth/65`?
- `eth/64` (EIP-2364) added `forkId` which allows nodes to distinguish between
Ethereum (ETH) and Ethereum Classic (ETC) blockchains, which share the same
genesis block. `forkId` also protects the system when a new hard fork is
going to be rolled out, by blocking interaction with out of date nodes. The
feature is required nowadays.
We send the right details to allow connection (this has been tested a lot),
but don't apply the full validation rules of EIP-2124/EIP-2364 in this patch.
It's to keep this patch simple (in its effects) and because those rules have
consequences best tested separately. In practice the other node will reject
us when we would reject it, so this is ok for testing, as long as it doesn't
get seriously deployed.
- `eth/65` added more efficient transaction pool methods.
- Then a later version of `eth/65` (without a new number) added typed
transactions, described in [EIP-2976](https://eips.ethereum.org/EIPS/eip-2976).
Why it's moved to `nimbus-eth1`:
- Mainly because `eth/64` onwards depend on the current state of block
synchronisation, as well as the blockchain's sequence of hard-fork block
numbers, both of which are part of `nimbus-eth1` run-time state. These
aren't available to pure `nim-eth` code. Although it would be possible to
add an API to let `nimbus-eth1` set these numbers, there isn't any point
because the protocol would still only be useful to `nimbus-eth1`.
Signed-off-by: Jamie Lokier <jamie@shareable.org>
Jamie Lokier