When we perform a handshake with a remote peer, we need to encode the
version messages with a particular network version before we find out
what the remote peer's version preference is. So in addition to having
a CURRENT_VERSION constant (which represents our preference), we need to
have a MIN_VERSION during the handshake (and later to determine whether
we'll talk to the peer at all).
* Replace Version MetaAddr by (Services, SocketAddr).
The version handshake message doesn't include last-seen timestamps for
the address fields, unlike other messages, so instead of modeling the
message data with a `MetaAddr` (which includes a timestamp), we should
just use a tuple.
* Simplify try_read_version implementation.
Because we no longer need to construct fake timestamps for the
`MetaAddr` fields, we don't need to use any of the parsed fields while
parsing later fields, and we can neatly wrap up the entire parsing logic
into a single expression.
* fmt
I didn't have the toolchain-specified `rustfmt` because I was mostly
offline and couldn't download it.
Deirdre Connolly
Henry de Valence