Closes#158.
As discussed on the issue, this makes it possible to safely serialize
data into hashes, and encourages serializable data to make illegal
states unrepresentable.
The previous implementation failed when timestamps were duplicated between
peers, because there was not a 1-1 relationship between timestamps and peers.
This field is called `services` in Bitcoin and Zcash, but because we use
that word internally for other purposes, calling it `PeerServices`
disambiguates the meaning to "the services advertised by the peer",
rather than, e.g., a `tower::Service`.
* 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.
The `NetworkAddress` type was a `(Services, SocketAddr)` pair as used in the
`version` handshake message, described as the `net_addr` struct in the Bitcoin
wiki protocol documentation. However, all of the other uses of the `net_addr`
struct are a `(Timestamp, Services, SocketAddr)` pair (where the timestamp is
the last-seen time of the peer), and the timestamp is omitted only during the
`version` messages, which are used only during the handshake, so it seems
better to include the timestamp field and omit it during serialization of
`version` packets.
Jane Lusby
Henry de Valence