inproc support is special in zmq: in particular it completely bypasses
the auth layer, which causes problems in OxenMQ because we assume that a
message will always have auth information (set during initial connection
handshake).
This adds an "always-on" inproc listener and adds a new `connect_inproc`
method for a caller to establish a connection to it.
It also throws exceptions if you try to `listen_plain` or `listen_curve`
on an inproc address, because that won't work for the reasons detailed
above.
The recent PR that revamped the connection IDs missed a case when
connecting to service nodes where we store the SN pubkey in peers, but
then fail to find the peer when we look it up by connection id.
This adds the required tracking to fix that case (and adds a test that
fails without the fix here).
The existing code was overly complicated by trying to track indices in
the `connections` vector, which complication happening because things
get removed from `connections` requiring all the internal index values
to be updated. So we ended up with a connection ID inside the
ConnectionID object, plus a map of those connection IDs to the
`connections` index, and need a map back from indices to ConnectionIDs.
Though this seems to work usually, I recently noticed an
oxen-storage-server sending oxend requests on the wrong connection and
so I suspect there is some rare edge cases here where a failed
connection index might not be updated properly.
This PR simplifies the whole thing by making getting rid of connection
ids entirely and keeping the connections in a map (with connection ids
that never change). This might end up being a little less efficient
than the vector, but it's unlikely to matter and the added complexity
isn't worth it.
Jason Rhinelander