Broadcasts being returned to sender.

[aheschl1]

When broadcasting, there is no mechanism to stop messages being returned to sender. This adds extra RTT to the proto.
This change will require updates to numerous test cases, and the broadcast loop on communications.rs.

[aheschl1]

Broadcasts are done in https://github.com/aheschl1/blockchain/blob/main/src/protocol/communication.rs#L18

Processes are registered for broadcast by adding to the queue at https://github.com/aheschl1/blockchain/blob/main/src/nodes/node.rs#L102

Currently the only rule that exists for "do not broadcast" is not to rebroadcast. This is done by adding the hash of a message to the mutexed HashSet at https://github.com/aheschl1/blockchain/blob/main/src/nodes/node.rs#L104 . (this is somewhat being abused and leads to this issue)

In order to eliminate retransmission, the https://github.com/aheschl1/blockchain/blob/main/src/nodes/node.rs#L102 can be converted to a Sender<(Message, Option<Peer>)>, where the Some(peer) indicates that we are broadcasting on behalf of peer. Then, at https://github.com/aheschl1/blockchain/blob/main/src/nodes/node.rs#L570 broadcast could be modified to have an exclude list, or broadcast_with_exclude could be added. The node implmentation is in the same file, and you can easy filter Peer as they are Eq and PartialEq. Peer is at https://github.com/aheschl1/blockchain/blob/main/src/nodes/peer.rs

Would require numerous changes across files; however, setting the second touple argument to None would not be a breaking change in any case. Furthermore, some testcases will fail because they count how many things are broadcasted, but in these, only 2 nodes are involved. These testcases can just be adjusted to expect one less broadcast.

[aheschl1]

@DiscordJim

[aheschl1]

Links are wrong now; however, the file paths can be followed