Disconnect peers that does not support a feature

[sondreb]

On the OnPartialValidationCompleted, if the network has activated some BIP9 deployment, we will proceed to disconnect nodes that does not support the feature we need.

That means as soon as a blockchain network activates, it will proceed to disconnect those nodes that does not support, e.g. Segwit.

Recent improvement to this code ensures that the nodes will always announce Segwit-capability, but this does not apply to older versions of the software, so they gets disconnected.

Code:

        /// <inheritdoc />
        public void AddDiscoveredNodesRequirement(NetworkPeerServices services)
        {
            IPeerConnector peerConnector = this.PeerConnectors.FirstOrDefault(pc => pc is PeerConnectorDiscovery);
            if ((peerConnector != null) && !peerConnector.Requirements.RequiredServices.HasFlag(services))
            {
                peerConnector.Requirements.RequiredServices |= services;
                foreach (INetworkPeer peer in peerConnector.ConnectorPeers)
                {
                    if (peer.Inbound)
                        continue;

                    if (!peer.PeerVersion.Services.HasFlag(services))
                        peer.Disconnect("The peer does not support the required services requirement.");
                }
            }
        }

Should we change this logic to be similar to proven headers, where an % of connections that doesn't support PH, will still be kept around?

If anyone is deploying with flags, they should consider dropping the last logic of the code above in the file ConnectionManager.cs. Just disable the if check and peer.Disconnect.

[dangershony]

Recent improvement to this code ensures that the nodes will always announce Segwit-capability, but this does not apply to older versions of the software, so they gets disconnected.

Just because of this comment I think we should not make this change because I am not sure the implications of that and if new versions fix it then it will go away pretty soon.