Fix Network Refresh overwriting properties marked with FromHost SyncFlag

[andy013]

Issue: #564

Changes

• Skip [Sync] properties in PostDeserialize during a network refresh.
• Check if connection has control when reading data table after a refresh

Notes

This fix prevents clients who call a network refresh from overwriting Sync properties that have the FromHost SyncFlag.

Currently, [Sync] properties are deserialised from the client's JSON payload, overwriting authoritative host values. ReadDataTable also lacked a check, causing NetList and NetDictionary types to be reset.

Checks are performed on the receiver side. I figured you should always have the receiver check if the sender was allowed to change the value to prevent hacked clients sending data and it just being blindly accepted. You could probably optimise it by also not sending FromHost values on a refresh called by clients.

I've not tested this extensively but it seems to be working in my basic tests. You should review it and make sure I'm not doing anything stupid.

Example

Test project: fromhostbug.zip

Join with a client and observe server console logs. Client calls Network.Refresh every frame which overwrites the values set by the host.

OnStart() sets the Sync FromHost properties like this:

protected override void OnStart()
{
	if ( Networking.IsHost )
	{
		Ammo = 6;
		NetworkList.Add( 1 );
		NetworkList.Add( 2 );
	}
}

Before fix:

[Generic] Wilson [76561197988413004] is connecting	
[Generic] [HOST] Ammo: 0 -> 1	    <--  Ammo set to 1 from the prefab
[Generic] Wilson (2) [76561197988413004] is connected	
[Generic] [HOST] Ammo: 1 -> 6	    <--  OnStart called for host
[Generic] List Changed: 	
[Generic] 1	
[Generic] 2	
[Generic] [HOST] Ammo: 6 -> 1	    <--  Client refresh sets ammo back to prefab value!
[Generic] List Changed: 	
[Generic] List is now empty.        <--  NetList also reset!

After fix:

[Generic] Wilson [76561197988413004] is connecting	
[Generic] [HOST] Ammo: 0 -> 1	
[Generic] Wilson (2) [76561197988413004] is connected	
[Generic] [HOST] Ammo: 1 -> 6	
[Generic] List Changed: 	
[Generic] 1	
[Generic] 2	     <-- Both Ammo and NetList stay set to host values even after client calls Network.Refresh

[andy013]

Should I use ReflectionQueryCache.SyncProperties instead of prop.HasAttribute here?

[lolleko]

We hould really avoid adding new flags to options whenever possible. Is there no other way?