ReadPayload is called with an invalid payload on client when it uses a predict spawn

[Navlyc]

General
Unity version: 2022.3.22f1
Fish-Networking version: 4.6.2
Discord link: https://discord.com/channels/424284635074134018/923983677980045382/1347684214363000832

Description
When I use a predict spawn a ReadPayload is called on the spawned object with an invalid payload on client owner of the spawn. I mean the payload doesn't match with what I write in the WritePayload function. After an investigation the payloadLength in ManagedObjects.Spawning.cs line 465 seems corrupted, I get sometime negative or huge values (-1828650512, 1308688880, -234814992).

Replication
Steps to reproduce the behavior:

1. Add Debug.Log(payloadLength.Value) in ManagedObjects.Spawning.cs line 466
2. Call a predict spawn (without pool in my case)
3. Look the console log on the client owner of the spawn and notice the value, it's invalid (negative or huge values like -1828650512, 1308688880, -234814992).

Expected behavior
ReadPayload matching with WritePayload.

Screenshots
I believe I found a fix

We need to add payload.Count (or segmentReader.Length) in last parameter of ReadPayload called in ClientObject.cs line 423 because this function believes the length is in the segmentReader and will read the first bytes of the payload instead. When the value is positive the following code is executed with an offseted reader giving a corrupted payload.

[FirstGearGames]

Did you have a project file to this?

I assume this can only be tested when spawning as client only?

[Navlyc]

Hello, I'm sorry, I dont have sample project for this. Yes you need just to predict spawn as client. Server can be host or not, we get the same issue.

[FirstGearGames]

Hey! I was not able to replicate the issue. I tried with two clients and server, as well two clients and host, as well one client + host/server. Payload length has always returned 0 as expected.

Here's my test project.

Steps:
Open 2 or 3 editors. Start one as server, rest as client. Predicted spawn occurs when client connects.

payloadbug.zip

[Navlyc]

Hello, sorry my description was probably not clear. I updated your sample with this code in ReadWritePayload.cs :

`
using FishNet.Connection;
using FishNet.Object;
using FishNet.Serializing;
using UnityEngine;

public class ReadWritePayload : NetworkBehaviour
{
const int PAYLOAD_TEST = 1000;

public override void WritePayload(NetworkConnection connection, Writer writer)
{
    writer.WriteInt32(PAYLOAD_TEST);
    Debug.Log("WritePayload " + PAYLOAD_TEST);
}

public override void ReadPayload(NetworkConnection connection, Reader reader)
{
    int payloadTest = reader.ReadInt32();
    Debug.Log("ReadPayload " + payloadTest);

    if (payloadTest != PAYLOAD_TEST)
    {
        Debug.LogError($"Not expected payload {payloadTest}, expected {PAYLOAD_TEST}");
    }
}

}
`
and I get the issue in the console :

I added the Debug.Log($"ReadPayload Length : {payloadLength}"); in ManagedObjects.Spawning.cs line 466.

[Navlyc]

And the following screenshot is what I get with my shared fix above :

[FirstGearGames]

Thanks, I took a better look and your solution seems appropriate. The size was already parsed into the array segment thus can be passed into the ReadPayload method.

I used your solution except modified to reader.Length for consistency reasons. This will be resolved in the next release.

If you wanted to submit a PR for the fix to get credit please feel free to.

[Navlyc]

Thanks you, it's OK. You can submit.