[Steam Flatpak] VAC server timeout occurs randomly in the middle of games

[saori-yuko]

Your system information

Operating System Version:
Freedesktop.org SDK 23.08 (Flatpak runtime) (64 bit)
Kernel Name: Linux
Kernel Version: 6.1.55
X Server Vendor: The X.Org Foundation
X Server Release: 12301002
X Window Manager: GNOME Shell
Steam Runtime Version: steam-runtime_0.20230801.56012

CPU Brand: Intel(R) Core(TM) i9-10940X CPU @ 3.30GHz
Driver: AMD AMD Radeon RX 6700 XT (navi22, LLVM 16.0.6, DRM 3.49, 6.1.55)

• Have you checked for system updates?: Yes

Please describe your issue in as much detail as possible:

Expect results: I do not get disconnected from the game do to VAC timeout Actual results: I get disconnected from the game with VAC timeout

Steps for reproducing this issue:

1. Play CS2
2. Join an online game
3. Play for an hour or so

[saori-yuko]

This issue does not occur in the non-flatpak version of steam

"NixOS 23.05 (Stoat)" (64 bit)
Kernel Name: Linux
Kernel Version: 6.1.55
X Server Vendor: The X.Org Foundation
X Server Release: 12301002
X Window Manager: GNOME Shell
Steam Runtime Version: steam-runtime_0.20230801.56012

[benaryorg]

Same issue here, although it has been an issue for me since CS:GO days, and I can not test against a native version of Steam (since I don't trust Steam or the games enough to let it out of the sandbox).

Last time I ran a tcpdump in hopes of finding something and indeed shortly before the DC/timeout my computer sent almost three dozen duplicate Acks to let the remote server know that a single packet was dropped and needs to be resent, however the server just kept sending the regular TCP stream packets and did not provide the missing packet. After about 100ms of getting packets further down the stream and sending the dup-ack packets the timeout occurred. Looking at the initial TCP handshake and the TLS handshake on that connection it seems to me that the round-trip time seems to have been pretty much 100ms. So either this is a fluke, or even entirely unrelated traffic, or the VAC system is very sensitive to packet loss in this specific setup. That alone however would still not explain why this only happens in a Flatpak version of Steam.

I can provide the pcap if required.

[sawb]

This issue does not occur in the non-flatpak version of steam

"NixOS 23.05 (Stoat)" (64 bit)
Kernel Name: Linux
Kernel Version: 6.1.55
X Server Vendor: The X.Org Foundation
X Server Release: 12301002
X Window Manager: GNOME Shell
Steam Runtime Version: steam-runtime_0.20230801.56012

This issue frequently occurs on Non-flatpak steam for me.

[ech0devv]

Still having this issue w/ steam runtime

[g572staem]

Tangentially related, same symptoms. (NOT a duplicate, duplicate issues occur in the same time frame). https://github.com/ValveSoftware/steam-for-linux/issues/10920

( Ubuntu 20.04 LTS, Nvidia. OS does not have boffin nonsense going on, very vanilla install. )