"Network dropped connection on reset" errors on 9p mounts

[lloeki]

Simple: add a 9p share to a VM (here I used the Debian Minimal one from UTM, updated to bullseye), mount it, and try to look at things on the host from the VM.

root@debian:~# mount -t 9p -o trans=virtio share /mnt/Users -o version=9p2000.L
root@debian:~# touch /Users/lloeki/foo
root@debian:~# ls -l /Users/lloeki/foo 
root@debian:~# ls -l /mnt/Users/lloeki
ls: /Users/lloeki/foo: Network dropped connection on reset
-rw-r--r-- 1 root root 0 Sep  9 05:21 /Users/lloeki/foo

This has been reported at lima:

• "Network dropped connection on reset" errors on 9p mounts lima-vm/lima#831

This is caused by a errno mapping issue between Darwin and Linux, fixed in QEMU 7.1:

• https://gitlab.com/qemu-project/qemu/-/issues/1010
• https://gitlab.com/qemu/qemu/-/commit/f5643914a9e8f79c606a76e6a9d7ea82a3fc3e65

So, I guess the fix is "easy": update to QEMU 7.1 :D

Configuration

• UTM Version: 4.0.2 (61)
• macOS Version: 12.5.1 (21G83)
• Mac Chip (Intel, M1, ...): M1

[sbates130272]

Hmmm I am on QEMU 7.1 and I still see this issue. UTM 4.0.5. Ubuntu 22.04 guest.

[sbates130272]

An strace inside the guest yields lots of these:

lgetxattr("/mnt/host/zlib-ng", "security.selinux", 0xaaaafc97e8b0, 255) = -1 ENETRESET (Network dropped connection on reset)

[sbates130272]

@osy can you see if you can replicate this on QEMU 7.1 and then assign as a bug rather than future if the QEMU fix did not resolve this issue (and I do not think it did).

[osy]

@sbates130272 I don’t understand why you say you are on QEMU 7.1 and UTM 4.0.5 since UTM 4.0.5 is running the same QEMU 7.0 as 3.x.

[sbates130272]

@osy OK maybe I am going crazy but I just though UTM used whatever QEMU is available on the path of the host machine. In my case the version of QEMU installed (via homebrew) on my M1 Macbook is 7.1. Am I missing something? I certainly don't see any other qemu-system-aarch64 executables on my system.

batesste@armagh ~ % which qemu-system-aarch64 
/opt/homebrew/bin/qemu-system-aarch64
batesste@armagh ~ % qemu-system-aarch64 --version
QEMU emulator version 7.1.0
Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project developers

[osy]

That’s… that’s not how it works. UTM is based off of QEMU. It doesn’t pull QEMU from your system. It’s built in.

[sbates130272]

@osy doh. Ooops. Thanks for the clarification. Sorry for being such a noob. So I guess I need to wait for UTM to bump to 7.1 and see if this issue goes away.

[sbates130272]

@osy sorry to be a pain but where in the codebase does UTM pull in QEMU? I had a look but I can't find anything obvious. I'd appreciate a pointer. Thanks!

[osy]

https://github.com/utmapp/UTM/blob/main/Documentation/Dependencies.md

[sbates130272]

Thanks @osy for helping me out. That all makes much more sense now. Looking forward to the upgrade to 7.1!

[anttiryt]

this started happening to me after standby/resume from UTM.

[lelegard]

Hi,

Could you please tell when UTM 4.1 will be released? I have the same issue and wait for a fix.

Alternatively, could anyone indicate how to modify the qemu command line which is generated by UTM to use qemu 7.1.0, as installed by Homebrew?

I tried without luck.

• Using QEMU / Export command from UTM, the generated command starts with qemu-system-aarch64 -L /Applications/UTM.app/Contents/Resources/qemu ...
• The default qemu-system-aarch64 is the one from Homebrew (7.1.0). When I try to run the command, it says qemu-system-aarch64: -spice: invalid option
• Using ps, I see that the actual process is /Applications/UTM.app/Contents/XPCServices/QEMUHelper.xpc/Contents/MacOS/QEMULauncher.app/Contents/MacOS/QEMULauncher /Applications/UTM.app/Contents/Frameworks/qemu-aarch64-softmmu.framework/Versions/A/qemu-aarch64-softmmu instead of qemu-system-aarch64. So, I tried it but it failed immediately with Trace/BPT trap: 5.
• Using htop, I see that QEMULauncher is in fact a child process of QEMUHelper. But the latter has no command line argument and must have been created using some specific configuration. If I try to run it, I get An XPC Service cannot be run directly.

So, is there a simple way to tweak the UTM-generated qemu command using another instance of qemu, namely the version 7.1.0 which is installed with Homebrew?

[osy]

https://github.com/utmapp/UTM/releases Please check out 4.1.1 beta. QEMU has been updated.

[lelegard]

ttps://github.com/utmapp/UTM/releases Please check out 4.1.1 beta. QEMU has been updated.

Thanks, works great, no more "network dropped" error.