[Bug 1922102] Re: Broken tap networking on macOS host

[Thomas Huth]

Ticket has been moved here (thanks, Vladislav!):
https://gitlab.com/qemu-project/qemu/-/issues/335
... thus I'm closing this on Launchpad now.

** Bug watch added: gitlab.com/qemu-project/qemu/-/issues #335
   https://gitlab.com/qemu-project/qemu/-/issues/335

** Changed in: qemu
       Status: Incomplete => Invalid

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https://bugs.launchpad.net/bugs/1922102

Title:
  Broken tap networking on macOS host

Status in QEMU:
  Invalid

Bug description:
  Building QEMU with GLib newer than 2.58.3 corrupts tap networking on macOS 
hosts.
  Tap device was provided by Tun/Tap kernel extension installed from brew:
    brew install tuntap

  Checked revisions:
    553032d (v5.2.0)
    6d40ce0 (v6.0.0-rc1)

  Host:
   MacBook Pro (Retina, 15-inch, Mid 2015)
   macOS Catalina 10.15.6 (19G2021)

  Guest:
    Linux Ubuntu 4.4.0-206-generic x86_64
    Also tested macOS Catalina 10.15.7 as a guest, the behaviour is the same.

  QEMU command line:

  qemu-system-x86_64 \
    -drive file=hdd.qcow2,if=virtio,format=qcow2 \
    -m 3G \
    -nic tap,script=tap-up.sh

  tap-up.sh:

   #!/bin/sh

   TAPDEV="$1"
   BRIDGEDEV="bridge0"

   ifconfig "$BRIDGEDEV" addm "$TAPDEV"

  Enabling/disabling Hypervisor.Framework acceleration (`-accel hvf`)
  has no effect.

  How to reproduce:
    1. Build & install GLib > 2.58.3 (tested 2.60.7)
    2. Build qemu-system-x86_64 with GLib > 2.58.3
    3. Boot any guest with tap networking enabled
    4. See that the external network is inaccessible

  Hotfix:
    1. Build & install GLib 2.58.3
    2. Build qemu-system-x86_64 with GLib 2.58.3
    3. Boot any guest with tap networking enabled
    4. See that the external network is accessible, everything is working as 
expected

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