On Tue, Jan 10, 2023 at 3:34 AM Peter Delevoryas <pe...@pjd.dev> wrote:
>
> On macOS, private $TMPDIR's are the default. These $TMPDIR's are
> generated from a user's unix UID and UUID [1], which can create a
> relatively long path:
>
> /var/folders/d7/rz20f6hd709c1ty8f6_6y_z40000gn/T/
>
> QEMU's avocado tests create a temporary directory prefixed by
> "avo_qemu_sock_", and create QMP sockets within _that_ as well.
> The QMP socket is unnecessarily long, because a temporary directory
> is created for every QEMUMachine object.
>
> /avo_qemu_sock_uh3w_dgc/qemu-37331-10bacf110-monitor.sock
>
> The path limit for unix sockets on macOS is 104: [2]
>
> /*
> * [XSI] Definitions for UNIX IPC domain.
> */
> struct sockaddr_un {
> unsigned char sun_len; /* sockaddr len including null */
> sa_family_t sun_family; /* [XSI] AF_UNIX */
> char sun_path[104]; /* [XSI] path name (gag) */
> };
>
> This results in avocado tests failing on macOS because the QMP unix
> socket can't be created, because the path is too long:
>
> ERROR| Failed to establish connection: OSError: AF_UNIX path too long
>
> This change resolves by reducing the size of the socket directory prefix
> and the suffix on the QMP and console socket names.
>
> The result is paths like this:
>
> pdel@pdel-mbp:/var/folders/d7/rz20f6hd709c1ty8f6_6y_z40000gn/T
> $ tree qemu*
> qemu_df4evjeq
> qemu_jbxel3gy
> qemu_ml9s_gg7
> qemu_oc7h7f3u
> qemu_oqb1yf97
> ├── 10a004050.con
> └── 10a004050.qmp
>
> [1]
> https://apple.stackexchange.com/questions/353832/why-is-mac-osx-temp-directory-in-weird-path
> [2]
> /Library/Developer/CommandLineTools/SDKs/MacOSX12.3.sdk/usr/include/sys/un.h
>
> Signed-off-by: Peter Delevoryas <pe...@pjd.dev>
I'm tentatively staging this with a benefit-of-the-doubt [1] -- my
tests are still running -- but I do have a question:
> ---
> python/qemu/machine/machine.py | 6 +++---
> tests/avocado/avocado_qemu/__init__.py | 2 +-
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/python/qemu/machine/machine.py b/python/qemu/machine/machine.py
> index 748a0d807c9d..d70977378305 100644
> --- a/python/qemu/machine/machine.py
> +++ b/python/qemu/machine/machine.py
> @@ -157,7 +157,7 @@ def __init__(self,
> self._wrapper = wrapper
> self._qmp_timer = qmp_timer
>
> - self._name = name or f"qemu-{os.getpid()}-{id(self):02x}"
> + self._name = name or f"{id(self):x}"
Why is it safe to not differentiate based on the process ID?
... I suppose the thinking is: by default, in machine.py, this is a
temp dir created by tempfile.mkdtemp which will be unique per-process.
I suppose there's no protection against a caller supplying the same
tempdir (or sockdir) to multiple instances, but I suppose in those
cases we get to argue that "Well, don't do that, then."
Does that sound about right?
--js
[1] staged @ https://gitlab.com/jsnow/qemu/-/commits/python
> self._temp_dir: Optional[str] = None
> self._base_temp_dir = base_temp_dir
> self._sock_dir = sock_dir
> @@ -167,7 +167,7 @@ def __init__(self,
> self._monitor_address = monitor_address
> else:
> self._monitor_address = os.path.join(
> - self.sock_dir, f"{self._name}-monitor.sock"
> + self.sock_dir, f"{self._name}.qmp"
> )
>
> self._console_log_path = console_log
> @@ -192,7 +192,7 @@ def __init__(self,
> self._console_set = False
> self._console_device_type: Optional[str] = None
> self._console_address = os.path.join(
> - self.sock_dir, f"{self._name}-console.sock"
> + self.sock_dir, f"{self._name}.con"
> )
> self._console_socket: Optional[socket.socket] = None
> self._remove_files: List[str] = []
> diff --git a/tests/avocado/avocado_qemu/__init__.py
> b/tests/avocado/avocado_qemu/__init__.py
> index 910f3ba1eab8..25a546842fab 100644
> --- a/tests/avocado/avocado_qemu/__init__.py
> +++ b/tests/avocado/avocado_qemu/__init__.py
> @@ -306,7 +306,7 @@ def require_netdev(self, netdevname):
> self.cancel('no support for user networking')
>
> def _new_vm(self, name, *args):
> - self._sd = tempfile.TemporaryDirectory(prefix="avo_qemu_sock_")
> + self._sd = tempfile.TemporaryDirectory(prefix="qemu_")
> vm = QEMUMachine(self.qemu_bin, base_temp_dir=self.workdir,
> sock_dir=self._sd.name, log_dir=self.logdir)
> self.log.debug('QEMUMachine "%s" created', name)
> --
> 2.39.0
>
>
