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python/machine: Fix AF_UNIX path too long on macOS 

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 <peter@pjd.dev>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20230110082930.42129-2-peter@pjd.dev
Signed-off-by: John Snow <jsnow@redhat.com>
This commit is contained in:
Peter Delevoryas 2023-01-10 00:29:30 -08:00 committed by John Snow
parent ada73a492c
commit f9922937d1
2 changed files with 4 additions and 4 deletions
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6
python/qemu/machine/machine.py
View File

@ -157,7 +157,7 @@ class QEMUMachine:
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}"
self._temp_dir: Optional[str] = None
self._base_temp_dir = base_temp_dir
self._sock_dir = sock_dir
@ -167,7 +167,7 @@ class QEMUMachine:
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 @@ class QEMUMachine:
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] = []

2
tests/avocado/avocado_qemu/__init__.py
View File

@ -306,7 +306,7 @@ class QemuSystemTest(QemuBaseTest):
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)