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>
(cherry picked from commit f9922937d173f50fe59fd1b20fadc445fb6b2564)
(Mjt: pick this simple fix for 7.2.x so subsequent changes applies cleanly)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/python/qemu/machine/machine.py b/python/qemu/machine/machine.py
index 37191f433b2dd3d405cb2dc5301847e7cf16feb7..5df210c8107c244761d09b346e0a439112c15f6b 100644 (file)
--- a/python/qemu/machine/machine.py
+++ b/python/qemu/machine/machine.py
@@ -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] = []

diff --git a/tests/avocado/avocado_qemu/__init__.py b/tests/avocado/avocado_qemu/__init__.py
index 910f3ba1eab80ae89b1e30dee70f917cb9c6ed2b..25a546842fab23e79c24e2099d2a02551a894f24 100644 (file)
--- a/tests/avocado/avocado_qemu/__init__.py
+++ b/tests/avocado/avocado_qemu/__init__.py
@@ -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)