Disable predictable network interface names to avoid cases where devices

don't reboot properly because interface name changed...

src/yunohost/data_migrations/0003_migrate_to_stretch.py

@@ -15,6 +15,7 @@ from yunohost.service import (_run_service_command,
                               manually_modified_files_compared_to_debian_default)
 from yunohost.utils.filesystem import free_space_in_directory
 from yunohost.utils.packages import get_installed_version
+from yunohost.utils.network import get_network_interfaces
 
 logger = getActionLogger('yunohost.migration')
 
@@ -68,6 +69,8 @@ class MyMigration(Migration):
         self.apt_dist_upgrade(conf_flags=["new", "miss", "def"])
         _run_service_command("restart", "fail2ban")
 
+        self.disable_predicable_interface_names()
+
         # Clean the mess
         os.system("apt autoremove --assume-yes")
         os.system("apt clean --assume-yes")
@@ -352,3 +355,20 @@ class MyMigration(Migration):
             # command showing in the terminal, since 'info' channel is only
             # enabled if the user explicitly add --verbose ...
             os.system(command)
+
+    def disable_predicable_interface_names(self):
+
+        # Try to see if currently used interface names are predictable ones or not...
+        # If we ain't using "eth0" or "wlan0", assume we are using predictable interface
+        # names and therefore they shouldnt be disabled
+        network_interfaces = get_network_interfaces().keys()
+        if "eth0" not in network_interfaces and "wlan0" not in network_interfaces:
+            return
+
+        interfaces_config = read_file("/etc/network/interfaces")
+        if "eth0" not in interfaces_config and "wlan0" not in interfaces_config:
+            return
+
+        # Disable predictive interface names
+        # c.f. https://unix.stackexchange.com/a/338730
+        os.system("ln -s /dev/null /etc/systemd/network/99-default.link")

src/yunohost/utils/network.py

@@ -56,7 +56,7 @@ def get_network_interfaces():
     # Parse relevant informations for each of them
     devices = {name: _extract_inet(addrs) for name, addrs in devices_raw.items() if name != "lo"}
 
-    return devices or "unknown"
+    return devices
 
 
 def get_gateway():
@@ -64,10 +64,10 @@ def get_gateway():
     output = subprocess.check_output('ip route show'.split())
     m = re.search('default via (.*) dev ([a-z]+[0-9]?)', output)
     if not m:
-        return "unknown"
+        return None
 
     addr = _extract_inet(m.group(1), True)
-    return addr.popitem()[1] if len(addr) == 1 else "unknown"
+    return addr.popitem()[1] if len(addr) == 1 else None
 
 
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