fix: preserve guest network identities and refresh session profiles

hydra/profiles.py

@@ -26,6 +26,7 @@ class Profile:
     width: int = 1280
     height: int = 800
     refresh_millihz: int = 0
+    mac: str | None = None
 
     def __post_init__(self):
         validate_name(self.name)
@@ -33,6 +34,12 @@ class Profile:
             if not isinstance(self.iso, (str, Path)) or not str(self.iso):
                 raise ValueError('ISO must be a nonempty path or omitted')
             object.__setattr__(self, 'iso', Path(self.iso).expanduser().resolve())
+        if self.mac is not None:
+            if (not isinstance(self.mac, str) or
+                not re.fullmatch(r'[0-9a-fA-F]{2}(:[0-9a-fA-F]{2}){5}', self.mac) or
+                int(self.mac[:2], 16) & 3 != 2):
+                raise ValueError('mac must be a locally administered unicast Ethernet address')
+            object.__setattr__(self, 'mac', self.mac.lower())
         for key, upper in (('memory', 262144), ('cpus', 256)):
             value = getattr(self, key)
             if type(value) is not int or not 1 <= value <= upper: