fix: preserve guest network identities and refresh session profiles

hydra/runtime.py

@@ -3,6 +3,7 @@
 import contextlib
 import errno
 import fcntl
+import hashlib
 import json
 import os
 import socket
@@ -54,6 +55,14 @@ def _intel_render_node() -> Path | None:
     return None
 
 
+def _stable_mac(paths: VMPaths) -> str:
+    # Disk/state identity survives restarts and runtime socket-directory changes.
+    # UID distinguishes owners even when a shared bridge sees the same names.
+    digest = bytearray(hashlib.sha256(f'{os.getuid()}:{paths.disk}'.encode()).digest()[:6])
+    digest[0] = (digest[0] & 0xfc) | 0x02
+    return ':'.join(f'{octet:02x}' for octet in digest)
+
+
 def build_qemu_argv(profile: Profile, paths: VMPaths) -> list[str]:
     accel = 'kvm' if os.access('/dev/kvm', os.R_OK | os.W_OK) else 'tcg'
     argv = [os.environ.get('HYDRA_QEMU', 'qemu-system-x86_64'), '-name', profile.name,
@@ -78,7 +87,7 @@ def build_qemu_argv(profile: Profile, paths: VMPaths) -> list[str]:
     argv += ['-device', 'virtio-blk-pci,drive=disk']
     if profile.iso is not None:
         argv += ['-device', 'ide-cd,drive=iso']
-    argv += ['-boot', 'order=dc' if profile.iso is not None else 'order=c', '-device', 'virtio-net-pci,netdev=net',
+    argv += ['-boot', 'order=dc' if profile.iso is not None else 'order=c', '-device', f'virtio-net-pci,netdev=net,mac={profile.mac or _stable_mac(paths)}',
              '-netdev', 'user,id=net' if profile.network == 'user'
              else f'bridge,id=net,br={profile.bridge}',
              '-device', 'qemu-xhci,id=usb', '-device', 'usb-tablet', '-device', 'usb-kbd']
@@ -136,6 +145,8 @@ class Runtime:
     def add(self, profile: Profile) -> None:
         self._validate_media(profile.iso)
         _private_dir(self.config)
+        if profile.mac is None:
+            profile = replace(profile, mac=_stable_mac(self.paths(profile.name)))
         save_profile(self.config / f'{profile.name}.toml', profile)
 
     @staticmethod