feat(computes): a compute names the address migrations reach it on

Migration is client-driven: libvirt sends the VM's memory to the
destination's own host name unless a migration URI is given, and the
app never gave one. Where the hosts cannot resolve each other's names
(or the names point at a management network) every migration failed
with "Unable to resolve address '<host name>' service '49152'".

A compute now has an optional migration address (an IP address or a
host name, no scheme or port), editable in the compute form and the
API. A VM migrating to that compute is sent to tcp://<address>
(bracketed for IPv6). Empty, the default for existing computes, keeps
the previous behavior. The compute's host name is not reused, because
for SSH computes it can be an ssh_config alias.

The migration log entry names the address when one is set.

computes/api/serializers.py

@@ -22,4 +22,4 @@ class ComputeSerializer(serializers.ModelSerializer):
 
     class Meta:
         model = Compute
-        fields = ["id", "name", "hostname", "login", "password", "type", "details"]
+        fields = ["id", "name", "hostname", "login", "password", "type", "details", "migration_address"]

computes/forms.py

@@ -50,4 +50,4 @@ class SocketComputeForm(forms.ModelForm):
 
     class Meta:
         model = Compute
-        fields = ["name", "details", "hostname", "type"]
+        fields = ["name", "details", "hostname", "type", "migration_address"]

computes/migrations/0004_compute_migration_address.py

@@ -0,0 +1,26 @@
+# Generated by Django 5.2.17 on 2026-10-06 08:53
+
+import computes.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("computes", "0003_auto_20200615_0637"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="compute",
+            name="migration_address",
+            field=models.CharField(
+                blank=True,
+                default="",
+                help_text="IP address or host name the other hosts send migrating VMs to; empty: the host's own host name, which they must be able to resolve",
+                max_length=64,
+                validators=[computes.validators.validate_migration_address],
+                verbose_name="migration address",
+            ),
+        ),
+    ]

computes/models.py

@@ -1,8 +1,11 @@
+from ipaddress import ip_address
+
 from django.db.models import CharField, IntegerField, Model
 from django.utils.functional import cached_property
 from django.utils.translation import gettext_lazy as _
 from libvirt import virConnect
 
+from computes.validators import validate_migration_address
 from vrtManager.connection import connection_manager
 from vrtManager.hostdetails import wvmHostDetails
 
@@ -14,6 +17,30 @@ class Compute(Model):
     password = CharField(_("password"), max_length=14, blank=True, null=True)
     details = CharField(_("details"), max_length=64, null=True, blank=True)
     type = IntegerField()
+    migration_address = CharField(
+        _("migration address"),
+        max_length=64,
+        blank=True,
+        default="",
+        validators=[validate_migration_address],
+        help_text=_(
+            "IP address or host name the other hosts send migrating VMs to; "
+            "empty: the host's own host name, which they must be able to resolve"
+        ),
+    )
+
+    @property
+    def migration_uri(self):
+        """The native migration URI for VMs migrated to this host, or None for
+        libvirt's default."""
+        if not self.migration_address:
+            return None
+        try:
+            if ip_address(self.migration_address).version == 6:
+                return f"tcp://[{self.migration_address}]"
+        except ValueError:
+            pass
+        return f"tcp://{self.migration_address}"
 
     @cached_property
     def status(self):

computes/test_migration_address.py

@@ -0,0 +1,73 @@
+"""A compute's migration address: where other hosts send a migrating VM's
+memory. Empty means libvirt's default (the destination's own hostname)."""
+
+from unittest.mock import MagicMock, patch
+
+from django.contrib.auth import get_user_model
+from django.core.exceptions import ValidationError
+from django.test import TestCase
+from django.urls import reverse
+
+from computes.models import Compute
+from computes.validators import validate_migration_address
+from instances.models import Instance
+from instances.utils import migrate_instance
+from logs.models import Logs
+
+
+class MigrationAddressTests(TestCase):
+    def test_accepted_and_refused_values(self):
+        for value in ("192.0.2.12", "kvm102.example.org", "kvm-102", "2001:db8::12",
+                      "kvm102.example.org."):
+            with self.subTest(value=value):
+                validate_migration_address(value)
+        for value in ("tcp://10.0.0.1", "10.0.0.1:49152", "[2001:db8::12]", "host name", "-bad", "a..b", "10.0.0.1/24", "x;y",
+                      "2001:db8::12%eth0", "2001:db8::12%bad]:49152", "a.."):
+            with self.subTest(value=value), self.assertRaises(ValidationError):
+                validate_migration_address(value)
+
+    def test_migration_uri(self):
+        cases = {"": None, "192.0.2.12": "tcp://192.0.2.12", "kvm102.example.org": "tcp://kvm102.example.org",
+                 "2001:db8::12": "tcp://[2001:db8::12]"}
+        for address, uri in cases.items():
+            with self.subTest(address=address):
+                self.assertEqual(Compute(migration_address=address).migration_uri, uri)
+
+    def test_the_compute_form_saves_it(self):
+        self.client.force_login(get_user_model().objects.create_superuser("ma-admin", "ma@example.com", "pw"))
+        compute = Compute.objects.create(name="ma", hostname="10.0.0.9", login="root", password="", type=2)
+        data = {"name": "ma", "hostname": "10.0.0.9", "login": "root", "type": 2, "details": "", "migration_address": "198.51.100.9"}
+        self.client.post(reverse("compute_update", args=[compute.id]), data)
+        compute.refresh_from_db()
+        self.assertEqual(compute.migration_address, "198.51.100.9")
+        self.client.post(reverse("compute_update", args=[compute.id]), {**data, "migration_address": "tcp://x"})
+        compute.refresh_from_db()
+        self.assertEqual(compute.migration_address, "198.51.100.9")
+
+    def test_a_migration_uses_the_destination_address(self):
+        source = Compute.objects.create(name="ma-src", hostname="10.0.0.8", login="root", password="", type=2)
+        dest = Compute.objects.create(name="ma-dst", hostname="kvm9", login="root", password="", type=2,
+                                      migration_address="198.51.100.9")
+        vm = MagicMock(compute=source, autostart=False)
+        vm.name = "vm"
+        with patch("instances.utils.connection_manager.host_is_up", return_value=True), \
+             patch("instances.utils.wvmInstances") as instances, \
+             patch("instances.utils.wvmInstance"), \
+             patch("instances.utils.Instance") as model:
+            model.objects.filter.return_value.first.return_value = None
+            migrate_instance(dest, vm, None, live=True)
+        self.assertEqual(instances.return_value.moveto.call_args.kwargs["uri"], "tcp://198.51.100.9")
+
+    def test_the_log_names_the_migration_address(self):
+        self.client.force_login(get_user_model().objects.create_superuser("ma-log", "ml@example.com", "pw"))
+        source = Compute.objects.create(name="ml-src", hostname="198.51.100.8", login="root", password="", type=2)
+        cases = {"": "to 198.51.100.9", "203.0.113.9": "to 198.51.100.9 via 203.0.113.9"}
+        for address, text in cases.items():
+            with self.subTest(address=address):
+                dest = Compute.objects.create(name=f"ml-dst{address}", hostname="198.51.100.9", login="root",
+                                              password="", type=2, migration_address=address)
+                vm = Instance.objects.create(compute=source, name="vm", uuid=f"u-{address}")
+                with patch("instances.views.utils.migrate_instance"):
+                    self.client.post(reverse("instances:migrate", args=[vm.id]),
+                                     {"compute_id": dest.id, "live_migrate": "true"})
+                self.assertTrue(Logs.objects.latest("id").message.endswith(text), Logs.objects.latest("id").message)

computes/validators.py

@@ -1,4 +1,5 @@
 import re
+from ipaddress import ip_address
 
 from django.core.exceptions import ValidationError
 from django.utils.translation import gettext_lazy as _
@@ -24,3 +25,17 @@ def validate_name(value):
     have_symbol = wrong_name.match("[^a-zA-Z0-9._-]+")
     if have_symbol:
         raise ValidationError(_("The hostname must not contain any special characters"))
+
+
+_hostname = re.compile(r"[A-Za-z0-9]([A-Za-z0-9-]{0,61}[A-Za-z0-9])?(\.[A-Za-z0-9]([A-Za-z0-9-]{0,61}[A-Za-z0-9])?)*\.?")
+
+
+def validate_migration_address(value):
+    """An IP address (no IPv6 scope) or a host name: no scheme, port or brackets."""
+    try:
+        if not getattr(ip_address(value), "scope_id", None):
+            return
+    except ValueError:
+        if _hostname.fullmatch(value):
+            return
+    raise ValidationError(_("Enter an IP address or a host name, without a scheme or port"))

instances/utils.py

@@ -191,6 +191,7 @@ def migrate_instance(
                     autoconverge,
                     compress,
                     postcopy,
+                    uri=new_compute.migration_uri,
                 )
             finally:
                 if conn_migrate is not None:

instances/views.py

@@ -687,6 +687,8 @@ def migrate(request, pk):
             "hostname": target_host.hostname,
             "method": migration_method,
         }
+        if target_host.migration_address:
+            msg = _("%(msg)s via %(address)s") % {"msg": msg, "address": target_host.migration_address}
         addlogmsg(request.user.username, current_host, instance.name, msg)
 
     return get_safe_redirect(

vrtManager/instance.py

@@ -117,7 +117,10 @@ class wvmInstances(wvmConnect):
         autoconverge=False,
         compress=False,
         postcopy=False,
+        uri=None,
     ):
+        """uri: the native migration URI (tcp://address) on the destination;
+        None lets libvirt use the destination's own hostname."""
         # The source definition always goes: one left behind points at the
         # same (shared) disks as the migrated VM and could be started again.
         flags = VIR_MIGRATE_PERSIST_DEST | VIR_MIGRATE_UNDEFINE_SOURCE
@@ -144,7 +147,7 @@ class wvmInstances(wvmConnect):
                 "Destination host emulator is different. Cannot be migrated"
             )
 
-        dom.migrate(self.wvm, flags, None, None, 0)
+        dom.migrate(self.wvm, flags, None, uri, 0)
 
     def graphics_type(self, name):
         inst = self.get_instance(name)

vrtManager/test_migration.py

@@ -50,3 +50,11 @@ class MigrationFlagsTestCase(unittest.TestCase):
                 flags = source.instance.calls[0][0]
                 self.assertTrue(flags & libvirt.VIR_MIGRATE_UNDEFINE_SOURCE)
                 self.assertTrue(flags & libvirt.VIR_MIGRATE_PERSIST_DEST)
+
+    def test_the_migration_uri_is_passed_on(self):
+        source = FakeSource(1)
+        destination().moveto(source, "vm", live=True, unsafe=False, offline=False, uri="tcp://192.0.2.12")
+        self.assertEqual(source.instance.calls[0][1], "tcp://192.0.2.12")
+        source = FakeSource(1)
+        destination().moveto(source, "vm", live=True, unsafe=False, offline=False)
+        self.assertIsNone(source.instance.calls[0][1])