net: option to force net MAC address

By default, QEMU sets the first NIC's MAC address to 52:54:00:12:34:56,
and increments the last octet for the next ones. When different VMs need
to discuss between each others via the same bridge, that can cause
conflicts.

A new option has been added to set a different MAC address, e.g.

  --net-mac-address 52:54:00:12:34:56

Which will assign 52:54:00:12:34:56 to the fist NIC, and increment the
last octet for the next one, etc.

Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>

virtme/commands/run.py

@@ -123,6 +123,13 @@ def make_parser() -> argparse.ArgumentParser:
         nargs="?",
         help="Enable basic network access: user, bridge(=<br>), loop.",
     )
+    g.add_argument(
+        "--net-mac-address",
+        action="store",
+        default=None,
+        help="The MAC address to assign to the NIC interface, e.g. 52:54:00:12:34:56. "
+        + "The last octet will be incremented for the next network devices.",
+    )
     g.add_argument(
         "--balloon",
         action="store_true",
@@ -1329,11 +1336,25 @@ def do_script(shellcmd: str, ret_path=None, show_boot_console=False) -> None:
         if video_args:
             qemuargs.extend(video_args)
 
+    def get_net_mac(index):
+        if args.net_mac_address is None:
+            return ""
+
+        mac = args.net_mac_address.split(':')
+        try:
+            if len(mac) != 6:
+                assert(ValueError)
+            mac[5] = "%02x" % ((int(mac[5], 16) + index) % 256)
+        except:
+            arg_fail("--net-mac-address: invalid MAC address: '%s'" % args.net_mac_address)
+        return ",mac=" + ":".join(mac)
+
     if args.net:
         extend_dhcp = False
         index = 0
         for net in args.net:
-            qemuargs.extend(["-device", "%s,netdev=n%d" % (arch.virtio_dev_type("net"), index)])
+            qemuargs.extend(["-device", "%s,netdev=n%d%s" %
+                            (arch.virtio_dev_type("net"), index, get_net_mac(index))])
             if net == "user":
                 qemuargs.extend(["-netdev", "user,id=n%d" % index])
                 extend_dhcp = True
@@ -1348,7 +1369,8 @@ def do_script(shellcmd: str, ret_path=None, show_boot_console=False) -> None:
                 hubid = index
                 qemuargs.extend(["-netdev", "hubport,id=n%d,hubid=%d" % (index, hubid)])
                 index += 1
-                qemuargs.extend(["-device", "%s,netdev=n%d" % (arch.virtio_dev_type("net"), index)])
+                qemuargs.extend(["-device", "%s,netdev=n%d%s" %
+                                (arch.virtio_dev_type("net"), index, get_net_mac(index))])
                 qemuargs.extend(["-netdev", "hubport,id=n%d,hubid=%d" % (index, hubid)])
             else:
                 arg_fail("--net: invalid choice: '%s' (choose from user, bridge(=<br>), loop)" % net)

virtme_ng/run.py

@@ -352,6 +352,14 @@ def make_parser():
         help="Enable network access: user, bridge(=<br>), loop",
     )
 
+    parser.add_argument(
+        "--net-mac-address",
+        "-N",
+        action="store",
+        help="The MAC address to assign to the NIC interface, e.g. 52:54:00:12:34:56. "
+        + "The last octet will be incremented for the next network devices.",
+    )
+
     parser.add_argument(
         "--disk",
         "-D",
@@ -934,6 +942,12 @@ def _get_virtme_network(self, args):
         else:
             self.virtme_param["network"] = ""
 
+    def _get_virtme_net_mac_address(self, args):
+        if args.net_mac_address is not None:
+            self.virtme_param["net_mac_address"] = "--net-mac-address " + args.net_mac_address
+        else:
+            self.virtme_param["net_mac_address"] = ""
+
     def _get_virtme_disk(self, args):
         if args.disk is not None:
             disk_str = ""
@@ -1088,6 +1102,7 @@ def run(self, args):
         self._get_virtme_no_virtme_ng_init(args)
         self._get_virtme_mods(args)
         self._get_virtme_network(args)
+        self._get_virtme_net_mac_address(args)
         self._get_virtme_disk(args)
         self._get_virtme_sound(args)
         self._get_virtme_disable_microvm(args)
@@ -1126,6 +1141,7 @@ def run(self, args):
             + f'{self.virtme_param["no_virtme_ng_init"]} '
             + f'{self.virtme_param["mods"]} '
             + f'{self.virtme_param["network"]} '
+            + f'{self.virtme_param["net_mac_address"]} '
             + f'{self.virtme_param["disk"]} '
             + f'{self.virtme_param["sound"]} '
             + f'{self.virtme_param["disable_microvm"]} '