CherryPicked: [cnv-4.19] net, tests, hot-plug: W/A guest-agent deadlock on hot-plugged interfaces

tests/network/libs/guest.py

@@ -0,0 +1,56 @@
+import ipaddress
+import json
+import logging
+from typing import TYPE_CHECKING, Final
+
+from libs.net.vmspec import IpNotFound
+from libs.vm.vm import BaseVirtualMachine
+from utilities.virt import vm_console_run_commands
+
+if TYPE_CHECKING:
+    from utilities.virt import VirtualMachineForTests
+
+LOGGER = logging.getLogger(__name__)
+
+
+def read_guest_interface_ipv4(
+    vm: VirtualMachineForTests | BaseVirtualMachine,
+    interface_name: str,
+    expected_ip: ipaddress.IPv4Address | None = None,
+) -> ipaddress.IPv4Interface:
+    """Retrieve the IPv4 address and prefix length of an interface from the VM guest OS.
+
+    Args:
+        vm: The virtual machine to query.
+        interface_name: The name of the network interface (e.g., "eth0").
+        expected_ip: When provided, the command filters to this specific host address
+            using 'ip addr show to <expected_ip>', which returns output only when
+            that address is configured on the interface. Useful when the interface
+            may carry multiple addresses.
+
+    Returns:
+        IPv4 address with prefix length (e.g., 192.168.1.5/24).
+
+    Raises:
+        IpNotFound: If no matching IPv4 address is found or console output cannot be parsed.
+    """
+    to_filter: Final[str] = f" to {expected_ip}" if expected_ip is not None else ""
+    cmd: Final[str] = f"ip -j -4 addr show {interface_name}{to_filter}"
+
+    output = vm_console_run_commands(vm=vm, commands=[cmd], timeout=30)
+    LOGGER.info(f"Command {cmd} output: {output[cmd]}")
+
+    try:
+        iface_info = json.loads(output[cmd][1])
+    except (IndexError, json.JSONDecodeError) as err:
+        raise IpNotFound(f"Failed to parse console JSON from VM {vm.name} for '{cmd}': {output[cmd]}") from err
+
+    if iface_info and "addr_info" in iface_info[0]:
+        for addr in iface_info[0]["addr_info"]:
+            if addr.get("family") == "inet":
+                if expected_ip is None or ipaddress.IPv4Address(addr["local"]) == expected_ip:
+                    return ipaddress.IPv4Interface(address=f"{addr['local']}/{addr['prefixlen']}")
+
+    raise IpNotFound(
+        f"{'No IPv4 address' if expected_ip is None else str(expected_ip)} found on {interface_name} in VM {vm.name}"
+    )