Support IPv6 in get_address() (#387)

Uses `psutil` to retrieve IPv6 address of a network interface when the optional `use_ipv6=True` kwarg is set.

Note: testing is not included as it's not safely possible at the moment because it requires that the system itself has IPv6 support enabled, there's at least one interface with an IPv6 address and that the test itself can determine those conditions a priori.

Closes #386 .

Authors:
  - Peter Andreas Entschev (https://github.com/pentschev)

Approvers:
  - Mads R. B. Kristensen (https://github.com/madsbk)

URL: #387

Author: pentschev

python/ucxx/ucxx/utils.py

@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: Copyright (c) 2022-2023, NVIDIA CORPORATION & AFFILIATES.
+# SPDX-FileCopyrightText: Copyright (c) 2022-2025, NVIDIA CORPORATION & AFFILIATES.
 # SPDX-License-Identifier: BSD-3-Clause
 
 import fcntl
@@ -126,7 +126,7 @@ def filter(self, record):
     return logger
 
 
-def get_address(ifname=None):
+def get_address(ifname=None, use_ipv6=False):
     """
     Get the address associated with a network interface.
 
@@ -137,6 +137,15 @@ def get_address(ifname=None):
         If None, it uses the value of environment variable `UCXPY_IFNAME`
         and if `UCXPY_IFNAME` is not set it defaults to "ib0"
         An OSError is raised for invalid interfaces.
+    use_ipv6 : bool
+        Whether to get IPv6 addresses instead of the IPv4 default.
+        NOTE: Requires the `psutil` package.
+
+    Raises
+    ------
+    OSError
+        If no device was found with the specified `ifname`, or no suitable
+        devices were found when `ifname=None`.
 
     Returns
     -------
@@ -150,16 +159,31 @@ def get_address(ifname=None):
 
     >>> get_address(ifname='lo')
     '127.0.0.1'
+
+    >>> get_address(ifname='lo', use_ipv6=True)
+    '::1'
     """
 
     def _get_address(ifname):
-        ifname = ifname.encode()
-        with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as s:
-            return socket.inet_ntoa(
-                fcntl.ioctl(
-                    s.fileno(), 0x8915, struct.pack("256s", ifname[:15])  # SIOCGIFADDR
-                )[20:24]
-            )
+        if use_ipv6:
+            import psutil
+
+            addrs = psutil.net_if_addrs()
+            if ifname in addrs:
+                for addr in addrs[ifname]:
+                    if addr.family == socket.AF_INET6:
+                        return addr.address.split("%")[0]
+            raise OSError("No such device")
+        else:
+            ifname = ifname.encode()
+            with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as s:
+                return socket.inet_ntoa(
+                    fcntl.ioctl(
+                        s.fileno(),
+                        0x8915,  # SIOCGIFADDR
+                        struct.pack("256s", ifname[:15]),
+                    )[20:24]
+                )
 
     def _try_interfaces():
         prefix_priority = ["ib", "eth", "en"]
@@ -177,6 +201,7 @@ def _try_interfaces():
                     return _get_address(i)
                 except OSError:
                     pass
+        raise OSError("No devices found")
 
     if ifname is None:
         ifname = os.environ.get("UCXPY_IFNAME")