nixos-rebuild-ng: improve IPv6 support (#469709)

pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/process.py

@@ -7,6 +7,7 @@ import shlex
 import subprocess
 from collections.abc import Sequence
 from dataclasses import dataclass
+from ipaddress import AddressValueError, IPv6Address
 from typing import Final, Self, TypedDict, Unpack
 
 from . import tmpdir
@@ -63,6 +64,23 @@ class Remote:
                         "'--ask-sudo-password' option instead"
                     )
 
+    def ssh_host(self) -> str:
+        """Fix up host string for SSH.
+
+        It returns an SSH-compatible host string if the host is using an
+        IPv6 address, otherwise it returns the passed host string unmodified.
+        """
+        try:
+            host_split = self.host.split("@")
+            host_fixed = host_split[-1].strip("[]").replace("%25", "%")
+            IPv6Address(host_fixed)
+            if len(host_split) > 1:
+                return host_split[0] + "@" + host_fixed
+            else:
+                return host_fixed
+        except AddressValueError:
+            return self.host
+
 
 # Not exhaustive, but we can always extend it later.
 class RunKwargs(TypedDict, total=False):
@@ -112,7 +130,7 @@ def run_wrapper(
             "ssh",
             *remote.opts,
             *SSH_DEFAULT_OPTS,
-            remote.host,
+            remote.ssh_host(),
             "--",
             # SSH will join the parameters here and pass it to the shell, so we
             # need to quote it to avoid issues.
@@ -187,7 +205,7 @@ def _kill_long_running_ssh_process(args: Args, remote: Remote) -> None:
                 "ssh",
                 *remote.opts,
                 *SSH_DEFAULT_OPTS,
-                remote.host,
+                remote.ssh_host(),
                 "--",
                 "pkill",
                 "--signal",

pkgs/by-name/ni/nixos-rebuild-ng/src/tests/test_process.py

@@ -140,3 +140,23 @@ def test_remote_from_name(monkeypatch: MonkeyPatch) -> None:
             opts=["-f", "foo", "-b", "bar", "-t"],
             sudo_password="password",
         )
+
+
+def test_ssh_host() -> None:
+    remotes = {
+        "user@[fe80::1%25eth0]": "user@fe80::1%eth0",
+        "[fe80::c98b%25enp4s0]": "fe80::c98b%enp4s0",
+        "user@[2001::5fce:a:198]": "user@2001::5fce:a:198",
+        "[2001::dead:beef]": "2001::dead:beef",
+        "root@192.168.178.1": "root@192.168.178.1",
+        "192.168.178.1": "192.168.178.1",
+        "user@localhost": "user@localhost",
+        "localhost": "localhost",
+        "user@example.org": "user@example.org",
+        "example.org": "example.org",
+    }
+
+    for host_input, expected in remotes.items():
+        remote = m.Remote.from_arg(host_input, None, False)
+        assert remote is not None
+        assert remote.ssh_host() == expected