cephadm: add generic methods for sharing namespaces across containers

In the future, some sidecar containers will need to share namespaces
with the primary container (or each other). Make it easy to set this up
by creating a enable_shared_namespaces function and Namespace enum.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

src/cephadm/cephadmlib/container_types.py

@@ -1,9 +1,11 @@
 # container_types.py - container instance wrapper types
 
 import copy
+import enum
+import functools
 import os
 
-from typing import Dict, List, Optional, Any, Union, Tuple, cast
+from typing import Dict, List, Optional, Any, Union, Tuple, Iterable, cast
 
 from .call_wrappers import call, call_throws, CallVerbosity
 from .constants import DEFAULT_TIMEOUT
@@ -599,3 +601,62 @@ def extract_uid_gid(
         raise Error(f'Failed to extract uid/gid for path {ex[0]}: {ex[1]}')
 
     raise RuntimeError('uid/gid not found')
+
+
+@functools.lru_cache()
+def _opt_key(value: str) -> str:
+    """Return a (long) option stripped of its value."""
+    return value.split('=', 1)[0]
+
+
+def _replace_container_arg(args: List[str], new_arg: str) -> None:
+    """Remove and replace arguments that have the same `--xyz` part as
+    the given `new_arg`. If new_arg is expected to have a value it
+    must be part of the new_arg string following an equal sign (`=`).
+    The existing arg may be a single or two strings in the input list.
+    """
+    key = _opt_key(new_arg)
+    has_value = key != new_arg
+    try:
+        idx = [_opt_key(v) for v in args].index(key)
+        if '=' in args[idx] or not has_value:
+            del args[idx]
+        else:
+            del args[idx]
+            del args[idx]
+    except ValueError:
+        pass
+    args.append(new_arg)
+
+
+class Namespace(enum.Enum):
+    """General container namespace control options."""
+
+    cgroupns = 'cgroupns'
+    cgroup = 'cgroupns'  # alias
+    ipc = 'ipc'
+    network = 'network'
+    pid = 'pid'
+    userns = 'userns'
+    user = 'userns'  # alias
+    uts = 'uts'
+
+    def to_option(self, value: str) -> str:
+        return f'--{self}={value}'
+
+    def __str__(self) -> str:
+        return self.value
+
+
+def enable_shared_namespaces(
+    args: List[str],
+    name: str,
+    ns: Iterable[Namespace],
+) -> None:
+    """Update the args list to contain options that enable container namespace
+    sharing where name is the name/id of the target container and ns is a list
+    or set of namespaces that should be shared.
+    """
+    cc = f'container:{name}'
+    for n in ns:
+        _replace_container_arg(args, n.to_option(cc))

src/cephadm/tests/test_util_funcs.py

@@ -906,3 +906,65 @@ def test_daemon_sub_id_systemd_names():
     )
     with pytest.raises(ValueError):
         dsi.service_name
+
+
+@pytest.mark.parametrize(
+    "args,new_arg,expected",
+    [
+        (['--foo=77'], '--bar', ['--foo=77', '--bar']),
+        (['--foo=77'], '--foo=12', ['--foo=12']),
+        (
+            ['--foo=77', '--quux=later', '--range=2-5'],
+            '--quux=now',
+            ['--foo=77', '--range=2-5', '--quux=now'],
+        ),
+        (
+            ['--foo=77', '--quux', 'later', '--range=2-5'],
+            '--quux=now',
+            ['--foo=77', '--range=2-5', '--quux=now'],
+        ),
+        (
+            ['--foo=77', '--quux', 'later', '--range=2-5'],
+            '--jiffy',
+            ['--foo=77', '--quux', 'later', '--range=2-5', '--jiffy'],
+        ),
+        (
+            ['--foo=77', '--quux=buff', '--range=2-5'],
+            '--quux',
+            ['--foo=77', '--range=2-5', '--quux'],
+        ),
+    ],
+)
+def test_replace_container_args(args, new_arg, expected):
+    from cephadmlib.container_types import _replace_container_arg
+
+    _args = list(args)  # preserve the input so test input is not mutated
+    _replace_container_arg(_args, new_arg)
+    assert _args == expected
+
+
+
+def test_enable_shared_namespaces():
+    from cephadmlib.container_types import enable_shared_namespaces, Namespace
+
+    args = []
+    enable_shared_namespaces(args, 'c001d00d', {Namespace.ipc})
+    assert args == ['--ipc=container:c001d00d']
+
+    enable_shared_namespaces(
+        args, 'c001d00d', [Namespace.uts, Namespace.network]
+    )
+    assert args == [
+        '--ipc=container:c001d00d',
+        '--uts=container:c001d00d',
+        '--network=container:c001d00d',
+    ]
+
+    enable_shared_namespaces(
+        args, 'badd33d5', [Namespace.network]
+    )
+    assert args == [
+        '--ipc=container:c001d00d',
+        '--uts=container:c001d00d',
+        '--network=container:badd33d5',
+    ]