iwd: Mirror NM connections to IWD network config files

Watch for NMSettingConnection changes and creation signals and convert
them to IWD format and write them to the configured IWD profile storage
directory.  The logic is off by default and gets enabled when the new
iwd-config-path setting in nm.conf's [main] group is set to a path to
an existing directory.

The idea here is that when a user edits an NM connection profile, the
change is immediately mirrored in IWD since IWD watches its
configuration directory using inotify.  This way NM clients can be used
to edit 802.1x settings, the PSK passphrase or the SSID -- changes that
would previously not take effect with the IWD backend.

Some precautions are taken to not make connections owned by a user
available to other users, such connections are not converted at all.
In all other cases where a connection cannot be converted sufficiently
well to the IWD format, for various reasons, we also give up and not
mirror these connections.

Due to IWD limitations and design differences with NM this logic has
many problems where it may not do its task properly.  It's meant to work
on a best-effort and "better than nothing" basis, but it should be safe
in that it shouldn't delete users data or reveal secrets, etc.  The most
obvious limitation is that there can be multiple NM connections
referring to the same SSID+Security tuple and only one IWD profile can
exist because the filename is based on only the SSID+Security type.  We
already had one NM connection selected for each IWD KnownNetwork and
referenced by a pointer, so we ignore changes in NM connections other
than that selected one.

1 files changed, 20 insertions, 0 deletions

diff --git a/man/NetworkManager.conf.xml b/man/NetworkManager.conf.xml
index 9ddd2b55a0..f55fcec17c 100644
--- a/man/NetworkManager.conf.xml
+++ b/man/NetworkManager.conf.xml
@@ -474,6 +474,26 @@ no-auto-default=*
           </para>
         </listitem>
       </varlistentry>
+
+      <varlistentry>
+        <term><varname>iwd-config-path</varname></term>
+        <listitem>
+          <para>
+            If the value points to an existing directory, Network
+            Manager will attempt to write copies of new or modified
+            Wi-Fi connection profiles, converted into the IWD
+            format, into this directory thus making IWD connection
+            properties editable.  This will only happen if the IWD
+            backend is active meaning that at least one Wi-Fi device
+            must exist.
+          </para>
+          <para>
+            This allows editing connection profile settings such as
+            the 802.1x configuration using Network Manager clients.
+            Without it such changes have no effect in IWD.
+          </para>
+        </listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>