diff --git a/src/libnm-core-impl/nm-setting.c b/src/libnm-core-impl/nm-setting.c
index 542ae6a80f..ce47c9bd1a 100644
--- a/src/libnm-core-impl/nm-setting.c
+++ b/src/libnm-core-impl/nm-setting.c
@@ -645,11 +645,16 @@ _property_direct_set_string(const NMSettInfoSetting  *sett_info,
     char **dst;
     char  *s;
 
+    nm_assert(property_info->property_type->direct_type == NM_VALUE_TYPE_STRING);
     nm_assert(((!!property_info->direct_set_string_ascii_strdown)
                + (!!property_info->direct_set_string_strip)
                + (property_info->direct_set_string_mac_address_len > 0)
                + (property_info->direct_set_string_ip_address_addr_family != 0))
-              <= 1);
+              <= (property_info->direct_hook.set_string_fcn ? 0 : 1));
+
+    if (property_info->direct_hook.set_string_fcn) {
+        return property_info->direct_hook.set_string_fcn(sett_info, property_info, setting, src);
+    }
 
     dst = _nm_setting_get_private(setting, sett_info, property_info->direct_offset);
 
diff --git a/src/libnm-core-impl/tests/test-setting.c b/src/libnm-core-impl/tests/test-setting.c
index 9ccedab806..0540b716a4 100644
--- a/src/libnm-core-impl/tests/test-setting.c
+++ b/src/libnm-core-impl/tests/test-setting.c
@@ -4430,6 +4430,7 @@ test_setting_metadata(void)
             GArray                   *property_types_data;
             guint                     prop_idx_val;
             gboolean                  can_set_including_default = FALSE;
+            gboolean                  can_have_direct_hook      = FALSE;
             int                       n_special_options;
 
             g_assert(sip->name);
@@ -4572,6 +4573,7 @@ test_setting_metadata(void)
                     g_assert(g_variant_type_equal(sip->property_type->dbus_type, "s"));
                     g_assert(sip->property_type->to_dbus_fcn
                              == _nm_setting_property_to_dbus_fcn_direct);
+                    can_have_direct_hook = TRUE;
                 }
                 g_assert(sip->param_spec);
                 g_assert(sip->param_spec->value_type == G_TYPE_STRING);
@@ -4596,6 +4598,9 @@ test_setting_metadata(void)
                 g_assert(sip->property_type->direct_type == NM_VALUE_TYPE_STRING);
             }
 
+            if (!can_have_direct_hook)
+                g_assert(!sip->direct_hook.set_string_fcn);
+
             n_special_options = (sip->direct_set_string_mac_address_len != 0)
                                 + (!!sip->direct_set_string_strip)
                                 + (!!sip->direct_set_string_ascii_strdown)
diff --git a/src/libnm-core-intern/nm-core-internal.h b/src/libnm-core-intern/nm-core-internal.h
index 50590f12a3..aee2a47263 100644
--- a/src/libnm-core-intern/nm-core-internal.h
+++ b/src/libnm-core-intern/nm-core-internal.h
@@ -746,8 +746,37 @@ struct _NMSettInfoProperty {
 
     GParamSpec *param_spec;
 
+    /* We want that our properties follow a small number of "default" types
+     * and behaviors. For example, we have int32 and string properties, but
+     * most properties of a certain type should behave in a similar way.
+     *
+     * That common behavior is realized via the property_type, which defines
+     * general behaviors for the property.
+     *
+     * Note that we still will need some property-specific additional tweaks.
+     * Of course, the name and param_spec are per-property. But below there are
+     * also flags and hooks, that can augment the behavior in the property_type.
+     * For example, the property_type in general might be of type string, but
+     * then we might want for some properties that the setter will strip
+     * whitespace. That is for example express with the flag direct_set_string_strip,
+     * which now is per-property-info, and no longer per-property-type.
+     *
+     * The distinction between those two is fixed. At the most extreme, we could
+     * move all fields from property_type to NMSettInfoProperty or we could move
+     * behavioral tweaks into the classes themselves. It's chosen this way so
+     * that we still have sensible common behaviors (string type), but minor
+     * tweaks are per property-info (and don't require a separate property-type). */
     const NMSettInfoPropertType *property_type;
 
+    union {
+        /* Optional hook for direct string properties, this gets called when setting the string.
+         * Return whether the value changed. */
+        gboolean (*set_string_fcn)(const NMSettInfoSetting  *sett_info,
+                                   const NMSettInfoProperty *property_info,
+                                   NMSetting                *setting,
+                                   const char               *src);
+    } direct_hook;
+
     /* This only has meaning for direct properties (property_type->direct_type != NM_VALUE_TYPE_UNSPEC).
      * In that case, this is the offset where _nm_setting_get_private() can find
      * the direct location. */