settings: return errno from nms_keyfile_nmmeta_write() for better logging

I encountered a failure in the log

    <trace> [1564647990.7822] keyfile: commit: deleting nmmeta file "/etc/NetworkManager/system-connections/35370b0b-e53b-42ea-9fe3-f1b1d552343b.nmmeta" failed
    <trace> [1564647990.7822] keyfile: commit: deleting nmmeta file "/etc/NetworkManager/system-connections/35370b0b-e53b-42ea-9fe3-f1b1d552343b.nmmeta" simulated

I think that was due to SELinux (rh #1738010).

Let nms_keyfile_nmmeta_write() return an errno code so we can log
more information about the failure.

src/settings/plugins/keyfile/nms-keyfile-plugin.c

@@ -1090,7 +1090,7 @@ nms_keyfile_plugin_set_nmmeta_tombstone (NMSKeyfilePlugin *self,
 	gboolean hard_failure = FALSE;
 	NMSKeyfileStorage *storage;
 	gs_unref_object NMSKeyfileStorage *storage_result = NULL;
-	gboolean nmmeta_success = FALSE;
+	gboolean nmmeta_errno;
 	gs_free char *nmmeta_filename = NULL;
 	NMSKeyfileStorageType storage_type;
 	const char *loaded_path;
@@ -1116,6 +1116,7 @@ nms_keyfile_plugin_set_nmmeta_tombstone (NMSKeyfilePlugin *self,
 			       simulate ? "simulate " : "",
 			       loaded_path ? "write" : "delete",
 			       uuid);
+			nmmeta_errno = 0;
 			hard_failure = TRUE;
 			goto out;
 		}
@@ -1124,29 +1125,30 @@ nms_keyfile_plugin_set_nmmeta_tombstone (NMSKeyfilePlugin *self,
 	}
 
 	if (simulate) {
-		nmmeta_success = TRUE;
+		nmmeta_errno = 0;
 		nmmeta_filename = nms_keyfile_nmmeta_filename (dirname, uuid, FALSE);
 	} else {
-		nmmeta_success = nms_keyfile_nmmeta_write (dirname,
+		nmmeta_errno = nms_keyfile_nmmeta_write (dirname,
-		                                           uuid,
+		                                         uuid,
-		                                           loaded_path,
+		                                         loaded_path,
-		                                           FALSE,
+		                                         FALSE,
-		                                           shadowed_storage,
+		                                         shadowed_storage,
-		                                           &nmmeta_filename);
+		                                         &nmmeta_filename);
 	}
 
-	_LOGT ("commit: %s nmmeta file \"%s\"%s%s%s%s%s%s %s",
+	_LOGT ("commit: %s nmmeta file \"%s\"%s%s%s%s%s%s %s%s%s%s",
 	       loaded_path ? "writing" : "deleting",
 	       nmmeta_filename,
 	       NM_PRINT_FMT_QUOTED (loaded_path, " (pointing to \"", loaded_path, "\")", ""),
 	       NM_PRINT_FMT_QUOTED (shadowed_storage, " (shadows \"", shadowed_storage, "\")", ""),
 	       simulate
 	       ? "simulated"
-	       : (  nmmeta_success
+	       : (  nmmeta_errno < 0
-	          ? "succeeded"
+	          ? "failed"
-	          : "failed"));
+	          : "succeeded"),
+	       NM_PRINT_FMT_QUOTED (nmmeta_errno < 0, " (", nm_strerror_native (nm_errno_native (nmmeta_errno)), ")", ""));
 
-	if (!nmmeta_success)
+	if (nmmeta_errno < 0)
 		goto out;
 
 	storage = nm_sett_util_storages_lookup_by_filename (&priv->storages, nmmeta_filename);
@@ -1177,12 +1179,13 @@ nms_keyfile_plugin_set_nmmeta_tombstone (NMSKeyfilePlugin *self,
 	}
 
 out:
-	nm_assert (!nmmeta_success || !hard_failure);
+	nm_assert (nmmeta_errno <= 0);
-	nm_assert (nmmeta_success  || !storage_result);
+	nm_assert (nmmeta_errno < 0  || !hard_failure);
+	nm_assert (nmmeta_errno == 0 || !storage_result);
 
 	NM_SET_OUT (out_hard_failure, hard_failure);
 	NM_SET_OUT (out_storage, (NMSettingsStorage *) g_steal_pointer (&storage_result));
-	return nmmeta_success;
+	return nmmeta_errno >= 0;
 }
 
 /*****************************************************************************/

src/settings/plugins/keyfile/nms-keyfile-utils.c

@@ -206,7 +206,7 @@ nms_keyfile_nmmeta_read_from_file (const char *full_filename,
 	return TRUE;
 }
 
-gboolean
+int
 nms_keyfile_nmmeta_write (const char *dirname,
                           const char *uuid,
                           const char *loaded_path,
@@ -216,6 +216,7 @@ nms_keyfile_nmmeta_write (const char *dirname,
 {
 	gs_free char *full_filename_tmp = NULL;
 	gs_free char *full_filename = NULL;
+	int errsv;
 
 	nm_assert (dirname && dirname[0] == '/');
 	nm_assert (   nm_utils_is_uuid (uuid)
@@ -231,13 +232,15 @@ nms_keyfile_nmmeta_write (const char *dirname,
 	(void) unlink (full_filename_tmp);
 
 	if (!loaded_path) {
-		gboolean success = TRUE;
-
 		full_filename_tmp[strlen (full_filename_tmp) - 1] = '\0';
-		if (unlink (full_filename_tmp) != 0)
+		errsv = 0;
-			success = NM_IN_SET (errno, ENOENT);
+		if (unlink (full_filename_tmp) != 0) {
+			errsv = -NM_ERRNO_NATIVE (errno);
+			if (errsv == -ENOENT)
+				errsv = 0;
+		}
 		NM_SET_OUT (out_full_filename, g_steal_pointer (&full_filename_tmp));
-		return success;
+		return errsv;
 	}
 
 	if (loaded_path_allow_relative) {
@@ -270,30 +273,32 @@ nms_keyfile_nmmeta_write (const char *dirname,
 		                                 contents,
 		                                 length,
 		                                 0600,
-		                                 NULL,
+		                                 &errsv,
 		                                 NULL)) {
 			NM_SET_OUT (out_full_filename, g_steal_pointer (&full_filename_tmp));
-			return FALSE;
+			return -NM_ERRNO_NATIVE (errsv);
 		}
 	} else {
 		/* we only have the "loaded_path" to store. That is commonly used for the tombstones to
 		 * link to /dev/null. A symlink is sufficient to store that ammount of information.
 		 * No need to bother with a keyfile. */
 		if (symlink (loaded_path, full_filename_tmp) != 0) {
+			errsv = -NM_ERRNO_NATIVE (errno);
 			full_filename_tmp[strlen (full_filename_tmp) - 1] = '\0';
 			NM_SET_OUT (out_full_filename, g_steal_pointer (&full_filename_tmp));
-			return FALSE;
+			return errsv;
 		}
 
 		if (rename (full_filename_tmp, full_filename) != 0) {
+			errsv = -NM_ERRNO_NATIVE (errno);
 			(void) unlink (full_filename_tmp);
 			NM_SET_OUT (out_full_filename, g_steal_pointer (&full_filename));
-			return FALSE;
+			return errsv;
 		}
 	}
 
 	NM_SET_OUT (out_full_filename, g_steal_pointer (&full_filename));
-	return TRUE;
+	return 0;
 }
 
 /*****************************************************************************/

src/settings/plugins/keyfile/nms-keyfile-utils.h

@@ -66,12 +66,12 @@ gboolean nms_keyfile_nmmeta_read_from_file (const char *full_filename,
                                             char **out_loaded_path,
                                             char **out_shadowed_storage);
 
-gboolean nms_keyfile_nmmeta_write (const char *dirname,
+int nms_keyfile_nmmeta_write (const char *dirname,
-                                   const char *uuid,
+                              const char *uuid,
-                                   const char *loaded_path,
+                              const char *loaded_path,
-                                   gboolean loaded_path_allow_relative,
+                              gboolean loaded_path_allow_relative,
-                                   const char *shadowed_storage,
+                              const char *shadowed_storage,
-                                   char **out_full_filename);
+                              char **out_full_filename);
 
 /*****************************************************************************/
 

src/settings/plugins/keyfile/tests/test-keyfile-settings.c

@@ -2543,7 +2543,7 @@ _assert_keyfile_nmmeta (const char *dirname,
 	nm_clear_g_free (&full_filename);
 
 
-	g_assert (nms_keyfile_nmmeta_write (dirname, uuid, loaded_path, allow_relative, NULL, &full_filename));
+	g_assert_cmpint (nms_keyfile_nmmeta_write (dirname, uuid, loaded_path, allow_relative, NULL, &full_filename), ==, 0);
 	g_assert_cmpstr (full_filename, ==, exp_full_filename);
 	nm_clear_g_free (&full_filename);