lsns: show persistent namespace, add --persistent

karelzak · karelzak · commit eabbd8b7d581 · 2022-11-08T10:09:28.000+01:00
* show persistent namespaces (without processes) by default * add option --persistent only these namespaces Fixes: #1881 Signed-off-by: Karel Zak <kzak@redhat.com>
diff --git a/sys-utils/lsns.8.adoc b/sys-utils/lsns.8.adoc
@@ -48,6 +48,10 @@ The default list of columns may be extended if _list_ is specified in the format
 *--output-all*::
 Output all available columns.
 
+*-P*, *--persistent*::
+Display only the namespaces without processes (aka persistent namespaces), created by bind mounting
+/proc/pid/ns/type files to a filesystem path.
+
 *-p*, *--task* _PID_::
 Display only the namespaces held by the process with this _PID_.
 
diff --git a/sys-utils/lsns.c b/sys-utils/lsns.c
@@ -210,6 +210,7 @@ struct lsns {
 	unsigned int raw	: 1,
 		     json	: 1,
 		     tree	: 2,
+		     persist	: 1,
 		     no_trunc	: 1,
 		     no_headings: 1,
 		     no_wrap    : 1;
@@ -722,7 +723,7 @@ static struct lsns_namespace *add_namespace_for_nsfd(struct lsns *ls, int fd, in
 	if (clone_type < 0)
 		return NULL;
 	lsns_type = clone_type_to_lsns_type(clone_type);
-	if (lsns_type < 0)
+	if (lsns_type < 0 || ls->fltr_types[lsns_type] == 0)
 		return NULL;
 
 	fd_owner = ioctl(fd, NS_GET_USERNS);
@@ -858,6 +859,42 @@ static void read_related_namespaces(struct lsns *ls)
 	}
 }
 
+static int read_persistent_namespaces(struct lsns *ls)
+{
+	struct libmnt_iter *itr = mnt_new_iter(MNT_ITER_FORWARD);
+	struct libmnt_fs *fs = NULL;
+
+	while (mnt_table_next_fs(ls->tab, itr, &fs) == 0) {
+		const char *root;
+		char *p, *end = NULL;
+		ino_t ino;
+		int fd;
+
+		if (!mnt_fs_match_fstype(fs, "nsfs"))
+			continue;
+		root = mnt_fs_get_root(fs);
+		if (!root || !(p = strchr(root, '[')))
+			continue;
+
+		errno = 0;
+		ino = strtoumax(++p, &end, 10);
+		if (!end || *end != ']' || errno != 0)
+			continue;
+		if (get_namespace(ls, ino))
+			continue;
+
+		fd = open(mnt_fs_get_target(fs), O_RDONLY);
+		if (fd < 0)
+			continue;
+
+		add_namespace_for_nsfd(ls, fd, ino);
+		close(fd);
+	}
+
+	mnt_free_iter(itr);
+	return 0;
+}
+
 #endif /* USE_NS_GET_API */
 
 static int read_namespaces(struct lsns *ls)
@@ -885,6 +922,8 @@ static int read_namespaces(struct lsns *ls)
 	}
 
 #ifdef USE_NS_GET_API
+	read_persistent_namespaces(ls);
+
 	if (ls->tree == LSNS_TREE_OWNER || ls->tree == LSNS_TREE_PARENT)
 		read_related_namespaces(ls);
 #endif
@@ -1150,6 +1189,8 @@ static int show_namespaces(struct lsns *ls)
 
 		if (ls->fltr_pid != 0 && !namespace_has_process(ns, ls->fltr_pid))
 			continue;
+		if (ls->persist && ns->nprocs != 0)
+			continue;
 
 		if (!ns->ns_outline)
 			show_namespace(ls, tab, ns, ns->proc);
@@ -1240,6 +1281,7 @@ static void __attribute__((__noreturn__)) usage(void)
 	fputs(_(" -n, --noheadings       don't print headings\n"), out);
 	fputs(_(" -o, --output <list>    define which output columns to use\n"), out);
 	fputs(_("     --output-all       output all columns\n"), out);
+	fputs(_(" -P, --persistent       namespaces without processes\n"), out);
 	fputs(_(" -p, --task <pid>       print process namespaces\n"), out);
 	fputs(_(" -r, --raw              use the raw output format\n"), out);
 	fputs(_(" -u, --notruncate       don't truncate text in columns\n"), out);
@@ -1275,6 +1317,7 @@ int main(int argc, char *argv[])
 		{ "help",	no_argument,       NULL, 'h' },
 		{ "output",     required_argument, NULL, 'o' },
 		{ "output-all", no_argument,       NULL, OPT_OUTPUT_ALL },
+		{ "persistent", no_argument,       NULL, 'P' },
 		{ "notruncate", no_argument,       NULL, 'u' },
 		{ "version",    no_argument,       NULL, 'V' },
 		{ "noheadings", no_argument,       NULL, 'n' },
@@ -1288,6 +1331,7 @@ int main(int argc, char *argv[])
 
 	static const ul_excl_t excl[] = {	/* rows and cols in ASCII order */
 		{ 'J','r' },
+		{ 'P','p' },
 		{ 'l','T' },
 		{ 0 }
 	};
@@ -1307,7 +1351,7 @@ int main(int argc, char *argv[])
 	INIT_LIST_HEAD(&netnsids_cache);
 
 	while ((c = getopt_long(argc, argv,
-				"Jlp:o:nruhVt:T::W", long_opts, NULL)) != -1) {
+				"JlPp:o:nruhVt:T::W", long_opts, NULL)) != -1) {
 
 		err_exclusive_options(c, long_opts, excl, excl_st);
 
@@ -1325,6 +1369,9 @@ int main(int argc, char *argv[])
 			for (ncolumns = 0; ncolumns < ARRAY_SIZE(infos); ncolumns++)
 				columns[ncolumns] = ncolumns;
 			break;
+		case 'P':
+			ls.persist = 1;
+			break;
 		case 'p':
 			ls.fltr_pid = strtos32_or_err(optarg, _("invalid PID argument"));
 			break;
@@ -1430,11 +1477,9 @@ int main(int argc, char *argv[])
 	if (has_column(COL_NETNSID))
 		netlink_fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 #endif
-	if (has_column(COL_NSFS)) {
-		ls.tab = mnt_new_table_from_file(_PATH_PROC_MOUNTINFO);
-		if (!ls.tab)
-			err(MNT_EX_FAIL, _("failed to parse %s"), _PATH_PROC_MOUNTINFO);
-	}
+	ls.tab = mnt_new_table_from_file(_PATH_PROC_MOUNTINFO);
+	if (!ls.tab)
+		err(MNT_EX_FAIL, _("failed to parse %s"), _PATH_PROC_MOUNTINFO);
 
 	r = read_processes(&ls);
 	if (!r)
