[PATCH v2 2/2] net: add debugfs files for showing netns refcount tracking info

Jeff Layton
2025-04-08T13:36:54Z

CONFIG_NET_NS_REFCNT_TRACKER currently has no convenient way to display
its tracking info. Add a new net_ns directory under the debugfs
ref_tracker directory. Create a directory in there for every netns, with
refcnt and notrefcnt files that show the currently tracked active and
passive references.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
net/core/net_namespace.c | 151 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 151 insertions(+)

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 4303f2a4926243e2c0ff0c0387383cd8e0658019..7e9dc487f46d656ee4ae3d6d18d35bb2aba2b176 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -1512,3 +1512,154 @@ const struct proc_ns_operations netns_operations = {
.owner = netns_owner,
};
#endif
+
+#ifdef CONFIG_DEBUG_FS
+#ifdef CONFIG_NET_NS_REFCNT_TRACKER
+
+#include <linux/debugfs.h>
+
+static struct dentry *ns_ref_tracker_dir;
+static unsigned int ns_debug_net_id;
+
+struct ns_debug_net {
+ struct dentry *netdir;
+ struct dentry *refcnt;
+ struct dentry *notrefcnt;
+};
+
+#define MAX_NS_DEBUG_BUFSIZE (32 * PAGE_SIZE)
+
+static int
+ns_debug_tracker_show(struct seq_file *f, void *v)
+{
+ struct ref_tracker_dir *tracker = f->private;
+ int len, bufsize = PAGE_SIZE;
+ char *buf;
+
+ for (;;) {
+ buf = kvmalloc(bufsize, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ len = ref_tracker_dir_snprint(tracker, buf, bufsize);
+ if (len < bufsize)
+ break;
+
+ kvfree(buf);
+ bufsize *= 2;
+ if (bufsize > MAX_NS_DEBUG_BUFSIZE)
+ return -ENOBUFS;
+ }
+ seq_write(f, buf, len);
+ kvfree(buf);
+ return 0;
+}
+
+static int
+ns_debug_ref_open(struct inode *inode, struct file *filp)
+{
+ int ret;
+ struct net *net = inode->i_private;
+
+ ret = single_open(filp, ns_debug_tracker_show, &net->refcnt_tracker);
+ if (!ret)
+ net_passive_inc(net);
+ return ret;
+}
+
+static int
+ns_debug_notref_open(struct inode *inode, struct file *filp)
+{
+ int ret;
+ struct net *net = inode->i_private;
+
+ ret = single_open(filp, ns_debug_tracker_show, &net->notrefcnt_tracker);
+ if (!ret)
+ net_passive_inc(net);
+ return ret;
+}
+
+static int
+ns_debug_ref_release(struct inode *inode, struct file *filp)
+{
+ struct net *net = inode->i_private;
+
+ net_passive_dec(net);
+ return single_release(inode, filp);
+}
+
+static const struct file_operations ns_debug_ref_fops = {
+ .owner = THIS_MODULE,
+ .open = ns_debug_ref_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = ns_debug_ref_release,
+};
+
+static const struct file_operations ns_debug_notref_fops = {
+ .owner = THIS_MODULE,
+ .open = ns_debug_notref_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = ns_debug_ref_release,
+};
+
+static int
+ns_debug_init_net(struct net *net)
+{
+ struct ns_debug_net *dnet = net_generic(net, ns_debug_net_id);
+ char name[11]; /* 10 decimal digits + NULL term */
+ int len;
+
+ len = snprintf(name, sizeof(name), "%u", net->ns.inum);
+ if (len >= sizeof(name))
+ return -EOVERFLOW;
+
+ dnet->netdir = debugfs_create_dir(name, ns_ref_tracker_dir);
+ if (IS_ERR(dnet->netdir))
+ return PTR_ERR(dnet->netdir);
+
+ dnet->refcnt = debugfs_create_file("refcnt", S_IFREG | 0400, dnet->netdir,
+ net, &ns_debug_ref_fops);
+ if (IS_ERR(dnet->refcnt)) {
+ debugfs_remove(dnet->netdir);
+ return PTR_ERR(dnet->refcnt);
+ }
+
+ dnet->notrefcnt = debugfs_create_file("notrefcnt", S_IFREG | 0400, dnet->netdir,
+ net, &ns_debug_notref_fops);
+ if (IS_ERR(dnet->notrefcnt)) {
+ debugfs_remove_recursive(dnet->netdir);
+ return PTR_ERR(dnet->notrefcnt);
+ }
+
+ return 0;
+}
+
+static void
+ns_debug_exit_net(struct net *net)
+{
+ struct ns_debug_net *dnet = net_generic(net, ns_debug_net_id);
+
+ debugfs_remove_recursive(dnet->netdir);
+}
+
+static struct pernet_operations ns_debug_net_ops = {
+ .init = ns_debug_init_net,
+ .exit = ns_debug_exit_net,
+ .id = &ns_debug_net_id,
+ .size = sizeof(struct ns_debug_net),
+};
+
+static int __init ns_debug_init(void)
+{
+ ns_ref_tracker_dir = debugfs_create_dir("net_ns", ref_tracker_debug_dir);
+ if (IS_ERR(ns_ref_tracker_dir))
+ return PTR_ERR(ns_ref_tracker_dir);
+
+ register_pernet_subsys(&ns_debug_net_ops);
+ return 0;
+}
+late_initcall(ns_debug_init);
+#endif /* CONFIG_NET_NS_REFCNT_TRACKER */
+#endif /* CONFIG_DEBUG_FS */

--
2.49.0