net: xsk: track AF_XDP sockets on a per-netns list

Track each AF_XDP socket in a per-netns list. This will be used later
by the sock_diag interface for querying sockets from userspace.
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

include/net/net_namespace.h

@@ -31,6 +31,7 @@
 #include <net/netns/xfrm.h>
 #include <net/netns/mpls.h>
 #include <net/netns/can.h>
+#include <net/netns/xdp.h>
 #include <linux/ns_common.h>
 #include <linux/idr.h>
 #include <linux/skbuff.h>
@@ -160,6 +161,9 @@ struct net {
 #endif
 #if IS_ENABLED(CONFIG_CAN)
 	struct netns_can	can;
+#endif
+#ifdef CONFIG_XDP_SOCKETS
+	struct netns_xdp	xdp;
 #endif
 	struct sock		*diag_nlsk;
 	atomic_t		fnhe_genid;

include/net/netns/xdp.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NETNS_XDP_H__
+#define __NETNS_XDP_H__
+
+#include <linux/rculist.h>
+#include <linux/mutex.h>
+
+struct netns_xdp {
+	struct mutex		lock;
+	struct hlist_head	list;
+};
+
+#endif /* __NETNS_XDP_H__ */

net/xdp/xsk.c

@@ -350,6 +350,10 @@ static int xsk_release(struct socket *sock)
 
 	net = sock_net(sk);
 
+	mutex_lock(&net->xdp.lock);
+	sk_del_node_init_rcu(sk);
+	mutex_unlock(&net->xdp.lock);
+
 	local_bh_disable();
 	sock_prot_inuse_add(net, sk->sk_prot, -1);
 	local_bh_enable();
@@ -746,6 +750,10 @@ static int xsk_create(struct net *net, struct socket *sock, int protocol,
 	mutex_init(&xs->mutex);
 	spin_lock_init(&xs->tx_completion_lock);
 
+	mutex_lock(&net->xdp.lock);
+	sk_add_node_rcu(sk, &net->xdp.list);
+	mutex_unlock(&net->xdp.lock);
+
 	local_bh_disable();
 	sock_prot_inuse_add(net, &xsk_proto, 1);
 	local_bh_enable();
@@ -759,6 +767,23 @@ static const struct net_proto_family xsk_family_ops = {
 	.owner	= THIS_MODULE,
 };
 
+static int __net_init xsk_net_init(struct net *net)
+{
+	mutex_init(&net->xdp.lock);
+	INIT_HLIST_HEAD(&net->xdp.list);
+	return 0;
+}
+
+static void __net_exit xsk_net_exit(struct net *net)
+{
+	WARN_ON_ONCE(!hlist_empty(&net->xdp.list));
+}
+
+static struct pernet_operations xsk_net_ops = {
+	.init = xsk_net_init,
+	.exit = xsk_net_exit,
+};
+
 static int __init xsk_init(void)
 {
 	int err;
@@ -771,8 +796,13 @@ static int __init xsk_init(void)
 	if (err)
 		goto out_proto;
 
+	err = register_pernet_subsys(&xsk_net_ops);
+	if (err)
+		goto out_sk;
 	return 0;
 
+out_sk:
+	sock_unregister(PF_XDP);
 out_proto:
 	proto_unregister(&xsk_proto);
 out: