[PATCH net-next v6 4/9] vsock/loopback: add netns support

[Bobby Eshleman <bobbyeshleman@gmail.com>]

From: Bobby Eshleman <bobbyeshleman@meta.com>

Add NS support to vsock loopback. Sockets in a global mode netns
communicate with each other, regardless of namespace. Sockets in a local
mode netns may only communicate with other sockets within the same
namespace.

Use pernet_ops to install a vsock_loopback for every namespace that is
created (to be used if local mode is enabled).

Retroactively call init/exit on every namespace when the vsock_loopback
module is loaded in order to initialize the per-ns device.

Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>

---
Changes in v6:
- init pernet ops for vsock_loopback module
- vsock_loopback: add space in struct to clarify lock protection
- do proper cleanup/unregister on vsock_loopback_exit()
- vsock_loopback: use virtio_vsock_skb_net()

Changes in v5:
- add callbacks code to avoid reverse dependency
- add logic for handling vsock_loopback setup for already existing
  namespaces
---
 include/net/af_vsock.h         |  1 +
 include/net/netns/vsock.h      |  6 +++
 net/vmw_vsock/vsock_loopback.c | 98 ++++++++++++++++++++++++++++++++++++++----
 3 files changed, 97 insertions(+), 8 deletions(-)

diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index 628e35ae9d00..5180b7dbb6d6 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -320,4 +320,5 @@ static inline bool vsock_net_check_mode(struct vsock_sock *vsk, struct net *net,
 
 	return orig_net_mode == VSOCK_NET_MODE_GLOBAL && vsk->orig_net_mode == VSOCK_NET_MODE_GLOBAL;
 }
+
 #endif /* __AF_VSOCK_H__ */
diff --git a/include/net/netns/vsock.h b/include/net/netns/vsock.h
index d4593c0b8dc4..a32d546793a2 100644
--- a/include/net/netns/vsock.h
+++ b/include/net/netns/vsock.h
@@ -9,6 +9,8 @@ enum vsock_net_mode {
 	VSOCK_NET_MODE_LOCAL,
 };
 
+struct vsock_loopback;
+
 struct netns_vsock {
 	struct ctl_table_header *vsock_hdr;
 	spinlock_t lock;
@@ -16,5 +18,9 @@ struct netns_vsock {
 	/* protected by lock */
 	enum vsock_net_mode mode;
 	bool written;
+
+#if IS_ENABLED(CONFIG_VSOCKETS_LOOPBACK)
+	struct vsock_loopback *loopback;
+#endif
 };
 #endif /* __NET_NET_NAMESPACE_VSOCK_H */
diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
index 1b2fab73e0d0..134e0619de07 100644
--- a/net/vmw_vsock/vsock_loopback.c
+++ b/net/vmw_vsock/vsock_loopback.c
@@ -28,8 +28,16 @@ static u32 vsock_loopback_get_local_cid(void)
 
 static int vsock_loopback_send_pkt(struct sk_buff *skb)
 {
-	struct vsock_loopback *vsock = &the_vsock_loopback;
+	struct vsock_loopback *vsock;
 	int len = skb->len;
+	struct net *net;
+
+	net = virtio_vsock_skb_net(skb);
+
+	if (net && net->vsock.mode == VSOCK_NET_MODE_LOCAL)
+		vsock = net->vsock.loopback;
+	else
+		vsock = &the_vsock_loopback;
 
 	virtio_vsock_skb_queue_tail(&vsock->pkt_queue, skb);
 	queue_work(vsock->workqueue, &vsock->pkt_work);
@@ -134,27 +142,99 @@ static void vsock_loopback_work(struct work_struct *work)
 	}
 }
 
-static int __init vsock_loopback_init(void)
+static int vsock_loopback_init_vsock(struct vsock_loopback *vsock)
 {
-	struct vsock_loopback *vsock = &the_vsock_loopback;
-	int ret;
-
 	vsock->workqueue = alloc_workqueue("vsock-loopback", 0, 0);
 	if (!vsock->workqueue)
 		return -ENOMEM;
 
 	skb_queue_head_init(&vsock->pkt_queue);
 	INIT_WORK(&vsock->pkt_work, vsock_loopback_work);
+	return 0;
+}
+
+static void vsock_loopback_deinit_vsock(struct vsock_loopback *vsock)
+{
+	if (vsock->workqueue)
+		destroy_workqueue(vsock->workqueue);
+}
+
+static int vsock_loopback_init_net(struct net *net)
+{
+	if (WARN_ON_ONCE(net->vsock.loopback))
+		return 0;
+
+	net->vsock.loopback = kmalloc(sizeof(*net->vsock.loopback), GFP_KERNEL);
+	if (!net->vsock.loopback)
+		return -ENOMEM;
+
+	return vsock_loopback_init_vsock(net->vsock.loopback);
+}
+
+static void vsock_loopback_exit_net(struct net *net)
+{
+	if (net->vsock.loopback) {
+		vsock_loopback_deinit_vsock(net->vsock.loopback);
+		kfree(net->vsock.loopback);
+		net->vsock.loopback = NULL;
+	}
+}
+
+static void vsock_loopback_deinit_all(void)
+{
+	struct net *net;
+
+	down_read(&net_rwsem);
+	for_each_net(net)
+		vsock_loopback_exit_net(net);
+	up_read(&net_rwsem);
+}
+
+static struct pernet_operations vsock_loopback_net_ops = {
+	.init = vsock_loopback_init_net,
+	.exit = vsock_loopback_exit_net,
+};
+
+static int __init vsock_loopback_init(void)
+{
+	struct vsock_loopback *vsock = &the_vsock_loopback;
+	struct net *net;
+	int ret;
+
+	ret = vsock_loopback_init_vsock(vsock);
+	if (ret < 0)
+		return ret;
+
+	ret = register_pernet_subsys(&vsock_loopback_net_ops);
+	if (ret < 0)
+		goto out_deinit_vsock;
+
+	/* call callbacks on any net previously created */
+	down_read(&net_rwsem);
+	for_each_net(net) {
+		ret = vsock_loopback_init_net(net);
+		if (ret < 0)
+			break;
+	}
+	up_read(&net_rwsem);
+
+	/* undo any initializations that succeeded */
+	if (ret < 0)
+		goto out_deinit_pernet_vsock;
 
 	ret = vsock_core_register(&loopback_transport.transport,
 				  VSOCK_TRANSPORT_F_LOCAL);
 	if (ret)
-		goto out_wq;
+		goto out_deinit_pernet_vsock;
+
 
 	return 0;
 
-out_wq:
-	destroy_workqueue(vsock->workqueue);
+out_deinit_pernet_vsock:
+	vsock_loopback_deinit_all();
+	unregister_pernet_subsys(&vsock_loopback_net_ops);
+out_deinit_vsock:
+	vsock_loopback_deinit_vsock(vsock);
 	return ret;
 }
 
@@ -164,6 +244,8 @@ static void __exit vsock_loopback_exit(void)
 
 	vsock_core_unregister(&loopback_transport.transport);
 
+	vsock_loopback_deinit_all();
+
 	flush_work(&vsock->pkt_work);
 
 	virtio_vsock_skb_queue_purge(&vsock->pkt_queue);

-- 
2.47.3