diff mbox series

[net-next,v7,09/25] ovpn: introduce the ovpn_socket object

Message ID 20240917010734.1905-10-antonio@openvpn.net (mailing list archive)
State Deferred
Delegated to: Netdev Maintainers
Headers show
Series Introducing OpenVPN Data Channel Offload | expand

Checks

Context Check Description
netdev/series_format fail Series longer than 15 patches
netdev/tree_selection success Clearly marked for net-next, async
netdev/ynl success Generated files up to date; no warnings/errors; GEN HAS DIFF 2 files changed, 2619 insertions(+);
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 16 this patch: 16
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers warning 1 maintainers not CCed: openvpn-devel@lists.sourceforge.net
netdev/build_clang success Errors and warnings before: 17 this patch: 17
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 22 this patch: 22
netdev/checkpatch warning WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-09-17--15-00 (tests: 764)

Commit Message

Antonio Quartulli Sept. 17, 2024, 1:07 a.m. UTC
This specific structure is used in the ovpn kernel module
to wrap and carry around a standard kernel socket.

ovpn takes ownership of passed sockets and therefore an ovpn
specific objects is attached to them for status tracking
purposes.

Initially only UDP support is introduced. TCP will come in a later
patch.

Signed-off-by: Antonio Quartulli <antonio@openvpn.net>
---
 drivers/net/ovpn/Makefile |   2 +
 drivers/net/ovpn/socket.c | 120 ++++++++++++++++++++++++++++++++++++++
 drivers/net/ovpn/socket.h |  48 +++++++++++++++
 drivers/net/ovpn/udp.c    |  72 +++++++++++++++++++++++
 drivers/net/ovpn/udp.h    |  17 ++++++
 5 files changed, 259 insertions(+)
 create mode 100644 drivers/net/ovpn/socket.c
 create mode 100644 drivers/net/ovpn/socket.h
 create mode 100644 drivers/net/ovpn/udp.c
 create mode 100644 drivers/net/ovpn/udp.h
diff mbox series

Patch

diff --git a/drivers/net/ovpn/Makefile b/drivers/net/ovpn/Makefile
index ce13499b3e17..56bddc9bef83 100644
--- a/drivers/net/ovpn/Makefile
+++ b/drivers/net/ovpn/Makefile
@@ -13,3 +13,5 @@  ovpn-y += io.o
 ovpn-y += netlink.o
 ovpn-y += netlink-gen.o
 ovpn-y += peer.o
+ovpn-y += socket.o
+ovpn-y += udp.o
diff --git a/drivers/net/ovpn/socket.c b/drivers/net/ovpn/socket.c
new file mode 100644
index 000000000000..090a3232ab0e
--- /dev/null
+++ b/drivers/net/ovpn/socket.c
@@ -0,0 +1,120 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*  OpenVPN data channel offload
+ *
+ *  Copyright (C) 2020-2024 OpenVPN, Inc.
+ *
+ *  Author:	James Yonan <james@openvpn.net>
+ *		Antonio Quartulli <antonio@openvpn.net>
+ */
+
+#include <linux/net.h>
+#include <linux/netdevice.h>
+
+#include "ovpnstruct.h"
+#include "main.h"
+#include "io.h"
+#include "peer.h"
+#include "socket.h"
+#include "udp.h"
+
+static void ovpn_socket_detach(struct socket *sock)
+{
+	if (!sock)
+		return;
+
+	sockfd_put(sock);
+}
+
+/**
+ * ovpn_socket_release_kref - kref_put callback
+ * @kref: the kref object
+ */
+void ovpn_socket_release_kref(struct kref *kref)
+{
+	struct ovpn_socket *sock = container_of(kref, struct ovpn_socket,
+						refcount);
+
+	ovpn_socket_detach(sock->sock);
+	kfree_rcu(sock, rcu);
+}
+
+static bool ovpn_socket_hold(struct ovpn_socket *sock)
+{
+	return kref_get_unless_zero(&sock->refcount);
+}
+
+static struct ovpn_socket *ovpn_socket_get(struct socket *sock)
+{
+	struct ovpn_socket *ovpn_sock;
+
+	rcu_read_lock();
+	ovpn_sock = rcu_dereference_sk_user_data(sock->sk);
+	if (!ovpn_socket_hold(ovpn_sock)) {
+		pr_warn("%s: found ovpn_socket with ref = 0\n", __func__);
+		ovpn_sock = NULL;
+	}
+	rcu_read_unlock();
+
+	return ovpn_sock;
+}
+
+static int ovpn_socket_attach(struct socket *sock, struct ovpn_peer *peer)
+{
+	int ret = -EOPNOTSUPP;
+
+	if (!sock || !peer)
+		return -EINVAL;
+
+	if (sock->sk->sk_protocol == IPPROTO_UDP)
+		ret = ovpn_udp_socket_attach(sock, peer->ovpn);
+
+	return ret;
+}
+
+/**
+ * ovpn_socket_new - create a new socket and initialize it
+ * @sock: the kernel socket to embed
+ * @peer: the peer reachable via this socket
+ *
+ * Return: an openvpn socket on success or a negative error code otherwise
+ */
+struct ovpn_socket *ovpn_socket_new(struct socket *sock, struct ovpn_peer *peer)
+{
+	struct ovpn_socket *ovpn_sock;
+	int ret;
+
+	ret = ovpn_socket_attach(sock, peer);
+	if (ret < 0 && ret != -EALREADY)
+		return ERR_PTR(ret);
+
+	/* if this socket is already owned by this interface, just increase the
+	 * refcounter and use it as expected.
+	 *
+	 * Since UDP sockets can be used to talk to multiple remote endpoints,
+	 * openvpn normally instantiates only one socket and shares it among all
+	 * its peers. For this reason, when we find out that a socket is already
+	 * used for some other peer in *this* instance, we can happily increase
+	 * its refcounter and use it normally.
+	 */
+	if (ret == -EALREADY) {
+		/* caller is expected to increase the sock refcounter before
+		 * passing it to this function. For this reason we drop it if
+		 * not needed, like when this socket is already owned.
+		 */
+		ovpn_sock = ovpn_socket_get(sock);
+		sockfd_put(sock);
+		return ovpn_sock;
+	}
+
+	ovpn_sock = kzalloc(sizeof(*ovpn_sock), GFP_KERNEL);
+	if (!ovpn_sock)
+		return ERR_PTR(-ENOMEM);
+
+	ovpn_sock->ovpn = peer->ovpn;
+	ovpn_sock->sock = sock;
+	kref_init(&ovpn_sock->refcount);
+
+	rcu_assign_sk_user_data(sock->sk, ovpn_sock);
+
+	return ovpn_sock;
+}
diff --git a/drivers/net/ovpn/socket.h b/drivers/net/ovpn/socket.h
new file mode 100644
index 000000000000..5ad9c5073b08
--- /dev/null
+++ b/drivers/net/ovpn/socket.h
@@ -0,0 +1,48 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*  OpenVPN data channel offload
+ *
+ *  Copyright (C) 2020-2024 OpenVPN, Inc.
+ *
+ *  Author:	James Yonan <james@openvpn.net>
+ *		Antonio Quartulli <antonio@openvpn.net>
+ */
+
+#ifndef _NET_OVPN_SOCK_H_
+#define _NET_OVPN_SOCK_H_
+
+#include <linux/net.h>
+#include <linux/kref.h>
+#include <net/sock.h>
+
+struct ovpn_struct;
+struct ovpn_peer;
+
+/**
+ * struct ovpn_socket - a kernel socket referenced in the ovpn code
+ * @ovpn: ovpn instance owning this socket (UDP only)
+ * @sock: the low level sock object
+ * @refcount: amount of contexts currently referencing this object
+ * @rcu: member used to schedule RCU destructor callback
+ */
+struct ovpn_socket {
+	struct ovpn_struct *ovpn;
+	struct socket *sock;
+	struct kref refcount;
+	struct rcu_head rcu;
+};
+
+void ovpn_socket_release_kref(struct kref *kref);
+
+/**
+ * ovpn_socket_put - decrease reference counter
+ * @sock: the socket whose reference counter should be decreased
+ */
+static inline void ovpn_socket_put(struct ovpn_socket *sock)
+{
+	kref_put(&sock->refcount, ovpn_socket_release_kref);
+}
+
+struct ovpn_socket *ovpn_socket_new(struct socket *sock,
+				    struct ovpn_peer *peer);
+
+#endif /* _NET_OVPN_SOCK_H_ */
diff --git a/drivers/net/ovpn/udp.c b/drivers/net/ovpn/udp.c
new file mode 100644
index 000000000000..c10474d252e1
--- /dev/null
+++ b/drivers/net/ovpn/udp.c
@@ -0,0 +1,72 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*  OpenVPN data channel offload
+ *
+ *  Copyright (C) 2019-2024 OpenVPN, Inc.
+ *
+ *  Author:	Antonio Quartulli <antonio@openvpn.net>
+ */
+
+#include <linux/netdevice.h>
+#include <linux/socket.h>
+#include <net/udp.h>
+
+#include "ovpnstruct.h"
+#include "main.h"
+#include "socket.h"
+#include "udp.h"
+
+/**
+ * ovpn_udp_socket_attach - set udp-tunnel CBs on socket and link it to ovpn
+ * @sock: socket to configure
+ * @ovpn: the openvp instance to link
+ *
+ * After invoking this function, the sock will be controlled by ovpn so that
+ * any incoming packet may be processed by ovpn first.
+ *
+ * Return: 0 on success or a negative error code otherwise
+ */
+int ovpn_udp_socket_attach(struct socket *sock, struct ovpn_struct *ovpn)
+{
+	struct ovpn_socket *old_data;
+	int ret = 0;
+
+	/* sanity check */
+	if (sock->sk->sk_protocol != IPPROTO_UDP) {
+		DEBUG_NET_WARN_ON_ONCE(1);
+		return -EINVAL;
+	}
+
+	/* make sure no pre-existing encapsulation handler exists */
+	rcu_read_lock();
+	old_data = rcu_dereference_sk_user_data(sock->sk);
+	if (!old_data) {
+		/* socket is currently unused - we can take it */
+		rcu_read_unlock();
+		return 0;
+	}
+
+	/* socket is in use. We need to understand if it's owned by this ovpn
+	 * instance or by something else.
+	 * In the former case, we can increase the refcounter and happily
+	 * use it, because the same UDP socket is expected to be shared among
+	 * different peers.
+	 *
+	 * Unlikely TCP, a single UDP socket can be used to talk to many remote
+	 * hosts and therefore openvpn instantiates one only for all its peers
+	 */
+	if ((READ_ONCE(udp_sk(sock->sk)->encap_type) == UDP_ENCAP_OVPNINUDP) &&
+	    old_data->ovpn == ovpn) {
+		netdev_dbg(ovpn->dev,
+			   "%s: provided socket already owned by this interface\n",
+			   __func__);
+		ret = -EALREADY;
+	} else {
+		netdev_err(ovpn->dev,
+			   "%s: provided socket already taken by other user\n",
+			   __func__);
+		ret = -EBUSY;
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
diff --git a/drivers/net/ovpn/udp.h b/drivers/net/ovpn/udp.h
new file mode 100644
index 000000000000..f2507f8f2c71
--- /dev/null
+++ b/drivers/net/ovpn/udp.h
@@ -0,0 +1,17 @@ 
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*  OpenVPN data channel offload
+ *
+ *  Copyright (C) 2019-2024 OpenVPN, Inc.
+ *
+ *  Author:	Antonio Quartulli <antonio@openvpn.net>
+ */
+
+#ifndef _NET_OVPN_UDP_H_
+#define _NET_OVPN_UDP_H_
+
+struct ovpn_struct;
+struct socket;
+
+int ovpn_udp_socket_attach(struct socket *sock, struct ovpn_struct *ovpn);
+
+#endif /* _NET_OVPN_UDP_H_ */