Message-Id: <20241219-b4-ovpn-v16-16-3e3001153683@openvpn.net>
Date: Thu, 19 Dec 2024 02:42:10 +0100
From: Antonio Quartulli <antonio@...nvpn.net>
To: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Donald Hunter <donald.hunter@...il.com>, 
 Antonio Quartulli <antonio@...nvpn.net>, Shuah Khan <shuah@...nel.org>, 
 sd@...asysnail.net, ryazanov.s.a@...il.com, 
 Andrew Lunn <andrew+netdev@...n.ch>
Cc: Simon Horman <horms@...nel.org>, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, Xiao Liang <shaw.leon@...il.com>
Subject: [PATCH net-next v16 16/26] ovpn: implement multi-peer support

With this change an ovpn instance will be able to stay connected to
multiple remote endpoints.

This functionality is strictly required when running ovpn on an
OpenVPN server.

Signed-off-by: Antonio Quartulli <antonio@...nvpn.net>
---
 drivers/net/ovpn/main.c       |  67 +++++++++++++++++-
 drivers/net/ovpn/ovpnstruct.h |  16 +++++
 drivers/net/ovpn/peer.c       | 158 ++++++++++++++++++++++++++++++++++++++++--
 drivers/net/ovpn/peer.h       |   9 +++
 4 files changed, 241 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ovpn/main.c b/drivers/net/ovpn/main.c
index 0f291c540f8e05dbfbc15d835d6c71e796114b03..17cdd5a732132de71b854fe0b76c284bd9f3d918 100644
--- a/drivers/net/ovpn/main.c
+++ b/drivers/net/ovpn/main.c
@@ -24,6 +24,13 @@
 #include "proto.h"
 #include "tcp.h"
 
+static void ovpn_priv_free(struct net_device *net)
+{
+	struct ovpn_priv *ovpn = netdev_priv(net);
+
+	kfree(ovpn->peers);
+}
+
 static int ovpn_net_init(struct net_device *dev)
 {
 	struct ovpn_priv *ovpn = netdev_priv(dev);
@@ -99,6 +106,8 @@ static void ovpn_setup(struct net_device *dev)
 
 	dev->netdev_ops = &ovpn_netdev_ops;
 
+	dev->priv_destructor = ovpn_priv_free;
+
 	dev->hard_header_len = 0;
 	dev->addr_len = 0;
 	dev->mtu = ETH_DATA_LEN - OVPN_HEAD_ROOM;
@@ -120,12 +129,50 @@ static void ovpn_setup(struct net_device *dev)
 	SET_NETDEV_DEVTYPE(dev, &ovpn_type);
 }
 
+static int ovpn_mp_alloc(struct ovpn_priv *ovpn)
+{
+	struct in_device *dev_v4;
+	int i;
+
+	if (ovpn->mode != OVPN_MODE_MP)
+		return 0;
+
+	dev_v4 = __in_dev_get_rtnl(ovpn->dev);
+	if (dev_v4) {
+		/* disable redirects as Linux gets confused by ovpn
+		 * handling same-LAN routing.
+		 * This happens because a multipeer interface is used as
+		 * relay point between hosts in the same subnet, while
+		 * in a classic LAN this would not be needed because the
+		 * two hosts would be able to talk directly.
+		 */
+		IN_DEV_CONF_SET(dev_v4, SEND_REDIRECTS, false);
+		IPV4_DEVCONF_ALL(dev_net(ovpn->dev), SEND_REDIRECTS) = false;
+	}
+
+	/* the peer container is fairly large, therefore we allocate it only in
+	 * MP mode
+	 */
+	ovpn->peers = kzalloc(sizeof(*ovpn->peers), GFP_KERNEL);
+	if (!ovpn->peers)
+		return -ENOMEM;
+
+	for (i = 0; i < ARRAY_SIZE(ovpn->peers->by_id); i++) {
+		INIT_HLIST_HEAD(&ovpn->peers->by_id[i]);
+		INIT_HLIST_NULLS_HEAD(&ovpn->peers->by_vpn_addr[i], i);
+		INIT_HLIST_NULLS_HEAD(&ovpn->peers->by_transp_addr[i], i);
+	}
+
+	return 0;
+}
+
 static int ovpn_newlink(struct net *src_net, struct net_device *dev,
 			struct nlattr *tb[], struct nlattr *data[],
 			struct netlink_ext_ack *extack)
 {
 	struct ovpn_priv *ovpn = netdev_priv(dev);
 	enum ovpn_mode mode = OVPN_MODE_P2P;
+	int err;
 
 	if (data && data[IFLA_OVPN_MODE]) {
 		mode = nla_get_u8(data[IFLA_OVPN_MODE]);
@@ -136,6 +183,10 @@ static int ovpn_newlink(struct net *src_net, struct net_device *dev,
 	ovpn->mode = mode;
 	spin_lock_init(&ovpn->lock);
 
+	err = ovpn_mp_alloc(ovpn);
+	if (err < 0)
+		return err;
+
 	/* turn carrier explicitly off after registration, this way state is
 	 * clearly defined
 	 */
@@ -195,14 +246,26 @@ static int ovpn_netdev_notifier_call(struct notifier_block *nb,
 		netif_carrier_off(dev);
 		ovpn->registered = false;
 
-		if (ovpn->mode == OVPN_MODE_P2P)
+		switch (ovpn->mode) {
+		case OVPN_MODE_P2P:
 			ovpn_peer_release_p2p(ovpn,
 					      OVPN_DEL_PEER_REASON_TEARDOWN);
+			break;
+		case OVPN_MODE_MP:
+			ovpn_peers_free(ovpn, OVPN_DEL_PEER_REASON_TEARDOWN);
+			break;
+		}
 		break;
 	case NETDEV_DOWN:
-		if (ovpn->mode == OVPN_MODE_P2P)
+		switch (ovpn->mode) {
+		case OVPN_MODE_P2P:
 			ovpn_peer_release_p2p(ovpn,
 					      OVPN_DEL_PEER_REASON_ADMINDOWN);
+			break;
+		case OVPN_MODE_MP:
+			ovpn_peers_free(ovpn, OVPN_DEL_PEER_REASON_ADMINDOWN);
+			break;
+		}
 		break;
 	case NETDEV_POST_INIT:
 	case NETDEV_GOING_DOWN:
diff --git a/drivers/net/ovpn/ovpnstruct.h b/drivers/net/ovpn/ovpnstruct.h
index 7af1f21bb5a76acb34269693bcba5ce8f832137f..bca13e8e4439c2f217ae17896f114347e8aefd06 100644
--- a/drivers/net/ovpn/ovpnstruct.h
+++ b/drivers/net/ovpn/ovpnstruct.h
@@ -16,6 +16,20 @@
 #include <uapi/linux/if_link.h>
 #include <uapi/linux/ovpn.h>
 
+/**
+ * struct ovpn_peer_collection - container of peers for MultiPeer mode
+ * @by_id: table of peers index by ID
+ * @by_vpn_addr: table of peers indexed by VPN IP address (items can be
+ *		 rehashed on the fly due to peer IP change)
+ * @by_transp_addr: table of peers indexed by transport address (items can be
+ *		    rehashed on the fly due to peer IP change)
+ */
+struct ovpn_peer_collection {
+	DECLARE_HASHTABLE(by_id, 12);
+	struct hlist_nulls_head by_vpn_addr[1 << 12];
+	struct hlist_nulls_head by_transp_addr[1 << 12];
+};
+
 /**
  * struct ovpn_priv - per ovpn interface state
  * @dev: the actual netdev representing the tunnel
@@ -23,6 +37,7 @@
  * @registered: whether dev is still registered with netdev or not
  * @mode: device operation mode (i.e. p2p, mp, ..)
  * @lock: protect this object
+ * @peers: data structures holding multi-peer references
  * @peer: in P2P mode, this is the only remote peer
  * @gro_cells: pointer to the Generic Receive Offload cell
  */
@@ -32,6 +47,7 @@ struct ovpn_priv {
 	bool registered;
 	enum ovpn_mode mode;
 	spinlock_t lock; /* protect writing to the ovpn_priv object */
+	struct ovpn_peer_collection *peers;
 	struct ovpn_peer __rcu *peer;
 	struct gro_cells gro_cells;
 };
diff --git a/drivers/net/ovpn/peer.c b/drivers/net/ovpn/peer.c
index d730aba685101b59e126d2f0bd51debd65fbc037..956104183f40c7c44f4fbbb8f2a4c48748d6b56f 100644
--- a/drivers/net/ovpn/peer.c
+++ b/drivers/net/ovpn/peer.c
@@ -9,6 +9,7 @@
 
 #include <linux/skbuff.h>
 #include <linux/list.h>
+#include <linux/hashtable.h>
 
 #include "ovpnstruct.h"
 #include "bind.h"
@@ -265,7 +266,15 @@ struct ovpn_peer *ovpn_peer_get_by_id(struct ovpn_priv *ovpn, u32 peer_id)
 static void ovpn_peer_remove(struct ovpn_peer *peer,
 			     enum ovpn_del_peer_reason reason)
 {
+	lockdep_assert_held(&peer->ovpn->lock);
+
 	switch (peer->ovpn->mode) {
+	case OVPN_MODE_MP:
+		hlist_del_init_rcu(&peer->hash_entry_id);
+		hlist_nulls_del_init_rcu(&peer->hash_entry_addr4);
+		hlist_nulls_del_init_rcu(&peer->hash_entry_addr6);
+		hlist_nulls_del_init_rcu(&peer->hash_entry_transp_addr);
+		break;
 	case OVPN_MODE_P2P:
 		RCU_INIT_POINTER(peer->ovpn->peer, NULL);
 		/* in P2P mode the carrier is switched off when the peer is
@@ -273,8 +282,6 @@ static void ovpn_peer_remove(struct ovpn_peer *peer,
 		 */
 		netif_carrier_off(peer->ovpn->dev);
 		break;
-	default:
-		return;
 	}
 
 	peer->delete_reason = reason;
@@ -340,6 +347,89 @@ bool ovpn_peer_check_by_src(struct ovpn_priv *ovpn, struct sk_buff *skb,
 	return match;
 }
 
+#define ovpn_get_hash_head(_tbl, _key, _key_len) ({		\
+	typeof(_tbl) *__tbl = &(_tbl);				\
+	(&(*__tbl)[jhash(_key, _key_len, 0) % HASH_SIZE(*__tbl)]); }) \
+
+/**
+ * ovpn_peer_add_mp - add peer to related tables in a MP instance
+ * @ovpn: the instance to add the peer to
+ * @peer: the peer to add
+ *
+ * Return: 0 on success or a negative error code otherwise
+ */
+static int ovpn_peer_add_mp(struct ovpn_priv *ovpn, struct ovpn_peer *peer)
+{
+	struct sockaddr_storage sa = { 0 };
+	struct hlist_nulls_head *nhead;
+	struct sockaddr_in6 *sa6;
+	struct sockaddr_in *sa4;
+	struct ovpn_bind *bind;
+	struct ovpn_peer *tmp;
+	size_t salen;
+	int ret = 0;
+
+	spin_lock_bh(&ovpn->lock);
+	/* do not add duplicates */
+	tmp = ovpn_peer_get_by_id(ovpn, peer->id);
+	if (tmp) {
+		ovpn_peer_put(tmp);
+		ret = -EEXIST;
+		goto out;
+	}
+
+	bind = rcu_dereference_protected(peer->bind, true);
+	/* peers connected via TCP have bind == NULL */
+	if (bind) {
+		switch (bind->remote.in4.sin_family) {
+		case AF_INET:
+			sa4 = (struct sockaddr_in *)&sa;
+
+			sa4->sin_family = AF_INET;
+			sa4->sin_addr.s_addr = bind->remote.in4.sin_addr.s_addr;
+			sa4->sin_port = bind->remote.in4.sin_port;
+			salen = sizeof(*sa4);
+			break;
+		case AF_INET6:
+			sa6 = (struct sockaddr_in6 *)&sa;
+
+			sa6->sin6_family = AF_INET6;
+			sa6->sin6_addr = bind->remote.in6.sin6_addr;
+			sa6->sin6_port = bind->remote.in6.sin6_port;
+			salen = sizeof(*sa6);
+			break;
+		default:
+			ret = -EPROTONOSUPPORT;
+			goto out;
+		}
+
+		nhead = ovpn_get_hash_head(ovpn->peers->by_transp_addr, &sa,
+					   salen);
+		hlist_nulls_add_head_rcu(&peer->hash_entry_transp_addr, nhead);
+	}
+
+	hlist_add_head_rcu(&peer->hash_entry_id,
+			   ovpn_get_hash_head(ovpn->peers->by_id, &peer->id,
+					      sizeof(peer->id)));
+
+	if (peer->vpn_addrs.ipv4.s_addr != htonl(INADDR_ANY)) {
+		nhead = ovpn_get_hash_head(ovpn->peers->by_vpn_addr,
+					   &peer->vpn_addrs.ipv4,
+					   sizeof(peer->vpn_addrs.ipv4));
+		hlist_nulls_add_head_rcu(&peer->hash_entry_addr4, nhead);
+	}
+
+	if (!ipv6_addr_any(&peer->vpn_addrs.ipv6)) {
+		nhead = ovpn_get_hash_head(ovpn->peers->by_vpn_addr,
+					   &peer->vpn_addrs.ipv6,
+					   sizeof(peer->vpn_addrs.ipv6));
+		hlist_nulls_add_head_rcu(&peer->hash_entry_addr6, nhead);
+	}
+out:
+	spin_unlock_bh(&ovpn->lock);
+	return ret;
+}
+
 /**
  * ovpn_peer_add_p2p - add peer to related tables in a P2P instance
  * @ovpn: the instance to add the peer to
@@ -380,11 +470,40 @@ static int ovpn_peer_add_p2p(struct ovpn_priv *ovpn, struct ovpn_peer *peer)
 int ovpn_peer_add(struct ovpn_priv *ovpn, struct ovpn_peer *peer)
 {
 	switch (ovpn->mode) {
+	case OVPN_MODE_MP:
+		return ovpn_peer_add_mp(ovpn, peer);
 	case OVPN_MODE_P2P:
 		return ovpn_peer_add_p2p(ovpn, peer);
-	default:
-		return -EOPNOTSUPP;
 	}
+
+	return -EOPNOTSUPP;
+}
+
+/**
+ * ovpn_peer_del_mp - delete peer from related tables in a MP instance
+ * @peer: the peer to delete
+ * @reason: reason why the peer was deleted (sent to userspace)
+ *
+ * Return: 0 on success or a negative error code otherwise
+ */
+static int ovpn_peer_del_mp(struct ovpn_peer *peer,
+			    enum ovpn_del_peer_reason reason)
+{
+	struct ovpn_peer *tmp;
+	int ret = -ENOENT;
+
+	lockdep_assert_held(&peer->ovpn->lock);
+
+	tmp = ovpn_peer_get_by_id(peer->ovpn, peer->id);
+	if (tmp == peer) {
+		ovpn_peer_remove(peer, reason);
+		ret = 0;
+	}
+
+	if (tmp)
+		ovpn_peer_put(tmp);
+
+	return ret;
 }
 
 /**
@@ -440,10 +559,35 @@ void ovpn_peer_release_p2p(struct ovpn_priv *ovpn,
  */
 int ovpn_peer_del(struct ovpn_peer *peer, enum ovpn_del_peer_reason reason)
 {
+	int ret = -EOPNOTSUPP;
+
+	spin_lock_bh(&peer->ovpn->lock);
 	switch (peer->ovpn->mode) {
+	case OVPN_MODE_MP:
+		ret = ovpn_peer_del_mp(peer, reason);
+		break;
 	case OVPN_MODE_P2P:
-		return ovpn_peer_del_p2p(peer, reason);
-	default:
-		return -EOPNOTSUPP;
+		ret = ovpn_peer_del_p2p(peer, reason);
+		break;
 	}
+	spin_unlock_bh(&peer->ovpn->lock);
+	return ret;
+}
+
+/**
+ * ovpn_peers_free - free all peers in the instance
+ * @ovpn: the instance whose peers should be released
+ * @reason: the reason for releasing all peers
+ */
+void ovpn_peers_free(struct ovpn_priv *ovpn,
+		     enum ovpn_del_peer_reason reason)
+{
+	struct hlist_node *tmp;
+	struct ovpn_peer *peer;
+	int bkt;
+
+	spin_lock_bh(&ovpn->lock);
+	hash_for_each_safe(ovpn->peers->by_id, bkt, tmp, peer, hash_entry_id)
+		ovpn_peer_remove(peer, reason);
+	spin_unlock_bh(&ovpn->lock);
 }
diff --git a/drivers/net/ovpn/peer.h b/drivers/net/ovpn/peer.h
index 370657baf775e1cf6a88e5a117e4d599196f944d..1aa5be02d17f411484062e07c5c49f88bb9f0c98 100644
--- a/drivers/net/ovpn/peer.h
+++ b/drivers/net/ovpn/peer.h
@@ -23,6 +23,10 @@
  * @vpn_addrs: IP addresses assigned over the tunnel
  * @vpn_addrs.ipv4: IPv4 assigned to peer on the tunnel
  * @vpn_addrs.ipv6: IPv6 assigned to peer on the tunnel
+ * @hash_entry_id: entry in the peer ID hashtable
+ * @hash_entry_addr4: entry in the peer IPv4 hashtable
+ * @hash_entry_addr6: entry in the peer IPv6 hashtable
+ * @hash_entry_transp_addr: entry in the peer transport address hashtable
  * @sock: the socket being used to talk to this peer
  * @tcp: keeps track of TCP specific state
  * @tcp.strp: stream parser context (TCP only)
@@ -55,6 +59,10 @@ struct ovpn_peer {
 		struct in_addr ipv4;
 		struct in6_addr ipv6;
 	} vpn_addrs;
+	struct hlist_node hash_entry_id;
+	struct hlist_nulls_node hash_entry_addr4;
+	struct hlist_nulls_node hash_entry_addr6;
+	struct hlist_nulls_node hash_entry_transp_addr;
 	struct ovpn_socket *sock;
 
 	struct {
@@ -116,6 +124,7 @@ int ovpn_peer_add(struct ovpn_priv *ovpn, struct ovpn_peer *peer);
 int ovpn_peer_del(struct ovpn_peer *peer, enum ovpn_del_peer_reason reason);
 void ovpn_peer_release_p2p(struct ovpn_priv *ovpn,
 			   enum ovpn_del_peer_reason reason);
+void ovpn_peers_free(struct ovpn_priv *ovpn, enum ovpn_del_peer_reason reason);
 
 struct ovpn_peer *ovpn_peer_get_by_transp_addr(struct ovpn_priv *ovpn,
 					       struct sk_buff *skb);

-- 
2.45.2

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