Message-Id: <20241002-b4-ovpn-v8-14-37ceffcffbde@openvpn.net>
Date: Wed, 02 Oct 2024 11:02:28 +0200
From: Antonio Quartulli <antonio@...nvpn.net>
To: 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>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, sd@...asysnail.net, ryazanov.s.a@...il.com
Subject: [PATCH net-next v8 14/24] 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       |  50 +++++++++++-
 drivers/net/ovpn/ovpnstruct.h |  19 +++++
 drivers/net/ovpn/peer.c       | 173 ++++++++++++++++++++++++++++++++++++++++--
 drivers/net/ovpn/peer.h       |   9 +++
 4 files changed, 241 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ovpn/main.c b/drivers/net/ovpn/main.c
index cb5cc3d4b5620f5a1e401e06e52e67c32e57aa78..7604f0970d3c283f8680f6800a125427999bb174 100644
--- a/drivers/net/ovpn/main.c
+++ b/drivers/net/ovpn/main.c
@@ -50,13 +50,53 @@ static void ovpn_struct_free(struct net_device *net)
 	struct ovpn_struct *ovpn = netdev_priv(net);
 
 	gro_cells_destroy(&ovpn->gro_cells);
+	kfree(ovpn->peers);
 }
 
 static int ovpn_net_init(struct net_device *dev)
 {
 	struct ovpn_struct *ovpn = netdev_priv(dev);
+	struct in_device *dev_v4;
+	int i, err;
 
-	return gro_cells_init(&ovpn->gro_cells, dev);
+	err = gro_cells_init(&ovpn->gro_cells, dev);
+	if (err)
+		return err;
+
+	if (ovpn->mode == OVPN_MODE_MP) {
+		dev_v4 = __in_dev_get_rtnl(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(dev), SEND_REDIRECTS) = false;
+		}
+
+		/* the peer container is fairly large, therefore we dynamically
+		 * allocate it only when needed
+		 */
+		ovpn->peers = kzalloc(sizeof(*ovpn->peers), GFP_KERNEL);
+		if (!ovpn->peers) {
+			gro_cells_destroy(&ovpn->gro_cells);
+			return -ENOMEM;
+		}
+
+		spin_lock_init(&ovpn->peers->lock);
+
+		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_net_open(struct net_device *dev)
@@ -201,8 +241,14 @@ void ovpn_iface_destruct(struct ovpn_struct *ovpn)
 
 	ovpn->registered = false;
 
-	if (ovpn->mode == OVPN_MODE_P2P)
+	switch (ovpn->mode) {
+	case OVPN_MODE_P2P:
 		ovpn_peer_release_p2p(ovpn);
+		break;
+	default:
+		ovpn_peers_free(ovpn);
+		break;
+	}
 }
 
 static int ovpn_netdev_notifier_call(struct notifier_block *nb,
diff --git a/drivers/net/ovpn/ovpnstruct.h b/drivers/net/ovpn/ovpnstruct.h
index 65497ce115aa4be719ed03f89135a80b73f9ef9b..4373d1bbc4874dc2f1d1f1697e7b847ec2f486c9 100644
--- a/drivers/net/ovpn/ovpnstruct.h
+++ b/drivers/net/ovpn/ovpnstruct.h
@@ -14,6 +14,23 @@
 #include <net/net_trackers.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)
+ * @lock: protects writes to peer tables
+ */
+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];
+
+	spinlock_t lock; /* protects writes to peer tables */
+};
+
 /**
  * struct ovpn_struct - per ovpn interface state
  * @dev: the actual netdev representing the tunnel
@@ -21,6 +38,7 @@
  * @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
  * @dev_list: entry for the module wide device list
  * @gro_cells: pointer to the Generic Receive Offload cell
@@ -31,6 +49,7 @@ struct ovpn_struct {
 	bool registered;
 	enum ovpn_mode mode;
 	spinlock_t lock; /* protect writing to the ovpn_struct object */
+	struct ovpn_peer_collection *peers;
 	struct ovpn_peer __rcu *peer;
 	struct list_head dev_list;
 	struct gro_cells gro_cells;
diff --git a/drivers/net/ovpn/peer.c b/drivers/net/ovpn/peer.c
index 6d34c56a4a51ce407b20b6175e6140aafc4b4e33..3c6fbf99f696c18d8a2dbe169c7f6f5933fb71ac 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"
@@ -65,13 +66,12 @@ struct ovpn_peer *ovpn_peer_new(struct ovpn_struct *ovpn, u32 id)
 }
 
 /**
- * ovpn_peer_release - release peer private members
- * @peer: the peer to release
+ * ovpn_peer_release_rcu - release peer private members
+ * @head: RCU head belonging to peer being released
  */
-static void ovpn_peer_release(struct ovpn_peer *peer)
+static void ovpn_peer_release_rcu(struct rcu_head *head)
 {
-	if (peer->sock)
-		ovpn_socket_put(peer->sock);
+	struct ovpn_peer *peer = container_of(head, struct ovpn_peer, rcu);
 
 	ovpn_crypto_state_release(&peer->crypto);
 	ovpn_bind_reset(peer, NULL);
@@ -86,9 +86,10 @@ void ovpn_peer_release_kref(struct kref *kref)
 {
 	struct ovpn_peer *peer = container_of(kref, struct ovpn_peer, refcount);
 
-	ovpn_peer_release(peer);
+	if (peer->sock)
+		ovpn_socket_put(peer->sock);
 	netdev_put(peer->ovpn->dev, &peer->ovpn->dev_tracker);
-	kfree_rcu(peer, rcu);
+	call_rcu(&peer->rcu, ovpn_peer_release_rcu);
 }
 
 /**
@@ -309,6 +310,89 @@ bool ovpn_peer_check_by_src(struct ovpn_struct *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_struct *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->peers->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->peers->lock);
+	return ret;
+}
+
 /**
  * ovpn_peer_add_p2p - add peer to related tables in a P2P instance
  * @ovpn: the instance to add the peer to
@@ -349,6 +433,8 @@ static int ovpn_peer_add_p2p(struct ovpn_struct *ovpn, struct ovpn_peer *peer)
 int ovpn_peer_add(struct ovpn_struct *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:
@@ -356,6 +442,51 @@ int ovpn_peer_add(struct ovpn_struct *ovpn, struct ovpn_peer *peer)
 	}
 }
 
+/**
+ * ovpn_peer_unhash - remove peer reference from all hashtables
+ * @peer: the peer to remove
+ * @reason: the delete reason to attach to the peer
+ */
+static void ovpn_peer_unhash(struct ovpn_peer *peer,
+			     enum ovpn_del_peer_reason reason)
+	__must_hold(&ovpn->peers->lock)
+{
+	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);
+
+	ovpn_peer_put(peer);
+	peer->delete_reason = reason;
+}
+
+/**
+ * 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)
+	__must_hold(&peer->ovpn->peers->lock)
+{
+	struct ovpn_peer *tmp;
+	int ret = -ENOENT;
+
+	tmp = ovpn_peer_get_by_id(peer->ovpn, peer->id);
+	if (tmp == peer) {
+		ovpn_peer_unhash(peer, reason);
+		ret = 0;
+	}
+
+	if (tmp)
+		ovpn_peer_put(tmp);
+
+	return ret;
+}
+
 /**
  * ovpn_peer_del_p2p - delete peer from related tables in a P2P instance
  * @peer: the peer to delete
@@ -411,10 +542,36 @@ void ovpn_peer_release_p2p(struct ovpn_struct *ovpn)
  */
 int ovpn_peer_del(struct ovpn_peer *peer, enum ovpn_del_peer_reason reason)
 {
+	int ret;
+
 	switch (peer->ovpn->mode) {
+	case OVPN_MODE_MP:
+		spin_lock_bh(&peer->ovpn->peers->lock);
+		ret = ovpn_peer_del_mp(peer, reason);
+		spin_unlock_bh(&peer->ovpn->peers->lock);
+		return ret;
 	case OVPN_MODE_P2P:
-		return ovpn_peer_del_p2p(peer, reason);
+		spin_lock_bh(&peer->ovpn->lock);
+		ret = ovpn_peer_del_p2p(peer, reason);
+		spin_unlock_bh(&peer->ovpn->lock);
+		return ret;
 	default:
 		return -EOPNOTSUPP;
 	}
 }
+
+/**
+ * ovpn_peers_free - free all peers in the instance
+ * @ovpn: the instance whose peers should be released
+ */
+void ovpn_peers_free(struct ovpn_struct *ovpn)
+{
+	struct hlist_node *tmp;
+	struct ovpn_peer *peer;
+	int bkt;
+
+	spin_lock_bh(&ovpn->peers->lock);
+	hash_for_each_safe(ovpn->peers->by_id, bkt, tmp, peer, hash_entry_id)
+		ovpn_peer_unhash(peer, OVPN_DEL_PEER_REASON_TEARDOWN);
+	spin_unlock_bh(&ovpn->peers->lock);
+}
diff --git a/drivers/net/ovpn/peer.h b/drivers/net/ovpn/peer.h
index 86d4696b1529c45025b63d2973fc48ca81ca8f63..9481eb41742ca2a6c88ee0262dd448fd947614fd 100644
--- a/drivers/net/ovpn/peer.h
+++ b/drivers/net/ovpn/peer.h
@@ -30,6 +30,10 @@
  * @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)
@@ -62,6 +66,10 @@ 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;
 
 	/* state of the TCP reading. Needed to keep track of how much of a
@@ -126,6 +134,7 @@ struct ovpn_peer *ovpn_peer_new(struct ovpn_struct *ovpn, u32 id);
 int ovpn_peer_add(struct ovpn_struct *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_struct *ovpn);
+void ovpn_peers_free(struct ovpn_struct *ovpn);
 
 struct ovpn_peer *ovpn_peer_get_by_transp_addr(struct ovpn_struct *ovpn,
 					       struct sk_buff *skb);

-- 
2.45.2

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