Date: Mon, 24 Jun 2024 13:31:12 +0200
From: Antonio Quartulli <antonio@...nvpn.net>
To: netdev@...r.kernel.org
Cc: kuba@...nel.org,
	ryazanov.s.a@...il.com,
	pabeni@...hat.com,
	edumazet@...gle.com,
	andrew@...n.ch,
	sd@...asysnail.net,
	Antonio Quartulli <antonio@...nvpn.net>
Subject: [PATCH net-next v4 15/25] 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       |  41 ++++++++-
 drivers/net/ovpn/ovpnstruct.h |  16 ++++
 drivers/net/ovpn/peer.c       | 152 ++++++++++++++++++++++++++++++++++
 drivers/net/ovpn/peer.h       |   9 ++
 4 files changed, 216 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ovpn/main.c b/drivers/net/ovpn/main.c
index 19f7c0ff679b..cefd7010ab37 100644
--- a/drivers/net/ovpn/main.c
+++ b/drivers/net/ovpn/main.c
@@ -46,6 +46,17 @@ static int ovpn_struct_init(struct net_device *dev, enum ovpn_mode mode)
 	ovpn->mode = mode;
 	spin_lock_init(&ovpn->lock);
 
+	if (mode == OVPN_MODE_MP) {
+		/* 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)
+			return -ENOMEM;
+
+		spin_lock_init(&ovpn->peers->lock);
+	}
+
 	return 0;
 }
 
@@ -54,14 +65,34 @@ 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);
 	rcu_barrier();
 }
 
 static int ovpn_net_init(struct net_device *dev)
 {
 	struct ovpn_struct *ovpn = netdev_priv(dev);
+	int err = gro_cells_init(&ovpn->gro_cells, dev);
+	struct in_device *dev_v4;
+
+	if (err)
+		return err;
 
-	return gro_cells_init(&ovpn->gro_cells, dev);
+	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;
+		}
+	}
+	return 0;
 }
 
 static int ovpn_net_open(struct net_device *dev)
@@ -210,8 +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 af39ee86f168..482e02b918e4 100644
--- a/drivers/net/ovpn/ovpnstruct.h
+++ b/drivers/net/ovpn/ovpnstruct.h
@@ -13,12 +13,27 @@
 #include <net/gro_cells.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_transp_addr: table of peers indexed by transport address
+ * @by_vpn_addr: table of peers indexed by VPN IP address
+ * @lock: protects writes to peers tables
+ */
+struct ovpn_peer_collection {
+	DECLARE_HASHTABLE(by_id, 12);
+	DECLARE_HASHTABLE(by_transp_addr, 12);
+	DECLARE_HASHTABLE(by_vpn_addr, 12);
+	spinlock_t lock; /* protects writes to peers tables */
+};
+
 /**
  * struct ovpn_struct - per ovpn interface state
  * @dev: the actual netdev representing the tunnel
  * @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
@@ -28,6 +43,7 @@ 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 f633b70bb140..2b5e2bbb2578 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"
@@ -311,6 +312,90 @@ bool ovpn_peer_check_by_src(struct ovpn_struct *ovpn, struct sk_buff *skb,
 	return match;
 }
 
+/**
+ * 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 sockaddr_in6 *sa6;
+	struct sockaddr_in *sa4;
+	struct ovpn_bind *bind;
+	struct ovpn_peer *tmp;
+	size_t salen;
+	int ret = 0;
+	u32 index;
+
+	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 unlock;
+	}
+
+	bind = rcu_dereference_protected(peer->bind, true);
+	/* peers connected via TCP have bind == NULL */
+	if (bind) {
+		switch (bind->sa.in4.sin_family) {
+		case AF_INET:
+			sa4 = (struct sockaddr_in *)&sa;
+
+			sa4->sin_family = AF_INET;
+			sa4->sin_addr.s_addr = bind->sa.in4.sin_addr.s_addr;
+			sa4->sin_port = bind->sa.in4.sin_port;
+			salen = sizeof(*sa4);
+			break;
+		case AF_INET6:
+			sa6 = (struct sockaddr_in6 *)&sa;
+
+			sa6->sin6_family = AF_INET6;
+			sa6->sin6_addr = bind->sa.in6.sin6_addr;
+			sa6->sin6_port = bind->sa.in6.sin6_port;
+			salen = sizeof(*sa6);
+			break;
+		default:
+			ret = -EPROTONOSUPPORT;
+			goto unlock;
+		}
+
+		index = ovpn_peer_index(ovpn->peers->by_transp_addr, &sa,
+					salen);
+		hlist_add_head_rcu(&peer->hash_entry_transp_addr,
+				   &ovpn->peers->by_transp_addr[index]);
+	}
+
+	index = ovpn_peer_index(ovpn->peers->by_id, &peer->id,
+				sizeof(peer->id));
+	hlist_add_head_rcu(&peer->hash_entry_id, &ovpn->peers->by_id[index]);
+
+	if (peer->vpn_addrs.ipv4.s_addr != htonl(INADDR_ANY)) {
+		index = ovpn_peer_index(ovpn->peers->by_vpn_addr,
+					&peer->vpn_addrs.ipv4,
+					sizeof(peer->vpn_addrs.ipv4));
+		hlist_add_head_rcu(&peer->hash_entry_addr4,
+				   &ovpn->peers->by_vpn_addr[index]);
+	}
+
+	if (!ipv6_addr_any(&peer->vpn_addrs.ipv6)) {
+		index = ovpn_peer_index(ovpn->peers->by_vpn_addr,
+					&peer->vpn_addrs.ipv6,
+					sizeof(peer->vpn_addrs.ipv6));
+		hlist_add_head_rcu(&peer->hash_entry_addr6,
+				   &ovpn->peers->by_vpn_addr[index]);
+	}
+
+unlock:
+	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
@@ -351,6 +436,8 @@ 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:
@@ -358,6 +445,53 @@ 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)
+{
+	hlist_del_init_rcu(&peer->hash_entry_id);
+	hlist_del_init_rcu(&peer->hash_entry_addr4);
+	hlist_del_init_rcu(&peer->hash_entry_addr6);
+	hlist_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)
+{
+	struct ovpn_peer *tmp;
+	int ret = 0;
+
+	spin_lock_bh(&peer->ovpn->peers->lock);
+	tmp = ovpn_peer_get_by_id(peer->ovpn, peer->id);
+	if (tmp != peer) {
+		ret = -ENOENT;
+		goto unlock;
+	}
+	ovpn_peer_unhash(peer, reason);
+
+unlock:
+	spin_unlock_bh(&peer->ovpn->peers->lock);
+
+	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
@@ -415,9 +549,27 @@ void ovpn_peer_release_p2p(struct ovpn_struct *ovpn)
 int ovpn_peer_del(struct ovpn_peer *peer, enum ovpn_del_peer_reason reason)
 {
 	switch (peer->ovpn->mode) {
+	case OVPN_MODE_MP:
+		return ovpn_peer_del_mp(peer, reason);
 	case OVPN_MODE_P2P:
 		return ovpn_peer_del_p2p(peer, reason);
 	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 86d4696b1529..6e92e09a3504 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_node hash_entry_addr4;
+	struct hlist_node hash_entry_addr6;
+	struct hlist_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);
-- 
2.44.2

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