[PATCH net-next v18 15/25] ovpn: implement multi-peer support

Antonio Quartulli
2025-01-13T09:31:24Z

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@openvpn.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 f6636cf4c287928ec005c94ad011f978b609069e..3ba01159afd237edf5941f3af194be8f292f37d9 100644
--- a/drivers/net/ovpn/ovpnstruct.h
+++ b/drivers/net/ovpn/ovpnstruct.h
@@ -15,12 +15,27 @@
#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
* @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
*/
@@ -29,6 +44,7 @@ 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 85505fd9fd72cf10aea792bab92eaa8228075cf5..ae712b64e5092cc5759fb7141d98444dbde7aac7 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"
@@ -280,7 +281,15 @@ static void ovpn_peer_remove_work(struct work_struct *work)
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
@@ -288,8 +297,6 @@ static void ovpn_peer_remove(struct ovpn_peer *peer,
*/
netif_carrier_off(peer->ovpn->dev);
break;
- default:
- return;
}

peer->delete_reason = reason;
@@ -353,6 +360,89 @@ 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
@@ -393,11 +483,40 @@ 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;
}

/**
@@ -453,10 +572,35 @@ 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 f3c5ad969fdad337afda23dd993805ed342cb218..52632215bb531b3dec4e0dae358f4e315cf33d7b 100644
--- a/drivers/net/ovpn/peer.h
+++ b/drivers/net/ovpn/peer.h
@@ -25,6 +25,10 @@
* @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)
@@ -58,6 +62,10 @@ 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 {
@@ -119,6 +127,7 @@ 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