mptcp: add netlink-based PM

Expose a new netlink family to userspace to control the PM, setting:

 - list of local addresses to be signalled.
 - list of local addresses used to created subflows.
 - maximum number of add_addr option to react

When the msk is fully established, the PM netlink attempts to
announce the 'signal' list via the ADD_ADDR option. Since we
currently lack the ADD_ADDR echo (and related event) only the
first addr is sent.

After exhausting the 'announce' list, the PM tries to create
subflow for each addr in 'local' list, waiting for each
connection to be completed before attempting the next one.

Idea is to add an additional PM hook for ADD_ADDR echo, to allow
the PM netlink announcing multiple addresses, in sequence.

Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 874 insertions, 2 deletions

diff --git a/net/mptcp/Makefile b/net/mptcp/Makefile
index faebe8ec9f73..baa0640527c7 100644
--- a/net/mptcp/Makefile
+++ b/net/mptcp/Makefile
@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_MPTCP) += mptcp.o
 
-mptcp-y := protocol.o subflow.o options.o token.o crypto.o ctrl.o pm.o diag.o mib.o
+mptcp-y := protocol.o subflow.o options.o token.o crypto.o ctrl.o pm.o diag.o \
+	   mib.o pm_netlink.o
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 3aedad58778c..064639f72487 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -176,7 +176,7 @@ out_unlock:
 
 int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc)
 {
-	return 0;
+	return mptcp_pm_nl_get_local_id(msk, skc);
 }
 
 static void pm_worker(struct work_struct *work)
@@ -192,12 +192,15 @@ static void pm_worker(struct work_struct *work)
 	pr_debug("msk=%p status=%x", msk, pm->status);
 	if (pm->status & BIT(MPTCP_PM_ADD_ADDR_RECEIVED)) {
 		pm->status &= ~BIT(MPTCP_PM_ADD_ADDR_RECEIVED);
+		mptcp_pm_nl_add_addr_received(msk);
 	}
 	if (pm->status & BIT(MPTCP_PM_ESTABLISHED)) {
 		pm->status &= ~BIT(MPTCP_PM_ESTABLISHED);
+		mptcp_pm_nl_fully_established(msk);
 	}
 	if (pm->status & BIT(MPTCP_PM_SUBFLOW_ESTABLISHED)) {
 		pm->status &= ~BIT(MPTCP_PM_SUBFLOW_ESTABLISHED);
+		mptcp_pm_nl_subflow_established(msk);
 	}
 
 	spin_unlock_bh(&msk->pm.lock);
@@ -219,6 +222,8 @@ void mptcp_pm_data_init(struct mptcp_sock *msk)
 
 	spin_lock_init(&msk->pm.lock);
 	INIT_WORK(&msk->pm.work, pm_worker);
+
+	mptcp_pm_nl_data_init(msk);
 }
 
 void mptcp_pm_close(struct mptcp_sock *msk)
@@ -232,4 +237,6 @@ void mptcp_pm_init(void)
 	pm_wq = alloc_workqueue("pm_wq", WQ_UNBOUND | WQ_MEM_RECLAIM, 8);
 	if (!pm_wq)
 		panic("Failed to allocate workqueue");
+
+	mptcp_pm_nl_init();
 }
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
new file mode 100644
index 000000000000..a0ce7f324499
--- /dev/null
+++ b/net/mptcp/pm_netlink.c
@@ -0,0 +1,857 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Multipath TCP
+ *
+ * Copyright (c) 2020, Red Hat, Inc.
+ */
+
+#include <linux/inet.h>
+#include <linux/kernel.h>
+#include <net/tcp.h>
+#include <net/netns/generic.h>
+#include <net/mptcp.h>
+#include <net/genetlink.h>
+#include <uapi/linux/mptcp.h>
+
+#include "protocol.h"
+
+/* forward declaration */
+static struct genl_family mptcp_genl_family;
+
+static int pm_nl_pernet_id;
+
+struct mptcp_pm_addr_entry {
+	struct list_head	list;
+	unsigned int		flags;
+	int			ifindex;
+	struct mptcp_addr_info	addr;
+	struct rcu_head		rcu;
+};
+
+struct pm_nl_pernet {
+	/* protects pernet updates */
+	spinlock_t		lock;
+	struct list_head	local_addr_list;
+	unsigned int		addrs;
+	unsigned int		add_addr_signal_max;
+	unsigned int		add_addr_accept_max;
+	unsigned int		local_addr_max;
+	unsigned int		subflows_max;
+	unsigned int		next_id;
+};
+
+#define MPTCP_PM_ADDR_MAX	8
+
+static bool addresses_equal(const struct mptcp_addr_info *a,
+			    struct mptcp_addr_info *b, bool use_port)
+{
+	bool addr_equals = false;
+
+	if (a->family != b->family)
+		return false;
+
+	if (a->family == AF_INET)
+		addr_equals = a->addr.s_addr == b->addr.s_addr;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else
+		addr_equals = !ipv6_addr_cmp(&a->addr6, &b->addr6);
+#endif
+
+	if (!addr_equals)
+		return false;
+	if (!use_port)
+		return true;
+
+	return a->port == b->port;
+}
+
+static void local_address(const struct sock_common *skc,
+			  struct mptcp_addr_info *addr)
+{
+	addr->port = 0;
+	addr->family = skc->skc_family;
+	if (addr->family == AF_INET)
+		addr->addr.s_addr = skc->skc_rcv_saddr;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (addr->family == AF_INET6)
+		addr->addr6 = skc->skc_v6_rcv_saddr;
+#endif
+}
+
+static void remote_address(const struct sock_common *skc,
+			   struct mptcp_addr_info *addr)
+{
+	addr->family = skc->skc_family;
+	addr->port = skc->skc_dport;
+	if (addr->family == AF_INET)
+		addr->addr.s_addr = skc->skc_daddr;
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (addr->family == AF_INET6)
+		addr->addr6 = skc->skc_v6_daddr;
+#endif
+}
+
+static bool lookup_subflow_by_saddr(const struct list_head *list,
+				    struct mptcp_addr_info *saddr)
+{
+	struct mptcp_subflow_context *subflow;
+	struct mptcp_addr_info cur;
+	struct sock_common *skc;
+
+	list_for_each_entry(subflow, list, node) {
+		skc = (struct sock_common *)mptcp_subflow_tcp_sock(subflow);
+
+		local_address(skc, &cur);
+		if (addresses_equal(&cur, saddr, false))
+			return true;
+	}
+
+	return false;
+}
+
+static struct mptcp_pm_addr_entry *
+select_local_address(const struct pm_nl_pernet *pernet,
+		     struct mptcp_sock *msk)
+{
+	struct mptcp_pm_addr_entry *entry, *ret = NULL;
+
+	rcu_read_lock();
+	spin_lock_bh(&msk->join_list_lock);
+	list_for_each_entry_rcu(entry, &pernet->local_addr_list, list) {
+		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW))
+			continue;
+
+		/* avoid any address already in use by subflows and
+		 * pending join
+		 */
+		if (entry->addr.family == ((struct sock *)msk)->sk_family &&
+		    !lookup_subflow_by_saddr(&msk->conn_list, &entry->addr) &&
+		    !lookup_subflow_by_saddr(&msk->join_list, &entry->addr)) {
+			ret = entry;
+			break;
+		}
+	}
+	spin_unlock_bh(&msk->join_list_lock);
+	rcu_read_unlock();
+	return ret;
+}
+
+static struct mptcp_pm_addr_entry *
+select_signal_address(struct pm_nl_pernet *pernet, unsigned int pos)
+{
+	struct mptcp_pm_addr_entry *entry, *ret = NULL;
+	int i = 0;
+
+	rcu_read_lock();
+	/* do not keep any additional per socket state, just signal
+	 * the address list in order.
+	 * Note: removal from the local address list during the msk life-cycle
+	 * can lead to additional addresses not being announced.
+	 */
+	list_for_each_entry_rcu(entry, &pernet->local_addr_list, list) {
+		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL))
+			continue;
+		if (i++ == pos) {
+			ret = entry;
+			break;
+		}
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
+static void check_work_pending(struct mptcp_sock *msk)
+{
+	if (msk->pm.add_addr_signaled == msk->pm.add_addr_signal_max &&
+	    (msk->pm.local_addr_used == msk->pm.local_addr_max ||
+	     msk->pm.subflows == msk->pm.subflows_max))
+		WRITE_ONCE(msk->pm.work_pending, false);
+}
+
+static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct mptcp_pm_addr_entry *local;
+	struct mptcp_addr_info remote;
+	struct pm_nl_pernet *pernet;
+
+	pernet = net_generic(sock_net((struct sock *)msk), pm_nl_pernet_id);
+
+	pr_debug("local %d:%d signal %d:%d subflows %d:%d\n",
+		 msk->pm.local_addr_used, msk->pm.local_addr_max,
+		 msk->pm.add_addr_signaled, msk->pm.add_addr_signal_max,
+		 msk->pm.subflows, msk->pm.subflows_max);
+
+	/* check first for announce */
+	if (msk->pm.add_addr_signaled < msk->pm.add_addr_signal_max) {
+		local = select_signal_address(pernet,
+					      msk->pm.add_addr_signaled);
+
+		if (local) {
+			msk->pm.add_addr_signaled++;
+			mptcp_pm_announce_addr(msk, &local->addr);
+		} else {
+			/* pick failed, avoid fourther attempts later */
+			msk->pm.local_addr_used = msk->pm.add_addr_signal_max;
+		}
+
+		check_work_pending(msk);
+	}
+
+	/* check if should create a new subflow */
+	if (msk->pm.local_addr_used < msk->pm.local_addr_max &&
+	    msk->pm.subflows < msk->pm.subflows_max) {
+		remote_address((struct sock_common *)sk, &remote);
+
+		local = select_local_address(pernet, msk);
+		if (local) {
+			msk->pm.local_addr_used++;
+			msk->pm.subflows++;
+			check_work_pending(msk);
+			spin_unlock_bh(&msk->pm.lock);
+			__mptcp_subflow_connect(sk, local->ifindex,
+						&local->addr, &remote);
+			spin_lock_bh(&msk->pm.lock);
+			return;
+		}
+
+		/* lookup failed, avoid fourther attempts later */
+		msk->pm.local_addr_used = msk->pm.local_addr_max;
+		check_work_pending(msk);
+	}
+}
+
+void mptcp_pm_nl_fully_established(struct mptcp_sock *msk)
+{
+	mptcp_pm_create_subflow_or_signal_addr(msk);
+}
+
+void mptcp_pm_nl_subflow_established(struct mptcp_sock *msk)
+{
+	mptcp_pm_create_subflow_or_signal_addr(msk);
+}
+
+void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk)
+{
+	struct sock *sk = (struct sock *)msk;
+	struct mptcp_addr_info remote;
+	struct mptcp_addr_info local;
+
+	pr_debug("accepted %d:%d remote family %d",
+		 msk->pm.add_addr_accepted, msk->pm.add_addr_accept_max,
+		 msk->pm.remote.family);
+	msk->pm.add_addr_accepted++;
+	msk->pm.subflows++;
+	if (msk->pm.add_addr_accepted >= msk->pm.add_addr_accept_max ||
+	    msk->pm.subflows >= msk->pm.subflows_max)
+		WRITE_ONCE(msk->pm.accept_addr, false);
+
+	/* connect to the specified remote address, using whatever
+	 * local address the routing configuration will pick.
+	 */
+	remote = msk->pm.remote;
+	if (!remote.port)
+		remote.port = sk->sk_dport;
+	memset(&local, 0, sizeof(local));
+	local.family = remote.family;
+
+	spin_unlock_bh(&msk->pm.lock);
+	__mptcp_subflow_connect((struct sock *)msk, 0, &local, &remote);
+	spin_lock_bh(&msk->pm.lock);
+}
+
+static bool address_use_port(struct mptcp_pm_addr_entry *entry)
+{
+	return (entry->flags &
+		(MPTCP_PM_ADDR_FLAG_SIGNAL | MPTCP_PM_ADDR_FLAG_SUBFLOW)) ==
+		MPTCP_PM_ADDR_FLAG_SIGNAL;
+}
+
+static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet,
+					     struct mptcp_pm_addr_entry *entry)
+{
+	struct mptcp_pm_addr_entry *cur;
+	int ret = -EINVAL;
+
+	spin_lock_bh(&pernet->lock);
+	/* to keep the code simple, don't do IDR-like allocation for address ID,
+	 * just bail when we exceed limits
+	 */
+	if (pernet->next_id > 255)
+		goto out;
+	if (pernet->addrs >= MPTCP_PM_ADDR_MAX)
+		goto out;
+
+	/* do not insert duplicate address, differentiate on port only
+	 * singled addresses
+	 */
+	list_for_each_entry(cur, &pernet->local_addr_list, list) {
+		if (addresses_equal(&cur->addr, &entry->addr,
+				    address_use_port(entry) &&
+				    address_use_port(cur)))
+			goto out;
+	}
+
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL)
+		pernet->add_addr_signal_max++;
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
+		pernet->local_addr_max++;
+
+	entry->addr.id = pernet->next_id++;
+	pernet->addrs++;
+	list_add_tail_rcu(&entry->list, &pernet->local_addr_list);
+	ret = entry->addr.id;
+
+out:
+	spin_unlock_bh(&pernet->lock);
+	return ret;
+}
+
+int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk, struct sock_common *skc)
+{
+	struct mptcp_pm_addr_entry *entry;
+	struct mptcp_addr_info skc_local;
+	struct mptcp_addr_info msk_local;
+	struct pm_nl_pernet *pernet;
+	int ret = -1;
+
+	if (WARN_ON_ONCE(!msk))
+		return -1;
+
+	/* The 0 ID mapping is defined by the first subflow, copied into the msk
+	 * addr
+	 */
+	local_address((struct sock_common *)msk, &msk_local);
+	local_address((struct sock_common *)msk, &skc_local);
+	if (addresses_equal(&msk_local, &skc_local, false))
+		return 0;
+
+	pernet = net_generic(sock_net((struct sock *)msk), pm_nl_pernet_id);
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(entry, &pernet->local_addr_list, list) {
+		if (addresses_equal(&entry->addr, &skc_local, false)) {
+			ret = entry->addr.id;
+			break;
+		}
+	}
+	rcu_read_unlock();
+	if (ret >= 0)
+		return ret;
+
+	/* address not found, add to local list */
+	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->flags = 0;
+	entry->addr = skc_local;
+	ret = mptcp_pm_nl_append_new_local_addr(pernet, entry);
+	if (ret < 0)
+		kfree(entry);
+
+	return ret;
+}
+
+void mptcp_pm_nl_data_init(struct mptcp_sock *msk)
+{
+	struct mptcp_pm_data *pm = &msk->pm;
+	struct pm_nl_pernet *pernet;
+	bool subflows;
+
+	pernet = net_generic(sock_net((struct sock *)msk), pm_nl_pernet_id);
+
+	pm->add_addr_signal_max = READ_ONCE(pernet->add_addr_signal_max);
+	pm->add_addr_accept_max = READ_ONCE(pernet->add_addr_accept_max);
+	pm->local_addr_max = READ_ONCE(pernet->local_addr_max);
+	pm->subflows_max = READ_ONCE(pernet->subflows_max);
+	subflows = !!pm->subflows_max;
+	WRITE_ONCE(pm->work_pending, (!!pm->local_addr_max && subflows) ||
+		   !!pm->add_addr_signal_max);
+	WRITE_ONCE(pm->accept_addr, !!pm->add_addr_accept_max && subflows);
+	WRITE_ONCE(pm->accept_subflow, subflows);
+}
+
+#define MPTCP_PM_CMD_GRP_OFFSET	0
+
+static const struct genl_multicast_group mptcp_pm_mcgrps[] = {
+	[MPTCP_PM_CMD_GRP_OFFSET]	= { .name = MPTCP_PM_CMD_GRP_NAME, },
+};
+
+static const struct nla_policy
+mptcp_pm_addr_policy[MPTCP_PM_ADDR_ATTR_MAX + 1] = {
+	[MPTCP_PM_ADDR_ATTR_FAMILY]	= { .type	= NLA_U16,	},
+	[MPTCP_PM_ADDR_ATTR_ID]		= { .type	= NLA_U8,	},
+	[MPTCP_PM_ADDR_ATTR_ADDR4]	= { .type	= NLA_U32,	},
+	[MPTCP_PM_ADDR_ATTR_ADDR6]	= { .type	= NLA_EXACT_LEN,
+					    .len   = sizeof(struct in6_addr), },
+	[MPTCP_PM_ADDR_ATTR_PORT]	= { .type	= NLA_U16	},
+	[MPTCP_PM_ADDR_ATTR_FLAGS]	= { .type	= NLA_U32	},
+	[MPTCP_PM_ADDR_ATTR_IF_IDX]     = { .type	= NLA_S32	},
+};
+
+static const struct nla_policy mptcp_pm_policy[MPTCP_PM_ATTR_MAX + 1] = {
+	[MPTCP_PM_ATTR_ADDR]		=
+					NLA_POLICY_NESTED(mptcp_pm_addr_policy),
+	[MPTCP_PM_ATTR_RCV_ADD_ADDRS]	= { .type	= NLA_U32,	},
+	[MPTCP_PM_ATTR_SUBFLOWS]	= { .type	= NLA_U32,	},
+};
+
+static int mptcp_pm_family_to_addr(int family)
+{
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (family == AF_INET6)
+		return MPTCP_PM_ADDR_ATTR_ADDR6;
+#endif
+	return MPTCP_PM_ADDR_ATTR_ADDR4;
+}
+
+static int mptcp_pm_parse_addr(struct nlattr *attr, struct genl_info *info,
+			       bool require_family,
+			       struct mptcp_pm_addr_entry *entry)
+{
+	struct nlattr *tb[MPTCP_PM_ADDR_ATTR_MAX + 1];
+	int err, addr_addr;
+
+	if (!attr) {
+		GENL_SET_ERR_MSG(info, "missing address info");
+		return -EINVAL;
+	}
+
+	/* no validation needed - was already done via nested policy */
+	err = nla_parse_nested_deprecated(tb, MPTCP_PM_ADDR_ATTR_MAX, attr,
+					  mptcp_pm_addr_policy, info->extack);
+	if (err)
+		return err;
+
+	memset(entry, 0, sizeof(*entry));
+	if (!tb[MPTCP_PM_ADDR_ATTR_FAMILY]) {
+		if (!require_family)
+			goto skip_family;
+
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "missing family");
+		return -EINVAL;
+	}
+
+	entry->addr.family = nla_get_u16(tb[MPTCP_PM_ADDR_ATTR_FAMILY]);
+	if (entry->addr.family != AF_INET
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	    && entry->addr.family != AF_INET6
+#endif
+	    ) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "unknown address family");
+		return -EINVAL;
+	}
+	addr_addr = mptcp_pm_family_to_addr(entry->addr.family);
+	if (!tb[addr_addr]) {
+		NL_SET_ERR_MSG_ATTR(info->extack, attr,
+				    "missing address data");
+		return -EINVAL;
+	}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	if (entry->addr.family == AF_INET6)
+		entry->addr.addr6 = nla_get_in6_addr(tb[addr_addr]);
+	else
+#endif
+		entry->addr.addr.s_addr = nla_get_in_addr(tb[addr_addr]);
+
+skip_family:
+	if (tb[MPTCP_PM_ADDR_ATTR_IF_IDX])
+		entry->ifindex = nla_get_s32(tb[MPTCP_PM_ADDR_ATTR_IF_IDX]);
+
+	if (tb[MPTCP_PM_ADDR_ATTR_ID])
+		entry->addr.id = nla_get_u8(tb[MPTCP_PM_ADDR_ATTR_ID]);
+
+	if (tb[MPTCP_PM_ADDR_ATTR_FLAGS])
+		entry->flags = nla_get_u32(tb[MPTCP_PM_ADDR_ATTR_FLAGS]);
+
+	return 0;
+}
+
+static struct pm_nl_pernet *genl_info_pm_nl(struct genl_info *info)
+{
+	return net_generic(genl_info_net(info), pm_nl_pernet_id);
+}
+
+static int mptcp_nl_cmd_add_addr(struct sk_buff *skb, struct genl_info *info)
+{
+	struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	struct mptcp_pm_addr_entry addr, *entry;
+	int ret;
+
+	ret = mptcp_pm_parse_addr(attr, info, true, &addr);
+	if (ret < 0)
+		return ret;
+
+	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+	if (!entry) {
+		GENL_SET_ERR_MSG(info, "can't allocate addr");
+		return -ENOMEM;
+	}
+
+	*entry = addr;
+	ret = mptcp_pm_nl_append_new_local_addr(pernet, entry);
+	if (ret < 0) {
+		GENL_SET_ERR_MSG(info, "too many addresses or duplicate one");
+		kfree(entry);
+		return ret;
+	}
+
+	return 0;
+}
+
+static struct mptcp_pm_addr_entry *
+__lookup_addr_by_id(struct pm_nl_pernet *pernet, unsigned int id)
+{
+	struct mptcp_pm_addr_entry *entry;
+
+	list_for_each_entry(entry, &pernet->local_addr_list, list) {
+		if (entry->addr.id == id)
+			return entry;
+	}
+	return NULL;
+}
+
+static int mptcp_nl_cmd_del_addr(struct sk_buff *skb, struct genl_info *info)
+{
+	struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	struct mptcp_pm_addr_entry addr, *entry;
+	int ret;
+
+	ret = mptcp_pm_parse_addr(attr, info, false, &addr);
+	if (ret < 0)
+		return ret;
+
+	spin_lock_bh(&pernet->lock);
+	entry = __lookup_addr_by_id(pernet, addr.addr.id);
+	if (!entry) {
+		GENL_SET_ERR_MSG(info, "address not found");
+		ret = -EINVAL;
+		goto out;
+	}
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL)
+		pernet->add_addr_signal_max--;
+	if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW)
+		pernet->local_addr_max--;
+
+	pernet->addrs--;
+	list_del_rcu(&entry->list);
+	kfree_rcu(entry, rcu);
+out:
+	spin_unlock_bh(&pernet->lock);
+	return ret;
+}
+
+static void __flush_addrs(struct pm_nl_pernet *pernet)
+{
+	while (!list_empty(&pernet->local_addr_list)) {
+		struct mptcp_pm_addr_entry *cur;
+
+		cur = list_entry(pernet->local_addr_list.next,
+				 struct mptcp_pm_addr_entry, list);
+		list_del_rcu(&cur->list);
+		kfree_rcu(cur, rcu);
+	}
+}
+
+static void __reset_counters(struct pm_nl_pernet *pernet)
+{
+	pernet->add_addr_signal_max = 0;
+	pernet->add_addr_accept_max = 0;
+	pernet->local_addr_max = 0;
+	pernet->addrs = 0;
+}
+
+static int mptcp_nl_cmd_flush_addrs(struct sk_buff *skb, struct genl_info *info)
+{
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+
+	spin_lock_bh(&pernet->lock);
+	__flush_addrs(pernet);
+	__reset_counters(pernet);
+	spin_unlock_bh(&pernet->lock);
+	return 0;
+}
+
+static int mptcp_nl_fill_addr(struct sk_buff *skb,
+			      struct mptcp_pm_addr_entry *entry)
+{
+	struct mptcp_addr_info *addr = &entry->addr;
+	struct nlattr *attr;
+
+	attr = nla_nest_start(skb, MPTCP_PM_ATTR_ADDR);
+	if (!attr)
+		return -EMSGSIZE;
+
+	if (nla_put_u16(skb, MPTCP_PM_ADDR_ATTR_FAMILY, addr->family))
+		goto nla_put_failure;
+	if (nla_put_u8(skb, MPTCP_PM_ADDR_ATTR_ID, addr->id))
+		goto nla_put_failure;
+	if (nla_put_u32(skb, MPTCP_PM_ADDR_ATTR_FLAGS, entry->flags))
+		goto nla_put_failure;
+	if (entry->ifindex &&
+	    nla_put_s32(skb, MPTCP_PM_ADDR_ATTR_IF_IDX, entry->ifindex))
+		goto nla_put_failure;
+
+	if (addr->family == AF_INET)
+		nla_put_in_addr(skb, MPTCP_PM_ADDR_ATTR_ADDR4,
+				addr->addr.s_addr);
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+	else if (addr->family == AF_INET6)
+		nla_put_in6_addr(skb, MPTCP_PM_ADDR_ATTR_ADDR6, &addr->addr6);
+#endif
+	nla_nest_end(skb, attr);
+	return 0;
+
+nla_put_failure:
+	nla_nest_cancel(skb, attr);
+	return -EMSGSIZE;
+}
+
+static int mptcp_nl_cmd_get_addr(struct sk_buff *skb, struct genl_info *info)
+{
+	struct nlattr *attr = info->attrs[MPTCP_PM_ATTR_ADDR];
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	struct mptcp_pm_addr_entry addr, *entry;
+	struct sk_buff *msg;
+	void *reply;
+	int ret;
+
+	ret = mptcp_pm_parse_addr(attr, info, false, &addr);
+	if (ret < 0)
+		return ret;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	reply = genlmsg_put_reply(msg, info, &mptcp_genl_family, 0,
+				  info->genlhdr->cmd);
+	if (!reply) {
+		GENL_SET_ERR_MSG(info, "not enough space in Netlink message");
+		ret = -EMSGSIZE;
+		goto fail;
+	}
+
+	spin_lock_bh(&pernet->lock);
+	entry = __lookup_addr_by_id(pernet, addr.addr.id);
+	if (!entry) {
+		GENL_SET_ERR_MSG(info, "address not found");
+		ret = -EINVAL;
+		goto unlock_fail;
+	}
+
+	ret = mptcp_nl_fill_addr(msg, entry);
+	if (ret)
+		goto unlock_fail;
+
+	genlmsg_end(msg, reply);
+	ret = genlmsg_reply(msg, info);
+	spin_unlock_bh(&pernet->lock);
+	return ret;
+
+unlock_fail:
+	spin_unlock_bh(&pernet->lock);
+
+fail:
+	nlmsg_free(msg);
+	return ret;
+}
+
+static int mptcp_nl_cmd_dump_addrs(struct sk_buff *msg,
+				   struct netlink_callback *cb)
+{
+	struct net *net = sock_net(msg->sk);
+	struct mptcp_pm_addr_entry *entry;
+	struct pm_nl_pernet *pernet;
+	int id = cb->args[0];
+	void *hdr;
+
+	pernet = net_generic(net, pm_nl_pernet_id);
+
+	spin_lock_bh(&pernet->lock);
+	list_for_each_entry(entry, &pernet->local_addr_list, list) {
+		if (entry->addr.id <= id)
+			continue;
+
+		hdr = genlmsg_put(msg, NETLINK_CB(cb->skb).portid,
+				  cb->nlh->nlmsg_seq, &mptcp_genl_family,
+				  NLM_F_MULTI, MPTCP_PM_CMD_GET_ADDR);
+		if (!hdr)
+			break;
+
+		if (mptcp_nl_fill_addr(msg, entry) < 0) {
+			genlmsg_cancel(msg, hdr);
+			break;
+		}
+
+		id = entry->addr.id;
+		genlmsg_end(msg, hdr);
+	}
+	spin_unlock_bh(&pernet->lock);
+
+	cb->args[0] = id;
+	return msg->len;
+}
+
+static int parse_limit(struct genl_info *info, int id, unsigned int *limit)
+{
+	struct nlattr *attr = info->attrs[id];
+
+	if (!attr)
+		return 0;
+
+	*limit = nla_get_u32(attr);
+	if (*limit > MPTCP_PM_ADDR_MAX) {
+		GENL_SET_ERR_MSG(info, "limit greater than maximum");
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int
+mptcp_nl_cmd_set_limits(struct sk_buff *skb, struct genl_info *info)
+{
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	unsigned int rcv_addrs, subflows;
+	int ret;
+
+	spin_lock_bh(&pernet->lock);
+	rcv_addrs = pernet->add_addr_accept_max;
+	ret = parse_limit(info, MPTCP_PM_ATTR_RCV_ADD_ADDRS, &rcv_addrs);
+	if (ret)
+		goto unlock;
+
+	subflows = pernet->subflows_max;
+	ret = parse_limit(info, MPTCP_PM_ATTR_SUBFLOWS, &subflows);
+	if (ret)
+		goto unlock;
+
+	WRITE_ONCE(pernet->add_addr_accept_max, rcv_addrs);
+	WRITE_ONCE(pernet->subflows_max, subflows);
+
+unlock:
+	spin_unlock_bh(&pernet->lock);
+	return ret;
+}
+
+static int
+mptcp_nl_cmd_get_limits(struct sk_buff *skb, struct genl_info *info)
+{
+	struct pm_nl_pernet *pernet = genl_info_pm_nl(info);
+	struct sk_buff *msg;
+	void *reply;
+
+	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	reply = genlmsg_put_reply(msg, info, &mptcp_genl_family, 0,
+				  MPTCP_PM_CMD_GET_LIMITS);
+	if (!reply)
+		goto fail;
+
+	if (nla_put_u32(msg, MPTCP_PM_ATTR_RCV_ADD_ADDRS,
+			READ_ONCE(pernet->add_addr_accept_max)))
+		goto fail;
+
+	if (nla_put_u32(msg, MPTCP_PM_ATTR_SUBFLOWS,
+			READ_ONCE(pernet->subflows_max)))
+		goto fail;
+
+	genlmsg_end(msg, reply);
+	return genlmsg_reply(msg, info);
+
+fail:
+	GENL_SET_ERR_MSG(info, "not enough space in Netlink message");
+	nlmsg_free(msg);
+	return -EMSGSIZE;
+}
+
+static struct genl_ops mptcp_pm_ops[] = {
+	{
+		.cmd    = MPTCP_PM_CMD_ADD_ADDR,
+		.doit   = mptcp_nl_cmd_add_addr,
+		.flags  = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd    = MPTCP_PM_CMD_DEL_ADDR,
+		.doit   = mptcp_nl_cmd_del_addr,
+		.flags  = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd    = MPTCP_PM_CMD_FLUSH_ADDRS,
+		.doit   = mptcp_nl_cmd_flush_addrs,
+		.flags  = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd    = MPTCP_PM_CMD_GET_ADDR,
+		.doit   = mptcp_nl_cmd_get_addr,
+		.dumpit   = mptcp_nl_cmd_dump_addrs,
+	},
+	{
+		.cmd    = MPTCP_PM_CMD_SET_LIMITS,
+		.doit   = mptcp_nl_cmd_set_limits,
+		.flags  = GENL_ADMIN_PERM,
+	},
+	{
+		.cmd    = MPTCP_PM_CMD_GET_LIMITS,
+		.doit   = mptcp_nl_cmd_get_limits,
+	},
+};
+
+static struct genl_family mptcp_genl_family __ro_after_init = {
+	.name		= MPTCP_PM_NAME,
+	.version	= MPTCP_PM_VER,
+	.maxattr	= MPTCP_PM_ATTR_MAX,
+	.policy		= mptcp_pm_policy,
+	.netnsok	= true,
+	.module		= THIS_MODULE,
+	.ops		= mptcp_pm_ops,
+	.n_ops		= ARRAY_SIZE(mptcp_pm_ops),
+	.mcgrps		= mptcp_pm_mcgrps,
+	.n_mcgrps	= ARRAY_SIZE(mptcp_pm_mcgrps),
+};
+
+static int __net_init pm_nl_init_net(struct net *net)
+{
+	struct pm_nl_pernet *pernet = net_generic(net, pm_nl_pernet_id);
+
+	INIT_LIST_HEAD_RCU(&pernet->local_addr_list);
+	__reset_counters(pernet);
+	pernet->next_id = 1;
+	spin_lock_init(&pernet->lock);
+	return 0;
+}
+
+static void __net_exit pm_nl_exit_net(struct list_head *net_list)
+{
+	struct net *net;
+
+	list_for_each_entry(net, net_list, exit_list) {
+		/* net is removed from namespace list, can't race with
+		 * other modifiers
+		 */
+		__flush_addrs(net_generic(net, pm_nl_pernet_id));
+	}
+}
+
+static struct pernet_operations mptcp_pm_pernet_ops = {
+	.init = pm_nl_init_net,
+	.exit_batch = pm_nl_exit_net,
+	.id = &pm_nl_pernet_id,
+	.size = sizeof(struct pm_nl_pernet),
+};
+
+void mptcp_pm_nl_init(void)
+{
+	if (register_pernet_subsys(&mptcp_pm_pernet_ops) < 0)
+		panic("Failed to register MPTCP PM pernet subsystem.\n");
+
+	if (genl_register_family(&mptcp_genl_family))
+		panic("Failed to register MPTCP PM netlink family\n");
+}
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 0999f74df027..f733c5425552 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -396,6 +396,13 @@ bool mptcp_pm_addr_signal(struct mptcp_sock *msk, unsigned int remaining,
 			  struct mptcp_addr_info *saddr);
 int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
 
+void mptcp_pm_nl_init(void);
+void mptcp_pm_nl_data_init(struct mptcp_sock *msk);
+void mptcp_pm_nl_fully_established(struct mptcp_sock *msk);
+void mptcp_pm_nl_subflow_established(struct mptcp_sock *msk);
+void mptcp_pm_nl_add_addr_received(struct mptcp_sock *msk);
+int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);
+
 static inline struct mptcp_ext *mptcp_get_ext(struct sk_buff *skb)
 {
 	return (struct mptcp_ext *)skb_ext_find(skb, SKB_EXT_MPTCP);