text: // SPDX-License-Identifier: GPL-2.0
  /* Multipath TCP
   *
   * Copyright (c) 2020, Red Hat, Inc.
   */
  
  #define pr_fmt(fmt) "MPTCP: " fmt
  
  #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))
  		goto nla_put_failure;
  #if IS_ENABLED(CONFIG_MPTCP_IPV6)
  	else if (addr->family == AF_INET6 &&
  		 nla_put_in6_addr(skb, MPTCP_PM_ADDR_ATTR_ADDR6, &addr->addr6))
  		goto nla_put_failure;
  #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");
  }
  