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41 results

pm_netlink.c

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  • Forked from hardware-enablement / Rockchip upstream enablement efforts / linux
    Source project has a limited visibility.
    pm_netlink.c 21.21 KiB
    // 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");
    }