// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * NETLINK      Kernel-user communication protocol.
 *
 *              Authors:        Alan Cox <alan@lxorguk.ukuu.org.uk>
 *                              Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
 *                              Patrick McHardy <kaber@trash.net>
 *
 * Tue Jun 26 14:36:48 MEST 2001 Herbert "herp" Rosmanith
 *                               added netlink_proto_exit
 * Tue Jan 22 18:32:44 BRST 2002 Arnaldo C. de Melo <acme@conectiva.com.br>
 *                               use nlk_sk, as sk->protinfo is on a diet 8)
 * Fri Jul 22 19:51:12 MEST 2005 Harald Welte <laforge@gnumonks.org>
 *                               - inc module use count of module that owns
 *                                 the kernel socket in case userspace opens
 *                                 socket of same protocol
 *                               - remove all module support, since netlink is
 *                                 mandatory if CONFIG_NET=y these days
 */

#include <linux/module.h>

#include <linux/capability.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/stat.h>
#include <linux/socket.h>
#include <linux/un.h>
#include <linux/fcntl.h>
#include <linux/termios.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/rtnetlink.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/notifier.h>
#include <linux/security.h>
#include <linux/jhash.h>
#include <linux/jiffies.h>
#include <linux/random.h>
#include <linux/bitops.h>
#include <linux/mm.h>
#include <linux/types.h>
#include <linux/audit.h>
#include <linux/mutex.h>
#include <linux/vmalloc.h>
#include <linux/if_arp.h>
#include <linux/rhashtable.h>
#include <asm/cacheflush.h>
#include <linux/hash.h>
#include <linux/genetlink.h>
#include <linux/net_namespace.h>
#include <linux/nospec.h>

#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/sock.h>
#include <net/scm.h>
#include <net/netlink.h>

#include "af_netlink.h"

struct listeners {
        struct rcu_head         rcu;
        unsigned long           masks[0];
};

/* state bits */
#define NETLINK_S_CONGESTED             0x0

static inline int netlink_is_kernel(struct sock *sk)
{
        return nlk_sk(sk)->flags & NETLINK_F_KERNEL_SOCKET;
}

struct netlink_table *nl_table __read_mostly;
EXPORT_SYMBOL_GPL(nl_table);

static DECLARE_WAIT_QUEUE_HEAD(nl_table_wait);

static struct lock_class_key nlk_cb_mutex_keys[MAX_LINKS];

static const char *const nlk_cb_mutex_key_strings[MAX_LINKS + 1] = {
        "nlk_cb_mutex-ROUTE",
        "nlk_cb_mutex-1",
        "nlk_cb_mutex-USERSOCK",
        "nlk_cb_mutex-FIREWALL",
        "nlk_cb_mutex-SOCK_DIAG",
        "nlk_cb_mutex-NFLOG",
        "nlk_cb_mutex-XFRM",
        "nlk_cb_mutex-SELINUX",
        "nlk_cb_mutex-ISCSI",
        "nlk_cb_mutex-AUDIT",
        "nlk_cb_mutex-FIB_LOOKUP",
        "nlk_cb_mutex-CONNECTOR",
        "nlk_cb_mutex-NETFILTER",
        "nlk_cb_mutex-IP6_FW",
        "nlk_cb_mutex-DNRTMSG",
        "nlk_cb_mutex-KOBJECT_UEVENT",
        "nlk_cb_mutex-GENERIC",
        "nlk_cb_mutex-17",
        "nlk_cb_mutex-SCSITRANSPORT",
        "nlk_cb_mutex-ECRYPTFS",
        "nlk_cb_mutex-RDMA",
        "nlk_cb_mutex-CRYPTO",
        "nlk_cb_mutex-SMC",
        "nlk_cb_mutex-23",
        "nlk_cb_mutex-24",
        "nlk_cb_mutex-25",
        "nlk_cb_mutex-26",
        "nlk_cb_mutex-27",
        "nlk_cb_mutex-28",
        "nlk_cb_mutex-29",
        "nlk_cb_mutex-30",
        "nlk_cb_mutex-31",
        "nlk_cb_mutex-MAX_LINKS"
};

static int netlink_dump(struct sock *sk);

/* nl_table locking explained:
 * Lookup and traversal are protected with an RCU read-side lock. Insertion
 * and removal are protected with per bucket lock while using RCU list
 * modification primitives and may run in parallel to RCU protected lookups.
 * Destruction of the Netlink socket may only occur *after* nl_table_lock has
 * been acquired * either during or after the socket has been removed from
 * the list and after an RCU grace period.
 */
DEFINE_RWLOCK(nl_table_lock);
EXPORT_SYMBOL_GPL(nl_table_lock);
static atomic_t nl_table_users = ATOMIC_INIT(0);

#define nl_deref_protected(X) rcu_dereference_protected(X, lockdep_is_held(&nl_table_lock));

static BLOCKING_NOTIFIER_HEAD(netlink_chain);


static const struct rhashtable_params netlink_rhashtable_params;

static inline u32 netlink_group_mask(u32 group)
{
        return group ? 1 << (group - 1) : 0;
}

static struct sk_buff *netlink_to_full_skb(const struct sk_buff *skb,
                                           gfp_t gfp_mask)
{
        unsigned int len = skb_end_offset(skb);
        struct sk_buff *new;

        new = alloc_skb(len, gfp_mask);
        if (new == NULL)
                return NULL;

        NETLINK_CB(new).portid = NETLINK_CB(skb).portid;
        NETLINK_CB(new).dst_group = NETLINK_CB(skb).dst_group;
        NETLINK_CB(new).creds = NETLINK_CB(skb).creds;

        skb_put_data(new, skb->data, len);
        return new;
}

static unsigned int netlink_tap_net_id;

struct netlink_tap_net {
        struct list_head netlink_tap_all;
        struct mutex netlink_tap_lock;
};

int netlink_add_tap(struct netlink_tap *nt)
{
        struct net *net = dev_net(nt->dev);
        struct netlink_tap_net *nn = net_generic(net, netlink_tap_net_id);

        if (unlikely(nt->dev->type != ARPHRD_NETLINK))
                return -EINVAL;

        mutex_lock(&nn->netlink_tap_lock);
        list_add_rcu(&nt->list, &nn->netlink_tap_all);
        mutex_unlock(&nn->netlink_tap_lock);

        __module_get(nt->module);

        return 0;
}
EXPORT_SYMBOL_GPL(netlink_add_tap);

static int __netlink_remove_tap(struct netlink_tap *nt)
{
        struct net *net = dev_net(nt->dev);
        struct netlink_tap_net *nn = net_generic(net, netlink_tap_net_id);
        bool found = false;
        struct netlink_tap *tmp;

        mutex_lock(&nn->netlink_tap_lock);

        list_for_each_entry(tmp, &nn->netlink_tap_all, list) {
                if (nt == tmp) {
                        list_del_rcu(&nt->list);
                        found = true;
                        goto out;
                }
        }

        pr_warn("__netlink_remove_tap: %p not found\n", nt);
out:
        mutex_unlock(&nn->netlink_tap_lock);

        if (found)
                module_put(nt->module);

        return found ? 0 : -ENODEV;
}

int netlink_remove_tap(struct netlink_tap *nt)
{
        int ret;

        ret = __netlink_remove_tap(nt);
        synchronize_net();

        return ret;
}
EXPORT_SYMBOL_GPL(netlink_remove_tap);

static __net_init int netlink_tap_init_net(struct net *net)
{
        struct netlink_tap_net *nn = net_generic(net, netlink_tap_net_id);

        INIT_LIST_HEAD(&nn->netlink_tap_all);
        mutex_init(&nn->netlink_tap_lock);
        return 0;
}

static struct pernet_operations netlink_tap_net_ops = {
        .init = netlink_tap_init_net,
        .id   = &netlink_tap_net_id,
        .size = sizeof(struct netlink_tap_net),
};

static bool netlink_filter_tap(const struct sk_buff *skb)
{
        struct sock *sk = skb->sk;

        /* We take the more conservative approach and
         * whitelist socket protocols that may pass.
         */
        switch (sk->sk_protocol) {
        case NETLINK_ROUTE:
        case NETLINK_USERSOCK:
        case NETLINK_SOCK_DIAG:
        case NETLINK_NFLOG:
        case NETLINK_XFRM:
        case NETLINK_FIB_LOOKUP:
        case NETLINK_NETFILTER:
        case NETLINK_GENERIC:
                return true;
        }

        return false;
}

static int __netlink_deliver_tap_skb(struct sk_buff *skb,
                                     struct net_device *dev)
{
        struct sk_buff *nskb;
        struct sock *sk = skb->sk;
        int ret = -ENOMEM;

        if (!net_eq(dev_net(dev), sock_net(sk)))
                return 0;

        dev_hold(dev);

        if (is_vmalloc_addr(skb->head))
                nskb = netlink_to_full_skb(skb, GFP_ATOMIC);
        else
                nskb = skb_clone(skb, GFP_ATOMIC);
        if (nskb) {
                nskb->dev = dev;
                nskb->protocol = htons((u16) sk->sk_protocol);
                nskb->pkt_type = netlink_is_kernel(sk) ?
                                 PACKET_KERNEL : PACKET_USER;
                skb_reset_network_header(nskb);
                ret = dev_queue_xmit(nskb);
                if (unlikely(ret > 0))
                        ret = net_xmit_errno(ret);
        }

        dev_put(dev);
        return ret;
}

static void __netlink_deliver_tap(struct sk_buff *skb, struct netlink_tap_net *nn)
{
        int ret;
        struct netlink_tap *tmp;

        if (!netlink_filter_tap(skb))
                return;

        list_for_each_entry_rcu(tmp, &nn->netlink_tap_all, list) {
                ret = __netlink_deliver_tap_skb(skb, tmp->dev);
                if (unlikely(ret))
                        break;
        }
}

static void netlink_deliver_tap(struct net *net, struct sk_buff *skb)
{
        struct netlink_tap_net *nn = net_generic(net, netlink_tap_net_id);

        rcu_read_lock();

        if (unlikely(!list_empty(&nn->netlink_tap_all)))
                __netlink_deliver_tap(skb, nn);

        rcu_read_unlock();
}

static void netlink_deliver_tap_kernel(struct sock *dst, struct sock *src,
                                       struct sk_buff *skb)
{
        if (!(netlink_is_kernel(dst) && netlink_is_kernel(src)))
                netlink_deliver_tap(sock_net(dst), skb);
}

static void netlink_overrun(struct sock *sk)
{
        struct netlink_sock *nlk = nlk_sk(sk);

        if (!(nlk->flags & NETLINK_F_RECV_NO_ENOBUFS)) {
                if (!test_and_set_bit(NETLINK_S_CONGESTED,
                                      &nlk_sk(sk)->state)) {
                        sk->sk_err = ENOBUFS;
                        sk->sk_error_report(sk);
                }
        }
        atomic_inc(&sk->sk_drops);
}

static void netlink_rcv_wake(struct sock *sk)
{
        struct netlink_sock *nlk = nlk_sk(sk);

        if (skb_queue_empty(&sk->sk_receive_queue))
                clear_bit(NETLINK_S_CONGESTED, &nlk->state);
        if (!test_bit(NETLINK_S_CONGESTED, &nlk->state))
                wake_up_interruptible(&nlk->wait);
}

static void netlink_skb_destructor(struct sk_buff *skb)
{
        if (is_vmalloc_addr(skb->head)) {
                if (!skb->cloned ||
                    !atomic_dec_return(&(skb_shinfo(skb)->dataref)))
                        vfree(skb->head);

                skb->head = NULL;
        }
        if (skb->sk != NULL)
                sock_rfree(skb);
}

static void netlink_skb_set_owner_r(struct sk_buff *skb, struct sock *sk)
{
        WARN_ON(skb->sk != NULL);
        skb->sk = sk;
        skb->destructor = netlink_skb_destructor;
        atomic_add(skb->truesize, &sk->sk_rmem_alloc);
        sk_mem_charge(sk, skb->truesize);
}

static void netlink_sock_destruct(struct sock *sk)
{
        struct netlink_sock *nlk = nlk_sk(sk);

        if (nlk->cb_running) {
                if (nlk->cb.done)
                        nlk->cb.done(&nlk->cb);
                module_put(nlk->cb.module);
                kfree_skb(nlk->cb.skb);
        }

        skb_queue_purge(&sk->sk_receive_queue);

        if (!sock_flag(sk, SOCK_DEAD)) {
                printk(KERN_ERR "Freeing alive netlink socket %p\n", sk);
                return;
        }

        WARN_ON(atomic_read(&sk->sk_rmem_alloc));
        WARN_ON(refcount_read(&sk->sk_wmem_alloc));
        WARN_ON(nlk_sk(sk)->groups);
}

static void netlink_sock_destruct_work(struct work_struct *work)
{
        struct netlink_sock *nlk = container_of(work, struct netlink_sock,
                                                work);

        sk_free(&nlk->sk);
}

/* This lock without WQ_FLAG_EXCLUSIVE is good on UP and it is _very_ bad on
 * SMP. Look, when several writers sleep and reader wakes them up, all but one
 * immediately hit write lock and grab all the cpus. Exclusive sleep solves
 * this, _but_ remember, it adds useless work on UP machines.
 */

void netlink_table_grab(void)
        __acquires(nl_table_lock)
{
        might_sleep();

        write_lock_irq(&nl_table_lock);

        if (atomic_read(&nl_table_users)) {
                DECLARE_WAITQUEUE(wait, current);

                add_wait_queue_exclusive(&nl_table_wait, &wait);
                for (;;) {
                        set_current_state(TASK_UNINTERRUPTIBLE);
                        if (atomic_read(&nl_table_users) == 0)
                                break;
                        write_unlock_irq(&nl_table_lock);
                        schedule();
                        write_lock_irq(&nl_table_lock);
                }

                __set_current_state(TASK_RUNNING);
                remove_wait_queue(&nl_table_wait, &wait);
        }
}

void netlink_table_ungrab(void)
        __releases(nl_table_lock)
{
        write_unlock_irq(&nl_table_lock);
        wake_up(&nl_table_wait);
}

static inline void
netlink_lock_table(void)
{
        /* read_lock() synchronizes us to netlink_table_grab */

        read_lock(&nl_table_lock);
        atomic_inc(&nl_table_users);
        read_unlock(&nl_table_lock);
}

static inline void
netlink_unlock_table(void)
{
        if (atomic_dec_and_test(&nl_table_users))
                wake_up(&nl_table_wait);
}

struct netlink_compare_arg
{
        possible_net_t pnet;
        u32 portid;
};

/* Doing sizeof directly may yield 4 extra bytes on 64-bit. */
#define netlink_compare_arg_len \
        (offsetof(struct netlink_compare_arg, portid) + sizeof(u32))

static inline int netlink_compare(struct rhashtable_compare_arg *arg,
                                  const void *ptr)
{
        const struct netlink_compare_arg *x = arg->key;
        const struct netlink_sock *nlk = ptr;

        return nlk->portid != x->portid ||
               !net_eq(sock_net(&nlk->sk), read_pnet(&x->pnet));
}

static void netlink_compare_arg_init(struct netlink_compare_arg *arg,
                                     struct net *net, u32 portid)
{
        memset(arg, 0, sizeof(*arg));
        write_pnet(&arg->pnet, net);
        arg->portid = portid;
}

static struct sock *__netlink_lookup(struct netlink_table *table, u32 portid,
                                     struct net *net)
{
        struct netlink_compare_arg arg;

        netlink_compare_arg_init(&arg, net, portid);
        return rhashtable_lookup_fast(&table->hash, &arg,
                                      netlink_rhashtable_params);
}

static int __netlink_insert(struct netlink_table *table, struct sock *sk)
{
        struct netlink_compare_arg arg;

        netlink_compare_arg_init(&arg, sock_net(sk), nlk_sk(sk)->portid);
        return rhashtable_lookup_insert_key(&table->hash, &arg,
                                            &nlk_sk(sk)->node,
                                            netlink_rhashtable_params);
}

static struct sock *netlink_lookup(struct net *net, int protocol, u32 portid)
{
        struct netlink_table *table = &nl_table[protocol];
        struct sock *sk;

        rcu_read_lock();
        sk = __netlink_lookup(table, portid, net);
        if (sk)
                sock_hold(sk);
        rcu_read_unlock();

        return sk;
}

static const struct proto_ops netlink_ops;

static void
netlink_update_listeners(struct sock *sk)
{
        struct netlink_table *tbl = &nl_table[sk->sk_protocol];
        unsigned long mask;
        unsigned int i;
        struct listeners *listeners;

        listeners = nl_deref_protected(tbl->listeners);
        if (!listeners)
                return;

        for (i = 0; i < NLGRPLONGS(tbl->groups); i++) {
                mask = 0;
                sk_for_each_bound(sk, &tbl->mc_list) {
                        if (i < NLGRPLONGS(nlk_sk(sk)->ngroups))
                                mask |= nlk_sk(sk)->groups[i];
                }
                listeners->masks[i] = mask;
        }
        /* this function is only called with the netlink table "grabbed", which
         * makes sure updates are visible before bind or setsockopt return. */
}

static int netlink_insert(struct sock *sk, u32 portid)
{
        struct netlink_table *table = &nl_table[sk->sk_protocol];
        int err;

        lock_sock(sk);

        err = nlk_sk(sk)->portid == portid ? 0 : -EBUSY;
        if (nlk_sk(sk)->bound)
                goto err;

        nlk_sk(sk)->portid = portid;
        sock_hold(sk);

        err = __netlink_insert(table, sk);
        if (err) {
                /* In case the hashtable backend returns with -EBUSY
                 * from here, it must not escape to the caller.
                 */
                if (unlikely(err == -EBUSY))
                        err = -EOVERFLOW;
                if (err == -EEXIST)
                        err = -EADDRINUSE;
                sock_put(sk);
                goto err;
        }

        /* We need to ensure that the socket is hashed and visible. */
        smp_wmb();
        nlk_sk(sk)->bound = portid;

err:
        release_sock(sk);
        return err;
}

static void netlink_remove(struct sock *sk)
{
        struct netlink_table *table;

        table = &nl_table[sk->sk_protocol];
        if (!rhashtable_remove_fast(&table->hash, &nlk_sk(sk)->node,
                                    netlink_rhashtable_params)) {
                WARN_ON(refcount_read(&sk->sk_refcnt) == 1);
                __sock_put(sk);
        }

        netlink_table_grab();
        if (nlk_sk(sk)->subscriptions) {
                __sk_del_bind_node(sk);
                netlink_update_listeners(sk);
        }
        if (sk->sk_protocol == NETLINK_GENERIC)
                atomic_inc(&genl_sk_destructing_cnt);
        netlink_table_ungrab();
}

static struct proto netlink_proto = {
        .name     = "NETLINK",
        .owner    = THIS_MODULE,
        .obj_size = sizeof(struct netlink_sock),
};

static int __netlink_create(struct net *net, struct socket *sock,
                            struct mutex *cb_mutex, int protocol,
                            int kern)
{
        struct sock *sk;
        struct netlink_sock *nlk;

        sock->ops = &netlink_ops;

        sk = sk_alloc(net, PF_NETLINK, GFP_KERNEL, &netlink_proto, kern);
        if (!sk)
                return -ENOMEM;

        sock_init_data(sock, sk);

        nlk = nlk_sk(sk);
        if (cb_mutex) {
                nlk->cb_mutex = cb_mutex;
        } else {
                nlk->cb_mutex = &nlk->cb_def_mutex;
                mutex_init(nlk->cb_mutex);
                lockdep_set_class_and_name(nlk->cb_mutex,
                                           nlk_cb_mutex_keys + protocol,
                                           nlk_cb_mutex_key_strings[protocol]);
        }
        init_waitqueue_head(&nlk->wait);

        sk->sk_destruct = netlink_sock_destruct;
        sk->sk_protocol = protocol;
        return 0;
}

static int netlink_create(struct net *net, struct socket *sock, int protocol,
                          int kern)
{
        struct module *module = NULL;
        struct mutex *cb_mutex;
        struct netlink_sock *nlk;
        int (*bind)(struct net *net, int group);
        void (*unbind)(struct net *net, int group);
        int err = 0;

        sock->state = SS_UNCONNECTED;

        if (sock->type != SOCK_RAW && sock->type != SOCK_DGRAM)
                return -ESOCKTNOSUPPORT;

        if (protocol < 0 || protocol >= MAX_LINKS)
                return -EPROTONOSUPPORT;
        protocol = array_index_nospec(protocol, MAX_LINKS);

        netlink_lock_table();
#ifdef CONFIG_MODULES
        if (!nl_table[protocol].registered) {
                netlink_unlock_table();
                request_module("net-pf-%d-proto-%d", PF_NETLINK, protocol);
                netlink_lock_table();
        }
#endif
        if (nl_table[protocol].registered &&
            try_module_get(nl_table[protocol].module))
                module = nl_table[protocol].module;
        else
                err = -EPROTONOSUPPORT;
        cb_mutex = nl_table[protocol].cb_mutex;
        bind = nl_table[protocol].bind;
        unbind = nl_table[protocol].unbind;
        netlink_unlock_table();

        if (err < 0)
                goto out;

        err = __netlink_create(net, sock, cb_mutex, protocol, kern);
        if (err < 0)
                goto out_module;

        local_bh_disable();
        sock_prot_inuse_add(net, &netlink_proto, 1);
        local_bh_enable();

        nlk = nlk_sk(sock->sk);
        nlk->module = module;
        nlk->netlink_bind = bind;
        nlk->netlink_unbind = unbind;
out:
        return err;

out_module:
        module_put(module);
        goto out;
}

static void deferred_put_nlk_sk(struct rcu_head *head)
{
        struct netlink_sock *nlk = container_of(head, struct netlink_sock, rcu);
        struct sock *sk = &nlk->sk;

        kfree(nlk->groups);
        nlk->groups = NULL;

        if (!refcount_dec_and_test(&sk->sk_refcnt))
                return;

        if (nlk->cb_running && nlk->cb.done) {
                INIT_WORK(&nlk->work, netlink_sock_destruct_work);
                schedule_work(&nlk->work);
                return;
        }

        sk_free(sk);
}

static int netlink_release(struct socket *sock)
{
        struct sock *sk = sock->sk;
        struct netlink_sock *nlk;

        if (!sk)
                return 0;

        netlink_remove(sk);
        sock_orphan(sk);
        nlk = nlk_sk(sk);

        /*
         * OK. Socket is unlinked, any packets that arrive now
         * will be purged.
         */

        /* must not acquire netlink_table_lock in any way again before unbind
         * and notifying genetlink is done as otherwise it might deadlock
         */
        if (nlk->netlink_unbind) {
                int i;

                for (i = 0; i < nlk->ngroups; i++)
                        if (test_bit(i, nlk->groups))
                                nlk->netlink_unbind(sock_net(sk), i + 1);
        }
        if (sk->sk_protocol == NETLINK_GENERIC &&
            atomic_dec_return(&genl_sk_destructing_cnt) == 0)
                wake_up(&genl_sk_destructing_waitq);

        sock->sk = NULL;
        wake_up_interruptible_all(&nlk->wait);

        skb_queue_purge(&sk->sk_write_queue);

        if (nlk->portid && nlk->bound) {
                struct netlink_notify n = {
                                                .net = sock_net(sk),
                                                .protocol = sk->sk_protocol,
                                                .portid = nlk->portid,
                                          };
                blocking_notifier_call_chain(&netlink_chain,
                                NETLINK_URELEASE, &n);
        }

        module_put(nlk->module);

        if (netlink_is_kernel(sk)) {
                netlink_table_grab();
                BUG_ON(nl_table[sk->sk_protocol].registered == 0);
                if (--nl_table[sk->sk_protocol].registered == 0) {
                        struct listeners *old;

                        old = nl_deref_protected(nl_table[sk->sk_protocol].listeners);
                        RCU_INIT_POINTER(nl_table[sk->sk_protocol].listeners, NULL);
                        kfree_rcu(old, rcu);
                        nl_table[sk->sk_protocol].module = NULL;
                        nl_table[sk->sk_protocol].bind = NULL;
                        nl_table[sk->sk_protocol].unbind = NULL;
                        nl_table[sk->sk_protocol].flags = 0;
                        nl_table[sk->sk_protocol].registered = 0;
                }
                netlink_table_ungrab();
        }

        local_bh_disable();
        sock_prot_inuse_add(sock_net(sk), &netlink_proto, -1);
        local_bh_enable();
        call_rcu(&nlk->rcu, deferred_put_nlk_sk);
        return 0;
}

static int netlink_autobind(struct socket *sock)
{
        struct sock *sk = sock->sk;
        struct net *net = sock_net(sk);
        struct netlink_table *table = &nl_table[sk->sk_protocol];
        s32 portid = task_tgid_vnr(current);
        int err;
        s32 rover = -4096;
        bool ok;

retry:
        cond_resched();
        rcu_read_lock();
        ok = !__netlink_lookup(table, portid, net);
        rcu_read_unlock();
        if (!ok) {
                /* Bind collision, search negative portid values. */
                if (rover == -4096)
                        /* rover will be in range [S32_MIN, -4097] */
                        rover = S32_MIN + prandom_u32_max(-4096 - S32_MIN);
                else if (rover >= -4096)
                        rover = -4097;
                portid = rover--;
                goto retry;
        }

        err = netlink_insert(sk, portid);
        if (err == -EADDRINUSE)
                goto retry;

        /* If 2 threads race to autobind, that is fine.  */
        if (err == -EBUSY)
                err = 0;

        return err;
}

/**
 * __netlink_ns_capable - General netlink message capability test
 * @nsp: NETLINK_CB of the socket buffer holding a netlink command from userspace.
 * @user_ns: The user namespace of the capability to use
 * @cap: The capability to use
 *
 * Test to see if the opener of the socket we received the message
 * from had when the netlink socket was created and the sender of the
 * message has has the capability @cap in the user namespace @user_ns.
 */
bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
                        struct user_namespace *user_ns, int cap)
{
        return ((nsp->flags & NETLINK_SKB_DST) ||
                file_ns_capable(nsp->sk->sk_socket->file, user_ns, cap)) &&
                ns_capable(user_ns, cap);
}
EXPORT_SYMBOL(__netlink_ns_capable);

/**
 * netlink_ns_capable - General netlink message capability test
 * @skb: socket buffer holding a netlink command from userspace
 * @user_ns: The user namespace of the capability to use
 * @cap: The capability to use
 *
 * Test to see if the opener of the socket we received the message
 * from had when the netlink socket was created and the sender of the
 * message has has the capability @cap in the user namespace @user_ns.
 */
bool netlink_ns_capable(const struct sk_buff *skb,
                        struct user_namespace *user_ns, int cap)
{
        return __netlink_ns_capable(&NETLINK_CB(skb), user_ns, cap);
}
EXPORT_SYMBOL(netlink_ns_capable);

/**
 * netlink_capable - Netlink global message capability test
 * @skb: socket buffer holding a netlink command from userspace
 * @cap: The capability to use
 *
 * Test to see if the opener of the socket we received the message
 * from had when the netlink socket was created and the sender of the
 * message has has the capability @cap in all user namespaces.
 */
bool netlink_capable(const struct sk_buff *skb, int cap)
{
        return netlink_ns_capable(skb, &init_user_ns, cap);
}
EXPORT_SYMBOL(netlink_capable);

/**
 * netlink_net_capable - Netlink network namespace message capability test
 * @skb: socket buffer holding a netlink command from userspace
 * @cap: The capability to use
 *
 * Test to see if the opener of the socket we received the message
 * from had when the netlink socket was created and the sender of the
 * message has has the capability @cap over the network namespace of
 * the socket we received the message from.
 */
bool netlink_net_capable(const struct sk_buff *skb, int cap)
{
        return netlink_ns_capable(skb, sock_net(skb->sk)->user_ns, cap);
}
EXPORT_SYMBOL(netlink_net_capable);

static inline int netlink_allowed(const struct socket *sock, unsigned int flag)
{
        return (nl_table[sock->sk->sk_protocol].flags & flag) ||
                ns_capable(sock_net(sock->sk)->user_ns, CAP_NET_ADMIN);
}

static void
netlink_update_subscriptions(struct sock *sk, unsigned int subscriptions)
{
        struct netlink_sock *nlk = nlk_sk(sk);

        if (nlk->subscriptions && !subscriptions)
                __sk_del_bind_node(sk);
        else if (!nlk->subscriptions && subscriptions)
                sk_add_bind_node(sk, &nl_table[sk->sk_protocol].mc_list);
        nlk->subscriptions = subscriptions;
}

static int netlink_realloc_groups(struct sock *sk)
{
        struct netlink_sock *nlk = nlk_sk(sk);
        unsigned int groups;
        unsigned long *new_groups;
        int err = 0;

        netlink_table_grab();

        groups = nl_table[sk->sk_protocol].groups;
        if (!nl_table[sk->sk_protocol].registered) {
                err = -ENOENT;
                goto out_unlock;
        }

        if (nlk->ngroups >= groups)
                goto out_unlock;

        new_groups = krealloc(nlk->groups, NLGRPSZ(groups), GFP_ATOMIC);
        if (new_groups == NULL) {
                err = -ENOMEM;
                goto out_unlock;
        }
        memset((char *)new_groups + NLGRPSZ(nlk->ngroups), 0,
               NLGRPSZ(groups) - NLGRPSZ(nlk->ngroups));

        nlk->groups = new_groups;
        nlk->ngroups = groups;
 out_unlock:
        netlink_table_ungrab();
        return err;
}

static void netlink_undo_bind(int group, long unsigned int groups,
                              struct sock *sk)
{
        struct netlink_sock *nlk = nlk_sk(sk);
        int undo;

        if (!nlk->netlink_unbind)
                return;

        for (undo = 0; undo < group; undo++)
                if (test_bit(undo, &groups))
                        nlk->netlink_unbind(sock_net(sk), undo + 1);
}

static int netlink_bind(struct socket *sock, struct sockaddr *addr,
                        int addr_len)
{
        struct sock *sk = sock->sk;
        struct net *net = sock_net(sk);
        struct netlink_sock *nlk = nlk_sk(sk);
        struct sockaddr_nl *nladdr = (struct sockaddr_nl *)addr;
        int err = 0;
        unsigned long groups;
        bool bound;

        if (addr_len < sizeof(struct sockaddr_nl))
                return -EINVAL;

        if (nladdr->nl_family != AF_NETLINK)
                return -EINVAL;
        groups = nladdr->nl_groups;

        /* Only superuser is allowed to listen multicasts */
        if (groups) {
                if (!netlink_allowed(sock, NL_CFG_F_NONROOT_RECV))
                        return -EPERM;
                err = netlink_realloc_groups(sk);
                if (err)
                        return err;
        }

        if (nlk->ngroups < BITS_PER_LONG)
                groups &= (1UL << nlk->ngroups) - 1;

        bound = nlk->bound;
        if (bound) {
                /* Ensure nlk->portid is up-to-date. */
                smp_rmb();

                if (nladdr->nl_pid != nlk->portid)
                        return -EINVAL;
        }

        netlink_lock_table();
        if (nlk->netlink_bind && groups) {
                int group;

                for (group = 0; group < nlk->ngroups; group++) {
                        if (!test_bit(group, &groups))
                                continue;
                        err = nlk->netlink_bind(net, group + 1);
                        if (!err)
                                continue;
                        netlink_undo_bind(group, groups, sk);
                        goto unlock;
                }
        }

        /* No need for barriers here as we return to user-space without
         * using any of the bound attributes.
         */
        if (!bound) {
                err = nladdr->nl_pid ?
                        netlink_insert(sk, nladdr->nl_pid) :
                        netlink_autobind(sock);
                if (err) {
                        netlink_undo_bind(nlk->ngroups, groups, sk);
                        goto unlock;
                }
        }

        if (!groups && (nlk->groups == NULL || !(u32)nlk->groups[0]))
                goto unlock;
        netlink_unlock_table();

        netlink_table_grab();
        netlink_update_subscriptions(sk, nlk->subscriptions +
                                         hweight32(groups) -
                                         hweight32(nlk->groups[0]));
        nlk->groups[0] = (nlk->groups[0] & ~0xffffffffUL) | groups;
        netlink_update_listeners(sk);
        netlink_table_ungrab();

        return 0;

unlock:
        netlink_unlock_table();
        return err;
}

static int netlink_connect(struct socket *sock, struct sockaddr *addr,
                           int alen, int flags)
{
        int err = 0;
        struct sock *sk = sock->sk;
        struct netlink_sock *nlk = nlk_sk(sk);
        struct sockaddr_nl *nladdr = (struct sockaddr_nl *)addr;

        if (alen < sizeof(addr->sa_family))
                return -EINVAL;

        if (addr->sa_family == AF_UNSPEC) {
                sk->sk_state    = NETLINK_UNCONNECTED;
                nlk->dst_portid = 0;
                nlk->dst_group  = 0;
                return 0;
        }
        if (addr->sa_family != AF_NETLINK)
                return -EINVAL;

        if (alen < sizeof(struct sockaddr_nl))
                return -EINVAL;

        if ((nladdr->nl_groups || nladdr->nl_pid) &&
            !netlink_allowed(sock, NL_CFG_F_NONROOT_SEND))
                return -EPERM;

        /* No need for barriers here as we return to user-space without
         * using any of the bound attributes.
         */
        if (!nlk->bound)
                err = netlink_autobind(sock);

        if (err == 0) {
                sk->sk_state    = NETLINK_CONNECTED;
                nlk->dst_portid = nladdr->nl_pid;
                nlk->dst_group  = ffs(nladdr->nl_groups);
        }

        return err;
}

static int netlink_getname(struct socket *sock, struct sockaddr *addr,
                           int peer)
{
        struct sock *sk = sock->sk;
        struct netlink_sock *nlk = nlk_sk(sk);
        DECLARE_SOCKADDR(struct sockaddr_nl *, nladdr, addr);

        nladdr->nl_family = AF_NETLINK;
        nladdr->nl_pad = 0;

        if (peer) {
                nladdr->nl_pid = nlk->dst_portid;
                nladdr->nl_groups = netlink_group_mask(nlk->dst_group);
        } else {
                nladdr->nl_pid = nlk->portid;
                netlink_lock_table();
                nladdr->nl_groups = nlk->groups ? nlk->groups[0] : 0;
                netlink_unlock_table();
        }
        return sizeof(*nladdr);
}

static int netlink_ioctl(struct socket *sock, unsigned int cmd,
                         unsigned long arg)
{
        /* try to hand this ioctl down to the NIC drivers.
         */
        return -ENOIOCTLCMD;
}

static struct sock *netlink_getsockbyportid(struct sock *ssk, u32 portid)
{
        struct sock *sock;
        struct netlink_sock *nlk;

        sock = netlink_lookup(sock_net(ssk), ssk->sk_protocol, portid);
        if (!sock)
                return ERR_PTR(-ECONNREFUSED);

        /* Don't bother queuing skb if kernel socket has no input function */
        nlk = nlk_sk(sock);
        if (sock->sk_state == NETLINK_CONNECTED &&
            nlk->dst_portid != nlk_sk(ssk)->portid) {
                sock_put(sock);
                return ERR_PTR(-ECONNREFUSED);
        }
        return sock;
}

struct sock *netlink_getsockbyfilp(struct file *filp)
{
        struct inode *inode = file_inode(filp);
        struct sock *sock;

        if (!S_ISSOCK(inode->i_mode))
                return ERR_PTR(-ENOTSOCK);

        sock = SOCKET_I(inode)->sk;
        if (sock->sk_family != AF_NETLINK)
                return ERR_PTR(-EINVAL);

        sock_hold(sock);
        return sock;
}

static struct sk_buff *netlink_alloc_large_skb(unsigned int size,
                                               int broadcast)
{
        struct sk_buff *skb;
        void *data;

        if (size <= NLMSG_GOODSIZE || broadcast)
                return alloc_skb(size, GFP_KERNEL);

        size = SKB_DATA_ALIGN(size) +
               SKB_DATA_ALIGN(sizeof(struct skb_shared_info));

        data = vmalloc(size);
        if (data == NULL)
                return NULL;

        skb = __build_skb(data, size);
        if (skb == NULL)
                vfree(data);
        else
                skb->destructor = netlink_skb_destructor;

        return skb;
}

/*
 * Attach a skb to a netlink socket.
 * The caller must hold a reference to the destination socket. On error, the
 * reference is dropped. The skb is not send to the destination, just all
 * all error checks are performed and memory in the queue is reserved.
 * Return values:
 * < 0: error. skb freed, reference to sock dropped.
 * 0: continue
 * 1: repeat lookup - reference dropped while waiting for socket memory.
 */
int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
                      long *timeo, struct sock *ssk)
{
        struct netlink_sock *nlk;

        nlk = nlk_sk(sk);

        if ((atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
             test_bit(NETLINK_S_CONGESTED, &nlk->state))) {
                DECLARE_WAITQUEUE(wait, current);
                if (!*timeo) {
                        if (!ssk || netlink_is_kernel(ssk))
                                netlink_overrun(sk);
                        sock_put(sk);
                        kfree_skb(skb);
                        return -EAGAIN;
                }

                __set_current_state(TASK_INTERRUPTIBLE);
                add_wait_queue(&nlk->wait, &wait);

                if ((atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
                     test_bit(NETLINK_S_CONGESTED, &nlk->state)) &&
                    !sock_flag(sk, SOCK_DEAD))
                        *timeo = schedule_timeout(*timeo);

                __set_current_state(TASK_RUNNING);
                remove_wait_queue(&nlk->wait, &wait);
                sock_put(sk);

                if (signal_pending(current)) {
                        kfree_skb(skb);
                        return sock_intr_errno(*timeo);
                }
                return 1;
        }
        netlink_skb_set_owner_r(skb, sk);
        return 0;
}

static int __netlink_sendskb(struct sock *sk, struct sk_buff *skb)
{
        int len = skb->len;

        netlink_deliver_tap(sock_net(sk), skb);

        skb_queue_tail(&sk->sk_receive_queue, skb);
        sk->sk_data_ready(sk);
        return len;
}

int netlink_sendskb(struct sock *sk, struct sk_buff *skb)
{
        int len = __netlink_sendskb(sk, skb);

        sock_put(sk);
        return len;
}

void netlink_detachskb(struct sock *sk, struct sk_buff *skb)
{
        kfree_skb(skb);
        sock_put(sk);
}

static struct sk_buff *netlink_trim(struct sk_buff *skb, gfp_t allocation)
{
        int delta;

        WARN_ON(skb->sk != NULL);
        delta = skb->end - skb->tail;
        if (is_vmalloc_addr(skb->head) || delta * 2 < skb->truesize)
                return skb;

        if (skb_shared(skb)) {
                struct sk_buff *nskb = skb_clone(skb, allocation);
                if (!nskb)
                        return skb;
                consume_skb(skb);
                skb = nskb;
        }

        pskb_expand_head(skb, 0, -delta,
                         (allocation & ~__GFP_DIRECT_RECLAIM) |
                         __GFP_NOWARN | __GFP_NORETRY);
        return skb;
}

static int netlink_unicast_kernel(struct sock *sk, struct sk_buff *skb,
                                  struct sock *ssk)
{
        int ret;
        struct netlink_sock *nlk = nlk_sk(sk);

        ret = -ECONNREFUSED;
        if (nlk->netlink_rcv != NULL) {
                ret = skb->len;
                netlink_skb_set_owner_r(skb, sk);
                NETLINK_CB(skb).sk = ssk;
                netlink_deliver_tap_kernel(sk, ssk, skb);
                nlk->netlink_rcv(skb);
                consume_skb(skb);
        } else {
                kfree_skb(skb);
        }
        sock_put(sk);
        return ret;
}

int netlink_unicast(struct sock *ssk, struct sk_buff *skb,
                    u32 portid, int nonblock)
{
        struct sock *sk;
        int err;
        long timeo;

        skb = netlink_trim(skb, gfp_any());

        timeo = sock_sndtimeo(ssk, nonblock);
retry:
        sk = netlink_getsockbyportid(ssk, portid);
        if (IS_ERR(sk)) {
                kfree_skb(skb);
                return PTR_ERR(sk);
        }
        if (netlink_is_kernel(sk))
                return netlink_unicast_kernel(sk, skb, ssk);

        if (sk_filter(sk, skb)) {
                err = skb->len;
                kfree_skb(skb);
                sock_put(sk);
                return err;
        }

        err = netlink_attachskb(sk, skb, &timeo, ssk);
        if (err == 1)
                goto retry;
        if (err)
                return err;

        return netlink_sendskb(sk, skb);
}
EXPORT_SYMBOL(netlink_unicast);

int netlink_has_listeners(struct sock *sk, unsigned int group)
{
        int res = 0;
        struct listeners *listeners;

        BUG_ON(!netlink_is_kernel(sk));

        rcu_read_lock();
        listeners = rcu_dereference(nl_table[sk->sk_protocol].listeners);

        if (listeners && group - 1 < nl_table[sk->sk_protocol].groups)
                res = test_bit(group - 1, listeners->masks);

        rcu_read_unlock();

        return res;
}
EXPORT_SYMBOL_GPL(netlink_has_listeners);

bool netlink_strict_get_check(struct sk_buff *skb)
{
        const struct netlink_sock *nlk = nlk_sk(NETLINK_CB(skb).sk);

        return nlk->flags & NETLINK_F_STRICT_CHK;
}
EXPORT_SYMBOL_GPL(netlink_strict_get_check);

static int netlink_broadcast_deliver(struct sock *sk, struct sk_buff *skb)
{
        struct netlink_sock *nlk = nlk_sk(sk);

        if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&
            !test_bit(NETLINK_S_CONGESTED, &nlk->state)) {
                netlink_skb_set_owner_r(skb, sk);
                __netlink_sendskb(sk, skb);
                return atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1);
        }
        return -1;
}

struct netlink_broadcast_data {
        struct sock *exclude_sk;
        struct net *net;
        u32 portid;
        u32 group;
        int failure;
        int delivery_failure;
        int congested;
        int delivered;
        gfp_t allocation;
        struct sk_buff *skb, *skb2;
        int (*tx_filter)(struct sock *dsk, struct sk_buff *skb, void *data);
        void *tx_data;
};

static void do_one_broadcast(struct sock *sk,
                                    struct netlink_broadcast_data *p)
{
        struct netlink_sock *nlk = nlk_sk(sk);
        int val;

        if (p->exclude_sk == sk)
                return;

        if (nlk->portid == p->portid || p->group - 1 >= nlk->ngroups ||
            !test_bit(p->group - 1, nlk->groups))
                return;

        if (!net_eq(sock_net(sk), p->net)) {
                if (!(nlk->flags & NETLINK_F_LISTEN_ALL_NSID))
                        return;

                if (!peernet_has_id(sock_net(sk), p->net))
                        return;

                if (!file_ns_capable(sk->sk_socket->file, p->net->user_ns,
                                     CAP_NET_BROADCAST))
                        return;
        }

        if (p->failure) {
                netlink_overrun(sk);
                return;
        }

        sock_hold(sk);
        if (p->skb2 == NULL) {
                if (skb_shared(p->skb)) {
                        p->skb2 = skb_clone(p->skb, p->allocation);
                } else {
                        p->skb2 = skb_get(p->skb);
                        /*
                         * skb ownership may have been set when
                         * delivered to a previous socket.
                         */
                        skb_orphan(p->skb2);
                }
        }
        if (p->skb2 == NULL) {
                netlink_overrun(sk);
                /* Clone failed. Notify ALL listeners. */
                p->failure = 1;
                if (nlk->flags & NETLINK_F_BROADCAST_SEND_ERROR)
                        p->delivery_failure = 1;
                goto out;
        }
        if (p->tx_filter && p->tx_filter(sk, p->skb2, p->tx_data)) {
                kfree_skb(p->skb2);
                p->skb2 = NULL;
                goto out;
        }
        if (sk_filter(sk, p->skb2)) {
                kfree_skb(p->skb2);
                p->skb2 = NULL;
                goto out;
        }
        NETLINK_CB(p->skb2).nsid = peernet2id(sock_net(sk), p->net);
        if (NETLINK_CB(p->skb2).nsid != NETNSA_NSID_NOT_ASSIGNED)
                NETLINK_CB(p->skb2).nsid_is_set = true;
        val = netlink_broadcast_deliver(sk, p->skb2);
        if (val < 0) {
                netlink_overrun(sk);
                if (nlk->flags & NETLINK_F_BROADCAST_SEND_ERROR)
                        p->delivery_failure = 1;
        } else {
                p->congested |= val;
                p->delivered = 1;
                p->skb2 = NULL;
        }
out:
        sock_put(sk);
}

int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb, u32 portid,
        u32 group, gfp_t allocation,
        int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
        void *filter_data)
{
        struct net *net = sock_net(ssk);
        struct netlink_broadcast_data info;
        struct sock *sk;

        skb = netlink_trim(skb, allocation);

        info.exclude_sk = ssk;
        info.net = net;
        info.portid = portid;
        info.group = group;
        info.failure = 0;
        info.delivery_failure = 0;
        info.congested = 0;
        info.delivered = 0;
        info.allocation = allocation;
        info.skb = skb;
        info.skb2 = NULL;
        info.tx_filter = filter;
        info.tx_data = filter_data;

        /* While we sleep in clone, do not allow to change socket list */

        netlink_lock_table();

        sk_for_each_bound(sk, &nl_table[ssk->sk_protocol].mc_list)
                do_one_broadcast(sk, &info);

        consume_skb(skb);

        netlink_unlock_table();

        if (info.delivery_failure) {
                kfree_skb(info.skb2);
                return -ENOBUFS;
        }
        consume_skb(info.skb2);

        if (info.delivered) {
                if (info.congested && gfpflags_allow_blocking(allocation))
                        yield();
                return 0;
        }
        return -ESRCH;
}
EXPORT_SYMBOL(netlink_broadcast_filtered);

int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 portid,
                      u32 group, gfp_t allocation)
{
        return netlink_broadcast_filtered(ssk, skb, portid, group, allocation,
                NULL, NULL);
}
EXPORT_SYMBOL(netlink_broadcast);

struct netlink_set_err_data {
        struct sock *exclude_sk;
        u32 portid;
        u32 group;
        int code;
};

static int do_one_set_err(struct sock *sk, struct netlink_set_err_data *p)
{
        struct netlink_sock *nlk = nlk_sk(sk);
        int ret = 0;

        if (sk == p->exclude_sk)
                goto out;

        if (!net_eq(sock_net(sk), sock_net(p->exclude_sk)))
                goto out;

        if (nlk->portid == p->portid || p->group - 1 >= nlk->ngroups ||
            !test_bit(p->group - 1, nlk->groups))
                goto out;

        if (p->code == ENOBUFS && nlk->flags & NETLINK_F_RECV_NO_ENOBUFS) {
                ret = 1;
                goto out;
        }

        sk->sk_err = p->code;
        sk->sk_error_report(sk);
out:
        return ret;
}

/**
 * netlink_set_err - report error to broadcast listeners
 * @ssk: the kernel netlink socket, as returned by netlink_kernel_create()
 * @portid: the PORTID of a process that we want to skip (if any)
 * @group: the broadcast group that will notice the error
 * @code: error code, must be negative (as usual in kernelspace)
 *
 * This function returns the number of broadcast listeners that have set the
 * NETLINK_NO_ENOBUFS socket option.
 */
int netlink_set_err(struct sock *ssk, u32 portid, u32 group, int code)
{
        struct netlink_set_err_data info;
        struct sock *sk;
        int ret = 0;

        info.exclude_sk = ssk;
        info.portid = portid;
        info.group = group;
        /* sk->sk_err wants a positive error value */
        info.code = -code;

        read_lock(&nl_table_lock);

        sk_for_each_bound(sk, &nl_table[ssk->sk_protocol].mc_list)
                ret += do_one_set_err(sk, &info);

        read_unlock(&nl_table_lock);
        return ret;
}
EXPORT_SYMBOL(netlink_set_err);

/* must be called with netlink table grabbed */
static void netlink_update_socket_mc(struct netlink_sock *nlk,
                                     unsigned int group,
                                     int is_new)
{
        int old, new = !!is_new, subscriptions;

        old = test_bit(group - 1, nlk->groups);
        subscriptions = nlk->subscriptions - old + new;
        if (new)
                __set_bit(group - 1, nlk->groups);
        else
                __clear_bit(group - 1, nlk->groups);
        netlink_update_subscriptions(&nlk->sk, subscriptions);
        netlink_update_listeners(&nlk->sk);
}

static int netlink_setsockopt(struct socket *sock, int level, int optname,
                              char __user *optval, unsigned int optlen)
{
        struct sock *sk = sock->sk;
        struct netlink_sock *nlk = nlk_sk(sk);
        unsigned int val = 0;
        int err;

        if (level != SOL_NETLINK)
                return -ENOPROTOOPT;

        if (optlen >= sizeof(int) &&
            get_user(val, (unsigned int __user *)optval))
                return -EFAULT;

        switch (optname) {
        case NETLINK_PKTINFO:
                if (val)
                        nlk->flags |= NETLINK_F_RECV_PKTINFO;
                else
                        nlk->flags &= ~NETLINK_F_RECV_PKTINFO;
                err = 0;
                break;
        case NETLINK_ADD_MEMBERSHIP:
        case NETLINK_DROP_MEMBERSHIP: {
                if (!netlink_allowed(sock, NL_CFG_F_NONROOT_RECV))
                        return -EPERM;
                err = netlink_realloc_groups(sk);
                if (err)
                        return err;
                if (!val || val - 1 >= nlk->ngroups)
                        return -EINVAL;
                if (optname == NETLINK_ADD_MEMBERSHIP && nlk->netlink_bind) {
                        err = nlk->netlink_bind(sock_net(sk), val);
                        if (err)
                                return err;
                }
                netlink_table_grab();
                netlink_update_socket_mc(nlk, val,
                                         optname == NETLINK_ADD_MEMBERSHIP);
                netlink_table_ungrab();
                if (optname == NETLINK_DROP_MEMBERSHIP && nlk->netlink_unbind)
                        nlk->netlink_unbind(sock_net(sk), val);

                err = 0;
                break;
        }
        case NETLINK_BROADCAST_ERROR:
                if (val)
                        nlk->flags |= NETLINK_F_BROADCAST_SEND_ERROR;
                else
                        nlk->flags &= ~NETLINK_F_BROADCAST_SEND_ERROR;
                err = 0;
                break;
        case NETLINK_NO_ENOBUFS:
                if (val) {
                        nlk->flags |= NETLINK_F_RECV_NO_ENOBUFS;
                        clear_bit(NETLINK_S_CONGESTED, &nlk->state);
                        wake_up_interruptible(&nlk->wait);
                } else {
                        nlk->flags &= ~NETLINK_F_RECV_NO_ENOBUFS;
                }
                err = 0;
                break;
        case NETLINK_LISTEN_ALL_NSID:
                if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_BROADCAST))
                        return -EPERM;

                if (val)
                        nlk->flags |= NETLINK_F_LISTEN_ALL_NSID;
                else
                        nlk->flags &= ~NETLINK_F_LISTEN_ALL_NSID;
                err = 0;
                break;
        case NETLINK_CAP_ACK:
                if (val)
                        nlk->flags |= NETLINK_F_CAP_ACK;
                else
                        nlk->flags &= ~NETLINK_F_CAP_ACK;
                err = 0;
                break;
        case NETLINK_EXT_ACK:
                if (val)
                        nlk->flags |= NETLINK_F_EXT_ACK;
                else
                        nlk->flags &= ~NETLINK_F_EXT_ACK;
                err = 0;
                break;
        case NETLINK_GET_STRICT_CHK:
                if (val)
                        nlk->flags |= NETLINK_F_STRICT_CHK;
                else
                        nlk->flags &= ~NETLINK_F_STRICT_CHK;
                err = 0;
                break;
        default:
                err = -ENOPROTOOPT;
        }
        return err;
}

static int netlink_getsockopt(struct socket *sock, int level, int optname,
                              char __user *optval, int __user *optlen)
{
        struct sock *sk = sock->sk;
        struct netlink_sock *nlk = nlk_sk(sk);
        int len, val, err;

        if (level != SOL_NETLINK)
                return -ENOPROTOOPT;

        if (get_user(len, optlen))
                return -EFAULT;
        if (len < 0)
                return -EINVAL;

        switch (optname) {
        case NETLINK_PKTINFO:
                if (len < sizeof(int))
                        return -EINVAL;
                len = sizeof(int);
                val = nlk->flags & NETLINK_F_RECV_PKTINFO ? 1 : 0;
                if (put_user(len, optlen) ||
                    put_user(val, optval))
                        return -EFAULT;
                err = 0;
                break;
        case NETLINK_BROADCAST_ERROR:
                if (len < sizeof(int))
                        return -EINVAL;
                len = sizeof(int);
                val = nlk->flags & NETLINK_F_BROADCAST_SEND_ERROR ? 1 : 0;
                if (put_user(len, optlen) ||
                    put_user(val, optval))
                        return -EFAULT;
                err = 0;
                break;
        case NETLINK_NO_ENOBUFS:
                if (len < sizeof(int))
                        return -EINVAL;
                len = sizeof(int);
                val = nlk->flags & NETLINK_F_RECV_NO_ENOBUFS ? 1 : 0;
                if (put_user(len, optlen) ||
                    put_user(val, optval))
                        return -EFAULT;
                err = 0;
                break;
        case NETLINK_LIST_MEMBERSHIPS: {
                int pos, idx, shift;

                err = 0;
                netlink_lock_table();
                for (pos = 0; pos * 8 < nlk->ngroups; pos += sizeof(u32)) {
                        if (len - pos < sizeof(u32))
                                break;

                        idx = pos / sizeof(unsigned long);
                        shift = (pos % sizeof(unsigned long)) * 8;
                        if (put_user((u32)(nlk->groups[idx] >> shift),
                                     (u32 __user *)(optval + pos))) {
                                err = -EFAULT;
                                break;
                        }
                }
                if (put_user(ALIGN(nlk->ngroups / 8, sizeof(u32)), optlen))
                        err = -EFAULT;
                netlink_unlock_table();
                break;
        }
        case NETLINK_CAP_ACK:
                if (len < sizeof(int))
                        return -EINVAL;
                len = sizeof(int);
                val = nlk->flags & NETLINK_F_CAP_ACK ? 1 : 0;
                if (put_user(len, optlen) ||
                    put_user(val, optval))
                        return -EFAULT;
                err = 0;
                break;
        case NETLINK_EXT_ACK:
                if (len < sizeof(int))
                        return -EINVAL;
                len = sizeof(int);
                val = nlk->flags & NETLINK_F_EXT_ACK ? 1 : 0;
                if (put_user(len, optlen) || put_user(val, optval))
                        return -EFAULT;
                err = 0;
                break;
        case NETLINK_GET_STRICT_CHK:
                if (len < sizeof(int))
                        return -EINVAL;
                len = sizeof(int);
                val = nlk->flags & NETLINK_F_STRICT_CHK ? 1 : 0;
                if (put_user(len, optlen) || put_user(val, optval))
                        return -EFAULT;
                err = 0;
                break;
        default:
                err = -ENOPROTOOPT;
        }
        return err;
}

static void netlink_cmsg_recv_pktinfo(struct msghdr *msg, struct sk_buff *skb)
{
        struct nl_pktinfo info;

        info.group = NETLINK_CB(skb).dst_group;
        put_cmsg(msg, SOL_NETLINK, NETLINK_PKTINFO, sizeof(info), &info);
}

static void netlink_cmsg_listen_all_nsid(struct sock *sk, struct msghdr *msg,
                                         struct sk_buff *skb)
{
        if (!NETLINK_CB(skb).nsid_is_set)
                return;

        put_cmsg(msg, SOL_NETLINK, NETLINK_LISTEN_ALL_NSID, sizeof(int),
                 &NETLINK_CB(skb).nsid);
}

static int netlink_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
{
        struct sock *sk = sock->sk;
        struct netlink_sock *nlk = nlk_sk(sk);
        DECLARE_SOCKADDR(struct sockaddr_nl *, addr, msg->msg_name);
        u32 dst_portid;
        u32 dst_group;
        struct sk_buff *skb;
        int err;
        struct scm_cookie scm;
        u32 netlink_skb_flags = 0;

        if (msg->msg_flags&MSG_OOB)
                return -EOPNOTSUPP;

        err = scm_send(sock, msg, &scm, true);
        if (err < 0)
                return err;

        if (msg->msg_namelen) {
                err = -EINVAL;
                if (msg->msg_namelen < sizeof(struct sockaddr_nl))
                        goto out;
                if (addr->nl_family != AF_NETLINK)
                        goto out;
                dst_portid = addr->nl_pid;
                dst_group = ffs(addr->nl_groups);
                err =  -EPERM;
                if ((dst_group || dst_portid) &&
                    !netlink_allowed(sock, NL_CFG_F_NONROOT_SEND))
                        goto out;
                netlink_skb_flags |= NETLINK_SKB_DST;
        } else {
                dst_portid = nlk->dst_portid;
                dst_group = nlk->dst_group;
        }

        if (!nlk->bound) {
                err = netlink_autobind(sock);
                if (err)
                        goto out;
        } else {
                /* Ensure nlk is hashed and visible. */
                smp_rmb();
        }

        err = -EMSGSIZE;
        if (len > sk->sk_sndbuf - 32)
                goto out;
        err = -ENOBUFS;
        skb = netlink_alloc_large_skb(len, dst_group);
        if (skb == NULL)
                goto out;

        NETLINK_CB(skb).portid  = nlk->portid;
        NETLINK_CB(skb).dst_group = dst_group;
        NETLINK_CB(skb).creds   = scm.creds;
        NETLINK_CB(skb).flags   = netlink_skb_flags;

        err = -EFAULT;
        if (memcpy_from_msg(skb_put(skb, len), msg, len)) {
                kfree_skb(skb);
                goto out;
        }

        err = security_netlink_send(sk, skb);
        if (err) {
                kfree_skb(skb);
                goto out;
        }

        if (dst_group) {
                refcount_inc(&skb->users);
                netlink_broadcast(sk, skb, dst_portid, dst_group, GFP_KERNEL);
        }
        err = netlink_unicast(sk, skb, dst_portid, msg->msg_flags&MSG_DONTWAIT);

out:
        scm_destroy(&scm);
        return err;
}

static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
                           int flags)
{
        struct scm_cookie scm;
        struct sock *sk = sock->sk;
        struct netlink_sock *nlk = nlk_sk(sk);
        int noblock = flags&MSG_DONTWAIT;
        size_t copied;
        struct sk_buff *skb, *data_skb;
        int err, ret;

        if (flags&MSG_OOB)
                return -EOPNOTSUPP;

        copied = 0;

        skb = skb_recv_datagram(sk, flags, noblock, &err);
        if (skb == NULL)
                goto out;

        data_skb = skb;

#ifdef CONFIG_COMPAT_NETLINK_MESSAGES
        if (unlikely(skb_shinfo(skb)->frag_list)) {
                /*
                 * If this skb has a frag_list, then here that means that we
                 * will have to use the frag_list skb's data for compat tasks
                 * and the regular skb's data for normal (non-compat) tasks.
                 *
                 * If we need to send the compat skb, assign it to the
                 * 'data_skb' variable so that it will be used below for data
                 * copying. We keep 'skb' for everything else, including
                 * freeing both later.
                 */
                if (flags & MSG_CMSG_COMPAT)
                        data_skb = skb_shinfo(skb)->frag_list;
        }
#endif

        /* Record the max length of recvmsg() calls for future allocations */
        nlk->max_recvmsg_len = max(nlk->max_recvmsg_len, len);
        nlk->max_recvmsg_len = min_t(size_t, nlk->max_recvmsg_len,
                                     SKB_WITH_OVERHEAD(32768));

        copied = data_skb->len;
        if (len < copied) {
                msg->msg_flags |= MSG_TRUNC;
                copied = len;
        }

        skb_reset_transport_header(data_skb);
        err = skb_copy_datagram_msg(data_skb, 0, msg, copied);

        if (msg->msg_name) {
                DECLARE_SOCKADDR(struct sockaddr_nl *, addr, msg->msg_name);
                addr->nl_family = AF_NETLINK;
                addr->nl_pad    = 0;
                addr->nl_pid    = NETLINK_CB(skb).portid;
                addr->nl_groups = netlink_group_mask(NETLINK_CB(skb).dst_group);
                msg->msg_namelen = sizeof(*addr);
        }

        if (nlk->flags & NETLINK_F_RECV_PKTINFO)
                netlink_cmsg_recv_pktinfo(msg, skb);
        if (nlk->flags & NETLINK_F_LISTEN_ALL_NSID)
                netlink_cmsg_listen_all_nsid(sk, msg, skb);

        memset(&scm, 0, sizeof(scm));
        scm.creds = *NETLINK_CREDS(skb);
        if (flags & MSG_TRUNC)
                copied = data_skb->len;

        skb_free_datagram(sk, skb);

        if (nlk->cb_running &&
            atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) {
                ret = netlink_dump(sk);

                if (ret) {
                        sk->sk_err = -ret;
                        sk->sk_error_report(sk);
                }
        }

        scm_recv(sock, msg, &scm, flags);
out:
        netlink_rcv_wake(sk);
        return err ? : copied;
}

static void netlink_data_ready(struct sock *sk)
{
        BUG();
}

/*
 *      We export these functions to other modules. They provide a
 *      complete set of kernel non-blocking support for message
 *      queueing.
 */

struct sock *
__netlink_kernel_create(struct net *net, int unit, struct module *module,
                        struct netlink_kernel_cfg *cfg)
{
        struct socket *sock;
        struct sock *sk;
        struct netlink_sock *nlk;
        struct listeners *listeners = NULL;
        struct mutex *cb_mutex = cfg ? cfg->cb_mutex : NULL;
        unsigned int groups;

        BUG_ON(!nl_table);

        if (unit < 0 || unit >= MAX_LINKS)
                return NULL;

        if (sock_create_lite(PF_NETLINK, SOCK_DGRAM, unit, &sock))
                return NULL;

        if (__netlink_create(net, sock, cb_mutex, unit, 1) < 0)
                goto out_sock_release_nosk;

        sk = sock->sk;

        if (!cfg || cfg->groups < 32)
                groups = 32;
        else
                groups = cfg->groups;

        listeners = kzalloc(sizeof(*listeners) + NLGRPSZ(groups), GFP_KERNEL);
        if (!listeners)
                goto out_sock_release;

        sk->sk_data_ready = netlink_data_ready;
        if (cfg && cfg->input)
                nlk_sk(sk)->netlink_rcv = cfg->input;

        if (netlink_insert(sk, 0))
                goto out_sock_release;

        nlk = nlk_sk(sk);
        nlk->flags |= NETLINK_F_KERNEL_SOCKET;

        netlink_table_grab();
        if (!nl_table[unit].registered) {
                nl_table[unit].groups = groups;
                rcu_assign_pointer(nl_table[unit].listeners, listeners);
                nl_table[unit].cb_mutex = cb_mutex;
                nl_table[unit].module = module;
                if (cfg) {
                        nl_table[unit].bind = cfg->bind;
                        nl_table[unit].unbind = cfg->unbind;
                        nl_table[unit].flags = cfg->flags;
                        if (cfg->compare)
                                nl_table[unit].compare = cfg->compare;
                }
                nl_table[unit].registered = 1;
        } else {
                kfree(listeners);
                nl_table[unit].registered++;
        }
        netlink_table_ungrab();
        return sk;

out_sock_release:
        kfree(listeners);
        netlink_kernel_release(sk);
        return NULL;

out_sock_release_nosk:
        sock_release(sock);
        return NULL;
}
EXPORT_SYMBOL(__netlink_kernel_create);

void
netlink_kernel_release(struct sock *sk)
{
        if (sk == NULL || sk->sk_socket == NULL)
                return;

        sock_release(sk->sk_socket);
}
EXPORT_SYMBOL(netlink_kernel_release);

int __netlink_change_ngroups(struct sock *sk, unsigned int groups)
{
        struct listeners *new, *old;
        struct netlink_table *tbl = &nl_table[sk->sk_protocol];

        if (groups < 32)
                groups = 32;

        if (NLGRPSZ(tbl->groups) < NLGRPSZ(groups)) {
                new = kzalloc(sizeof(*new) + NLGRPSZ(groups), GFP_ATOMIC);
                if (!new)
                        return -ENOMEM;
                old = nl_deref_protected(tbl->listeners);
                memcpy(new->masks, old->masks, NLGRPSZ(tbl->groups));
                rcu_assign_pointer(tbl->listeners, new);

                kfree_rcu(old, rcu);
        }
        tbl->groups = groups;

        return 0;
}

/**
 * netlink_change_ngroups - change number of multicast groups
 *
 * This changes the number of multicast groups that are available
 * on a certain netlink family. Note that it is not possible to
 * change the number of groups to below 32. Also note that it does
 * not implicitly call netlink_clear_multicast_users() when the
 * number of groups is reduced.
 *
 * @sk: The kernel netlink socket, as returned by netlink_kernel_create().
 * @groups: The new number of groups.
 */
int netlink_change_ngroups(struct sock *sk, unsigned int groups)
{
        int err;

        netlink_table_grab();
        err = __netlink_change_ngroups(sk, groups);
        netlink_table_ungrab();

        return err;
}

void __netlink_clear_multicast_users(struct sock *ksk, unsigned int group)
{
        struct sock *sk;
        struct netlink_table *tbl = &nl_table[ksk->sk_protocol];

        sk_for_each_bound(sk, &tbl->mc_list)
                netlink_update_socket_mc(nlk_sk(sk), group, 0);
}

struct nlmsghdr *
__nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags)
{
        struct nlmsghdr *nlh;
        int size = nlmsg_msg_size(len);

        nlh = skb_put(skb, NLMSG_ALIGN(size));
        nlh->nlmsg_type = type;
        nlh->nlmsg_len = size;
        nlh->nlmsg_flags = flags;
        nlh->nlmsg_pid = portid;
        nlh->nlmsg_seq = seq;
        if (!__builtin_constant_p(size) || NLMSG_ALIGN(size) - size != 0)
                memset(nlmsg_data(nlh) + len, 0, NLMSG_ALIGN(size) - size);
        return nlh;
}
EXPORT_SYMBOL(__nlmsg_put);

/*
 * It looks a bit ugly.
 * It would be better to create kernel thread.
 */

static int netlink_dump(struct sock *sk)
{
        struct netlink_sock *nlk = nlk_sk(sk);
        struct netlink_ext_ack extack = {};
        struct netlink_callback *cb;
        struct sk_buff *skb = NULL;
        struct nlmsghdr *nlh;
        struct module *module;
        int err = -ENOBUFS;
        int alloc_min_size;
        int alloc_size;

        mutex_lock(nlk->cb_mutex);
        if (!nlk->cb_running) {
                err = -EINVAL;
                goto errout_skb;
        }

        if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
                goto errout_skb;

        /* NLMSG_GOODSIZE is small to avoid high order allocations being
         * required, but it makes sense to _attempt_ a 16K bytes allocation
         * to reduce number of system calls on dump operations, if user
         * ever provided a big enough buffer.
         */
        cb = &nlk->cb;
        alloc_min_size = max_t(int, cb->min_dump_alloc, NLMSG_GOODSIZE);

        if (alloc_min_size < nlk->max_recvmsg_len) {
                alloc_size = nlk->max_recvmsg_len;
                skb = alloc_skb(alloc_size,
                                (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) |
                                __GFP_NOWARN | __GFP_NORETRY);
        }
        if (!skb) {
                alloc_size = alloc_min_size;
                skb = alloc_skb(alloc_size, GFP_KERNEL);
        }
        if (!skb)
                goto errout_skb;

        /* Trim skb to allocated size. User is expected to provide buffer as
         * large as max(min_dump_alloc, 16KiB (mac_recvmsg_len capped at
         * netlink_recvmsg())). dump will pack as many smaller messages as
         * could fit within the allocated skb. skb is typically allocated
         * with larger space than required (could be as much as near 2x the
         * requested size with align to next power of 2 approach). Allowing
         * dump to use the excess space makes it difficult for a user to have a
         * reasonable static buffer based on the expected largest dump of a
         * single netdev. The outcome is MSG_TRUNC error.
         */
        skb_reserve(skb, skb_tailroom(skb) - alloc_size);
        netlink_skb_set_owner_r(skb, sk);

        if (nlk->dump_done_errno > 0) {
                cb->extack = &extack;
                nlk->dump_done_errno = cb->dump(skb, cb);
                cb->extack = NULL;
        }

        if (nlk->dump_done_errno > 0 ||
            skb_tailroom(skb) < nlmsg_total_size(sizeof(nlk->dump_done_errno))) {
                mutex_unlock(nlk->cb_mutex);

                if (sk_filter(sk, skb))
                        kfree_skb(skb);
                else
                        __netlink_sendskb(sk, skb);
                return 0;
        }

        nlh = nlmsg_put_answer(skb, cb, NLMSG_DONE,
                               sizeof(nlk->dump_done_errno),
                               NLM_F_MULTI | cb->answer_flags);
        if (WARN_ON(!nlh))
                goto errout_skb;

        nl_dump_check_consistent(cb, nlh);

        memcpy(nlmsg_data(nlh), &nlk->dump_done_errno,
               sizeof(nlk->dump_done_errno));

        if (extack._msg && nlk->flags & NETLINK_F_EXT_ACK) {
                nlh->nlmsg_flags |= NLM_F_ACK_TLVS;
                if (!nla_put_string(skb, NLMSGERR_ATTR_MSG, extack._msg))
                        nlmsg_end(skb, nlh);
        }

        if (sk_filter(sk, skb))
                kfree_skb(skb);
        else
                __netlink_sendskb(sk, skb);

        if (cb->done)
                cb->done(cb);

        nlk->cb_running = false;
        module = cb->module;
        skb = cb->skb;
        mutex_unlock(nlk->cb_mutex);
        module_put(module);
        consume_skb(skb);
        return 0;

errout_skb:
        mutex_unlock(nlk->cb_mutex);
        kfree_skb(skb);
        return err;
}

int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
                         const struct nlmsghdr *nlh,
                         struct netlink_dump_control *control)
{
        struct netlink_sock *nlk, *nlk2;
        struct netlink_callback *cb;
        struct sock *sk;
        int ret;

        refcount_inc(&skb->users);

        sk = netlink_lookup(sock_net(ssk), ssk->sk_protocol, NETLINK_CB(skb).portid);
        if (sk == NULL) {
                ret = -ECONNREFUSED;
                goto error_free;
        }

        nlk = nlk_sk(sk);
        mutex_lock(nlk->cb_mutex);
        /* A dump is in progress... */
        if (nlk->cb_running) {
                ret = -EBUSY;
                goto error_unlock;
        }
        /* add reference of module which cb->dump belongs to */
        if (!try_module_get(control->module)) {
                ret = -EPROTONOSUPPORT;
                goto error_unlock;
        }

        cb = &nlk->cb;
        memset(cb, 0, sizeof(*cb));
        cb->dump = control->dump;
        cb->done = control->done;
        cb->nlh = nlh;
        cb->data = control->data;
        cb->module = control->module;
        cb->min_dump_alloc = control->min_dump_alloc;
        cb->skb = skb;

        nlk2 = nlk_sk(NETLINK_CB(skb).sk);
        cb->strict_check = !!(nlk2->flags & NETLINK_F_STRICT_CHK);

        if (control->start) {
                ret = control->start(cb);
                if (ret)
                        goto error_put;
        }

        nlk->cb_running = true;
        nlk->dump_done_errno = INT_MAX;

        mutex_unlock(nlk->cb_mutex);

        ret = netlink_dump(sk);

        sock_put(sk);

        if (ret)
                return ret;

        /* We successfully started a dump, by returning -EINTR we
         * signal not to send ACK even if it was requested.
         */
        return -EINTR;

error_put:
        module_put(control->module);
error_unlock:
        sock_put(sk);
        mutex_unlock(nlk->cb_mutex);
error_free:
        kfree_skb(skb);
        return ret;
}
EXPORT_SYMBOL(__netlink_dump_start);

void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
                 const struct netlink_ext_ack *extack)
{
        struct sk_buff *skb;
        struct nlmsghdr *rep;
        struct nlmsgerr *errmsg;
        size_t payload = sizeof(*errmsg);
        size_t tlvlen = 0;
        struct netlink_sock *nlk = nlk_sk(NETLINK_CB(in_skb).sk);
        unsigned int flags = 0;
        bool nlk_has_extack = nlk->flags & NETLINK_F_EXT_ACK;

        /* Error messages get the original request appened, unless the user
         * requests to cap the error message, and get extra error data if
         * requested.
         */
        if (nlk_has_extack && extack && extack->_msg)
                tlvlen += nla_total_size(strlen(extack->_msg) + 1);

        if (err) {
                if (!(nlk->flags & NETLINK_F_CAP_ACK))
                        payload += nlmsg_len(nlh);
                else
                        flags |= NLM_F_CAPPED;
                if (nlk_has_extack && extack && extack->bad_attr)
                        tlvlen += nla_total_size(sizeof(u32));
        } else {
                flags |= NLM_F_CAPPED;

                if (nlk_has_extack && extack && extack->cookie_len)
                        tlvlen += nla_total_size(extack->cookie_len);
        }

        if (tlvlen)
                flags |= NLM_F_ACK_TLVS;

        skb = nlmsg_new(payload + tlvlen, GFP_KERNEL);
        if (!skb) {
                NETLINK_CB(in_skb).sk->sk_err = ENOBUFS;
                NETLINK_CB(in_skb).sk->sk_error_report(NETLINK_CB(in_skb).sk);
                return;
        }

        rep = __nlmsg_put(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
                          NLMSG_ERROR, payload, flags);
        errmsg = nlmsg_data(rep);
        errmsg->error = err;
        memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh));

        if (nlk_has_extack && extack) {
                if (extack->_msg) {
                        WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG,
                                               extack->_msg));
                }
                if (err) {
                        if (extack->bad_attr &&
                            !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
                                     (u8 *)extack->bad_attr >= in_skb->data +
                                                               in_skb->len))
                                WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
                                                    (u8 *)extack->bad_attr -
                                                    in_skb->data));
                } else {
                        if (extack->cookie_len)
                                WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
                                                extack->cookie_len,
                                                extack->cookie));
                }
        }

        nlmsg_end(skb, rep);

        netlink_unicast(in_skb->sk, skb, NETLINK_CB(in_skb).portid, MSG_DONTWAIT);
}
EXPORT_SYMBOL(netlink_ack);

int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct sk_buff *,
                                                   struct nlmsghdr *,
                                                   struct netlink_ext_ack *))
{
        struct netlink_ext_ack extack;
        struct nlmsghdr *nlh;
        int err;

        while (skb->len >= nlmsg_total_size(0)) {
                int msglen;

                memset(&extack, 0, sizeof(extack));
                nlh = nlmsg_hdr(skb);
                err = 0;

                if (nlh->nlmsg_len < NLMSG_HDRLEN || skb->len < nlh->nlmsg_len)
                        return 0;

                /* Only requests are handled by the kernel */
                if (!(nlh->nlmsg_flags & NLM_F_REQUEST))
                        goto ack;

                /* Skip control messages */
                if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
                        goto ack;

                err = cb(skb, nlh, &extack);
                if (err == -EINTR)
                        goto skip;

ack:
                if (nlh->nlmsg_flags & NLM_F_ACK || err)
                        netlink_ack(skb, nlh, err, &extack);

skip:
                msglen = NLMSG_ALIGN(nlh->nlmsg_len);
                if (msglen > skb->len)
                        msglen = skb->len;
                skb_pull(skb, msglen);
        }

        return 0;
}
EXPORT_SYMBOL(netlink_rcv_skb);

/**
 * nlmsg_notify - send a notification netlink message
 * @sk: netlink socket to use
 * @skb: notification message
 * @portid: destination netlink portid for reports or 0
 * @group: destination multicast group or 0
 * @report: 1 to report back, 0 to disable
 * @flags: allocation flags
 */
int nlmsg_notify(struct sock *sk, struct sk_buff *skb, u32 portid,
                 unsigned int group, int report, gfp_t flags)
{
        int err = 0;

        if (group) {
                int exclude_portid = 0;

                if (report) {
                        refcount_inc(&skb->users);
                        exclude_portid = portid;
                }

                /* errors reported via destination sk->sk_err, but propagate
                 * delivery errors if NETLINK_BROADCAST_ERROR flag is set */
                err = nlmsg_multicast(sk, skb, exclude_portid, group, flags);
        }

        if (report) {
                int err2;

                err2 = nlmsg_unicast(sk, skb, portid);
                if (!err || err == -ESRCH)
                        err = err2;
        }

        return err;
}
EXPORT_SYMBOL(nlmsg_notify);

#ifdef CONFIG_PROC_FS
struct nl_seq_iter {
        struct seq_net_private p;
        struct rhashtable_iter hti;
        int link;
};

static void netlink_walk_start(struct nl_seq_iter *iter)
{
        rhashtable_walk_enter(&nl_table[iter->link].hash, &iter->hti);
        rhashtable_walk_start(&iter->hti);
}

static void netlink_walk_stop(struct nl_seq_iter *iter)
{
        rhashtable_walk_stop(&iter->hti);
        rhashtable_walk_exit(&iter->hti);
}

static void *__netlink_seq_next(struct seq_file *seq)
{
        struct nl_seq_iter *iter = seq->private;
        struct netlink_sock *nlk;

        do {
                for (;;) {
                        nlk = rhashtable_walk_next(&iter->hti);

                        if (IS_ERR(nlk)) {
                                if (PTR_ERR(nlk) == -EAGAIN)
                                        continue;

                                return nlk;
                        }

                        if (nlk)
                                break;

                        netlink_walk_stop(iter);
                        if (++iter->link >= MAX_LINKS)
                                return NULL;

                        netlink_walk_start(iter);
                }
        } while (sock_net(&nlk->sk) != seq_file_net(seq));

        return nlk;
}

static void *netlink_seq_start(struct seq_file *seq, loff_t *posp)
{
        struct nl_seq_iter *iter = seq->private;
        void *obj = SEQ_START_TOKEN;
        loff_t pos;

        iter->link = 0;

        netlink_walk_start(iter);

        for (pos = *posp; pos && obj && !IS_ERR(obj); pos--)
                obj = __netlink_seq_next(seq);

        return obj;
}

static void *netlink_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        ++*pos;
        return __netlink_seq_next(seq);
}

static void netlink_seq_stop(struct seq_file *seq, void *v)
{
        struct nl_seq_iter *iter = seq->private;

        if (iter->link >= MAX_LINKS)
                return;

        netlink_walk_stop(iter);
}


static int netlink_seq_show(struct seq_file *seq, void *v)
{
        if (v == SEQ_START_TOKEN) {
                seq_puts(seq,
                         "sk               Eth Pid        Groups   "
                         "Rmem     Wmem     Dump  Locks    Drops    Inode\n");
        } else {
                struct sock *s = v;
                struct netlink_sock *nlk = nlk_sk(s);

                seq_printf(seq, "%pK %-3d %-10u %08x %-8d %-8d %-5d %-8d %-8u %-8lu\n",
                           s,
                           s->sk_protocol,
                           nlk->portid,
                           nlk->groups ? (u32)nlk->groups[0] : 0,
                           sk_rmem_alloc_get(s),
                           sk_wmem_alloc_get(s),
                           nlk->cb_running,
                           refcount_read(&s->sk_refcnt),
                           atomic_read(&s->sk_drops),
                           sock_i_ino(s)
                        );

        }
        return 0;
}

static const struct seq_operations netlink_seq_ops = {
        .start  = netlink_seq_start,
        .next   = netlink_seq_next,
        .stop   = netlink_seq_stop,
        .show   = netlink_seq_show,
};
#endif

int netlink_register_notifier(struct notifier_block *nb)
{
        return blocking_notifier_chain_register(&netlink_chain, nb);
}
EXPORT_SYMBOL(netlink_register_notifier);

int netlink_unregister_notifier(struct notifier_block *nb)
{
        return blocking_notifier_chain_unregister(&netlink_chain, nb);
}
EXPORT_SYMBOL(netlink_unregister_notifier);

static const struct proto_ops netlink_ops = {
        .family =       PF_NETLINK,
        .owner =        THIS_MODULE,
        .release =      netlink_release,
        .bind =         netlink_bind,
        .connect =      netlink_connect,
        .socketpair =   sock_no_socketpair,
        .accept =       sock_no_accept,
        .getname =      netlink_getname,
        .poll =         datagram_poll,
        .ioctl =        netlink_ioctl,
        .listen =       sock_no_listen,
        .shutdown =     sock_no_shutdown,
        .setsockopt =   netlink_setsockopt,
        .getsockopt =   netlink_getsockopt,
        .sendmsg =      netlink_sendmsg,
        .recvmsg =      netlink_recvmsg,
        .mmap =         sock_no_mmap,
        .sendpage =     sock_no_sendpage,
};

static const struct net_proto_family netlink_family_ops = {
        .family = PF_NETLINK,
        .create = netlink_create,
        .owner  = THIS_MODULE,  /* for consistency 8) */
};

static int __net_init netlink_net_init(struct net *net)
{
#ifdef CONFIG_PROC_FS
        if (!proc_create_net("netlink", 0, net->proc_net, &netlink_seq_ops,
                        sizeof(struct nl_seq_iter)))
                return -ENOMEM;
#endif
        return 0;
}

static void __net_exit netlink_net_exit(struct net *net)
{
#ifdef CONFIG_PROC_FS
        remove_proc_entry("netlink", net->proc_net);
#endif
}

static void __init netlink_add_usersock_entry(void)
{
        struct listeners *listeners;
        int groups = 32;

        listeners = kzalloc(sizeof(*listeners) + NLGRPSZ(groups), GFP_KERNEL);
        if (!listeners)
                panic("netlink_add_usersock_entry: Cannot allocate listeners\n");

        netlink_table_grab();

        nl_table[NETLINK_USERSOCK].groups = groups;
        rcu_assign_pointer(nl_table[NETLINK_USERSOCK].listeners, listeners);
        nl_table[NETLINK_USERSOCK].module = THIS_MODULE;
        nl_table[NETLINK_USERSOCK].registered = 1;
        nl_table[NETLINK_USERSOCK].flags = NL_CFG_F_NONROOT_SEND;

        netlink_table_ungrab();
}

static struct pernet_operations __net_initdata netlink_net_ops = {
        .init = netlink_net_init,
        .exit = netlink_net_exit,
};

static inline u32 netlink_hash(const void *data, u32 len, u32 seed)
{
        const struct netlink_sock *nlk = data;
        struct netlink_compare_arg arg;

        netlink_compare_arg_init(&arg, sock_net(&nlk->sk), nlk->portid);
        return jhash2((u32 *)&arg, netlink_compare_arg_len / sizeof(u32), seed);
}

static const struct rhashtable_params netlink_rhashtable_params = {
        .head_offset = offsetof(struct netlink_sock, node),
        .key_len = netlink_compare_arg_len,
        .obj_hashfn = netlink_hash,
        .obj_cmpfn = netlink_compare,
        .automatic_shrinking = true,
};

static int __init netlink_proto_init(void)
{
        int i;
        int err = proto_register(&netlink_proto, 0);

        if (err != 0)
                goto out;

        BUILD_BUG_ON(sizeof(struct netlink_skb_parms) > FIELD_SIZEOF(struct sk_buff, cb));

        nl_table = kcalloc(MAX_LINKS, sizeof(*nl_table), GFP_KERNEL);
        if (!nl_table)
                goto panic;

        for (i = 0; i < MAX_LINKS; i++) {
                if (rhashtable_init(&nl_table[i].hash,
                                    &netlink_rhashtable_params) < 0) {
                        while (--i > 0)
                                rhashtable_destroy(&nl_table[i].hash);
                        kfree(nl_table);
                        goto panic;
                }
        }

        netlink_add_usersock_entry();

        sock_register(&netlink_family_ops);
        register_pernet_subsys(&netlink_net_ops);
        register_pernet_subsys(&netlink_tap_net_ops);
        /* The netlink device handler may be needed early. */
        rtnetlink_init();
out:
        return err;
panic:
        panic("netlink_init: Cannot allocate nl_table\n");
}

core_initcall(netlink_proto_init);