ClabureDB: Classified Bug-Reports Database

   /*
    * NETLINK      Kernel-user communication protocol.
    *
    *                 Authors:        Alan Cox <alan@lxorguk.ukuu.org.uk>
    *                                 Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
    *
    *                This program is free software; you can redistribute it and/or
    *                modify it under the terms of the GNU General Public License
    *                as published by the Free Software Foundation; either version
   *                2 of the License, or (at your option) any later version.
   *
   * 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 <asm/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 <net/net_namespace.h>
  #include <net/sock.h>
  #include <net/scm.h>
  #include <net/netlink.h>
  
  #define NLGRPSZ(x)        (ALIGN(x, sizeof(unsigned long) * 8) / 8)
  #define NLGRPLONGS(x)        (NLGRPSZ(x)/sizeof(unsigned long))
  
  struct netlink_sock {
          /* struct sock has to be the first member of netlink_sock */
          struct sock                sk;
          u32                        pid;
          u32                        dst_pid;
          u32                        dst_group;
          u32                        flags;
          u32                        subscriptions;
          u32                        ngroups;
          unsigned long                *groups;
          unsigned long                state;
          wait_queue_head_t        wait;
          struct netlink_callback        *cb;
          struct mutex                *cb_mutex;
          struct mutex                cb_def_mutex;
          void                        (*netlink_rcv)(struct sk_buff *skb);
          struct module                *module;
  };
  
  #define NETLINK_KERNEL_SOCKET        0x1
  #define NETLINK_RECV_PKTINFO        0x2
  
  static inline struct netlink_sock *nlk_sk(struct sock *sk)
  {
          return container_of(sk, struct netlink_sock, sk);
  }
  
  static inline int netlink_is_kernel(struct sock *sk)
  {
          return nlk_sk(sk)->flags & NETLINK_KERNEL_SOCKET;
  }
  
  struct nl_pid_hash {
         struct hlist_head *table;
         unsigned long rehash_time;
 
         unsigned int mask;
         unsigned int shift;
 
         unsigned int entries;
         unsigned int max_shift;
 
         u32 rnd;
 };
 
 struct netlink_table {
         struct nl_pid_hash hash;
         struct hlist_head mc_list;
         unsigned long *listeners;
         unsigned int nl_nonroot;
         unsigned int groups;
         struct mutex *cb_mutex;
         struct module *module;
         int registered;
 };
 
 static struct netlink_table *nl_table;
 
 static DECLARE_WAIT_QUEUE_HEAD(nl_table_wait);
 
 static int netlink_dump(struct sock *sk);
 static void netlink_destroy_callback(struct netlink_callback *cb);
 
 static DEFINE_RWLOCK(nl_table_lock);
 static atomic_t nl_table_users = ATOMIC_INIT(0);
 
 static ATOMIC_NOTIFIER_HEAD(netlink_chain);
 
 static u32 netlink_group_mask(u32 group)
 {
         return group ? 1 << (group - 1) : 0;
 }
 
 static struct hlist_head *nl_pid_hashfn(struct nl_pid_hash *hash, u32 pid)
 {
         return &hash->table[jhash_1word(pid, hash->rnd) & hash->mask];
 }
 
 static void netlink_sock_destruct(struct sock *sk)
 {
         struct netlink_sock *nlk = nlk_sk(sk);
 
         if (nlk->cb) {
                 if (nlk->cb->done)
                         nlk->cb->done(nlk->cb);
                 netlink_destroy_callback(nlk->cb);
         }
 
         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(atomic_read(&sk->sk_wmem_alloc));
         WARN_ON(nlk_sk(sk)->groups);
 }
 
 /* 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.
  */
 
 static void netlink_table_grab(void)
         __acquires(nl_table_lock)
 {
         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);
         }
 }
 
 static 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);
 }
 
 static inline struct sock *netlink_lookup(struct net *net, int protocol,
                                           u32 pid)
 {
         struct nl_pid_hash *hash = &nl_table[protocol].hash;
         struct hlist_head *head;
         struct sock *sk;
         struct hlist_node *node;
 
         read_lock(&nl_table_lock);
         head = nl_pid_hashfn(hash, pid);
         sk_for_each(sk, node, head) {
                 if (net_eq(sock_net(sk), net) && (nlk_sk(sk)->pid == pid)) {
                         sock_hold(sk);
                         goto found;
                 }
         }
         sk = NULL;
 found:
         read_unlock(&nl_table_lock);
         return sk;
 }
 
 static inline struct hlist_head *nl_pid_hash_zalloc(size_t size)
 {
         if (size <= PAGE_SIZE)
                 return kzalloc(size, GFP_ATOMIC);
         else
                 return (struct hlist_head *)
                         __get_free_pages(GFP_ATOMIC | __GFP_ZERO,
                                          get_order(size));
 }
 
 static inline void nl_pid_hash_free(struct hlist_head *table, size_t size)
 {
         if (size <= PAGE_SIZE)
                 kfree(table);
         else
                 free_pages((unsigned long)table, get_order(size));
 }
 
 static int nl_pid_hash_rehash(struct nl_pid_hash *hash, int grow)
 {
         unsigned int omask, mask, shift;
         size_t osize, size;
         struct hlist_head *otable, *table;
         int i;
 
         omask = mask = hash->mask;
         osize = size = (mask + 1) * sizeof(*table);
         shift = hash->shift;
 
         if (grow) {
                 if (++shift > hash->max_shift)
                         return 0;
                 mask = mask * 2 + 1;
                 size *= 2;
         }
 
         table = nl_pid_hash_zalloc(size);
         if (!table)
                 return 0;
 
         otable = hash->table;
         hash->table = table;
         hash->mask = mask;
         hash->shift = shift;
         get_random_bytes(&hash->rnd, sizeof(hash->rnd));
 
         for (i = 0; i <= omask; i++) {
                 struct sock *sk;
                 struct hlist_node *node, *tmp;
 
                 sk_for_each_safe(sk, node, tmp, &otable[i])
                         __sk_add_node(sk, nl_pid_hashfn(hash, nlk_sk(sk)->pid));
         }
 
         nl_pid_hash_free(otable, osize);
         hash->rehash_time = jiffies + 10 * 60 * HZ;
         return 1;
 }
 
 static inline int nl_pid_hash_dilute(struct nl_pid_hash *hash, int len)
 {
         int avg = hash->entries >> hash->shift;
 
         if (unlikely(avg > 1) && nl_pid_hash_rehash(hash, 1))
                 return 1;
 
         if (unlikely(len > avg) && time_after(jiffies, hash->rehash_time)) {
                 nl_pid_hash_rehash(hash, 0);
                 return 1;
         }
 
         return 0;
 }
 
 static const struct proto_ops netlink_ops;
 
 static void
 netlink_update_listeners(struct sock *sk)
 {
         struct netlink_table *tbl = &nl_table[sk->sk_protocol];
         struct hlist_node *node;
         unsigned long mask;
         unsigned int i;
 
         for (i = 0; i < NLGRPLONGS(tbl->groups); i++) {
                 mask = 0;
                 sk_for_each_bound(sk, node, &tbl->mc_list) {
                         if (i < NLGRPLONGS(nlk_sk(sk)->ngroups))
                                 mask |= nlk_sk(sk)->groups[i];
                 }
                 tbl->listeners[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, struct net *net, u32 pid)
 {
         struct nl_pid_hash *hash = &nl_table[sk->sk_protocol].hash;
         struct hlist_head *head;
         int err = -EADDRINUSE;
         struct sock *osk;
         struct hlist_node *node;
         int len;
 
         netlink_table_grab();
         head = nl_pid_hashfn(hash, pid);
         len = 0;
         sk_for_each(osk, node, head) {
                 if (net_eq(sock_net(osk), net) && (nlk_sk(osk)->pid == pid))
                         break;
                 len++;
         }
         if (node)
                 goto err;
 
         err = -EBUSY;
         if (nlk_sk(sk)->pid)
                 goto err;
 
         err = -ENOMEM;
         if (BITS_PER_LONG > 32 && unlikely(hash->entries >= UINT_MAX))
                 goto err;
 
         if (len && nl_pid_hash_dilute(hash, len))
                 head = nl_pid_hashfn(hash, pid);
         hash->entries++;
         nlk_sk(sk)->pid = pid;
         sk_add_node(sk, head);
         err = 0;
 
 err:
         netlink_table_ungrab();
         return err;
 }
 
 static void netlink_remove(struct sock *sk)
 {
         netlink_table_grab();
         if (sk_del_node_init(sk))
                 nl_table[sk->sk_protocol].hash.entries--;
         if (nlk_sk(sk)->subscriptions)
                 __sk_del_bind_node(sk);
         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)
 {
         struct sock *sk;
         struct netlink_sock *nlk;
 
         sock->ops = &netlink_ops;
 
         sk = sk_alloc(net, PF_NETLINK, GFP_KERNEL, &netlink_proto);
         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);
         }
         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)
 {
         struct module *module = NULL;
         struct mutex *cb_mutex;
         struct netlink_sock *nlk;
         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;
 
         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;
         cb_mutex = nl_table[protocol].cb_mutex;
         netlink_unlock_table();
 
         err = __netlink_create(net, sock, cb_mutex, protocol);
         if (err < 0)
                 goto out_module;
 
         nlk = nlk_sk(sock->sk);
         nlk->module = module;
 out:
         return err;
 
 out_module:
         module_put(module);
         goto out;
 }
 
 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.
          */
 
         sock->sk = NULL;
         wake_up_interruptible_all(&nlk->wait);
 
         skb_queue_purge(&sk->sk_write_queue);
 
         if (nlk->pid && !nlk->subscriptions) {
                 struct netlink_notify n = {
                                                 .net = sock_net(sk),
                                                 .protocol = sk->sk_protocol,
                                                 .pid = nlk->pid,
                                           };
                 atomic_notifier_call_chain(&netlink_chain,
                                 NETLINK_URELEASE, &n);
         }
 
         module_put(nlk->module);
 
         netlink_table_grab();
         if (netlink_is_kernel(sk)) {
                 BUG_ON(nl_table[sk->sk_protocol].registered == 0);
                 if (--nl_table[sk->sk_protocol].registered == 0) {
                         kfree(nl_table[sk->sk_protocol].listeners);
                         nl_table[sk->sk_protocol].module = NULL;
                         nl_table[sk->sk_protocol].registered = 0;
                 }
         } else if (nlk->subscriptions)
                 netlink_update_listeners(sk);
         netlink_table_ungrab();
 
         kfree(nlk->groups);
         nlk->groups = NULL;
 
         sock_put(sk);
         return 0;
 }
 
 static int netlink_autobind(struct socket *sock)
 {
         struct sock *sk = sock->sk;
         struct net *net = sock_net(sk);
         struct nl_pid_hash *hash = &nl_table[sk->sk_protocol].hash;
         struct hlist_head *head;
         struct sock *osk;
         struct hlist_node *node;
         s32 pid = current->tgid;
         int err;
         static s32 rover = -4097;
 
 retry:
         cond_resched();
         netlink_table_grab();
         head = nl_pid_hashfn(hash, pid);
         sk_for_each(osk, node, head) {
                 if (!net_eq(sock_net(osk), net))
                         continue;
                 if (nlk_sk(osk)->pid == pid) {
                         /* Bind collision, search negative pid values. */
                         pid = rover--;
                         if (rover > -4097)
                                 rover = -4097;
                         netlink_table_ungrab();
                         goto retry;
                 }
         }
         netlink_table_ungrab();
 
         err = netlink_insert(sk, net, pid);
         if (err == -EADDRINUSE)
                 goto retry;
 
         /* If 2 threads race to autobind, that is fine.  */
         if (err == -EBUSY)
                 err = 0;
 
         return err;
 }
 
 static inline int netlink_capable(struct socket *sock, unsigned int flag)
 {
         return (nl_table[sock->sk->sk_protocol].nl_nonroot & flag) ||
                capable(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 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;
 
         if (nladdr->nl_family != AF_NETLINK)
                 return -EINVAL;
 
         /* Only superuser is allowed to listen multicasts */
         if (nladdr->nl_groups) {
                 if (!netlink_capable(sock, NL_NONROOT_RECV))
                         return -EPERM;
                 err = netlink_realloc_groups(sk);
                 if (err)
                         return err;
         }
 
         if (nlk->pid) {
                 if (nladdr->nl_pid != nlk->pid)
                         return -EINVAL;
         } else {
                 err = nladdr->nl_pid ?
                         netlink_insert(sk, net, nladdr->nl_pid) :
                         netlink_autobind(sock);
                 if (err)
                         return err;
         }
 
         if (!nladdr->nl_groups && (nlk->groups == NULL || !(u32)nlk->groups[0]))
                 return 0;
 
         netlink_table_grab();
         netlink_update_subscriptions(sk, nlk->subscriptions +
                                          hweight32(nladdr->nl_groups) -
                                          hweight32(nlk->groups[0]));
         nlk->groups[0] = (nlk->groups[0] & ~0xffffffffUL) | nladdr->nl_groups;
         netlink_update_listeners(sk);
         netlink_table_ungrab();
 
         return 0;
 }
 
 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 (addr->sa_family == AF_UNSPEC) {
                 sk->sk_state        = NETLINK_UNCONNECTED;
                 nlk->dst_pid        = 0;
                 nlk->dst_group  = 0;
                 return 0;
         }
         if (addr->sa_family != AF_NETLINK)
                 return -EINVAL;
 
         /* Only superuser is allowed to send multicasts */
         if (nladdr->nl_groups && !netlink_capable(sock, NL_NONROOT_SEND))
                 return -EPERM;
 
         if (!nlk->pid)
                 err = netlink_autobind(sock);
 
         if (err == 0) {
                 sk->sk_state        = NETLINK_CONNECTED;
                 nlk->dst_pid         = nladdr->nl_pid;
                 nlk->dst_group  = ffs(nladdr->nl_groups);
         }
 
         return err;
 }
 
 static int netlink_getname(struct socket *sock, struct sockaddr *addr,
                            int *addr_len, int peer)
 {
         struct sock *sk = sock->sk;
         struct netlink_sock *nlk = nlk_sk(sk);
         struct sockaddr_nl *nladdr = (struct sockaddr_nl *)addr;
 
         nladdr->nl_family = AF_NETLINK;
         nladdr->nl_pad = 0;
         *addr_len = sizeof(*nladdr);
 
         if (peer) {
                 nladdr->nl_pid = nlk->dst_pid;
                 nladdr->nl_groups = netlink_group_mask(nlk->dst_group);
         } else {
                 nladdr->nl_pid = nlk->pid;
                 nladdr->nl_groups = nlk->groups ? nlk->groups[0] : 0;
         }
         return 0;
 }
 
 static void netlink_overrun(struct sock *sk)
 {
         if (!test_and_set_bit(0, &nlk_sk(sk)->state)) {
                 sk->sk_err = ENOBUFS;
                 sk->sk_error_report(sk);
         }
 }
 
 static struct sock *netlink_getsockbypid(struct sock *ssk, u32 pid)
 {
         struct sock *sock;
         struct netlink_sock *nlk;
 
         sock = netlink_lookup(sock_net(ssk), ssk->sk_protocol, pid);
         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_pid != nlk_sk(ssk)->pid) {
                 sock_put(sock);
                 return ERR_PTR(-ECONNREFUSED);
         }
         return sock;
 }
 
 struct sock *netlink_getsockbyfilp(struct file *filp)
 {
         struct inode *inode = filp->f_path.dentry->d_inode;
         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;
 }
 
 /*
  * 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(0, &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(0, &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;
         }
         skb_set_owner_r(skb, sk);
         return 0;
 }
 
 int netlink_sendskb(struct sock *sk, struct sk_buff *skb)
 {
         int len = skb->len;
 
         skb_queue_tail(&sk->sk_receive_queue, skb);
         sk->sk_data_ready(sk, len);
         sock_put(sk);
         return len;
 }
 
 void netlink_detachskb(struct sock *sk, struct sk_buff *skb)
 {
         kfree_skb(skb);
         sock_put(sk);
 }
 
 static inline struct sk_buff *netlink_trim(struct sk_buff *skb,
                                            gfp_t allocation)
 {
         int delta;
 
         skb_orphan(skb);
 
         delta = skb->end - skb->tail;
         if (delta * 2 < skb->truesize)
                 return skb;
 
         if (skb_shared(skb)) {
                 struct sk_buff *nskb = skb_clone(skb, allocation);
                 if (!nskb)
                         return skb;
                 kfree_skb(skb);
                 skb = nskb;
         }
 
         if (!pskb_expand_head(skb, 0, -delta, allocation))
                 skb->truesize -= delta;
 
         return skb;
 }
 
 static inline void netlink_rcv_wake(struct sock *sk)
 {
         struct netlink_sock *nlk = nlk_sk(sk);
 
         if (skb_queue_empty(&sk->sk_receive_queue))
                 clear_bit(0, &nlk->state);
         if (!test_bit(0, &nlk->state))
                 wake_up_interruptible(&nlk->wait);
 }
 
 static inline int netlink_unicast_kernel(struct sock *sk, struct sk_buff *skb)
 {
         int ret;
         struct netlink_sock *nlk = nlk_sk(sk);
 
         ret = -ECONNREFUSED;
         if (nlk->netlink_rcv != NULL) {
                 ret = skb->len;
                 skb_set_owner_r(skb, sk);
                 nlk->netlink_rcv(skb);
         }
         kfree_skb(skb);
         sock_put(sk);
         return ret;
 }
 
 int netlink_unicast(struct sock *ssk, struct sk_buff *skb,
                     u32 pid, int nonblock)
 {
         struct sock *sk;
         int err;
         long timeo;
 
         skb = netlink_trim(skb, gfp_any());
 
         timeo = sock_sndtimeo(ssk, nonblock);
 retry:
         sk = netlink_getsockbypid(ssk, pid);
         if (IS_ERR(sk)) {
                 kfree_skb(skb);
                 return PTR_ERR(sk);
         }
         if (netlink_is_kernel(sk))
                 return netlink_unicast_kernel(sk, skb);
 
         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;
         unsigned long *listeners;
 
         BUG_ON(!netlink_is_kernel(sk));
 
         rcu_read_lock();
         listeners = rcu_dereference(nl_table[sk->sk_protocol].listeners);
 
         if (group - 1 < nl_table[sk->sk_protocol].groups)
                 res = test_bit(group - 1, listeners);
 
         rcu_read_unlock();
 
         return res;
 }
 EXPORT_SYMBOL_GPL(netlink_has_listeners);
 
 static inline 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(0, &nlk->state)) {
                 skb_set_owner_r(skb, sk);
                 skb_queue_tail(&sk->sk_receive_queue, skb);
                 sk->sk_data_ready(sk, skb->len);
                 return atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf;
         }
         return -1;
 }
 
 struct netlink_broadcast_data {
         struct sock *exclude_sk;
         struct net *net;
         u32 pid;
         u32 group;
         int failure;
         int congested;
         int delivered;
         gfp_t allocation;
         struct sk_buff *skb, *skb2;
 };
 
 static inline int 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)
                 goto out;
 
         if (nlk->pid == p->pid || p->group - 1 >= nlk->ngroups ||
             !test_bit(p->group - 1, nlk->groups))
                 goto out;
 
         if (!net_eq(sock_net(sk), p->net))
                 goto out;
 
         if (p->failure) {
                 netlink_overrun(sk);
                 goto out;
         }
 
         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;
         } else if (sk_filter(sk, p->skb2)) {
                 kfree_skb(p->skb2);
                 p->skb2 = NULL;
         } else if ((val = netlink_broadcast_deliver(sk, p->skb2)) < 0) {
                 netlink_overrun(sk);
         } else {
                 p->congested |= val;
                 p->delivered = 1;
                 p->skb2 = NULL;
         }
        sock_put(sk);

out:
        return 0;
}

int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 pid,
                      u32 group, gfp_t allocation)
{
        struct net *net = sock_net(ssk);
        struct netlink_broadcast_data info;
        struct hlist_node *node;
        struct sock *sk;

        skb = netlink_trim(skb, allocation);

        info.exclude_sk = ssk;
        info.net = net;
        info.pid = pid;
        info.group = group;
        info.failure = 0;
        info.congested = 0;
        info.delivered = 0;
        info.allocation = allocation;
        info.skb = skb;
        info.skb2 = NULL;

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

        netlink_lock_table();

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

        kfree_skb(skb);

        netlink_unlock_table();

        if (info.skb2)
                kfree_skb(info.skb2);

        if (info.delivered) {
                if (info.congested && (allocation & __GFP_WAIT))
                        yield();
                return 0;
        }
        if (info.failure)
                return -ENOBUFS;
        return -ESRCH;
}
EXPORT_SYMBOL(netlink_broadcast);

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

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

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

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

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

        sk->sk_err = p->code;
        sk->sk_error_report(sk);
out:
        return 0;
}

void netlink_set_err(struct sock *ssk, u32 pid, u32 group, int code)
{
        struct netlink_set_err_data info;
        struct hlist_node *node;
        struct sock *sk;

        info.exclude_sk = ssk;
        info.pid = pid;
        info.group = group;
        info.code = code;

        read_lock(&nl_table_lock);

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

        read_unlock(&nl_table_lock);
}

/* 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, 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_RECV_PKTINFO;
                else
                        nlk->flags &= ~NETLINK_RECV_PKTINFO;
                err = 0;
                break;
        case NETLINK_ADD_MEMBERSHIP:
        case NETLINK_DROP_MEMBERSHIP: {
                if (!netlink_capable(sock, NL_NONROOT_RECV))
                        return -EPERM;
                err = netlink_realloc_groups(sk);
                if (err)
                        return err;
                if (!val || val - 1 >= nlk->ngroups)
                        return -EINVAL;
                netlink_table_grab();
                netlink_update_socket_mc(nlk, val,
                                         optname == NETLINK_ADD_MEMBERSHIP);
                netlink_table_ungrab();
                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_RECV_PKTINFO ? 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 int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
                           struct msghdr *msg, size_t len)
{
        struct sock_iocb *siocb = kiocb_to_siocb(kiocb);
        struct sock *sk = sock->sk;
        struct netlink_sock *nlk = nlk_sk(sk);
        struct sockaddr_nl *addr = msg->msg_name;
        u32 dst_pid;
        u32 dst_group;
        struct sk_buff *skb;
        int err;
        struct scm_cookie scm;

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

        if (NULL == siocb->scm)
                siocb->scm = &scm;
        err = scm_send(sock, msg, siocb->scm);
        if (err < 0)
                return err;

        if (msg->msg_namelen) {
                if (addr->nl_family != AF_NETLINK)
                        return -EINVAL;
                dst_pid = addr->nl_pid;
                dst_group = ffs(addr->nl_groups);
                if (dst_group && !netlink_capable(sock, NL_NONROOT_SEND))
                        return -EPERM;
        } else {
                dst_pid = nlk->dst_pid;
                dst_group = nlk->dst_group;
        }

        if (!nlk->pid) {
                err = netlink_autobind(sock);
                if (err)
                        goto out;
        }

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

        NETLINK_CB(skb).pid        = nlk->pid;
        NETLINK_CB(skb).dst_group = dst_group;
        NETLINK_CB(skb).loginuid = audit_get_loginuid(current);
        NETLINK_CB(skb).sessionid = audit_get_sessionid(current);
        security_task_getsecid(current, &(NETLINK_CB(skb).sid));
        memcpy(NETLINK_CREDS(skb), &siocb->scm->creds, sizeof(struct ucred));

        /* What can I do? Netlink is asynchronous, so that
           we will have to save current capabilities to
           check them, when this message will be delivered
           to corresponding kernel module.   --ANK (980802)
         */

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

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

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

out:
        return err;
}

static int netlink_recvmsg(struct kiocb *kiocb, struct socket *sock,
                           struct msghdr *msg, size_t len,
                           int flags)
{
        struct sock_iocb *siocb = kiocb_to_siocb(kiocb);
        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;
        int err;

        if (flags&MSG_OOB)
                return -EOPNOTSUPP;

        copied = 0;

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

        msg->msg_namelen = 0;

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

        skb_reset_transport_header(skb);
        err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);

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

        if (nlk->flags & NETLINK_RECV_PKTINFO)
                netlink_cmsg_recv_pktinfo(msg, skb);

        if (NULL == siocb->scm) {
                memset(&scm, 0, sizeof(scm));
                siocb->scm = &scm;
        }
        siocb->scm->creds = *NETLINK_CREDS(skb);
        if (flags & MSG_TRUNC)
                copied = skb->len;
        skb_free_datagram(sk, skb);

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

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

static void netlink_data_ready(struct sock *sk, int len)
{
        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, unsigned int groups,
                      void (*input)(struct sk_buff *skb),
                      struct mutex *cb_mutex, struct module *module)
{
        struct socket *sock;
        struct sock *sk;
        struct netlink_sock *nlk;
        unsigned long *listeners = NULL;

        BUG_ON(!nl_table);

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

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

        /*
         * We have to just have a reference on the net from sk, but don't
         * get_net it. Besides, we cannot get and then put the net here.
         * So we create one inside init_net and the move it to net.
         */

        if (__netlink_create(&init_net, sock, cb_mutex, unit) < 0)
                goto out_sock_release_nosk;

        sk = sock->sk;
        sk_change_net(sk, net);

        if (groups < 32)
                groups = 32;

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

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

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

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

        netlink_table_grab();
        if (!nl_table[unit].registered) {
                nl_table[unit].groups = groups;
                nl_table[unit].listeners = listeners;
                nl_table[unit].cb_mutex = cb_mutex;
                nl_table[unit].module = module;
                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)
{
        sk_release_kernel(sk);
}
EXPORT_SYMBOL(netlink_kernel_release);


/**
 * 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)
{
        unsigned long *listeners, *old = NULL;
        struct netlink_table *tbl = &nl_table[sk->sk_protocol];
        int err = 0;

        if (groups < 32)
                groups = 32;

        netlink_table_grab();
        if (NLGRPSZ(tbl->groups) < NLGRPSZ(groups)) {
                listeners = kzalloc(NLGRPSZ(groups), GFP_ATOMIC);
                if (!listeners) {
                        err = -ENOMEM;
                        goto out_ungrab;
                }
                old = tbl->listeners;
                memcpy(listeners, old, NLGRPSZ(tbl->groups));
                rcu_assign_pointer(tbl->listeners, listeners);
        }
        tbl->groups = groups;

 out_ungrab:
        netlink_table_ungrab();
        synchronize_rcu();
        kfree(old);
        return err;
}
EXPORT_SYMBOL(netlink_change_ngroups);

/**
 * netlink_clear_multicast_users - kick off multicast listeners
 *
 * This function removes all listeners from the given group.
 * @ksk: The kernel netlink socket, as returned by
 *        netlink_kernel_create().
 * @group: The multicast group to clear.
 */
void netlink_clear_multicast_users(struct sock *ksk, unsigned int group)
{
        struct sock *sk;
        struct hlist_node *node;
        struct netlink_table *tbl = &nl_table[ksk->sk_protocol];

        netlink_table_grab();

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

        netlink_table_ungrab();
}
EXPORT_SYMBOL(netlink_clear_multicast_users);

void netlink_set_nonroot(int protocol, unsigned int flags)
{
        if ((unsigned int)protocol < MAX_LINKS)
                nl_table[protocol].nl_nonroot = flags;
}
EXPORT_SYMBOL(netlink_set_nonroot);

static void netlink_destroy_callback(struct netlink_callback *cb)
{
        if (cb->skb)
                kfree_skb(cb->skb);
        kfree(cb);
}

/*
 * 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_callback *cb;
        struct sk_buff *skb;
        struct nlmsghdr *nlh;
        int len, err = -ENOBUFS;

        skb = sock_rmalloc(sk, NLMSG_GOODSIZE, 0, GFP_KERNEL);
        if (!skb)
                goto errout;

        mutex_lock(nlk->cb_mutex);

        cb = nlk->cb;
        if (cb == NULL) {
                err = -EINVAL;
                goto errout_skb;
        }

        len = cb->dump(skb, cb);

        if (len > 0) {
                mutex_unlock(nlk->cb_mutex);

                if (sk_filter(sk, skb))
                        kfree_skb(skb);
                else {
                        skb_queue_tail(&sk->sk_receive_queue, skb);
                        sk->sk_data_ready(sk, skb->len);
                }
                return 0;
        }

        nlh = nlmsg_put_answer(skb, cb, NLMSG_DONE, sizeof(len), NLM_F_MULTI);
        if (!nlh)
                goto errout_skb;

        memcpy(nlmsg_data(nlh), &len, sizeof(len));

        if (sk_filter(sk, skb))
                kfree_skb(skb);
        else {
                skb_queue_tail(&sk->sk_receive_queue, skb);
                sk->sk_data_ready(sk, skb->len);
        }

        if (cb->done)
                cb->done(cb);
        nlk->cb = NULL;
        mutex_unlock(nlk->cb_mutex);

        netlink_destroy_callback(cb);
        return 0;

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

int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
                       struct nlmsghdr *nlh,
                       int (*dump)(struct sk_buff *skb,
                                   struct netlink_callback *),
                       int (*done)(struct netlink_callback *))
{
        struct netlink_callback *cb;
        struct sock *sk;
        struct netlink_sock *nlk;

        cb = kzalloc(sizeof(*cb), GFP_KERNEL);
        if (cb == NULL)
                return -ENOBUFS;

        cb->dump = dump;
        cb->done = done;
        cb->nlh = nlh;
        atomic_inc(&skb->users);
        cb->skb = skb;

        sk = netlink_lookup(sock_net(ssk), ssk->sk_protocol, NETLINK_CB(skb).pid);
        if (sk == NULL) {
                netlink_destroy_callback(cb);
                return -ECONNREFUSED;
        }
        nlk = nlk_sk(sk);
        /* A dump is in progress... */
        mutex_lock(nlk->cb_mutex);
        if (nlk->cb) {
                mutex_unlock(nlk->cb_mutex);
                netlink_destroy_callback(cb);
                sock_put(sk);
                return -EBUSY;
        }
        nlk->cb = cb;
        mutex_unlock(nlk->cb_mutex);

        netlink_dump(sk);
        sock_put(sk);

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

void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
{
        struct sk_buff *skb;
        struct nlmsghdr *rep;
        struct nlmsgerr *errmsg;
        size_t payload = sizeof(*errmsg);

        /* error messages get the original request appened */
        if (err)
                payload += nlmsg_len(nlh);

        skb = nlmsg_new(payload, GFP_KERNEL);
        if (!skb) {
                struct sock *sk;

                sk = netlink_lookup(sock_net(in_skb->sk),
                                    in_skb->sk->sk_protocol,
                                    NETLINK_CB(in_skb).pid);
                if (sk) {
                        sk->sk_err = ENOBUFS;
                        sk->sk_error_report(sk);
                        sock_put(sk);
                }
                return;
        }

        rep = __nlmsg_put(skb, NETLINK_CB(in_skb).pid, nlh->nlmsg_seq,
                          NLMSG_ERROR, sizeof(struct nlmsgerr), 0);
        errmsg = nlmsg_data(rep);
        errmsg->error = err;
        memcpy(&errmsg->msg, nlh, err ? nlh->nlmsg_len : sizeof(*nlh));
        netlink_unicast(in_skb->sk, skb, NETLINK_CB(in_skb).pid, MSG_DONTWAIT);
}
EXPORT_SYMBOL(netlink_ack);

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

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

                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);
                if (err == -EINTR)
                        goto skip;

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

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
 * @pid: destination netlink pid 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 pid,
                 unsigned int group, int report, gfp_t flags)
{
        int err = 0;

        if (group) {
                int exclude_pid = 0;

                if (report) {
                        atomic_inc(&skb->users);
                        exclude_pid = pid;
                }

                /* errors reported via destination sk->sk_err */
                nlmsg_multicast(sk, skb, exclude_pid, group, flags);
        }

        if (report)
                err = nlmsg_unicast(sk, skb, pid);

        return err;
}
EXPORT_SYMBOL(nlmsg_notify);

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

static struct sock *netlink_seq_socket_idx(struct seq_file *seq, loff_t pos)
{
        struct nl_seq_iter *iter = seq->private;
        int i, j;
        struct sock *s;
        struct hlist_node *node;
        loff_t off = 0;

        for (i = 0; i < MAX_LINKS; i++) {
                struct nl_pid_hash *hash = &nl_table[i].hash;

                for (j = 0; j <= hash->mask; j++) {
                        sk_for_each(s, node, &hash->table[j]) {
                                if (sock_net(s) != seq_file_net(seq))
                                        continue;
                                if (off == pos) {
                                        iter->link = i;
                                        iter->hash_idx = j;
                                        return s;
                                }
                                ++off;
                        }
                }
        }
        return NULL;
}

static void *netlink_seq_start(struct seq_file *seq, loff_t *pos)
        __acquires(nl_table_lock)
{
        read_lock(&nl_table_lock);
        return *pos ? netlink_seq_socket_idx(seq, *pos - 1) : SEQ_START_TOKEN;
}

static void *netlink_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct sock *s;
        struct nl_seq_iter *iter;
        int i, j;

        ++*pos;

        if (v == SEQ_START_TOKEN)
                return netlink_seq_socket_idx(seq, 0);

        iter = seq->private;
        s = v;
        do {
                s = sk_next(s);
        } while (s && sock_net(s) != seq_file_net(seq));
        if (s)
                return s;

        i = iter->link;
        j = iter->hash_idx + 1;

        do {
                struct nl_pid_hash *hash = &nl_table[i].hash;

                for (; j <= hash->mask; j++) {
                        s = sk_head(&hash->table[j]);
                        while (s && sock_net(s) != seq_file_net(seq))
                                s = sk_next(s);
                        if (s) {
                                iter->link = i;
                                iter->hash_idx = j;
                                return s;
                        }
                }

                j = 0;
        } while (++i < MAX_LINKS);

        return NULL;
}

static void netlink_seq_stop(struct seq_file *seq, void *v)
        __releases(nl_table_lock)
{
        read_unlock(&nl_table_lock);
}


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\n");
        else {
                struct sock *s = v;
                struct netlink_sock *nlk = nlk_sk(s);

                seq_printf(seq, "%p %-3d %-6d %08x %-8d %-8d %p %d\n",
                           s,
                           s->sk_protocol,
                           nlk->pid,
                           nlk->groups ? (u32)nlk->groups[0] : 0,
                           atomic_read(&s->sk_rmem_alloc),
                           atomic_read(&s->sk_wmem_alloc),
                           nlk->cb,
                           atomic_read(&s->sk_refcnt)
                        );

        }
        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,
};


static int netlink_seq_open(struct inode *inode, struct file *file)
{
        return seq_open_net(inode, file, &netlink_seq_ops,
                                sizeof(struct nl_seq_iter));
}

static const struct file_operations netlink_seq_fops = {
        .owner                = THIS_MODULE,
        .open                = netlink_seq_open,
        .read                = seq_read,
        .llseek                = seq_lseek,
        .release        = seq_release_net,
};

#endif

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

int netlink_unregister_notifier(struct notifier_block *nb)
{
        return atomic_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 =        sock_no_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 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_net_fops_create(net, "netlink", 0, &netlink_seq_fops))
                return -ENOMEM;
#endif
        return 0;
}

static void __net_exit netlink_net_exit(struct net *net)
{
#ifdef CONFIG_PROC_FS
        proc_net_remove(net, "netlink");
#endif
}

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

static int __init netlink_proto_init(void)
{
        struct sk_buff *dummy_skb;
        int i;
        unsigned long limit;
        unsigned int order;
        int err = proto_register(&netlink_proto, 0);

        if (err != 0)
                goto out;

        BUILD_BUG_ON(sizeof(struct netlink_skb_parms) > sizeof(dummy_skb->cb));

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

        if (num_physpages >= (128 * 1024))
                limit = num_physpages >> (21 - PAGE_SHIFT);
        else
                limit = num_physpages >> (23 - PAGE_SHIFT);

        order = get_bitmask_order(limit) - 1 + PAGE_SHIFT;
        limit = (1UL << order) / sizeof(struct hlist_head);
        order = get_bitmask_order(min(limit, (unsigned long)UINT_MAX)) - 1;

        for (i = 0; i < MAX_LINKS; i++) {
                struct nl_pid_hash *hash = &nl_table[i].hash;

                hash->table = nl_pid_hash_zalloc(1 * sizeof(*hash->table));
                if (!hash->table) {
                        while (i-- > 0)
                                nl_pid_hash_free(nl_table[i].hash.table,
                                                 1 * sizeof(*hash->table));
                        kfree(nl_table);
                        goto panic;
                }
                hash->max_shift = order;
                hash->shift = 0;
                hash->mask = 0;
                hash->rehash_time = jiffies;
        }

        sock_register(&netlink_family_ops);
        register_pernet_subsys(&netlink_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);