/*
   * File: socket.c
   *
   * Phonet sockets
   *
   * Copyright (C) 2008 Nokia Corporation.
   *

   * Authors: Sakari Ailus <sakari.ailus@nokia.com>
   *          Rémi Denis-Courmont

   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * version 2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
   * 02110-1301 USA
   */

  #include <linux/gfp.h>

  #include <linux/kernel.h>
  #include <linux/net.h>

  #include <linux/poll.h>

  #include <linux/sched/signal.h>

  #include <net/sock.h>
  #include <net/tcp_states.h>
  
  #include <linux/phonet.h>

  #include <linux/export.h>

  #include <net/phonet/phonet.h>

  #include <net/phonet/pep.h>

  #include <net/phonet/pn_dev.h>
  
  static int pn_socket_release(struct socket *sock)
  {
  	struct sock *sk = sock->sk;
  
  	if (sk) {
  		sock->sk = NULL;
  		sk->sk_prot->close(sk, 0);
  	}
  	return 0;
  }

  #define PN_HASHSIZE	16
  #define PN_HASHMASK	(PN_HASHSIZE-1)

  static struct  {

  	struct hlist_head hlist[PN_HASHSIZE];

  	struct mutex lock;

  } pnsocks;
  
  void __init pn_sock_init(void)
  {

  	unsigned int i;

  
  	for (i = 0; i < PN_HASHSIZE; i++)
  		INIT_HLIST_HEAD(pnsocks.hlist + i);

  	mutex_init(&pnsocks.lock);

  }
  
  static struct hlist_head *pn_hash_list(u16 obj)
  {
  	return pnsocks.hlist + (obj & PN_HASHMASK);
  }

  
  /*
   * Find address based on socket address, match only certain fields.
   * Also grab sock if it was found. Remember to sock_put it later.
   */

  struct sock *pn_find_sock_by_sa(struct net *net, const struct sockaddr_pn *spn)

  {

  	struct sock *sknode;
  	struct sock *rval = NULL;
  	u16 obj = pn_sockaddr_get_object(spn);
  	u8 res = spn->spn_resource;

  	struct hlist_head *hlist = pn_hash_list(obj);

  	rcu_read_lock();

  	sk_for_each_rcu(sknode, hlist) {

  		struct pn_sock *pn = pn_sk(sknode);
  		BUG_ON(!pn->sobject); /* unbound socket */

  		if (!net_eq(sock_net(sknode), net))
  			continue;

  		if (pn_port(obj)) {
  			/* Look up socket by port */
  			if (pn_port(pn->sobject) != pn_port(obj))
  				continue;
  		} else {
  			/* If port is zero, look up by resource */
  			if (pn->resource != res)
  				continue;
  		}

  		if (pn_addr(pn->sobject) &&
  		    pn_addr(pn->sobject) != pn_addr(obj))

  			continue;
  
  		rval = sknode;
  		sock_hold(sknode);
  		break;
  	}

  	rcu_read_unlock();

  
  	return rval;

  }
  
  /* Deliver a broadcast packet (only in bottom-half) */
  void pn_deliver_sock_broadcast(struct net *net, struct sk_buff *skb)
  {

  	struct hlist_head *hlist = pnsocks.hlist;

  	unsigned int h;

  	rcu_read_lock();

  	for (h = 0; h < PN_HASHSIZE; h++) {

  		struct sock *sknode;

  		sk_for_each(sknode, hlist) {

  			struct sk_buff *clone;

  			if (!net_eq(sock_net(sknode), net))
  				continue;
  			if (!sock_flag(sknode, SOCK_BROADCAST))
  				continue;
  
  			clone = skb_clone(skb, GFP_ATOMIC);
  			if (clone) {
  				sock_hold(sknode);
  				sk_receive_skb(sknode, clone, 0);
  			}

  		}

  		hlist++;

  	}

  	rcu_read_unlock();

  }

  int pn_sock_hash(struct sock *sk)

  {

  	struct hlist_head *hlist = pn_hash_list(pn_sk(sk)->sobject);

  	mutex_lock(&pnsocks.lock);
  	sk_add_node_rcu(sk, hlist);
  	mutex_unlock(&pnsocks.lock);

  
  	return 0;

  }
  EXPORT_SYMBOL(pn_sock_hash);
  
  void pn_sock_unhash(struct sock *sk)
  {

  	mutex_lock(&pnsocks.lock);
  	sk_del_node_init_rcu(sk);
  	mutex_unlock(&pnsocks.lock);

  	pn_sock_unbind_all_res(sk);

  	synchronize_rcu();

  }
  EXPORT_SYMBOL(pn_sock_unhash);

  static DEFINE_MUTEX(port_mutex);

  static int pn_socket_bind(struct socket *sock, struct sockaddr *addr, int len)
  {
  	struct sock *sk = sock->sk;
  	struct pn_sock *pn = pn_sk(sk);
  	struct sockaddr_pn *spn = (struct sockaddr_pn *)addr;
  	int err;
  	u16 handle;
  	u8 saddr;
  
  	if (sk->sk_prot->bind)
  		return sk->sk_prot->bind(sk, addr, len);
  
  	if (len < sizeof(struct sockaddr_pn))
  		return -EINVAL;
  	if (spn->spn_family != AF_PHONET)
  		return -EAFNOSUPPORT;
  
  	handle = pn_sockaddr_get_object((struct sockaddr_pn *)addr);
  	saddr = pn_addr(handle);

  	if (saddr && phonet_address_lookup(sock_net(sk), saddr))

  		return -EADDRNOTAVAIL;
  
  	lock_sock(sk);
  	if (sk->sk_state != TCP_CLOSE || pn_port(pn->sobject)) {
  		err = -EINVAL; /* attempt to rebind */
  		goto out;
  	}

  	WARN_ON(sk_hashed(sk));
  	mutex_lock(&port_mutex);

  	err = sk->sk_prot->get_port(sk, pn_port(handle));
  	if (err)

  		goto out_port;

  
  	/* get_port() sets the port, bind() sets the address if applicable */
  	pn->sobject = pn_object(saddr, pn_port(pn->sobject));
  	pn->resource = spn->spn_resource;
  
  	/* Enable RX on the socket */

  	err = sk->sk_prot->hash(sk);

  out_port:
  	mutex_unlock(&port_mutex);

  out:
  	release_sock(sk);
  	return err;
  }
  
  static int pn_socket_autobind(struct socket *sock)
  {
  	struct sockaddr_pn sa;
  	int err;
  
  	memset(&sa, 0, sizeof(sa));
  	sa.spn_family = AF_PHONET;
  	err = pn_socket_bind(sock, (struct sockaddr *)&sa,
  				sizeof(struct sockaddr_pn));
  	if (err != -EINVAL)
  		return err;
  	BUG_ON(!pn_port(pn_sk(sock->sk)->sobject));
  	return 0; /* socket was already bound */
  }

  static int pn_socket_connect(struct socket *sock, struct sockaddr *addr,
  		int len, int flags)
  {
  	struct sock *sk = sock->sk;

  	struct pn_sock *pn = pn_sk(sk);

  	struct sockaddr_pn *spn = (struct sockaddr_pn *)addr;

  	struct task_struct *tsk = current;
  	long timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);

  	int err;

  	if (pn_socket_autobind(sock))
  		return -ENOBUFS;

  	if (len < sizeof(struct sockaddr_pn))
  		return -EINVAL;
  	if (spn->spn_family != AF_PHONET)
  		return -EAFNOSUPPORT;
  
  	lock_sock(sk);
  
  	switch (sock->state) {
  	case SS_UNCONNECTED:

  		if (sk->sk_state != TCP_CLOSE) {

  			err = -EISCONN;
  			goto out;

  		}
  		break;

  	case SS_CONNECTING:
  		err = -EALREADY;
  		goto out;
  	default:
  		err = -EISCONN;
  		goto out;

  	}

  	pn->dobject = pn_sockaddr_get_object(spn);
  	pn->resource = pn_sockaddr_get_resource(spn);

  	sock->state = SS_CONNECTING;

  	err = sk->sk_prot->connect(sk, addr, len);

  	if (err) {

  		sock->state = SS_UNCONNECTED;

  		pn->dobject = 0;

  		goto out;
  	}

  	while (sk->sk_state == TCP_SYN_SENT) {
  		DEFINE_WAIT(wait);

  		if (!timeo) {
  			err = -EINPROGRESS;
  			goto out;
  		}
  		if (signal_pending(tsk)) {
  			err = sock_intr_errno(timeo);
  			goto out;
  		}

  		prepare_to_wait_exclusive(sk_sleep(sk), &wait,
  						TASK_INTERRUPTIBLE);
  		release_sock(sk);
  		timeo = schedule_timeout(timeo);
  		lock_sock(sk);
  		finish_wait(sk_sleep(sk), &wait);

  	}

  	if ((1 << sk->sk_state) & (TCPF_SYN_RECV|TCPF_ESTABLISHED))
  		err = 0;
  	else if (sk->sk_state == TCP_CLOSE_WAIT)
  		err = -ECONNRESET;
  	else
  		err = -ECONNREFUSED;
  	sock->state = err ? SS_UNCONNECTED : SS_CONNECTED;

  out:
  	release_sock(sk);
  	return err;
  }

  static int pn_socket_accept(struct socket *sock, struct socket *newsock,

  			    int flags, bool kern)

  {
  	struct sock *sk = sock->sk;
  	struct sock *newsk;
  	int err;

  	if (unlikely(sk->sk_state != TCP_LISTEN))
  		return -EINVAL;

  	newsk = sk->sk_prot->accept(sk, flags, &err, kern);

  	if (!newsk)
  		return err;
  
  	lock_sock(newsk);
  	sock_graft(newsk, newsock);
  	newsock->state = SS_CONNECTED;
  	release_sock(newsk);
  	return 0;
  }

  static int pn_socket_getname(struct socket *sock, struct sockaddr *addr,
  				int *sockaddr_len, int peer)
  {
  	struct sock *sk = sock->sk;
  	struct pn_sock *pn = pn_sk(sk);
  
  	memset(addr, 0, sizeof(struct sockaddr_pn));
  	addr->sa_family = AF_PHONET;
  	if (!peer) /* Race with bind() here is userland's problem. */
  		pn_sockaddr_set_object((struct sockaddr_pn *)addr,
  					pn->sobject);
  
  	*sockaddr_len = sizeof(struct sockaddr_pn);
  	return 0;
  }

  static unsigned int pn_socket_poll(struct file *file, struct socket *sock,
  					poll_table *wait)
  {
  	struct sock *sk = sock->sk;
  	struct pep_sock *pn = pep_sk(sk);
  	unsigned int mask = 0;

  	poll_wait(file, sk_sleep(sk), wait);

  	if (sk->sk_state == TCP_CLOSE)

  		return POLLERR;

  	if (!skb_queue_empty(&sk->sk_receive_queue))
  		mask |= POLLIN | POLLRDNORM;

  	if (!skb_queue_empty(&pn->ctrlreq_queue))
  		mask |= POLLPRI;
  	if (!mask && sk->sk_state == TCP_CLOSE_WAIT)

  		return POLLHUP;

  	if (sk->sk_state == TCP_ESTABLISHED &&

  		refcount_read(&sk->sk_wmem_alloc) < sk->sk_sndbuf &&

  		atomic_read(&pn->tx_credits))

  		mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
  
  	return mask;
  }

  static int pn_socket_ioctl(struct socket *sock, unsigned int cmd,
  				unsigned long arg)
  {
  	struct sock *sk = sock->sk;
  	struct pn_sock *pn = pn_sk(sk);
  
  	if (cmd == SIOCPNGETOBJECT) {
  		struct net_device *dev;
  		u16 handle;
  		u8 saddr;
  
  		if (get_user(handle, (__u16 __user *)arg))
  			return -EFAULT;
  
  		lock_sock(sk);
  		if (sk->sk_bound_dev_if)
  			dev = dev_get_by_index(sock_net(sk),
  						sk->sk_bound_dev_if);
  		else
  			dev = phonet_device_get(sock_net(sk));
  		if (dev && (dev->flags & IFF_UP))
  			saddr = phonet_address_get(dev, pn_addr(handle));
  		else
  			saddr = PN_NO_ADDR;
  		release_sock(sk);
  
  		if (dev)
  			dev_put(dev);
  		if (saddr == PN_NO_ADDR)
  			return -EHOSTUNREACH;
  
  		handle = pn_object(saddr, pn_port(pn->sobject));
  		return put_user(handle, (__u16 __user *)arg);
  	}
  
  	return sk->sk_prot->ioctl(sk, cmd, arg);
  }

  static int pn_socket_listen(struct socket *sock, int backlog)
  {
  	struct sock *sk = sock->sk;
  	int err = 0;

  	if (pn_socket_autobind(sock))
  		return -ENOBUFS;
  
  	lock_sock(sk);

  	if (sock->state != SS_UNCONNECTED) {

  		err = -EINVAL;
  		goto out;
  	}

  	if (sk->sk_state != TCP_LISTEN) {
  		sk->sk_state = TCP_LISTEN;
  		sk->sk_ack_backlog = 0;
  	}

  	sk->sk_max_ack_backlog = backlog;
  out:
  	release_sock(sk);
  	return err;
  }

  static int pn_socket_sendmsg(struct socket *sock, struct msghdr *m,
  			     size_t total_len)

  {
  	struct sock *sk = sock->sk;
  
  	if (pn_socket_autobind(sock))
  		return -EAGAIN;

  	return sk->sk_prot->sendmsg(sk, m, total_len);

  }
  
  const struct proto_ops phonet_dgram_ops = {
  	.family		= AF_PHONET,
  	.owner		= THIS_MODULE,
  	.release	= pn_socket_release,
  	.bind		= pn_socket_bind,
  	.connect	= sock_no_connect,
  	.socketpair	= sock_no_socketpair,
  	.accept		= sock_no_accept,
  	.getname	= pn_socket_getname,
  	.poll		= datagram_poll,
  	.ioctl		= pn_socket_ioctl,
  	.listen		= sock_no_listen,
  	.shutdown	= sock_no_shutdown,
  	.setsockopt	= sock_no_setsockopt,
  	.getsockopt	= sock_no_getsockopt,
  #ifdef CONFIG_COMPAT
  	.compat_setsockopt = sock_no_setsockopt,
  	.compat_getsockopt = sock_no_getsockopt,
  #endif
  	.sendmsg	= pn_socket_sendmsg,
  	.recvmsg	= sock_common_recvmsg,
  	.mmap		= sock_no_mmap,
  	.sendpage	= sock_no_sendpage,
  };

  const struct proto_ops phonet_stream_ops = {
  	.family		= AF_PHONET,
  	.owner		= THIS_MODULE,
  	.release	= pn_socket_release,
  	.bind		= pn_socket_bind,

  	.connect	= pn_socket_connect,

  	.socketpair	= sock_no_socketpair,
  	.accept		= pn_socket_accept,
  	.getname	= pn_socket_getname,
  	.poll		= pn_socket_poll,
  	.ioctl		= pn_socket_ioctl,
  	.listen		= pn_socket_listen,
  	.shutdown	= sock_no_shutdown,

  	.setsockopt	= sock_common_setsockopt,
  	.getsockopt	= sock_common_getsockopt,

  #ifdef CONFIG_COMPAT

  	.compat_setsockopt = compat_sock_common_setsockopt,
  	.compat_getsockopt = compat_sock_common_getsockopt,

  #endif
  	.sendmsg	= pn_socket_sendmsg,
  	.recvmsg	= sock_common_recvmsg,
  	.mmap		= sock_no_mmap,
  	.sendpage	= sock_no_sendpage,
  };
  EXPORT_SYMBOL(phonet_stream_ops);

  /* allocate port for a socket */
  int pn_sock_get_port(struct sock *sk, unsigned short sport)
  {
  	static int port_cur;

  	struct net *net = sock_net(sk);

  	struct pn_sock *pn = pn_sk(sk);
  	struct sockaddr_pn try_sa;
  	struct sock *tmpsk;
  
  	memset(&try_sa, 0, sizeof(struct sockaddr_pn));
  	try_sa.spn_family = AF_PHONET;

  	WARN_ON(!mutex_is_locked(&port_mutex));

  	if (!sport) {
  		/* search free port */

  		int port, pmin, pmax;

  		phonet_get_local_port_range(&pmin, &pmax);

  		for (port = pmin; port <= pmax; port++) {
  			port_cur++;
  			if (port_cur < pmin || port_cur > pmax)
  				port_cur = pmin;
  
  			pn_sockaddr_set_port(&try_sa, port_cur);

  			tmpsk = pn_find_sock_by_sa(net, &try_sa);

  			if (tmpsk == NULL) {
  				sport = port_cur;
  				goto found;
  			} else
  				sock_put(tmpsk);
  		}
  	} else {
  		/* try to find specific port */
  		pn_sockaddr_set_port(&try_sa, sport);

  		tmpsk = pn_find_sock_by_sa(net, &try_sa);

  		if (tmpsk == NULL)
  			/* No sock there! We can use that port... */
  			goto found;
  		else
  			sock_put(tmpsk);
  	}

  	/* the port must be in use already */
  	return -EADDRINUSE;
  
  found:

  	pn->sobject = pn_object(pn_addr(pn->sobject), sport);
  	return 0;
  }
  EXPORT_SYMBOL(pn_sock_get_port);

  #ifdef CONFIG_PROC_FS

  static struct sock *pn_sock_get_idx(struct seq_file *seq, loff_t pos)
  {
  	struct net *net = seq_file_net(seq);

  	struct hlist_head *hlist = pnsocks.hlist;

  	struct sock *sknode;

  	unsigned int h;

  	for (h = 0; h < PN_HASHSIZE; h++) {

  		sk_for_each_rcu(sknode, hlist) {

  			if (!net_eq(net, sock_net(sknode)))
  				continue;
  			if (!pos)
  				return sknode;
  			pos--;
  		}
  		hlist++;

  	}
  	return NULL;
  }
  
  static struct sock *pn_sock_get_next(struct seq_file *seq, struct sock *sk)
  {
  	struct net *net = seq_file_net(seq);
  
  	do
  		sk = sk_next(sk);
  	while (sk && !net_eq(net, sock_net(sk)));
  
  	return sk;
  }
  
  static void *pn_sock_seq_start(struct seq_file *seq, loff_t *pos)

  	__acquires(rcu)

  {

  	rcu_read_lock();

  	return *pos ? pn_sock_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
  }
  
  static void *pn_sock_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  {
  	struct sock *sk;
  
  	if (v == SEQ_START_TOKEN)
  		sk = pn_sock_get_idx(seq, 0);
  	else
  		sk = pn_sock_get_next(seq, v);
  	(*pos)++;
  	return sk;
  }
  
  static void pn_sock_seq_stop(struct seq_file *seq, void *v)

  	__releases(rcu)

  {

  	rcu_read_unlock();

  }
  
  static int pn_sock_seq_show(struct seq_file *seq, void *v)
  {

  	seq_setwidth(seq, 127);

  	if (v == SEQ_START_TOKEN)

  		seq_puts(seq, "pt  loc  rem rs st tx_queue rx_queue "
  			"  uid inode ref pointer drops");

  	else {
  		struct sock *sk = v;
  		struct pn_sock *pn = pn_sk(sk);
  
  		seq_printf(seq, "%2d %04X:%04X:%02X %02X %08X:%08X %5d %lu "

  			"%d %pK %d",

  			sk->sk_protocol, pn->sobject, pn->dobject,
  			pn->resource, sk->sk_state,

  			sk_wmem_alloc_get(sk), sk_rmem_alloc_get(sk),

  			from_kuid_munged(seq_user_ns(seq), sock_i_uid(sk)),
  			sock_i_ino(sk),

  			refcount_read(&sk->sk_refcnt), sk,

  			atomic_read(&sk->sk_drops));

  	}

  	seq_pad(seq, '
  ');

  	return 0;
  }
  
  static const struct seq_operations pn_sock_seq_ops = {
  	.start = pn_sock_seq_start,
  	.next = pn_sock_seq_next,
  	.stop = pn_sock_seq_stop,
  	.show = pn_sock_seq_show,
  };
  
  static int pn_sock_open(struct inode *inode, struct file *file)
  {

  	return seq_open_net(inode, file, &pn_sock_seq_ops,
  				sizeof(struct seq_net_private));

  }
  
  const struct file_operations pn_sock_seq_fops = {
  	.owner = THIS_MODULE,
  	.open = pn_sock_open,
  	.read = seq_read,
  	.llseek = seq_lseek,

  	.release = seq_release_net,

  };

  #endif

  
  static struct  {
  	struct sock *sk[256];
  } pnres;
  
  /*
   * Find and hold socket based on resource.
   */
  struct sock *pn_find_sock_by_res(struct net *net, u8 res)
  {
  	struct sock *sk;
  
  	if (!net_eq(net, &init_net))
  		return NULL;
  
  	rcu_read_lock();
  	sk = rcu_dereference(pnres.sk[res]);
  	if (sk)
  		sock_hold(sk);
  	rcu_read_unlock();
  	return sk;
  }
  
  static DEFINE_MUTEX(resource_mutex);
  
  int pn_sock_bind_res(struct sock *sk, u8 res)
  {
  	int ret = -EADDRINUSE;
  
  	if (!net_eq(sock_net(sk), &init_net))
  		return -ENOIOCTLCMD;
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  	if (pn_socket_autobind(sk->sk_socket))
  		return -EAGAIN;
  
  	mutex_lock(&resource_mutex);
  	if (pnres.sk[res] == NULL) {
  		sock_hold(sk);

  		rcu_assign_pointer(pnres.sk[res], sk);

  		ret = 0;
  	}
  	mutex_unlock(&resource_mutex);
  	return ret;
  }
  
  int pn_sock_unbind_res(struct sock *sk, u8 res)
  {
  	int ret = -ENOENT;
  
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	mutex_lock(&resource_mutex);
  	if (pnres.sk[res] == sk) {

  		RCU_INIT_POINTER(pnres.sk[res], NULL);

  		ret = 0;
  	}
  	mutex_unlock(&resource_mutex);
  
  	if (ret == 0) {
  		synchronize_rcu();
  		sock_put(sk);
  	}
  	return ret;
  }
  
  void pn_sock_unbind_all_res(struct sock *sk)
  {

  	unsigned int res, match = 0;

  
  	mutex_lock(&resource_mutex);
  	for (res = 0; res < 256; res++) {
  		if (pnres.sk[res] == sk) {

  			RCU_INIT_POINTER(pnres.sk[res], NULL);

  			match++;
  		}
  	}
  	mutex_unlock(&resource_mutex);

  	while (match > 0) {

  		__sock_put(sk);

  		match--;
  	}

  	/* Caller is responsible for RCU sync before final sock_put() */

  }

  
  #ifdef CONFIG_PROC_FS
  static struct sock **pn_res_get_idx(struct seq_file *seq, loff_t pos)
  {
  	struct net *net = seq_file_net(seq);

  	unsigned int i;

  
  	if (!net_eq(net, &init_net))
  		return NULL;
  
  	for (i = 0; i < 256; i++) {
  		if (pnres.sk[i] == NULL)
  			continue;
  		if (!pos)
  			return pnres.sk + i;
  		pos--;
  	}
  	return NULL;
  }
  
  static struct sock **pn_res_get_next(struct seq_file *seq, struct sock **sk)
  {
  	struct net *net = seq_file_net(seq);

  	unsigned int i;

  
  	BUG_ON(!net_eq(net, &init_net));
  
  	for (i = (sk - pnres.sk) + 1; i < 256; i++)
  		if (pnres.sk[i])
  			return pnres.sk + i;
  	return NULL;
  }
  
  static void *pn_res_seq_start(struct seq_file *seq, loff_t *pos)
  	__acquires(resource_mutex)
  {
  	mutex_lock(&resource_mutex);
  	return *pos ? pn_res_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
  }
  
  static void *pn_res_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  {
  	struct sock **sk;
  
  	if (v == SEQ_START_TOKEN)
  		sk = pn_res_get_idx(seq, 0);
  	else
  		sk = pn_res_get_next(seq, v);
  	(*pos)++;
  	return sk;
  }
  
  static void pn_res_seq_stop(struct seq_file *seq, void *v)
  	__releases(resource_mutex)
  {
  	mutex_unlock(&resource_mutex);
  }
  
  static int pn_res_seq_show(struct seq_file *seq, void *v)
  {

  	seq_setwidth(seq, 63);

  	if (v == SEQ_START_TOKEN)

  		seq_puts(seq, "rs   uid inode");

  	else {
  		struct sock **psk = v;
  		struct sock *sk = *psk;

  		seq_printf(seq, "%02X %5u %lu",

  			   (int) (psk - pnres.sk),
  			   from_kuid_munged(seq_user_ns(seq), sock_i_uid(sk)),

  			   sock_i_ino(sk));

  	}

  	seq_pad(seq, '
  ');

  	return 0;
  }
  
  static const struct seq_operations pn_res_seq_ops = {
  	.start = pn_res_seq_start,
  	.next = pn_res_seq_next,
  	.stop = pn_res_seq_stop,
  	.show = pn_res_seq_show,
  };
  
  static int pn_res_open(struct inode *inode, struct file *file)
  {
  	return seq_open_net(inode, file, &pn_res_seq_ops,
  				sizeof(struct seq_net_private));
  }
  
  const struct file_operations pn_res_seq_fops = {
  	.owner = THIS_MODULE,
  	.open = pn_res_open,
  	.read = seq_read,
  	.llseek = seq_lseek,
  	.release = seq_release_net,
  };
  #endif