/*
   * File: pep.c
   *
   * Phonet pipe protocol end point socket
   *
   * Copyright (C) 2008 Nokia Corporation.
   *
   * Author: 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/kernel.h>
  #include <linux/slab.h>
  #include <linux/socket.h>
  #include <net/sock.h>
  #include <net/tcp_states.h>
  #include <asm/ioctls.h>
  
  #include <linux/phonet.h>
  #include <linux/module.h>
  #include <net/phonet/phonet.h>
  #include <net/phonet/pep.h>
  #include <net/phonet/gprs.h>
  
  /* sk_state values:
   * TCP_CLOSE		sock not in use yet
   * TCP_CLOSE_WAIT	disconnected pipe
   * TCP_LISTEN		listening pipe endpoint
   * TCP_SYN_RECV		connected pipe in disabled state
   * TCP_ESTABLISHED	connected pipe in enabled state
   *
   * pep_sock locking:
   *  - sk_state, hlist: sock lock needed
   *  - listener: read only
   *  - pipe_handle: read only
   */
  
  #define CREDITS_MAX	10
  #define CREDITS_THR	7
  
  #define pep_sb_size(s) (((s) + 5) & ~3) /* 2-bytes head, 32-bits aligned */
  
  /* Get the next TLV sub-block. */
  static unsigned char *pep_get_sb(struct sk_buff *skb, u8 *ptype, u8 *plen,
  					void *buf)
  {
  	void *data = NULL;
  	struct {
  		u8 sb_type;
  		u8 sb_len;
  	} *ph, h;
  	int buflen = *plen;
  
  	ph = skb_header_pointer(skb, 0, 2, &h);
  	if (ph == NULL || ph->sb_len < 2 || !pskb_may_pull(skb, ph->sb_len))
  		return NULL;
  	ph->sb_len -= 2;
  	*ptype = ph->sb_type;
  	*plen = ph->sb_len;
  
  	if (buflen > ph->sb_len)
  		buflen = ph->sb_len;
  	data = skb_header_pointer(skb, 2, buflen, buf);
  	__skb_pull(skb, 2 + ph->sb_len);
  	return data;
  }
  
  static struct sk_buff *pep_alloc_skb(struct sock *sk, const void *payload,
  					int len, gfp_t priority)
  {
  	struct sk_buff *skb = alloc_skb(MAX_PNPIPE_HEADER + len, priority);
  	if (!skb)
  		return NULL;
  	skb_set_owner_w(skb, sk);
  
  	skb_reserve(skb, MAX_PNPIPE_HEADER);
  	__skb_put(skb, len);
  	skb_copy_to_linear_data(skb, payload, len);
  	__skb_push(skb, sizeof(struct pnpipehdr));
  	skb_reset_transport_header(skb);
  	return skb;
  }
  
  static int pep_reply(struct sock *sk, struct sk_buff *oskb, u8 code,
  			const void *data, int len, gfp_t priority)
  {
  	const struct pnpipehdr *oph = pnp_hdr(oskb);
  	struct pnpipehdr *ph;
  	struct sk_buff *skb;
  	struct sockaddr_pn peer;
  
  	skb = pep_alloc_skb(sk, data, len, priority);
  	if (!skb)
  		return -ENOMEM;
  
  	ph = pnp_hdr(skb);
  	ph->utid = oph->utid;
  	ph->message_id = oph->message_id + 1; /* REQ -> RESP */
  	ph->pipe_handle = oph->pipe_handle;
  	ph->error_code = code;
  
  	pn_skb_get_src_sockaddr(oskb, &peer);
  	return pn_skb_send(sk, skb, &peer);
  }
  
  static int pep_indicate(struct sock *sk, u8 id, u8 code,
  			const void *data, int len, gfp_t priority)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct pnpipehdr *ph;
  	struct sk_buff *skb;
  
  	skb = pep_alloc_skb(sk, data, len, priority);
  	if (!skb)
  		return -ENOMEM;
  
  	ph = pnp_hdr(skb);
  	ph->utid = 0;
  	ph->message_id = id;
  	ph->pipe_handle = pn->pipe_handle;
  	ph->data[0] = code;
  	return pn_skb_send(sk, skb, NULL);
  }
  
  #define PAD 0x00
  
  static int pipe_handler_request(struct sock *sk, u8 id, u8 code,
  				const void *data, int len)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct pnpipehdr *ph;
  	struct sk_buff *skb;
  
  	skb = pep_alloc_skb(sk, data, len, GFP_KERNEL);
  	if (!skb)
  		return -ENOMEM;
  
  	ph = pnp_hdr(skb);
  	ph->utid = id; /* whatever */
  	ph->message_id = id;
  	ph->pipe_handle = pn->pipe_handle;
  	ph->data[0] = code;
  	return pn_skb_send(sk, skb, NULL);
  }
  
  static int pipe_handler_send_created_ind(struct sock *sk)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	u8 data[4] = {
  		PN_PIPE_SB_NEGOTIATED_FC, pep_sb_size(2),
  		pn->tx_fc, pn->rx_fc,
  	};
  
  	return pep_indicate(sk, PNS_PIPE_CREATED_IND, 1 /* sub-blocks */,
  				data, 4, GFP_ATOMIC);
  }
  
  static int pep_accept_conn(struct sock *sk, struct sk_buff *skb)
  {
  	static const u8 data[20] = {
  		PAD, PAD, PAD, 2 /* sub-blocks */,
  		PN_PIPE_SB_REQUIRED_FC_TX, pep_sb_size(5), 3, PAD,
  			PN_MULTI_CREDIT_FLOW_CONTROL,
  			PN_ONE_CREDIT_FLOW_CONTROL,
  			PN_LEGACY_FLOW_CONTROL,
  			PAD,
  		PN_PIPE_SB_PREFERRED_FC_RX, pep_sb_size(5), 3, PAD,
  			PN_MULTI_CREDIT_FLOW_CONTROL,
  			PN_ONE_CREDIT_FLOW_CONTROL,
  			PN_LEGACY_FLOW_CONTROL,
  			PAD,
  	};
  
  	might_sleep();
  	return pep_reply(sk, skb, PN_PIPE_NO_ERROR, data, sizeof(data),
  				GFP_KERNEL);
  }
  
  static int pep_reject_conn(struct sock *sk, struct sk_buff *skb, u8 code,
  				gfp_t priority)
  {
  	static const u8 data[4] = { PAD, PAD, PAD, 0 /* sub-blocks */ };
  	WARN_ON(code == PN_PIPE_NO_ERROR);
  	return pep_reply(sk, skb, code, data, sizeof(data), priority);
  }
  
  /* Control requests are not sent by the pipe service and have a specific
   * message format. */
  static int pep_ctrlreq_error(struct sock *sk, struct sk_buff *oskb, u8 code,
  				gfp_t priority)
  {
  	const struct pnpipehdr *oph = pnp_hdr(oskb);
  	struct sk_buff *skb;
  	struct pnpipehdr *ph;
  	struct sockaddr_pn dst;
  	u8 data[4] = {
  		oph->data[0], /* PEP type */
  		code, /* error code, at an unusual offset */
  		PAD, PAD,
  	};
  
  	skb = pep_alloc_skb(sk, data, 4, priority);
  	if (!skb)
  		return -ENOMEM;
  
  	ph = pnp_hdr(skb);
  	ph->utid = oph->utid;
  	ph->message_id = PNS_PEP_CTRL_RESP;
  	ph->pipe_handle = oph->pipe_handle;
  	ph->data[0] = oph->data[1]; /* CTRL id */
  
  	pn_skb_get_src_sockaddr(oskb, &dst);
  	return pn_skb_send(sk, skb, &dst);
  }
  
  static int pipe_snd_status(struct sock *sk, u8 type, u8 status, gfp_t priority)
  {
  	u8 data[4] = { type, PAD, PAD, status };
  
  	return pep_indicate(sk, PNS_PEP_STATUS_IND, PN_PEP_TYPE_COMMON,
  				data, 4, priority);
  }
  
  /* Send our RX flow control information to the sender.
   * Socket must be locked. */
  static void pipe_grant_credits(struct sock *sk, gfp_t priority)
  {
  	struct pep_sock *pn = pep_sk(sk);
  
  	BUG_ON(sk->sk_state != TCP_ESTABLISHED);
  
  	switch (pn->rx_fc) {
  	case PN_LEGACY_FLOW_CONTROL: /* TODO */
  		break;
  	case PN_ONE_CREDIT_FLOW_CONTROL:
  		if (pipe_snd_status(sk, PN_PEP_IND_FLOW_CONTROL,
  					PEP_IND_READY, priority) == 0)
  			pn->rx_credits = 1;
  		break;
  	case PN_MULTI_CREDIT_FLOW_CONTROL:
  		if ((pn->rx_credits + CREDITS_THR) > CREDITS_MAX)
  			break;
  		if (pipe_snd_status(sk, PN_PEP_IND_ID_MCFC_GRANT_CREDITS,
  					CREDITS_MAX - pn->rx_credits,
  					priority) == 0)
  			pn->rx_credits = CREDITS_MAX;
  		break;
  	}
  }
  
  static int pipe_rcv_status(struct sock *sk, struct sk_buff *skb)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct pnpipehdr *hdr;
  	int wake = 0;
  
  	if (!pskb_may_pull(skb, sizeof(*hdr) + 4))
  		return -EINVAL;
  
  	hdr = pnp_hdr(skb);
  	if (hdr->data[0] != PN_PEP_TYPE_COMMON) {
  		LIMIT_NETDEBUG(KERN_DEBUG"Phonet unknown PEP type: %u
  ",
  				(unsigned int)hdr->data[0]);
  		return -EOPNOTSUPP;
  	}
  
  	switch (hdr->data[1]) {
  	case PN_PEP_IND_FLOW_CONTROL:
  		switch (pn->tx_fc) {
  		case PN_LEGACY_FLOW_CONTROL:
  			switch (hdr->data[4]) {
  			case PEP_IND_BUSY:
  				atomic_set(&pn->tx_credits, 0);
  				break;
  			case PEP_IND_READY:
  				atomic_set(&pn->tx_credits, wake = 1);
  				break;
  			}
  			break;
  		case PN_ONE_CREDIT_FLOW_CONTROL:
  			if (hdr->data[4] == PEP_IND_READY)
  				atomic_set(&pn->tx_credits, wake = 1);
  			break;
  		}
  		break;
  
  	case PN_PEP_IND_ID_MCFC_GRANT_CREDITS:
  		if (pn->tx_fc != PN_MULTI_CREDIT_FLOW_CONTROL)
  			break;
  		atomic_add(wake = hdr->data[4], &pn->tx_credits);
  		break;
  
  	default:
  		LIMIT_NETDEBUG(KERN_DEBUG"Phonet unknown PEP indication: %u
  ",
  				(unsigned int)hdr->data[1]);
  		return -EOPNOTSUPP;
  	}
  	if (wake)
  		sk->sk_write_space(sk);
  	return 0;
  }
  
  static int pipe_rcv_created(struct sock *sk, struct sk_buff *skb)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct pnpipehdr *hdr = pnp_hdr(skb);
  	u8 n_sb = hdr->data[0];
  
  	pn->rx_fc = pn->tx_fc = PN_LEGACY_FLOW_CONTROL;
  	__skb_pull(skb, sizeof(*hdr));
  	while (n_sb > 0) {
  		u8 type, buf[2], len = sizeof(buf);
  		u8 *data = pep_get_sb(skb, &type, &len, buf);
  
  		if (data == NULL)
  			return -EINVAL;
  		switch (type) {
  		case PN_PIPE_SB_NEGOTIATED_FC:
  			if (len < 2 || (data[0] | data[1]) > 3)
  				break;
  			pn->tx_fc = data[0] & 3;
  			pn->rx_fc = data[1] & 3;
  			break;
  		}
  		n_sb--;
  	}
  	return 0;
  }
  
  /* Queue an skb to a connected sock.
   * Socket lock must be held. */
  static int pipe_do_rcv(struct sock *sk, struct sk_buff *skb)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct pnpipehdr *hdr = pnp_hdr(skb);
  	struct sk_buff_head *queue;
  	int err = 0;
  
  	BUG_ON(sk->sk_state == TCP_CLOSE_WAIT);
  
  	switch (hdr->message_id) {
  	case PNS_PEP_CONNECT_REQ:
  		pep_reject_conn(sk, skb, PN_PIPE_ERR_PEP_IN_USE, GFP_ATOMIC);
  		break;
  
  	case PNS_PEP_DISCONNECT_REQ:
  		pep_reply(sk, skb, PN_PIPE_NO_ERROR, NULL, 0, GFP_ATOMIC);
  		sk->sk_state = TCP_CLOSE_WAIT;
  		if (!sock_flag(sk, SOCK_DEAD))
  			sk->sk_state_change(sk);
  		break;
  
  	case PNS_PEP_ENABLE_REQ:
  		/* Wait for PNS_PIPE_(ENABLED|REDIRECTED)_IND */
  		pep_reply(sk, skb, PN_PIPE_NO_ERROR, NULL, 0, GFP_ATOMIC);
  		break;
  
  	case PNS_PEP_RESET_REQ:
  		switch (hdr->state_after_reset) {
  		case PN_PIPE_DISABLE:
  			pn->init_enable = 0;
  			break;
  		case PN_PIPE_ENABLE:
  			pn->init_enable = 1;
  			break;
  		default: /* not allowed to send an error here!? */
  			err = -EINVAL;
  			goto out;
  		}
  		/* fall through */
  	case PNS_PEP_DISABLE_REQ:
  		atomic_set(&pn->tx_credits, 0);
  		pep_reply(sk, skb, PN_PIPE_NO_ERROR, NULL, 0, GFP_ATOMIC);
  		break;
  
  	case PNS_PEP_CTRL_REQ:
  		if (skb_queue_len(&pn->ctrlreq_queue) >= PNPIPE_CTRLREQ_MAX) {
  			atomic_inc(&sk->sk_drops);
  			break;
  		}
  		__skb_pull(skb, 4);
  		queue = &pn->ctrlreq_queue;
  		goto queue;
  
  	case PNS_PIPE_ALIGNED_DATA:
  		__skb_pull(skb, 1);
  		/* fall through */
  	case PNS_PIPE_DATA:
  		__skb_pull(skb, 3); /* Pipe data header */
  		if (!pn_flow_safe(pn->rx_fc)) {
  			err = sock_queue_rcv_skb(sk, skb);
  			if (!err)
  				return NET_RX_SUCCESS;
  			err = -ENOBUFS;
  			break;
  		}
  
  		if (pn->rx_credits == 0) {
  			atomic_inc(&sk->sk_drops);
  			err = -ENOBUFS;
  			break;
  		}
  		pn->rx_credits--;
  		queue = &sk->sk_receive_queue;
  		goto queue;
  
  	case PNS_PEP_STATUS_IND:
  		pipe_rcv_status(sk, skb);
  		break;
  
  	case PNS_PIPE_REDIRECTED_IND:
  		err = pipe_rcv_created(sk, skb);
  		break;
  
  	case PNS_PIPE_CREATED_IND:
  		err = pipe_rcv_created(sk, skb);
  		if (err)
  			break;
  		/* fall through */
  	case PNS_PIPE_RESET_IND:
  		if (!pn->init_enable)
  			break;
  		/* fall through */
  	case PNS_PIPE_ENABLED_IND:
  		if (!pn_flow_safe(pn->tx_fc)) {
  			atomic_set(&pn->tx_credits, 1);
  			sk->sk_write_space(sk);
  		}
  		if (sk->sk_state == TCP_ESTABLISHED)
  			break; /* Nothing to do */
  		sk->sk_state = TCP_ESTABLISHED;
  		pipe_grant_credits(sk, GFP_ATOMIC);
  		break;
  
  	case PNS_PIPE_DISABLED_IND:
  		sk->sk_state = TCP_SYN_RECV;
  		pn->rx_credits = 0;
  		break;
  
  	default:
  		LIMIT_NETDEBUG(KERN_DEBUG"Phonet unknown PEP message: %u
  ",
  				hdr->message_id);
  		err = -EINVAL;
  	}
  out:
  	kfree_skb(skb);
  	return (err == -ENOBUFS) ? NET_RX_DROP : NET_RX_SUCCESS;
  
  queue:
  	skb->dev = NULL;
  	skb_set_owner_r(skb, sk);
  	err = skb->len;
  	skb_queue_tail(queue, skb);
  	if (!sock_flag(sk, SOCK_DEAD))
  		sk->sk_data_ready(sk, err);
  	return NET_RX_SUCCESS;
  }
  
  /* Destroy connected sock. */
  static void pipe_destruct(struct sock *sk)
  {
  	struct pep_sock *pn = pep_sk(sk);
  
  	skb_queue_purge(&sk->sk_receive_queue);
  	skb_queue_purge(&pn->ctrlreq_queue);
  }
  
  static u8 pipe_negotiate_fc(const u8 *fcs, unsigned int n)
  {
  	unsigned int i;
  	u8 final_fc = PN_NO_FLOW_CONTROL;
  
  	for (i = 0; i < n; i++) {
  		u8 fc = fcs[i];
  
  		if (fc > final_fc && fc < PN_MAX_FLOW_CONTROL)
  			final_fc = fc;
  	}
  	return final_fc;
  }
  
  static int pep_connresp_rcv(struct sock *sk, struct sk_buff *skb)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct pnpipehdr *hdr;
  	u8 n_sb;
  
  	if (!pskb_pull(skb, sizeof(*hdr) + 4))
  		return -EINVAL;
  
  	hdr = pnp_hdr(skb);
  	if (hdr->error_code != PN_PIPE_NO_ERROR)
  		return -ECONNREFUSED;
  
  	/* Parse sub-blocks */
  	n_sb = hdr->data[4];
  	while (n_sb > 0) {
  		u8 type, buf[6], len = sizeof(buf);
  		const u8 *data = pep_get_sb(skb, &type, &len, buf);
  
  		if (data == NULL)
  			return -EINVAL;
  
  		switch (type) {
  		case PN_PIPE_SB_REQUIRED_FC_TX:
  			if (len < 2 || len < data[0])
  				break;
  			pn->tx_fc = pipe_negotiate_fc(data + 2, len - 2);
  			break;
  
  		case PN_PIPE_SB_PREFERRED_FC_RX:
  			if (len < 2 || len < data[0])
  				break;
  			pn->rx_fc = pipe_negotiate_fc(data + 2, len - 2);
  			break;
  
  		}
  		n_sb--;
  	}
  
  	return pipe_handler_send_created_ind(sk);
  }
  
  static int pep_enableresp_rcv(struct sock *sk, struct sk_buff *skb)
  {
  	struct pnpipehdr *hdr = pnp_hdr(skb);
  
  	if (hdr->error_code != PN_PIPE_NO_ERROR)
  		return -ECONNREFUSED;
  
  	return pep_indicate(sk, PNS_PIPE_ENABLED_IND, 0 /* sub-blocks */,
  		NULL, 0, GFP_ATOMIC);
  
  }
  
  static void pipe_start_flow_control(struct sock *sk)
  {
  	struct pep_sock *pn = pep_sk(sk);
  
  	if (!pn_flow_safe(pn->tx_fc)) {
  		atomic_set(&pn->tx_credits, 1);
  		sk->sk_write_space(sk);
  	}
  	pipe_grant_credits(sk, GFP_ATOMIC);
  }
  
  /* Queue an skb to an actively connected sock.
   * Socket lock must be held. */
  static int pipe_handler_do_rcv(struct sock *sk, struct sk_buff *skb)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct pnpipehdr *hdr = pnp_hdr(skb);
  	int err = NET_RX_SUCCESS;
  
  	switch (hdr->message_id) {
  	case PNS_PIPE_ALIGNED_DATA:
  		__skb_pull(skb, 1);
  		/* fall through */
  	case PNS_PIPE_DATA:
  		__skb_pull(skb, 3); /* Pipe data header */
  		if (!pn_flow_safe(pn->rx_fc)) {
  			err = sock_queue_rcv_skb(sk, skb);
  			if (!err)
  				return NET_RX_SUCCESS;
  			err = NET_RX_DROP;
  			break;
  		}
  
  		if (pn->rx_credits == 0) {
  			atomic_inc(&sk->sk_drops);
  			err = NET_RX_DROP;
  			break;
  		}
  		pn->rx_credits--;
  		skb->dev = NULL;
  		skb_set_owner_r(skb, sk);
  		err = skb->len;
  		skb_queue_tail(&sk->sk_receive_queue, skb);
  		if (!sock_flag(sk, SOCK_DEAD))
  			sk->sk_data_ready(sk, err);
  		return NET_RX_SUCCESS;
  
  	case PNS_PEP_CONNECT_RESP:
  		if (sk->sk_state != TCP_SYN_SENT)
  			break;
  		if (!sock_flag(sk, SOCK_DEAD))
  			sk->sk_state_change(sk);
  		if (pep_connresp_rcv(sk, skb)) {
  			sk->sk_state = TCP_CLOSE_WAIT;
  			break;
  		}
  		if (pn->init_enable == PN_PIPE_DISABLE)
  			sk->sk_state = TCP_SYN_RECV;
  		else {
  			sk->sk_state = TCP_ESTABLISHED;
  			pipe_start_flow_control(sk);
  		}
  		break;
  
  	case PNS_PEP_ENABLE_RESP:
  		if (sk->sk_state != TCP_SYN_SENT)
  			break;
  
  		if (pep_enableresp_rcv(sk, skb)) {
  			sk->sk_state = TCP_CLOSE_WAIT;
  			break;
  		}
  
  		sk->sk_state = TCP_ESTABLISHED;
  		pipe_start_flow_control(sk);
  		break;
  
  	case PNS_PEP_DISCONNECT_RESP:
  		/* sock should already be dead, nothing to do */
  		break;
  
  	case PNS_PEP_STATUS_IND:
  		pipe_rcv_status(sk, skb);
  		break;
  	}
  	kfree_skb(skb);
  	return err;
  }
  
  /* Listening sock must be locked */
  static struct sock *pep_find_pipe(const struct hlist_head *hlist,
  					const struct sockaddr_pn *dst,
  					u8 pipe_handle)
  {
  	struct sock *sknode;
  	u16 dobj = pn_sockaddr_get_object(dst);
  
  	sk_for_each(sknode, hlist) {
  		struct pep_sock *pnnode = pep_sk(sknode);
  
  		/* Ports match, but addresses might not: */
  		if (pnnode->pn_sk.sobject != dobj)
  			continue;
  		if (pnnode->pipe_handle != pipe_handle)
  			continue;
  		if (sknode->sk_state == TCP_CLOSE_WAIT)
  			continue;
  
  		sock_hold(sknode);
  		return sknode;
  	}
  	return NULL;
  }
  
  /*
   * Deliver an skb to a listening sock.
   * Socket lock must be held.
   * We then queue the skb to the right connected sock (if any).
   */
  static int pep_do_rcv(struct sock *sk, struct sk_buff *skb)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct sock *sknode;
  	struct pnpipehdr *hdr;
  	struct sockaddr_pn dst;
  	u8 pipe_handle;
  
  	if (!pskb_may_pull(skb, sizeof(*hdr)))
  		goto drop;
  
  	hdr = pnp_hdr(skb);
  	pipe_handle = hdr->pipe_handle;
  	if (pipe_handle == PN_PIPE_INVALID_HANDLE)
  		goto drop;
  
  	pn_skb_get_dst_sockaddr(skb, &dst);
  
  	/* Look for an existing pipe handle */
  	sknode = pep_find_pipe(&pn->hlist, &dst, pipe_handle);
  	if (sknode)
  		return sk_receive_skb(sknode, skb, 1);
  
  	switch (hdr->message_id) {
  	case PNS_PEP_CONNECT_REQ:
  		if (sk->sk_state != TCP_LISTEN || sk_acceptq_is_full(sk)) {
  			pep_reject_conn(sk, skb, PN_PIPE_ERR_PEP_IN_USE,
  					GFP_ATOMIC);
  			break;
  		}
  		skb_queue_head(&sk->sk_receive_queue, skb);
  		sk_acceptq_added(sk);
  		if (!sock_flag(sk, SOCK_DEAD))
  			sk->sk_data_ready(sk, 0);
  		return NET_RX_SUCCESS;
  
  	case PNS_PEP_DISCONNECT_REQ:
  		pep_reply(sk, skb, PN_PIPE_NO_ERROR, NULL, 0, GFP_ATOMIC);
  		break;
  
  	case PNS_PEP_CTRL_REQ:
  		pep_ctrlreq_error(sk, skb, PN_PIPE_INVALID_HANDLE, GFP_ATOMIC);
  		break;
  
  	case PNS_PEP_RESET_REQ:
  	case PNS_PEP_ENABLE_REQ:
  	case PNS_PEP_DISABLE_REQ:
  		/* invalid handle is not even allowed here! */
  		break;
  
  	default:
  		if ((1 << sk->sk_state)
  				& ~(TCPF_CLOSE|TCPF_LISTEN|TCPF_CLOSE_WAIT))
  			/* actively connected socket */
  			return pipe_handler_do_rcv(sk, skb);
  	}
  drop:
  	kfree_skb(skb);
  	return NET_RX_SUCCESS;
  }
  
  static int pipe_do_remove(struct sock *sk)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct pnpipehdr *ph;
  	struct sk_buff *skb;
  
  	skb = pep_alloc_skb(sk, NULL, 0, GFP_KERNEL);
  	if (!skb)
  		return -ENOMEM;
  
  	ph = pnp_hdr(skb);
  	ph->utid = 0;
  	ph->message_id = PNS_PIPE_REMOVE_REQ;
  	ph->pipe_handle = pn->pipe_handle;
  	ph->data[0] = PAD;
  	return pn_skb_send(sk, skb, NULL);
  }
  
  /* associated socket ceases to exist */
  static void pep_sock_close(struct sock *sk, long timeout)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	int ifindex = 0;
  
  	sock_hold(sk); /* keep a reference after sk_common_release() */
  	sk_common_release(sk);
  
  	lock_sock(sk);
  	if ((1 << sk->sk_state) & (TCPF_SYN_RECV|TCPF_ESTABLISHED)) {
  		if (sk->sk_backlog_rcv == pipe_do_rcv)
  			/* Forcefully remove dangling Phonet pipe */
  			pipe_do_remove(sk);
  		else
  			pipe_handler_request(sk, PNS_PEP_DISCONNECT_REQ, PAD,
  						NULL, 0);
  	}
  	sk->sk_state = TCP_CLOSE;
  
  	ifindex = pn->ifindex;
  	pn->ifindex = 0;
  	release_sock(sk);
  
  	if (ifindex)
  		gprs_detach(sk);
  	sock_put(sk);
  }
  
  static struct sock *pep_sock_accept(struct sock *sk, int flags, int *errp)
  {
  	struct pep_sock *pn = pep_sk(sk), *newpn;
  	struct sock *newsk = NULL;
  	struct sk_buff *skb;
  	struct pnpipehdr *hdr;
  	struct sockaddr_pn dst, src;
  	int err;
  	u16 peer_type;
  	u8 pipe_handle, enabled, n_sb;
  	u8 aligned = 0;
  
  	skb = skb_recv_datagram(sk, 0, flags & O_NONBLOCK, errp);
  	if (!skb)
  		return NULL;
  
  	lock_sock(sk);
  	if (sk->sk_state != TCP_LISTEN) {
  		err = -EINVAL;
  		goto drop;
  	}
  	sk_acceptq_removed(sk);
  
  	err = -EPROTO;
  	if (!pskb_may_pull(skb, sizeof(*hdr) + 4))
  		goto drop;
  
  	hdr = pnp_hdr(skb);
  	pipe_handle = hdr->pipe_handle;
  	switch (hdr->state_after_connect) {
  	case PN_PIPE_DISABLE:
  		enabled = 0;
  		break;
  	case PN_PIPE_ENABLE:
  		enabled = 1;
  		break;
  	default:
  		pep_reject_conn(sk, skb, PN_PIPE_ERR_INVALID_PARAM,
  				GFP_KERNEL);
  		goto drop;
  	}
  	peer_type = hdr->other_pep_type << 8;
  
  	/* Parse sub-blocks (options) */
  	n_sb = hdr->data[4];
  	while (n_sb > 0) {
  		u8 type, buf[1], len = sizeof(buf);
  		const u8 *data = pep_get_sb(skb, &type, &len, buf);
  
  		if (data == NULL)
  			goto drop;
  		switch (type) {
  		case PN_PIPE_SB_CONNECT_REQ_PEP_SUB_TYPE:
  			if (len < 1)
  				goto drop;
  			peer_type = (peer_type & 0xff00) | data[0];
  			break;
  		case PN_PIPE_SB_ALIGNED_DATA:
  			aligned = data[0] != 0;
  			break;
  		}
  		n_sb--;
  	}
  
  	/* Check for duplicate pipe handle */
  	newsk = pep_find_pipe(&pn->hlist, &dst, pipe_handle);
  	if (unlikely(newsk)) {
  		__sock_put(newsk);
  		newsk = NULL;
  		pep_reject_conn(sk, skb, PN_PIPE_ERR_PEP_IN_USE, GFP_KERNEL);
  		goto drop;
  	}
  
  	/* Create a new to-be-accepted sock */
  	newsk = sk_alloc(sock_net(sk), PF_PHONET, GFP_KERNEL, sk->sk_prot);
  	if (!newsk) {
  		pep_reject_conn(sk, skb, PN_PIPE_ERR_OVERLOAD, GFP_KERNEL);
  		err = -ENOBUFS;
  		goto drop;
  	}
  
  	sock_init_data(NULL, newsk);
  	newsk->sk_state = TCP_SYN_RECV;
  	newsk->sk_backlog_rcv = pipe_do_rcv;
  	newsk->sk_protocol = sk->sk_protocol;
  	newsk->sk_destruct = pipe_destruct;
  
  	newpn = pep_sk(newsk);
  	pn_skb_get_dst_sockaddr(skb, &dst);
  	pn_skb_get_src_sockaddr(skb, &src);
  	newpn->pn_sk.sobject = pn_sockaddr_get_object(&dst);
  	newpn->pn_sk.dobject = pn_sockaddr_get_object(&src);
  	newpn->pn_sk.resource = pn_sockaddr_get_resource(&dst);
  	sock_hold(sk);
  	newpn->listener = sk;
  	skb_queue_head_init(&newpn->ctrlreq_queue);
  	newpn->pipe_handle = pipe_handle;
  	atomic_set(&newpn->tx_credits, 0);
  	newpn->ifindex = 0;
  	newpn->peer_type = peer_type;
  	newpn->rx_credits = 0;
  	newpn->rx_fc = newpn->tx_fc = PN_LEGACY_FLOW_CONTROL;
  	newpn->init_enable = enabled;
  	newpn->aligned = aligned;
  
  	err = pep_accept_conn(newsk, skb);
  	if (err) {
  		sock_put(newsk);
  		newsk = NULL;
  		goto drop;
  	}
  	sk_add_node(newsk, &pn->hlist);
  drop:
  	release_sock(sk);
  	kfree_skb(skb);
  	*errp = err;
  	return newsk;
  }
  
  static int pep_sock_connect(struct sock *sk, struct sockaddr *addr, int len)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	int err;
  	u8 data[4] = { 0 /* sub-blocks */, PAD, PAD, PAD };
  
  	if (pn->pipe_handle == PN_PIPE_INVALID_HANDLE)
  		pn->pipe_handle = 1; /* anything but INVALID_HANDLE */
  
  	err = pipe_handler_request(sk, PNS_PEP_CONNECT_REQ,
  				pn->init_enable, data, 4);
  	if (err) {
  		pn->pipe_handle = PN_PIPE_INVALID_HANDLE;
  		return err;
  	}
  
  	sk->sk_state = TCP_SYN_SENT;
  
  	return 0;
  }
  
  static int pep_sock_enable(struct sock *sk, struct sockaddr *addr, int len)
  {
  	int err;
  
  	err = pipe_handler_request(sk, PNS_PEP_ENABLE_REQ, PAD,
  				NULL, 0);
  	if (err)
  		return err;
  
  	sk->sk_state = TCP_SYN_SENT;
  
  	return 0;
  }
  
  static int pep_ioctl(struct sock *sk, int cmd, unsigned long arg)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	int answ;
  	int ret = -ENOIOCTLCMD;
  
  	switch (cmd) {
  	case SIOCINQ:
  		if (sk->sk_state == TCP_LISTEN) {
  			ret = -EINVAL;
  			break;
  		}
  
  		lock_sock(sk);
  		if (sock_flag(sk, SOCK_URGINLINE) &&
  		    !skb_queue_empty(&pn->ctrlreq_queue))
  			answ = skb_peek(&pn->ctrlreq_queue)->len;
  		else if (!skb_queue_empty(&sk->sk_receive_queue))
  			answ = skb_peek(&sk->sk_receive_queue)->len;
  		else
  			answ = 0;
  		release_sock(sk);
  		ret = put_user(answ, (int __user *)arg);
  		break;
  
  	case SIOCPNENABLEPIPE:
  		lock_sock(sk);
  		if (sk->sk_state == TCP_SYN_SENT)
  			ret =  -EBUSY;
  		else if (sk->sk_state == TCP_ESTABLISHED)
  			ret = -EISCONN;
  		else
  			ret = pep_sock_enable(sk, NULL, 0);
  		release_sock(sk);
  		break;
  	}
  
  	return ret;
  }
  
  static int pep_init(struct sock *sk)
  {
  	struct pep_sock *pn = pep_sk(sk);
  
  	sk->sk_destruct = pipe_destruct;
  	INIT_HLIST_HEAD(&pn->hlist);
  	pn->listener = NULL;
  	skb_queue_head_init(&pn->ctrlreq_queue);
  	atomic_set(&pn->tx_credits, 0);
  	pn->ifindex = 0;
  	pn->peer_type = 0;
  	pn->pipe_handle = PN_PIPE_INVALID_HANDLE;
  	pn->rx_credits = 0;
  	pn->rx_fc = pn->tx_fc = PN_LEGACY_FLOW_CONTROL;
  	pn->init_enable = 1;
  	pn->aligned = 0;
  	return 0;
  }
  
  static int pep_setsockopt(struct sock *sk, int level, int optname,
  				char __user *optval, unsigned int optlen)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	int val = 0, err = 0;
  
  	if (level != SOL_PNPIPE)
  		return -ENOPROTOOPT;
  	if (optlen >= sizeof(int)) {
  		if (get_user(val, (int __user *) optval))
  			return -EFAULT;
  	}
  
  	lock_sock(sk);
  	switch (optname) {
  	case PNPIPE_ENCAP:
  		if (val && val != PNPIPE_ENCAP_IP) {
  			err = -EINVAL;
  			break;
  		}
  		if (!pn->ifindex == !val)
  			break; /* Nothing to do! */
  		if (!capable(CAP_NET_ADMIN)) {
  			err = -EPERM;
  			break;
  		}
  		if (val) {
  			release_sock(sk);
  			err = gprs_attach(sk);
  			if (err > 0) {
  				pn->ifindex = err;
  				err = 0;
  			}
  		} else {
  			pn->ifindex = 0;
  			release_sock(sk);
  			gprs_detach(sk);
  			err = 0;
  		}
  		goto out_norel;
  
  	case PNPIPE_HANDLE:
  		if ((sk->sk_state == TCP_CLOSE) &&
  			(val >= 0) && (val < PN_PIPE_INVALID_HANDLE))
  			pn->pipe_handle = val;
  		else
  			err = -EINVAL;
  		break;
  
  	case PNPIPE_INITSTATE:
  		pn->init_enable = !!val;
  		break;
  
  	default:
  		err = -ENOPROTOOPT;
  	}
  	release_sock(sk);
  
  out_norel:
  	return err;
  }
  
  static int pep_getsockopt(struct sock *sk, int level, int optname,
  				char __user *optval, int __user *optlen)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	int len, val;
  
  	if (level != SOL_PNPIPE)
  		return -ENOPROTOOPT;
  	if (get_user(len, optlen))
  		return -EFAULT;
  
  	switch (optname) {
  	case PNPIPE_ENCAP:
  		val = pn->ifindex ? PNPIPE_ENCAP_IP : PNPIPE_ENCAP_NONE;
  		break;
  
  	case PNPIPE_IFINDEX:
  		val = pn->ifindex;
  		break;
  
  	case PNPIPE_HANDLE:
  		val = pn->pipe_handle;
  		if (val == PN_PIPE_INVALID_HANDLE)
  			return -EINVAL;
  		break;
  
  	case PNPIPE_INITSTATE:
  		val = pn->init_enable;
  		break;
  
  	default:
  		return -ENOPROTOOPT;
  	}
  
  	len = min_t(unsigned int, sizeof(int), len);
  	if (put_user(len, optlen))
  		return -EFAULT;
  	if (put_user(val, (int __user *) optval))
  		return -EFAULT;
  	return 0;
  }
  
  static int pipe_skb_send(struct sock *sk, struct sk_buff *skb)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct pnpipehdr *ph;
  	int err;
  
  	if (pn_flow_safe(pn->tx_fc) &&
  	    !atomic_add_unless(&pn->tx_credits, -1, 0)) {
  		kfree_skb(skb);
  		return -ENOBUFS;
  	}
  
  	skb_push(skb, 3 + pn->aligned);
  	skb_reset_transport_header(skb);
  	ph = pnp_hdr(skb);
  	ph->utid = 0;
  	if (pn->aligned) {
  		ph->message_id = PNS_PIPE_ALIGNED_DATA;
  		ph->data[0] = 0; /* padding */
  	} else
  		ph->message_id = PNS_PIPE_DATA;
  	ph->pipe_handle = pn->pipe_handle;
  	err = pn_skb_send(sk, skb, NULL);
  
  	if (err && pn_flow_safe(pn->tx_fc))
  		atomic_inc(&pn->tx_credits);
  	return err;
  
  }
  
  static int pep_sendmsg(struct kiocb *iocb, struct sock *sk,
  			struct msghdr *msg, size_t len)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct sk_buff *skb;
  	long timeo;
  	int flags = msg->msg_flags;
  	int err, done;
  
  	if (len > USHRT_MAX)
  		return -EMSGSIZE;
  
  	if ((msg->msg_flags & ~(MSG_DONTWAIT|MSG_EOR|MSG_NOSIGNAL|
  				MSG_CMSG_COMPAT)) ||
  			!(msg->msg_flags & MSG_EOR))
  		return -EOPNOTSUPP;
  
  	skb = sock_alloc_send_skb(sk, MAX_PNPIPE_HEADER + len,
  					flags & MSG_DONTWAIT, &err);
  	if (!skb)
  		return err;
  
  	skb_reserve(skb, MAX_PHONET_HEADER + 3 + pn->aligned);
  	err = memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len);
  	if (err < 0)
  		goto outfree;
  
  	lock_sock(sk);
  	timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
  	if ((1 << sk->sk_state) & (TCPF_LISTEN|TCPF_CLOSE)) {
  		err = -ENOTCONN;
  		goto out;
  	}
  	if (sk->sk_state != TCP_ESTABLISHED) {
  		/* Wait until the pipe gets to enabled state */
  disabled:
  		err = sk_stream_wait_connect(sk, &timeo);
  		if (err)
  			goto out;
  
  		if (sk->sk_state == TCP_CLOSE_WAIT) {
  			err = -ECONNRESET;
  			goto out;
  		}
  	}
  	BUG_ON(sk->sk_state != TCP_ESTABLISHED);
  
  	/* Wait until flow control allows TX */
  	done = atomic_read(&pn->tx_credits);
  	while (!done) {
  		DEFINE_WAIT(wait);
  
  		if (!timeo) {
  			err = -EAGAIN;
  			goto out;
  		}
  		if (signal_pending(current)) {
  			err = sock_intr_errno(timeo);
  			goto out;
  		}
  
  		prepare_to_wait(sk_sleep(sk), &wait,
  				TASK_INTERRUPTIBLE);
  		done = sk_wait_event(sk, &timeo, atomic_read(&pn->tx_credits));
  		finish_wait(sk_sleep(sk), &wait);
  
  		if (sk->sk_state != TCP_ESTABLISHED)
  			goto disabled;
  	}
  
  	err = pipe_skb_send(sk, skb);
  	if (err >= 0)
  		err = len; /* success! */
  	skb = NULL;
  out:
  	release_sock(sk);
  outfree:
  	kfree_skb(skb);
  	return err;
  }
  
  int pep_writeable(struct sock *sk)
  {
  	struct pep_sock *pn = pep_sk(sk);
  
  	return atomic_read(&pn->tx_credits);
  }
  
  int pep_write(struct sock *sk, struct sk_buff *skb)
  {
  	struct sk_buff *rskb, *fs;
  	int flen = 0;
  
  	if (pep_sk(sk)->aligned)
  		return pipe_skb_send(sk, skb);
  
  	rskb = alloc_skb(MAX_PNPIPE_HEADER, GFP_ATOMIC);
  	if (!rskb) {
  		kfree_skb(skb);
  		return -ENOMEM;
  	}
  	skb_shinfo(rskb)->frag_list = skb;
  	rskb->len += skb->len;
  	rskb->data_len += rskb->len;
  	rskb->truesize += rskb->len;
  
  	/* Avoid nested fragments */
  	skb_walk_frags(skb, fs)
  		flen += fs->len;
  	skb->next = skb_shinfo(skb)->frag_list;
  	skb_frag_list_init(skb);
  	skb->len -= flen;
  	skb->data_len -= flen;
  	skb->truesize -= flen;
  
  	skb_reserve(rskb, MAX_PHONET_HEADER + 3);
  	return pipe_skb_send(sk, rskb);
  }
  
  struct sk_buff *pep_read(struct sock *sk)
  {
  	struct sk_buff *skb = skb_dequeue(&sk->sk_receive_queue);
  
  	if (sk->sk_state == TCP_ESTABLISHED)
  		pipe_grant_credits(sk, GFP_ATOMIC);
  	return skb;
  }
  
  static int pep_recvmsg(struct kiocb *iocb, struct sock *sk,
  			struct msghdr *msg, size_t len, int noblock,
  			int flags, int *addr_len)
  {
  	struct sk_buff *skb;
  	int err;
  
  	if (flags & ~(MSG_OOB|MSG_PEEK|MSG_TRUNC|MSG_DONTWAIT|MSG_WAITALL|
  			MSG_NOSIGNAL|MSG_CMSG_COMPAT))
  		return -EOPNOTSUPP;
  
  	if (unlikely(1 << sk->sk_state & (TCPF_LISTEN | TCPF_CLOSE)))
  		return -ENOTCONN;
  
  	if ((flags & MSG_OOB) || sock_flag(sk, SOCK_URGINLINE)) {
  		/* Dequeue and acknowledge control request */
  		struct pep_sock *pn = pep_sk(sk);
  
  		if (flags & MSG_PEEK)
  			return -EOPNOTSUPP;
  		skb = skb_dequeue(&pn->ctrlreq_queue);
  		if (skb) {
  			pep_ctrlreq_error(sk, skb, PN_PIPE_NO_ERROR,
  						GFP_KERNEL);
  			msg->msg_flags |= MSG_OOB;
  			goto copy;
  		}
  		if (flags & MSG_OOB)
  			return -EINVAL;
  	}
  
  	skb = skb_recv_datagram(sk, flags, noblock, &err);
  	lock_sock(sk);
  	if (skb == NULL) {
  		if (err == -ENOTCONN && sk->sk_state == TCP_CLOSE_WAIT)
  			err = -ECONNRESET;
  		release_sock(sk);
  		return err;
  	}
  
  	if (sk->sk_state == TCP_ESTABLISHED)
  		pipe_grant_credits(sk, GFP_KERNEL);
  	release_sock(sk);
  copy:
  	msg->msg_flags |= MSG_EOR;
  	if (skb->len > len)
  		msg->msg_flags |= MSG_TRUNC;
  	else
  		len = skb->len;
  
  	err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, len);
  	if (!err)
  		err = (flags & MSG_TRUNC) ? skb->len : len;
  
  	skb_free_datagram(sk, skb);
  	return err;
  }
  
  static void pep_sock_unhash(struct sock *sk)
  {
  	struct pep_sock *pn = pep_sk(sk);
  	struct sock *skparent = NULL;
  
  	lock_sock(sk);
  
  	if (pn->listener != NULL) {
  		skparent = pn->listener;
  		pn->listener = NULL;
  		release_sock(sk);
  
  		pn = pep_sk(skparent);
  		lock_sock(skparent);
  		sk_del_node_init(sk);
  		sk = skparent;
  	}
  
  	/* Unhash a listening sock only when it is closed
  	 * and all of its active connected pipes are closed. */
  	if (hlist_empty(&pn->hlist))
  		pn_sock_unhash(&pn->pn_sk.sk);
  	release_sock(sk);
  
  	if (skparent)
  		sock_put(skparent);
  }
  
  static struct proto pep_proto = {
  	.close		= pep_sock_close,
  	.accept		= pep_sock_accept,
  	.connect	= pep_sock_connect,
  	.ioctl		= pep_ioctl,
  	.init		= pep_init,
  	.setsockopt	= pep_setsockopt,
  	.getsockopt	= pep_getsockopt,
  	.sendmsg	= pep_sendmsg,
  	.recvmsg	= pep_recvmsg,
  	.backlog_rcv	= pep_do_rcv,
  	.hash		= pn_sock_hash,
  	.unhash		= pep_sock_unhash,
  	.get_port	= pn_sock_get_port,
  	.obj_size	= sizeof(struct pep_sock),
  	.owner		= THIS_MODULE,
  	.name		= "PNPIPE",
  };
  
  static struct phonet_protocol pep_pn_proto = {
  	.ops		= &phonet_stream_ops,
  	.prot		= &pep_proto,
  	.sock_type	= SOCK_SEQPACKET,
  };
  
  static int __init pep_register(void)
  {
  	return phonet_proto_register(PN_PROTO_PIPE, &pep_pn_proto);
  }
  
  static void __exit pep_unregister(void)
  {
  	phonet_proto_unregister(PN_PROTO_PIPE, &pep_pn_proto);
  }
  
  module_init(pep_register);
  module_exit(pep_unregister);
  MODULE_AUTHOR("Remi Denis-Courmont, Nokia");
  MODULE_DESCRIPTION("Phonet pipe protocol");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_NET_PF_PROTO(PF_PHONET, PN_PROTO_PIPE);