/*
   * Generic HDLC support routines for Linux
   * Point-to-point protocol support
   *

   * Copyright (C) 1999 - 2008 Krzysztof Halasa <khc@pm.waw.pl>

   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of version 2 of the GNU General Public License
   * as published by the Free Software Foundation.
   */

  #include <linux/errno.h>

  #include <linux/hdlc.h>

  #include <linux/if_arp.h>

  #include <linux/inetdevice.h>

  #include <linux/init.h>

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

  #include <linux/pkt_sched.h>

  #include <linux/poll.h>

  #include <linux/skbuff.h>
  #include <linux/slab.h>

  #include <linux/spinlock.h>
  
  #define DEBUG_CP		0 /* also bytes# to dump */
  #define DEBUG_STATE		0
  #define DEBUG_HARD_HEADER	0
  
  #define HDLC_ADDR_ALLSTATIONS	0xFF
  #define HDLC_CTRL_UI		0x03
  
  #define PID_LCP			0xC021
  #define PID_IP			0x0021
  #define PID_IPCP		0x8021
  #define PID_IPV6		0x0057
  #define PID_IPV6CP		0x8057
  
  enum {IDX_LCP = 0, IDX_IPCP, IDX_IPV6CP, IDX_COUNT};
  enum {CP_CONF_REQ = 1, CP_CONF_ACK, CP_CONF_NAK, CP_CONF_REJ, CP_TERM_REQ,
        CP_TERM_ACK, CP_CODE_REJ, LCP_PROTO_REJ, LCP_ECHO_REQ, LCP_ECHO_REPLY,
        LCP_DISC_REQ, CP_CODES};
  #if DEBUG_CP
  static const char *const code_names[CP_CODES] = {
  	"0", "ConfReq", "ConfAck", "ConfNak", "ConfRej", "TermReq",
  	"TermAck", "CodeRej", "ProtoRej", "EchoReq", "EchoReply", "Discard"
  };
  static char debug_buffer[64 + 3 * DEBUG_CP];
  #endif
  
  enum {LCP_OPTION_MRU = 1, LCP_OPTION_ACCM, LCP_OPTION_MAGIC = 5};
  
  struct hdlc_header {
  	u8 address;
  	u8 control;
  	__be16 protocol;
  };
  
  struct cp_header {
  	u8 code;
  	u8 id;
  	__be16 len;
  };

  struct proto {
  	struct net_device *dev;
  	struct timer_list timer;
  	unsigned long timeout;
  	u16 pid;		/* protocol ID */
  	u8 state;
  	u8 cr_id;		/* ID of last Configuration-Request */
  	u8 restart_counter;

  };

  struct ppp {
  	struct proto protos[IDX_COUNT];
  	spinlock_t lock;
  	unsigned long last_pong;
  	unsigned int req_timeout, cr_retries, term_retries;
  	unsigned int keepalive_interval, keepalive_timeout;
  	u8 seq;			/* local sequence number for requests */
  	u8 echo_id;		/* ID of last Echo-Request (LCP) */
  };
  
  enum {CLOSED = 0, STOPPED, STOPPING, REQ_SENT, ACK_RECV, ACK_SENT, OPENED,
        STATES, STATE_MASK = 0xF};
  enum {START = 0, STOP, TO_GOOD, TO_BAD, RCR_GOOD, RCR_BAD, RCA, RCN, RTR, RTA,
        RUC, RXJ_GOOD, RXJ_BAD, EVENTS};
  enum {INV = 0x10, IRC = 0x20, ZRC = 0x40, SCR = 0x80, SCA = 0x100,
        SCN = 0x200, STR = 0x400, STA = 0x800, SCJ = 0x1000};
  
  #if DEBUG_STATE
  static const char *const state_names[STATES] = {
  	"Closed", "Stopped", "Stopping", "ReqSent", "AckRecv", "AckSent",
  	"Opened"
  };
  static const char *const event_names[EVENTS] = {
  	"Start", "Stop", "TO+", "TO-", "RCR+", "RCR-", "RCA", "RCN",
  	"RTR", "RTA", "RUC", "RXJ+", "RXJ-"
  };
  #endif
  
  static struct sk_buff_head tx_queue; /* used when holding the spin lock */

  static int ppp_ioctl(struct net_device *dev, struct ifreq *ifr);

  static inline struct ppp* get_ppp(struct net_device *dev)
  {
  	return (struct ppp *)dev_to_hdlc(dev)->state;
  }

  static inline struct proto* get_proto(struct net_device *dev, u16 pid)

  {

  	struct ppp *ppp = get_ppp(dev);
  
  	switch (pid) {
  	case PID_LCP:
  		return &ppp->protos[IDX_LCP];
  	case PID_IPCP:
  		return &ppp->protos[IDX_IPCP];
  	case PID_IPV6CP:
  		return &ppp->protos[IDX_IPV6CP];
  	default:
  		return NULL;
  	}

  }

  static inline const char* proto_name(u16 pid)
  {
  	switch (pid) {
  	case PID_LCP:
  		return "LCP";
  	case PID_IPCP:
  		return "IPCP";
  	case PID_IPV6CP:
  		return "IPV6CP";
  	default:
  		return NULL;
  	}
  }

  static __be16 ppp_type_trans(struct sk_buff *skb, struct net_device *dev)

  {

  	struct hdlc_header *data = (struct hdlc_header*)skb->data;
  
  	if (skb->len < sizeof(struct hdlc_header))
  		return htons(ETH_P_HDLC);
  	if (data->address != HDLC_ADDR_ALLSTATIONS ||
  	    data->control != HDLC_CTRL_UI)
  		return htons(ETH_P_HDLC);
  
  	switch (data->protocol) {

  	case cpu_to_be16(PID_IP):

  		skb_pull(skb, sizeof(struct hdlc_header));
  		return htons(ETH_P_IP);

  	case cpu_to_be16(PID_IPV6):

  		skb_pull(skb, sizeof(struct hdlc_header));
  		return htons(ETH_P_IPV6);

  	default:
  		return htons(ETH_P_HDLC);

  	}

  }

  
  static int ppp_hard_header(struct sk_buff *skb, struct net_device *dev,
  			   u16 type, const void *daddr, const void *saddr,
  			   unsigned int len)
  {
  	struct hdlc_header *data;
  #if DEBUG_HARD_HEADER
  	printk(KERN_DEBUG "%s: ppp_hard_header() called
  ", dev->name);
  #endif
  
  	skb_push(skb, sizeof(struct hdlc_header));
  	data = (struct hdlc_header*)skb->data;
  
  	data->address = HDLC_ADDR_ALLSTATIONS;
  	data->control = HDLC_CTRL_UI;
  	switch (type) {
  	case ETH_P_IP:
  		data->protocol = htons(PID_IP);
  		break;
  	case ETH_P_IPV6:
  		data->protocol = htons(PID_IPV6);
  		break;
  	case PID_LCP:
  	case PID_IPCP:
  	case PID_IPV6CP:
  		data->protocol = htons(type);
  		break;
  	default:		/* unknown protocol */
  		data->protocol = 0;
  	}
  	return sizeof(struct hdlc_header);

  }

  static void ppp_tx_flush(void)
  {
  	struct sk_buff *skb;
  	while ((skb = skb_dequeue(&tx_queue)) != NULL)
  		dev_queue_xmit(skb);
  }

  static void ppp_tx_cp(struct net_device *dev, u16 pid, u8 code,
  		      u8 id, unsigned int len, const void *data)

  {

  	struct sk_buff *skb;
  	struct cp_header *cp;
  	unsigned int magic_len = 0;
  	static u32 magic;
  
  #if DEBUG_CP
  	int i;
  	char *ptr;
  #endif
  
  	if (pid == PID_LCP && (code == LCP_ECHO_REQ || code == LCP_ECHO_REPLY))
  		magic_len = sizeof(magic);
  
  	skb = dev_alloc_skb(sizeof(struct hdlc_header) +
  			    sizeof(struct cp_header) + magic_len + len);
  	if (!skb) {
  		printk(KERN_WARNING "%s: out of memory in ppp_tx_cp()
  ",
  		       dev->name);
  		return;
  	}
  	skb_reserve(skb, sizeof(struct hdlc_header));
  
  	cp = (struct cp_header *)skb_put(skb, sizeof(struct cp_header));
  	cp->code = code;
  	cp->id = id;
  	cp->len = htons(sizeof(struct cp_header) + magic_len + len);
  
  	if (magic_len)
  		memcpy(skb_put(skb, magic_len), &magic, magic_len);
  	if (len)
  		memcpy(skb_put(skb, len), data, len);
  
  #if DEBUG_CP
  	BUG_ON(code >= CP_CODES);
  	ptr = debug_buffer;
  	*ptr = '\x0';
  	for (i = 0; i < min_t(unsigned int, magic_len + len, DEBUG_CP); i++) {
  		sprintf(ptr, " %02X", skb->data[sizeof(struct cp_header) + i]);
  		ptr += strlen(ptr);
  	}
  	printk(KERN_DEBUG "%s: TX %s [%s id 0x%X]%s
  ", dev->name,
  	       proto_name(pid), code_names[code], id, debug_buffer);
  #endif

  	ppp_hard_header(skb, dev, pid, NULL, NULL, 0);

  	skb->priority = TC_PRIO_CONTROL;
  	skb->dev = dev;
  	skb_reset_network_header(skb);
  	skb_queue_tail(&tx_queue, skb);

  }

  /* State transition table (compare STD-51)
     Events                                   Actions
     TO+  = Timeout with counter > 0          irc = Initialize-Restart-Count
     TO-  = Timeout with counter expired      zrc = Zero-Restart-Count
  
     RCR+ = Receive-Configure-Request (Good)  scr = Send-Configure-Request
     RCR- = Receive-Configure-Request (Bad)
     RCA  = Receive-Configure-Ack             sca = Send-Configure-Ack
     RCN  = Receive-Configure-Nak/Rej         scn = Send-Configure-Nak/Rej
  
     RTR  = Receive-Terminate-Request         str = Send-Terminate-Request
     RTA  = Receive-Terminate-Ack             sta = Send-Terminate-Ack
  
     RUC  = Receive-Unknown-Code              scj = Send-Code-Reject
     RXJ+ = Receive-Code-Reject (permitted)
         or Receive-Protocol-Reject
     RXJ- = Receive-Code-Reject (catastrophic)
         or Receive-Protocol-Reject
  */
  static int cp_table[EVENTS][STATES] = {
  	/* CLOSED     STOPPED STOPPING REQ_SENT ACK_RECV ACK_SENT OPENED
  	     0           1         2       3       4      5          6    */
  	{IRC|SCR|3,     INV     , INV ,   INV   , INV ,  INV    ,   INV   }, /* START */
  	{   INV   ,      0      ,  0  ,    0    ,  0  ,   0     ,    0    }, /* STOP */
  	{   INV   ,     INV     ,STR|2,  SCR|3  ,SCR|3,  SCR|5  ,   INV   }, /* TO+ */
  	{   INV   ,     INV     ,  1  ,    1    ,  1  ,    1    ,   INV   }, /* TO- */
  	{  STA|0  ,IRC|SCR|SCA|5,  2  ,  SCA|5  ,SCA|6,  SCA|5  ,SCR|SCA|5}, /* RCR+ */
  	{  STA|0  ,IRC|SCR|SCN|3,  2  ,  SCN|3  ,SCN|4,  SCN|3  ,SCR|SCN|3}, /* RCR- */
  	{  STA|0  ,    STA|1    ,  2  ,  IRC|4  ,SCR|3,    6    , SCR|3   }, /* RCA */
  	{  STA|0  ,    STA|1    ,  2  ,IRC|SCR|3,SCR|3,IRC|SCR|5, SCR|3   }, /* RCN */
  	{  STA|0  ,    STA|1    ,STA|2,  STA|3  ,STA|3,  STA|3  ,ZRC|STA|2}, /* RTR */
  	{    0    ,      1      ,  1  ,    3    ,  3  ,    5    ,  SCR|3  }, /* RTA */
  	{  SCJ|0  ,    SCJ|1    ,SCJ|2,  SCJ|3  ,SCJ|4,  SCJ|5  ,  SCJ|6  }, /* RUC */
  	{    0    ,      1      ,  2  ,    3    ,  3  ,    5    ,    6    }, /* RXJ+ */
  	{    0    ,      1      ,  1  ,    1    ,  1  ,    1    ,IRC|STR|2}, /* RXJ- */
  };

  /* SCA: RCR+ must supply id, len and data
     SCN: RCR- must supply code, id, len and data
     STA: RTR must supply id
     SCJ: RUC must supply CP packet len and data */
  static void ppp_cp_event(struct net_device *dev, u16 pid, u16 event, u8 code,

  			 u8 id, unsigned int len, const void *data)

  {

  	int old_state, action;
  	struct ppp *ppp = get_ppp(dev);
  	struct proto *proto = get_proto(dev, pid);
  
  	old_state = proto->state;
  	BUG_ON(old_state >= STATES);
  	BUG_ON(event >= EVENTS);
  
  #if DEBUG_STATE
  	printk(KERN_DEBUG "%s: %s ppp_cp_event(%s) %s ...
  ", dev->name,
  	       proto_name(pid), event_names[event], state_names[proto->state]);
  #endif
  
  	action = cp_table[event][old_state];
  
  	proto->state = action & STATE_MASK;
  	if (action & (SCR | STR)) /* set Configure-Req/Terminate-Req timer */
  		mod_timer(&proto->timer, proto->timeout =
  			  jiffies + ppp->req_timeout * HZ);
  	if (action & ZRC)
  		proto->restart_counter = 0;
  	if (action & IRC)
  		proto->restart_counter = (proto->state == STOPPING) ?
  			ppp->term_retries : ppp->cr_retries;
  
  	if (action & SCR)	/* send Configure-Request */
  		ppp_tx_cp(dev, pid, CP_CONF_REQ, proto->cr_id = ++ppp->seq,
  			  0, NULL);
  	if (action & SCA)	/* send Configure-Ack */
  		ppp_tx_cp(dev, pid, CP_CONF_ACK, id, len, data);
  	if (action & SCN)	/* send Configure-Nak/Reject */
  		ppp_tx_cp(dev, pid, code, id, len, data);
  	if (action & STR)	/* send Terminate-Request */
  		ppp_tx_cp(dev, pid, CP_TERM_REQ, ++ppp->seq, 0, NULL);
  	if (action & STA)	/* send Terminate-Ack */
  		ppp_tx_cp(dev, pid, CP_TERM_ACK, id, 0, NULL);
  	if (action & SCJ)	/* send Code-Reject */
  		ppp_tx_cp(dev, pid, CP_CODE_REJ, ++ppp->seq, len, data);
  
  	if (old_state != OPENED && proto->state == OPENED) {
  		printk(KERN_INFO "%s: %s up
  ", dev->name, proto_name(pid));
  		if (pid == PID_LCP) {
  			netif_dormant_off(dev);
  			ppp_cp_event(dev, PID_IPCP, START, 0, 0, 0, NULL);
  			ppp_cp_event(dev, PID_IPV6CP, START, 0, 0, 0, NULL);
  			ppp->last_pong = jiffies;
  			mod_timer(&proto->timer, proto->timeout =
  				  jiffies + ppp->keepalive_interval * HZ);
  		}
  	}
  	if (old_state == OPENED && proto->state != OPENED) {
  		printk(KERN_INFO "%s: %s down
  ", dev->name, proto_name(pid));
  		if (pid == PID_LCP) {
  			netif_dormant_on(dev);
  			ppp_cp_event(dev, PID_IPCP, STOP, 0, 0, 0, NULL);
  			ppp_cp_event(dev, PID_IPV6CP, STOP, 0, 0, 0, NULL);
  		}
  	}
  	if (old_state != CLOSED && proto->state == CLOSED)
  		del_timer(&proto->timer);
  
  #if DEBUG_STATE
  	printk(KERN_DEBUG "%s: %s ppp_cp_event(%s) ... %s
  ", dev->name,
  	       proto_name(pid), event_names[event], state_names[proto->state]);
  #endif

  }

  static void ppp_cp_parse_cr(struct net_device *dev, u16 pid, u8 id,

  			    unsigned int req_len, const u8 *data)

  {
  	static u8 const valid_accm[6] = { LCP_OPTION_ACCM, 6, 0, 0, 0, 0 };

  	const u8 *opt;
  	u8 *out;
  	unsigned int len = req_len, nak_len = 0, rej_len = 0;

  
  	if (!(out = kmalloc(len, GFP_ATOMIC))) {
  		dev->stats.rx_dropped++;
  		return;	/* out of memory, ignore CR packet */
  	}
  
  	for (opt = data; len; len -= opt[1], opt += opt[1]) {
  		if (len < 2 || len < opt[1]) {
  			dev->stats.rx_errors++;

  			kfree(out);

  			return; /* bad packet, drop silently */
  		}
  
  		if (pid == PID_LCP)
  			switch (opt[0]) {
  			case LCP_OPTION_MRU:
  				continue; /* MRU always OK and > 1500 bytes? */
  
  			case LCP_OPTION_ACCM: /* async control character map */
  				if (!memcmp(opt, valid_accm,
  					    sizeof(valid_accm)))
  					continue;
  				if (!rej_len) { /* NAK it */
  					memcpy(out + nak_len, valid_accm,
  					       sizeof(valid_accm));
  					nak_len += sizeof(valid_accm);
  					continue;
  				}
  				break;
  			case LCP_OPTION_MAGIC:
  				if (opt[1] != 6 || (!opt[2] && !opt[3] &&
  						    !opt[4] && !opt[5]))
  					break; /* reject invalid magic number */
  				continue;
  			}
  		/* reject this option */
  		memcpy(out + rej_len, opt, opt[1]);
  		rej_len += opt[1];
  	}
  
  	if (rej_len)
  		ppp_cp_event(dev, pid, RCR_BAD, CP_CONF_REJ, id, rej_len, out);
  	else if (nak_len)
  		ppp_cp_event(dev, pid, RCR_BAD, CP_CONF_NAK, id, nak_len, out);
  	else

  		ppp_cp_event(dev, pid, RCR_GOOD, CP_CONF_ACK, id, req_len, data);

  
  	kfree(out);
  }
  
  static int ppp_rx(struct sk_buff *skb)
  {
  	struct hdlc_header *hdr = (struct hdlc_header*)skb->data;
  	struct net_device *dev = skb->dev;
  	struct ppp *ppp = get_ppp(dev);
  	struct proto *proto;
  	struct cp_header *cp;
  	unsigned long flags;
  	unsigned int len;
  	u16 pid;
  #if DEBUG_CP
  	int i;
  	char *ptr;
  #endif
  
  	spin_lock_irqsave(&ppp->lock, flags);
  	/* Check HDLC header */
  	if (skb->len < sizeof(struct hdlc_header))
  		goto rx_error;
  	cp = (struct cp_header*)skb_pull(skb, sizeof(struct hdlc_header));
  	if (hdr->address != HDLC_ADDR_ALLSTATIONS ||
  	    hdr->control != HDLC_CTRL_UI)
  		goto rx_error;
  
  	pid = ntohs(hdr->protocol);
  	proto = get_proto(dev, pid);
  	if (!proto) {
  		if (ppp->protos[IDX_LCP].state == OPENED)
  			ppp_tx_cp(dev, PID_LCP, LCP_PROTO_REJ,
  				  ++ppp->seq, skb->len + 2, &hdr->protocol);
  		goto rx_error;
  	}
  
  	len = ntohs(cp->len);
  	if (len < sizeof(struct cp_header) /* no complete CP header? */ ||
  	    skb->len < len /* truncated packet? */)
  		goto rx_error;
  	skb_pull(skb, sizeof(struct cp_header));
  	len -= sizeof(struct cp_header);
  
  	/* HDLC and CP headers stripped from skb */
  #if DEBUG_CP
  	if (cp->code < CP_CODES)
  		sprintf(debug_buffer, "[%s id 0x%X]", code_names[cp->code],
  			cp->id);
  	else
  		sprintf(debug_buffer, "[code %u id 0x%X]", cp->code, cp->id);
  	ptr = debug_buffer + strlen(debug_buffer);
  	for (i = 0; i < min_t(unsigned int, len, DEBUG_CP); i++) {
  		sprintf(ptr, " %02X", skb->data[i]);
  		ptr += strlen(ptr);
  	}
  	printk(KERN_DEBUG "%s: RX %s %s
  ", dev->name, proto_name(pid),
  	       debug_buffer);
  #endif
  
  	/* LCP only */
  	if (pid == PID_LCP)
  		switch (cp->code) {
  		case LCP_PROTO_REJ:
  			pid = ntohs(*(__be16*)skb->data);
  			if (pid == PID_LCP || pid == PID_IPCP ||
  			    pid == PID_IPV6CP)
  				ppp_cp_event(dev, pid, RXJ_BAD, 0, 0,
  					     0, NULL);
  			goto out;
  
  		case LCP_ECHO_REQ: /* send Echo-Reply */
  			if (len >= 4 && proto->state == OPENED)
  				ppp_tx_cp(dev, PID_LCP, LCP_ECHO_REPLY,
  					  cp->id, len - 4, skb->data + 4);
  			goto out;
  
  		case LCP_ECHO_REPLY:
  			if (cp->id == ppp->echo_id)
  				ppp->last_pong = jiffies;
  			goto out;
  
  		case LCP_DISC_REQ: /* discard */
  			goto out;
  		}
  
  	/* LCP, IPCP and IPV6CP */
  	switch (cp->code) {
  	case CP_CONF_REQ:
  		ppp_cp_parse_cr(dev, pid, cp->id, len, skb->data);
  		goto out;
  
  	case CP_CONF_ACK:
  		if (cp->id == proto->cr_id)
  			ppp_cp_event(dev, pid, RCA, 0, 0, 0, NULL);
  		goto out;
  
  	case CP_CONF_REJ:
  	case CP_CONF_NAK:
  		if (cp->id == proto->cr_id)
  			ppp_cp_event(dev, pid, RCN, 0, 0, 0, NULL);
  		goto out;
  
  	case CP_TERM_REQ:
  		ppp_cp_event(dev, pid, RTR, 0, cp->id, 0, NULL);
  		goto out;
  
  	case CP_TERM_ACK:
  		ppp_cp_event(dev, pid, RTA, 0, 0, 0, NULL);
  		goto out;
  
  	case CP_CODE_REJ:
  		ppp_cp_event(dev, pid, RXJ_BAD, 0, 0, 0, NULL);
  		goto out;
  
  	default:
  		len += sizeof(struct cp_header);
  		if (len > dev->mtu)
  			len = dev->mtu;
  		ppp_cp_event(dev, pid, RUC, 0, 0, len, cp);
  		goto out;
  	}
  	goto out;
  
  rx_error:
  	dev->stats.rx_errors++;
  out:
  	spin_unlock_irqrestore(&ppp->lock, flags);
  	dev_kfree_skb_any(skb);
  	ppp_tx_flush();
  	return NET_RX_DROP;
  }

  static void ppp_timer(unsigned long arg)
  {
  	struct proto *proto = (struct proto *)arg;
  	struct ppp *ppp = get_ppp(proto->dev);
  	unsigned long flags;
  
  	spin_lock_irqsave(&ppp->lock, flags);
  	switch (proto->state) {
  	case STOPPING:
  	case REQ_SENT:
  	case ACK_RECV:
  	case ACK_SENT:
  		if (proto->restart_counter) {
  			ppp_cp_event(proto->dev, proto->pid, TO_GOOD, 0, 0,
  				     0, NULL);
  			proto->restart_counter--;
  		} else
  			ppp_cp_event(proto->dev, proto->pid, TO_BAD, 0, 0,
  				     0, NULL);
  		break;
  
  	case OPENED:
  		if (proto->pid != PID_LCP)
  			break;
  		if (time_after(jiffies, ppp->last_pong +
  			       ppp->keepalive_timeout * HZ)) {
  			printk(KERN_INFO "%s: Link down
  ", proto->dev->name);
  			ppp_cp_event(proto->dev, PID_LCP, STOP, 0, 0, 0, NULL);
  			ppp_cp_event(proto->dev, PID_LCP, START, 0, 0, 0, NULL);
  		} else {	/* send keep-alive packet */
  			ppp->echo_id = ++ppp->seq;
  			ppp_tx_cp(proto->dev, PID_LCP, LCP_ECHO_REQ,
  				  ppp->echo_id, 0, NULL);
  			proto->timer.expires = jiffies +
  				ppp->keepalive_interval * HZ;
  			add_timer(&proto->timer);
  		}
  		break;
  	}
  	spin_unlock_irqrestore(&ppp->lock, flags);
  	ppp_tx_flush();
  }
  
  
  static void ppp_start(struct net_device *dev)
  {
  	struct ppp *ppp = get_ppp(dev);
  	int i;
  
  	for (i = 0; i < IDX_COUNT; i++) {
  		struct proto *proto = &ppp->protos[i];
  		proto->dev = dev;
  		init_timer(&proto->timer);
  		proto->timer.function = ppp_timer;
  		proto->timer.data = (unsigned long)proto;
  		proto->state = CLOSED;
  	}
  	ppp->protos[IDX_LCP].pid = PID_LCP;
  	ppp->protos[IDX_IPCP].pid = PID_IPCP;
  	ppp->protos[IDX_IPV6CP].pid = PID_IPV6CP;
  
  	ppp_cp_event(dev, PID_LCP, START, 0, 0, 0, NULL);
  }
  
  static void ppp_stop(struct net_device *dev)
  {
  	ppp_cp_event(dev, PID_LCP, STOP, 0, 0, 0, NULL);
  }

  static struct hdlc_proto proto = {

  	.start		= ppp_start,
  	.stop		= ppp_stop,

  	.type_trans	= ppp_type_trans,
  	.ioctl		= ppp_ioctl,

  	.netif_rx	= ppp_rx,

  	.module		= THIS_MODULE,
  };

  static const struct header_ops ppp_header_ops = {
  	.create = ppp_hard_header,
  };

  
  static int ppp_ioctl(struct net_device *dev, struct ifreq *ifr)

  {
  	hdlc_device *hdlc = dev_to_hdlc(dev);

  	struct ppp *ppp;

  	int result;
  
  	switch (ifr->ifr_settings.type) {
  	case IF_GET_PROTO:

  		if (dev_to_hdlc(dev)->proto != &proto)
  			return -EINVAL;

  		ifr->ifr_settings.type = IF_PROTO_PPP;
  		return 0; /* return protocol only, no settable parameters */
  
  	case IF_PROTO_PPP:

  		if (!capable(CAP_NET_ADMIN))

  			return -EPERM;

  		if (dev->flags & IFF_UP)

  			return -EBUSY;
  
  		/* no settable parameters */

  		result = hdlc->attach(dev, ENCODING_NRZ,PARITY_CRC16_PR1_CCITT);

  		if (result)
  			return result;

  		result = attach_hdlc_protocol(dev, &proto, sizeof(struct ppp));

  		if (result)
  			return result;

  
  		ppp = get_ppp(dev);
  		spin_lock_init(&ppp->lock);
  		ppp->req_timeout = 2;
  		ppp->cr_retries = 10;
  		ppp->term_retries = 2;
  		ppp->keepalive_interval = 10;
  		ppp->keepalive_timeout = 60;

  		dev->hard_header_len = sizeof(struct hdlc_header);
  		dev->header_ops = &ppp_header_ops;

  		dev->type = ARPHRD_PPP;

  		netif_dormant_on(dev);

  		return 0;
  	}
  
  	return -EINVAL;
  }

  
  
  static int __init mod_init(void)
  {

  	skb_queue_head_init(&tx_queue);

  	register_hdlc_protocol(&proto);
  	return 0;
  }

  static void __exit mod_exit(void)
  {
  	unregister_hdlc_protocol(&proto);
  }
  
  
  module_init(mod_init);
  module_exit(mod_exit);
  
  MODULE_AUTHOR("Krzysztof Halasa <khc@pm.waw.pl>");
  MODULE_DESCRIPTION("PPP protocol support for generic HDLC");
  MODULE_LICENSE("GPL v2");