/*
 *	NET3:	A (fairly minimal) implementation of synchronous PPP for Linux
 *		as well as a CISCO HDLC implementation. See the copyright 
 *		message below for the original source.
 *
 *	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.
 *
 *	Note however. This code is also used in a different form by FreeBSD.
 *	Therefore when making any non OS specific change please consider
 *	contributing it back to the original author under the terms
 *	below in addition.
 *		-- Alan
 *
 *	Port for Linux-2.1 by Jan "Yenya" Kasprzak <kas@fi.muni.cz>
 */

/*
 * Synchronous PPP/Cisco link level subroutines.
 * Keepalive protocol implemented in both Cisco and PPP modes.
 *
 * Copyright (C) 1994 Cronyx Ltd.
 * Author: Serge Vakulenko, <vak@zebub.msk.su>
 *
 * This software is distributed with NO WARRANTIES, not even the implied
 * warranties for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Authors grant any other persons or organisations permission to use
 * or modify this software as long as this message is kept with the software,
 * all derivative works or modified versions.
 *
 * Version 1.9, Wed Oct  4 18:58:15 MSK 1995
 *
 * $Id: syncppp.c,v 1.18 2000/04/11 05:25:31 asj Exp $
 */
#undef DEBUG

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/route.h>
#include <linux/netdevice.h>
#include <linux/inetdevice.h>
#include <linux/random.h>
#include <linux/pkt_sched.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>

#include <net/syncppp.h>

#include <asm/byteorder.h>
#include <asm/uaccess.h>

#define MAXALIVECNT     6               /* max. alive packets */

#define PPP_ALLSTATIONS 0xff            /* All-Stations broadcast address */
#define PPP_UI          0x03            /* Unnumbered Information */
#define PPP_IP          0x0021          /* Internet Protocol */
#define PPP_ISO         0x0023          /* ISO OSI Protocol */
#define PPP_XNS         0x0025          /* Xerox NS Protocol */
#define PPP_IPX         0x002b          /* Novell IPX Protocol */
#define PPP_LCP         0xc021          /* Link Control Protocol */
#define PPP_IPCP        0x8021          /* Internet Protocol Control Protocol */

#define LCP_CONF_REQ    1               /* PPP LCP configure request */
#define LCP_CONF_ACK    2               /* PPP LCP configure acknowledge */
#define LCP_CONF_NAK    3               /* PPP LCP configure negative ack */
#define LCP_CONF_REJ    4               /* PPP LCP configure reject */
#define LCP_TERM_REQ    5               /* PPP LCP terminate request */
#define LCP_TERM_ACK    6               /* PPP LCP terminate acknowledge */
#define LCP_CODE_REJ    7               /* PPP LCP code reject */
#define LCP_PROTO_REJ   8               /* PPP LCP protocol reject */
#define LCP_ECHO_REQ    9               /* PPP LCP echo request */
#define LCP_ECHO_REPLY  10              /* PPP LCP echo reply */
#define LCP_DISC_REQ    11              /* PPP LCP discard request */

#define LCP_OPT_MRU             1       /* maximum receive unit */
#define LCP_OPT_ASYNC_MAP       2       /* async control character map */
#define LCP_OPT_AUTH_PROTO      3       /* authentication protocol */
#define LCP_OPT_QUAL_PROTO      4       /* quality protocol */
#define LCP_OPT_MAGIC           5       /* magic number */
#define LCP_OPT_RESERVED        6       /* reserved */
#define LCP_OPT_PROTO_COMP      7       /* protocol field compression */
#define LCP_OPT_ADDR_COMP       8       /* address/control field compression */

#define IPCP_CONF_REQ   LCP_CONF_REQ    /* PPP IPCP configure request */
#define IPCP_CONF_ACK   LCP_CONF_ACK    /* PPP IPCP configure acknowledge */
#define IPCP_CONF_NAK   LCP_CONF_NAK    /* PPP IPCP configure negative ack */
#define IPCP_CONF_REJ   LCP_CONF_REJ    /* PPP IPCP configure reject */
#define IPCP_TERM_REQ   LCP_TERM_REQ    /* PPP IPCP terminate request */
#define IPCP_TERM_ACK   LCP_TERM_ACK    /* PPP IPCP terminate acknowledge */
#define IPCP_CODE_REJ   LCP_CODE_REJ    /* PPP IPCP code reject */

#define CISCO_MULTICAST         0x8f    /* Cisco multicast address */
#define CISCO_UNICAST           0x0f    /* Cisco unicast address */
#define CISCO_KEEPALIVE         0x8035  /* Cisco keepalive protocol */
#define CISCO_ADDR_REQ          0       /* Cisco address request */
#define CISCO_ADDR_REPLY        1       /* Cisco address reply */
#define CISCO_KEEPALIVE_REQ     2       /* Cisco keepalive request */

struct ppp_header {
	u8 address;
	u8 control;
	u16 protocol;
};
#define PPP_HEADER_LEN          sizeof (struct ppp_header)

struct lcp_header {
	u8 type;
	u8 ident;
	u16 len;
};
#define LCP_HEADER_LEN          sizeof (struct lcp_header)

struct cisco_packet {
	u32 type;
	u32 par1;
	u32 par2;
	u16 rel;
	u16 time0;
	u16 time1;
};
#define CISCO_PACKET_LEN 18
#define CISCO_BIG_PACKET_LEN 20

static struct sppp *spppq;
static struct timer_list sppp_keepalive_timer;
static DEFINE_SPINLOCK(spppq_lock);

/* global xmit queue for sending packets while spinlock is held */
static struct sk_buff_head tx_queue;

static void sppp_keepalive (unsigned long dummy);
static void sppp_cp_send (struct sppp *sp, u16 proto, u8 type,
	u8 ident, u16 len, void *data);
static void sppp_cisco_send (struct sppp *sp, int type, long par1, long par2);
static void sppp_lcp_input (struct sppp *sp, struct sk_buff *m);
static void sppp_cisco_input (struct sppp *sp, struct sk_buff *m);
static void sppp_ipcp_input (struct sppp *sp, struct sk_buff *m);
static void sppp_lcp_open (struct sppp *sp);
static void sppp_ipcp_open (struct sppp *sp);
static int sppp_lcp_conf_parse_options (struct sppp *sp, struct lcp_header *h,
	int len, u32 *magic);
static void sppp_cp_timeout (unsigned long arg);
static char *sppp_lcp_type_name (u8 type);
static char *sppp_ipcp_type_name (u8 type);
static void sppp_print_bytes (u8 *p, u16 len);

static int debug;

/* Flush global outgoing packet queue to dev_queue_xmit().
 *
 * dev_queue_xmit() must be called with interrupts enabled
 * which means it can't be called with spinlocks held.
 * If a packet needs to be sent while a spinlock is held,
 * then put the packet into tx_queue, and call sppp_flush_xmit()
 * after spinlock is released.
 */
static void sppp_flush_xmit(void)
{
	struct sk_buff *skb;
	while ((skb = skb_dequeue(&tx_queue)) != NULL)
		dev_queue_xmit(skb);
}

/*
 *	Interface down stub
 */	

static void if_down(struct net_device *dev)
{
	struct sppp *sp = (struct sppp *)sppp_of(dev);

	sp->pp_link_state=SPPP_LINK_DOWN;
}

/*
 * Timeout routine activations.
 */

static void sppp_set_timeout(struct sppp *p,int s) 
{
	if (! (p->pp_flags & PP_TIMO)) 
	{
		init_timer(&p->pp_timer);
		p->pp_timer.function=sppp_cp_timeout;
		p->pp_timer.expires=jiffies+s*HZ;
		p->pp_timer.data=(unsigned long)p;
		p->pp_flags |= PP_TIMO;
		add_timer(&p->pp_timer);
	}
}

static void sppp_clear_timeout(struct sppp *p)
{
	if (p->pp_flags & PP_TIMO) 
	{
		del_timer(&p->pp_timer);
		p->pp_flags &= ~PP_TIMO; 
	}
}

/**
 *	sppp_input -	receive and process a WAN PPP frame
 *	@skb:	The buffer to process
 *	@dev:	The device it arrived on
 *
 *	This can be called directly by cards that do not have
 *	timing constraints but is normally called from the network layer
 *	after interrupt servicing to process frames queued via netif_rx().
 *
 *	We process the options in the card. If the frame is destined for
 *	the protocol stacks then it requeues the frame for the upper level
 *	protocol. If it is a control from it is processed and discarded
 *	here.
 */
 
static void sppp_input (struct net_device *dev, struct sk_buff *skb)
{
	struct ppp_header *h;
	struct sppp *sp = (struct sppp *)sppp_of(dev);
	unsigned long flags;

	skb->dev=dev;
	skb->mac.raw=skb->data;

	if (dev->flags & IFF_RUNNING)
	{
		/* Count received bytes, add FCS and one flag */
		sp->ibytes+= skb->len + 3;
		sp->ipkts++;
	}

	if (!pskb_may_pull(skb, PPP_HEADER_LEN)) {
		/* Too small packet, drop it. */
		if (sp->pp_flags & PP_DEBUG)
			printk (KERN_DEBUG "%s: input packet is too small, %d bytes\n",
				dev->name, skb->len);
		kfree_skb(skb);
		return;
	}

	/* Get PPP header. */
	h = (struct ppp_header *)skb->data;
	skb_pull(skb,sizeof(struct ppp_header));

	spin_lock_irqsave(&sp->lock, flags);
	
	switch (h->address) {
	default:        /* Invalid PPP packet. */
		goto invalid;
	case PPP_ALLSTATIONS:
		if (h->control != PPP_UI)
			goto invalid;
		if (sp->pp_flags & PP_CISCO) {
			if (sp->pp_flags & PP_DEBUG)
				printk (KERN_WARNING "%s: PPP packet in Cisco mode <0x%x 0x%x 0x%x>\n",
					dev->name,
					h->address, h->control, ntohs (h->protocol));
			goto drop;
		}
		switch (ntohs (h->protocol)) {
		default:
			if (sp->lcp.state == LCP_STATE_OPENED)
				sppp_cp_send (sp, PPP_LCP, LCP_PROTO_REJ,
					++sp->pp_seq, skb->len + 2,
					&h->protocol);
			if (sp->pp_flags & PP_DEBUG)
				printk (KERN_WARNING "%s: invalid input protocol <0x%x 0x%x 0x%x>\n",
					dev->name,
					h->address, h->control, ntohs (h->protocol));
			goto drop;
		case PPP_LCP:
			sppp_lcp_input (sp, skb);
			goto drop;
		case PPP_IPCP:
			if (sp->lcp.state == LCP_STATE_OPENED)
				sppp_ipcp_input (sp, skb);
			else
				printk(KERN_DEBUG "IPCP when still waiting LCP finish.\n");
			goto drop;
		case PPP_IP:
			if (sp->ipcp.state == IPCP_STATE_OPENED) {
				if(sp->pp_flags&PP_DEBUG)
					printk(KERN_DEBUG "Yow an IP frame.\n");
				skb->protocol=htons(ETH_P_IP);
				netif_rx(skb);
				dev->last_rx = jiffies;
				goto done;
			}
			break;
#ifdef IPX
		case PPP_IPX:
			/* IPX IPXCP not implemented yet */
			if (sp->lcp.state == LCP_STATE_OPENED) {
				skb->protocol=htons(ETH_P_IPX);
				netif_rx(skb);
				dev->last_rx = jiffies;
				goto done;
			}
			break;
#endif
		}
		break;
	case CISCO_MULTICAST:
	case CISCO_UNICAST:
		/* Don't check the control field here (RFC 1547). */
		if (! (sp->pp_flags & PP_CISCO)) {
			if (sp->pp_flags & PP_DEBUG)
				printk (KERN_WARNING "%s: Cisco packet in PPP mode <0x%x 0x%x 0x%x>\n",
					dev->name,
					h->address, h->control, ntohs (h->protocol));
			goto drop;
		}
		switch (ntohs (h->protocol)) {
		default:
			goto invalid;
		case CISCO_KEEPALIVE:
			sppp_cisco_input (sp, skb);
			goto drop;
#ifdef CONFIG_INET
		case ETH_P_IP:
			skb->protocol=htons(ETH_P_IP);
			netif_rx(skb);
			dev->last_rx = jiffies;
			goto done;
#endif
#ifdef CONFIG_IPX
		case ETH_P_IPX:
			skb->protocol=htons(ETH_P_IPX);
			netif_rx(skb);
			dev->last_rx = jiffies;
			goto done;
#endif
		}
		break;
	}
	goto drop;

invalid:
	if (sp->pp_flags & PP_DEBUG)
		printk (KERN_WARNING "%s: invalid input packet <0x%x 0x%x 0x%x>\n",
			dev->name, h->address, h->control, ntohs (h->protocol));
drop:
	kfree_skb(skb);
done:
	spin_unlock_irqrestore(&sp->lock, flags);
	sppp_flush_xmit();
	return;
}

/*
 *	Handle transmit packets.
 */
 
static int sppp_hard_header(struct sk_buff *skb, struct net_device *dev, __u16 type,
		void *daddr, void *saddr, unsigned int len)
{
	struct sppp *sp = (struct sppp *)sppp_of(dev);
	struct ppp_header *h;
	skb_push(skb,sizeof(struct ppp_header));
	h=(struct ppp_header *)skb->data;
	if(sp->pp_flags&PP_CISCO)
	{
		h->address = CISCO_UNICAST;
		h->control = 0;
	}
	else
	{
		h->address = PPP_ALLSTATIONS;
		h->control = PPP_UI;
	}
	if(sp->pp_flags & PP_CISCO)
	{
		h->protocol = htons(type);
	}
	else switch(type)
	{
		case ETH_P_IP:
			h->protocol = htons(PPP_IP);
			break;
		case ETH_P_IPX:
			h->protocol = htons(PPP_IPX);
			break;
	}
	return sizeof(struct ppp_header);
}

static int sppp_rebuild_header(struct sk_buff *skb)
{
	return 0;
}

/*
 * Send keepalive packets, every 10 seconds.
 */

static void sppp_keepalive (unsigned long dummy)
{
	struct sppp *sp;
	unsigned long flags;

	spin_lock_irqsave(&spppq_lock, flags);

	for (sp=spppq; sp; sp=sp->pp_next) 
	{
		struct net_device *dev = sp->pp_if;

		/* Keepalive mode disabled or channel down? */
		if (! (sp->pp_flags & PP_KEEPALIVE) ||
		    ! (dev->flags & IFF_UP))
			continue;

		spin_lock(&sp->lock);

		/* No keepalive in PPP mode if LCP not opened yet. */
		if (! (sp->pp_flags & PP_CISCO) &&
		    sp->lcp.state != LCP_STATE_OPENED) {
			spin_unlock(&sp->lock);
			continue;
		}

		if (sp->pp_alivecnt == MAXALIVECNT) {
			/* No keepalive packets got.  Stop the interface. */
			printk (KERN_WARNING "%s: protocol down\n", dev->name);
			if_down (dev);
			if (! (sp->pp_flags & PP_CISCO)) {
				/* Shut down the PPP link. */
				sp->lcp.magic = jiffies;
				sp->lcp.state = LCP_STATE_CLOSED;
				sp->ipcp.state = IPCP_STATE_CLOSED;
				sppp_clear_timeout (sp);
				/* Initiate negotiation. */
				sppp_lcp_open (sp);
			}
		}
		if (sp->pp_alivecnt <= MAXALIVECNT)
			++sp->pp_alivecnt;
		if (sp->pp_flags & PP_CISCO)
			sppp_cisco_send (sp, CISCO_KEEPALIVE_REQ, ++sp->pp_seq,
				sp->pp_rseq);
		else if (sp->lcp.state == LCP_STATE_OPENED) {
			long nmagic = htonl (sp->lcp.magic);
			sp->lcp.echoid = ++sp->pp_seq;
			sppp_cp_send (sp, PPP_LCP, LCP_ECHO_REQ,
				sp->lcp.echoid, 4, &nmagic);
		}

		spin_unlock(&sp->lock);
	}