ipoe: initial implementation of kernel module

6 files changed, 1755 insertions, 0 deletions

diff --git a/drivers/pptp/CMakeLists.txt b/drivers/pptp/CMakeLists.txt
new file mode 100644
index 0000000..fd732e6
--- /dev/null
+++ b/drivers/pptp/CMakeLists.txt
@@ -0,0 +1,19 @@
+if (NOT DEFINED KDIR)
+	set(KDIR "/usr/src/linux")
+endif (NOT DEFINED KDIR)
+
+ADD_CUSTOM_COMMAND(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/driver/pptp.ko
+	COMMAND rm -rf ${CMAKE_CURRENT_BINARY_DIR}/driver
+	COMMAND mkdir ${CMAKE_CURRENT_BINARY_DIR}/driver
+	COMMAND ln -sf ${CMAKE_CURRENT_SOURCE_DIR}/* ${CMAKE_CURRENT_BINARY_DIR}/driver
+	COMMAND make -C ${KDIR} M=${CMAKE_CURRENT_BINARY_DIR}/driver modules
+	DEPENDS pptp.c
+)
+
+ADD_CUSTOM_TARGET(pptp_drv ALL
+	DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/driver/pptp.ko
+)
+
+IF (NOT DEFINED CPACK_TYPE)
+	INSTALL(CODE "EXECUTE_PROCESS(COMMAND make -C ${KDIR} M=${CMAKE_CURRENT_BINARY_DIR}/driver modules_install)")
+ENDIF (NOT DEFINED CPACK_TYPE)
diff --git a/drivers/pptp/Makefile b/drivers/pptp/Makefile
new file mode 100644
index 0000000..8ccbbed
--- /dev/null
+++ b/drivers/pptp/Makefile
@@ -0,0 +1,4 @@
+obj-m += pptp.o
+
+default:
+	make -C $(KDIR) M=$(PWD) modules
diff --git a/drivers/pptp/gre.c b/drivers/pptp/gre.c
new file mode 100644
index 0000000..77886d5
--- /dev/null
+++ b/drivers/pptp/gre.c
@@ -0,0 +1,220 @@
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/skbuff.h>
+#include <linux/in.h>
+#include <linux/netdevice.h>
+#include <linux/version.h>
+#include <linux/spinlock.h>
+#include <net/protocol.h>
+
+#include "gre.h"
+
+struct gre_protocol *gre_proto[GREPROTO_MAX] ____cacheline_aligned_in_smp;
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+static rwlock_t gre_proto_lock=RW_LOCK_UNLOCKED;
+#else
+static DEFINE_SPINLOCK(gre_proto_lock);
+#endif
+
+int gre_add_protocol(struct gre_protocol *proto, u8 version)
+{
+	int ret;
+
+	if (version >= GREPROTO_MAX)
+		return -EINVAL;
+	
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	write_lock_bh(&gre_proto_lock);
+#else
+	spin_lock(&gre_proto_lock);
+#endif
+	if (gre_proto[version]) {
+		ret = -EAGAIN;
+	} else {
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+		gre_proto[version] = proto;
+#else
+		rcu_assign_pointer(gre_proto[version], proto);
+#endif
+		ret = 0;
+	}
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	write_unlock_bh(&gre_proto_lock);
+#else
+	spin_unlock(&gre_proto_lock);
+#endif
+
+	return ret;
+}
+
+int gre_del_protocol(struct gre_protocol *proto, u8 version)
+{
+	if (version >= GREPROTO_MAX)
+		goto out_err;
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	write_lock_bh(&gre_proto_lock);
+#else
+	spin_lock(&gre_proto_lock);
+#endif
+	if (gre_proto[version] == proto)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+		gre_proto[version] = NULL;
+#else
+		rcu_assign_pointer(gre_proto[version], NULL);
+#endif
+	else
+		goto out_err_unlock;
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	write_unlock_bh(&gre_proto_lock);
+#else
+	spin_unlock(&gre_proto_lock);
+	synchronize_rcu();
+#endif
+	return 0;
+
+out_err_unlock:
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	write_unlock_bh(&gre_proto_lock);
+#else
+	spin_unlock(&gre_proto_lock);
+#endif
+out_err:
+	return -EINVAL;
+}
+
+static int gre_rcv(struct sk_buff *skb)
+{
+	u8 ver;
+	int ret;
+	struct gre_protocol *proto;
+
+	if (!pskb_may_pull(skb, 12))
+		goto drop_nolock;
+
+	ver = skb->data[1]&0x7f;
+	if (ver >= GREPROTO_MAX)
+		goto drop_nolock;
+	
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	read_lock(&gre_proto_lock);
+	proto = gre_proto[ver];
+#else
+	rcu_read_lock();
+	proto = rcu_dereference(gre_proto[ver]);
+#endif
+	if (!proto || !proto->handler)
+		goto drop;
+
+	ret = proto->handler(skb);
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	read_unlock(&gre_proto_lock);
+#else
+	rcu_read_unlock();
+#endif
+
+	return ret;
+
+drop:
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	read_unlock(&gre_proto_lock);
+#else
+	rcu_read_unlock();
+#endif
+drop_nolock:
+	kfree_skb(skb);
+	return NET_RX_DROP;
+}
+
+static void gre_err(struct sk_buff *skb, u32 info)
+{
+	u8 ver;
+	struct gre_protocol *proto;
+
+	if (!pskb_may_pull(skb, 12))
+		goto drop_nolock;
+
+	ver=skb->data[1]&0x7f;
+	if (ver>=GREPROTO_MAX)
+		goto drop_nolock;
+		
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	read_lock(&gre_proto_lock);
+	proto = gre_proto[ver];
+#else
+	rcu_read_lock();
+	proto = rcu_dereference(gre_proto[ver]);
+#endif
+	if (!proto || !proto->err_handler)
+		goto drop;
+
+	proto->err_handler(skb, info);
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	read_unlock(&gre_proto_lock);
+#else
+	rcu_read_unlock();
+#endif
+
+	return;
+
+drop:
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	read_unlock(&gre_proto_lock);
+#else
+	rcu_read_unlock();
+#endif
+drop_nolock:
+	kfree_skb(skb);
+}
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+static struct inet_protocol net_gre_protocol = {
+	.handler	= gre_rcv,
+	.err_handler	= gre_err,
+	.protocol	= IPPROTO_GRE,
+	.name		= "GRE",
+};
+#else
+static struct net_protocol net_gre_protocol = {
+	.handler	= gre_rcv,
+	.err_handler	= gre_err,
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,24)
+	.netns_ok=1,
+#endif
+};
+#endif
+
+static int __init gre_init(void)
+{
+	printk(KERN_INFO "GRE over IPv4 demultiplexor driver");
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	inet_add_protocol(&net_gre_protocol);
+#else
+	if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
+		printk(KERN_INFO "gre: can't add protocol\n");
+		return -EAGAIN;
+	}
+#endif
+	return 0;
+}
+
+static void __exit gre_exit(void)
+{
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	inet_del_protocol(&net_gre_protocol);
+#else
+	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
+#endif
+}
+
+module_init(gre_init);
+module_exit(gre_exit);
+
+MODULE_DESCRIPTION("GRE over IPv4 demultiplexor driver");
+MODULE_AUTHOR("Kozlov D. (xeb@mail.ru)");
+MODULE_LICENSE("GPL");
+EXPORT_SYMBOL_GPL(gre_add_protocol);
+EXPORT_SYMBOL_GPL(gre_del_protocol);
diff --git a/drivers/pptp/gre.h b/drivers/pptp/gre.h
new file mode 100644
index 0000000..2ca7f74
--- /dev/null
+++ b/drivers/pptp/gre.h
@@ -0,0 +1,18 @@
+#ifndef __LINUX_GRE_H
+#define __LINUX_GRE_H
+
+#include <linux/skbuff.h>
+
+#define GREPROTO_CISCO	0
+#define GREPROTO_PPTP		1
+#define GREPROTO_MAX		2
+
+struct gre_protocol {
+	int		(*handler)(struct sk_buff *skb);
+	void	(*err_handler)(struct sk_buff *skb, u32 info);
+};
+
+int gre_add_protocol(struct gre_protocol *proto, u8 version);
+int gre_del_protocol(struct gre_protocol *proto, u8 version);
+
+#endif
diff --git a/drivers/pptp/if_pppox.h b/drivers/pptp/if_pppox.h
new file mode 100644
index 0000000..bc05b53
--- /dev/null
+++ b/drivers/pptp/if_pppox.h
@@ -0,0 +1,222 @@
+/***************************************************************************
+ * Linux PPP over X - Generic PPP transport layer sockets
+ * Linux PPP over Ethernet (PPPoE) Socket Implementation (RFC 2516)
+ *
+ * This file supplies definitions required by the PPP over Ethernet driver
+ * (pppox.c).  All version information wrt this file is located in pppox.c
+ *
+ * License:
+ *		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.
+ *
+ */
+
+#ifndef __LINUX_IF_PPPOX_H
+#define __LINUX_IF_PPPOX_H
+
+
+#include <asm/types.h>
+#include <asm/byteorder.h>
+#include <linux/version.h>
+
+#ifdef  __KERNEL__
+#include <linux/in.h>
+#include <linux/if_ether.h>
+#include <linux/if.h>
+#include <linux/netdevice.h>
+#include <linux/ppp_channel.h>
+#endif /* __KERNEL__ */
+
+/* For user-space programs to pick up these definitions
+ * which they wouldn't get otherwise without defining __KERNEL__
+ */
+#ifndef AF_PPPOX
+#define AF_PPPOX	24
+#define PF_PPPOX	AF_PPPOX
+#endif /* !(AF_PPPOX) */
+
+/************************************************************************
+ * PPPoE addressing definition
+ */
+typedef __u16 sid_t;
+struct pppoe_addr{
+       sid_t           sid;                    /* Session identifier */
+       unsigned char   remote[ETH_ALEN];       /* Remote address */
+       char            dev[IFNAMSIZ];          /* Local device to use */
+};
+
+struct pptp_addr{
+       __u16           call_id;
+       struct in_addr  sin_addr;
+};
+/************************************************************************
+ * Protocols supported by AF_PPPOX
+ */
+#define PX_PROTO_OE    0 /* Currently just PPPoE */
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,22)
+#define PX_PROTO_PPTP  1
+#define PX_MAX_PROTO   2
+#else
+#define PX_PROTO_PPTP  2
+#define PX_MAX_PROTO   3
+#endif
+
+struct sockaddr_pppox {
+       sa_family_t     sa_family;            /* address family, AF_PPPOX */
+       unsigned int    sa_protocol;          /* protocol identifier */
+       union{
+               struct pppoe_addr       pppoe;
+	       			 struct pptp_addr        pptp;
+       }sa_addr;
+}__attribute__ ((packed));
+
+
+/*********************************************************************
+ *
+ * ioctl interface for defining forwarding of connections
+ *
+ ********************************************************************/
+
+#define PPPOEIOCSFWD	_IOW(0xB1 ,0, size_t)
+#define PPPOEIOCDFWD	_IO(0xB1 ,1)
+/*#define PPPOEIOCGFWD	_IOWR(0xB1,2, size_t)*/
+
+/* Codes to identify message types */
+#define PADI_CODE	0x09
+#define PADO_CODE	0x07
+#define PADR_CODE	0x19
+#define PADS_CODE	0x65
+#define PADT_CODE	0xa7
+struct pppoe_tag {
+	__u16 tag_type;
+	__u16 tag_len;
+	char tag_data[0];
+} __attribute ((packed));
+
+/* Tag identifiers */
+#define PTT_EOL		__constant_htons(0x0000)
+#define PTT_SRV_NAME	__constant_htons(0x0101)
+#define PTT_AC_NAME	__constant_htons(0x0102)
+#define PTT_HOST_UNIQ	__constant_htons(0x0103)
+#define PTT_AC_COOKIE	__constant_htons(0x0104)
+#define PTT_VENDOR 	__constant_htons(0x0105)
+#define PTT_RELAY_SID	__constant_htons(0x0110)
+#define PTT_SRV_ERR     __constant_htons(0x0201)
+#define PTT_SYS_ERR  	__constant_htons(0x0202)
+#define PTT_GEN_ERR  	__constant_htons(0x0203)
+
+struct pppoe_hdr {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+	__u8 ver : 4;
+	__u8 type : 4;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+	__u8 type : 4;
+	__u8 ver : 4;
+#else
+#error	"Please fix <asm/byteorder.h>"
+#endif
+	__u8 code;
+	__u16 sid;
+	__u16 length;
+	struct pppoe_tag tag[0];
+} __attribute__ ((packed));
+
+
+/* Socket options */
+#define PPTP_SO_TIMEOUT 1
+
+
+#ifdef __KERNEL__
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+struct pppoe_opt {
+	struct net_device      *dev;	  /* device associated with socket*/
+	struct pppoe_addr	pa;	  /* what this socket is bound to*/
+	struct sockaddr_pppox	relay;	  /* what socket data will be
+					     relayed to (PPPoE relaying) */
+};
+#endif
+struct pptp_opt {
+	struct pptp_addr	src_addr;
+	struct pptp_addr	dst_addr;
+	__u32 ack_sent, ack_recv;
+	__u32 seq_sent, seq_recv;
+	int ppp_flags;
+};
+#define PPTP_FLAG_PAUSE 0
+#define PPTP_FLAG_PROC 1
+
+#include <net/sock.h>
+
+struct pppox_sock {
+	/* struct sock must be the first member of pppox_sock */
+	#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	struct ppp_channel	chan;
+	struct sock		*sk;
+	#else
+	struct sock		sk;
+	struct ppp_channel	chan;
+	#endif
+	struct pppox_sock	*next;	  /* for hash table */
+	union {
+		struct pppoe_opt pppoe;
+		struct pptp_opt pptp;
+	} proto;
+	unsigned short		num;
+};
+#define pppoe_dev	proto.pppoe.dev
+#define pppoe_pa	proto.pppoe.pa
+#define pppoe_relay	proto.pppoe.relay
+
+static inline struct pppox_sock *pppox_sk(struct sock *sk)
+{
+	#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	return (struct pppox_sock *)sk->protinfo.pppox;
+	#else
+	return (struct pppox_sock *)sk;
+	#endif
+}
+
+static inline struct sock *sk_pppox(struct pppox_sock *po)
+{
+	#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	return po->sk;
+	#else
+	return (struct sock *)po;
+	#endif
+}
+
+struct module;
+
+struct pppox_proto {
+	#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,24)
+	int		(*create)(struct socket *sock);
+	#else
+	int		(*create)(struct net *net, struct socket *sock);
+	#endif
+	int		(*ioctl)(struct socket *sock, unsigned int cmd,
+				 unsigned long arg);
+  #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,15)
+	struct module	*owner;
+	#endif
+};
+
+extern int register_pppox_proto(int proto_num, struct pppox_proto *pp);
+extern void unregister_pppox_proto(int proto_num);
+extern void pppox_unbind_sock(struct sock *sk);/* delete ppp-channel binding */
+extern int pppox_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);
+
+/* PPPoX socket states */
+enum {
+    PPPOX_NONE		= 0,  /* initial state */
+    PPPOX_CONNECTED	= 1,  /* connection established ==TCP_ESTABLISHED */
+    PPPOX_BOUND		= 2,  /* bound to ppp device */
+    PPPOX_RELAY		= 4,  /* forwarding is enabled */
+    PPPOX_ZOMBIE	= 8,  /* dead, but still bound to ppp device */
+    PPPOX_DEAD		= 16  /* dead, useless, please clean me up!*/
+};
+
+#endif /* __KERNEL__ */
+
+#endif /* !(__LINUX_IF_PPPOX_H) */
diff --git a/drivers/pptp/pptp.c b/drivers/pptp/pptp.c
new file mode 100644
index 0000000..78853fc
--- /dev/null
+++ b/drivers/pptp/pptp.c
@@ -0,0 +1,1272 @@
+/*
+ *  Point-to-Point Tunneling Protocol for Linux
+ *
+ *	Authors: Kozlov D. (xeb@mail.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.
+ *
+ */
+
+#include <linux/string.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/netdevice.h>
+#include <linux/net.h>
+#include <linux/skbuff.h>
+#include <linux/init.h>
+#include <linux/ppp_channel.h>
+#include <linux/ppp_defs.h>
+#include "if_pppox.h"
+#include <linux/if_ppp.h>
+#include <linux/notifier.h>
+#include <linux/file.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/version.h>
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+#include <asm/bitops.h>
+#endif
+
+#include <net/sock.h>
+#include <net/protocol.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/route.h>
+
+#include <asm/uaccess.h>
+
+#define DEBUG
+//#define CONFIG_GRE
+
+#if defined(CONFIG_GRE) || defined(CONFIG_GRE_MODULE)
+#include "gre.h"
+#endif
+
+#define PPTP_DRIVER_VERSION "0.8.5"
+
+static int log_level=0;
+static int log_packets=10;
+
+#define MAX_CALLID 65535
+#define PPP_LCP_ECHOREQ 0x09
+#define PPP_LCP_ECHOREP 0x0A
+
+static DECLARE_BITMAP(callid_bitmap, MAX_CALLID + 1);
+static struct pppox_sock **callid_sock;
+
+#define SC_RCV_BITS	(SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+#define INIT_TIMER(_timer,_routine,_data) \
+do { \
+	(_timer)->function=_routine; \
+	(_timer)->data=_data; \
+	init_timer(_timer); \
+} while (0);
+
+static inline void *kzalloc(size_t size,int gfp)
+{
+	void *p=kmalloc(size,gfp);
+	memset(p,0,size);
+	return p;
+}
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,4,20)
+static inline void nf_reset(struct sk_buff *skb)
+{
+#ifdef CONFIG_NETFILTER
+	nf_conntrack_put(skb->nfct);
+	skb->nfct=NULL;
+#ifdef CONFIG_NETFILTER_DEBUG
+	skb->nf_debug=0;
+#endif
+#endif
+}
+#define __user
+#endif
+
+/**
+ * __ffs - find first bit in word.
+ * @word: The word to search
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+static inline unsigned long __ffs(unsigned long word)
+{
+	int num = 0;
+
+#if BITS_PER_LONG == 64
+	if ((word & 0xffffffff) == 0) {
+		num += 32;
+		word >>= 32;
+	}
+#endif
+	if ((word & 0xffff) == 0) {
+		num += 16;
+		word >>= 16;
+	}
+	if ((word & 0xff) == 0) {
+		num += 8;
+		word >>= 8;
+	}
+	if ((word & 0xf) == 0) {
+		num += 4;
+		word >>= 4;
+	}
+	if ((word & 0x3) == 0) {
+		num += 2;
+		word >>= 2;
+	}
+	if ((word & 0x1) == 0)
+		num += 1;
+	return num;
+}
+
+#define BITOP_WORD(nr)		((nr) / BITS_PER_LONG)
+/*
+ * Find the next set bit in a memory region.
+ */
+static unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
+			    unsigned long offset)
+{
+	const unsigned long *p = addr + BITOP_WORD(offset);
+	unsigned long result = offset & ~(BITS_PER_LONG-1);
+	unsigned long tmp;
+
+	if (offset >= size)
+		return size;
+	size -= result;
+	offset %= BITS_PER_LONG;
+	if (offset) {
+		tmp = *(p++);
+		tmp &= (~0UL << offset);
+		if (size < BITS_PER_LONG)
+			goto found_first;
+		if (tmp)
+			goto found_middle;
+		size -= BITS_PER_LONG;
+		result += BITS_PER_LONG;
+	}
+	while (size & ~(BITS_PER_LONG-1)) {
+		if ((tmp = *(p++)))
+			goto found_middle;
+		result += BITS_PER_LONG;
+		size -= BITS_PER_LONG;
+	}
+	if (!size)
+		return result;
+	tmp = *p;
+
+found_first:
+	tmp &= (~0UL >> (BITS_PER_LONG - size));
+	if (tmp == 0UL)		/* Are any bits set? */
+		return result + size;	/* Nope. */
+found_middle:
+	return result + __ffs(tmp);
+}
+#endif
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+static rwlock_t chan_lock=RW_LOCK_UNLOCKED;
+#define SK_STATE(sk) (sk)->state
+#else
+static DEFINE_SPINLOCK(chan_lock);
+#define SK_STATE(sk) (sk)->sk_state
+#endif
+
+static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb);
+static int pptp_ppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
+			   unsigned long arg);
+static int pptp_rcv_core(struct sock *sk,struct sk_buff *skb);
+
+static struct ppp_channel_ops pptp_chan_ops= {
+	.start_xmit = pptp_xmit,
+	.ioctl=pptp_ppp_ioctl,
+};
+
+
+#define MISSING_WINDOW 20
+#define WRAPPED( curseq, lastseq) \
+    ((((curseq) & 0xffffff00) == 0) && \
+     (((lastseq) & 0xffffff00 ) == 0xffffff00))
+
+/* gre header structure: -------------------------------------------- */
+
+#define PPTP_GRE_PROTO  0x880B
+#define PPTP_GRE_VER    0x1
+
+#define PPTP_GRE_FLAG_C	0x80
+#define PPTP_GRE_FLAG_R	0x40
+#define PPTP_GRE_FLAG_K	0x20
+#define PPTP_GRE_FLAG_S	0x10
+#define PPTP_GRE_FLAG_A	0x80
+
+#define PPTP_GRE_IS_C(f) ((f)&PPTP_GRE_FLAG_C)
+#define PPTP_GRE_IS_R(f) ((f)&PPTP_GRE_FLAG_R)
+#define PPTP_GRE_IS_K(f) ((f)&PPTP_GRE_FLAG_K)
+#define PPTP_GRE_IS_S(f) ((f)&PPTP_GRE_FLAG_S)
+#define PPTP_GRE_IS_A(f) ((f)&PPTP_GRE_FLAG_A)
+
+struct pptp_gre_header {
+  u8 flags;		/* bitfield */
+  u8 ver;			/* should be PPTP_GRE_VER (enhanced GRE) */
+  u16 protocol;		/* should be PPTP_GRE_PROTO (ppp-encaps) */
+  u16 payload_len;	/* size of ppp payload, not inc. gre header */
+  u16 call_id;		/* peer's call_id for this session */
+  u32 seq;		/* sequence number.  Present if S==1 */
+  u32 ack;		/* seq number of highest packet recieved by */
+  				/*  sender in this session */
+} __packed;
+#define PPTP_HEADER_OVERHEAD (2+sizeof(struct pptp_gre_header))
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+static struct pppox_sock * lookup_chan(u16 call_id, u32 s_addr)
+#else
+static struct pppox_sock * lookup_chan(u16 call_id, __be32 s_addr)
+#endif
+{
+	struct pppox_sock *sock;
+	struct pptp_opt *opt;
+
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	rcu_read_lock();
+	sock = rcu_dereference(callid_sock[call_id]);
+#else
+	read_lock(&chan_lock);
+	sock = callid_sock[call_id];
+#endif
+	if (sock) {
+		opt=&sock->proto.pptp;
+		if (opt->dst_addr.sin_addr.s_addr!=s_addr) sock=NULL;
+		else sock_hold(sk_pppox(sock));
+	}
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	rcu_read_unlock();
+#else
+	read_unlock(&chan_lock);
+#endif
+	
+	return sock;
+}
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+static int lookup_chan_dst(u16 call_id, u32 d_addr)
+#else
+static int lookup_chan_dst(u16 call_id, __be32 d_addr)
+#endif
+{
+	struct pppox_sock *sock;
+	struct pptp_opt *opt;
+	int i;
+	
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	rcu_read_lock();
+#else
+	down(&chan_lock);
+#endif
+	for(i = find_next_bit(callid_bitmap,MAX_CALLID,1); i < MAX_CALLID; 
+	                i = find_next_bit(callid_bitmap, MAX_CALLID, i + 1)){
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	    sock = rcu_dereference(callid_sock[i]);
+#else
+	    sock = callid_sock[i];
+#endif
+	    if (!sock)
+		continue;
+	    opt = &sock->proto.pptp;
+	    if (opt->dst_addr.call_id == call_id && opt->dst_addr.sin_addr.s_addr == d_addr) break;
+	}
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	rcu_read_unlock();
+#else
+	up(&chan_lock);
+#endif
+	
+	return i<MAX_CALLID;
+}
+
+static int add_chan(struct pppox_sock *sock)
+{
+	static int call_id=0;
+	int res=-1;
+
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	spin_lock(&chan_lock);
+#else
+	write_lock_bh(&chan_lock);
+#endif
+	
+	if (!sock->proto.pptp.src_addr.call_id)
+	{
+	    call_id=find_next_zero_bit(callid_bitmap,MAX_CALLID,call_id+1);
+	    if (call_id==MAX_CALLID)
+				call_id=find_next_zero_bit(callid_bitmap,MAX_CALLID,1);
+	    sock->proto.pptp.src_addr.call_id=call_id;
+	}
+	else if (test_bit(sock->proto.pptp.src_addr.call_id,callid_bitmap))
+		goto exit;
+	
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	rcu_assign_pointer(callid_sock[sock->proto.pptp.src_addr.call_id],sock);
+#else
+	callid_sock[sock->proto.pptp.src_addr.call_id] = sock;
+#endif
+	set_bit(sock->proto.pptp.src_addr.call_id,callid_bitmap);
+	res=0;
+
+exit:	
+	#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	spin_unlock(&chan_lock);
+	#else
+	write_unlock_bh(&chan_lock);
+	#endif
+
+	return res;
+}
+
+static void del_chan(struct pppox_sock *sock)
+{
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	spin_lock(&chan_lock);
+#else
+	write_lock_bh(&chan_lock);
+#endif
+	clear_bit(sock->proto.pptp.src_addr.call_id,callid_bitmap);
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	rcu_assign_pointer(callid_sock[sock->proto.pptp.src_addr.call_id],NULL);
+	spin_unlock(&chan_lock);
+	synchronize_rcu();
+#else
+	callid_sock[sock->proto.pptp.src_addr.call_id] = NULL;
+	write_unlock_bh(&chan_lock);
+#endif
+}
+
+static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
+{
+	struct sock *sk = (struct sock *) chan->private;
+	struct pppox_sock *po = pppox_sk(sk);
+	struct pptp_opt *opt=&po->proto.pptp;
+	struct pptp_gre_header *hdr;
+	unsigned int header_len=sizeof(*hdr);
+	int err=0;
+	int islcp;
+	int len;
+	unsigned char *data;
+	u32 seq_recv;
+	
+	
+	struct rtable *rt;     			/* Route to the other host */
+	struct net_device *tdev;			/* Device to other host */
+	struct iphdr  *iph;			/* Our new IP header */
+	int    max_headroom;			/* The extra header space needed */
+
+	if (SK_STATE(sk_pppox(po)) & PPPOX_DEAD)
+	    goto tx_error;
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	{
+		struct rt_key key = {
+			.dst=opt->dst_addr.sin_addr.s_addr,
+			.src=opt->src_addr.sin_addr.s_addr,
+			.tos=RT_TOS(0),
+		};
+		if ((err=ip_route_output_key(&rt, &key))) {
+			goto tx_error;
+		}
+	}
+#else
+	{
+		struct flowi fl = { .oif = 0,
+				    .nl_u = { .ip4_u =
+					      { .daddr = opt->dst_addr.sin_addr.s_addr,
+						.saddr = opt->src_addr.sin_addr.s_addr,
+						.tos = RT_TOS(0) } },
+				    .proto = IPPROTO_GRE };
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,25)
+		if ((err=ip_route_output_key(&rt, &fl))) {
+#else
+		if ((err=ip_route_output_key(&init_net,&rt, &fl))) {
+#endif
+			goto tx_error;
+		}
+	}
+#endif
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36)
+	tdev = rt->u.dst.dev;
+#else
+	tdev = rt->dst.dev;
+#endif
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	max_headroom = ((tdev->hard_header_len+15)&~15) + sizeof(*iph)+sizeof(*hdr)+2;
+#else
+	max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(*iph)+sizeof(*hdr)+2;
+#endif
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,22)
+	if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) {
+#else
+	if (skb_headroom(skb) < max_headroom || skb_shared(skb) ||
+		  (skb_cloned(skb) && !skb_clone_writable(skb,0))) {
+#endif
+ 		struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
+		if (!new_skb) {
+ 			ip_rt_put(rt);
+			goto tx_error;
+		}
+		if (skb->sk)
+		skb_set_owner_w(new_skb, skb->sk);
+		kfree_skb(skb);
+		skb = new_skb;
+	}
+
+	data=skb->data;
+	islcp=((data[0] << 8) + data[1])== PPP_LCP && 1 <= data[2] && data[2] <= 7;
+
+	/* compress protocol field */
+	if ((opt->ppp_flags & SC_COMP_PROT) && data[0]==0 && !islcp)
+		skb_pull(skb,1);
+
+	/*
+		* Put in the address/control bytes if necessary
+		*/
+	if ((opt->ppp_flags & SC_COMP_AC) == 0 || islcp) {
+		data=skb_push(skb,2);
+		data[0]=PPP_ALLSTATIONS;
+		data[1]=PPP_UI;
+	}
+	
+	len=skb->len;
+  
+	seq_recv = opt->seq_recv;
+  
+	if (opt->ack_sent == seq_recv) header_len-=sizeof(hdr->ack);
+
+	// Push down and install GRE header
+	skb_push(skb,header_len);
+	hdr=(struct pptp_gre_header *)(skb->data);
+
+	hdr->flags       = PPTP_GRE_FLAG_K;
+	hdr->ver         = PPTP_GRE_VER;
+	hdr->protocol    = htons(PPTP_GRE_PROTO);
+	hdr->call_id     = htons(opt->dst_addr.call_id);
+
+	hdr->flags |= PPTP_GRE_FLAG_S;
+	hdr->seq    = htonl(++opt->seq_sent);
+#ifdef DEBUG
+	if (log_level>=3 && opt->seq_sent<=log_packets)
+		printk(KERN_INFO"PPTP[%i]: send packet: seq=%i",opt->src_addr.call_id,opt->seq_sent);
+#endif
+	if (opt->ack_sent != seq_recv)	{
+	/* send ack with this message */
+		hdr->ver |= PPTP_GRE_FLAG_A;
+		hdr->ack  = htonl(seq_recv);
+		opt->ack_sent = seq_recv;
+#ifdef DEBUG
+		if (log_level>=3 && opt->seq_sent<=log_packets)
+			printk(" ack=%i",seq_recv);
+#endif
+	}
+	hdr->payload_len = htons(len);
+#ifdef DEBUG
+	if (log_level>=3 && opt->seq_sent<=log_packets)
+		printk("\n");
+#endif
+
+	/*
+	 *	Push down and install the IP header.
+	 */
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,31)
+	skb_reset_transport_header(skb);
+	skb_push(skb, sizeof(*iph));
+	skb_reset_network_header(skb);
+#elif LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
+	skb->transport_header = skb->network_header;
+	skb_push(skb, sizeof(*iph));
+	skb_reset_network_header(skb);
+#else
+	skb->h.raw = skb->nh.raw;
+	skb->nh.raw = skb_push(skb, sizeof(*iph));
+#endif
+	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,16)
+	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED |
+			      IPSKB_REROUTED);
+#endif
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
+	iph 			=	ip_hdr(skb);
+#else
+	iph 			=	skb->nh.iph;
+#endif
+	iph->version		=	4;
+	iph->ihl		=	sizeof(struct iphdr) >> 2;
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36)
+	if (ip_dont_fragment(sk, &rt->u.dst))
+#else
+	if (ip_dont_fragment(sk, &rt->dst))
+#endif
+		iph->frag_off	=	htons(IP_DF);
+	else
+		iph->frag_off	=	0;
+	iph->protocol		=	IPPROTO_GRE;
+	iph->tos		=	0;
+	iph->daddr		=	rt->rt_dst;
+	iph->saddr		=	rt->rt_src;
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	iph->ttl = sk->protinfo.af_inet.ttl;
+#else
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36)
+	iph->ttl = dst_metric(&rt->u.dst, RTAX_HOPLIMIT);
+#else
+	iph->ttl = dst_metric(&rt->dst, RTAX_HOPLIMIT);
+#endif
+#endif
+	iph->tot_len = htons(skb->len);
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,31)
+	skb_dst_drop(skb);
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36)
+	skb_dst_set(skb,&rt->u.dst);
+#else
+	skb_dst_set(skb,&rt->dst);
+#endif
+#else
+	dst_release(skb->dst);
+	skb->dst = &rt->u.dst;
+#endif
+
+	nf_reset(skb);
+
+	skb->ip_summed = CHECKSUM_NONE;
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36)
+	ip_select_ident(iph, &rt->u.dst, NULL);
+#else
+	ip_select_ident(iph, &rt->dst, NULL);
+#endif
+	ip_send_check(iph);
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+ 	err = NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev, ip_send);
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(2,6,25)
+ 	err = NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, skb, NULL, rt->u.dst.dev, dst_output);
+#else
+ 	err = ip_local_out(skb);
+#endif
+
+tx_error:
+	return 1;
+}
+
+static int pptp_rcv_core(struct sock *sk,struct sk_buff *skb)
+{
+	struct pppox_sock *po = pppox_sk(sk);
+	struct pptp_opt *opt=&po->proto.pptp;
+	int headersize,payload_len,seq;
+	u8 *payload;
+	struct pptp_gre_header *header;
+
+	if (!(SK_STATE(sk) & PPPOX_CONNECTED)) {
+		if (sock_queue_rcv_skb(sk, skb))
+			goto drop;
+		return NET_RX_SUCCESS;
+	}
+	
+	header = (struct pptp_gre_header *)(skb->data);
+
+	/* test if acknowledgement present */
+	if (PPTP_GRE_IS_A(header->ver)){
+			u32 ack = (PPTP_GRE_IS_S(header->flags))?
+					header->ack:header->seq; /* ack in different place if S = 0 */
+
+			ack = ntohl( ack);
+
+			if (ack > opt->ack_recv) opt->ack_recv = ack;
+			/* also handle sequence number wrap-around  */
+			if (WRAPPED(ack,opt->ack_recv)) opt->ack_recv = ack;
+	}
+
+	/* test if payload present */
+	if (!PPTP_GRE_IS_S(header->flags)){
+		goto drop;
+	}
+
+	headersize  = sizeof(*header);
+	payload_len = ntohs(header->payload_len);
+	seq         = ntohl(header->seq);
+
+	/* no ack present? */
+	if (!PPTP_GRE_IS_A(header->ver)) headersize -= sizeof(header->ack);
+	/* check for incomplete packet (length smaller than expected) */
+	if (skb->len - headersize < payload_len){
+#ifdef DEBUG
+		if (log_level>=1)
+			printk(KERN_INFO"PPTP: discarding truncated packet (expected %d, got %d bytes)\n",
+						payload_len, skb->len - headersize);
+#endif
+		goto drop;
+	}
+
+	payload=skb->data+headersize;
+	/* check for expected sequence number */
+	if ( seq < opt->seq_recv + 1 || WRAPPED(opt->seq_recv, seq) ){
+		if ( (payload[0] == PPP_ALLSTATIONS) && (payload[1] == PPP_UI) &&
+		     (PPP_PROTOCOL(payload) == PPP_LCP) &&
+		     ((payload[4] == PPP_LCP_ECHOREQ) || (payload[4] == PPP_LCP_ECHOREP)) ){
+#ifdef DEBUG
+			if ( log_level >= 1)
+				printk(KERN_INFO"PPTP[%i]: allowing old LCP Echo packet %d (expecting %d)\n", opt->src_addr.call_id,
+							seq, opt->seq_recv + 1);
+#endif
+			goto allow_packet;
+		}
+#ifdef DEBUG
+		if ( log_level >= 1)
+			printk(KERN_INFO"PPTP[%i]: discarding duplicate or old packet %d (expecting %d)\n",opt->src_addr.call_id,
+							seq, opt->seq_recv + 1);
+#endif
+	}else{
+		opt->seq_recv = seq;
+allow_packet:
+#ifdef DEBUG
+		if ( log_level >= 3 && opt->seq_sent<=log_packets)
+			printk(KERN_INFO"PPTP[%i]: accepting packet %d size=%i (%02x %02x %02x %02x %02x %02x)\n",opt->src_addr.call_id, seq,payload_len,
+				*(payload +0),
+				*(payload +1),
+				*(payload +2),
+				*(payload +3),
+				*(payload +4),
+				*(payload +5));
+#endif
+
+		skb_pull(skb,headersize);
+
+		if (payload[0] == PPP_ALLSTATIONS && payload[1] == PPP_UI){
+			/* chop off address/control */
+			if (skb->len < 3)
+				goto drop;
+			skb_pull(skb,2);
+		}
+
+		if ((*skb->data) & 1){
+			/* protocol is compressed */
+			skb_push(skb, 1)[0] = 0;
+		}
+
+		skb->ip_summed=CHECKSUM_NONE;
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,21)
+		skb_set_network_header(skb,skb->head-skb->data);
+#endif
+		ppp_input(&po->chan,skb);
+
+		return NET_RX_SUCCESS;
+	}
+drop:
+	kfree_skb(skb);
+	return NET_RX_DROP;
+}
+
+static int pptp_rcv(struct sk_buff *skb)
+{
+	struct pppox_sock *po;
+	struct pptp_gre_header *header;
+	struct iphdr *iph;
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,0)
+	int ret;
+	struct sock *sk;
+#endif
+
+	if (skb->pkt_type != PACKET_HOST)
+		goto drop;
+
+	/*if (!pskb_may_pull(skb, 12))
+		goto drop;*/
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
+	iph = ip_hdr(skb);
+#else
+	iph = skb->nh.iph;
+#endif
+
+	header = (struct pptp_gre_header *)skb->data;
+
+	if (    /* version should be 1 */
+					((header->ver & 0x7F) != PPTP_GRE_VER) ||
+					/* PPTP-GRE protocol for PPTP */
+					(ntohs(header->protocol) != PPTP_GRE_PROTO)||
+					/* flag C should be clear   */
+					PPTP_GRE_IS_C(header->flags) ||
+					/* flag R should be clear   */
+					PPTP_GRE_IS_R(header->flags) ||
+					/* flag K should be set     */
+					(!PPTP_GRE_IS_K(header->flags)) ||
+					/* routing and recursion ctrl = 0  */
+					((header->flags&0xF) != 0)){
+			/* if invalid, discard this packet */
+		if (log_level>=1)
+			printk(KERN_INFO"PPTP: Discarding GRE: %X %X %X %X %X %X\n",
+							header->ver&0x7F, ntohs(header->protocol),
+							PPTP_GRE_IS_C(header->flags),
+							PPTP_GRE_IS_R(header->flags),
+							PPTP_GRE_IS_K(header->flags),
+							header->flags & 0xF);
+		goto drop;
+	}
+
+
+	if ((po=lookup_chan(htons(header->call_id),iph->saddr))) {
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,31)
+		skb_dst_drop(skb);
+#else
+		dst_release(skb->dst);
+		skb->dst = NULL;
+#endif
+		nf_reset(skb);
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,0)
+		sk=sk_pppox(po);
+    		bh_lock_sock(sk);
+		/* Socket state is unknown, must put skb into backlog. */
+		if (sk->lock.users != 0) {
+		    sk_add_backlog(sk, skb);
+		    ret = NET_RX_SUCCESS;
+		} else {
+		    ret = pptp_rcv_core(sk, skb);
+		}
+		bh_unlock_sock(sk);
+		sock_put(sk);
+		return ret;
+		
+#else /* LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,0) */
+		
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,19)
+		return sk_receive_skb(sk_pppox(po), skb);
+#else
+		return sk_receive_skb(sk_pppox(po), skb, 0);
+#endif
+		
+#endif /* LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,0) */
+	}else {
+#ifdef DEBUG
+		if (log_level>=1)
+			printk(KERN_INFO"PPTP: Discarding packet from unknown call_id %i\n",htons(header->call_id));
+#endif
+	}
+
+drop:
+	kfree_skb(skb);
+	return NET_RX_DROP;
+}
+
+static int pptp_bind(struct socket *sock,struct sockaddr *uservaddr,int sockaddr_len)
+{
+	struct sock *sk = sock->sk;
+	struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr;
+	struct pppox_sock *po = pppox_sk(sk);
+	struct pptp_opt *opt=&po->proto.pptp;
+	int error=0;
+
+#ifdef DEBUG	
+	if (log_level>=1)
+		printk(KERN_INFO"PPTP: bind: addr=%X call_id=%i\n",sp->sa_addr.pptp.sin_addr.s_addr,
+						sp->sa_addr.pptp.call_id);
+#endif
+	lock_sock(sk);
+
+	opt->src_addr=sp->sa_addr.pptp;
+	if (add_chan(po))
+	{
+	    release_sock(sk);
+		error=-EBUSY;
+	}
+#ifdef DEBUG
+	if (log_level>=1)
+		printk(KERN_INFO"PPTP: using call_id %i\n",opt->src_addr.call_id);
+#endif
+
+	release_sock(sk);
+	return error;
+}
+
+static int pptp_connect(struct socket *sock, struct sockaddr *uservaddr,
+		  int sockaddr_len, int flags)
+{
+	struct sock *sk = sock->sk;
+	struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr;
+	struct pppox_sock *po = pppox_sk(sk);
+	struct pptp_opt *opt = &po->proto.pptp;
+	struct rtable *rt;     			/* Route to the other host */
+	int error=0;
+
+	if (sp->sa_protocol != PX_PROTO_PPTP)
+		return -EINVAL;
+	
+#ifdef DEBUG
+	if (log_level>=1)
+		printk(KERN_INFO"PPTP[%i]: connect: addr=%X call_id=%i\n",opt->src_addr.call_id,
+						sp->sa_addr.pptp.sin_addr.s_addr,sp->sa_addr.pptp.call_id);
+#endif
+	
+	if (lookup_chan_dst(sp->sa_addr.pptp.call_id,sp->sa_addr.pptp.sin_addr.s_addr))
+		return -EALREADY;
+
+	lock_sock(sk);
+	/* Check for already bound sockets */
+	if (SK_STATE(sk) & PPPOX_CONNECTED){
+		error = -EBUSY;
+		goto end;
+	}
+
+	/* Check for already disconnected sockets, on attempts to disconnect */
+	if (SK_STATE(sk) & PPPOX_DEAD){
+		error = -EALREADY;
+		goto end;
+	}
+
+	if (!opt->src_addr.sin_addr.s_addr || !sp->sa_addr.pptp.sin_addr.s_addr){
+		error = -EINVAL;
+		goto end;
+	}
+
+	po->chan.private=sk;
+	po->chan.ops=&pptp_chan_ops;
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	{
+		struct rt_key key = {
+			.dst=opt->dst_addr.sin_addr.s_addr,
+			.src=opt->src_addr.sin_addr.s_addr,
+			.tos=RT_TOS(0),
+		};
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,25)
+		if (ip_route_output_key(&rt, &key)) {
+#else
+		if (ip_route_output_key(&init_net, &rt, &key)) {
+#endif
+			error = -EHOSTUNREACH;
+			goto end;
+		}
+	}
+#else
+	{
+		struct flowi fl = {
+				    .nl_u = { .ip4_u =
+					      { .daddr = opt->dst_addr.sin_addr.s_addr,
+						.saddr = opt->src_addr.sin_addr.s_addr,
+						.tos = RT_CONN_FLAGS(sk) } },
+				    .proto = IPPROTO_GRE };
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,18)
+		security_sk_classify_flow(sk, &fl);
+#endif
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,25)
+		if (ip_route_output_key(&rt, &fl)){
+#else
+		if (ip_route_output_key(&init_net, &rt, &fl)){
+#endif
+			error = -EHOSTUNREACH;
+			goto end;
+		}
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36)
+		sk_setup_caps(sk, &rt->u.dst);
+#else
+		sk_setup_caps(sk, &rt->dst);
+#endif
+	}
+#endif
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	po->chan.mtu=PPP_MTU;
+#else
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36)
+	po->chan.mtu=dst_mtu(&rt->u.dst);
+#else
+	po->chan.mtu=dst_mtu(&rt->dst);
+#endif
+	if (!po->chan.mtu) po->chan.mtu=PPP_MTU;
+#endif
+	ip_rt_put(rt);
+	po->chan.mtu-=PPTP_HEADER_OVERHEAD;
+
+	po->chan.hdrlen=2+sizeof(struct pptp_gre_header);
+	error = ppp_register_channel(&po->chan);
+	if (error){
+		printk(KERN_ERR "PPTP: failed to register PPP channel (%d)\n",error);
+		goto end;
+	}
+
+	opt->dst_addr=sp->sa_addr.pptp;
+	SK_STATE(sk) = PPPOX_CONNECTED;
+
+ end:
+	release_sock(sk);
+	return error;
+}
+
+static int pptp_getname(struct socket *sock, struct sockaddr *uaddr,
+		  int *usockaddr_len, int peer)
+{
+	int len = sizeof(struct sockaddr_pppox);
+	struct sockaddr_pppox sp;
+
+	sp.sa_family	= AF_PPPOX;
+	sp.sa_protocol	= PX_PROTO_PPTP;
+	sp.sa_addr.pptp=pppox_sk(sock->sk)->proto.pptp.src_addr;
+
+	memcpy(uaddr, &sp, len);
+
+	*usockaddr_len = len;
+
+	return 0;
+}
+
+static int pptp_release(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+	struct pppox_sock *po;
+	struct pptp_opt *opt;
+	int error = 0;
+
+	if (!sk)
+	    return 0;
+
+	lock_sock(sk);
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	if (sk->dead)
+#else
+	if (sock_flag(sk, SOCK_DEAD))
+#endif
+	{
+	    release_sock(sk);
+	    return -EBADF;
+	}
+		
+	po = pppox_sk(sk);
+	opt=&po->proto.pptp;
+	del_chan(po);
+
+	pppox_unbind_sock(sk);
+	SK_STATE(sk) = PPPOX_DEAD;
+
+#ifdef DEBUG
+	if (log_level>=1)
+		printk(KERN_INFO"PPTP[%i]: release\n",opt->src_addr.call_id);
+#endif
+
+	sock_orphan(sk);
+	sock->sk = NULL;
+
+	release_sock(sk);
+	sock_put(sk);
+
+	return error;
+}
+
+
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+static struct proto pptp_sk_proto = {
+	.name	  = "PPTP",
+	.owner	  = THIS_MODULE,
+	.obj_size = sizeof(struct pppox_sock),
+};
+#endif
+
+static struct proto_ops pptp_ops = {
+    .family		= AF_PPPOX,
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+    .owner		= THIS_MODULE,
+#endif
+    .release		= pptp_release,
+    .bind		=  pptp_bind,
+    .connect		= pptp_connect,
+    .socketpair		= sock_no_socketpair,
+    .accept		= sock_no_accept,
+    .getname		= pptp_getname,
+    .poll		= sock_no_poll,
+    .listen		= sock_no_listen,
+    .shutdown		= sock_no_shutdown,
+    .setsockopt		= sock_no_setsockopt,
+    .getsockopt		= sock_no_getsockopt,
+    .sendmsg		= sock_no_sendmsg,
+    .recvmsg		= sock_no_recvmsg,
+    .mmap		= sock_no_mmap,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,16)
+    .ioctl		= pppox_ioctl,
+#endif
+};
+
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+static void pptp_sock_destruct(struct sock *sk)
+{
+	skb_queue_purge(&sk->receive_queue);
+	if (!(SK_STATE(sk) & PPPOX_DEAD)) {
+		del_chan(pppox_sk(sk));
+		pppox_unbind_sock(sk);
+	}
+	if (sk->protinfo.destruct_hook)
+		kfree(sk->protinfo.destruct_hook);
+
+	MOD_DEC_USE_COUNT;
+}
+
+static int pptp_create(struct socket *sock)
+{
+	int error = -ENOMEM;
+	struct sock *sk;
+	struct pppox_sock *po;
+	struct pptp_opt *opt;
+
+	MOD_INC_USE_COUNT;
+
+	sk = sk_alloc(PF_PPPOX, GFP_KERNEL, 1);
+	if (!sk)
+		goto out;
+
+	sock_init_data(sock, sk);
+
+	sock->state = SS_UNCONNECTED;
+	sock->ops   = &pptp_ops;
+
+	//sk->sk_backlog_rcv = pppoe_rcv_core;
+	sk->state	   = PPPOX_NONE;
+	sk->type	   = SOCK_STREAM;
+	sk->family	   = PF_PPPOX;
+	sk->protocol	   = PX_PROTO_PPTP;
+
+	sk->protinfo.pppox=kzalloc(sizeof(struct pppox_sock),GFP_KERNEL);
+	sk->destruct=pptp_sock_destruct;
+	sk->protinfo.destruct_hook=sk->protinfo.pppox;
+
+	po = pppox_sk(sk);
+	po->sk=sk;
+	opt=&po->proto.pptp;
+
+	opt->seq_sent=0; opt->seq_recv=0;
+	opt->ack_recv=0; opt->ack_sent=0;
+
+	error = 0;
+out:
+	return error;
+}
+#else
+static void pptp_sock_destruct(struct sock *sk)
+{
+    if (!(SK_STATE(sk) & PPPOX_DEAD)){
+	    del_chan(pppox_sk(sk));
+	    pppox_unbind_sock(sk);
+    }
+    skb_queue_purge(&sk->sk_receive_queue);
+}
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,24)
+static int pptp_create(struct socket *sock)
+#else
+static int pptp_create(struct net *net, struct socket *sock)
+#endif
+{
+	int error = -ENOMEM;
+	struct sock *sk;
+	struct pppox_sock *po;
+	struct pptp_opt *opt;
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,24)
+	sk = sk_alloc(PF_PPPOX, GFP_KERNEL, &pptp_sk_proto, 1);
+#else
+	sk = sk_alloc(net,PF_PPPOX, GFP_KERNEL, &pptp_sk_proto);
+#endif
+	if (!sk)
+		goto out;
+
+	sock_init_data(sock, sk);
+
+	sock->state = SS_UNCONNECTED;
+	sock->ops   = &pptp_ops;
+
+	sk->sk_backlog_rcv = pptp_rcv_core;
+	sk->sk_state	   = PPPOX_NONE;
+	sk->sk_type	   = SOCK_STREAM;
+	sk->sk_family	   = PF_PPPOX;
+	sk->sk_protocol	   = PX_PROTO_PPTP;
+	sk->sk_destruct	   = pptp_sock_destruct;
+
+	po = pppox_sk(sk);
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	po->sk=sk;
+#endif
+	opt=&po->proto.pptp;
+
+	opt->seq_sent=0; opt->seq_recv=0;
+	opt->ack_recv=0; opt->ack_sent=0;
+
+	error = 0;
+out:
+	return error;
+}
+#endif
+
+
+static int pptp_ppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
+			   unsigned long arg)
+{
+	struct sock *sk = (struct sock *) chan->private;
+	struct pppox_sock *po = pppox_sk(sk);
+	struct pptp_opt *opt=&po->proto.pptp;
+	void __user *argp = (void __user *)arg;
+	int __user *p = argp;
+	int err, val;
+
+	err = -EFAULT;
+	switch (cmd) {
+	case PPPIOCGFLAGS:
+		val = opt->ppp_flags;
+		if (put_user(val, p))
+			break;
+		err = 0;
+		break;
+	case PPPIOCSFLAGS:
+		if (get_user(val, p))
+			break;
+		opt->ppp_flags = val & ~SC_RCV_BITS;
+		err = 0;
+		break;
+	default:
+		err = -ENOTTY;
+	}
+
+	return err;
+}
+
+
+static struct pppox_proto pppox_pptp_proto = {
+    .create	= pptp_create,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,15)
+    .owner	= THIS_MODULE,
+#endif
+};
+
+#if defined(CONFIG_GRE) || defined(CONFIG_GRE_MODULE)
+static struct gre_protocol gre_pptp_protocol = {
+	.handler	= pptp_rcv,
+};
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+static struct inet_protocol net_pptp_protocol = {
+	.handler	= pptp_rcv,
+	.protocol = IPPROTO_GRE,
+	.name     = "PPTP",
+};
+#else
+static struct net_protocol net_pptp_protocol = {
+	.handler	= pptp_rcv,
+};
+#endif
+
+static int __init pptp_init_module(void)
+{
+	int err=0;
+	printk(KERN_INFO "PPTP driver version " PPTP_DRIVER_VERSION "\n");
+
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	callid_sock = __vmalloc((MAX_CALLID + 1) * sizeof(void *),
+	                        GFP_KERNEL | __GFP_ZERO, PAGE_KERNEL);
+#else
+	callid_sock = __vmalloc((MAX_CALLID + 1) * sizeof(void *),
+	                        GFP_KERNEL, PAGE_KERNEL);
+	memset(callid_sock, 0, (MAX_CALLID + 1) * sizeof(void *));
+#endif
+	if (!callid_sock) {
+		printk(KERN_ERR "PPTP: cann't allocate memory\n");
+		return -ENOMEM;
+	}
+
+#if defined(CONFIG_GRE) || defined(CONFIG_GRE_MODULE)
+	if (gre_add_protocol(&gre_pptp_protocol, GREPROTO_PPTP) < 0) {
+		printk(KERN_INFO "PPTP: can't add protocol\n");
+		goto out_free_mem;
+	}
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	inet_add_protocol(&net_pptp_protocol);
+#else
+	if (inet_add_protocol(&net_pptp_protocol, IPPROTO_GRE) < 0) {
+		printk(KERN_INFO "PPTP: can't add protocol\n");
+		goto out_free_mem;
+	}
+#endif
+
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	err = proto_register(&pptp_sk_proto, 0);
+	if (err){
+		printk(KERN_INFO "PPTP: can't register sk_proto\n");
+		goto out_inet_del_protocol;
+	}
+#endif
+
+ 	err = register_pppox_proto(PX_PROTO_PPTP, &pppox_pptp_proto);
+	if (err){
+		printk(KERN_INFO "PPTP: can't register pppox_proto\n");
+		goto out_unregister_sk_proto;
+	}
+	
+	return 0;
+out_unregister_sk_proto:
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	proto_unregister(&pptp_sk_proto);
+#endif
+
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+out_inet_del_protocol:
+#endif
+
+#if defined(CONFIG_GRE) || defined(CONFIG_GRE_MODULE)
+	gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	inet_del_protocol(&net_pptp_protocol);
+#else
+	inet_del_protocol(&net_pptp_protocol, IPPROTO_GRE);
+#endif
+out_free_mem:
+	vfree(callid_sock);
+	
+	return err;
+}
+
+static void __exit pptp_exit_module(void)
+{
+	unregister_pppox_proto(PX_PROTO_PPTP);
+#if defined(CONFIG_GRE) || defined(CONFIG_GRE_MODULE)
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+	proto_unregister(&pptp_sk_proto);
+#endif
+	gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
+#elif LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+	inet_del_protocol(&net_pptp_protocol);
+#else
+	proto_unregister(&pptp_sk_proto);
+	inet_del_protocol(&net_pptp_protocol, IPPROTO_GRE);
+#endif
+	vfree(callid_sock);
+}
+
+module_init(pptp_init_module);
+module_exit(pptp_exit_module);
+
+MODULE_DESCRIPTION("Point-to-Point Tunneling Protocol for Linux");
+MODULE_AUTHOR("Kozlov D. (xeb@mail.ru)");
+MODULE_LICENSE("GPL");
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+MODULE_PARM(log_level,"i");
+MODULE_PARM(log_packets,"i");
+#else
+module_param(log_level,int,0);
+module_param(log_packets,int,0);
+#endif
+MODULE_PARM_DESC(log_level,"Logging level (default=0)");
+