Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3435 insertions, 0 deletions

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
new file mode 100644
index 000000000..b825c6a9b
--- /dev/null
+++ b/drivers/net/ppp/ppp_generic.c
@@ -0,0 +1,3435 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Generic PPP layer for Linux.
+ *
+ * Copyright 1999-2002 Paul Mackerras.
+ *
+ * The generic PPP layer handles the PPP network interfaces, the
+ * /dev/ppp device, packet and VJ compression, and multilink.
+ * It talks to PPP `channels' via the interface defined in
+ * include/linux/ppp_channel.h.  Channels provide the basic means for
+ * sending and receiving PPP frames on some kind of communications
+ * channel.
+ *
+ * Part of the code in this driver was inspired by the old async-only
+ * PPP driver, written by Michael Callahan and Al Longyear, and
+ * subsequently hacked by Paul Mackerras.
+ *
+ * ==FILEVERSION 20041108==
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/sched/signal.h>
+#include <linux/kmod.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/idr.h>
+#include <linux/netdevice.h>
+#include <linux/poll.h>
+#include <linux/ppp_defs.h>
+#include <linux/filter.h>
+#include <linux/ppp-ioctl.h>
+#include <linux/ppp_channel.h>
+#include <linux/ppp-comp.h>
+#include <linux/skbuff.h>
+#include <linux/rtnetlink.h>
+#include <linux/if_arp.h>
+#include <linux/ip.h>
+#include <linux/tcp.h>
+#include <linux/spinlock.h>
+#include <linux/rwsem.h>
+#include <linux/stddef.h>
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <asm/unaligned.h>
+#include <net/slhc_vj.h>
+#include <linux/atomic.h>
+#include <linux/refcount.h>
+
+#include <linux/nsproxy.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+#define PPP_VERSION	"2.4.2"
+
+/*
+ * Network protocols we support.
+ */
+#define NP_IP	0		/* Internet Protocol V4 */
+#define NP_IPV6	1		/* Internet Protocol V6 */
+#define NP_IPX	2		/* IPX protocol */
+#define NP_AT	3		/* Appletalk protocol */
+#define NP_MPLS_UC 4		/* MPLS unicast */
+#define NP_MPLS_MC 5		/* MPLS multicast */
+#define NUM_NP	6		/* Number of NPs. */
+
+#define MPHDRLEN	6	/* multilink protocol header length */
+#define MPHDRLEN_SSN	4	/* ditto with short sequence numbers */
+
+#define PPP_PROTO_LEN	2
+
+/*
+ * An instance of /dev/ppp can be associated with either a ppp
+ * interface unit or a ppp channel.  In both cases, file->private_data
+ * points to one of these.
+ */
+struct ppp_file {
+	enum {
+		INTERFACE=1, CHANNEL
+	}		kind;
+	struct sk_buff_head xq;		/* pppd transmit queue */
+	struct sk_buff_head rq;		/* receive queue for pppd */
+	wait_queue_head_t rwait;	/* for poll on reading /dev/ppp */
+	refcount_t	refcnt;		/* # refs (incl /dev/ppp attached) */
+	int		hdrlen;		/* space to leave for headers */
+	int		index;		/* interface unit / channel number */
+	int		dead;		/* unit/channel has been shut down */
+};
+
+#define PF_TO_X(pf, X)		container_of(pf, X, file)
+
+#define PF_TO_PPP(pf)		PF_TO_X(pf, struct ppp)
+#define PF_TO_CHANNEL(pf)	PF_TO_X(pf, struct channel)
+
+/*
+ * Data structure to hold primary network stats for which
+ * we want to use 64 bit storage.  Other network stats
+ * are stored in dev->stats of the ppp strucute.
+ */
+struct ppp_link_stats {
+	u64 rx_packets;
+	u64 tx_packets;
+	u64 rx_bytes;
+	u64 tx_bytes;
+};
+
+/*
+ * Data structure describing one ppp unit.
+ * A ppp unit corresponds to a ppp network interface device
+ * and represents a multilink bundle.
+ * It can have 0 or more ppp channels connected to it.
+ */
+struct ppp {
+	struct ppp_file	file;		/* stuff for read/write/poll 0 */
+	struct file	*owner;		/* file that owns this unit 48 */
+	struct list_head channels;	/* list of attached channels 4c */
+	int		n_channels;	/* how many channels are attached 54 */
+	spinlock_t	rlock;		/* lock for receive side 58 */
+	spinlock_t	wlock;		/* lock for transmit side 5c */
+	int __percpu	*xmit_recursion; /* xmit recursion detect */
+	int		mru;		/* max receive unit 60 */
+	unsigned int	flags;		/* control bits 64 */
+	unsigned int	xstate;		/* transmit state bits 68 */
+	unsigned int	rstate;		/* receive state bits 6c */
+	int		debug;		/* debug flags 70 */
+	struct slcompress *vj;		/* state for VJ header compression */
+	enum NPmode	npmode[NUM_NP];	/* what to do with each net proto 78 */
+	struct sk_buff	*xmit_pending;	/* a packet ready to go out 88 */
+	struct compressor *xcomp;	/* transmit packet compressor 8c */
+	void		*xc_state;	/* its internal state 90 */
+	struct compressor *rcomp;	/* receive decompressor 94 */
+	void		*rc_state;	/* its internal state 98 */
+	unsigned long	last_xmit;	/* jiffies when last pkt sent 9c */
+	unsigned long	last_recv;	/* jiffies when last pkt rcvd a0 */
+	struct net_device *dev;		/* network interface device a4 */
+	int		closing;	/* is device closing down? a8 */
+#ifdef CONFIG_PPP_MULTILINK
+	int		nxchan;		/* next channel to send something on */
+	u32		nxseq;		/* next sequence number to send */
+	int		mrru;		/* MP: max reconst. receive unit */
+	u32		nextseq;	/* MP: seq no of next packet */
+	u32		minseq;		/* MP: min of most recent seqnos */
+	struct sk_buff_head mrq;	/* MP: receive reconstruction queue */
+#endif /* CONFIG_PPP_MULTILINK */
+#ifdef CONFIG_PPP_FILTER
+	struct bpf_prog *pass_filter;	/* filter for packets to pass */
+	struct bpf_prog *active_filter; /* filter for pkts to reset idle */
+#endif /* CONFIG_PPP_FILTER */
+	struct net	*ppp_net;	/* the net we belong to */
+	struct ppp_link_stats stats64;	/* 64 bit network stats */
+};
+
+/*
+ * Bits in flags: SC_NO_TCP_CCID, SC_CCP_OPEN, SC_CCP_UP, SC_LOOP_TRAFFIC,
+ * SC_MULTILINK, SC_MP_SHORTSEQ, SC_MP_XSHORTSEQ, SC_COMP_TCP, SC_REJ_COMP_TCP,
+ * SC_MUST_COMP
+ * Bits in rstate: SC_DECOMP_RUN, SC_DC_ERROR, SC_DC_FERROR.
+ * Bits in xstate: SC_COMP_RUN
+ */
+#define SC_FLAG_BITS	(SC_NO_TCP_CCID|SC_CCP_OPEN|SC_CCP_UP|SC_LOOP_TRAFFIC \
+			 |SC_MULTILINK|SC_MP_SHORTSEQ|SC_MP_XSHORTSEQ \
+			 |SC_COMP_TCP|SC_REJ_COMP_TCP|SC_MUST_COMP)
+
+/*
+ * Private data structure for each channel.
+ * This includes the data structure used for multilink.
+ */
+struct channel {
+	struct ppp_file	file;		/* stuff for read/write/poll */
+	struct list_head list;		/* link in all/new_channels list */
+	struct ppp_channel *chan;	/* public channel data structure */
+	struct rw_semaphore chan_sem;	/* protects `chan' during chan ioctl */
+	spinlock_t	downl;		/* protects `chan', file.xq dequeue */
+	struct ppp	*ppp;		/* ppp unit we're connected to */
+	struct net	*chan_net;	/* the net channel belongs to */
+	struct list_head clist;		/* link in list of channels per unit */
+	rwlock_t	upl;		/* protects `ppp' */
+#ifdef CONFIG_PPP_MULTILINK
+	u8		avail;		/* flag used in multilink stuff */
+	u8		had_frag;	/* >= 1 fragments have been sent */
+	u32		lastseq;	/* MP: last sequence # received */
+	int		speed;		/* speed of the corresponding ppp channel*/
+#endif /* CONFIG_PPP_MULTILINK */
+};
+
+struct ppp_config {
+	struct file *file;
+	s32 unit;
+	bool ifname_is_set;
+};
+
+/*
+ * SMP locking issues:
+ * Both the ppp.rlock and ppp.wlock locks protect the ppp.channels
+ * list and the ppp.n_channels field, you need to take both locks
+ * before you modify them.
+ * The lock ordering is: channel.upl -> ppp.wlock -> ppp.rlock ->
+ * channel.downl.
+ */
+
+static DEFINE_MUTEX(ppp_mutex);
+static atomic_t ppp_unit_count = ATOMIC_INIT(0);
+static atomic_t channel_count = ATOMIC_INIT(0);
+
+/* per-net private data for this module */
+static unsigned int ppp_net_id __read_mostly;
+struct ppp_net {
+	/* units to ppp mapping */
+	struct idr units_idr;
+
+	/*
+	 * all_ppp_mutex protects the units_idr mapping.
+	 * It also ensures that finding a ppp unit in the units_idr
+	 * map and updating its file.refcnt field is atomic.
+	 */
+	struct mutex all_ppp_mutex;
+
+	/* channels */
+	struct list_head all_channels;
+	struct list_head new_channels;
+	int last_channel_index;
+
+	/*
+	 * all_channels_lock protects all_channels and
+	 * last_channel_index, and the atomicity of find
+	 * a channel and updating its file.refcnt field.
+	 */
+	spinlock_t all_channels_lock;
+};
+
+/* Get the PPP protocol number from a skb */
+#define PPP_PROTO(skb)	get_unaligned_be16((skb)->data)
+
+/* We limit the length of ppp->file.rq to this (arbitrary) value */
+#define PPP_MAX_RQLEN	32
+
+/*
+ * Maximum number of multilink fragments queued up.
+ * This has to be large enough to cope with the maximum latency of
+ * the slowest channel relative to the others.  Strictly it should
+ * depend on the number of channels and their characteristics.
+ */
+#define PPP_MP_MAX_QLEN	128
+
+/* Multilink header bits. */
+#define B	0x80		/* this fragment begins a packet */
+#define E	0x40		/* this fragment ends a packet */
+
+/* Compare multilink sequence numbers (assumed to be 32 bits wide) */
+#define seq_before(a, b)	((s32)((a) - (b)) < 0)
+#define seq_after(a, b)		((s32)((a) - (b)) > 0)
+
+/* Prototypes. */
+static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf,
+			struct file *file, unsigned int cmd, unsigned long arg);
+static void ppp_xmit_process(struct ppp *ppp, struct sk_buff *skb);
+static void ppp_send_frame(struct ppp *ppp, struct sk_buff *skb);
+static void ppp_push(struct ppp *ppp);
+static void ppp_channel_push(struct channel *pch);
+static void ppp_receive_frame(struct ppp *ppp, struct sk_buff *skb,
+			      struct channel *pch);
+static void ppp_receive_error(struct ppp *ppp);
+static void ppp_receive_nonmp_frame(struct ppp *ppp, struct sk_buff *skb);
+static struct sk_buff *ppp_decompress_frame(struct ppp *ppp,
+					    struct sk_buff *skb);
+#ifdef CONFIG_PPP_MULTILINK
+static void ppp_receive_mp_frame(struct ppp *ppp, struct sk_buff *skb,
+				struct channel *pch);
+static void ppp_mp_insert(struct ppp *ppp, struct sk_buff *skb);
+static struct sk_buff *ppp_mp_reconstruct(struct ppp *ppp);
+static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb);
+#endif /* CONFIG_PPP_MULTILINK */
+static int ppp_set_compress(struct ppp *ppp, struct ppp_option_data *data);
+static void ppp_ccp_peek(struct ppp *ppp, struct sk_buff *skb, int inbound);
+static void ppp_ccp_closed(struct ppp *ppp);
+static struct compressor *find_compressor(int type);
+static void ppp_get_stats(struct ppp *ppp, struct ppp_stats *st);
+static int ppp_create_interface(struct net *net, struct file *file, int *unit);
+static void init_ppp_file(struct ppp_file *pf, int kind);
+static void ppp_destroy_interface(struct ppp *ppp);
+static struct ppp *ppp_find_unit(struct ppp_net *pn, int unit);
+static struct channel *ppp_find_channel(struct ppp_net *pn, int unit);
+static int ppp_connect_channel(struct channel *pch, int unit);
+static int ppp_disconnect_channel(struct channel *pch);
+static void ppp_destroy_channel(struct channel *pch);
+static int unit_get(struct idr *p, void *ptr, int min);
+static int unit_set(struct idr *p, void *ptr, int n);
+static void unit_put(struct idr *p, int n);
+static void *unit_find(struct idr *p, int n);
+static void ppp_setup(struct net_device *dev);
+
+static const struct net_device_ops ppp_netdev_ops;
+
+static struct class *ppp_class;
+
+/* per net-namespace data */
+static inline struct ppp_net *ppp_pernet(struct net *net)
+{
+	return net_generic(net, ppp_net_id);
+}
+
+/* Translates a PPP protocol number to a NP index (NP == network protocol) */
+static inline int proto_to_npindex(int proto)
+{
+	switch (proto) {
+	case PPP_IP:
+		return NP_IP;
+	case PPP_IPV6:
+		return NP_IPV6;
+	case PPP_IPX:
+		return NP_IPX;
+	case PPP_AT:
+		return NP_AT;
+	case PPP_MPLS_UC:
+		return NP_MPLS_UC;
+	case PPP_MPLS_MC:
+		return NP_MPLS_MC;
+	}
+	return -EINVAL;
+}
+
+/* Translates an NP index into a PPP protocol number */
+static const int npindex_to_proto[NUM_NP] = {
+	PPP_IP,
+	PPP_IPV6,
+	PPP_IPX,
+	PPP_AT,
+	PPP_MPLS_UC,
+	PPP_MPLS_MC,
+};
+
+/* Translates an ethertype into an NP index */
+static inline int ethertype_to_npindex(int ethertype)
+{
+	switch (ethertype) {
+	case ETH_P_IP:
+		return NP_IP;
+	case ETH_P_IPV6:
+		return NP_IPV6;
+	case ETH_P_IPX:
+		return NP_IPX;
+	case ETH_P_PPPTALK:
+	case ETH_P_ATALK:
+		return NP_AT;
+	case ETH_P_MPLS_UC:
+		return NP_MPLS_UC;
+	case ETH_P_MPLS_MC:
+		return NP_MPLS_MC;
+	}
+	return -1;
+}
+
+/* Translates an NP index into an ethertype */
+static const int npindex_to_ethertype[NUM_NP] = {
+	ETH_P_IP,
+	ETH_P_IPV6,
+	ETH_P_IPX,
+	ETH_P_PPPTALK,
+	ETH_P_MPLS_UC,
+	ETH_P_MPLS_MC,
+};
+
+/*
+ * Locking shorthand.
+ */
+#define ppp_xmit_lock(ppp)	spin_lock_bh(&(ppp)->wlock)
+#define ppp_xmit_unlock(ppp)	spin_unlock_bh(&(ppp)->wlock)
+#define ppp_recv_lock(ppp)	spin_lock_bh(&(ppp)->rlock)
+#define ppp_recv_unlock(ppp)	spin_unlock_bh(&(ppp)->rlock)
+#define ppp_lock(ppp)		do { ppp_xmit_lock(ppp); \
+				     ppp_recv_lock(ppp); } while (0)
+#define ppp_unlock(ppp)		do { ppp_recv_unlock(ppp); \
+				     ppp_xmit_unlock(ppp); } while (0)
+
+/*
+ * /dev/ppp device routines.
+ * The /dev/ppp device is used by pppd to control the ppp unit.
+ * It supports the read, write, ioctl and poll functions.
+ * Open instances of /dev/ppp can be in one of three states:
+ * unattached, attached to a ppp unit, or attached to a ppp channel.
+ */
+static int ppp_open(struct inode *inode, struct file *file)
+{
+	/*
+	 * This could (should?) be enforced by the permissions on /dev/ppp.
+	 */
+	if (!ns_capable(file->f_cred->user_ns, CAP_NET_ADMIN))
+		return -EPERM;
+	return 0;
+}
+
+static int ppp_release(struct inode *unused, struct file *file)
+{
+	struct ppp_file *pf = file->private_data;
+	struct ppp *ppp;
+
+	if (pf) {
+		file->private_data = NULL;
+		if (pf->kind == INTERFACE) {
+			ppp = PF_TO_PPP(pf);
+			rtnl_lock();
+			if (file == ppp->owner)
+				unregister_netdevice(ppp->dev);
+			rtnl_unlock();
+		}
+		if (refcount_dec_and_test(&pf->refcnt)) {
+			switch (pf->kind) {
+			case INTERFACE:
+				ppp_destroy_interface(PF_TO_PPP(pf));
+				break;
+			case CHANNEL:
+				ppp_destroy_channel(PF_TO_CHANNEL(pf));
+				break;
+			}
+		}
+	}
+	return 0;
+}
+
+static ssize_t ppp_read(struct file *file, char __user *buf,
+			size_t count, loff_t *ppos)
+{
+	struct ppp_file *pf = file->private_data;
+	DECLARE_WAITQUEUE(wait, current);
+	ssize_t ret;
+	struct sk_buff *skb = NULL;
+	struct iovec iov;
+	struct iov_iter to;
+
+	ret = count;
+
+	if (!pf)
+		return -ENXIO;
+	add_wait_queue(&pf->rwait, &wait);
+	for (;;) {
+		set_current_state(TASK_INTERRUPTIBLE);
+		skb = skb_dequeue(&pf->rq);
+		if (skb)
+			break;
+		ret = 0;
+		if (pf->dead)
+			break;
+		if (pf->kind == INTERFACE) {
+			/*
+			 * Return 0 (EOF) on an interface that has no
+			 * channels connected, unless it is looping
+			 * network traffic (demand mode).
+			 */
+			struct ppp *ppp = PF_TO_PPP(pf);
+
+			ppp_recv_lock(ppp);
+			if (ppp->n_channels == 0 &&
+			    (ppp->flags & SC_LOOP_TRAFFIC) == 0) {
+				ppp_recv_unlock(ppp);
+				break;
+			}
+			ppp_recv_unlock(ppp);
+		}
+		ret = -EAGAIN;
+		if (file->f_flags & O_NONBLOCK)
+			break;
+		ret = -ERESTARTSYS;
+		if (signal_pending(current))
+			break;
+		schedule();
+	}
+	set_current_state(TASK_RUNNING);
+	remove_wait_queue(&pf->rwait, &wait);
+
+	if (!skb)
+		goto out;
+
+	ret = -EOVERFLOW;
+	if (skb->len > count)
+		goto outf;
+	ret = -EFAULT;
+	iov.iov_base = buf;
+	iov.iov_len = count;
+	iov_iter_init(&to, READ, &iov, 1, count);
+	if (skb_copy_datagram_iter(skb, 0, &to, skb->len))
+		goto outf;
+	ret = skb->len;
+
+ outf:
+	kfree_skb(skb);
+ out:
+	return ret;
+}
+
+static ssize_t ppp_write(struct file *file, const char __user *buf,
+			 size_t count, loff_t *ppos)
+{
+	struct ppp_file *pf = file->private_data;
+	struct sk_buff *skb;
+	ssize_t ret;
+
+	if (!pf)
+		return -ENXIO;
+	/* All PPP packets should start with the 2-byte protocol */
+	if (count < PPP_PROTO_LEN)
+		return -EINVAL;
+	ret = -ENOMEM;
+	skb = alloc_skb(count + pf->hdrlen, GFP_KERNEL);
+	if (!skb)
+		goto out;
+	skb_reserve(skb, pf->hdrlen);
+	ret = -EFAULT;
+	if (copy_from_user(skb_put(skb, count), buf, count)) {
+		kfree_skb(skb);
+		goto out;
+	}
+
+	switch (pf->kind) {
+	case INTERFACE:
+		ppp_xmit_process(PF_TO_PPP(pf), skb);
+		break;
+	case CHANNEL:
+		skb_queue_tail(&pf->xq, skb);
+		ppp_channel_push(PF_TO_CHANNEL(pf));
+		break;
+	}
+
+	ret = count;
+
+ out:
+	return ret;
+}
+
+/* No kernel lock - fine */
+static __poll_t ppp_poll(struct file *file, poll_table *wait)
+{
+	struct ppp_file *pf = file->private_data;
+	__poll_t mask;
+
+	if (!pf)
+		return 0;
+	poll_wait(file, &pf->rwait, wait);
+	mask = EPOLLOUT | EPOLLWRNORM;
+	if (skb_peek(&pf->rq))
+		mask |= EPOLLIN | EPOLLRDNORM;
+	if (pf->dead)
+		mask |= EPOLLHUP;
+	else if (pf->kind == INTERFACE) {
+		/* see comment in ppp_read */
+		struct ppp *ppp = PF_TO_PPP(pf);
+
+		ppp_recv_lock(ppp);
+		if (ppp->n_channels == 0 &&
+		    (ppp->flags & SC_LOOP_TRAFFIC) == 0)
+			mask |= EPOLLIN | EPOLLRDNORM;
+		ppp_recv_unlock(ppp);
+	}
+
+	return mask;
+}
+
+#ifdef CONFIG_PPP_FILTER
+static struct bpf_prog *get_filter(struct sock_fprog *uprog)
+{
+	struct sock_fprog_kern fprog;
+	struct bpf_prog *res = NULL;
+	int err;
+
+	if (!uprog->len)
+		return NULL;
+
+	/* uprog->len is unsigned short, so no overflow here */
+	fprog.len = uprog->len;
+	fprog.filter = memdup_user(uprog->filter,
+				   uprog->len * sizeof(struct sock_filter));
+	if (IS_ERR(fprog.filter))
+		return ERR_CAST(fprog.filter);
+
+	err = bpf_prog_create(&res, &fprog);
+	kfree(fprog.filter);
+
+	return err ? ERR_PTR(err) : res;
+}
+
+static struct bpf_prog *ppp_get_filter(struct sock_fprog __user *p)
+{
+	struct sock_fprog uprog;
+
+	if (copy_from_user(&uprog, p, sizeof(struct sock_fprog)))
+		return ERR_PTR(-EFAULT);
+	return get_filter(&uprog);
+}
+
+#ifdef CONFIG_COMPAT
+struct sock_fprog32 {
+	unsigned short len;
+	compat_caddr_t filter;
+};
+
+#define PPPIOCSPASS32		_IOW('t', 71, struct sock_fprog32)
+#define PPPIOCSACTIVE32		_IOW('t', 70, struct sock_fprog32)
+
+static struct bpf_prog *compat_ppp_get_filter(struct sock_fprog32 __user *p)
+{
+	struct sock_fprog32 uprog32;
+	struct sock_fprog uprog;
+
+	if (copy_from_user(&uprog32, p, sizeof(struct sock_fprog32)))
+		return ERR_PTR(-EFAULT);
+	uprog.len = uprog32.len;
+	uprog.filter = compat_ptr(uprog32.filter);
+	return get_filter(&uprog);
+}
+#endif
+#endif
+
+static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct ppp_file *pf;
+	struct ppp *ppp;
+	int err = -EFAULT, val, val2, i;
+	struct ppp_idle32 idle32;
+	struct ppp_idle64 idle64;
+	struct npioctl npi;
+	int unit, cflags;
+	struct slcompress *vj;
+	void __user *argp = (void __user *)arg;
+	int __user *p = argp;
+
+	mutex_lock(&ppp_mutex);
+
+	pf = file->private_data;
+	if (!pf) {
+		err = ppp_unattached_ioctl(current->nsproxy->net_ns,
+					   pf, file, cmd, arg);
+		goto out;
+	}
+
+	if (cmd == PPPIOCDETACH) {
+		/*
+		 * PPPIOCDETACH is no longer supported as it was heavily broken,
+		 * and is only known to have been used by pppd older than
+		 * ppp-2.4.2 (released November 2003).
+		 */
+		pr_warn_once("%s (%d) used obsolete PPPIOCDETACH ioctl\n",
+			     current->comm, current->pid);
+		err = -EINVAL;
+		goto out;
+	}
+
+	if (pf->kind == CHANNEL) {
+		struct channel *pch;
+		struct ppp_channel *chan;
+
+		pch = PF_TO_CHANNEL(pf);
+
+		switch (cmd) {
+		case PPPIOCCONNECT:
+			if (get_user(unit, p))
+				break;
+			err = ppp_connect_channel(pch, unit);
+			break;
+
+		case PPPIOCDISCONN:
+			err = ppp_disconnect_channel(pch);
+			break;
+
+		default:
+			down_read(&pch->chan_sem);
+			chan = pch->chan;
+			err = -ENOTTY;
+			if (chan && chan->ops->ioctl)
+				err = chan->ops->ioctl(chan, cmd, arg);
+			up_read(&pch->chan_sem);
+		}
+		goto out;
+	}
+
+	if (pf->kind != INTERFACE) {
+		/* can't happen */
+		pr_err("PPP: not interface or channel??\n");
+		err = -EINVAL;
+		goto out;
+	}
+
+	ppp = PF_TO_PPP(pf);
+	switch (cmd) {
+	case PPPIOCSMRU:
+		if (get_user(val, p))
+			break;
+		ppp->mru = val;
+		err = 0;
+		break;
+
+	case PPPIOCSFLAGS:
+		if (get_user(val, p))
+			break;
+		ppp_lock(ppp);
+		cflags = ppp->flags & ~val;
+#ifdef CONFIG_PPP_MULTILINK
+		if (!(ppp->flags & SC_MULTILINK) && (val & SC_MULTILINK))
+			ppp->nextseq = 0;
+#endif
+		ppp->flags = val & SC_FLAG_BITS;
+		ppp_unlock(ppp);
+		if (cflags & SC_CCP_OPEN)
+			ppp_ccp_closed(ppp);
+		err = 0;
+		break;
+
+	case PPPIOCGFLAGS:
+		val = ppp->flags | ppp->xstate | ppp->rstate;
+		if (put_user(val, p))
+			break;
+		err = 0;
+		break;
+
+	case PPPIOCSCOMPRESS:
+	{
+		struct ppp_option_data data;
+		if (copy_from_user(&data, argp, sizeof(data)))
+			err = -EFAULT;
+		else
+			err = ppp_set_compress(ppp, &data);
+		break;
+	}
+	case PPPIOCGUNIT:
+		if (put_user(ppp->file.index, p))
+			break;
+		err = 0;
+		break;
+
+	case PPPIOCSDEBUG:
+		if (get_user(val, p))
+			break;
+		ppp->debug = val;
+		err = 0;
+		break;
+
+	case PPPIOCGDEBUG:
+		if (put_user(ppp->debug, p))
+			break;
+		err = 0;
+		break;
+
+	case PPPIOCGIDLE32:
+                idle32.xmit_idle = (jiffies - ppp->last_xmit) / HZ;
+                idle32.recv_idle = (jiffies - ppp->last_recv) / HZ;
+                if (copy_to_user(argp, &idle32, sizeof(idle32)))
+			break;
+		err = 0;
+		break;
+
+	case PPPIOCGIDLE64:
+		idle64.xmit_idle = (jiffies - ppp->last_xmit) / HZ;
+		idle64.recv_idle = (jiffies - ppp->last_recv) / HZ;
+		if (copy_to_user(argp, &idle64, sizeof(idle64)))
+			break;
+		err = 0;
+		break;
+
+	case PPPIOCSMAXCID:
+		if (get_user(val, p))
+			break;
+		val2 = 15;
+		if ((val >> 16) != 0) {
+			val2 = val >> 16;
+			val &= 0xffff;
+		}
+		vj = slhc_init(val2+1, val+1);
+		if (IS_ERR(vj)) {
+			err = PTR_ERR(vj);
+			break;
+		}
+		ppp_lock(ppp);
+		if (ppp->vj)
+			slhc_free(ppp->vj);
+		ppp->vj = vj;
+		ppp_unlock(ppp);
+		err = 0;
+		break;
+
+	case PPPIOCGNPMODE:
+	case PPPIOCSNPMODE:
+		if (copy_from_user(&npi, argp, sizeof(npi)))
+			break;
+		err = proto_to_npindex(npi.protocol);
+		if (err < 0)
+			break;
+		i = err;
+		if (cmd == PPPIOCGNPMODE) {
+			err = -EFAULT;
+			npi.mode = ppp->npmode[i];
+			if (copy_to_user(argp, &npi, sizeof(npi)))
+				break;
+		} else {
+			ppp->npmode[i] = npi.mode;
+			/* we may be able to transmit more packets now (??) */
+			netif_wake_queue(ppp->dev);
+		}
+		err = 0;
+		break;
+
+#ifdef CONFIG_PPP_FILTER
+	case PPPIOCSPASS:
+	case PPPIOCSACTIVE:
+	{
+		struct bpf_prog *filter = ppp_get_filter(argp);
+		struct bpf_prog **which;
+
+		if (IS_ERR(filter)) {
+			err = PTR_ERR(filter);
+			break;
+		}
+		if (cmd == PPPIOCSPASS)
+			which = &ppp->pass_filter;
+		else
+			which = &ppp->active_filter;
+		ppp_lock(ppp);
+		if (*which)
+			bpf_prog_destroy(*which);
+		*which = filter;
+		ppp_unlock(ppp);
+		err = 0;
+		break;
+	}
+#endif /* CONFIG_PPP_FILTER */
+
+#ifdef CONFIG_PPP_MULTILINK
+	case PPPIOCSMRRU:
+		if (get_user(val, p))
+			break;
+		ppp_recv_lock(ppp);
+		ppp->mrru = val;
+		ppp_recv_unlock(ppp);
+		err = 0;
+		break;
+#endif /* CONFIG_PPP_MULTILINK */
+
+	default:
+		err = -ENOTTY;
+	}
+
+out:
+	mutex_unlock(&ppp_mutex);
+
+	return err;
+}
+
+#ifdef CONFIG_COMPAT
+struct ppp_option_data32 {
+	compat_uptr_t		ptr;
+	u32			length;
+	compat_int_t		transmit;
+};
+#define PPPIOCSCOMPRESS32	_IOW('t', 77, struct ppp_option_data32)
+
+static long ppp_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct ppp_file *pf;
+	int err = -ENOIOCTLCMD;
+	void __user *argp = (void __user *)arg;
+
+	mutex_lock(&ppp_mutex);
+
+	pf = file->private_data;
+	if (pf && pf->kind == INTERFACE) {
+		struct ppp *ppp = PF_TO_PPP(pf);
+		switch (cmd) {
+#ifdef CONFIG_PPP_FILTER
+		case PPPIOCSPASS32:
+		case PPPIOCSACTIVE32:
+		{
+			struct bpf_prog *filter = compat_ppp_get_filter(argp);
+			struct bpf_prog **which;
+
+			if (IS_ERR(filter)) {
+				err = PTR_ERR(filter);
+				break;
+			}
+			if (cmd == PPPIOCSPASS32)
+				which = &ppp->pass_filter;
+			else
+				which = &ppp->active_filter;
+			ppp_lock(ppp);
+			if (*which)
+				bpf_prog_destroy(*which);
+			*which = filter;
+			ppp_unlock(ppp);
+			err = 0;
+			break;
+		}
+#endif /* CONFIG_PPP_FILTER */
+		case PPPIOCSCOMPRESS32:
+		{
+			struct ppp_option_data32 data32;
+			if (copy_from_user(&data32, argp, sizeof(data32))) {
+				err = -EFAULT;
+			} else {
+				struct ppp_option_data data = {
+					.ptr = compat_ptr(data32.ptr),
+					.length = data32.length,
+					.transmit = data32.transmit
+				};
+				err = ppp_set_compress(ppp, &data);
+			}
+			break;
+		}
+		}
+	}
+	mutex_unlock(&ppp_mutex);
+
+	/* all other commands have compatible arguments */
+	if (err == -ENOIOCTLCMD)
+		err = ppp_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
+
+	return err;
+}
+#endif
+
+static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf,
+			struct file *file, unsigned int cmd, unsigned long arg)
+{
+	int unit, err = -EFAULT;
+	struct ppp *ppp;
+	struct channel *chan;
+	struct ppp_net *pn;
+	int __user *p = (int __user *)arg;
+
+	switch (cmd) {
+	case PPPIOCNEWUNIT:
+		/* Create a new ppp unit */
+		if (get_user(unit, p))
+			break;
+		err = ppp_create_interface(net, file, &unit);
+		if (err < 0)
+			break;
+
+		err = -EFAULT;
+		if (put_user(unit, p))
+			break;
+		err = 0;
+		break;
+
+	case PPPIOCATTACH:
+		/* Attach to an existing ppp unit */
+		if (get_user(unit, p))
+			break;
+		err = -ENXIO;
+		pn = ppp_pernet(net);
+		mutex_lock(&pn->all_ppp_mutex);
+		ppp = ppp_find_unit(pn, unit);
+		if (ppp) {
+			refcount_inc(&ppp->file.refcnt);
+			file->private_data = &ppp->file;
+			err = 0;
+		}
+		mutex_unlock(&pn->all_ppp_mutex);
+		break;
+
+	case PPPIOCATTCHAN:
+		if (get_user(unit, p))
+			break;
+		err = -ENXIO;
+		pn = ppp_pernet(net);
+		spin_lock_bh(&pn->all_channels_lock);
+		chan = ppp_find_channel(pn, unit);
+		if (chan) {
+			refcount_inc(&chan->file.refcnt);
+			file->private_data = &chan->file;
+			err = 0;
+		}
+		spin_unlock_bh(&pn->all_channels_lock);
+		break;
+
+	default:
+		err = -ENOTTY;
+	}
+
+	return err;
+}
+
+static const struct file_operations ppp_device_fops = {
+	.owner		= THIS_MODULE,
+	.read		= ppp_read,
+	.write		= ppp_write,
+	.poll		= ppp_poll,
+	.unlocked_ioctl	= ppp_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= ppp_compat_ioctl,
+#endif
+	.open		= ppp_open,
+	.release	= ppp_release,
+	.llseek		= noop_llseek,
+};
+
+static __net_init int ppp_init_net(struct net *net)
+{
+	struct ppp_net *pn = net_generic(net, ppp_net_id);
+
+	idr_init(&pn->units_idr);
+	mutex_init(&pn->all_ppp_mutex);
+
+	INIT_LIST_HEAD(&pn->all_channels);
+	INIT_LIST_HEAD(&pn->new_channels);
+
+	spin_lock_init(&pn->all_channels_lock);
+
+	return 0;
+}
+
+static __net_exit void ppp_exit_net(struct net *net)
+{
+	struct ppp_net *pn = net_generic(net, ppp_net_id);
+	struct net_device *dev;
+	struct net_device *aux;
+	struct ppp *ppp;
+	LIST_HEAD(list);
+	int id;
+
+	rtnl_lock();
+	for_each_netdev_safe(net, dev, aux) {
+		if (dev->netdev_ops == &ppp_netdev_ops)
+			unregister_netdevice_queue(dev, &list);
+	}
+
+	idr_for_each_entry(&pn->units_idr, ppp, id)
+		/* Skip devices already unregistered by previous loop */
+		if (!net_eq(dev_net(ppp->dev), net))
+			unregister_netdevice_queue(ppp->dev, &list);
+
+	unregister_netdevice_many(&list);
+	rtnl_unlock();
+
+	mutex_destroy(&pn->all_ppp_mutex);
+	idr_destroy(&pn->units_idr);
+	WARN_ON_ONCE(!list_empty(&pn->all_channels));
+	WARN_ON_ONCE(!list_empty(&pn->new_channels));
+}
+
+static struct pernet_operations ppp_net_ops = {
+	.init = ppp_init_net,
+	.exit = ppp_exit_net,
+	.id   = &ppp_net_id,
+	.size = sizeof(struct ppp_net),
+};
+
+static int ppp_unit_register(struct ppp *ppp, int unit, bool ifname_is_set)
+{
+	struct ppp_net *pn = ppp_pernet(ppp->ppp_net);
+	int ret;
+
+	mutex_lock(&pn->all_ppp_mutex);
+
+	if (unit < 0) {
+		ret = unit_get(&pn->units_idr, ppp, 0);
+		if (ret < 0)
+			goto err;
+		if (!ifname_is_set) {
+			while (1) {
+				snprintf(ppp->dev->name, IFNAMSIZ, "ppp%i", ret);
+				if (!__dev_get_by_name(ppp->ppp_net, ppp->dev->name))
+					break;
+				unit_put(&pn->units_idr, ret);
+				ret = unit_get(&pn->units_idr, ppp, ret + 1);
+				if (ret < 0)
+					goto err;
+			}
+		}
+	} else {
+		/* Caller asked for a specific unit number. Fail with -EEXIST
+		 * if unavailable. For backward compatibility, return -EEXIST
+		 * too if idr allocation fails; this makes pppd retry without
+		 * requesting a specific unit number.
+		 */
+		if (unit_find(&pn->units_idr, unit)) {
+			ret = -EEXIST;
+			goto err;
+		}
+		ret = unit_set(&pn->units_idr, ppp, unit);
+		if (ret < 0) {
+			/* Rewrite error for backward compatibility */
+			ret = -EEXIST;
+			goto err;
+		}
+	}
+	ppp->file.index = ret;
+
+	if (!ifname_is_set)
+		snprintf(ppp->dev->name, IFNAMSIZ, "ppp%i", ppp->file.index);
+
+	mutex_unlock(&pn->all_ppp_mutex);
+
+	ret = register_netdevice(ppp->dev);
+	if (ret < 0)
+		goto err_unit;
+
+	atomic_inc(&ppp_unit_count);
+
+	return 0;
+
+err_unit:
+	mutex_lock(&pn->all_ppp_mutex);
+	unit_put(&pn->units_idr, ppp->file.index);
+err:
+	mutex_unlock(&pn->all_ppp_mutex);
+
+	return ret;
+}
+
+static int ppp_dev_configure(struct net *src_net, struct net_device *dev,
+			     const struct ppp_config *conf)
+{
+	struct ppp *ppp = netdev_priv(dev);
+	int indx;
+	int err;
+	int cpu;
+
+	ppp->dev = dev;
+	ppp->ppp_net = src_net;
+	ppp->mru = PPP_MRU;
+	ppp->owner = conf->file;
+
+	init_ppp_file(&ppp->file, INTERFACE);
+	ppp->file.hdrlen = PPP_HDRLEN - 2; /* don't count proto bytes */
+
+	for (indx = 0; indx < NUM_NP; ++indx)
+		ppp->npmode[indx] = NPMODE_PASS;
+	INIT_LIST_HEAD(&ppp->channels);
+	spin_lock_init(&ppp->rlock);
+	spin_lock_init(&ppp->wlock);
+
+	ppp->xmit_recursion = alloc_percpu(int);
+	if (!ppp->xmit_recursion) {
+		err = -ENOMEM;
+		goto err1;
+	}
+	for_each_possible_cpu(cpu)
+		(*per_cpu_ptr(ppp->xmit_recursion, cpu)) = 0;
+
+#ifdef CONFIG_PPP_MULTILINK
+	ppp->minseq = -1;
+	skb_queue_head_init(&ppp->mrq);
+#endif /* CONFIG_PPP_MULTILINK */
+#ifdef CONFIG_PPP_FILTER
+	ppp->pass_filter = NULL;
+	ppp->active_filter = NULL;
+#endif /* CONFIG_PPP_FILTER */
+
+	err = ppp_unit_register(ppp, conf->unit, conf->ifname_is_set);
+	if (err < 0)
+		goto err2;
+
+	conf->file->private_data = &ppp->file;
+
+	return 0;
+err2:
+	free_percpu(ppp->xmit_recursion);
+err1:
+	return err;
+}
+
+static const struct nla_policy ppp_nl_policy[IFLA_PPP_MAX + 1] = {
+	[IFLA_PPP_DEV_FD]	= { .type = NLA_S32 },
+};
+
+static int ppp_nl_validate(struct nlattr *tb[], struct nlattr *data[],
+			   struct netlink_ext_ack *extack)
+{
+	if (!data)
+		return -EINVAL;
+
+	if (!data[IFLA_PPP_DEV_FD])
+		return -EINVAL;
+	if (nla_get_s32(data[IFLA_PPP_DEV_FD]) < 0)
+		return -EBADF;
+
+	return 0;
+}
+
+static int ppp_nl_newlink(struct net *src_net, struct net_device *dev,
+			  struct nlattr *tb[], struct nlattr *data[],
+			  struct netlink_ext_ack *extack)
+{
+	struct ppp_config conf = {
+		.unit = -1,
+		.ifname_is_set = true,
+	};
+	struct file *file;
+	int err;
+
+	file = fget(nla_get_s32(data[IFLA_PPP_DEV_FD]));
+	if (!file)
+		return -EBADF;
+
+	/* rtnl_lock is already held here, but ppp_create_interface() locks
+	 * ppp_mutex before holding rtnl_lock. Using mutex_trylock() avoids
+	 * possible deadlock due to lock order inversion, at the cost of
+	 * pushing the problem back to userspace.
+	 */
+	if (!mutex_trylock(&ppp_mutex)) {
+		err = -EBUSY;
+		goto out;
+	}
+
+	if (file->f_op != &ppp_device_fops || file->private_data) {
+		err = -EBADF;
+		goto out_unlock;
+	}
+
+	conf.file = file;
+
+	/* Don't use device name generated by the rtnetlink layer when ifname
+	 * isn't specified. Let ppp_dev_configure() set the device name using
+	 * the PPP unit identifer as suffix (i.e. ppp<unit_id>). This allows
+	 * userspace to infer the device name using to the PPPIOCGUNIT ioctl.
+	 */
+	if (!tb[IFLA_IFNAME] || !nla_len(tb[IFLA_IFNAME]) || !*(char *)nla_data(tb[IFLA_IFNAME]))
+		conf.ifname_is_set = false;
+
+	err = ppp_dev_configure(src_net, dev, &conf);
+
+out_unlock:
+	mutex_unlock(&ppp_mutex);
+out:
+	fput(file);
+
+	return err;
+}
+
+static void ppp_nl_dellink(struct net_device *dev, struct list_head *head)
+{
+	unregister_netdevice_queue(dev, head);
+}
+
+static size_t ppp_nl_get_size(const struct net_device *dev)
+{
+	return 0;
+}
+
+static int ppp_nl_fill_info(struct sk_buff *skb, const struct net_device *dev)
+{
+	return 0;
+}
+
+static struct net *ppp_nl_get_link_net(const struct net_device *dev)
+{
+	struct ppp *ppp = netdev_priv(dev);
+
+	return ppp->ppp_net;
+}
+
+static struct rtnl_link_ops ppp_link_ops __read_mostly = {
+	.kind		= "ppp",
+	.maxtype	= IFLA_PPP_MAX,
+	.policy		= ppp_nl_policy,
+	.priv_size	= sizeof(struct ppp),
+	.setup		= ppp_setup,
+	.validate	= ppp_nl_validate,
+	.newlink	= ppp_nl_newlink,
+	.dellink	= ppp_nl_dellink,
+	.get_size	= ppp_nl_get_size,
+	.fill_info	= ppp_nl_fill_info,
+	.get_link_net	= ppp_nl_get_link_net,
+};
+
+#define PPP_MAJOR	108
+
+/* Called at boot time if ppp is compiled into the kernel,
+   or at module load time (from init_module) if compiled as a module. */
+static int __init ppp_init(void)
+{
+	int err;
+
+	pr_info("PPP generic driver version " PPP_VERSION "\n");
+
+	err = register_pernet_device(&ppp_net_ops);
+	if (err) {
+		pr_err("failed to register PPP pernet device (%d)\n", err);
+		goto out;
+	}
+
+	err = register_chrdev(PPP_MAJOR, "ppp", &ppp_device_fops);
+	if (err) {
+		pr_err("failed to register PPP device (%d)\n", err);
+		goto out_net;
+	}
+
+	ppp_class = class_create(THIS_MODULE, "ppp");
+	if (IS_ERR(ppp_class)) {
+		err = PTR_ERR(ppp_class);
+		goto out_chrdev;
+	}
+
+	err = rtnl_link_register(&ppp_link_ops);
+	if (err) {
+		pr_err("failed to register rtnetlink PPP handler\n");
+		goto out_class;
+	}
+
+	/* not a big deal if we fail here :-) */
+	device_create(ppp_class, NULL, MKDEV(PPP_MAJOR, 0), NULL, "ppp");
+
+	return 0;
+
+out_class:
+	class_destroy(ppp_class);
+out_chrdev:
+	unregister_chrdev(PPP_MAJOR, "ppp");
+out_net:
+	unregister_pernet_device(&ppp_net_ops);
+out:
+	return err;
+}
+
+/*
+ * Network interface unit routines.
+ */
+static netdev_tx_t
+ppp_start_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct ppp *ppp = netdev_priv(dev);
+	int npi, proto;
+	unsigned char *pp;
+
+	npi = ethertype_to_npindex(ntohs(skb->protocol));
+	if (npi < 0)
+		goto outf;
+
+	/* Drop, accept or reject the packet */
+	switch (ppp->npmode[npi]) {
+	case NPMODE_PASS:
+		break;
+	case NPMODE_QUEUE:
+		/* it would be nice to have a way to tell the network
+		   system to queue this one up for later. */
+		goto outf;
+	case NPMODE_DROP:
+	case NPMODE_ERROR:
+		goto outf;
+	}
+
+	/* Put the 2-byte PPP protocol number on the front,
+	   making sure there is room for the address and control fields. */
+	if (skb_cow_head(skb, PPP_HDRLEN))
+		goto outf;
+
+	pp = skb_push(skb, 2);
+	proto = npindex_to_proto[npi];
+	put_unaligned_be16(proto, pp);
+
+	skb_scrub_packet(skb, !net_eq(ppp->ppp_net, dev_net(dev)));
+	ppp_xmit_process(ppp, skb);
+
+	return NETDEV_TX_OK;
+
+ outf:
+	kfree_skb(skb);
+	++dev->stats.tx_dropped;
+	return NETDEV_TX_OK;
+}
+
+static int
+ppp_net_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
+{
+	struct ppp *ppp = netdev_priv(dev);
+	int err = -EFAULT;
+	void __user *addr = (void __user *) ifr->ifr_ifru.ifru_data;
+	struct ppp_stats stats;
+	struct ppp_comp_stats cstats;
+	char *vers;
+
+	switch (cmd) {
+	case SIOCGPPPSTATS:
+		ppp_get_stats(ppp, &stats);
+		if (copy_to_user(addr, &stats, sizeof(stats)))
+			break;
+		err = 0;
+		break;
+
+	case SIOCGPPPCSTATS:
+		memset(&cstats, 0, sizeof(cstats));
+		if (ppp->xc_state)
+			ppp->xcomp->comp_stat(ppp->xc_state, &cstats.c);
+		if (ppp->rc_state)
+			ppp->rcomp->decomp_stat(ppp->rc_state, &cstats.d);
+		if (copy_to_user(addr, &cstats, sizeof(cstats)))
+			break;
+		err = 0;
+		break;
+
+	case SIOCGPPPVER:
+		vers = PPP_VERSION;
+		if (copy_to_user(addr, vers, strlen(vers) + 1))
+			break;
+		err = 0;
+		break;
+
+	default:
+		err = -EINVAL;
+	}
+
+	return err;
+}
+
+static void
+ppp_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats64)
+{
+	struct ppp *ppp = netdev_priv(dev);
+
+	ppp_recv_lock(ppp);
+	stats64->rx_packets = ppp->stats64.rx_packets;
+	stats64->rx_bytes   = ppp->stats64.rx_bytes;
+	ppp_recv_unlock(ppp);
+
+	ppp_xmit_lock(ppp);
+	stats64->tx_packets = ppp->stats64.tx_packets;
+	stats64->tx_bytes   = ppp->stats64.tx_bytes;
+	ppp_xmit_unlock(ppp);
+
+	stats64->rx_errors        = dev->stats.rx_errors;
+	stats64->tx_errors        = dev->stats.tx_errors;
+	stats64->rx_dropped       = dev->stats.rx_dropped;
+	stats64->tx_dropped       = dev->stats.tx_dropped;
+	stats64->rx_length_errors = dev->stats.rx_length_errors;
+}
+
+static int ppp_dev_init(struct net_device *dev)
+{
+	struct ppp *ppp;
+
+	netdev_lockdep_set_classes(dev);
+
+	ppp = netdev_priv(dev);
+	/* Let the netdevice take a reference on the ppp file. This ensures
+	 * that ppp_destroy_interface() won't run before the device gets
+	 * unregistered.
+	 */
+	refcount_inc(&ppp->file.refcnt);
+
+	return 0;
+}
+
+static void ppp_dev_uninit(struct net_device *dev)
+{
+	struct ppp *ppp = netdev_priv(dev);
+	struct ppp_net *pn = ppp_pernet(ppp->ppp_net);
+
+	ppp_lock(ppp);
+	ppp->closing = 1;
+	ppp_unlock(ppp);
+
+	mutex_lock(&pn->all_ppp_mutex);
+	unit_put(&pn->units_idr, ppp->file.index);
+	mutex_unlock(&pn->all_ppp_mutex);
+
+	ppp->owner = NULL;
+
+	ppp->file.dead = 1;
+	wake_up_interruptible(&ppp->file.rwait);
+}
+
+static void ppp_dev_priv_destructor(struct net_device *dev)
+{
+	struct ppp *ppp;
+
+	ppp = netdev_priv(dev);
+	if (refcount_dec_and_test(&ppp->file.refcnt))
+		ppp_destroy_interface(ppp);
+}
+
+static const struct net_device_ops ppp_netdev_ops = {
+	.ndo_init	 = ppp_dev_init,
+	.ndo_uninit      = ppp_dev_uninit,
+	.ndo_start_xmit  = ppp_start_xmit,
+	.ndo_do_ioctl    = ppp_net_ioctl,
+	.ndo_get_stats64 = ppp_get_stats64,
+};
+
+static struct device_type ppp_type = {
+	.name = "ppp",
+};
+
+static void ppp_setup(struct net_device *dev)
+{
+	dev->netdev_ops = &ppp_netdev_ops;
+	SET_NETDEV_DEVTYPE(dev, &ppp_type);
+
+	dev->features |= NETIF_F_LLTX;
+
+	dev->hard_header_len = PPP_HDRLEN;
+	dev->mtu = PPP_MRU;
+	dev->addr_len = 0;
+	dev->tx_queue_len = 3;
+	dev->type = ARPHRD_PPP;
+	dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
+	dev->priv_destructor = ppp_dev_priv_destructor;
+	netif_keep_dst(dev);
+}
+
+/*
+ * Transmit-side routines.
+ */
+
+/* Called to do any work queued up on the transmit side that can now be done */
+static void __ppp_xmit_process(struct ppp *ppp, struct sk_buff *skb)
+{
+	ppp_xmit_lock(ppp);
+	if (!ppp->closing) {
+		ppp_push(ppp);
+
+		if (skb)
+			skb_queue_tail(&ppp->file.xq, skb);
+		while (!ppp->xmit_pending &&
+		       (skb = skb_dequeue(&ppp->file.xq)))
+			ppp_send_frame(ppp, skb);
+		/* If there's no work left to do, tell the core net
+		   code that we can accept some more. */
+		if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq))
+			netif_wake_queue(ppp->dev);
+		else
+			netif_stop_queue(ppp->dev);
+	} else {
+		kfree_skb(skb);
+	}
+	ppp_xmit_unlock(ppp);
+}
+
+static void ppp_xmit_process(struct ppp *ppp, struct sk_buff *skb)
+{
+	local_bh_disable();
+
+	if (unlikely(*this_cpu_ptr(ppp->xmit_recursion)))
+		goto err;
+
+	(*this_cpu_ptr(ppp->xmit_recursion))++;
+	__ppp_xmit_process(ppp, skb);
+	(*this_cpu_ptr(ppp->xmit_recursion))--;
+
+	local_bh_enable();
+
+	return;
+
+err:
+	local_bh_enable();
+
+	kfree_skb(skb);
+
+	if (net_ratelimit())
+		netdev_err(ppp->dev, "recursion detected\n");
+}
+
+static inline struct sk_buff *
+pad_compress_skb(struct ppp *ppp, struct sk_buff *skb)
+{
+	struct sk_buff *new_skb;
+	int len;
+	int new_skb_size = ppp->dev->mtu +
+		ppp->xcomp->comp_extra + ppp->dev->hard_header_len;
+	int compressor_skb_size = ppp->dev->mtu +
+		ppp->xcomp->comp_extra + PPP_HDRLEN;
+	new_skb = alloc_skb(new_skb_size, GFP_ATOMIC);
+	if (!new_skb) {
+		if (net_ratelimit())
+			netdev_err(ppp->dev, "PPP: no memory (comp pkt)\n");
+		return NULL;
+	}
+	if (ppp->dev->hard_header_len > PPP_HDRLEN)
+		skb_reserve(new_skb,
+			    ppp->dev->hard_header_len - PPP_HDRLEN);
+
+	/* compressor still expects A/C bytes in hdr */
+	len = ppp->xcomp->compress(ppp->xc_state, skb->data - 2,
+				   new_skb->data, skb->len + 2,
+				   compressor_skb_size);
+	if (len > 0 && (ppp->flags & SC_CCP_UP)) {
+		consume_skb(skb);
+		skb = new_skb;
+		skb_put(skb, len);
+		skb_pull(skb, 2);	/* pull off A/C bytes */
+	} else if (len == 0) {
+		/* didn't compress, or CCP not up yet */
+		consume_skb(new_skb);
+		new_skb = skb;
+	} else {
+		/*
+		 * (len < 0)
+		 * MPPE requires that we do not send unencrypted
+		 * frames.  The compressor will return -1 if we
+		 * should drop the frame.  We cannot simply test
+		 * the compress_proto because MPPE and MPPC share
+		 * the same number.
+		 */
+		if (net_ratelimit())
+			netdev_err(ppp->dev, "ppp: compressor dropped pkt\n");
+		kfree_skb(skb);
+		consume_skb(new_skb);
+		new_skb = NULL;
+	}
+	return new_skb;
+}
+
+/*
+ * Compress and send a frame.
+ * The caller should have locked the xmit path,
+ * and xmit_pending should be 0.
+ */
+static void
+ppp_send_frame(struct ppp *ppp, struct sk_buff *skb)
+{
+	int proto = PPP_PROTO(skb);
+	struct sk_buff *new_skb;
+	int len;
+	unsigned char *cp;
+
+	skb->dev = ppp->dev;
+
+	if (proto < 0x8000) {
+#ifdef CONFIG_PPP_FILTER
+		/* check if we should pass this packet */
+		/* the filter instructions are constructed assuming
+		   a four-byte PPP header on each packet */
+		*(u8 *)skb_push(skb, 2) = 1;
+		if (ppp->pass_filter &&
+		    BPF_PROG_RUN(ppp->pass_filter, skb) == 0) {
+			if (ppp->debug & 1)
+				netdev_printk(KERN_DEBUG, ppp->dev,
+					      "PPP: outbound frame "
+					      "not passed\n");
+			kfree_skb(skb);
+			return;
+		}
+		/* if this packet passes the active filter, record the time */
+		if (!(ppp->active_filter &&
+		      BPF_PROG_RUN(ppp->active_filter, skb) == 0))
+			ppp->last_xmit = jiffies;
+		skb_pull(skb, 2);
+#else
+		/* for data packets, record the time */
+		ppp->last_xmit = jiffies;
+#endif /* CONFIG_PPP_FILTER */
+	}
+
+	++ppp->stats64.tx_packets;
+	ppp->stats64.tx_bytes += skb->len - PPP_PROTO_LEN;
+
+	switch (proto) {
+	case PPP_IP:
+		if (!ppp->vj || (ppp->flags & SC_COMP_TCP) == 0)
+			break;
+		/* try to do VJ TCP header compression */
+		new_skb = alloc_skb(skb->len + ppp->dev->hard_header_len - 2,
+				    GFP_ATOMIC);
+		if (!new_skb) {
+			netdev_err(ppp->dev, "PPP: no memory (VJ comp pkt)\n");
+			goto drop;
+		}
+		skb_reserve(new_skb, ppp->dev->hard_header_len - 2);
+		cp = skb->data + 2;
+		len = slhc_compress(ppp->vj, cp, skb->len - 2,
+				    new_skb->data + 2, &cp,
+				    !(ppp->flags & SC_NO_TCP_CCID));
+		if (cp == skb->data + 2) {
+			/* didn't compress */
+			consume_skb(new_skb);
+		} else {
+			if (cp[0] & SL_TYPE_COMPRESSED_TCP) {
+				proto = PPP_VJC_COMP;
+				cp[0] &= ~SL_TYPE_COMPRESSED_TCP;
+			} else {
+				proto = PPP_VJC_UNCOMP;
+				cp[0] = skb->data[2];
+			}
+			consume_skb(skb);
+			skb = new_skb;
+			cp = skb_put(skb, len + 2);
+			cp[0] = 0;
+			cp[1] = proto;
+		}
+		break;
+
+	case PPP_CCP:
+		/* peek at outbound CCP frames */
+		ppp_ccp_peek(ppp, skb, 0);
+		break;
+	}
+
+	/* try to do packet compression */
+	if ((ppp->xstate & SC_COMP_RUN) && ppp->xc_state &&
+	    proto != PPP_LCP && proto != PPP_CCP) {
+		if (!(ppp->flags & SC_CCP_UP) && (ppp->flags & SC_MUST_COMP)) {
+			if (net_ratelimit())
+				netdev_err(ppp->dev,
+					   "ppp: compression required but "
+					   "down - pkt dropped.\n");
+			goto drop;
+		}
+		skb = pad_compress_skb(ppp, skb);
+		if (!skb)
+			goto drop;
+	}
+
+	/*
+	 * If we are waiting for traffic (demand dialling),
+	 * queue it up for pppd to receive.
+	 */
+	if (ppp->flags & SC_LOOP_TRAFFIC) {
+		if (ppp->file.rq.qlen > PPP_MAX_RQLEN)
+			goto drop;
+		skb_queue_tail(&ppp->file.rq, skb);
+		wake_up_interruptible(&ppp->file.rwait);
+		return;
+	}
+
+	ppp->xmit_pending = skb;
+	ppp_push(ppp);
+	return;
+
+ drop:
+	kfree_skb(skb);
+	++ppp->dev->stats.tx_errors;
+}
+
+/*
+ * Try to send the frame in xmit_pending.
+ * The caller should have the xmit path locked.
+ */
+static void
+ppp_push(struct ppp *ppp)
+{
+	struct list_head *list;
+	struct channel *pch;
+	struct sk_buff *skb = ppp->xmit_pending;
+
+	if (!skb)
+		return;
+
+	list = &ppp->channels;
+	if (list_empty(list)) {
+		/* nowhere to send the packet, just drop it */
+		ppp->xmit_pending = NULL;
+		kfree_skb(skb);
+		return;
+	}
+
+	if ((ppp->flags & SC_MULTILINK) == 0) {
+		/* not doing multilink: send it down the first channel */
+		list = list->next;
+		pch = list_entry(list, struct channel, clist);
+
+		spin_lock(&pch->downl);
+		if (pch->chan) {
+			if (pch->chan->ops->start_xmit(pch->chan, skb))
+				ppp->xmit_pending = NULL;
+		} else {
+			/* channel got unregistered */
+			kfree_skb(skb);
+			ppp->xmit_pending = NULL;
+		}
+		spin_unlock(&pch->downl);
+		return;
+	}
+
+#ifdef CONFIG_PPP_MULTILINK
+	/* Multilink: fragment the packet over as many links
+	   as can take the packet at the moment. */
+	if (!ppp_mp_explode(ppp, skb))
+		return;
+#endif /* CONFIG_PPP_MULTILINK */
+
+	ppp->xmit_pending = NULL;
+	kfree_skb(skb);
+}
+
+#ifdef CONFIG_PPP_MULTILINK
+static bool mp_protocol_compress __read_mostly = true;
+module_param(mp_protocol_compress, bool, 0644);
+MODULE_PARM_DESC(mp_protocol_compress,
+		 "compress protocol id in multilink fragments");
+
+/*
+ * Divide a packet to be transmitted into fragments and
+ * send them out the individual links.
+ */
+static int ppp_mp_explode(struct ppp *ppp, struct sk_buff *skb)
+{
+	int len, totlen;
+	int i, bits, hdrlen, mtu;
+	int flen;
+	int navail, nfree, nzero;
+	int nbigger;
+	int totspeed;
+	int totfree;
+	unsigned char *p, *q;
+	struct list_head *list;
+	struct channel *pch;
+	struct sk_buff *frag;
+	struct ppp_channel *chan;
+
+	totspeed = 0; /*total bitrate of the bundle*/
+	nfree = 0; /* # channels which have no packet already queued */
+	navail = 0; /* total # of usable channels (not deregistered) */
+	nzero = 0; /* number of channels with zero speed associated*/
+	totfree = 0; /*total # of channels available and
+				  *having no queued packets before
+				  *starting the fragmentation*/
+
+	hdrlen = (ppp->flags & SC_MP_XSHORTSEQ)? MPHDRLEN_SSN: MPHDRLEN;
+	i = 0;
+	list_for_each_entry(pch, &ppp->channels, clist) {
+		if (pch->chan) {
+			pch->avail = 1;
+			navail++;
+			pch->speed = pch->chan->speed;
+		} else {
+			pch->avail = 0;
+		}
+		if (pch->avail) {
+			if (skb_queue_empty(&pch->file.xq) ||
+				!pch->had_frag) {
+					if (pch->speed == 0)
+						nzero++;
+					else
+						totspeed += pch->speed;
+
+					pch->avail = 2;
+					++nfree;
+					++totfree;
+				}
+			if (!pch->had_frag && i < ppp->nxchan)
+				ppp->nxchan = i;
+		}
+		++i;
+	}
+	/*
+	 * Don't start sending this packet unless at least half of
+	 * the channels are free.  This gives much better TCP
+	 * performance if we have a lot of channels.
+	 */
+	if (nfree == 0 || nfree < navail / 2)
+		return 0; /* can't take now, leave it in xmit_pending */
+
+	/* Do protocol field compression */
+	p = skb->data;
+	len = skb->len;
+	if (*p == 0 && mp_protocol_compress) {
+		++p;
+		--len;
+	}
+
+	totlen = len;
+	nbigger = len % nfree;
+
+	/* skip to the channel after the one we last used
+	   and start at that one */
+	list = &ppp->channels;
+	for (i = 0; i < ppp->nxchan; ++i) {
+		list = list->next;
+		if (list == &ppp->channels) {
+			i = 0;
+			break;
+		}
+	}
+
+	/* create a fragment for each channel */
+	bits = B;
+	while (len > 0) {
+		list = list->next;
+		if (list == &ppp->channels) {
+			i = 0;
+			continue;
+		}
+		pch = list_entry(list, struct channel, clist);
+		++i;
+		if (!pch->avail)
+			continue;
+
+		/*
+		 * Skip this channel if it has a fragment pending already and
+		 * we haven't given a fragment to all of the free channels.
+		 */
+		if (pch->avail == 1) {
+			if (nfree > 0)
+				continue;
+		} else {
+			pch->avail = 1;
+		}
+
+		/* check the channel's mtu and whether it is still attached. */
+		spin_lock(&pch->downl);
+		if (pch->chan == NULL) {
+			/* can't use this channel, it's being deregistered */
+			if (pch->speed == 0)
+				nzero--;
+			else
+				totspeed -= pch->speed;
+
+			spin_unlock(&pch->downl);
+			pch->avail = 0;
+			totlen = len;
+			totfree--;
+			nfree--;
+			if (--navail == 0)
+				break;
+			continue;
+		}
+
+		/*
+		*if the channel speed is not set divide
+		*the packet evenly among the free channels;
+		*otherwise divide it according to the speed
+		*of the channel we are going to transmit on
+		*/
+		flen = len;
+		if (nfree > 0) {
+			if (pch->speed == 0) {
+				flen = len/nfree;
+				if (nbigger > 0) {
+					flen++;
+					nbigger--;
+				}
+			} else {
+				flen = (((totfree - nzero)*(totlen + hdrlen*totfree)) /
+					((totspeed*totfree)/pch->speed)) - hdrlen;
+				if (nbigger > 0) {
+					flen += ((totfree - nzero)*pch->speed)/totspeed;
+					nbigger -= ((totfree - nzero)*pch->speed)/
+							totspeed;
+				}
+			}
+			nfree--;
+		}
+
+		/*
+		 *check if we are on the last channel or
+		 *we exceded the length of the data to
+		 *fragment
+		 */
+		if ((nfree <= 0) || (flen > len))
+			flen = len;
+		/*
+		 *it is not worth to tx on slow channels:
+		 *in that case from the resulting flen according to the
+		 *above formula will be equal or less than zero.
+		 *Skip the channel in this case
+		 */
+		if (flen <= 0) {
+			pch->avail = 2;
+			spin_unlock(&pch->downl);
+			continue;
+		}
+
+		/*
+		 * hdrlen includes the 2-byte PPP protocol field, but the
+		 * MTU counts only the payload excluding the protocol field.
+		 * (RFC1661 Section 2)
+		 */
+		mtu = pch->chan->mtu - (hdrlen - 2);
+		if (mtu < 4)
+			mtu = 4;
+		if (flen > mtu)
+			flen = mtu;
+		if (flen == len)
+			bits |= E;
+		frag = alloc_skb(flen + hdrlen + (flen == 0), GFP_ATOMIC);
+		if (!frag)
+			goto noskb;
+		q = skb_put(frag, flen + hdrlen);
+
+		/* make the MP header */
+		put_unaligned_be16(PPP_MP, q);
+		if (ppp->flags & SC_MP_XSHORTSEQ) {
+			q[2] = bits + ((ppp->nxseq >> 8) & 0xf);
+			q[3] = ppp->nxseq;
+		} else {
+			q[2] = bits;
+			q[3] = ppp->nxseq >> 16;
+			q[4] = ppp->nxseq >> 8;
+			q[5] = ppp->nxseq;
+		}
+
+		memcpy(q + hdrlen, p, flen);
+
+		/* try to send it down the channel */
+		chan = pch->chan;
+		if (!skb_queue_empty(&pch->file.xq) ||
+			!chan->ops->start_xmit(chan, frag))
+			skb_queue_tail(&pch->file.xq, frag);
+		pch->had_frag = 1;
+		p += flen;
+		len -= flen;
+		++ppp->nxseq;
+		bits = 0;
+		spin_unlock(&pch->downl);
+	}
+	ppp->nxchan = i;
+
+	return 1;
+
+ noskb:
+	spin_unlock(&pch->downl);
+	if (ppp->debug & 1)
+		netdev_err(ppp->dev, "PPP: no memory (fragment)\n");
+	++ppp->dev->stats.tx_errors;
+	++ppp->nxseq;
+	return 1;	/* abandon the frame */
+}
+#endif /* CONFIG_PPP_MULTILINK */
+
+/* Try to send data out on a channel */
+static void __ppp_channel_push(struct channel *pch)
+{
+	struct sk_buff *skb;
+	struct ppp *ppp;
+
+	spin_lock(&pch->downl);
+	if (pch->chan) {
+		while (!skb_queue_empty(&pch->file.xq)) {
+			skb = skb_dequeue(&pch->file.xq);
+			if (!pch->chan->ops->start_xmit(pch->chan, skb)) {
+				/* put the packet back and try again later */
+				skb_queue_head(&pch->file.xq, skb);
+				break;
+			}
+		}
+	} else {
+		/* channel got deregistered */
+		skb_queue_purge(&pch->file.xq);
+	}
+	spin_unlock(&pch->downl);
+	/* see if there is anything from the attached unit to be sent */
+	if (skb_queue_empty(&pch->file.xq)) {
+		ppp = pch->ppp;
+		if (ppp)
+			__ppp_xmit_process(ppp, NULL);
+	}
+}
+
+static void ppp_channel_push(struct channel *pch)
+{
+	read_lock_bh(&pch->upl);
+	if (pch->ppp) {
+		(*this_cpu_ptr(pch->ppp->xmit_recursion))++;
+		__ppp_channel_push(pch);
+		(*this_cpu_ptr(pch->ppp->xmit_recursion))--;
+	} else {
+		__ppp_channel_push(pch);
+	}
+	read_unlock_bh(&pch->upl);
+}
+
+/*
+ * Receive-side routines.
+ */
+
+struct ppp_mp_skb_parm {
+	u32		sequence;
+	u8		BEbits;
+};
+#define PPP_MP_CB(skb)	((struct ppp_mp_skb_parm *)((skb)->cb))
+
+static inline void
+ppp_do_recv(struct ppp *ppp, struct sk_buff *skb, struct channel *pch)
+{
+	ppp_recv_lock(ppp);
+	if (!ppp->closing)
+		ppp_receive_frame(ppp, skb, pch);
+	else
+		kfree_skb(skb);
+	ppp_recv_unlock(ppp);
+}
+
+/**
+ * __ppp_decompress_proto - Decompress protocol field, slim version.
+ * @skb: Socket buffer where protocol field should be decompressed. It must have
+ *	 at least 1 byte of head room and 1 byte of linear data. First byte of
+ *	 data must be a protocol field byte.
+ *
+ * Decompress protocol field in PPP header if it's compressed, e.g. when
+ * Protocol-Field-Compression (PFC) was negotiated. No checks w.r.t. skb data
+ * length are done in this function.
+ */
+static void __ppp_decompress_proto(struct sk_buff *skb)
+{
+	if (skb->data[0] & 0x01)
+		*(u8 *)skb_push(skb, 1) = 0x00;
+}
+
+/**
+ * ppp_decompress_proto - Check skb data room and decompress protocol field.
+ * @skb: Socket buffer where protocol field should be decompressed. First byte
+ *	 of data must be a protocol field byte.
+ *
+ * Decompress protocol field in PPP header if it's compressed, e.g. when
+ * Protocol-Field-Compression (PFC) was negotiated. This function also makes
+ * sure that skb data room is sufficient for Protocol field, before and after
+ * decompression.
+ *
+ * Return: true - decompressed successfully, false - not enough room in skb.
+ */
+static bool ppp_decompress_proto(struct sk_buff *skb)
+{
+	/* At least one byte should be present (if protocol is compressed) */
+	if (!pskb_may_pull(skb, 1))
+		return false;
+
+	__ppp_decompress_proto(skb);
+
+	/* Protocol field should occupy 2 bytes when not compressed */
+	return pskb_may_pull(skb, 2);
+}
+
+void
+ppp_input(struct ppp_channel *chan, struct sk_buff *skb)
+{
+	struct channel *pch = chan->ppp;
+	int proto;
+
+	if (!pch) {
+		kfree_skb(skb);
+		return;
+	}
+
+	read_lock_bh(&pch->upl);
+	if (!ppp_decompress_proto(skb)) {
+		kfree_skb(skb);
+		if (pch->ppp) {
+			++pch->ppp->dev->stats.rx_length_errors;
+			ppp_receive_error(pch->ppp);
+		}
+		goto done;
+	}
+
+	proto = PPP_PROTO(skb);
+	if (!pch->ppp || proto >= 0xc000 || proto == PPP_CCPFRAG) {
+		/* put it on the channel queue */
+		skb_queue_tail(&pch->file.rq, skb);
+		/* drop old frames if queue too long */
+		while (pch->file.rq.qlen > PPP_MAX_RQLEN &&
+		       (skb = skb_dequeue(&pch->file.rq)))
+			kfree_skb(skb);
+		wake_up_interruptible(&pch->file.rwait);
+	} else {
+		ppp_do_recv(pch->ppp, skb, pch);
+	}
+
+done:
+	read_unlock_bh(&pch->upl);
+}
+
+/* Put a 0-length skb in the receive queue as an error indication */
+void
+ppp_input_error(struct ppp_channel *chan, int code)
+{
+	struct channel *pch = chan->ppp;
+	struct sk_buff *skb;
+
+	if (!pch)
+		return;
+
+	read_lock_bh(&pch->upl);
+	if (pch->ppp) {
+		skb = alloc_skb(0, GFP_ATOMIC);
+		if (skb) {
+			skb->len = 0;		/* probably unnecessary */
+			skb->cb[0] = code;
+			ppp_do_recv(pch->ppp, skb, pch);
+		}
+	}
+	read_unlock_bh(&pch->upl);
+}
+
+/*
+ * We come in here to process a received frame.
+ * The receive side of the ppp unit is locked.
+ */
+static void
+ppp_receive_frame(struct ppp *ppp, struct sk_buff *skb, struct channel *pch)
+{
+	/* note: a 0-length skb is used as an error indication */
+	if (skb->len > 0) {
+		skb_checksum_complete_unset(skb);
+#ifdef CONFIG_PPP_MULTILINK
+		/* XXX do channel-level decompression here */
+		if (PPP_PROTO(skb) == PPP_MP)
+			ppp_receive_mp_frame(ppp, skb, pch);
+		else
+#endif /* CONFIG_PPP_MULTILINK */
+			ppp_receive_nonmp_frame(ppp, skb);
+	} else {
+		kfree_skb(skb);
+		ppp_receive_error(ppp);
+	}
+}
+
+static void
+ppp_receive_error(struct ppp *ppp)
+{
+	++ppp->dev->stats.rx_errors;
+	if (ppp->vj)
+		slhc_toss(ppp->vj);
+}
+
+static void
+ppp_receive_nonmp_frame(struct ppp *ppp, struct sk_buff *skb)
+{
+	struct sk_buff *ns;
+	int proto, len, npi;
+
+	/*
+	 * Decompress the frame, if compressed.
+	 * Note that some decompressors need to see uncompressed frames
+	 * that come in as well as compressed frames.
+	 */
+	if (ppp->rc_state && (ppp->rstate & SC_DECOMP_RUN) &&
+	    (ppp->rstate & (SC_DC_FERROR | SC_DC_ERROR)) == 0)
+		skb = ppp_decompress_frame(ppp, skb);
+
+	if (ppp->flags & SC_MUST_COMP && ppp->rstate & SC_DC_FERROR)
+		goto err;
+
+	/* At this point the "Protocol" field MUST be decompressed, either in
+	 * ppp_input(), ppp_decompress_frame() or in ppp_receive_mp_frame().
+	 */
+	proto = PPP_PROTO(skb);
+	switch (proto) {
+	case PPP_VJC_COMP:
+		/* decompress VJ compressed packets */
+		if (!ppp->vj || (ppp->flags & SC_REJ_COMP_TCP))
+			goto err;
+
+		if (skb_tailroom(skb) < 124 || skb_cloned(skb)) {
+			/* copy to a new sk_buff with more tailroom */
+			ns = dev_alloc_skb(skb->len + 128);
+			if (!ns) {
+				netdev_err(ppp->dev, "PPP: no memory "
+					   "(VJ decomp)\n");
+				goto err;
+			}
+			skb_reserve(ns, 2);
+			skb_copy_bits(skb, 0, skb_put(ns, skb->len), skb->len);
+			consume_skb(skb);
+			skb = ns;
+		}
+		else
+			skb->ip_summed = CHECKSUM_NONE;
+
+		len = slhc_uncompress(ppp->vj, skb->data + 2, skb->len - 2);
+		if (len <= 0) {
+			netdev_printk(KERN_DEBUG, ppp->dev,
+				      "PPP: VJ decompression error\n");
+			goto err;
+		}
+		len += 2;
+		if (len > skb->len)
+			skb_put(skb, len - skb->len);
+		else if (len < skb->len)
+			skb_trim(skb, len);
+		proto = PPP_IP;
+		break;
+
+	case PPP_VJC_UNCOMP:
+		if (!ppp->vj || (ppp->flags & SC_REJ_COMP_TCP))
+			goto err;
+
+		/* Until we fix the decompressor need to make sure
+		 * data portion is linear.
+		 */
+		if (!pskb_may_pull(skb, skb->len))
+			goto err;
+
+		if (slhc_remember(ppp->vj, skb->data + 2, skb->len - 2) <= 0) {
+			netdev_err(ppp->dev, "PPP: VJ uncompressed error\n");
+			goto err;
+		}
+		proto = PPP_IP;
+		break;
+
+	case PPP_CCP:
+		ppp_ccp_peek(ppp, skb, 1);
+		break;
+	}
+
+	++ppp->stats64.rx_packets;
+	ppp->stats64.rx_bytes += skb->len - 2;
+
+	npi = proto_to_npindex(proto);
+	if (npi < 0) {
+		/* control or unknown frame - pass it to pppd */
+		skb_queue_tail(&ppp->file.rq, skb);
+		/* limit queue length by dropping old frames */
+		while (ppp->file.rq.qlen > PPP_MAX_RQLEN &&
+		       (skb = skb_dequeue(&ppp->file.rq)))
+			kfree_skb(skb);
+		/* wake up any process polling or blocking on read */
+		wake_up_interruptible(&ppp->file.rwait);
+
+	} else {
+		/* network protocol frame - give it to the kernel */
+
+#ifdef CONFIG_PPP_FILTER
+		/* check if the packet passes the pass and active filters */
+		/* the filter instructions are constructed assuming
+		   a four-byte PPP header on each packet */
+		if (ppp->pass_filter || ppp->active_filter) {
+			if (skb_unclone(skb, GFP_ATOMIC))
+				goto err;
+
+			*(u8 *)skb_push(skb, 2) = 0;
+			if (ppp->pass_filter &&
+			    BPF_PROG_RUN(ppp->pass_filter, skb) == 0) {
+				if (ppp->debug & 1)
+					netdev_printk(KERN_DEBUG, ppp->dev,
+						      "PPP: inbound frame "
+						      "not passed\n");
+				kfree_skb(skb);
+				return;
+			}
+			if (!(ppp->active_filter &&
+			      BPF_PROG_RUN(ppp->active_filter, skb) == 0))
+				ppp->last_recv = jiffies;
+			__skb_pull(skb, 2);
+		} else
+#endif /* CONFIG_PPP_FILTER */
+			ppp->last_recv = jiffies;
+
+		if ((ppp->dev->flags & IFF_UP) == 0 ||
+		    ppp->npmode[npi] != NPMODE_PASS) {
+			kfree_skb(skb);
+		} else {
+			/* chop off protocol */
+			skb_pull_rcsum(skb, 2);
+			skb->dev = ppp->dev;
+			skb->protocol = htons(npindex_to_ethertype[npi]);
+			skb_reset_mac_header(skb);
+			skb_scrub_packet(skb, !net_eq(ppp->ppp_net,
+						      dev_net(ppp->dev)));
+			netif_rx(skb);
+		}
+	}
+	return;
+
+ err:
+	kfree_skb(skb);
+	ppp_receive_error(ppp);
+}
+
+static struct sk_buff *
+ppp_decompress_frame(struct ppp *ppp, struct sk_buff *skb)
+{
+	int proto = PPP_PROTO(skb);
+	struct sk_buff *ns;
+	int len;
+
+	/* Until we fix all the decompressor's need to make sure
+	 * data portion is linear.
+	 */
+	if (!pskb_may_pull(skb, skb->len))
+		goto err;
+
+	if (proto == PPP_COMP) {
+		int obuff_size;
+
+		switch(ppp->rcomp->compress_proto) {
+		case CI_MPPE:
+			obuff_size = ppp->mru + PPP_HDRLEN + 1;
+			break;
+		default:
+			obuff_size = ppp->mru + PPP_HDRLEN;
+			break;
+		}
+
+		ns = dev_alloc_skb(obuff_size);
+		if (!ns) {
+			netdev_err(ppp->dev, "ppp_decompress_frame: "
+				   "no memory\n");
+			goto err;
+		}
+		/* the decompressor still expects the A/C bytes in the hdr */
+		len = ppp->rcomp->decompress(ppp->rc_state, skb->data - 2,
+				skb->len + 2, ns->data, obuff_size);
+		if (len < 0) {
+			/* Pass the compressed frame to pppd as an
+			   error indication. */
+			if (len == DECOMP_FATALERROR)
+				ppp->rstate |= SC_DC_FERROR;
+			kfree_skb(ns);
+			goto err;
+		}
+
+		consume_skb(skb);
+		skb = ns;
+		skb_put(skb, len);
+		skb_pull(skb, 2);	/* pull off the A/C bytes */
+
+		/* Don't call __ppp_decompress_proto() here, but instead rely on
+		 * corresponding algo (mppe/bsd/deflate) to decompress it.
+		 */
+	} else {
+		/* Uncompressed frame - pass to decompressor so it
+		   can update its dictionary if necessary. */
+		if (ppp->rcomp->incomp)
+			ppp->rcomp->incomp(ppp->rc_state, skb->data - 2,
+					   skb->len + 2);
+	}
+
+	return skb;
+
+ err:
+	ppp->rstate |= SC_DC_ERROR;
+	ppp_receive_error(ppp);
+	return skb;
+}
+
+#ifdef CONFIG_PPP_MULTILINK
+/*
+ * Receive a multilink frame.
+ * We put it on the reconstruction queue and then pull off
+ * as many completed frames as we can.
+ */
+static void
+ppp_receive_mp_frame(struct ppp *ppp, struct sk_buff *skb, struct channel *pch)
+{
+	u32 mask, seq;
+	struct channel *ch;
+	int mphdrlen = (ppp->flags & SC_MP_SHORTSEQ)? MPHDRLEN_SSN: MPHDRLEN;
+
+	if (!pskb_may_pull(skb, mphdrlen + 1) || ppp->mrru == 0)
+		goto err;		/* no good, throw it away */
+
+	/* Decode sequence number and begin/end bits */
+	if (ppp->flags & SC_MP_SHORTSEQ) {
+		seq = ((skb->data[2] & 0x0f) << 8) | skb->data[3];
+		mask = 0xfff;
+	} else {
+		seq = (skb->data[3] << 16) | (skb->data[4] << 8)| skb->data[5];
+		mask = 0xffffff;
+	}
+	PPP_MP_CB(skb)->BEbits = skb->data[2];
+	skb_pull(skb, mphdrlen);	/* pull off PPP and MP headers */
+
+	/*
+	 * Do protocol ID decompression on the first fragment of each packet.
+	 * We have to do that here, because ppp_receive_nonmp_frame() expects
+	 * decompressed protocol field.
+	 */
+	if (PPP_MP_CB(skb)->BEbits & B)
+		__ppp_decompress_proto(skb);
+
+	/*
+	 * Expand sequence number to 32 bits, making it as close
+	 * as possible to ppp->minseq.
+	 */
+	seq |= ppp->minseq & ~mask;
+	if ((int)(ppp->minseq - seq) > (int)(mask >> 1))
+		seq += mask + 1;
+	else if ((int)(seq - ppp->minseq) > (int)(mask >> 1))
+		seq -= mask + 1;	/* should never happen */
+	PPP_MP_CB(skb)->sequence = seq;
+	pch->lastseq = seq;
+
+	/*
+	 * If this packet comes before the next one we were expecting,
+	 * drop it.
+	 */
+	if (seq_before(seq, ppp->nextseq)) {
+		kfree_skb(skb);
+		++ppp->dev->stats.rx_dropped;
+		ppp_receive_error(ppp);
+		return;
+	}
+
+	/*
+	 * Reevaluate minseq, the minimum over all channels of the
+	 * last sequence number received on each channel.  Because of
+	 * the increasing sequence number rule, we know that any fragment
+	 * before `minseq' which hasn't arrived is never going to arrive.
+	 * The list of channels can't change because we have the receive
+	 * side of the ppp unit locked.
+	 */
+	list_for_each_entry(ch, &ppp->channels, clist) {
+		if (seq_before(ch->lastseq, seq))
+			seq = ch->lastseq;
+	}
+	if (seq_before(ppp->minseq, seq))
+		ppp->minseq = seq;
+
+	/* Put the fragment on the reconstruction queue */
+	ppp_mp_insert(ppp, skb);
+
+	/* If the queue is getting long, don't wait any longer for packets
+	   before the start of the queue. */
+	if (skb_queue_len(&ppp->mrq) >= PPP_MP_MAX_QLEN) {
+		struct sk_buff *mskb = skb_peek(&ppp->mrq);
+		if (seq_before(ppp->minseq, PPP_MP_CB(mskb)->sequence))
+			ppp->minseq = PPP_MP_CB(mskb)->sequence;
+	}
+
+	/* Pull completed packets off the queue and receive them. */
+	while ((skb = ppp_mp_reconstruct(ppp))) {
+		if (pskb_may_pull(skb, 2))
+			ppp_receive_nonmp_frame(ppp, skb);
+		else {
+			++ppp->dev->stats.rx_length_errors;
+			kfree_skb(skb);
+			ppp_receive_error(ppp);
+		}
+	}
+
+	return;
+
+ err:
+	kfree_skb(skb);
+	ppp_receive_error(ppp);
+}
+
+/*
+ * Insert a fragment on the MP reconstruction queue.
+ * The queue is ordered by increasing sequence number.
+ */
+static void
+ppp_mp_insert(struct ppp *ppp, struct sk_buff *skb)
+{
+	struct sk_buff *p;
+	struct sk_buff_head *list = &ppp->mrq;
+	u32 seq = PPP_MP_CB(skb)->sequence;
+
+	/* N.B. we don't need to lock the list lock because we have the
+	   ppp unit receive-side lock. */
+	skb_queue_walk(list, p) {
+		if (seq_before(seq, PPP_MP_CB(p)->sequence))
+			break;
+	}
+	__skb_queue_before(list, p, skb);
+}
+
+/*
+ * Reconstruct a packet from the MP fragment queue.
+ * We go through increasing sequence numbers until we find a
+ * complete packet, or we get to the sequence number for a fragment
+ * which hasn't arrived but might still do so.
+ */
+static struct sk_buff *
+ppp_mp_reconstruct(struct ppp *ppp)
+{
+	u32 seq = ppp->nextseq;
+	u32 minseq = ppp->minseq;
+	struct sk_buff_head *list = &ppp->mrq;
+	struct sk_buff *p, *tmp;
+	struct sk_buff *head, *tail;
+	struct sk_buff *skb = NULL;
+	int lost = 0, len = 0;
+
+	if (ppp->mrru == 0)	/* do nothing until mrru is set */
+		return NULL;
+	head = __skb_peek(list);
+	tail = NULL;
+	skb_queue_walk_safe(list, p, tmp) {
+	again:
+		if (seq_before(PPP_MP_CB(p)->sequence, seq)) {
+			/* this can't happen, anyway ignore the skb */
+			netdev_err(ppp->dev, "ppp_mp_reconstruct bad "
+				   "seq %u < %u\n",
+				   PPP_MP_CB(p)->sequence, seq);
+			__skb_unlink(p, list);
+			kfree_skb(p);
+			continue;
+		}
+		if (PPP_MP_CB(p)->sequence != seq) {
+			u32 oldseq;
+			/* Fragment `seq' is missing.  If it is after
+			   minseq, it might arrive later, so stop here. */
+			if (seq_after(seq, minseq))
+				break;
+			/* Fragment `seq' is lost, keep going. */
+			lost = 1;
+			oldseq = seq;
+			seq = seq_before(minseq, PPP_MP_CB(p)->sequence)?
+				minseq + 1: PPP_MP_CB(p)->sequence;
+
+			if (ppp->debug & 1)
+				netdev_printk(KERN_DEBUG, ppp->dev,
+					      "lost frag %u..%u\n",
+					      oldseq, seq-1);
+
+			goto again;
+		}
+
+		/*
+		 * At this point we know that all the fragments from
+		 * ppp->nextseq to seq are either present or lost.
+		 * Also, there are no complete packets in the queue
+		 * that have no missing fragments and end before this
+		 * fragment.
+		 */
+
+		/* B bit set indicates this fragment starts a packet */
+		if (PPP_MP_CB(p)->BEbits & B) {
+			head = p;
+			lost = 0;
+			len = 0;
+		}
+
+		len += p->len;
+
+		/* Got a complete packet yet? */
+		if (lost == 0 && (PPP_MP_CB(p)->BEbits & E) &&
+		    (PPP_MP_CB(head)->BEbits & B)) {
+			if (len > ppp->mrru + 2) {
+				++ppp->dev->stats.rx_length_errors;
+				netdev_printk(KERN_DEBUG, ppp->dev,
+					      "PPP: reconstructed packet"
+					      " is too long (%d)\n", len);
+			} else {
+				tail = p;
+				break;
+			}
+			ppp->nextseq = seq + 1;
+		}
+
+		/*
+		 * If this is the ending fragment of a packet,
+		 * and we haven't found a complete valid packet yet,
+		 * we can discard up to and including this fragment.
+		 */
+		if (PPP_MP_CB(p)->BEbits & E) {
+			struct sk_buff *tmp2;
+
+			skb_queue_reverse_walk_from_safe(list, p, tmp2) {
+				if (ppp->debug & 1)
+					netdev_printk(KERN_DEBUG, ppp->dev,
+						      "discarding frag %u\n",
+						      PPP_MP_CB(p)->sequence);
+				__skb_unlink(p, list);
+				kfree_skb(p);
+			}
+			head = skb_peek(list);
+			if (!head)
+				break;
+		}
+		++seq;
+	}
+
+	/* If we have a complete packet, copy it all into one skb. */
+	if (tail != NULL) {
+		/* If we have discarded any fragments,
+		   signal a receive error. */
+		if (PPP_MP_CB(head)->sequence != ppp->nextseq) {
+			skb_queue_walk_safe(list, p, tmp) {
+				if (p == head)
+					break;
+				if (ppp->debug & 1)
+					netdev_printk(KERN_DEBUG, ppp->dev,
+						      "discarding frag %u\n",
+						      PPP_MP_CB(p)->sequence);
+				__skb_unlink(p, list);
+				kfree_skb(p);
+			}
+
+			if (ppp->debug & 1)
+				netdev_printk(KERN_DEBUG, ppp->dev,
+					      "  missed pkts %u..%u\n",
+					      ppp->nextseq,
+					      PPP_MP_CB(head)->sequence-1);
+			++ppp->dev->stats.rx_dropped;
+			ppp_receive_error(ppp);
+		}
+
+		skb = head;
+		if (head != tail) {
+			struct sk_buff **fragpp = &skb_shinfo(skb)->frag_list;
+			p = skb_queue_next(list, head);
+			__skb_unlink(skb, list);
+			skb_queue_walk_from_safe(list, p, tmp) {
+				__skb_unlink(p, list);
+				*fragpp = p;
+				p->next = NULL;
+				fragpp = &p->next;
+
+				skb->len += p->len;
+				skb->data_len += p->len;
+				skb->truesize += p->truesize;
+
+				if (p == tail)
+					break;
+			}
+		} else {
+			__skb_unlink(skb, list);
+		}
+
+		ppp->nextseq = PPP_MP_CB(tail)->sequence + 1;
+	}
+
+	return skb;
+}
+#endif /* CONFIG_PPP_MULTILINK */
+
+/*
+ * Channel interface.
+ */
+
+/* Create a new, unattached ppp channel. */
+int ppp_register_channel(struct ppp_channel *chan)
+{
+	return ppp_register_net_channel(current->nsproxy->net_ns, chan);
+}
+
+/* Create a new, unattached ppp channel for specified net. */
+int ppp_register_net_channel(struct net *net, struct ppp_channel *chan)
+{
+	struct channel *pch;
+	struct ppp_net *pn;
+
+	pch = kzalloc(sizeof(struct channel), GFP_KERNEL);
+	if (!pch)
+		return -ENOMEM;
+
+	pn = ppp_pernet(net);
+
+	pch->ppp = NULL;
+	pch->chan = chan;
+	pch->chan_net = get_net(net);
+	chan->ppp = pch;
+	init_ppp_file(&pch->file, CHANNEL);
+	pch->file.hdrlen = chan->hdrlen;
+#ifdef CONFIG_PPP_MULTILINK
+	pch->lastseq = -1;
+#endif /* CONFIG_PPP_MULTILINK */
+	init_rwsem(&pch->chan_sem);
+	spin_lock_init(&pch->downl);
+	rwlock_init(&pch->upl);
+
+	spin_lock_bh(&pn->all_channels_lock);
+	pch->file.index = ++pn->last_channel_index;
+	list_add(&pch->list, &pn->new_channels);
+	atomic_inc(&channel_count);
+	spin_unlock_bh(&pn->all_channels_lock);
+
+	return 0;
+}
+
+/*
+ * Return the index of a channel.
+ */
+int ppp_channel_index(struct ppp_channel *chan)
+{
+	struct channel *pch = chan->ppp;
+
+	if (pch)
+		return pch->file.index;
+	return -1;
+}
+
+/*
+ * Return the PPP unit number to which a channel is connected.
+ */
+int ppp_unit_number(struct ppp_channel *chan)
+{
+	struct channel *pch = chan->ppp;
+	int unit = -1;
+
+	if (pch) {
+		read_lock_bh(&pch->upl);
+		if (pch->ppp)
+			unit = pch->ppp->file.index;
+		read_unlock_bh(&pch->upl);
+	}
+	return unit;
+}
+
+/*
+ * Return the PPP device interface name of a channel.
+ */
+char *ppp_dev_name(struct ppp_channel *chan)
+{
+	struct channel *pch = chan->ppp;
+	char *name = NULL;
+
+	if (pch) {
+		read_lock_bh(&pch->upl);
+		if (pch->ppp && pch->ppp->dev)
+			name = pch->ppp->dev->name;
+		read_unlock_bh(&pch->upl);
+	}
+	return name;
+}
+
+
+/*
+ * Disconnect a channel from the generic layer.
+ * This must be called in process context.
+ */
+void
+ppp_unregister_channel(struct ppp_channel *chan)
+{
+	struct channel *pch = chan->ppp;
+	struct ppp_net *pn;
+
+	if (!pch)
+		return;		/* should never happen */
+
+	chan->ppp = NULL;
+
+	/*
+	 * This ensures that we have returned from any calls into the
+	 * the channel's start_xmit or ioctl routine before we proceed.
+	 */
+	down_write(&pch->chan_sem);
+	spin_lock_bh(&pch->downl);
+	pch->chan = NULL;
+	spin_unlock_bh(&pch->downl);
+	up_write(&pch->chan_sem);
+	ppp_disconnect_channel(pch);
+
+	pn = ppp_pernet(pch->chan_net);
+	spin_lock_bh(&pn->all_channels_lock);
+	list_del(&pch->list);
+	spin_unlock_bh(&pn->all_channels_lock);
+
+	pch->file.dead = 1;
+	wake_up_interruptible(&pch->file.rwait);
+	if (refcount_dec_and_test(&pch->file.refcnt))
+		ppp_destroy_channel(pch);
+}
+
+/*
+ * Callback from a channel when it can accept more to transmit.
+ * This should be called at BH/softirq level, not interrupt level.
+ */
+void
+ppp_output_wakeup(struct ppp_channel *chan)
+{
+	struct channel *pch = chan->ppp;
+
+	if (!pch)
+		return;
+	ppp_channel_push(pch);
+}
+
+/*
+ * Compression control.
+ */
+
+/* Process the PPPIOCSCOMPRESS ioctl. */
+static int
+ppp_set_compress(struct ppp *ppp, struct ppp_option_data *data)
+{
+	int err = -EFAULT;
+	struct compressor *cp, *ocomp;
+	void *state, *ostate;
+	unsigned char ccp_option[CCP_MAX_OPTION_LENGTH];
+
+	if (data->length > CCP_MAX_OPTION_LENGTH)
+		goto out;
+	if (copy_from_user(ccp_option, data->ptr, data->length))
+		goto out;
+
+	err = -EINVAL;
+	if (data->length < 2 || ccp_option[1] < 2 || ccp_option[1] > data->length)
+		goto out;
+
+	cp = try_then_request_module(
+		find_compressor(ccp_option[0]),
+		"ppp-compress-%d", ccp_option[0]);
+	if (!cp)
+		goto out;
+
+	err = -ENOBUFS;
+	if (data->transmit) {
+		state = cp->comp_alloc(ccp_option, data->length);
+		if (state) {
+			ppp_xmit_lock(ppp);
+			ppp->xstate &= ~SC_COMP_RUN;
+			ocomp = ppp->xcomp;
+			ostate = ppp->xc_state;
+			ppp->xcomp = cp;
+			ppp->xc_state = state;
+			ppp_xmit_unlock(ppp);
+			if (ostate) {
+				ocomp->comp_free(ostate);
+				module_put(ocomp->owner);
+			}
+			err = 0;
+		} else
+			module_put(cp->owner);
+
+	} else {
+		state = cp->decomp_alloc(ccp_option, data->length);
+		if (state) {
+			ppp_recv_lock(ppp);
+			ppp->rstate &= ~SC_DECOMP_RUN;
+			ocomp = ppp->rcomp;
+			ostate = ppp->rc_state;
+			ppp->rcomp = cp;
+			ppp->rc_state = state;
+			ppp_recv_unlock(ppp);
+			if (ostate) {
+				ocomp->decomp_free(ostate);
+				module_put(ocomp->owner);
+			}
+			err = 0;
+		} else
+			module_put(cp->owner);
+	}
+
+ out:
+	return err;
+}
+
+/*
+ * Look at a CCP packet and update our state accordingly.
+ * We assume the caller has the xmit or recv path locked.
+ */
+static void
+ppp_ccp_peek(struct ppp *ppp, struct sk_buff *skb, int inbound)
+{
+	unsigned char *dp;
+	int len;
+
+	if (!pskb_may_pull(skb, CCP_HDRLEN + 2))
+		return;	/* no header */
+	dp = skb->data + 2;
+
+	switch (CCP_CODE(dp)) {
+	case CCP_CONFREQ:
+
+		/* A ConfReq starts negotiation of compression
+		 * in one direction of transmission,
+		 * and hence brings it down...but which way?
+		 *
+		 * Remember:
+		 * A ConfReq indicates what the sender would like to receive
+		 */
+		if(inbound)
+			/* He is proposing what I should send */
+			ppp->xstate &= ~SC_COMP_RUN;
+		else
+			/* I am proposing to what he should send */
+			ppp->rstate &= ~SC_DECOMP_RUN;
+
+		break;
+
+	case CCP_TERMREQ:
+	case CCP_TERMACK:
+		/*
+		 * CCP is going down, both directions of transmission
+		 */
+		ppp->rstate &= ~SC_DECOMP_RUN;
+		ppp->xstate &= ~SC_COMP_RUN;
+		break;
+
+	case CCP_CONFACK:
+		if ((ppp->flags & (SC_CCP_OPEN | SC_CCP_UP)) != SC_CCP_OPEN)
+			break;
+		len = CCP_LENGTH(dp);
+		if (!pskb_may_pull(skb, len + 2))
+			return;		/* too short */
+		dp += CCP_HDRLEN;
+		len -= CCP_HDRLEN;
+		if (len < CCP_OPT_MINLEN || len < CCP_OPT_LENGTH(dp))
+			break;
+		if (inbound) {
+			/* we will start receiving compressed packets */
+			if (!ppp->rc_state)
+				break;
+			if (ppp->rcomp->decomp_init(ppp->rc_state, dp, len,
+					ppp->file.index, 0, ppp->mru, ppp->debug)) {
+				ppp->rstate |= SC_DECOMP_RUN;
+				ppp->rstate &= ~(SC_DC_ERROR | SC_DC_FERROR);
+			}
+		} else {
+			/* we will soon start sending compressed packets */
+			if (!ppp->xc_state)
+				break;
+			if (ppp->xcomp->comp_init(ppp->xc_state, dp, len,
+					ppp->file.index, 0, ppp->debug))
+				ppp->xstate |= SC_COMP_RUN;
+		}
+		break;
+
+	case CCP_RESETACK:
+		/* reset the [de]compressor */
+		if ((ppp->flags & SC_CCP_UP) == 0)
+			break;
+		if (inbound) {
+			if (ppp->rc_state && (ppp->rstate & SC_DECOMP_RUN)) {
+				ppp->rcomp->decomp_reset(ppp->rc_state);
+				ppp->rstate &= ~SC_DC_ERROR;
+			}
+		} else {
+			if (ppp->xc_state && (ppp->xstate & SC_COMP_RUN))
+				ppp->xcomp->comp_reset(ppp->xc_state);
+		}
+		break;
+	}
+}
+
+/* Free up compression resources. */
+static void
+ppp_ccp_closed(struct ppp *ppp)
+{
+	void *xstate, *rstate;
+	struct compressor *xcomp, *rcomp;
+
+	ppp_lock(ppp);
+	ppp->flags &= ~(SC_CCP_OPEN | SC_CCP_UP);
+	ppp->xstate = 0;
+	xcomp = ppp->xcomp;
+	xstate = ppp->xc_state;
+	ppp->xc_state = NULL;
+	ppp->rstate = 0;
+	rcomp = ppp->rcomp;
+	rstate = ppp->rc_state;
+	ppp->rc_state = NULL;
+	ppp_unlock(ppp);
+
+	if (xstate) {
+		xcomp->comp_free(xstate);
+		module_put(xcomp->owner);
+	}
+	if (rstate) {
+		rcomp->decomp_free(rstate);
+		module_put(rcomp->owner);
+	}
+}
+
+/* List of compressors. */
+static LIST_HEAD(compressor_list);
+static DEFINE_SPINLOCK(compressor_list_lock);
+
+struct compressor_entry {
+	struct list_head list;
+	struct compressor *comp;
+};
+
+static struct compressor_entry *
+find_comp_entry(int proto)
+{
+	struct compressor_entry *ce;
+
+	list_for_each_entry(ce, &compressor_list, list) {
+		if (ce->comp->compress_proto == proto)
+			return ce;
+	}
+	return NULL;
+}
+
+/* Register a compressor */
+int
+ppp_register_compressor(struct compressor *cp)
+{
+	struct compressor_entry *ce;
+	int ret;
+	spin_lock(&compressor_list_lock);
+	ret = -EEXIST;
+	if (find_comp_entry(cp->compress_proto))
+		goto out;
+	ret = -ENOMEM;
+	ce = kmalloc(sizeof(struct compressor_entry), GFP_ATOMIC);
+	if (!ce)
+		goto out;
+	ret = 0;
+	ce->comp = cp;
+	list_add(&ce->list, &compressor_list);
+ out:
+	spin_unlock(&compressor_list_lock);
+	return ret;
+}
+
+/* Unregister a compressor */
+void
+ppp_unregister_compressor(struct compressor *cp)
+{
+	struct compressor_entry *ce;
+
+	spin_lock(&compressor_list_lock);
+	ce = find_comp_entry(cp->compress_proto);
+	if (ce && ce->comp == cp) {
+		list_del(&ce->list);
+		kfree(ce);
+	}
+	spin_unlock(&compressor_list_lock);
+}
+
+/* Find a compressor. */
+static struct compressor *
+find_compressor(int type)
+{
+	struct compressor_entry *ce;
+	struct compressor *cp = NULL;
+
+	spin_lock(&compressor_list_lock);
+	ce = find_comp_entry(type);
+	if (ce) {
+		cp = ce->comp;
+		if (!try_module_get(cp->owner))
+			cp = NULL;
+	}
+	spin_unlock(&compressor_list_lock);
+	return cp;
+}
+
+/*
+ * Miscelleneous stuff.
+ */
+
+static void
+ppp_get_stats(struct ppp *ppp, struct ppp_stats *st)
+{
+	struct slcompress *vj = ppp->vj;
+
+	memset(st, 0, sizeof(*st));
+	st->p.ppp_ipackets = ppp->stats64.rx_packets;
+	st->p.ppp_ierrors = ppp->dev->stats.rx_errors;
+	st->p.ppp_ibytes = ppp->stats64.rx_bytes;
+	st->p.ppp_opackets = ppp->stats64.tx_packets;
+	st->p.ppp_oerrors = ppp->dev->stats.tx_errors;
+	st->p.ppp_obytes = ppp->stats64.tx_bytes;
+	if (!vj)
+		return;
+	st->vj.vjs_packets = vj->sls_o_compressed + vj->sls_o_uncompressed;
+	st->vj.vjs_compressed = vj->sls_o_compressed;
+	st->vj.vjs_searches = vj->sls_o_searches;
+	st->vj.vjs_misses = vj->sls_o_misses;
+	st->vj.vjs_errorin = vj->sls_i_error;
+	st->vj.vjs_tossed = vj->sls_i_tossed;
+	st->vj.vjs_uncompressedin = vj->sls_i_uncompressed;
+	st->vj.vjs_compressedin = vj->sls_i_compressed;
+}
+
+/*
+ * Stuff for handling the lists of ppp units and channels
+ * and for initialization.
+ */
+
+/*
+ * Create a new ppp interface unit.  Fails if it can't allocate memory
+ * or if there is already a unit with the requested number.
+ * unit == -1 means allocate a new number.
+ */
+static int ppp_create_interface(struct net *net, struct file *file, int *unit)
+{
+	struct ppp_config conf = {
+		.file = file,
+		.unit = *unit,
+		.ifname_is_set = false,
+	};
+	struct net_device *dev;
+	struct ppp *ppp;
+	int err;
+
+	dev = alloc_netdev(sizeof(struct ppp), "", NET_NAME_ENUM, ppp_setup);
+	if (!dev) {
+		err = -ENOMEM;
+		goto err;
+	}
+	dev_net_set(dev, net);
+	dev->rtnl_link_ops = &ppp_link_ops;
+
+	rtnl_lock();
+
+	err = ppp_dev_configure(net, dev, &conf);
+	if (err < 0)
+		goto err_dev;
+	ppp = netdev_priv(dev);
+	*unit = ppp->file.index;
+
+	rtnl_unlock();
+
+	return 0;
+
+err_dev:
+	rtnl_unlock();
+	free_netdev(dev);
+err:
+	return err;
+}
+
+/*
+ * Initialize a ppp_file structure.
+ */
+static void
+init_ppp_file(struct ppp_file *pf, int kind)
+{
+	pf->kind = kind;
+	skb_queue_head_init(&pf->xq);
+	skb_queue_head_init(&pf->rq);
+	refcount_set(&pf->refcnt, 1);
+	init_waitqueue_head(&pf->rwait);
+}
+
+/*
+ * Free the memory used by a ppp unit.  This is only called once
+ * there are no channels connected to the unit and no file structs
+ * that reference the unit.
+ */
+static void ppp_destroy_interface(struct ppp *ppp)
+{
+	atomic_dec(&ppp_unit_count);
+
+	if (!ppp->file.dead || ppp->n_channels) {
+		/* "can't happen" */
+		netdev_err(ppp->dev, "ppp: destroying ppp struct %p "
+			   "but dead=%d n_channels=%d !\n",
+			   ppp, ppp->file.dead, ppp->n_channels);
+		return;
+	}
+
+	ppp_ccp_closed(ppp);
+	if (ppp->vj) {
+		slhc_free(ppp->vj);
+		ppp->vj = NULL;
+	}
+	skb_queue_purge(&ppp->file.xq);
+	skb_queue_purge(&ppp->file.rq);
+#ifdef CONFIG_PPP_MULTILINK
+	skb_queue_purge(&ppp->mrq);
+#endif /* CONFIG_PPP_MULTILINK */
+#ifdef CONFIG_PPP_FILTER
+	if (ppp->pass_filter) {
+		bpf_prog_destroy(ppp->pass_filter);
+		ppp->pass_filter = NULL;
+	}
+
+	if (ppp->active_filter) {
+		bpf_prog_destroy(ppp->active_filter);
+		ppp->active_filter = NULL;
+	}
+#endif /* CONFIG_PPP_FILTER */
+
+	kfree_skb(ppp->xmit_pending);
+	free_percpu(ppp->xmit_recursion);
+
+	free_netdev(ppp->dev);
+}
+
+/*
+ * Locate an existing ppp unit.
+ * The caller should have locked the all_ppp_mutex.
+ */
+static struct ppp *
+ppp_find_unit(struct ppp_net *pn, int unit)
+{
+	return unit_find(&pn->units_idr, unit);
+}
+
+/*
+ * Locate an existing ppp channel.
+ * The caller should have locked the all_channels_lock.
+ * First we look in the new_channels list, then in the
+ * all_channels list.  If found in the new_channels list,
+ * we move it to the all_channels list.  This is for speed
+ * when we have a lot of channels in use.
+ */
+static struct channel *
+ppp_find_channel(struct ppp_net *pn, int unit)
+{
+	struct channel *pch;
+
+	list_for_each_entry(pch, &pn->new_channels, list) {
+		if (pch->file.index == unit) {
+			list_move(&pch->list, &pn->all_channels);
+			return pch;
+		}
+	}
+
+	list_for_each_entry(pch, &pn->all_channels, list) {
+		if (pch->file.index == unit)
+			return pch;
+	}
+
+	return NULL;
+}
+
+/*
+ * Connect a PPP channel to a PPP interface unit.
+ */
+static int
+ppp_connect_channel(struct channel *pch, int unit)
+{
+	struct ppp *ppp;
+	struct ppp_net *pn;
+	int ret = -ENXIO;
+	int hdrlen;
+
+	pn = ppp_pernet(pch->chan_net);
+
+	mutex_lock(&pn->all_ppp_mutex);
+	ppp = ppp_find_unit(pn, unit);
+	if (!ppp)
+		goto out;
+	write_lock_bh(&pch->upl);
+	ret = -EINVAL;
+	if (pch->ppp)
+		goto outl;
+
+	ppp_lock(ppp);
+	spin_lock_bh(&pch->downl);
+	if (!pch->chan) {
+		/* Don't connect unregistered channels */
+		spin_unlock_bh(&pch->downl);
+		ppp_unlock(ppp);
+		ret = -ENOTCONN;
+		goto outl;
+	}
+	spin_unlock_bh(&pch->downl);
+	if (pch->file.hdrlen > ppp->file.hdrlen)
+		ppp->file.hdrlen = pch->file.hdrlen;
+	hdrlen = pch->file.hdrlen + 2;	/* for protocol bytes */
+	if (hdrlen > ppp->dev->hard_header_len)
+		ppp->dev->hard_header_len = hdrlen;
+	list_add_tail(&pch->clist, &ppp->channels);
+	++ppp->n_channels;
+	pch->ppp = ppp;
+	refcount_inc(&ppp->file.refcnt);
+	ppp_unlock(ppp);
+	ret = 0;
+
+ outl:
+	write_unlock_bh(&pch->upl);
+ out:
+	mutex_unlock(&pn->all_ppp_mutex);
+	return ret;
+}
+
+/*
+ * Disconnect a channel from its ppp unit.
+ */
+static int
+ppp_disconnect_channel(struct channel *pch)
+{
+	struct ppp *ppp;
+	int err = -EINVAL;
+
+	write_lock_bh(&pch->upl);
+	ppp = pch->ppp;
+	pch->ppp = NULL;
+	write_unlock_bh(&pch->upl);
+	if (ppp) {
+		/* remove it from the ppp unit's list */
+		ppp_lock(ppp);
+		list_del(&pch->clist);
+		if (--ppp->n_channels == 0)
+			wake_up_interruptible(&ppp->file.rwait);
+		ppp_unlock(ppp);
+		if (refcount_dec_and_test(&ppp->file.refcnt))
+			ppp_destroy_interface(ppp);
+		err = 0;
+	}
+	return err;
+}
+
+/*
+ * Free up the resources used by a ppp channel.
+ */
+static void ppp_destroy_channel(struct channel *pch)
+{
+	put_net(pch->chan_net);
+	pch->chan_net = NULL;
+
+	atomic_dec(&channel_count);
+
+	if (!pch->file.dead) {
+		/* "can't happen" */
+		pr_err("ppp: destroying undead channel %p !\n", pch);
+		return;
+	}
+	skb_queue_purge(&pch->file.xq);
+	skb_queue_purge(&pch->file.rq);
+	kfree(pch);
+}
+
+static void __exit ppp_cleanup(void)
+{
+	/* should never happen */
+	if (atomic_read(&ppp_unit_count) || atomic_read(&channel_count))
+		pr_err("PPP: removing module but units remain!\n");
+	rtnl_link_unregister(&ppp_link_ops);
+	unregister_chrdev(PPP_MAJOR, "ppp");
+	device_destroy(ppp_class, MKDEV(PPP_MAJOR, 0));
+	class_destroy(ppp_class);
+	unregister_pernet_device(&ppp_net_ops);
+}
+
+/*
+ * Units handling. Caller must protect concurrent access
+ * by holding all_ppp_mutex
+ */
+
+/* associate pointer with specified number */
+static int unit_set(struct idr *p, void *ptr, int n)
+{
+	int unit;
+
+	unit = idr_alloc(p, ptr, n, n + 1, GFP_KERNEL);
+	if (unit == -ENOSPC)
+		unit = -EINVAL;
+	return unit;
+}
+
+/* get new free unit number and associate pointer with it */
+static int unit_get(struct idr *p, void *ptr, int min)
+{
+	return idr_alloc(p, ptr, min, 0, GFP_KERNEL);
+}
+
+/* put unit number back to a pool */
+static void unit_put(struct idr *p, int n)
+{
+	idr_remove(p, n);
+}
+
+/* get pointer associated with the number */
+static void *unit_find(struct idr *p, int n)
+{
+	return idr_find(p, n);
+}
+
+/* Module/initialization stuff */
+
+module_init(ppp_init);
+module_exit(ppp_cleanup);
+
+EXPORT_SYMBOL(ppp_register_net_channel);
+EXPORT_SYMBOL(ppp_register_channel);
+EXPORT_SYMBOL(ppp_unregister_channel);
+EXPORT_SYMBOL(ppp_channel_index);
+EXPORT_SYMBOL(ppp_unit_number);
+EXPORT_SYMBOL(ppp_dev_name);
+EXPORT_SYMBOL(ppp_input);
+EXPORT_SYMBOL(ppp_input_error);
+EXPORT_SYMBOL(ppp_output_wakeup);
+EXPORT_SYMBOL(ppp_register_compressor);
+EXPORT_SYMBOL(ppp_unregister_compressor);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_CHARDEV(PPP_MAJOR, 0);
+MODULE_ALIAS_RTNL_LINK("ppp");
+MODULE_ALIAS("devname:ppp");