Adding upstream version 6.1.76.upstream/6.1.76

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

14 files changed, 4778 insertions, 0 deletions

diff --git a/net/x25/Kconfig b/net/x25/Kconfig
new file mode 100644
index 000000000..68729aa3a
--- /dev/null
+++ b/net/x25/Kconfig
@@ -0,0 +1,34 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# CCITT X.25 Packet Layer
+#
+
+config X25
+	tristate "CCITT X.25 Packet Layer"
+	help
+	  X.25 is a set of standardized network protocols, similar in scope to
+	  frame relay; the one physical line from your box to the X.25 network
+	  entry point can carry several logical point-to-point connections
+	  (called "virtual circuits") to other computers connected to the X.25
+	  network. Governments, banks, and other organizations tend to use it
+	  to connect to each other or to form Wide Area Networks (WANs). Many
+	  countries have public X.25 networks. X.25 consists of two
+	  protocols: the higher level Packet Layer Protocol (PLP) (say Y here
+	  if you want that) and the lower level data link layer protocol LAPB
+	  (say Y to "LAPB Data Link Driver" below if you want that).
+
+	  You can read more about X.25 at <https://www.sangoma.com/tutorials/x25/> and
+	  <http://docwiki.cisco.com/wiki/X.25>.
+	  Information about X.25 for Linux is contained in the files
+	  <file:Documentation/networking/x25.rst> and
+	  <file:Documentation/networking/x25-iface.rst>.
+
+	  One connects to an X.25 network either with a dedicated network card
+	  using the X.21 protocol (not yet supported by Linux) or one can do
+	  X.25 over a standard telephone line using an ordinary modem (say Y
+	  to "X.25 async driver" below) or over Ethernet using an ordinary
+	  Ethernet card and the LAPB over Ethernet (say Y to "LAPB Data Link
+	  Driver" and "LAPB over Ethernet driver" below).
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called x25. If unsure, say N.
diff --git a/net/x25/Makefile b/net/x25/Makefile
new file mode 100644
index 000000000..5dd544a23
--- /dev/null
+++ b/net/x25/Makefile
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the Linux X.25 Packet layer.
+#
+
+obj-$(CONFIG_X25) += x25.o
+
+x25-y			:= af_x25.o x25_dev.o x25_facilities.o x25_in.o \
+			   x25_link.o x25_out.o x25_route.o x25_subr.o \
+			   x25_timer.o x25_proc.o x25_forward.o
+x25-$(CONFIG_SYSCTL)	+= sysctl_net_x25.o
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
new file mode 100644
index 000000000..5c7ad301d
--- /dev/null
+++ b/net/x25/af_x25.c
@@ -0,0 +1,1856 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine,
+ *	randomly fail to work with new releases, misbehave and/or generally
+ *	screw up. It might even work.
+ *
+ *	This code REQUIRES 2.1.15 or higher
+ *
+ *	History
+ *	X.25 001	Jonathan Naylor	Started coding.
+ *	X.25 002	Jonathan Naylor	Centralised disconnect handling.
+ *					New timer architecture.
+ *	2000-03-11	Henner Eisen	MSG_EOR handling more POSIX compliant.
+ *	2000-03-22	Daniela Squassoni Allowed disabling/enabling of
+ *					  facilities negotiation and increased
+ *					  the throughput upper limit.
+ *	2000-08-27	Arnaldo C. Melo s/suser/capable/ + micro cleanups
+ *	2000-09-04	Henner Eisen	Set sock->state in x25_accept().
+ *					Fixed x25_output() related skb leakage.
+ *	2000-10-02	Henner Eisen	Made x25_kick() single threaded per socket.
+ *	2000-10-27	Henner Eisen    MSG_DONTWAIT for fragment allocation.
+ *	2000-11-14	Henner Eisen    Closing datalink from NETDEV_GOING_DOWN
+ *	2002-10-06	Arnaldo C. Melo Get rid of cli/sti, move proc stuff to
+ *					x25_proc.c, using seq_file
+ *	2005-04-02	Shaun Pereira	Selective sub address matching
+ *					with call user data
+ *	2005-04-15	Shaun Pereira	Fast select with no restriction on
+ *					response
+ */
+
+#define pr_fmt(fmt) "X25: " fmt
+
+#include <linux/module.h>
+#include <linux/capability.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/sched/signal.h>
+#include <linux/timer.h>
+#include <linux/string.h>
+#include <linux/net.h>
+#include <linux/netdevice.h>
+#include <linux/if_arp.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <net/sock.h>
+#include <net/tcp_states.h>
+#include <linux/uaccess.h>
+#include <linux/fcntl.h>
+#include <linux/termios.h>	/* For TIOCINQ/OUTQ */
+#include <linux/notifier.h>
+#include <linux/init.h>
+#include <linux/compat.h>
+#include <linux/ctype.h>
+
+#include <net/x25.h>
+#include <net/compat.h>
+
+int sysctl_x25_restart_request_timeout = X25_DEFAULT_T20;
+int sysctl_x25_call_request_timeout    = X25_DEFAULT_T21;
+int sysctl_x25_reset_request_timeout   = X25_DEFAULT_T22;
+int sysctl_x25_clear_request_timeout   = X25_DEFAULT_T23;
+int sysctl_x25_ack_holdback_timeout    = X25_DEFAULT_T2;
+int sysctl_x25_forward                 = 0;
+
+HLIST_HEAD(x25_list);
+DEFINE_RWLOCK(x25_list_lock);
+
+static const struct proto_ops x25_proto_ops;
+
+static const struct x25_address null_x25_address = {"               "};
+
+#ifdef CONFIG_COMPAT
+struct compat_x25_subscrip_struct {
+	char device[200-sizeof(compat_ulong_t)];
+	compat_ulong_t global_facil_mask;
+	compat_uint_t extended;
+};
+#endif
+
+
+int x25_parse_address_block(struct sk_buff *skb,
+		struct x25_address *called_addr,
+		struct x25_address *calling_addr)
+{
+	unsigned char len;
+	int needed;
+	int rc;
+
+	if (!pskb_may_pull(skb, 1)) {
+		/* packet has no address block */
+		rc = 0;
+		goto empty;
+	}
+
+	len = *skb->data;
+	needed = 1 + ((len >> 4) + (len & 0x0f) + 1) / 2;
+
+	if (!pskb_may_pull(skb, needed)) {
+		/* packet is too short to hold the addresses it claims
+		   to hold */
+		rc = -1;
+		goto empty;
+	}
+
+	return x25_addr_ntoa(skb->data, called_addr, calling_addr);
+
+empty:
+	*called_addr->x25_addr = 0;
+	*calling_addr->x25_addr = 0;
+
+	return rc;
+}
+
+
+int x25_addr_ntoa(unsigned char *p, struct x25_address *called_addr,
+		  struct x25_address *calling_addr)
+{
+	unsigned int called_len, calling_len;
+	char *called, *calling;
+	unsigned int i;
+
+	called_len  = (*p >> 0) & 0x0F;
+	calling_len = (*p >> 4) & 0x0F;
+
+	called  = called_addr->x25_addr;
+	calling = calling_addr->x25_addr;
+	p++;
+
+	for (i = 0; i < (called_len + calling_len); i++) {
+		if (i < called_len) {
+			if (i % 2 != 0) {
+				*called++ = ((*p >> 0) & 0x0F) + '0';
+				p++;
+			} else {
+				*called++ = ((*p >> 4) & 0x0F) + '0';
+			}
+		} else {
+			if (i % 2 != 0) {
+				*calling++ = ((*p >> 0) & 0x0F) + '0';
+				p++;
+			} else {
+				*calling++ = ((*p >> 4) & 0x0F) + '0';
+			}
+		}
+	}
+
+	*called = *calling = '\0';
+
+	return 1 + (called_len + calling_len + 1) / 2;
+}
+
+int x25_addr_aton(unsigned char *p, struct x25_address *called_addr,
+		  struct x25_address *calling_addr)
+{
+	unsigned int called_len, calling_len;
+	char *called, *calling;
+	int i;
+
+	called  = called_addr->x25_addr;
+	calling = calling_addr->x25_addr;
+
+	called_len  = strlen(called);
+	calling_len = strlen(calling);
+
+	*p++ = (calling_len << 4) | (called_len << 0);
+
+	for (i = 0; i < (called_len + calling_len); i++) {
+		if (i < called_len) {
+			if (i % 2 != 0) {
+				*p |= (*called++ - '0') << 0;
+				p++;
+			} else {
+				*p = 0x00;
+				*p |= (*called++ - '0') << 4;
+			}
+		} else {
+			if (i % 2 != 0) {
+				*p |= (*calling++ - '0') << 0;
+				p++;
+			} else {
+				*p = 0x00;
+				*p |= (*calling++ - '0') << 4;
+			}
+		}
+	}
+
+	return 1 + (called_len + calling_len + 1) / 2;
+}
+
+/*
+ *	Socket removal during an interrupt is now safe.
+ */
+static void x25_remove_socket(struct sock *sk)
+{
+	write_lock_bh(&x25_list_lock);
+	sk_del_node_init(sk);
+	write_unlock_bh(&x25_list_lock);
+}
+
+/*
+ *	Handle device status changes.
+ */
+static int x25_device_event(struct notifier_block *this, unsigned long event,
+			    void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct x25_neigh *nb;
+
+	if (!net_eq(dev_net(dev), &init_net))
+		return NOTIFY_DONE;
+
+	if (dev->type == ARPHRD_X25) {
+		switch (event) {
+		case NETDEV_REGISTER:
+		case NETDEV_POST_TYPE_CHANGE:
+			x25_link_device_up(dev);
+			break;
+		case NETDEV_DOWN:
+			nb = x25_get_neigh(dev);
+			if (nb) {
+				x25_link_terminated(nb);
+				x25_neigh_put(nb);
+			}
+			x25_route_device_down(dev);
+			break;
+		case NETDEV_PRE_TYPE_CHANGE:
+		case NETDEV_UNREGISTER:
+			x25_link_device_down(dev);
+			break;
+		case NETDEV_CHANGE:
+			if (!netif_carrier_ok(dev)) {
+				nb = x25_get_neigh(dev);
+				if (nb) {
+					x25_link_terminated(nb);
+					x25_neigh_put(nb);
+				}
+			}
+			break;
+		}
+	}
+
+	return NOTIFY_DONE;
+}
+
+/*
+ *	Add a socket to the bound sockets list.
+ */
+static void x25_insert_socket(struct sock *sk)
+{
+	write_lock_bh(&x25_list_lock);
+	sk_add_node(sk, &x25_list);
+	write_unlock_bh(&x25_list_lock);
+}
+
+/*
+ *	Find a socket that wants to accept the Call Request we just
+ *	received. Check the full list for an address/cud match.
+ *	If no cuds match return the next_best thing, an address match.
+ *	Note: if a listening socket has cud set it must only get calls
+ *	with matching cud.
+ */
+static struct sock *x25_find_listener(struct x25_address *addr,
+					struct sk_buff *skb)
+{
+	struct sock *s;
+	struct sock *next_best;
+
+	read_lock_bh(&x25_list_lock);
+	next_best = NULL;
+
+	sk_for_each(s, &x25_list)
+		if ((!strcmp(addr->x25_addr,
+			x25_sk(s)->source_addr.x25_addr) ||
+				!strcmp(x25_sk(s)->source_addr.x25_addr,
+					null_x25_address.x25_addr)) &&
+					s->sk_state == TCP_LISTEN) {
+			/*
+			 * Found a listening socket, now check the incoming
+			 * call user data vs this sockets call user data
+			 */
+			if (x25_sk(s)->cudmatchlength > 0 &&
+				skb->len >= x25_sk(s)->cudmatchlength) {
+				if((memcmp(x25_sk(s)->calluserdata.cuddata,
+					skb->data,
+					x25_sk(s)->cudmatchlength)) == 0) {
+					sock_hold(s);
+					goto found;
+				 }
+			} else
+				next_best = s;
+		}
+	if (next_best) {
+		s = next_best;
+		sock_hold(s);
+		goto found;
+	}
+	s = NULL;
+found:
+	read_unlock_bh(&x25_list_lock);
+	return s;
+}
+
+/*
+ *	Find a connected X.25 socket given my LCI and neighbour.
+ */
+static struct sock *__x25_find_socket(unsigned int lci, struct x25_neigh *nb)
+{
+	struct sock *s;
+
+	sk_for_each(s, &x25_list)
+		if (x25_sk(s)->lci == lci && x25_sk(s)->neighbour == nb) {
+			sock_hold(s);
+			goto found;
+		}
+	s = NULL;
+found:
+	return s;
+}
+
+struct sock *x25_find_socket(unsigned int lci, struct x25_neigh *nb)
+{
+	struct sock *s;
+
+	read_lock_bh(&x25_list_lock);
+	s = __x25_find_socket(lci, nb);
+	read_unlock_bh(&x25_list_lock);
+	return s;
+}
+
+/*
+ *	Find a unique LCI for a given device.
+ */
+static unsigned int x25_new_lci(struct x25_neigh *nb)
+{
+	unsigned int lci = 1;
+	struct sock *sk;
+
+	while ((sk = x25_find_socket(lci, nb)) != NULL) {
+		sock_put(sk);
+		if (++lci == 4096) {
+			lci = 0;
+			break;
+		}
+		cond_resched();
+	}
+
+	return lci;
+}
+
+/*
+ *	Deferred destroy.
+ */
+static void __x25_destroy_socket(struct sock *);
+
+/*
+ *	handler for deferred kills.
+ */
+static void x25_destroy_timer(struct timer_list *t)
+{
+	struct sock *sk = from_timer(sk, t, sk_timer);
+
+	x25_destroy_socket_from_timer(sk);
+}
+
+/*
+ *	This is called from user mode and the timers. Thus it protects itself
+ *	against interrupting users but doesn't worry about being called during
+ *	work. Once it is removed from the queue no interrupt or bottom half
+ *	will touch it and we are (fairly 8-) ) safe.
+ *	Not static as it's used by the timer
+ */
+static void __x25_destroy_socket(struct sock *sk)
+{
+	struct sk_buff *skb;
+
+	x25_stop_heartbeat(sk);
+	x25_stop_timer(sk);
+
+	x25_remove_socket(sk);
+	x25_clear_queues(sk);		/* Flush the queues */
+
+	while ((skb = skb_dequeue(&sk->sk_receive_queue)) != NULL) {
+		if (skb->sk != sk) {		/* A pending connection */
+			/*
+			 * Queue the unaccepted socket for death
+			 */
+			skb->sk->sk_state = TCP_LISTEN;
+			sock_set_flag(skb->sk, SOCK_DEAD);
+			x25_start_heartbeat(skb->sk);
+			x25_sk(skb->sk)->state = X25_STATE_0;
+		}
+
+		kfree_skb(skb);
+	}
+
+	if (sk_has_allocations(sk)) {
+		/* Defer: outstanding buffers */
+		sk->sk_timer.expires  = jiffies + 10 * HZ;
+		sk->sk_timer.function = x25_destroy_timer;
+		add_timer(&sk->sk_timer);
+	} else {
+		/* drop last reference so sock_put will free */
+		__sock_put(sk);
+	}
+}
+
+void x25_destroy_socket_from_timer(struct sock *sk)
+{
+	sock_hold(sk);
+	bh_lock_sock(sk);
+	__x25_destroy_socket(sk);
+	bh_unlock_sock(sk);
+	sock_put(sk);
+}
+
+/*
+ *	Handling for system calls applied via the various interfaces to a
+ *	X.25 socket object.
+ */
+
+static int x25_setsockopt(struct socket *sock, int level, int optname,
+			  sockptr_t optval, unsigned int optlen)
+{
+	int opt;
+	struct sock *sk = sock->sk;
+	int rc = -ENOPROTOOPT;
+
+	if (level != SOL_X25 || optname != X25_QBITINCL)
+		goto out;
+
+	rc = -EINVAL;
+	if (optlen < sizeof(int))
+		goto out;
+
+	rc = -EFAULT;
+	if (copy_from_sockptr(&opt, optval, sizeof(int)))
+		goto out;
+
+	if (opt)
+		set_bit(X25_Q_BIT_FLAG, &x25_sk(sk)->flags);
+	else
+		clear_bit(X25_Q_BIT_FLAG, &x25_sk(sk)->flags);
+	rc = 0;
+out:
+	return rc;
+}
+
+static int x25_getsockopt(struct socket *sock, int level, int optname,
+			  char __user *optval, int __user *optlen)
+{
+	struct sock *sk = sock->sk;
+	int val, len, rc = -ENOPROTOOPT;
+
+	if (level != SOL_X25 || optname != X25_QBITINCL)
+		goto out;
+
+	rc = -EFAULT;
+	if (get_user(len, optlen))
+		goto out;
+
+	len = min_t(unsigned int, len, sizeof(int));
+
+	rc = -EINVAL;
+	if (len < 0)
+		goto out;
+
+	rc = -EFAULT;
+	if (put_user(len, optlen))
+		goto out;
+
+	val = test_bit(X25_Q_BIT_FLAG, &x25_sk(sk)->flags);
+	rc = copy_to_user(optval, &val, len) ? -EFAULT : 0;
+out:
+	return rc;
+}
+
+static int x25_listen(struct socket *sock, int backlog)
+{
+	struct sock *sk = sock->sk;
+	int rc = -EOPNOTSUPP;
+
+	lock_sock(sk);
+	if (sock->state != SS_UNCONNECTED) {
+		rc = -EINVAL;
+		release_sock(sk);
+		return rc;
+	}
+
+	if (sk->sk_state != TCP_LISTEN) {
+		memset(&x25_sk(sk)->dest_addr, 0, X25_ADDR_LEN);
+		sk->sk_max_ack_backlog = backlog;
+		sk->sk_state           = TCP_LISTEN;
+		rc = 0;
+	}
+	release_sock(sk);
+
+	return rc;
+}
+
+static struct proto x25_proto = {
+	.name	  = "X25",
+	.owner	  = THIS_MODULE,
+	.obj_size = sizeof(struct x25_sock),
+};
+
+static struct sock *x25_alloc_socket(struct net *net, int kern)
+{
+	struct x25_sock *x25;
+	struct sock *sk = sk_alloc(net, AF_X25, GFP_ATOMIC, &x25_proto, kern);
+
+	if (!sk)
+		goto out;
+
+	sock_init_data(NULL, sk);
+
+	x25 = x25_sk(sk);
+	skb_queue_head_init(&x25->ack_queue);
+	skb_queue_head_init(&x25->fragment_queue);
+	skb_queue_head_init(&x25->interrupt_in_queue);
+	skb_queue_head_init(&x25->interrupt_out_queue);
+out:
+	return sk;
+}
+
+static int x25_create(struct net *net, struct socket *sock, int protocol,
+		      int kern)
+{
+	struct sock *sk;
+	struct x25_sock *x25;
+	int rc = -EAFNOSUPPORT;
+
+	if (!net_eq(net, &init_net))
+		goto out;
+
+	rc = -ESOCKTNOSUPPORT;
+	if (sock->type != SOCK_SEQPACKET)
+		goto out;
+
+	rc = -EINVAL;
+	if (protocol)
+		goto out;
+
+	rc = -ENOMEM;
+	if ((sk = x25_alloc_socket(net, kern)) == NULL)
+		goto out;
+
+	x25 = x25_sk(sk);
+
+	sock_init_data(sock, sk);
+
+	x25_init_timers(sk);
+
+	sock->ops    = &x25_proto_ops;
+	sk->sk_protocol = protocol;
+	sk->sk_backlog_rcv = x25_backlog_rcv;
+
+	x25->t21   = sysctl_x25_call_request_timeout;
+	x25->t22   = sysctl_x25_reset_request_timeout;
+	x25->t23   = sysctl_x25_clear_request_timeout;
+	x25->t2    = sysctl_x25_ack_holdback_timeout;
+	x25->state = X25_STATE_0;
+	x25->cudmatchlength = 0;
+	set_bit(X25_ACCPT_APPRV_FLAG, &x25->flags);	/* normally no cud  */
+							/* on call accept   */
+
+	x25->facilities.winsize_in  = X25_DEFAULT_WINDOW_SIZE;
+	x25->facilities.winsize_out = X25_DEFAULT_WINDOW_SIZE;
+	x25->facilities.pacsize_in  = X25_DEFAULT_PACKET_SIZE;
+	x25->facilities.pacsize_out = X25_DEFAULT_PACKET_SIZE;
+	x25->facilities.throughput  = 0;	/* by default don't negotiate
+						   throughput */
+	x25->facilities.reverse     = X25_DEFAULT_REVERSE;
+	x25->dte_facilities.calling_len = 0;
+	x25->dte_facilities.called_len = 0;
+	memset(x25->dte_facilities.called_ae, '\0',
+			sizeof(x25->dte_facilities.called_ae));
+	memset(x25->dte_facilities.calling_ae, '\0',
+			sizeof(x25->dte_facilities.calling_ae));
+
+	rc = 0;
+out:
+	return rc;
+}
+
+static struct sock *x25_make_new(struct sock *osk)
+{
+	struct sock *sk = NULL;
+	struct x25_sock *x25, *ox25;
+
+	if (osk->sk_type != SOCK_SEQPACKET)
+		goto out;
+
+	if ((sk = x25_alloc_socket(sock_net(osk), 0)) == NULL)
+		goto out;
+
+	x25 = x25_sk(sk);
+
+	sk->sk_type        = osk->sk_type;
+	sk->sk_priority    = osk->sk_priority;
+	sk->sk_protocol    = osk->sk_protocol;
+	sk->sk_rcvbuf      = osk->sk_rcvbuf;
+	sk->sk_sndbuf      = osk->sk_sndbuf;
+	sk->sk_state       = TCP_ESTABLISHED;
+	sk->sk_backlog_rcv = osk->sk_backlog_rcv;
+	sock_copy_flags(sk, osk);
+
+	ox25 = x25_sk(osk);
+	x25->t21        = ox25->t21;
+	x25->t22        = ox25->t22;
+	x25->t23        = ox25->t23;
+	x25->t2         = ox25->t2;
+	x25->flags	= ox25->flags;
+	x25->facilities = ox25->facilities;
+	x25->dte_facilities = ox25->dte_facilities;
+	x25->cudmatchlength = ox25->cudmatchlength;
+
+	clear_bit(X25_INTERRUPT_FLAG, &x25->flags);
+	x25_init_timers(sk);
+out:
+	return sk;
+}
+
+static int x25_release(struct socket *sock)
+{
+	struct sock *sk = sock->sk;
+	struct x25_sock *x25;
+
+	if (!sk)
+		return 0;
+
+	x25 = x25_sk(sk);
+
+	sock_hold(sk);
+	lock_sock(sk);
+	switch (x25->state) {
+
+		case X25_STATE_0:
+		case X25_STATE_2:
+			x25_disconnect(sk, 0, 0, 0);
+			__x25_destroy_socket(sk);
+			goto out;
+
+		case X25_STATE_1:
+		case X25_STATE_3:
+		case X25_STATE_4:
+			x25_clear_queues(sk);
+			x25_write_internal(sk, X25_CLEAR_REQUEST);
+			x25_start_t23timer(sk);
+			x25->state = X25_STATE_2;
+			sk->sk_state	= TCP_CLOSE;
+			sk->sk_shutdown	|= SEND_SHUTDOWN;
+			sk->sk_state_change(sk);
+			sock_set_flag(sk, SOCK_DEAD);
+			sock_set_flag(sk, SOCK_DESTROY);
+			break;
+
+		case X25_STATE_5:
+			x25_write_internal(sk, X25_CLEAR_REQUEST);
+			x25_disconnect(sk, 0, 0, 0);
+			__x25_destroy_socket(sk);
+			goto out;
+	}
+
+	sock_orphan(sk);
+out:
+	release_sock(sk);
+	sock_put(sk);
+	return 0;
+}
+
+static int x25_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
+{
+	struct sock *sk = sock->sk;
+	struct sockaddr_x25 *addr = (struct sockaddr_x25 *)uaddr;
+	int len, i, rc = 0;
+
+	if (addr_len != sizeof(struct sockaddr_x25) ||
+	    addr->sx25_family != AF_X25 ||
+	    strnlen(addr->sx25_addr.x25_addr, X25_ADDR_LEN) == X25_ADDR_LEN) {
+		rc = -EINVAL;
+		goto out;
+	}
+
+	/* check for the null_x25_address */
+	if (strcmp(addr->sx25_addr.x25_addr, null_x25_address.x25_addr)) {
+
+		len = strlen(addr->sx25_addr.x25_addr);
+		for (i = 0; i < len; i++) {
+			if (!isdigit(addr->sx25_addr.x25_addr[i])) {
+				rc = -EINVAL;
+				goto out;
+			}
+		}
+	}
+
+	lock_sock(sk);
+	if (sock_flag(sk, SOCK_ZAPPED)) {
+		x25_sk(sk)->source_addr = addr->sx25_addr;
+		x25_insert_socket(sk);
+		sock_reset_flag(sk, SOCK_ZAPPED);
+	} else {
+		rc = -EINVAL;
+	}
+	release_sock(sk);
+	SOCK_DEBUG(sk, "x25_bind: socket is bound\n");
+out:
+	return rc;
+}
+
+static int x25_wait_for_connection_establishment(struct sock *sk)
+{
+	DECLARE_WAITQUEUE(wait, current);
+	int rc;
+
+	add_wait_queue_exclusive(sk_sleep(sk), &wait);
+	for (;;) {
+		__set_current_state(TASK_INTERRUPTIBLE);
+		rc = -ERESTARTSYS;
+		if (signal_pending(current))
+			break;
+		rc = sock_error(sk);
+		if (rc) {
+			sk->sk_socket->state = SS_UNCONNECTED;
+			break;
+		}
+		rc = -ENOTCONN;
+		if (sk->sk_state == TCP_CLOSE) {
+			sk->sk_socket->state = SS_UNCONNECTED;
+			break;
+		}
+		rc = 0;
+		if (sk->sk_state != TCP_ESTABLISHED) {
+			release_sock(sk);
+			schedule();
+			lock_sock(sk);
+		} else
+			break;
+	}
+	__set_current_state(TASK_RUNNING);
+	remove_wait_queue(sk_sleep(sk), &wait);
+	return rc;
+}
+
+static int x25_connect(struct socket *sock, struct sockaddr *uaddr,
+		       int addr_len, int flags)
+{
+	struct sock *sk = sock->sk;
+	struct x25_sock *x25 = x25_sk(sk);
+	struct sockaddr_x25 *addr = (struct sockaddr_x25 *)uaddr;
+	struct x25_route *rt;
+	int rc = 0;
+
+	lock_sock(sk);
+	if (sk->sk_state == TCP_ESTABLISHED && sock->state == SS_CONNECTING) {
+		sock->state = SS_CONNECTED;
+		goto out; /* Connect completed during a ERESTARTSYS event */
+	}
+
+	rc = -ECONNREFUSED;
+	if (sk->sk_state == TCP_CLOSE && sock->state == SS_CONNECTING) {
+		sock->state = SS_UNCONNECTED;
+		goto out;
+	}
+
+	rc = -EISCONN;	/* No reconnect on a seqpacket socket */
+	if (sk->sk_state == TCP_ESTABLISHED)
+		goto out;
+
+	rc = -EALREADY;	/* Do nothing if call is already in progress */
+	if (sk->sk_state == TCP_SYN_SENT)
+		goto out;
+
+	sk->sk_state   = TCP_CLOSE;
+	sock->state = SS_UNCONNECTED;
+
+	rc = -EINVAL;
+	if (addr_len != sizeof(struct sockaddr_x25) ||
+	    addr->sx25_family != AF_X25 ||
+	    strnlen(addr->sx25_addr.x25_addr, X25_ADDR_LEN) == X25_ADDR_LEN)
+		goto out;
+
+	rc = -ENETUNREACH;
+	rt = x25_get_route(&addr->sx25_addr);
+	if (!rt)
+		goto out;
+
+	x25->neighbour = x25_get_neigh(rt->dev);
+	if (!x25->neighbour)
+		goto out_put_route;
+
+	x25_limit_facilities(&x25->facilities, x25->neighbour);
+
+	x25->lci = x25_new_lci(x25->neighbour);
+	if (!x25->lci)
+		goto out_put_neigh;
+
+	rc = -EINVAL;
+	if (sock_flag(sk, SOCK_ZAPPED)) /* Must bind first - autobinding does not work */
+		goto out_put_neigh;
+
+	if (!strcmp(x25->source_addr.x25_addr, null_x25_address.x25_addr))
+		memset(&x25->source_addr, '\0', X25_ADDR_LEN);
+
+	x25->dest_addr = addr->sx25_addr;
+
+	/* Move to connecting socket, start sending Connect Requests */
+	sock->state   = SS_CONNECTING;
+	sk->sk_state  = TCP_SYN_SENT;
+
+	x25->state = X25_STATE_1;
+
+	x25_write_internal(sk, X25_CALL_REQUEST);
+
+	x25_start_heartbeat(sk);
+	x25_start_t21timer(sk);
+
+	/* Now the loop */
+	rc = -EINPROGRESS;
+	if (sk->sk_state != TCP_ESTABLISHED && (flags & O_NONBLOCK))
+		goto out;
+
+	rc = x25_wait_for_connection_establishment(sk);
+	if (rc)
+		goto out_put_neigh;
+
+	sock->state = SS_CONNECTED;
+	rc = 0;
+out_put_neigh:
+	if (rc && x25->neighbour) {
+		read_lock_bh(&x25_list_lock);
+		x25_neigh_put(x25->neighbour);
+		x25->neighbour = NULL;
+		read_unlock_bh(&x25_list_lock);
+		x25->state = X25_STATE_0;
+	}
+out_put_route:
+	x25_route_put(rt);
+out:
+	release_sock(sk);
+	return rc;
+}
+
+static int x25_wait_for_data(struct sock *sk, long timeout)
+{
+	DECLARE_WAITQUEUE(wait, current);
+	int rc = 0;
+
+	add_wait_queue_exclusive(sk_sleep(sk), &wait);
+	for (;;) {
+		__set_current_state(TASK_INTERRUPTIBLE);
+		if (sk->sk_shutdown & RCV_SHUTDOWN)
+			break;
+		rc = -ERESTARTSYS;
+		if (signal_pending(current))
+			break;
+		rc = -EAGAIN;
+		if (!timeout)
+			break;
+		rc = 0;
+		if (skb_queue_empty(&sk->sk_receive_queue)) {
+			release_sock(sk);
+			timeout = schedule_timeout(timeout);
+			lock_sock(sk);
+		} else
+			break;
+	}
+	__set_current_state(TASK_RUNNING);
+	remove_wait_queue(sk_sleep(sk), &wait);
+	return rc;
+}
+
+static int x25_accept(struct socket *sock, struct socket *newsock, int flags,
+		      bool kern)
+{
+	struct sock *sk = sock->sk;
+	struct sock *newsk;
+	struct sk_buff *skb;
+	int rc = -EINVAL;
+
+	if (!sk)
+		goto out;
+
+	rc = -EOPNOTSUPP;
+	if (sk->sk_type != SOCK_SEQPACKET)
+		goto out;
+
+	lock_sock(sk);
+	rc = -EINVAL;
+	if (sk->sk_state != TCP_LISTEN)
+		goto out2;
+
+	rc = x25_wait_for_data(sk, sk->sk_rcvtimeo);
+	if (rc)
+		goto out2;
+	skb = skb_dequeue(&sk->sk_receive_queue);
+	rc = -EINVAL;
+	if (!skb->sk)
+		goto out2;
+	newsk		 = skb->sk;
+	sock_graft(newsk, newsock);
+
+	/* Now attach up the new socket */
+	skb->sk = NULL;
+	kfree_skb(skb);
+	sk_acceptq_removed(sk);
+	newsock->state = SS_CONNECTED;
+	rc = 0;
+out2:
+	release_sock(sk);
+out:
+	return rc;
+}
+
+static int x25_getname(struct socket *sock, struct sockaddr *uaddr,
+		       int peer)
+{
+	struct sockaddr_x25 *sx25 = (struct sockaddr_x25 *)uaddr;
+	struct sock *sk = sock->sk;
+	struct x25_sock *x25 = x25_sk(sk);
+	int rc = 0;
+
+	if (peer) {
+		if (sk->sk_state != TCP_ESTABLISHED) {
+			rc = -ENOTCONN;
+			goto out;
+		}
+		sx25->sx25_addr = x25->dest_addr;
+	} else
+		sx25->sx25_addr = x25->source_addr;
+
+	sx25->sx25_family = AF_X25;
+	rc = sizeof(*sx25);
+
+out:
+	return rc;
+}
+
+int x25_rx_call_request(struct sk_buff *skb, struct x25_neigh *nb,
+			unsigned int lci)
+{
+	struct sock *sk;
+	struct sock *make;
+	struct x25_sock *makex25;
+	struct x25_address source_addr, dest_addr;
+	struct x25_facilities facilities;
+	struct x25_dte_facilities dte_facilities;
+	int len, addr_len, rc;
+
+	/*
+	 *	Remove the LCI and frame type.
+	 */
+	skb_pull(skb, X25_STD_MIN_LEN);
+
+	/*
+	 *	Extract the X.25 addresses and convert them to ASCII strings,
+	 *	and remove them.
+	 *
+	 *	Address block is mandatory in call request packets
+	 */
+	addr_len = x25_parse_address_block(skb, &source_addr, &dest_addr);
+	if (addr_len <= 0)
+		goto out_clear_request;
+	skb_pull(skb, addr_len);
+
+	/*
+	 *	Get the length of the facilities, skip past them for the moment
+	 *	get the call user data because this is needed to determine
+	 *	the correct listener
+	 *
+	 *	Facilities length is mandatory in call request packets
+	 */
+	if (!pskb_may_pull(skb, 1))
+		goto out_clear_request;
+	len = skb->data[0] + 1;
+	if (!pskb_may_pull(skb, len))
+		goto out_clear_request;
+	skb_pull(skb,len);
+
+	/*
+	 *	Ensure that the amount of call user data is valid.
+	 */
+	if (skb->len > X25_MAX_CUD_LEN)
+		goto out_clear_request;
+
+	/*
+	 *	Get all the call user data so it can be used in
+	 *	x25_find_listener and skb_copy_from_linear_data up ahead.
+	 */
+	if (!pskb_may_pull(skb, skb->len))
+		goto out_clear_request;
+
+	/*
+	 *	Find a listener for the particular address/cud pair.
+	 */
+	sk = x25_find_listener(&source_addr,skb);
+	skb_push(skb,len);
+
+	if (sk != NULL && sk_acceptq_is_full(sk)) {
+		goto out_sock_put;
+	}
+
+	/*
+	 *	We dont have any listeners for this incoming call.
+	 *	Try forwarding it.
+	 */
+	if (sk == NULL) {
+		skb_push(skb, addr_len + X25_STD_MIN_LEN);
+		if (sysctl_x25_forward &&
+				x25_forward_call(&dest_addr, nb, skb, lci) > 0)
+		{
+			/* Call was forwarded, dont process it any more */
+			kfree_skb(skb);
+			rc = 1;
+			goto out;
+		} else {
+			/* No listeners, can't forward, clear the call */
+			goto out_clear_request;
+		}
+	}
+
+	/*
+	 *	Try to reach a compromise on the requested facilities.
+	 */
+	len = x25_negotiate_facilities(skb, sk, &facilities, &dte_facilities);
+	if (len == -1)
+		goto out_sock_put;
+
+	/*
+	 * current neighbour/link might impose additional limits
+	 * on certain facilities
+	 */
+
+	x25_limit_facilities(&facilities, nb);
+
+	/*
+	 *	Try to create a new socket.
+	 */
+	make = x25_make_new(sk);
+	if (!make)
+		goto out_sock_put;
+
+	/*
+	 *	Remove the facilities
+	 */
+	skb_pull(skb, len);
+
+	skb->sk     = make;
+	make->sk_state = TCP_ESTABLISHED;
+
+	makex25 = x25_sk(make);
+	makex25->lci           = lci;
+	makex25->dest_addr     = dest_addr;
+	makex25->source_addr   = source_addr;
+	x25_neigh_hold(nb);
+	makex25->neighbour     = nb;
+	makex25->facilities    = facilities;
+	makex25->dte_facilities= dte_facilities;
+	makex25->vc_facil_mask = x25_sk(sk)->vc_facil_mask;
+	/* ensure no reverse facil on accept */
+	makex25->vc_facil_mask &= ~X25_MASK_REVERSE;
+	/* ensure no calling address extension on accept */
+	makex25->vc_facil_mask &= ~X25_MASK_CALLING_AE;
+	makex25->cudmatchlength = x25_sk(sk)->cudmatchlength;
+
+	/* Normally all calls are accepted immediately */
+	if (test_bit(X25_ACCPT_APPRV_FLAG, &makex25->flags)) {
+		x25_write_internal(make, X25_CALL_ACCEPTED);
+		makex25->state = X25_STATE_3;
+	} else {
+		makex25->state = X25_STATE_5;
+	}
+
+	/*
+	 *	Incoming Call User Data.
+	 */
+	skb_copy_from_linear_data(skb, makex25->calluserdata.cuddata, skb->len);
+	makex25->calluserdata.cudlength = skb->len;
+
+	sk_acceptq_added(sk);
+
+	x25_insert_socket(make);
+
+	skb_queue_head(&sk->sk_receive_queue, skb);
+
+	x25_start_heartbeat(make);
+
+	if (!sock_flag(sk, SOCK_DEAD))
+		sk->sk_data_ready(sk);
+	rc = 1;
+	sock_put(sk);
+out:
+	return rc;
+out_sock_put:
+	sock_put(sk);
+out_clear_request:
+	rc = 0;
+	x25_transmit_clear_request(nb, lci, 0x01);
+	goto out;
+}
+
+static int x25_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
+{
+	struct sock *sk = sock->sk;
+	struct x25_sock *x25 = x25_sk(sk);
+	DECLARE_SOCKADDR(struct sockaddr_x25 *, usx25, msg->msg_name);
+	struct sockaddr_x25 sx25;
+	struct sk_buff *skb;
+	unsigned char *asmptr;
+	int noblock = msg->msg_flags & MSG_DONTWAIT;
+	size_t size;
+	int qbit = 0, rc = -EINVAL;
+
+	lock_sock(sk);
+	if (msg->msg_flags & ~(MSG_DONTWAIT|MSG_OOB|MSG_EOR|MSG_CMSG_COMPAT))
+		goto out;
+
+	/* we currently don't support segmented records at the user interface */
+	if (!(msg->msg_flags & (MSG_EOR|MSG_OOB)))
+		goto out;
+
+	rc = -EADDRNOTAVAIL;
+	if (sock_flag(sk, SOCK_ZAPPED))
+		goto out;
+
+	rc = -EPIPE;
+	if (sk->sk_shutdown & SEND_SHUTDOWN) {
+		send_sig(SIGPIPE, current, 0);
+		goto out;
+	}
+
+	rc = -ENETUNREACH;
+	if (!x25->neighbour)
+		goto out;
+
+	if (usx25) {
+		rc = -EINVAL;
+		if (msg->msg_namelen < sizeof(sx25))
+			goto out;
+		memcpy(&sx25, usx25, sizeof(sx25));
+		rc = -EISCONN;
+		if (strcmp(x25->dest_addr.x25_addr, sx25.sx25_addr.x25_addr))
+			goto out;
+		rc = -EINVAL;
+		if (sx25.sx25_family != AF_X25)
+			goto out;
+	} else {
+		/*
+		 *	FIXME 1003.1g - if the socket is like this because
+		 *	it has become closed (not started closed) we ought
+		 *	to SIGPIPE, EPIPE;
+		 */
+		rc = -ENOTCONN;
+		if (sk->sk_state != TCP_ESTABLISHED)
+			goto out;
+
+		sx25.sx25_family = AF_X25;
+		sx25.sx25_addr   = x25->dest_addr;
+	}
+
+	/* Sanity check the packet size */
+	if (len > 65535) {
+		rc = -EMSGSIZE;
+		goto out;
+	}
+
+	SOCK_DEBUG(sk, "x25_sendmsg: sendto: Addresses built.\n");
+
+	/* Build a packet */
+	SOCK_DEBUG(sk, "x25_sendmsg: sendto: building packet.\n");
+
+	if ((msg->msg_flags & MSG_OOB) && len > 32)
+		len = 32;
+
+	size = len + X25_MAX_L2_LEN + X25_EXT_MIN_LEN;
+
+	release_sock(sk);
+	skb = sock_alloc_send_skb(sk, size, noblock, &rc);
+	lock_sock(sk);
+	if (!skb)
+		goto out;
+	X25_SKB_CB(skb)->flags = msg->msg_flags;
+
+	skb_reserve(skb, X25_MAX_L2_LEN + X25_EXT_MIN_LEN);
+
+	/*
+	 *	Put the data on the end
+	 */
+	SOCK_DEBUG(sk, "x25_sendmsg: Copying user data\n");
+
+	skb_reset_transport_header(skb);
+	skb_put(skb, len);
+
+	rc = memcpy_from_msg(skb_transport_header(skb), msg, len);
+	if (rc)
+		goto out_kfree_skb;
+
+	/*
+	 *	If the Q BIT Include socket option is in force, the first
+	 *	byte of the user data is the logical value of the Q Bit.
+	 */
+	if (test_bit(X25_Q_BIT_FLAG, &x25->flags)) {
+		if (!pskb_may_pull(skb, 1))
+			goto out_kfree_skb;
+
+		qbit = skb->data[0];
+		skb_pull(skb, 1);
+	}
+
+	/*
+	 *	Push down the X.25 header
+	 */
+	SOCK_DEBUG(sk, "x25_sendmsg: Building X.25 Header.\n");
+
+	if (msg->msg_flags & MSG_OOB) {
+		if (x25->neighbour->extended) {
+			asmptr    = skb_push(skb, X25_STD_MIN_LEN);
+			*asmptr++ = ((x25->lci >> 8) & 0x0F) | X25_GFI_EXTSEQ;
+			*asmptr++ = (x25->lci >> 0) & 0xFF;
+			*asmptr++ = X25_INTERRUPT;
+		} else {
+			asmptr    = skb_push(skb, X25_STD_MIN_LEN);
+			*asmptr++ = ((x25->lci >> 8) & 0x0F) | X25_GFI_STDSEQ;
+			*asmptr++ = (x25->lci >> 0) & 0xFF;
+			*asmptr++ = X25_INTERRUPT;
+		}
+	} else {
+		if (x25->neighbour->extended) {
+			/* Build an Extended X.25 header */
+			asmptr    = skb_push(skb, X25_EXT_MIN_LEN);
+			*asmptr++ = ((x25->lci >> 8) & 0x0F) | X25_GFI_EXTSEQ;
+			*asmptr++ = (x25->lci >> 0) & 0xFF;
+			*asmptr++ = X25_DATA;
+			*asmptr++ = X25_DATA;
+		} else {
+			/* Build an Standard X.25 header */
+			asmptr    = skb_push(skb, X25_STD_MIN_LEN);
+			*asmptr++ = ((x25->lci >> 8) & 0x0F) | X25_GFI_STDSEQ;
+			*asmptr++ = (x25->lci >> 0) & 0xFF;
+			*asmptr++ = X25_DATA;
+		}
+
+		if (qbit)
+			skb->data[0] |= X25_Q_BIT;
+	}
+
+	SOCK_DEBUG(sk, "x25_sendmsg: Built header.\n");
+	SOCK_DEBUG(sk, "x25_sendmsg: Transmitting buffer\n");
+
+	rc = -ENOTCONN;
+	if (sk->sk_state != TCP_ESTABLISHED)
+		goto out_kfree_skb;
+
+	if (msg->msg_flags & MSG_OOB)
+		skb_queue_tail(&x25->interrupt_out_queue, skb);
+	else {
+		rc = x25_output(sk, skb);
+		len = rc;
+		if (rc < 0)
+			kfree_skb(skb);
+		else if (test_bit(X25_Q_BIT_FLAG, &x25->flags))
+			len++;
+	}
+
+	x25_kick(sk);
+	rc = len;
+out:
+	release_sock(sk);
+	return rc;
+out_kfree_skb:
+	kfree_skb(skb);
+	goto out;
+}
+
+
+static int x25_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
+		       int flags)
+{
+	struct sock *sk = sock->sk;
+	struct x25_sock *x25 = x25_sk(sk);
+	DECLARE_SOCKADDR(struct sockaddr_x25 *, sx25, msg->msg_name);
+	size_t copied;
+	int qbit, header_len;
+	struct sk_buff *skb;
+	unsigned char *asmptr;
+	int rc = -ENOTCONN;
+
+	lock_sock(sk);
+
+	if (x25->neighbour == NULL)
+		goto out;
+
+	header_len = x25->neighbour->extended ?
+		X25_EXT_MIN_LEN : X25_STD_MIN_LEN;
+
+	/*
+	 * This works for seqpacket too. The receiver has ordered the queue for
+	 * us! We do one quick check first though
+	 */
+	if (sk->sk_state != TCP_ESTABLISHED)
+		goto out;
+
+	if (flags & MSG_OOB) {
+		rc = -EINVAL;
+		if (sock_flag(sk, SOCK_URGINLINE) ||
+		    !skb_peek(&x25->interrupt_in_queue))
+			goto out;
+
+		skb = skb_dequeue(&x25->interrupt_in_queue);
+
+		if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+			goto out_free_dgram;
+
+		skb_pull(skb, X25_STD_MIN_LEN);
+
+		/*
+		 *	No Q bit information on Interrupt data.
+		 */
+		if (test_bit(X25_Q_BIT_FLAG, &x25->flags)) {
+			asmptr  = skb_push(skb, 1);
+			*asmptr = 0x00;
+		}
+
+		msg->msg_flags |= MSG_OOB;
+	} else {
+		/* Now we can treat all alike */
+		release_sock(sk);
+		skb = skb_recv_datagram(sk, flags, &rc);
+		lock_sock(sk);
+		if (!skb)
+			goto out;
+
+		if (!pskb_may_pull(skb, header_len))
+			goto out_free_dgram;
+
+		qbit = (skb->data[0] & X25_Q_BIT) == X25_Q_BIT;
+
+		skb_pull(skb, header_len);
+
+		if (test_bit(X25_Q_BIT_FLAG, &x25->flags)) {
+			asmptr  = skb_push(skb, 1);
+			*asmptr = qbit;
+		}
+	}
+
+	skb_reset_transport_header(skb);
+	copied = skb->len;
+
+	if (copied > size) {
+		copied = size;
+		msg->msg_flags |= MSG_TRUNC;
+	}
+
+	/* Currently, each datagram always contains a complete record */
+	msg->msg_flags |= MSG_EOR;
+
+	rc = skb_copy_datagram_msg(skb, 0, msg, copied);
+	if (rc)
+		goto out_free_dgram;
+
+	if (sx25) {
+		sx25->sx25_family = AF_X25;
+		sx25->sx25_addr   = x25->dest_addr;
+		msg->msg_namelen = sizeof(*sx25);
+	}
+
+	x25_check_rbuf(sk);
+	rc = copied;
+out_free_dgram:
+	skb_free_datagram(sk, skb);
+out:
+	release_sock(sk);
+	return rc;
+}
+
+
+static int x25_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
+{
+	struct sock *sk = sock->sk;
+	struct x25_sock *x25 = x25_sk(sk);
+	void __user *argp = (void __user *)arg;
+	int rc;
+
+	switch (cmd) {
+	case TIOCOUTQ: {
+		int amount;
+
+		amount = sk->sk_sndbuf - sk_wmem_alloc_get(sk);
+		if (amount < 0)
+			amount = 0;
+		rc = put_user(amount, (unsigned int __user *)argp);
+		break;
+	}
+
+	case TIOCINQ: {
+		struct sk_buff *skb;
+		int amount = 0;
+		/*
+		 * These two are safe on a single CPU system as
+		 * only user tasks fiddle here
+		 */
+		lock_sock(sk);
+		if ((skb = skb_peek(&sk->sk_receive_queue)) != NULL)
+			amount = skb->len;
+		release_sock(sk);
+		rc = put_user(amount, (unsigned int __user *)argp);
+		break;
+	}
+
+	case SIOCGIFADDR:
+	case SIOCSIFADDR:
+	case SIOCGIFDSTADDR:
+	case SIOCSIFDSTADDR:
+	case SIOCGIFBRDADDR:
+	case SIOCSIFBRDADDR:
+	case SIOCGIFNETMASK:
+	case SIOCSIFNETMASK:
+	case SIOCGIFMETRIC:
+	case SIOCSIFMETRIC:
+		rc = -EINVAL;
+		break;
+	case SIOCADDRT:
+	case SIOCDELRT:
+		rc = -EPERM;
+		if (!capable(CAP_NET_ADMIN))
+			break;
+		rc = x25_route_ioctl(cmd, argp);
+		break;
+	case SIOCX25GSUBSCRIP:
+		rc = x25_subscr_ioctl(cmd, argp);
+		break;
+	case SIOCX25SSUBSCRIP:
+		rc = -EPERM;
+		if (!capable(CAP_NET_ADMIN))
+			break;
+		rc = x25_subscr_ioctl(cmd, argp);
+		break;
+	case SIOCX25GFACILITIES: {
+		lock_sock(sk);
+		rc = copy_to_user(argp, &x25->facilities,
+				  sizeof(x25->facilities))
+			? -EFAULT : 0;
+		release_sock(sk);
+		break;
+	}
+
+	case SIOCX25SFACILITIES: {
+		struct x25_facilities facilities;
+		rc = -EFAULT;
+		if (copy_from_user(&facilities, argp, sizeof(facilities)))
+			break;
+		rc = -EINVAL;
+		lock_sock(sk);
+		if (sk->sk_state != TCP_LISTEN &&
+		    sk->sk_state != TCP_CLOSE)
+			goto out_fac_release;
+		if (facilities.pacsize_in < X25_PS16 ||
+		    facilities.pacsize_in > X25_PS4096)
+			goto out_fac_release;
+		if (facilities.pacsize_out < X25_PS16 ||
+		    facilities.pacsize_out > X25_PS4096)
+			goto out_fac_release;
+		if (facilities.winsize_in < 1 ||
+		    facilities.winsize_in > 127)
+			goto out_fac_release;
+		if (facilities.throughput) {
+			int out = facilities.throughput & 0xf0;
+			int in  = facilities.throughput & 0x0f;
+			if (!out)
+				facilities.throughput |=
+					X25_DEFAULT_THROUGHPUT << 4;
+			else if (out < 0x30 || out > 0xD0)
+				goto out_fac_release;
+			if (!in)
+				facilities.throughput |=
+					X25_DEFAULT_THROUGHPUT;
+			else if (in < 0x03 || in > 0x0D)
+				goto out_fac_release;
+		}
+		if (facilities.reverse &&
+		    (facilities.reverse & 0x81) != 0x81)
+			goto out_fac_release;
+		x25->facilities = facilities;
+		rc = 0;
+out_fac_release:
+		release_sock(sk);
+		break;
+	}
+
+	case SIOCX25GDTEFACILITIES: {
+		lock_sock(sk);
+		rc = copy_to_user(argp, &x25->dte_facilities,
+				  sizeof(x25->dte_facilities));
+		release_sock(sk);
+		if (rc)
+			rc = -EFAULT;
+		break;
+	}
+
+	case SIOCX25SDTEFACILITIES: {
+		struct x25_dte_facilities dtefacs;
+		rc = -EFAULT;
+		if (copy_from_user(&dtefacs, argp, sizeof(dtefacs)))
+			break;
+		rc = -EINVAL;
+		lock_sock(sk);
+		if (sk->sk_state != TCP_LISTEN &&
+		    sk->sk_state != TCP_CLOSE)
+			goto out_dtefac_release;
+		if (dtefacs.calling_len > X25_MAX_AE_LEN)
+			goto out_dtefac_release;
+		if (dtefacs.called_len > X25_MAX_AE_LEN)
+			goto out_dtefac_release;
+		x25->dte_facilities = dtefacs;
+		rc = 0;
+out_dtefac_release:
+		release_sock(sk);
+		break;
+	}
+
+	case SIOCX25GCALLUSERDATA: {
+		lock_sock(sk);
+		rc = copy_to_user(argp, &x25->calluserdata,
+				  sizeof(x25->calluserdata))
+			? -EFAULT : 0;
+		release_sock(sk);
+		break;
+	}
+
+	case SIOCX25SCALLUSERDATA: {
+		struct x25_calluserdata calluserdata;
+
+		rc = -EFAULT;
+		if (copy_from_user(&calluserdata, argp, sizeof(calluserdata)))
+			break;
+		rc = -EINVAL;
+		if (calluserdata.cudlength > X25_MAX_CUD_LEN)
+			break;
+		lock_sock(sk);
+		x25->calluserdata = calluserdata;
+		release_sock(sk);
+		rc = 0;
+		break;
+	}
+
+	case SIOCX25GCAUSEDIAG: {
+		lock_sock(sk);
+		rc = copy_to_user(argp, &x25->causediag, sizeof(x25->causediag))
+			? -EFAULT : 0;
+		release_sock(sk);
+		break;
+	}
+
+	case SIOCX25SCAUSEDIAG: {
+		struct x25_causediag causediag;
+		rc = -EFAULT;
+		if (copy_from_user(&causediag, argp, sizeof(causediag)))
+			break;
+		lock_sock(sk);
+		x25->causediag = causediag;
+		release_sock(sk);
+		rc = 0;
+		break;
+
+	}
+
+	case SIOCX25SCUDMATCHLEN: {
+		struct x25_subaddr sub_addr;
+		rc = -EINVAL;
+		lock_sock(sk);
+		if(sk->sk_state != TCP_CLOSE)
+			goto out_cud_release;
+		rc = -EFAULT;
+		if (copy_from_user(&sub_addr, argp,
+				   sizeof(sub_addr)))
+			goto out_cud_release;
+		rc = -EINVAL;
+		if (sub_addr.cudmatchlength > X25_MAX_CUD_LEN)
+			goto out_cud_release;
+		x25->cudmatchlength = sub_addr.cudmatchlength;
+		rc = 0;
+out_cud_release:
+		release_sock(sk);
+		break;
+	}
+
+	case SIOCX25CALLACCPTAPPRV: {
+		rc = -EINVAL;
+		lock_sock(sk);
+		if (sk->sk_state == TCP_CLOSE) {
+			clear_bit(X25_ACCPT_APPRV_FLAG, &x25->flags);
+			rc = 0;
+		}
+		release_sock(sk);
+		break;
+	}
+
+	case SIOCX25SENDCALLACCPT:  {
+		rc = -EINVAL;
+		lock_sock(sk);
+		if (sk->sk_state != TCP_ESTABLISHED)
+			goto out_sendcallaccpt_release;
+		/* must call accptapprv above */
+		if (test_bit(X25_ACCPT_APPRV_FLAG, &x25->flags))
+			goto out_sendcallaccpt_release;
+		x25_write_internal(sk, X25_CALL_ACCEPTED);
+		x25->state = X25_STATE_3;
+		rc = 0;
+out_sendcallaccpt_release:
+		release_sock(sk);
+		break;
+	}
+
+	default:
+		rc = -ENOIOCTLCMD;
+		break;
+	}
+
+	return rc;
+}
+
+static const struct net_proto_family x25_family_ops = {
+	.family =	AF_X25,
+	.create =	x25_create,
+	.owner	=	THIS_MODULE,
+};
+
+#ifdef CONFIG_COMPAT
+static int compat_x25_subscr_ioctl(unsigned int cmd,
+		struct compat_x25_subscrip_struct __user *x25_subscr32)
+{
+	struct compat_x25_subscrip_struct x25_subscr;
+	struct x25_neigh *nb;
+	struct net_device *dev;
+	int rc = -EINVAL;
+
+	rc = -EFAULT;
+	if (copy_from_user(&x25_subscr, x25_subscr32, sizeof(*x25_subscr32)))
+		goto out;
+
+	rc = -EINVAL;
+	dev = x25_dev_get(x25_subscr.device);
+	if (dev == NULL)
+		goto out;
+
+	nb = x25_get_neigh(dev);
+	if (nb == NULL)
+		goto out_dev_put;
+
+	dev_put(dev);
+
+	if (cmd == SIOCX25GSUBSCRIP) {
+		read_lock_bh(&x25_neigh_list_lock);
+		x25_subscr.extended = nb->extended;
+		x25_subscr.global_facil_mask = nb->global_facil_mask;
+		read_unlock_bh(&x25_neigh_list_lock);
+		rc = copy_to_user(x25_subscr32, &x25_subscr,
+				sizeof(*x25_subscr32)) ? -EFAULT : 0;
+	} else {
+		rc = -EINVAL;
+		if (x25_subscr.extended == 0 || x25_subscr.extended == 1) {
+			rc = 0;
+			write_lock_bh(&x25_neigh_list_lock);
+			nb->extended = x25_subscr.extended;
+			nb->global_facil_mask = x25_subscr.global_facil_mask;
+			write_unlock_bh(&x25_neigh_list_lock);
+		}
+	}
+	x25_neigh_put(nb);
+out:
+	return rc;
+out_dev_put:
+	dev_put(dev);
+	goto out;
+}
+
+static int compat_x25_ioctl(struct socket *sock, unsigned int cmd,
+				unsigned long arg)
+{
+	void __user *argp = compat_ptr(arg);
+	int rc = -ENOIOCTLCMD;
+
+	switch(cmd) {
+	case TIOCOUTQ:
+	case TIOCINQ:
+		rc = x25_ioctl(sock, cmd, (unsigned long)argp);
+		break;
+	case SIOCGIFADDR:
+	case SIOCSIFADDR:
+	case SIOCGIFDSTADDR:
+	case SIOCSIFDSTADDR:
+	case SIOCGIFBRDADDR:
+	case SIOCSIFBRDADDR:
+	case SIOCGIFNETMASK:
+	case SIOCSIFNETMASK:
+	case SIOCGIFMETRIC:
+	case SIOCSIFMETRIC:
+		rc = -EINVAL;
+		break;
+	case SIOCADDRT:
+	case SIOCDELRT:
+		rc = -EPERM;
+		if (!capable(CAP_NET_ADMIN))
+			break;
+		rc = x25_route_ioctl(cmd, argp);
+		break;
+	case SIOCX25GSUBSCRIP:
+		rc = compat_x25_subscr_ioctl(cmd, argp);
+		break;
+	case SIOCX25SSUBSCRIP:
+		rc = -EPERM;
+		if (!capable(CAP_NET_ADMIN))
+			break;
+		rc = compat_x25_subscr_ioctl(cmd, argp);
+		break;
+	case SIOCX25GFACILITIES:
+	case SIOCX25SFACILITIES:
+	case SIOCX25GDTEFACILITIES:
+	case SIOCX25SDTEFACILITIES:
+	case SIOCX25GCALLUSERDATA:
+	case SIOCX25SCALLUSERDATA:
+	case SIOCX25GCAUSEDIAG:
+	case SIOCX25SCAUSEDIAG:
+	case SIOCX25SCUDMATCHLEN:
+	case SIOCX25CALLACCPTAPPRV:
+	case SIOCX25SENDCALLACCPT:
+		rc = x25_ioctl(sock, cmd, (unsigned long)argp);
+		break;
+	default:
+		rc = -ENOIOCTLCMD;
+		break;
+	}
+	return rc;
+}
+#endif
+
+static const struct proto_ops x25_proto_ops = {
+	.family =	AF_X25,
+	.owner =	THIS_MODULE,
+	.release =	x25_release,
+	.bind =		x25_bind,
+	.connect =	x25_connect,
+	.socketpair =	sock_no_socketpair,
+	.accept =	x25_accept,
+	.getname =	x25_getname,
+	.poll =		datagram_poll,
+	.ioctl =	x25_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = compat_x25_ioctl,
+#endif
+	.gettstamp =	sock_gettstamp,
+	.listen =	x25_listen,
+	.shutdown =	sock_no_shutdown,
+	.setsockopt =	x25_setsockopt,
+	.getsockopt =	x25_getsockopt,
+	.sendmsg =	x25_sendmsg,
+	.recvmsg =	x25_recvmsg,
+	.mmap =		sock_no_mmap,
+	.sendpage =	sock_no_sendpage,
+};
+
+static struct packet_type x25_packet_type __read_mostly = {
+	.type =	cpu_to_be16(ETH_P_X25),
+	.func =	x25_lapb_receive_frame,
+};
+
+static struct notifier_block x25_dev_notifier = {
+	.notifier_call = x25_device_event,
+};
+
+void x25_kill_by_neigh(struct x25_neigh *nb)
+{
+	struct sock *s;
+
+	write_lock_bh(&x25_list_lock);
+
+	sk_for_each(s, &x25_list) {
+		if (x25_sk(s)->neighbour == nb) {
+			write_unlock_bh(&x25_list_lock);
+			lock_sock(s);
+			x25_disconnect(s, ENETUNREACH, 0, 0);
+			release_sock(s);
+			write_lock_bh(&x25_list_lock);
+		}
+	}
+	write_unlock_bh(&x25_list_lock);
+
+	/* Remove any related forwards */
+	x25_clear_forward_by_dev(nb->dev);
+}
+
+static int __init x25_init(void)
+{
+	int rc;
+
+	rc = proto_register(&x25_proto, 0);
+	if (rc)
+		goto out;
+
+	rc = sock_register(&x25_family_ops);
+	if (rc)
+		goto out_proto;
+
+	dev_add_pack(&x25_packet_type);
+
+	rc = register_netdevice_notifier(&x25_dev_notifier);
+	if (rc)
+		goto out_sock;
+
+	rc = x25_register_sysctl();
+	if (rc)
+		goto out_dev;
+
+	rc = x25_proc_init();
+	if (rc)
+		goto out_sysctl;
+
+	pr_info("Linux Version 0.2\n");
+
+out:
+	return rc;
+out_sysctl:
+	x25_unregister_sysctl();
+out_dev:
+	unregister_netdevice_notifier(&x25_dev_notifier);
+out_sock:
+	dev_remove_pack(&x25_packet_type);
+	sock_unregister(AF_X25);
+out_proto:
+	proto_unregister(&x25_proto);
+	goto out;
+}
+module_init(x25_init);
+
+static void __exit x25_exit(void)
+{
+	x25_proc_exit();
+	x25_link_free();
+	x25_route_free();
+
+	x25_unregister_sysctl();
+
+	unregister_netdevice_notifier(&x25_dev_notifier);
+
+	dev_remove_pack(&x25_packet_type);
+
+	sock_unregister(AF_X25);
+	proto_unregister(&x25_proto);
+}
+module_exit(x25_exit);
+
+MODULE_AUTHOR("Jonathan Naylor <g4klx@g4klx.demon.co.uk>");
+MODULE_DESCRIPTION("The X.25 Packet Layer network layer protocol");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_NETPROTO(PF_X25);
diff --git a/net/x25/sysctl_net_x25.c b/net/x25/sysctl_net_x25.c
new file mode 100644
index 000000000..e9802afa4
--- /dev/null
+++ b/net/x25/sysctl_net_x25.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+/* -*- linux-c -*-
+ * sysctl_net_x25.c: sysctl interface to net X.25 subsystem.
+ *
+ * Begun April 1, 1996, Mike Shaver.
+ * Added /proc/sys/net/x25 directory entry (empty =) ). [MS]
+ */
+
+#include <linux/sysctl.h>
+#include <linux/skbuff.h>
+#include <linux/socket.h>
+#include <linux/netdevice.h>
+#include <linux/init.h>
+#include <net/x25.h>
+
+static int min_timer[] = {   1 * HZ };
+static int max_timer[] = { 300 * HZ };
+
+static struct ctl_table_header *x25_table_header;
+
+static struct ctl_table x25_table[] = {
+	{
+		.procname =	"restart_request_timeout",
+		.data =		&sysctl_x25_restart_request_timeout,
+		.maxlen =	sizeof(int),
+		.mode =		0644,
+		.proc_handler =	proc_dointvec_minmax,
+		.extra1 =	&min_timer,
+		.extra2 =	&max_timer,
+	},
+	{
+		.procname =	"call_request_timeout",
+		.data =		&sysctl_x25_call_request_timeout,
+		.maxlen =	sizeof(int),
+		.mode =		0644,
+		.proc_handler =	proc_dointvec_minmax,
+		.extra1 =	&min_timer,
+		.extra2 =	&max_timer,
+	},
+	{
+		.procname =	"reset_request_timeout",
+		.data =		&sysctl_x25_reset_request_timeout,
+		.maxlen =	sizeof(int),
+		.mode =		0644,
+		.proc_handler =	proc_dointvec_minmax,
+		.extra1 =	&min_timer,
+		.extra2 =	&max_timer,
+	},
+	{
+		.procname =	"clear_request_timeout",
+		.data =		&sysctl_x25_clear_request_timeout,
+		.maxlen =	sizeof(int),
+		.mode =		0644,
+		.proc_handler =	proc_dointvec_minmax,
+		.extra1 =	&min_timer,
+		.extra2 =	&max_timer,
+	},
+	{
+		.procname =	"acknowledgement_hold_back_timeout",
+		.data =		&sysctl_x25_ack_holdback_timeout,
+		.maxlen =	sizeof(int),
+		.mode =		0644,
+		.proc_handler =	proc_dointvec_minmax,
+		.extra1 =	&min_timer,
+		.extra2 =	&max_timer,
+	},
+	{
+		.procname =	"x25_forward",
+		.data = 	&sysctl_x25_forward,
+		.maxlen = 	sizeof(int),
+		.mode = 	0644,
+		.proc_handler = proc_dointvec,
+	},
+	{ },
+};
+
+int __init x25_register_sysctl(void)
+{
+	x25_table_header = register_net_sysctl(&init_net, "net/x25", x25_table);
+	if (!x25_table_header)
+		return -ENOMEM;
+	return 0;
+}
+
+void x25_unregister_sysctl(void)
+{
+	unregister_net_sysctl_table(x25_table_header);
+}
diff --git a/net/x25/x25_dev.c b/net/x25/x25_dev.c
new file mode 100644
index 000000000..748d8630a
--- /dev/null
+++ b/net/x25/x25_dev.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine, randomly fail to work with new
+ *	releases, misbehave and/or generally screw up. It might even work.
+ *
+ *	This code REQUIRES 2.1.15 or higher
+ *
+ *	History
+ *	X.25 001	Jonathan Naylor	Started coding.
+ *      2000-09-04	Henner Eisen	Prevent freeing a dangling skb.
+ */
+
+#define pr_fmt(fmt) "X25: " fmt
+
+#include <linux/kernel.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <net/sock.h>
+#include <linux/if_arp.h>
+#include <net/x25.h>
+#include <net/x25device.h>
+
+static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb)
+{
+	struct sock *sk;
+	unsigned short frametype;
+	unsigned int lci;
+
+	if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+		return 0;
+
+	frametype = skb->data[2];
+	lci = ((skb->data[0] << 8) & 0xF00) + ((skb->data[1] << 0) & 0x0FF);
+
+	/*
+	 *	LCI of zero is always for us, and its always a link control
+	 *	frame.
+	 */
+	if (lci == 0) {
+		x25_link_control(skb, nb, frametype);
+		return 0;
+	}
+
+	/*
+	 *	Find an existing socket.
+	 */
+	if ((sk = x25_find_socket(lci, nb)) != NULL) {
+		int queued = 1;
+
+		skb_reset_transport_header(skb);
+		bh_lock_sock(sk);
+		if (!sock_owned_by_user(sk)) {
+			queued = x25_process_rx_frame(sk, skb);
+		} else {
+			queued = !sk_add_backlog(sk, skb, READ_ONCE(sk->sk_rcvbuf));
+		}
+		bh_unlock_sock(sk);
+		sock_put(sk);
+		return queued;
+	}
+
+	/*
+	 *	Is is a Call Request ? if so process it.
+	 */
+	if (frametype == X25_CALL_REQUEST)
+		return x25_rx_call_request(skb, nb, lci);
+
+	/*
+	 * 	Its not a Call Request, nor is it a control frame.
+	 *	Can we forward it?
+	 */
+
+	if (x25_forward_data(lci, nb, skb)) {
+		if (frametype == X25_CLEAR_CONFIRMATION) {
+			x25_clear_forward_by_lci(lci);
+		}
+		kfree_skb(skb);
+		return 1;
+	}
+
+/*
+	x25_transmit_clear_request(nb, lci, 0x0D);
+*/
+
+	if (frametype != X25_CLEAR_CONFIRMATION)
+		pr_debug("x25_receive_data(): unknown frame type %2x\n",frametype);
+
+	return 0;
+}
+
+int x25_lapb_receive_frame(struct sk_buff *skb, struct net_device *dev,
+			   struct packet_type *ptype, struct net_device *orig_dev)
+{
+	struct sk_buff *nskb;
+	struct x25_neigh *nb;
+
+	if (!net_eq(dev_net(dev), &init_net))
+		goto drop;
+
+	nskb = skb_copy(skb, GFP_ATOMIC);
+	if (!nskb)
+		goto drop;
+	kfree_skb(skb);
+	skb = nskb;
+
+	/*
+	 * Packet received from unrecognised device, throw it away.
+	 */
+	nb = x25_get_neigh(dev);
+	if (!nb) {
+		pr_debug("unknown neighbour - %s\n", dev->name);
+		goto drop;
+	}
+
+	if (!pskb_may_pull(skb, 1)) {
+		x25_neigh_put(nb);
+		goto drop;
+	}
+
+	switch (skb->data[0]) {
+
+	case X25_IFACE_DATA:
+		skb_pull(skb, 1);
+		if (x25_receive_data(skb, nb)) {
+			x25_neigh_put(nb);
+			goto out;
+		}
+		break;
+
+	case X25_IFACE_CONNECT:
+		x25_link_established(nb);
+		break;
+
+	case X25_IFACE_DISCONNECT:
+		x25_link_terminated(nb);
+		break;
+	}
+	x25_neigh_put(nb);
+drop:
+	kfree_skb(skb);
+out:
+	return 0;
+}
+
+void x25_establish_link(struct x25_neigh *nb)
+{
+	struct sk_buff *skb;
+	unsigned char *ptr;
+
+	switch (nb->dev->type) {
+	case ARPHRD_X25:
+		if ((skb = alloc_skb(1, GFP_ATOMIC)) == NULL) {
+			pr_err("x25_dev: out of memory\n");
+			return;
+		}
+		ptr  = skb_put(skb, 1);
+		*ptr = X25_IFACE_CONNECT;
+		break;
+
+	default:
+		return;
+	}
+
+	skb->protocol = htons(ETH_P_X25);
+	skb->dev      = nb->dev;
+
+	dev_queue_xmit(skb);
+}
+
+void x25_terminate_link(struct x25_neigh *nb)
+{
+	struct sk_buff *skb;
+	unsigned char *ptr;
+
+	if (nb->dev->type != ARPHRD_X25)
+		return;
+
+	skb = alloc_skb(1, GFP_ATOMIC);
+	if (!skb) {
+		pr_err("x25_dev: out of memory\n");
+		return;
+	}
+
+	ptr  = skb_put(skb, 1);
+	*ptr = X25_IFACE_DISCONNECT;
+
+	skb->protocol = htons(ETH_P_X25);
+	skb->dev      = nb->dev;
+	dev_queue_xmit(skb);
+}
+
+void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
+{
+	unsigned char *dptr;
+
+	skb_reset_network_header(skb);
+
+	switch (nb->dev->type) {
+	case ARPHRD_X25:
+		dptr  = skb_push(skb, 1);
+		*dptr = X25_IFACE_DATA;
+		break;
+
+	default:
+		kfree_skb(skb);
+		return;
+	}
+
+	skb->protocol = htons(ETH_P_X25);
+	skb->dev      = nb->dev;
+
+	dev_queue_xmit(skb);
+}
diff --git a/net/x25/x25_facilities.c b/net/x25/x25_facilities.c
new file mode 100644
index 000000000..8e1a49b0c
--- /dev/null
+++ b/net/x25/x25_facilities.c
@@ -0,0 +1,350 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine,
+ *	randomly fail to work with new releases, misbehave and/or generally
+ *	screw up. It might even work.
+ *
+ *	This code REQUIRES 2.1.15 or higher
+ *
+ *	History
+ *	X.25 001	Split from x25_subr.c
+ *	mar/20/00	Daniela Squassoni Disabling/enabling of facilities
+ *					  negotiation.
+ *	apr/14/05	Shaun Pereira - Allow fast select with no restriction
+ *					on response.
+ */
+
+#define pr_fmt(fmt) "X25: " fmt
+
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/x25.h>
+
+/**
+ * x25_parse_facilities - Parse facilities from skb into the facilities structs
+ *
+ * @skb: sk_buff to parse
+ * @facilities: Regular facilities, updated as facilities are found
+ * @dte_facs: ITU DTE facilities, updated as DTE facilities are found
+ * @vc_fac_mask: mask is updated with all facilities found
+ *
+ * Return codes:
+ *  -1 - Parsing error, caller should drop call and clean up
+ *   0 - Parse OK, this skb has no facilities
+ *  >0 - Parse OK, returns the length of the facilities header
+ *
+ */
+int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
+		struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
+{
+	unsigned char *p;
+	unsigned int len;
+
+	*vc_fac_mask = 0;
+
+	/*
+	 * The kernel knows which facilities were set on an incoming call but
+	 * currently this information is not available to userspace.  Here we
+	 * give userspace who read incoming call facilities 0 length to indicate
+	 * it wasn't set.
+	 */
+	dte_facs->calling_len = 0;
+	dte_facs->called_len = 0;
+	memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae));
+	memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae));
+
+	if (!pskb_may_pull(skb, 1))
+		return 0;
+
+	len = skb->data[0];
+
+	if (!pskb_may_pull(skb, 1 + len))
+		return -1;
+
+	p = skb->data + 1;
+
+	while (len > 0) {
+		switch (*p & X25_FAC_CLASS_MASK) {
+		case X25_FAC_CLASS_A:
+			if (len < 2)
+				return -1;
+			switch (*p) {
+			case X25_FAC_REVERSE:
+				if((p[1] & 0x81) == 0x81) {
+					facilities->reverse = p[1] & 0x81;
+					*vc_fac_mask |= X25_MASK_REVERSE;
+					break;
+				}
+
+				if((p[1] & 0x01) == 0x01) {
+					facilities->reverse = p[1] & 0x01;
+					*vc_fac_mask |= X25_MASK_REVERSE;
+					break;
+				}
+
+				if((p[1] & 0x80) == 0x80) {
+					facilities->reverse = p[1] & 0x80;
+					*vc_fac_mask |= X25_MASK_REVERSE;
+					break;
+				}
+
+				if(p[1] == 0x00) {
+					facilities->reverse
+						= X25_DEFAULT_REVERSE;
+					*vc_fac_mask |= X25_MASK_REVERSE;
+					break;
+				}
+				fallthrough;
+			case X25_FAC_THROUGHPUT:
+				facilities->throughput = p[1];
+				*vc_fac_mask |= X25_MASK_THROUGHPUT;
+				break;
+			case X25_MARKER:
+				break;
+			default:
+				pr_debug("unknown facility "
+				       "%02X, value %02X\n",
+				       p[0], p[1]);
+				break;
+			}
+			p   += 2;
+			len -= 2;
+			break;
+		case X25_FAC_CLASS_B:
+			if (len < 3)
+				return -1;
+			switch (*p) {
+			case X25_FAC_PACKET_SIZE:
+				facilities->pacsize_in  = p[1];
+				facilities->pacsize_out = p[2];
+				*vc_fac_mask |= X25_MASK_PACKET_SIZE;
+				break;
+			case X25_FAC_WINDOW_SIZE:
+				facilities->winsize_in  = p[1];
+				facilities->winsize_out = p[2];
+				*vc_fac_mask |= X25_MASK_WINDOW_SIZE;
+				break;
+			default:
+				pr_debug("unknown facility "
+				       "%02X, values %02X, %02X\n",
+				       p[0], p[1], p[2]);
+				break;
+			}
+			p   += 3;
+			len -= 3;
+			break;
+		case X25_FAC_CLASS_C:
+			if (len < 4)
+				return -1;
+			pr_debug("unknown facility %02X, "
+			       "values %02X, %02X, %02X\n",
+			       p[0], p[1], p[2], p[3]);
+			p   += 4;
+			len -= 4;
+			break;
+		case X25_FAC_CLASS_D:
+			if (len < p[1] + 2)
+				return -1;
+			switch (*p) {
+			case X25_FAC_CALLING_AE:
+				if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
+					return -1;
+				if (p[2] > X25_MAX_AE_LEN)
+					return -1;
+				dte_facs->calling_len = p[2];
+				memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
+				*vc_fac_mask |= X25_MASK_CALLING_AE;
+				break;
+			case X25_FAC_CALLED_AE:
+				if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
+					return -1;
+				if (p[2] > X25_MAX_AE_LEN)
+					return -1;
+				dte_facs->called_len = p[2];
+				memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
+				*vc_fac_mask |= X25_MASK_CALLED_AE;
+				break;
+			default:
+				pr_debug("unknown facility %02X,"
+					"length %d\n", p[0], p[1]);
+				break;
+			}
+			len -= p[1] + 2;
+			p += p[1] + 2;
+			break;
+		}
+	}
+
+	return p - skb->data;
+}
+
+/*
+ *	Create a set of facilities.
+ */
+int x25_create_facilities(unsigned char *buffer,
+		struct x25_facilities *facilities,
+		struct x25_dte_facilities *dte_facs, unsigned long facil_mask)
+{
+	unsigned char *p = buffer + 1;
+	int len;
+
+	if (!facil_mask) {
+		/*
+		 * Length of the facilities field in call_req or
+		 * call_accept packets
+		 */
+		buffer[0] = 0;
+		len = 1; /* 1 byte for the length field */
+		return len;
+	}
+
+	if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
+		*p++ = X25_FAC_REVERSE;
+		*p++ = facilities->reverse;
+	}
+
+	if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
+		*p++ = X25_FAC_THROUGHPUT;
+		*p++ = facilities->throughput;
+	}
+
+	if ((facilities->pacsize_in || facilities->pacsize_out) &&
+	    (facil_mask & X25_MASK_PACKET_SIZE)) {
+		*p++ = X25_FAC_PACKET_SIZE;
+		*p++ = facilities->pacsize_in ? : facilities->pacsize_out;
+		*p++ = facilities->pacsize_out ? : facilities->pacsize_in;
+	}
+
+	if ((facilities->winsize_in || facilities->winsize_out) &&
+	    (facil_mask & X25_MASK_WINDOW_SIZE)) {
+		*p++ = X25_FAC_WINDOW_SIZE;
+		*p++ = facilities->winsize_in ? : facilities->winsize_out;
+		*p++ = facilities->winsize_out ? : facilities->winsize_in;
+	}
+
+	if (facil_mask & (X25_MASK_CALLING_AE|X25_MASK_CALLED_AE)) {
+		*p++ = X25_MARKER;
+		*p++ = X25_DTE_SERVICES;
+	}
+
+	if (dte_facs->calling_len && (facil_mask & X25_MASK_CALLING_AE)) {
+		unsigned int bytecount = (dte_facs->calling_len + 1) >> 1;
+		*p++ = X25_FAC_CALLING_AE;
+		*p++ = 1 + bytecount;
+		*p++ = dte_facs->calling_len;
+		memcpy(p, dte_facs->calling_ae, bytecount);
+		p += bytecount;
+	}
+
+	if (dte_facs->called_len && (facil_mask & X25_MASK_CALLED_AE)) {
+		unsigned int bytecount = (dte_facs->called_len % 2) ?
+		dte_facs->called_len / 2 + 1 :
+		dte_facs->called_len / 2;
+		*p++ = X25_FAC_CALLED_AE;
+		*p++ = 1 + bytecount;
+		*p++ = dte_facs->called_len;
+		memcpy(p, dte_facs->called_ae, bytecount);
+		p+=bytecount;
+	}
+
+	len       = p - buffer;
+	buffer[0] = len - 1;
+
+	return len;
+}
+
+/*
+ *	Try to reach a compromise on a set of facilities.
+ *
+ *	The only real problem is with reverse charging.
+ */
+int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
+		struct x25_facilities *new, struct x25_dte_facilities *dte)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+	struct x25_facilities *ours = &x25->facilities;
+	struct x25_facilities theirs;
+	int len;
+
+	memset(&theirs, 0, sizeof(theirs));
+	memcpy(new, ours, sizeof(*new));
+	memset(dte, 0, sizeof(*dte));
+
+	len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
+	if (len < 0)
+		return len;
+
+	/*
+	 *	They want reverse charging, we won't accept it.
+	 */
+	if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
+		SOCK_DEBUG(sk, "X.25: rejecting reverse charging request\n");
+		return -1;
+	}
+
+	new->reverse = theirs.reverse;
+
+	if (theirs.throughput) {
+		int theirs_in =  theirs.throughput & 0x0f;
+		int theirs_out = theirs.throughput & 0xf0;
+		int ours_in  = ours->throughput & 0x0f;
+		int ours_out = ours->throughput & 0xf0;
+		if (!ours_in || theirs_in < ours_in) {
+			SOCK_DEBUG(sk, "X.25: inbound throughput negotiated\n");
+			new->throughput = (new->throughput & 0xf0) | theirs_in;
+		}
+		if (!ours_out || theirs_out < ours_out) {
+			SOCK_DEBUG(sk,
+				"X.25: outbound throughput negotiated\n");
+			new->throughput = (new->throughput & 0x0f) | theirs_out;
+		}
+	}
+
+	if (theirs.pacsize_in && theirs.pacsize_out) {
+		if (theirs.pacsize_in < ours->pacsize_in) {
+			SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down\n");
+			new->pacsize_in = theirs.pacsize_in;
+		}
+		if (theirs.pacsize_out < ours->pacsize_out) {
+			SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down\n");
+			new->pacsize_out = theirs.pacsize_out;
+		}
+	}
+
+	if (theirs.winsize_in && theirs.winsize_out) {
+		if (theirs.winsize_in < ours->winsize_in) {
+			SOCK_DEBUG(sk, "X.25: window size inwards negotiated down\n");
+			new->winsize_in = theirs.winsize_in;
+		}
+		if (theirs.winsize_out < ours->winsize_out) {
+			SOCK_DEBUG(sk, "X.25: window size outwards negotiated down\n");
+			new->winsize_out = theirs.winsize_out;
+		}
+	}
+
+	return len;
+}
+
+/*
+ *	Limit values of certain facilities according to the capability of the
+ *      currently attached x25 link.
+ */
+void x25_limit_facilities(struct x25_facilities *facilities,
+			  struct x25_neigh *nb)
+{
+
+	if (!nb->extended) {
+		if (facilities->winsize_in  > 7) {
+			pr_debug("incoming winsize limited to 7\n");
+			facilities->winsize_in = 7;
+		}
+		if (facilities->winsize_out > 7) {
+			facilities->winsize_out = 7;
+			pr_debug("outgoing winsize limited to 7\n");
+		}
+	}
+}
diff --git a/net/x25/x25_forward.c b/net/x25/x25_forward.c
new file mode 100644
index 000000000..21b30b56e
--- /dev/null
+++ b/net/x25/x25_forward.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	History
+ *	03-01-2007	Added forwarding for x.25	Andrew Hendry
+ */
+
+#define pr_fmt(fmt) "X25: " fmt
+
+#include <linux/if_arp.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <net/x25.h>
+
+LIST_HEAD(x25_forward_list);
+DEFINE_RWLOCK(x25_forward_list_lock);
+
+int x25_forward_call(struct x25_address *dest_addr, struct x25_neigh *from,
+			struct sk_buff *skb, int lci)
+{
+	struct x25_route *rt;
+	struct x25_neigh *neigh_new = NULL;
+	struct x25_forward *x25_frwd, *new_frwd;
+	struct sk_buff *skbn;
+	short same_lci = 0;
+	int rc = 0;
+
+	if ((rt = x25_get_route(dest_addr)) == NULL)
+		goto out_no_route;
+
+	if ((neigh_new = x25_get_neigh(rt->dev)) == NULL) {
+		/* This shouldn't happen, if it occurs somehow
+		 * do something sensible
+		 */
+		goto out_put_route;
+	}
+
+	/* Avoid a loop. This is the normal exit path for a
+	 * system with only one x.25 iface and default route
+	 */
+	if (rt->dev == from->dev) {
+		goto out_put_nb;
+	}
+
+	/* Remote end sending a call request on an already
+	 * established LCI? It shouldn't happen, just in case..
+	 */
+	read_lock_bh(&x25_forward_list_lock);
+	list_for_each_entry(x25_frwd, &x25_forward_list, node) {
+		if (x25_frwd->lci == lci) {
+			pr_warn("call request for lci which is already registered!, transmitting but not registering new pair\n");
+			same_lci = 1;
+		}
+	}
+	read_unlock_bh(&x25_forward_list_lock);
+
+	/* Save the forwarding details for future traffic */
+	if (!same_lci){
+		if ((new_frwd = kmalloc(sizeof(struct x25_forward),
+						GFP_ATOMIC)) == NULL){
+			rc = -ENOMEM;
+			goto out_put_nb;
+		}
+		new_frwd->lci = lci;
+		new_frwd->dev1 = rt->dev;
+		new_frwd->dev2 = from->dev;
+		write_lock_bh(&x25_forward_list_lock);
+		list_add(&new_frwd->node, &x25_forward_list);
+		write_unlock_bh(&x25_forward_list_lock);
+	}
+
+	/* Forward the call request */
+	if ( (skbn = skb_clone(skb, GFP_ATOMIC)) == NULL){
+		goto out_put_nb;
+	}
+	x25_transmit_link(skbn, neigh_new);
+	rc = 1;
+
+
+out_put_nb:
+	x25_neigh_put(neigh_new);
+
+out_put_route:
+	x25_route_put(rt);
+
+out_no_route:
+	return rc;
+}
+
+
+int x25_forward_data(int lci, struct x25_neigh *from, struct sk_buff *skb) {
+
+	struct x25_forward *frwd;
+	struct net_device *peer = NULL;
+	struct x25_neigh *nb;
+	struct sk_buff *skbn;
+	int rc = 0;
+
+	read_lock_bh(&x25_forward_list_lock);
+	list_for_each_entry(frwd, &x25_forward_list, node) {
+		if (frwd->lci == lci) {
+			/* The call is established, either side can send */
+			if (from->dev == frwd->dev1) {
+				peer = frwd->dev2;
+			} else {
+				peer = frwd->dev1;
+			}
+			break;
+		}
+	}
+	read_unlock_bh(&x25_forward_list_lock);
+
+	if ( (nb = x25_get_neigh(peer)) == NULL)
+		goto out;
+
+	if ( (skbn = pskb_copy(skb, GFP_ATOMIC)) == NULL){
+		goto output;
+
+	}
+	x25_transmit_link(skbn, nb);
+
+	rc = 1;
+output:
+	x25_neigh_put(nb);
+out:
+	return rc;
+}
+
+void x25_clear_forward_by_lci(unsigned int lci)
+{
+	struct x25_forward *fwd, *tmp;
+
+	write_lock_bh(&x25_forward_list_lock);
+
+	list_for_each_entry_safe(fwd, tmp, &x25_forward_list, node) {
+		if (fwd->lci == lci) {
+			list_del(&fwd->node);
+			kfree(fwd);
+		}
+	}
+	write_unlock_bh(&x25_forward_list_lock);
+}
+
+
+void x25_clear_forward_by_dev(struct net_device *dev)
+{
+	struct x25_forward *fwd, *tmp;
+
+	write_lock_bh(&x25_forward_list_lock);
+
+	list_for_each_entry_safe(fwd, tmp, &x25_forward_list, node) {
+		if ((fwd->dev1 == dev) || (fwd->dev2 == dev)){
+			list_del(&fwd->node);
+			kfree(fwd);
+		}
+	}
+	write_unlock_bh(&x25_forward_list_lock);
+}
diff --git a/net/x25/x25_in.c b/net/x25/x25_in.c
new file mode 100644
index 000000000..b981a4828
--- /dev/null
+++ b/net/x25/x25_in.c
@@ -0,0 +1,456 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine,
+ *	randomly fail to work with new releases, misbehave and/or generally
+ *	screw up. It might even work.
+ *
+ *	This code REQUIRES 2.1.15 or higher
+ *
+ *	History
+ *	X.25 001	Jonathan Naylor	  Started coding.
+ *	X.25 002	Jonathan Naylor	  Centralised disconnection code.
+ *					  New timer architecture.
+ *	2000-03-20	Daniela Squassoni Disabling/enabling of facilities
+ *					  negotiation.
+ *	2000-11-10	Henner Eisen	  Check and reset for out-of-sequence
+ *					  i-frames.
+ */
+
+#define pr_fmt(fmt) "X25: " fmt
+
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/tcp_states.h>
+#include <net/x25.h>
+
+static int x25_queue_rx_frame(struct sock *sk, struct sk_buff *skb, int more)
+{
+	struct sk_buff *skbo, *skbn = skb;
+	struct x25_sock *x25 = x25_sk(sk);
+
+	if (more) {
+		x25->fraglen += skb->len;
+		skb_queue_tail(&x25->fragment_queue, skb);
+		skb_set_owner_r(skb, sk);
+		return 0;
+	}
+
+	if (x25->fraglen > 0) {	/* End of fragment */
+		int len = x25->fraglen + skb->len;
+
+		if ((skbn = alloc_skb(len, GFP_ATOMIC)) == NULL){
+			kfree_skb(skb);
+			return 1;
+		}
+
+		skb_queue_tail(&x25->fragment_queue, skb);
+
+		skb_reset_transport_header(skbn);
+
+		skbo = skb_dequeue(&x25->fragment_queue);
+		skb_copy_from_linear_data(skbo, skb_put(skbn, skbo->len),
+					  skbo->len);
+		kfree_skb(skbo);
+
+		while ((skbo =
+			skb_dequeue(&x25->fragment_queue)) != NULL) {
+			skb_pull(skbo, (x25->neighbour->extended) ?
+					X25_EXT_MIN_LEN : X25_STD_MIN_LEN);
+			skb_copy_from_linear_data(skbo,
+						  skb_put(skbn, skbo->len),
+						  skbo->len);
+			kfree_skb(skbo);
+		}
+
+		x25->fraglen = 0;
+	}
+
+	skb_set_owner_r(skbn, sk);
+	skb_queue_tail(&sk->sk_receive_queue, skbn);
+	if (!sock_flag(sk, SOCK_DEAD))
+		sk->sk_data_ready(sk);
+
+	return 0;
+}
+
+/*
+ * State machine for state 1, Awaiting Call Accepted State.
+ * The handling of the timer(s) is in file x25_timer.c.
+ * Handling of state 0 and connection release is in af_x25.c.
+ */
+static int x25_state1_machine(struct sock *sk, struct sk_buff *skb, int frametype)
+{
+	struct x25_address source_addr, dest_addr;
+	int len;
+	struct x25_sock *x25 = x25_sk(sk);
+
+	switch (frametype) {
+	case X25_CALL_ACCEPTED: {
+
+		x25_stop_timer(sk);
+		x25->condition = 0x00;
+		x25->vs        = 0;
+		x25->va        = 0;
+		x25->vr        = 0;
+		x25->vl        = 0;
+		x25->state     = X25_STATE_3;
+		sk->sk_state   = TCP_ESTABLISHED;
+		/*
+		 *	Parse the data in the frame.
+		 */
+		if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+			goto out_clear;
+		skb_pull(skb, X25_STD_MIN_LEN);
+
+		len = x25_parse_address_block(skb, &source_addr,
+					      &dest_addr);
+		if (len > 0)
+			skb_pull(skb, len);
+		else if (len < 0)
+			goto out_clear;
+
+		len = x25_parse_facilities(skb, &x25->facilities,
+					   &x25->dte_facilities,
+					   &x25->vc_facil_mask);
+		if (len > 0)
+			skb_pull(skb, len);
+		else if (len < 0)
+			goto out_clear;
+		/*
+		 *	Copy any Call User Data.
+		 */
+		if (skb->len > 0) {
+			if (skb->len > X25_MAX_CUD_LEN)
+				goto out_clear;
+
+			skb_copy_bits(skb, 0, x25->calluserdata.cuddata,
+				skb->len);
+			x25->calluserdata.cudlength = skb->len;
+		}
+		if (!sock_flag(sk, SOCK_DEAD))
+			sk->sk_state_change(sk);
+		break;
+	}
+	case X25_CALL_REQUEST:
+		/* call collision */
+		x25->causediag.cause      = 0x01;
+		x25->causediag.diagnostic = 0x48;
+
+		x25_write_internal(sk, X25_CLEAR_REQUEST);
+		x25_disconnect(sk, EISCONN, 0x01, 0x48);
+		break;
+
+	case X25_CLEAR_REQUEST:
+		if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+			goto out_clear;
+
+		x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
+		x25_disconnect(sk, ECONNREFUSED, skb->data[3], skb->data[4]);
+		break;
+
+	default:
+		break;
+	}
+
+	return 0;
+
+out_clear:
+	x25_write_internal(sk, X25_CLEAR_REQUEST);
+	x25->state = X25_STATE_2;
+	x25_start_t23timer(sk);
+	return 0;
+}
+
+/*
+ * State machine for state 2, Awaiting Clear Confirmation State.
+ * The handling of the timer(s) is in file x25_timer.c
+ * Handling of state 0 and connection release is in af_x25.c.
+ */
+static int x25_state2_machine(struct sock *sk, struct sk_buff *skb, int frametype)
+{
+	switch (frametype) {
+
+		case X25_CLEAR_REQUEST:
+			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+				goto out_clear;
+
+			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
+			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
+			break;
+
+		case X25_CLEAR_CONFIRMATION:
+			x25_disconnect(sk, 0, 0, 0);
+			break;
+
+		default:
+			break;
+	}
+
+	return 0;
+
+out_clear:
+	x25_write_internal(sk, X25_CLEAR_REQUEST);
+	x25_start_t23timer(sk);
+	return 0;
+}
+
+/*
+ * State machine for state 3, Connected State.
+ * The handling of the timer(s) is in file x25_timer.c
+ * Handling of state 0 and connection release is in af_x25.c.
+ */
+static int x25_state3_machine(struct sock *sk, struct sk_buff *skb, int frametype, int ns, int nr, int q, int d, int m)
+{
+	int queued = 0;
+	int modulus;
+	struct x25_sock *x25 = x25_sk(sk);
+
+	modulus = (x25->neighbour->extended) ? X25_EMODULUS : X25_SMODULUS;
+
+	switch (frametype) {
+
+		case X25_RESET_REQUEST:
+			x25_write_internal(sk, X25_RESET_CONFIRMATION);
+			x25_stop_timer(sk);
+			x25->condition = 0x00;
+			x25->vs        = 0;
+			x25->vr        = 0;
+			x25->va        = 0;
+			x25->vl        = 0;
+			x25_requeue_frames(sk);
+			break;
+
+		case X25_CLEAR_REQUEST:
+			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+				goto out_clear;
+
+			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
+			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
+			break;
+
+		case X25_RR:
+		case X25_RNR:
+			if (!x25_validate_nr(sk, nr)) {
+				x25_clear_queues(sk);
+				x25_write_internal(sk, X25_RESET_REQUEST);
+				x25_start_t22timer(sk);
+				x25->condition = 0x00;
+				x25->vs        = 0;
+				x25->vr        = 0;
+				x25->va        = 0;
+				x25->vl        = 0;
+				x25->state     = X25_STATE_4;
+			} else {
+				x25_frames_acked(sk, nr);
+				if (frametype == X25_RNR) {
+					x25->condition |= X25_COND_PEER_RX_BUSY;
+				} else {
+					x25->condition &= ~X25_COND_PEER_RX_BUSY;
+				}
+			}
+			break;
+
+		case X25_DATA:	/* XXX */
+			x25->condition &= ~X25_COND_PEER_RX_BUSY;
+			if ((ns != x25->vr) || !x25_validate_nr(sk, nr)) {
+				x25_clear_queues(sk);
+				x25_write_internal(sk, X25_RESET_REQUEST);
+				x25_start_t22timer(sk);
+				x25->condition = 0x00;
+				x25->vs        = 0;
+				x25->vr        = 0;
+				x25->va        = 0;
+				x25->vl        = 0;
+				x25->state     = X25_STATE_4;
+				break;
+			}
+			x25_frames_acked(sk, nr);
+			if (ns == x25->vr) {
+				if (x25_queue_rx_frame(sk, skb, m) == 0) {
+					x25->vr = (x25->vr + 1) % modulus;
+					queued = 1;
+				} else {
+					/* Should never happen */
+					x25_clear_queues(sk);
+					x25_write_internal(sk, X25_RESET_REQUEST);
+					x25_start_t22timer(sk);
+					x25->condition = 0x00;
+					x25->vs        = 0;
+					x25->vr        = 0;
+					x25->va        = 0;
+					x25->vl        = 0;
+					x25->state     = X25_STATE_4;
+					break;
+				}
+				if (atomic_read(&sk->sk_rmem_alloc) >
+				    (sk->sk_rcvbuf >> 1))
+					x25->condition |= X25_COND_OWN_RX_BUSY;
+			}
+			/*
+			 *	If the window is full Ack it immediately, else
+			 *	start the holdback timer.
+			 */
+			if (((x25->vl + x25->facilities.winsize_in) % modulus) == x25->vr) {
+				x25->condition &= ~X25_COND_ACK_PENDING;
+				x25_stop_timer(sk);
+				x25_enquiry_response(sk);
+			} else {
+				x25->condition |= X25_COND_ACK_PENDING;
+				x25_start_t2timer(sk);
+			}
+			break;
+
+		case X25_INTERRUPT_CONFIRMATION:
+			clear_bit(X25_INTERRUPT_FLAG, &x25->flags);
+			break;
+
+		case X25_INTERRUPT:
+			if (sock_flag(sk, SOCK_URGINLINE))
+				queued = !sock_queue_rcv_skb(sk, skb);
+			else {
+				skb_set_owner_r(skb, sk);
+				skb_queue_tail(&x25->interrupt_in_queue, skb);
+				queued = 1;
+			}
+			sk_send_sigurg(sk);
+			x25_write_internal(sk, X25_INTERRUPT_CONFIRMATION);
+			break;
+
+		default:
+			pr_warn("unknown %02X in state 3\n", frametype);
+			break;
+	}
+
+	return queued;
+
+out_clear:
+	x25_write_internal(sk, X25_CLEAR_REQUEST);
+	x25->state = X25_STATE_2;
+	x25_start_t23timer(sk);
+	return 0;
+}
+
+/*
+ * State machine for state 4, Awaiting Reset Confirmation State.
+ * The handling of the timer(s) is in file x25_timer.c
+ * Handling of state 0 and connection release is in af_x25.c.
+ */
+static int x25_state4_machine(struct sock *sk, struct sk_buff *skb, int frametype)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	switch (frametype) {
+
+		case X25_RESET_REQUEST:
+			x25_write_internal(sk, X25_RESET_CONFIRMATION);
+			fallthrough;
+		case X25_RESET_CONFIRMATION: {
+			x25_stop_timer(sk);
+			x25->condition = 0x00;
+			x25->va        = 0;
+			x25->vr        = 0;
+			x25->vs        = 0;
+			x25->vl        = 0;
+			x25->state     = X25_STATE_3;
+			x25_requeue_frames(sk);
+			break;
+		}
+		case X25_CLEAR_REQUEST:
+			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2))
+				goto out_clear;
+
+			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
+			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
+			break;
+
+		default:
+			break;
+	}
+
+	return 0;
+
+out_clear:
+	x25_write_internal(sk, X25_CLEAR_REQUEST);
+	x25->state = X25_STATE_2;
+	x25_start_t23timer(sk);
+	return 0;
+}
+
+/*
+ * State machine for state 5, Call Accepted / Call Connected pending (X25_ACCPT_APPRV_FLAG).
+ * The handling of the timer(s) is in file x25_timer.c
+ * Handling of state 0 and connection release is in af_x25.c.
+ */
+static int x25_state5_machine(struct sock *sk, struct sk_buff *skb, int frametype)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	switch (frametype) {
+		case X25_CLEAR_REQUEST:
+			if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 2)) {
+				x25_write_internal(sk, X25_CLEAR_REQUEST);
+				x25->state = X25_STATE_2;
+				x25_start_t23timer(sk);
+				return 0;
+			}
+
+			x25_write_internal(sk, X25_CLEAR_CONFIRMATION);
+			x25_disconnect(sk, 0, skb->data[3], skb->data[4]);
+			break;
+
+		default:
+			break;
+	}
+
+	return 0;
+}
+
+/* Higher level upcall for a LAPB frame */
+int x25_process_rx_frame(struct sock *sk, struct sk_buff *skb)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+	int queued = 0, frametype, ns, nr, q, d, m;
+
+	if (x25->state == X25_STATE_0)
+		return 0;
+
+	frametype = x25_decode(sk, skb, &ns, &nr, &q, &d, &m);
+
+	switch (x25->state) {
+	case X25_STATE_1:
+		queued = x25_state1_machine(sk, skb, frametype);
+		break;
+	case X25_STATE_2:
+		queued = x25_state2_machine(sk, skb, frametype);
+		break;
+	case X25_STATE_3:
+		queued = x25_state3_machine(sk, skb, frametype, ns, nr, q, d, m);
+		break;
+	case X25_STATE_4:
+		queued = x25_state4_machine(sk, skb, frametype);
+		break;
+	case X25_STATE_5:
+		queued = x25_state5_machine(sk, skb, frametype);
+		break;
+	}
+
+	x25_kick(sk);
+
+	return queued;
+}
+
+int x25_backlog_rcv(struct sock *sk, struct sk_buff *skb)
+{
+	int queued = x25_process_rx_frame(sk, skb);
+
+	if (!queued)
+		kfree_skb(skb);
+
+	return 0;
+}
diff --git a/net/x25/x25_link.c b/net/x25/x25_link.c
new file mode 100644
index 000000000..5460b9146
--- /dev/null
+++ b/net/x25/x25_link.c
@@ -0,0 +1,421 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine,
+ *	randomly fail to work with new releases, misbehave and/or generally
+ *	screw up. It might even work.
+ *
+ *	This code REQUIRES 2.1.15 or higher
+ *
+ *	History
+ *	X.25 001	Jonathan Naylor	  Started coding.
+ *	X.25 002	Jonathan Naylor	  New timer architecture.
+ *	mar/20/00	Daniela Squassoni Disabling/enabling of facilities
+ *					  negotiation.
+ *	2000-09-04	Henner Eisen	  dev_hold() / dev_put() for x25_neigh.
+ */
+
+#define pr_fmt(fmt) "X25: " fmt
+
+#include <linux/kernel.h>
+#include <linux/jiffies.h>
+#include <linux/timer.h>
+#include <linux/slab.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/uaccess.h>
+#include <linux/init.h>
+#include <net/x25.h>
+
+LIST_HEAD(x25_neigh_list);
+DEFINE_RWLOCK(x25_neigh_list_lock);
+
+static void x25_t20timer_expiry(struct timer_list *);
+
+static void x25_transmit_restart_confirmation(struct x25_neigh *nb);
+static void x25_transmit_restart_request(struct x25_neigh *nb);
+
+/*
+ *	Linux set/reset timer routines
+ */
+static inline void x25_start_t20timer(struct x25_neigh *nb)
+{
+	mod_timer(&nb->t20timer, jiffies + nb->t20);
+}
+
+static void x25_t20timer_expiry(struct timer_list *t)
+{
+	struct x25_neigh *nb = from_timer(nb, t, t20timer);
+
+	x25_transmit_restart_request(nb);
+
+	x25_start_t20timer(nb);
+}
+
+static inline void x25_stop_t20timer(struct x25_neigh *nb)
+{
+	del_timer(&nb->t20timer);
+}
+
+/*
+ *	This handles all restart and diagnostic frames.
+ */
+void x25_link_control(struct sk_buff *skb, struct x25_neigh *nb,
+		      unsigned short frametype)
+{
+	struct sk_buff *skbn;
+
+	switch (frametype) {
+	case X25_RESTART_REQUEST:
+		switch (nb->state) {
+		case X25_LINK_STATE_0:
+			/* This can happen when the x25 module just gets loaded
+			 * and doesn't know layer 2 has already connected
+			 */
+			nb->state = X25_LINK_STATE_3;
+			x25_transmit_restart_confirmation(nb);
+			break;
+		case X25_LINK_STATE_2:
+			x25_stop_t20timer(nb);
+			nb->state = X25_LINK_STATE_3;
+			break;
+		case X25_LINK_STATE_3:
+			/* clear existing virtual calls */
+			x25_kill_by_neigh(nb);
+
+			x25_transmit_restart_confirmation(nb);
+			break;
+		}
+		break;
+
+	case X25_RESTART_CONFIRMATION:
+		switch (nb->state) {
+		case X25_LINK_STATE_2:
+			x25_stop_t20timer(nb);
+			nb->state = X25_LINK_STATE_3;
+			break;
+		case X25_LINK_STATE_3:
+			/* clear existing virtual calls */
+			x25_kill_by_neigh(nb);
+
+			x25_transmit_restart_request(nb);
+			nb->state = X25_LINK_STATE_2;
+			x25_start_t20timer(nb);
+			break;
+		}
+		break;
+
+	case X25_DIAGNOSTIC:
+		if (!pskb_may_pull(skb, X25_STD_MIN_LEN + 4))
+			break;
+
+		pr_warn("diagnostic #%d - %02X %02X %02X\n",
+		       skb->data[3], skb->data[4],
+		       skb->data[5], skb->data[6]);
+		break;
+
+	default:
+		pr_warn("received unknown %02X with LCI 000\n",
+		       frametype);
+		break;
+	}
+
+	if (nb->state == X25_LINK_STATE_3)
+		while ((skbn = skb_dequeue(&nb->queue)) != NULL)
+			x25_send_frame(skbn, nb);
+}
+
+/*
+ *	This routine is called when a Restart Request is needed
+ */
+static void x25_transmit_restart_request(struct x25_neigh *nb)
+{
+	unsigned char *dptr;
+	int len = X25_MAX_L2_LEN + X25_STD_MIN_LEN + 2;
+	struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);
+
+	if (!skb)
+		return;
+
+	skb_reserve(skb, X25_MAX_L2_LEN);
+
+	dptr = skb_put(skb, X25_STD_MIN_LEN + 2);
+
+	*dptr++ = nb->extended ? X25_GFI_EXTSEQ : X25_GFI_STDSEQ;
+	*dptr++ = 0x00;
+	*dptr++ = X25_RESTART_REQUEST;
+	*dptr++ = 0x00;
+	*dptr++ = 0;
+
+	skb->sk = NULL;
+
+	x25_send_frame(skb, nb);
+}
+
+/*
+ * This routine is called when a Restart Confirmation is needed
+ */
+static void x25_transmit_restart_confirmation(struct x25_neigh *nb)
+{
+	unsigned char *dptr;
+	int len = X25_MAX_L2_LEN + X25_STD_MIN_LEN;
+	struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);
+
+	if (!skb)
+		return;
+
+	skb_reserve(skb, X25_MAX_L2_LEN);
+
+	dptr = skb_put(skb, X25_STD_MIN_LEN);
+
+	*dptr++ = nb->extended ? X25_GFI_EXTSEQ : X25_GFI_STDSEQ;
+	*dptr++ = 0x00;
+	*dptr++ = X25_RESTART_CONFIRMATION;
+
+	skb->sk = NULL;
+
+	x25_send_frame(skb, nb);
+}
+
+/*
+ *	This routine is called when a Clear Request is needed outside of the context
+ *	of a connected socket.
+ */
+void x25_transmit_clear_request(struct x25_neigh *nb, unsigned int lci,
+				unsigned char cause)
+{
+	unsigned char *dptr;
+	int len = X25_MAX_L2_LEN + X25_STD_MIN_LEN + 2;
+	struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);
+
+	if (!skb)
+		return;
+
+	skb_reserve(skb, X25_MAX_L2_LEN);
+
+	dptr = skb_put(skb, X25_STD_MIN_LEN + 2);
+
+	*dptr++ = ((lci >> 8) & 0x0F) | (nb->extended ?
+					 X25_GFI_EXTSEQ :
+					 X25_GFI_STDSEQ);
+	*dptr++ = (lci >> 0) & 0xFF;
+	*dptr++ = X25_CLEAR_REQUEST;
+	*dptr++ = cause;
+	*dptr++ = 0x00;
+
+	skb->sk = NULL;
+
+	x25_send_frame(skb, nb);
+}
+
+void x25_transmit_link(struct sk_buff *skb, struct x25_neigh *nb)
+{
+	switch (nb->state) {
+	case X25_LINK_STATE_0:
+		skb_queue_tail(&nb->queue, skb);
+		nb->state = X25_LINK_STATE_1;
+		x25_establish_link(nb);
+		break;
+	case X25_LINK_STATE_1:
+	case X25_LINK_STATE_2:
+		skb_queue_tail(&nb->queue, skb);
+		break;
+	case X25_LINK_STATE_3:
+		x25_send_frame(skb, nb);
+		break;
+	}
+}
+
+/*
+ *	Called when the link layer has become established.
+ */
+void x25_link_established(struct x25_neigh *nb)
+{
+	switch (nb->state) {
+	case X25_LINK_STATE_0:
+	case X25_LINK_STATE_1:
+		x25_transmit_restart_request(nb);
+		nb->state = X25_LINK_STATE_2;
+		x25_start_t20timer(nb);
+		break;
+	}
+}
+
+/*
+ *	Called when the link layer has terminated, or an establishment
+ *	request has failed.
+ */
+
+void x25_link_terminated(struct x25_neigh *nb)
+{
+	nb->state = X25_LINK_STATE_0;
+	skb_queue_purge(&nb->queue);
+	x25_stop_t20timer(nb);
+
+	/* Out of order: clear existing virtual calls (X.25 03/93 4.6.3) */
+	x25_kill_by_neigh(nb);
+}
+
+/*
+ *	Add a new device.
+ */
+void x25_link_device_up(struct net_device *dev)
+{
+	struct x25_neigh *nb = kmalloc(sizeof(*nb), GFP_ATOMIC);
+
+	if (!nb)
+		return;
+
+	skb_queue_head_init(&nb->queue);
+	timer_setup(&nb->t20timer, x25_t20timer_expiry, 0);
+
+	dev_hold(dev);
+	nb->dev      = dev;
+	nb->state    = X25_LINK_STATE_0;
+	nb->extended = 0;
+	/*
+	 * Enables negotiation
+	 */
+	nb->global_facil_mask = X25_MASK_REVERSE |
+				       X25_MASK_THROUGHPUT |
+				       X25_MASK_PACKET_SIZE |
+				       X25_MASK_WINDOW_SIZE;
+	nb->t20      = sysctl_x25_restart_request_timeout;
+	refcount_set(&nb->refcnt, 1);
+
+	write_lock_bh(&x25_neigh_list_lock);
+	list_add(&nb->node, &x25_neigh_list);
+	write_unlock_bh(&x25_neigh_list_lock);
+}
+
+/**
+ *	__x25_remove_neigh - remove neighbour from x25_neigh_list
+ *	@nb: - neigh to remove
+ *
+ *	Remove neighbour from x25_neigh_list. If it was there.
+ *	Caller must hold x25_neigh_list_lock.
+ */
+static void __x25_remove_neigh(struct x25_neigh *nb)
+{
+	if (nb->node.next) {
+		list_del(&nb->node);
+		x25_neigh_put(nb);
+	}
+}
+
+/*
+ *	A device has been removed, remove its links.
+ */
+void x25_link_device_down(struct net_device *dev)
+{
+	struct x25_neigh *nb;
+	struct list_head *entry, *tmp;
+
+	write_lock_bh(&x25_neigh_list_lock);
+
+	list_for_each_safe(entry, tmp, &x25_neigh_list) {
+		nb = list_entry(entry, struct x25_neigh, node);
+
+		if (nb->dev == dev) {
+			__x25_remove_neigh(nb);
+			dev_put(dev);
+		}
+	}
+
+	write_unlock_bh(&x25_neigh_list_lock);
+}
+
+/*
+ *	Given a device, return the neighbour address.
+ */
+struct x25_neigh *x25_get_neigh(struct net_device *dev)
+{
+	struct x25_neigh *nb, *use = NULL;
+
+	read_lock_bh(&x25_neigh_list_lock);
+	list_for_each_entry(nb, &x25_neigh_list, node) {
+		if (nb->dev == dev) {
+			use = nb;
+			break;
+		}
+	}
+
+	if (use)
+		x25_neigh_hold(use);
+	read_unlock_bh(&x25_neigh_list_lock);
+	return use;
+}
+
+/*
+ *	Handle the ioctls that control the subscription functions.
+ */
+int x25_subscr_ioctl(unsigned int cmd, void __user *arg)
+{
+	struct x25_subscrip_struct x25_subscr;
+	struct x25_neigh *nb;
+	struct net_device *dev;
+	int rc = -EINVAL;
+
+	if (cmd != SIOCX25GSUBSCRIP && cmd != SIOCX25SSUBSCRIP)
+		goto out;
+
+	rc = -EFAULT;
+	if (copy_from_user(&x25_subscr, arg, sizeof(x25_subscr)))
+		goto out;
+
+	rc = -EINVAL;
+	if ((dev = x25_dev_get(x25_subscr.device)) == NULL)
+		goto out;
+
+	if ((nb = x25_get_neigh(dev)) == NULL)
+		goto out_dev_put;
+
+	dev_put(dev);
+
+	if (cmd == SIOCX25GSUBSCRIP) {
+		read_lock_bh(&x25_neigh_list_lock);
+		x25_subscr.extended	     = nb->extended;
+		x25_subscr.global_facil_mask = nb->global_facil_mask;
+		read_unlock_bh(&x25_neigh_list_lock);
+		rc = copy_to_user(arg, &x25_subscr,
+				  sizeof(x25_subscr)) ? -EFAULT : 0;
+	} else {
+		rc = -EINVAL;
+		if (!(x25_subscr.extended && x25_subscr.extended != 1)) {
+			rc = 0;
+			write_lock_bh(&x25_neigh_list_lock);
+			nb->extended	     = x25_subscr.extended;
+			nb->global_facil_mask = x25_subscr.global_facil_mask;
+			write_unlock_bh(&x25_neigh_list_lock);
+		}
+	}
+	x25_neigh_put(nb);
+out:
+	return rc;
+out_dev_put:
+	dev_put(dev);
+	goto out;
+}
+
+
+/*
+ *	Release all memory associated with X.25 neighbour structures.
+ */
+void __exit x25_link_free(void)
+{
+	struct x25_neigh *nb;
+	struct list_head *entry, *tmp;
+
+	write_lock_bh(&x25_neigh_list_lock);
+
+	list_for_each_safe(entry, tmp, &x25_neigh_list) {
+		struct net_device *dev;
+
+		nb = list_entry(entry, struct x25_neigh, node);
+		dev = nb->dev;
+		__x25_remove_neigh(nb);
+		dev_put(dev);
+	}
+	write_unlock_bh(&x25_neigh_list_lock);
+}
diff --git a/net/x25/x25_out.c b/net/x25/x25_out.c
new file mode 100644
index 000000000..dbc0940bf
--- /dev/null
+++ b/net/x25/x25_out.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine,
+ *	randomly fail to work with new releases, misbehave and/or generally
+ *	screw up. It might even work.
+ *
+ *	This code REQUIRES 2.1.15 or higher
+ *
+ *	History
+ *	X.25 001	Jonathan Naylor	Started coding.
+ *	X.25 002	Jonathan Naylor	New timer architecture.
+ *	2000-09-04	Henner Eisen	Prevented x25_output() skb leakage.
+ *	2000-10-27	Henner Eisen	MSG_DONTWAIT for fragment allocation.
+ *	2000-11-10	Henner Eisen	x25_send_iframe(): re-queued frames
+ *					needed cleaned seq-number fields.
+ */
+
+#include <linux/slab.h>
+#include <linux/socket.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/x25.h>
+
+static int x25_pacsize_to_bytes(unsigned int pacsize)
+{
+	int bytes = 1;
+
+	if (!pacsize)
+		return 128;
+
+	while (pacsize-- > 0)
+		bytes *= 2;
+
+	return bytes;
+}
+
+/*
+ *	This is where all X.25 information frames pass.
+ *
+ *      Returns the amount of user data bytes sent on success
+ *      or a negative error code on failure.
+ */
+int x25_output(struct sock *sk, struct sk_buff *skb)
+{
+	struct sk_buff *skbn;
+	unsigned char header[X25_EXT_MIN_LEN];
+	int err, frontlen, len;
+	int sent=0, noblock = X25_SKB_CB(skb)->flags & MSG_DONTWAIT;
+	struct x25_sock *x25 = x25_sk(sk);
+	int header_len = x25->neighbour->extended ? X25_EXT_MIN_LEN :
+						    X25_STD_MIN_LEN;
+	int max_len = x25_pacsize_to_bytes(x25->facilities.pacsize_out);
+
+	if (skb->len - header_len > max_len) {
+		/* Save a copy of the Header */
+		skb_copy_from_linear_data(skb, header, header_len);
+		skb_pull(skb, header_len);
+
+		frontlen = skb_headroom(skb);
+
+		while (skb->len > 0) {
+			release_sock(sk);
+			skbn = sock_alloc_send_skb(sk, frontlen + max_len,
+						   noblock, &err);
+			lock_sock(sk);
+			if (!skbn) {
+				if (err == -EWOULDBLOCK && noblock){
+					kfree_skb(skb);
+					return sent;
+				}
+				SOCK_DEBUG(sk, "x25_output: fragment alloc"
+					       " failed, err=%d, %d bytes "
+					       "sent\n", err, sent);
+				return err;
+			}
+
+			skb_reserve(skbn, frontlen);
+
+			len = max_len > skb->len ? skb->len : max_len;
+
+			/* Copy the user data */
+			skb_copy_from_linear_data(skb, skb_put(skbn, len), len);
+			skb_pull(skb, len);
+
+			/* Duplicate the Header */
+			skb_push(skbn, header_len);
+			skb_copy_to_linear_data(skbn, header, header_len);
+
+			if (skb->len > 0) {
+				if (x25->neighbour->extended)
+					skbn->data[3] |= X25_EXT_M_BIT;
+				else
+					skbn->data[2] |= X25_STD_M_BIT;
+			}
+
+			skb_queue_tail(&sk->sk_write_queue, skbn);
+			sent += len;
+		}
+
+		kfree_skb(skb);
+	} else {
+		skb_queue_tail(&sk->sk_write_queue, skb);
+		sent = skb->len - header_len;
+	}
+	return sent;
+}
+
+/*
+ *	This procedure is passed a buffer descriptor for an iframe. It builds
+ *	the rest of the control part of the frame and then writes it out.
+ */
+static void x25_send_iframe(struct sock *sk, struct sk_buff *skb)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	if (!skb)
+		return;
+
+	if (x25->neighbour->extended) {
+		skb->data[2]  = (x25->vs << 1) & 0xFE;
+		skb->data[3] &= X25_EXT_M_BIT;
+		skb->data[3] |= (x25->vr << 1) & 0xFE;
+	} else {
+		skb->data[2] &= X25_STD_M_BIT;
+		skb->data[2] |= (x25->vs << 1) & 0x0E;
+		skb->data[2] |= (x25->vr << 5) & 0xE0;
+	}
+
+	x25_transmit_link(skb, x25->neighbour);
+}
+
+void x25_kick(struct sock *sk)
+{
+	struct sk_buff *skb, *skbn;
+	unsigned short start, end;
+	int modulus;
+	struct x25_sock *x25 = x25_sk(sk);
+
+	if (x25->state != X25_STATE_3)
+		return;
+
+	/*
+	 *	Transmit interrupt data.
+	 */
+	if (skb_peek(&x25->interrupt_out_queue) != NULL &&
+		!test_and_set_bit(X25_INTERRUPT_FLAG, &x25->flags)) {
+
+		skb = skb_dequeue(&x25->interrupt_out_queue);
+		x25_transmit_link(skb, x25->neighbour);
+	}
+
+	if (x25->condition & X25_COND_PEER_RX_BUSY)
+		return;
+
+	if (!skb_peek(&sk->sk_write_queue))
+		return;
+
+	modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
+
+	start   = skb_peek(&x25->ack_queue) ? x25->vs : x25->va;
+	end     = (x25->va + x25->facilities.winsize_out) % modulus;
+
+	if (start == end)
+		return;
+
+	x25->vs = start;
+
+	/*
+	 * Transmit data until either we're out of data to send or
+	 * the window is full.
+	 */
+
+	skb = skb_dequeue(&sk->sk_write_queue);
+
+	do {
+		if ((skbn = skb_clone(skb, GFP_ATOMIC)) == NULL) {
+			skb_queue_head(&sk->sk_write_queue, skb);
+			break;
+		}
+
+		skb_set_owner_w(skbn, sk);
+
+		/*
+		 * Transmit the frame copy.
+		 */
+		x25_send_iframe(sk, skbn);
+
+		x25->vs = (x25->vs + 1) % modulus;
+
+		/*
+		 * Requeue the original data frame.
+		 */
+		skb_queue_tail(&x25->ack_queue, skb);
+
+	} while (x25->vs != end &&
+		 (skb = skb_dequeue(&sk->sk_write_queue)) != NULL);
+
+	x25->vl         = x25->vr;
+	x25->condition &= ~X25_COND_ACK_PENDING;
+
+	x25_stop_timer(sk);
+}
+
+/*
+ * The following routines are taken from page 170 of the 7th ARRL Computer
+ * Networking Conference paper, as is the whole state machine.
+ */
+
+void x25_enquiry_response(struct sock *sk)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	if (x25->condition & X25_COND_OWN_RX_BUSY)
+		x25_write_internal(sk, X25_RNR);
+	else
+		x25_write_internal(sk, X25_RR);
+
+	x25->vl         = x25->vr;
+	x25->condition &= ~X25_COND_ACK_PENDING;
+
+	x25_stop_timer(sk);
+}
diff --git a/net/x25/x25_proc.c b/net/x25/x25_proc.c
new file mode 100644
index 000000000..0412814a2
--- /dev/null
+++ b/net/x25/x25_proc.c
@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine,
+ *	randomly fail to work with new releases, misbehave and/or generally
+ *	screw up. It might even work.
+ *
+ *	This code REQUIRES 2.4 with seq_file support
+ *
+ *	History
+ *	2002/10/06	Arnaldo Carvalho de Melo  seq_file support
+ */
+
+#include <linux/init.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/export.h>
+#include <net/net_namespace.h>
+#include <net/sock.h>
+#include <net/x25.h>
+
+#ifdef CONFIG_PROC_FS
+
+static void *x25_seq_route_start(struct seq_file *seq, loff_t *pos)
+	__acquires(x25_route_list_lock)
+{
+	read_lock_bh(&x25_route_list_lock);
+	return seq_list_start_head(&x25_route_list, *pos);
+}
+
+static void *x25_seq_route_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	return seq_list_next(v, &x25_route_list, pos);
+}
+
+static void x25_seq_route_stop(struct seq_file *seq, void *v)
+	__releases(x25_route_list_lock)
+{
+	read_unlock_bh(&x25_route_list_lock);
+}
+
+static int x25_seq_route_show(struct seq_file *seq, void *v)
+{
+	struct x25_route *rt = list_entry(v, struct x25_route, node);
+
+	if (v == &x25_route_list) {
+		seq_puts(seq, "Address          Digits  Device\n");
+		goto out;
+	}
+
+	rt = v;
+	seq_printf(seq, "%-15s  %-6d  %-5s\n",
+		   rt->address.x25_addr, rt->sigdigits,
+		   rt->dev ? rt->dev->name : "???");
+out:
+	return 0;
+}
+
+static void *x25_seq_socket_start(struct seq_file *seq, loff_t *pos)
+	__acquires(x25_list_lock)
+{
+	read_lock_bh(&x25_list_lock);
+	return seq_hlist_start_head(&x25_list, *pos);
+}
+
+static void *x25_seq_socket_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	return seq_hlist_next(v, &x25_list, pos);
+}
+
+static void x25_seq_socket_stop(struct seq_file *seq, void *v)
+	__releases(x25_list_lock)
+{
+	read_unlock_bh(&x25_list_lock);
+}
+
+static int x25_seq_socket_show(struct seq_file *seq, void *v)
+{
+	struct sock *s;
+	struct x25_sock *x25;
+	const char *devname;
+
+	if (v == SEQ_START_TOKEN) {
+		seq_printf(seq, "dest_addr  src_addr   dev   lci st vs vr "
+				"va   t  t2 t21 t22 t23 Snd-Q Rcv-Q inode\n");
+		goto out;
+	}
+
+	s = sk_entry(v);
+	x25 = x25_sk(s);
+
+	if (!x25->neighbour || !x25->neighbour->dev)
+		devname = "???";
+	else
+		devname = x25->neighbour->dev->name;
+
+	seq_printf(seq, "%-10s %-10s %-5s %3.3X  %d  %d  %d  %d %3lu %3lu "
+			"%3lu %3lu %3lu %5d %5d %ld\n",
+		   !x25->dest_addr.x25_addr[0] ? "*" : x25->dest_addr.x25_addr,
+		   !x25->source_addr.x25_addr[0] ? "*" : x25->source_addr.x25_addr,
+		   devname, x25->lci & 0x0FFF, x25->state, x25->vs, x25->vr,
+		   x25->va, x25_display_timer(s) / HZ, x25->t2  / HZ,
+		   x25->t21 / HZ, x25->t22 / HZ, x25->t23 / HZ,
+		   sk_wmem_alloc_get(s),
+		   sk_rmem_alloc_get(s),
+		   s->sk_socket ? SOCK_INODE(s->sk_socket)->i_ino : 0L);
+out:
+	return 0;
+}
+
+static void *x25_seq_forward_start(struct seq_file *seq, loff_t *pos)
+	__acquires(x25_forward_list_lock)
+{
+	read_lock_bh(&x25_forward_list_lock);
+	return seq_list_start_head(&x25_forward_list, *pos);
+}
+
+static void *x25_seq_forward_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	return seq_list_next(v, &x25_forward_list, pos);
+}
+
+static void x25_seq_forward_stop(struct seq_file *seq, void *v)
+	__releases(x25_forward_list_lock)
+{
+	read_unlock_bh(&x25_forward_list_lock);
+}
+
+static int x25_seq_forward_show(struct seq_file *seq, void *v)
+{
+	struct x25_forward *f = list_entry(v, struct x25_forward, node);
+
+	if (v == &x25_forward_list) {
+		seq_printf(seq, "lci dev1       dev2\n");
+		goto out;
+	}
+
+	f = v;
+
+	seq_printf(seq, "%d %-10s %-10s\n",
+			f->lci, f->dev1->name, f->dev2->name);
+out:
+	return 0;
+}
+
+static const struct seq_operations x25_seq_route_ops = {
+	.start  = x25_seq_route_start,
+	.next   = x25_seq_route_next,
+	.stop   = x25_seq_route_stop,
+	.show   = x25_seq_route_show,
+};
+
+static const struct seq_operations x25_seq_socket_ops = {
+	.start  = x25_seq_socket_start,
+	.next   = x25_seq_socket_next,
+	.stop   = x25_seq_socket_stop,
+	.show   = x25_seq_socket_show,
+};
+
+static const struct seq_operations x25_seq_forward_ops = {
+	.start  = x25_seq_forward_start,
+	.next   = x25_seq_forward_next,
+	.stop   = x25_seq_forward_stop,
+	.show   = x25_seq_forward_show,
+};
+
+int __init x25_proc_init(void)
+{
+	if (!proc_mkdir("x25", init_net.proc_net))
+		return -ENOMEM;
+
+	if (!proc_create_seq("x25/route", 0444, init_net.proc_net,
+			 &x25_seq_route_ops))
+		goto out;
+
+	if (!proc_create_seq("x25/socket", 0444, init_net.proc_net,
+			 &x25_seq_socket_ops))
+		goto out;
+
+	if (!proc_create_seq("x25/forward", 0444, init_net.proc_net,
+			 &x25_seq_forward_ops))
+		goto out;
+	return 0;
+
+out:
+	remove_proc_subtree("x25", init_net.proc_net);
+	return -ENOMEM;
+}
+
+void __exit x25_proc_exit(void)
+{
+	remove_proc_subtree("x25", init_net.proc_net);
+}
+
+#else /* CONFIG_PROC_FS */
+
+int __init x25_proc_init(void)
+{
+	return 0;
+}
+
+void __exit x25_proc_exit(void)
+{
+}
+#endif /* CONFIG_PROC_FS */
diff --git a/net/x25/x25_route.c b/net/x25/x25_route.c
new file mode 100644
index 000000000..647f325ed
--- /dev/null
+++ b/net/x25/x25_route.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine,
+ *	randomly fail to work with new releases, misbehave and/or generally
+ *	screw up. It might even work.
+ *
+ *	This code REQUIRES 2.1.15 or higher
+ *
+ *	History
+ *	X.25 001	Jonathan Naylor	Started coding.
+ */
+
+#include <linux/if_arp.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <net/x25.h>
+
+LIST_HEAD(x25_route_list);
+DEFINE_RWLOCK(x25_route_list_lock);
+
+/*
+ *	Add a new route.
+ */
+static int x25_add_route(struct x25_address *address, unsigned int sigdigits,
+			 struct net_device *dev)
+{
+	struct x25_route *rt;
+	int rc = -EINVAL;
+
+	write_lock_bh(&x25_route_list_lock);
+
+	list_for_each_entry(rt, &x25_route_list, node) {
+		if (!memcmp(&rt->address, address, sigdigits) &&
+		    rt->sigdigits == sigdigits)
+			goto out;
+	}
+
+	rt = kmalloc(sizeof(*rt), GFP_ATOMIC);
+	rc = -ENOMEM;
+	if (!rt)
+		goto out;
+
+	strcpy(rt->address.x25_addr, "000000000000000");
+	memcpy(rt->address.x25_addr, address->x25_addr, sigdigits);
+
+	rt->sigdigits = sigdigits;
+	rt->dev       = dev;
+	refcount_set(&rt->refcnt, 1);
+
+	list_add(&rt->node, &x25_route_list);
+	rc = 0;
+out:
+	write_unlock_bh(&x25_route_list_lock);
+	return rc;
+}
+
+/**
+ * __x25_remove_route - remove route from x25_route_list
+ * @rt: route to remove
+ *
+ * Remove route from x25_route_list. If it was there.
+ * Caller must hold x25_route_list_lock.
+ */
+static void __x25_remove_route(struct x25_route *rt)
+{
+	if (rt->node.next) {
+		list_del(&rt->node);
+		x25_route_put(rt);
+	}
+}
+
+static int x25_del_route(struct x25_address *address, unsigned int sigdigits,
+			 struct net_device *dev)
+{
+	struct x25_route *rt;
+	int rc = -EINVAL;
+
+	write_lock_bh(&x25_route_list_lock);
+
+	list_for_each_entry(rt, &x25_route_list, node) {
+		if (!memcmp(&rt->address, address, sigdigits) &&
+		    rt->sigdigits == sigdigits && rt->dev == dev) {
+			__x25_remove_route(rt);
+			rc = 0;
+			break;
+		}
+	}
+
+	write_unlock_bh(&x25_route_list_lock);
+	return rc;
+}
+
+/*
+ *	A device has been removed, remove its routes.
+ */
+void x25_route_device_down(struct net_device *dev)
+{
+	struct x25_route *rt;
+	struct list_head *entry, *tmp;
+
+	write_lock_bh(&x25_route_list_lock);
+
+	list_for_each_safe(entry, tmp, &x25_route_list) {
+		rt = list_entry(entry, struct x25_route, node);
+
+		if (rt->dev == dev)
+			__x25_remove_route(rt);
+	}
+	write_unlock_bh(&x25_route_list_lock);
+}
+
+/*
+ *	Check that the device given is a valid X.25 interface that is "up".
+ */
+struct net_device *x25_dev_get(char *devname)
+{
+	struct net_device *dev = dev_get_by_name(&init_net, devname);
+
+	if (dev && (!(dev->flags & IFF_UP) || dev->type != ARPHRD_X25)) {
+		dev_put(dev);
+		dev = NULL;
+	}
+
+	return dev;
+}
+
+/**
+ * 	x25_get_route -	Find a route given an X.25 address.
+ *	@addr: - address to find a route for
+ *
+ * 	Find a route given an X.25 address.
+ */
+struct x25_route *x25_get_route(struct x25_address *addr)
+{
+	struct x25_route *rt, *use = NULL;
+
+	read_lock_bh(&x25_route_list_lock);
+
+	list_for_each_entry(rt, &x25_route_list, node) {
+		if (!memcmp(&rt->address, addr, rt->sigdigits)) {
+			if (!use)
+				use = rt;
+			else if (rt->sigdigits > use->sigdigits)
+				use = rt;
+		}
+	}
+
+	if (use)
+		x25_route_hold(use);
+
+	read_unlock_bh(&x25_route_list_lock);
+	return use;
+}
+
+/*
+ *	Handle the ioctls that control the routing functions.
+ */
+int x25_route_ioctl(unsigned int cmd, void __user *arg)
+{
+	struct x25_route_struct rt;
+	struct net_device *dev;
+	int rc = -EINVAL;
+
+	if (cmd != SIOCADDRT && cmd != SIOCDELRT)
+		goto out;
+
+	rc = -EFAULT;
+	if (copy_from_user(&rt, arg, sizeof(rt)))
+		goto out;
+
+	rc = -EINVAL;
+	if (rt.sigdigits > 15)
+		goto out;
+
+	dev = x25_dev_get(rt.device);
+	if (!dev)
+		goto out;
+
+	if (cmd == SIOCADDRT)
+		rc = x25_add_route(&rt.address, rt.sigdigits, dev);
+	else
+		rc = x25_del_route(&rt.address, rt.sigdigits, dev);
+	dev_put(dev);
+out:
+	return rc;
+}
+
+/*
+ *	Release all memory associated with X.25 routing structures.
+ */
+void __exit x25_route_free(void)
+{
+	struct x25_route *rt;
+	struct list_head *entry, *tmp;
+
+	write_lock_bh(&x25_route_list_lock);
+	list_for_each_safe(entry, tmp, &x25_route_list) {
+		rt = list_entry(entry, struct x25_route, node);
+		__x25_remove_route(rt);
+	}
+	write_unlock_bh(&x25_route_list_lock);
+}
diff --git a/net/x25/x25_subr.c b/net/x25/x25_subr.c
new file mode 100644
index 000000000..0285aaa1e
--- /dev/null
+++ b/net/x25/x25_subr.c
@@ -0,0 +1,384 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine,
+ *	randomly fail to work with new releases, misbehave and/or generally
+ *	screw up. It might even work.
+ *
+ *	This code REQUIRES 2.1.15 or higher
+ *
+ *	History
+ *	X.25 001	Jonathan Naylor	  Started coding.
+ *	X.25 002	Jonathan Naylor	  Centralised disconnection processing.
+ *	mar/20/00	Daniela Squassoni Disabling/enabling of facilities
+ *					  negotiation.
+ *	jun/24/01	Arnaldo C. Melo	  use skb_queue_purge, cleanups
+ *	apr/04/15	Shaun Pereira		Fast select with no
+ *						restriction on response.
+ */
+
+#define pr_fmt(fmt) "X25: " fmt
+
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/tcp_states.h>
+#include <net/x25.h>
+
+/*
+ *	This routine purges all of the queues of frames.
+ */
+void x25_clear_queues(struct sock *sk)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	skb_queue_purge(&sk->sk_write_queue);
+	skb_queue_purge(&x25->ack_queue);
+	skb_queue_purge(&x25->interrupt_in_queue);
+	skb_queue_purge(&x25->interrupt_out_queue);
+	skb_queue_purge(&x25->fragment_queue);
+}
+
+
+/*
+ * This routine purges the input queue of those frames that have been
+ * acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
+ * SDL diagram.
+*/
+void x25_frames_acked(struct sock *sk, unsigned short nr)
+{
+	struct sk_buff *skb;
+	struct x25_sock *x25 = x25_sk(sk);
+	int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
+
+	/*
+	 * Remove all the ack-ed frames from the ack queue.
+	 */
+	if (x25->va != nr)
+		while (skb_peek(&x25->ack_queue) && x25->va != nr) {
+			skb = skb_dequeue(&x25->ack_queue);
+			kfree_skb(skb);
+			x25->va = (x25->va + 1) % modulus;
+		}
+}
+
+void x25_requeue_frames(struct sock *sk)
+{
+	struct sk_buff *skb, *skb_prev = NULL;
+
+	/*
+	 * Requeue all the un-ack-ed frames on the output queue to be picked
+	 * up by x25_kick. This arrangement handles the possibility of an empty
+	 * output queue.
+	 */
+	while ((skb = skb_dequeue(&x25_sk(sk)->ack_queue)) != NULL) {
+		if (!skb_prev)
+			skb_queue_head(&sk->sk_write_queue, skb);
+		else
+			skb_append(skb_prev, skb, &sk->sk_write_queue);
+		skb_prev = skb;
+	}
+}
+
+/*
+ *	Validate that the value of nr is between va and vs. Return true or
+ *	false for testing.
+ */
+int x25_validate_nr(struct sock *sk, unsigned short nr)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+	unsigned short vc = x25->va;
+	int modulus = x25->neighbour->extended ? X25_EMODULUS : X25_SMODULUS;
+
+	while (vc != x25->vs) {
+		if (nr == vc)
+			return 1;
+		vc = (vc + 1) % modulus;
+	}
+
+	return nr == x25->vs ? 1 : 0;
+}
+
+/*
+ *  This routine is called when the packet layer internally generates a
+ *  control frame.
+ */
+void x25_write_internal(struct sock *sk, int frametype)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+	struct sk_buff *skb;
+	unsigned char  *dptr;
+	unsigned char  facilities[X25_MAX_FAC_LEN];
+	unsigned char  addresses[1 + X25_ADDR_LEN];
+	unsigned char  lci1, lci2;
+	/*
+	 *	Default safe frame size.
+	 */
+	int len = X25_MAX_L2_LEN + X25_EXT_MIN_LEN;
+
+	/*
+	 *	Adjust frame size.
+	 */
+	switch (frametype) {
+	case X25_CALL_REQUEST:
+		len += 1 + X25_ADDR_LEN + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
+		break;
+	case X25_CALL_ACCEPTED: /* fast sel with no restr on resp */
+		if (x25->facilities.reverse & 0x80) {
+			len += 1 + X25_MAX_FAC_LEN + X25_MAX_CUD_LEN;
+		} else {
+			len += 1 + X25_MAX_FAC_LEN;
+		}
+		break;
+	case X25_CLEAR_REQUEST:
+	case X25_RESET_REQUEST:
+		len += 2;
+		break;
+	case X25_RR:
+	case X25_RNR:
+	case X25_REJ:
+	case X25_CLEAR_CONFIRMATION:
+	case X25_INTERRUPT_CONFIRMATION:
+	case X25_RESET_CONFIRMATION:
+		break;
+	default:
+		pr_err("invalid frame type %02X\n", frametype);
+		return;
+	}
+
+	if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)
+		return;
+
+	/*
+	 *	Space for Ethernet and 802.2 LLC headers.
+	 */
+	skb_reserve(skb, X25_MAX_L2_LEN);
+
+	/*
+	 *	Make space for the GFI and LCI, and fill them in.
+	 */
+	dptr = skb_put(skb, 2);
+
+	lci1 = (x25->lci >> 8) & 0x0F;
+	lci2 = (x25->lci >> 0) & 0xFF;
+
+	if (x25->neighbour->extended) {
+		*dptr++ = lci1 | X25_GFI_EXTSEQ;
+		*dptr++ = lci2;
+	} else {
+		*dptr++ = lci1 | X25_GFI_STDSEQ;
+		*dptr++ = lci2;
+	}
+
+	/*
+	 *	Now fill in the frame type specific information.
+	 */
+	switch (frametype) {
+
+		case X25_CALL_REQUEST:
+			dptr    = skb_put(skb, 1);
+			*dptr++ = X25_CALL_REQUEST;
+			len     = x25_addr_aton(addresses, &x25->dest_addr,
+						&x25->source_addr);
+			skb_put_data(skb, addresses, len);
+			len     = x25_create_facilities(facilities,
+					&x25->facilities,
+					&x25->dte_facilities,
+					x25->neighbour->global_facil_mask);
+			skb_put_data(skb, facilities, len);
+			skb_put_data(skb, x25->calluserdata.cuddata,
+				     x25->calluserdata.cudlength);
+			x25->calluserdata.cudlength = 0;
+			break;
+
+		case X25_CALL_ACCEPTED:
+			dptr    = skb_put(skb, 2);
+			*dptr++ = X25_CALL_ACCEPTED;
+			*dptr++ = 0x00;		/* Address lengths */
+			len     = x25_create_facilities(facilities,
+							&x25->facilities,
+							&x25->dte_facilities,
+							x25->vc_facil_mask);
+			skb_put_data(skb, facilities, len);
+
+			/* fast select with no restriction on response
+				allows call user data. Userland must
+				ensure it is ours and not theirs */
+			if(x25->facilities.reverse & 0x80) {
+				skb_put_data(skb,
+					     x25->calluserdata.cuddata,
+					     x25->calluserdata.cudlength);
+			}
+			x25->calluserdata.cudlength = 0;
+			break;
+
+		case X25_CLEAR_REQUEST:
+			dptr    = skb_put(skb, 3);
+			*dptr++ = frametype;
+			*dptr++ = x25->causediag.cause;
+			*dptr++ = x25->causediag.diagnostic;
+			break;
+
+		case X25_RESET_REQUEST:
+			dptr    = skb_put(skb, 3);
+			*dptr++ = frametype;
+			*dptr++ = 0x00;		/* XXX */
+			*dptr++ = 0x00;		/* XXX */
+			break;
+
+		case X25_RR:
+		case X25_RNR:
+		case X25_REJ:
+			if (x25->neighbour->extended) {
+				dptr     = skb_put(skb, 2);
+				*dptr++  = frametype;
+				*dptr++  = (x25->vr << 1) & 0xFE;
+			} else {
+				dptr     = skb_put(skb, 1);
+				*dptr    = frametype;
+				*dptr++ |= (x25->vr << 5) & 0xE0;
+			}
+			break;
+
+		case X25_CLEAR_CONFIRMATION:
+		case X25_INTERRUPT_CONFIRMATION:
+		case X25_RESET_CONFIRMATION:
+			dptr  = skb_put(skb, 1);
+			*dptr = frametype;
+			break;
+	}
+
+	x25_transmit_link(skb, x25->neighbour);
+}
+
+/*
+ *	Unpick the contents of the passed X.25 Packet Layer frame.
+ */
+int x25_decode(struct sock *sk, struct sk_buff *skb, int *ns, int *nr, int *q,
+	       int *d, int *m)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+	unsigned char *frame;
+
+	if (!pskb_may_pull(skb, X25_STD_MIN_LEN))
+		return X25_ILLEGAL;
+	frame = skb->data;
+
+	*ns = *nr = *q = *d = *m = 0;
+
+	switch (frame[2]) {
+	case X25_CALL_REQUEST:
+	case X25_CALL_ACCEPTED:
+	case X25_CLEAR_REQUEST:
+	case X25_CLEAR_CONFIRMATION:
+	case X25_INTERRUPT:
+	case X25_INTERRUPT_CONFIRMATION:
+	case X25_RESET_REQUEST:
+	case X25_RESET_CONFIRMATION:
+	case X25_RESTART_REQUEST:
+	case X25_RESTART_CONFIRMATION:
+	case X25_REGISTRATION_REQUEST:
+	case X25_REGISTRATION_CONFIRMATION:
+	case X25_DIAGNOSTIC:
+		return frame[2];
+	}
+
+	if (x25->neighbour->extended) {
+		if (frame[2] == X25_RR  ||
+		    frame[2] == X25_RNR ||
+		    frame[2] == X25_REJ) {
+			if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
+				return X25_ILLEGAL;
+			frame = skb->data;
+
+			*nr = (frame[3] >> 1) & 0x7F;
+			return frame[2];
+		}
+	} else {
+		if ((frame[2] & 0x1F) == X25_RR  ||
+		    (frame[2] & 0x1F) == X25_RNR ||
+		    (frame[2] & 0x1F) == X25_REJ) {
+			*nr = (frame[2] >> 5) & 0x07;
+			return frame[2] & 0x1F;
+		}
+	}
+
+	if (x25->neighbour->extended) {
+		if ((frame[2] & 0x01) == X25_DATA) {
+			if (!pskb_may_pull(skb, X25_EXT_MIN_LEN))
+				return X25_ILLEGAL;
+			frame = skb->data;
+
+			*q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
+			*d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
+			*m  = (frame[3] & X25_EXT_M_BIT) == X25_EXT_M_BIT;
+			*nr = (frame[3] >> 1) & 0x7F;
+			*ns = (frame[2] >> 1) & 0x7F;
+			return X25_DATA;
+		}
+	} else {
+		if ((frame[2] & 0x01) == X25_DATA) {
+			*q  = (frame[0] & X25_Q_BIT) == X25_Q_BIT;
+			*d  = (frame[0] & X25_D_BIT) == X25_D_BIT;
+			*m  = (frame[2] & X25_STD_M_BIT) == X25_STD_M_BIT;
+			*nr = (frame[2] >> 5) & 0x07;
+			*ns = (frame[2] >> 1) & 0x07;
+			return X25_DATA;
+		}
+	}
+
+	pr_debug("invalid PLP frame %3ph\n", frame);
+
+	return X25_ILLEGAL;
+}
+
+void x25_disconnect(struct sock *sk, int reason, unsigned char cause,
+		    unsigned char diagnostic)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	x25_clear_queues(sk);
+	x25_stop_timer(sk);
+
+	x25->lci   = 0;
+	x25->state = X25_STATE_0;
+
+	x25->causediag.cause      = cause;
+	x25->causediag.diagnostic = diagnostic;
+
+	sk->sk_state     = TCP_CLOSE;
+	sk->sk_err       = reason;
+	sk->sk_shutdown |= SEND_SHUTDOWN;
+
+	if (!sock_flag(sk, SOCK_DEAD)) {
+		sk->sk_state_change(sk);
+		sock_set_flag(sk, SOCK_DEAD);
+	}
+	if (x25->neighbour) {
+		read_lock_bh(&x25_list_lock);
+		x25_neigh_put(x25->neighbour);
+		x25->neighbour = NULL;
+		read_unlock_bh(&x25_list_lock);
+	}
+}
+
+/*
+ * Clear an own-rx-busy condition and tell the peer about this, provided
+ * that there is a significant amount of free receive buffer space available.
+ */
+void x25_check_rbuf(struct sock *sk)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	if (atomic_read(&sk->sk_rmem_alloc) < (sk->sk_rcvbuf >> 1) &&
+	    (x25->condition & X25_COND_OWN_RX_BUSY)) {
+		x25->condition &= ~X25_COND_OWN_RX_BUSY;
+		x25->condition &= ~X25_COND_ACK_PENDING;
+		x25->vl         = x25->vr;
+		x25_write_internal(sk, X25_RR);
+		x25_stop_timer(sk);
+	}
+}
diff --git a/net/x25/x25_timer.c b/net/x25/x25_timer.c
new file mode 100644
index 000000000..9376365cd
--- /dev/null
+++ b/net/x25/x25_timer.c
@@ -0,0 +1,169 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	X.25 Packet Layer release 002
+ *
+ *	This is ALPHA test software. This code may break your machine,
+ *	randomly fail to work with new releases, misbehave and/or generally
+ *	screw up. It might even work.
+ *
+ *	This code REQUIRES 2.1.15 or higher
+ *
+ *	History
+ *	X.25 001	Jonathan Naylor	Started coding.
+ *	X.25 002	Jonathan Naylor	New timer architecture.
+ *					Centralised disconnection processing.
+ */
+
+#include <linux/errno.h>
+#include <linux/jiffies.h>
+#include <linux/timer.h>
+#include <net/sock.h>
+#include <net/tcp_states.h>
+#include <net/x25.h>
+
+static void x25_heartbeat_expiry(struct timer_list *t);
+static void x25_timer_expiry(struct timer_list *t);
+
+void x25_init_timers(struct sock *sk)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	timer_setup(&x25->timer, x25_timer_expiry, 0);
+
+	/* initialized by sock_init_data */
+	sk->sk_timer.function = x25_heartbeat_expiry;
+}
+
+void x25_start_heartbeat(struct sock *sk)
+{
+	mod_timer(&sk->sk_timer, jiffies + 5 * HZ);
+}
+
+void x25_stop_heartbeat(struct sock *sk)
+{
+	del_timer(&sk->sk_timer);
+}
+
+void x25_start_t2timer(struct sock *sk)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	mod_timer(&x25->timer, jiffies + x25->t2);
+}
+
+void x25_start_t21timer(struct sock *sk)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	mod_timer(&x25->timer, jiffies + x25->t21);
+}
+
+void x25_start_t22timer(struct sock *sk)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	mod_timer(&x25->timer, jiffies + x25->t22);
+}
+
+void x25_start_t23timer(struct sock *sk)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	mod_timer(&x25->timer, jiffies + x25->t23);
+}
+
+void x25_stop_timer(struct sock *sk)
+{
+	del_timer(&x25_sk(sk)->timer);
+}
+
+unsigned long x25_display_timer(struct sock *sk)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	if (!timer_pending(&x25->timer))
+		return 0;
+
+	return x25->timer.expires - jiffies;
+}
+
+static void x25_heartbeat_expiry(struct timer_list *t)
+{
+	struct sock *sk = from_timer(sk, t, sk_timer);
+
+	bh_lock_sock(sk);
+	if (sock_owned_by_user(sk)) /* can currently only occur in state 3 */
+		goto restart_heartbeat;
+
+	switch (x25_sk(sk)->state) {
+
+		case X25_STATE_0:
+			/*
+			 * Magic here: If we listen() and a new link dies
+			 * before it is accepted() it isn't 'dead' so doesn't
+			 * get removed.
+			 */
+			if (sock_flag(sk, SOCK_DESTROY) ||
+			    (sk->sk_state == TCP_LISTEN &&
+			     sock_flag(sk, SOCK_DEAD))) {
+				bh_unlock_sock(sk);
+				x25_destroy_socket_from_timer(sk);
+				return;
+			}
+			break;
+
+		case X25_STATE_3:
+			/*
+			 * Check for the state of the receive buffer.
+			 */
+			x25_check_rbuf(sk);
+			break;
+	}
+restart_heartbeat:
+	x25_start_heartbeat(sk);
+	bh_unlock_sock(sk);
+}
+
+/*
+ *	Timer has expired, it may have been T2, T21, T22, or T23. We can tell
+ *	by the state machine state.
+ */
+static inline void x25_do_timer_expiry(struct sock * sk)
+{
+	struct x25_sock *x25 = x25_sk(sk);
+
+	switch (x25->state) {
+
+		case X25_STATE_3:	/* T2 */
+			if (x25->condition & X25_COND_ACK_PENDING) {
+				x25->condition &= ~X25_COND_ACK_PENDING;
+				x25_enquiry_response(sk);
+			}
+			break;
+
+		case X25_STATE_1:	/* T21 */
+		case X25_STATE_4:	/* T22 */
+			x25_write_internal(sk, X25_CLEAR_REQUEST);
+			x25->state = X25_STATE_2;
+			x25_start_t23timer(sk);
+			break;
+
+		case X25_STATE_2:	/* T23 */
+			x25_disconnect(sk, ETIMEDOUT, 0, 0);
+			break;
+	}
+}
+
+static void x25_timer_expiry(struct timer_list *t)
+{
+	struct x25_sock *x25 = from_timer(x25, t, timer);
+	struct sock *sk = &x25->sk;
+
+	bh_lock_sock(sk);
+	if (sock_owned_by_user(sk)) { /* can currently only occur in state 3 */
+		if (x25_sk(sk)->state == X25_STATE_3)
+			x25_start_t2timer(sk);
+	} else
+		x25_do_timer_expiry(sk);
+	bh_unlock_sock(sk);
+}