v4.19.13 snapshot.
diff --git a/net/802/psnap.c b/net/802/psnap.c
new file mode 100644
index 0000000..db6baf7
--- /dev/null
+++ b/net/802/psnap.c
@@ -0,0 +1,167 @@
+/*
+ * SNAP data link layer. Derived from 802.2
+ *
+ * Alan Cox <alan@lxorguk.ukuu.org.uk>,
+ * from the 802.2 layer by Greg Page.
+ * Merged in additions from Greg Page's psnap.c.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <net/datalink.h>
+#include <net/llc.h>
+#include <net/psnap.h>
+#include <linux/mm.h>
+#include <linux/in.h>
+#include <linux/init.h>
+#include <linux/rculist.h>
+
+static LIST_HEAD(snap_list);
+static DEFINE_SPINLOCK(snap_lock);
+static struct llc_sap *snap_sap;
+
+/*
+ * Find a snap client by matching the 5 bytes.
+ */
+static struct datalink_proto *find_snap_client(const unsigned char *desc)
+{
+ struct datalink_proto *proto = NULL, *p;
+
+ list_for_each_entry_rcu(p, &snap_list, node) {
+ if (!memcmp(p->type, desc, 5)) {
+ proto = p;
+ break;
+ }
+ }
+ return proto;
+}
+
+/*
+ * A SNAP packet has arrived
+ */
+static int snap_rcv(struct sk_buff *skb, struct net_device *dev,
+ struct packet_type *pt, struct net_device *orig_dev)
+{
+ int rc = 1;
+ struct datalink_proto *proto;
+ static struct packet_type snap_packet_type = {
+ .type = cpu_to_be16(ETH_P_SNAP),
+ };
+
+ if (unlikely(!pskb_may_pull(skb, 5)))
+ goto drop;
+
+ rcu_read_lock();
+ proto = find_snap_client(skb_transport_header(skb));
+ if (proto) {
+ /* Pass the frame on. */
+ skb->transport_header += 5;
+ skb_pull_rcsum(skb, 5);
+ rc = proto->rcvfunc(skb, dev, &snap_packet_type, orig_dev);
+ }
+ rcu_read_unlock();
+
+ if (unlikely(!proto))
+ goto drop;
+
+out:
+ return rc;
+
+drop:
+ kfree_skb(skb);
+ goto out;
+}
+
+/*
+ * Put a SNAP header on a frame and pass to 802.2
+ */
+static int snap_request(struct datalink_proto *dl,
+ struct sk_buff *skb, u8 *dest)
+{
+ memcpy(skb_push(skb, 5), dl->type, 5);
+ llc_build_and_send_ui_pkt(snap_sap, skb, dest, snap_sap->laddr.lsap);
+ return 0;
+}
+
+/*
+ * Set up the SNAP layer
+ */
+EXPORT_SYMBOL(register_snap_client);
+EXPORT_SYMBOL(unregister_snap_client);
+
+static const char snap_err_msg[] __initconst =
+ KERN_CRIT "SNAP - unable to register with 802.2\n";
+
+static int __init snap_init(void)
+{
+ snap_sap = llc_sap_open(0xAA, snap_rcv);
+ if (!snap_sap) {
+ printk(snap_err_msg);
+ return -EBUSY;
+ }
+
+ return 0;
+}
+
+module_init(snap_init);
+
+static void __exit snap_exit(void)
+{
+ llc_sap_put(snap_sap);
+}
+
+module_exit(snap_exit);
+
+
+/*
+ * Register SNAP clients. We don't yet use this for IP.
+ */
+struct datalink_proto *register_snap_client(const unsigned char *desc,
+ int (*rcvfunc)(struct sk_buff *,
+ struct net_device *,
+ struct packet_type *,
+ struct net_device *))
+{
+ struct datalink_proto *proto = NULL;
+
+ spin_lock_bh(&snap_lock);
+
+ if (find_snap_client(desc))
+ goto out;
+
+ proto = kmalloc(sizeof(*proto), GFP_ATOMIC);
+ if (proto) {
+ memcpy(proto->type, desc, 5);
+ proto->rcvfunc = rcvfunc;
+ proto->header_length = 5 + 3; /* snap + 802.2 */
+ proto->request = snap_request;
+ list_add_rcu(&proto->node, &snap_list);
+ }
+out:
+ spin_unlock_bh(&snap_lock);
+
+ return proto;
+}
+
+/*
+ * Unregister SNAP clients. Protocols no longer want to play with us ...
+ */
+void unregister_snap_client(struct datalink_proto *proto)
+{
+ spin_lock_bh(&snap_lock);
+ list_del_rcu(&proto->node);
+ spin_unlock_bh(&snap_lock);
+
+ synchronize_net();
+
+ kfree(proto);
+}
+
+MODULE_LICENSE("GPL");