cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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psnap.c (3356B)

      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 *	SNAP data link layer. Derived from 802.2
      4 *
      5 *		Alan Cox <alan@lxorguk.ukuu.org.uk>,
      6 *		from the 802.2 layer by Greg Page.
      7 *		Merged in additions from Greg Page's psnap.c.
      8 */
      9
     10#include <linux/module.h>
     11#include <linux/netdevice.h>
     12#include <linux/skbuff.h>
     13#include <linux/slab.h>
     14#include <net/datalink.h>
     15#include <net/llc.h>
     16#include <net/psnap.h>
     17#include <linux/mm.h>
     18#include <linux/in.h>
     19#include <linux/init.h>
     20#include <linux/rculist.h>
     21
     22static LIST_HEAD(snap_list);
     23static DEFINE_SPINLOCK(snap_lock);
     24static struct llc_sap *snap_sap;
     25
     26/*
     27 *	Find a snap client by matching the 5 bytes.
     28 */
     29static struct datalink_proto *find_snap_client(const unsigned char *desc)
     30{
     31	struct datalink_proto *proto = NULL, *p;
     32
     33	list_for_each_entry_rcu(p, &snap_list, node, lockdep_is_held(&snap_lock)) {
     34		if (!memcmp(p->type, desc, 5)) {
     35			proto = p;
     36			break;
     37		}
     38	}
     39	return proto;
     40}
     41
     42/*
     43 *	A SNAP packet has arrived
     44 */
     45static int snap_rcv(struct sk_buff *skb, struct net_device *dev,
     46		    struct packet_type *pt, struct net_device *orig_dev)
     47{
     48	int rc = 1;
     49	struct datalink_proto *proto;
     50	static struct packet_type snap_packet_type = {
     51		.type = cpu_to_be16(ETH_P_SNAP),
     52	};
     53
     54	if (unlikely(!pskb_may_pull(skb, 5)))
     55		goto drop;
     56
     57	rcu_read_lock();
     58	proto = find_snap_client(skb_transport_header(skb));
     59	if (proto) {
     60		/* Pass the frame on. */
     61		skb->transport_header += 5;
     62		skb_pull_rcsum(skb, 5);
     63		rc = proto->rcvfunc(skb, dev, &snap_packet_type, orig_dev);
     64	}
     65	rcu_read_unlock();
     66
     67	if (unlikely(!proto))
     68		goto drop;
     69
     70out:
     71	return rc;
     72
     73drop:
     74	kfree_skb(skb);
     75	goto out;
     76}
     77
     78/*
     79 *	Put a SNAP header on a frame and pass to 802.2
     80 */
     81static int snap_request(struct datalink_proto *dl,
     82			struct sk_buff *skb, const u8 *dest)
     83{
     84	memcpy(skb_push(skb, 5), dl->type, 5);
     85	llc_build_and_send_ui_pkt(snap_sap, skb, dest, snap_sap->laddr.lsap);
     86	return 0;
     87}
     88
     89/*
     90 *	Set up the SNAP layer
     91 */
     92EXPORT_SYMBOL(register_snap_client);
     93EXPORT_SYMBOL(unregister_snap_client);
     94
     95static const char snap_err_msg[] __initconst =
     96	KERN_CRIT "SNAP - unable to register with 802.2\n";
     97
     98static int __init snap_init(void)
     99{
    100	snap_sap = llc_sap_open(0xAA, snap_rcv);
    101	if (!snap_sap) {
    102		printk(snap_err_msg);
    103		return -EBUSY;
    104	}
    105
    106	return 0;
    107}
    108
    109module_init(snap_init);
    110
    111static void __exit snap_exit(void)
    112{
    113	llc_sap_put(snap_sap);
    114}
    115
    116module_exit(snap_exit);
    117
    118
    119/*
    120 *	Register SNAP clients. We don't yet use this for IP.
    121 */
    122struct datalink_proto *register_snap_client(const unsigned char *desc,
    123					    int (*rcvfunc)(struct sk_buff *,
    124							   struct net_device *,
    125							   struct packet_type *,
    126							   struct net_device *))
    127{
    128	struct datalink_proto *proto = NULL;
    129
    130	spin_lock_bh(&snap_lock);
    131
    132	if (find_snap_client(desc))
    133		goto out;
    134
    135	proto = kmalloc(sizeof(*proto), GFP_ATOMIC);
    136	if (proto) {
    137		memcpy(proto->type, desc, 5);
    138		proto->rcvfunc		= rcvfunc;
    139		proto->header_length	= 5 + 3; /* snap + 802.2 */
    140		proto->request		= snap_request;
    141		list_add_rcu(&proto->node, &snap_list);
    142	}
    143out:
    144	spin_unlock_bh(&snap_lock);
    145
    146	return proto;
    147}
    148
    149/*
    150 *	Unregister SNAP clients. Protocols no longer want to play with us ...
    151 */
    152void unregister_snap_client(struct datalink_proto *proto)
    153{
    154	spin_lock_bh(&snap_lock);
    155	list_del_rcu(&proto->node);
    156	spin_unlock_bh(&snap_lock);
    157
    158	synchronize_net();
    159
    160	kfree(proto);
    161}
    162
    163MODULE_LICENSE("GPL");