1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *	STP SAP demux
4 *
5 *	Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
6 */
7#include <linux/mutex.h>
8#include <linux/skbuff.h>
9#include <linux/etherdevice.h>
10#include <linux/llc.h>
11#include <linux/slab.h>
12#include <linux/module.h>
13#include <net/llc.h>
14#include <net/llc_pdu.h>
15#include <net/stp.h>
16
17/* 01:80:c2:00:00:20 - 01:80:c2:00:00:2F */
18#define GARP_ADDR_MIN	0x20
19#define GARP_ADDR_MAX	0x2F
20#define GARP_ADDR_RANGE	(GARP_ADDR_MAX - GARP_ADDR_MIN)
21
22static const struct stp_proto __rcu *garp_protos[GARP_ADDR_RANGE + 1] __read_mostly;
23static const struct stp_proto __rcu *stp_proto __read_mostly;
24
25static struct llc_sap *sap __read_mostly;
26static unsigned int sap_registered;
27static DEFINE_MUTEX(stp_proto_mutex);
28
29/* Called under rcu_read_lock from LLC */
30static int stp_pdu_rcv(struct sk_buff *skb, struct net_device *dev,
31		       struct packet_type *pt, struct net_device *orig_dev)
32{
33	const struct ethhdr *eh = eth_hdr(skb);
34	const struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
35	const struct stp_proto *proto;
36
37	if (pdu->ssap != LLC_SAP_BSPAN ||
38	    pdu->dsap != LLC_SAP_BSPAN ||
39	    pdu->ctrl_1 != LLC_PDU_TYPE_U)
40		goto err;
41
42	if (eh->h_dest[5] >= GARP_ADDR_MIN && eh->h_dest[5] <= GARP_ADDR_MAX) {
43		proto = rcu_dereference(garp_protos[eh->h_dest[5] -
44						    GARP_ADDR_MIN]);
45		if (proto &&
46		    !ether_addr_equal(eh->h_dest, proto->group_address))
47			goto err;
48	} else
49		proto = rcu_dereference(stp_proto);
50
51	if (!proto)
52		goto err;
53
54	proto->rcv(proto, skb, dev);
55	return 0;
56
57err:
58	kfree_skb(skb);
59	return 0;
60}
61
62int stp_proto_register(const struct stp_proto *proto)
63{
64	int err = 0;
65
66	mutex_lock(&stp_proto_mutex);
67	if (sap_registered++ == 0) {
68		sap = llc_sap_open(LLC_SAP_BSPAN, stp_pdu_rcv);
69		if (!sap) {
70			err = -ENOMEM;
71			goto out;
72		}
73	}
74	if (is_zero_ether_addr(proto->group_address))
75		rcu_assign_pointer(stp_proto, proto);
76	else
77		rcu_assign_pointer(garp_protos[proto->group_address[5] -
78					       GARP_ADDR_MIN], proto);
79out:
80	mutex_unlock(&stp_proto_mutex);
81	return err;
82}
83EXPORT_SYMBOL_GPL(stp_proto_register);
84
85void stp_proto_unregister(const struct stp_proto *proto)
86{
87	mutex_lock(&stp_proto_mutex);
88	if (is_zero_ether_addr(proto->group_address))
89		RCU_INIT_POINTER(stp_proto, NULL);
90	else
91		RCU_INIT_POINTER(garp_protos[proto->group_address[5] -
92					       GARP_ADDR_MIN], NULL);
93	synchronize_rcu();
94
95	if (--sap_registered == 0)
96		llc_sap_put(sap);
97	mutex_unlock(&stp_proto_mutex);
98}
99EXPORT_SYMBOL_GPL(stp_proto_unregister);
100
101MODULE_DESCRIPTION("SAP demux for IEEE 802.1D Spanning Tree Protocol (STP)");
102MODULE_LICENSE("GPL");
103