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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/net/802/stp.c
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// SPDX-License-Identifier: GPL-2.0-only

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/*

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 *	STP SAP demux

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 *

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 *	Copyright (c) 2008 Patrick McHardy <[email protected]>

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 */

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#include <linux/mutex.h>

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#include <linux/skbuff.h>

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#include <linux/etherdevice.h>

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#include <linux/llc.h>

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#include <linux/slab.h>

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#include <linux/module.h>

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#include <net/llc.h>

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#include <net/llc_pdu.h>

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#include <net/stp.h>

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/* 01:80:c2:00:00:20 - 01:80:c2:00:00:2F */

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#define GARP_ADDR_MIN	0x20

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#define GARP_ADDR_MAX	0x2F

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#define GARP_ADDR_RANGE	(GARP_ADDR_MAX - GARP_ADDR_MIN)

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static const struct stp_proto __rcu *garp_protos[GARP_ADDR_RANGE + 1] __read_mostly;

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static const struct stp_proto __rcu *stp_proto __read_mostly;

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static struct llc_sap *sap __read_mostly;

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static unsigned int sap_registered;

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static DEFINE_MUTEX(stp_proto_mutex);

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/* Called under rcu_read_lock from LLC */

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static int stp_pdu_rcv(struct sk_buff *skb, struct net_device *dev,

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		       struct packet_type *pt, struct net_device *orig_dev)

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{

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	const struct ethhdr *eh = eth_hdr(skb);

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	const struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);

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	const struct stp_proto *proto;

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	if (pdu->ssap != LLC_SAP_BSPAN ||

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	    pdu->dsap != LLC_SAP_BSPAN ||

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	    pdu->ctrl_1 != LLC_PDU_TYPE_U)

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		goto err;

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	if (eh->h_dest[5] >= GARP_ADDR_MIN && eh->h_dest[5] <= GARP_ADDR_MAX) {

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		proto = rcu_dereference(garp_protos[eh->h_dest[5] -

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						    GARP_ADDR_MIN]);

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		if (proto &&

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		    !ether_addr_equal(eh->h_dest, proto->group_address))

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			goto err;

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	} else

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		proto = rcu_dereference(stp_proto);

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	if (!proto)

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		goto err;

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	proto->rcv(proto, skb, dev);

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	return 0;

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err:

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	kfree_skb(skb);

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	return 0;

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}

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int stp_proto_register(const struct stp_proto *proto)

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{

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	int err = 0;

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	mutex_lock(&stp_proto_mutex);

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	if (sap_registered++ == 0) {

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		sap = llc_sap_open(LLC_SAP_BSPAN, stp_pdu_rcv);

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		if (!sap) {

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			err = -ENOMEM;

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			goto out;

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		}

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	}

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	if (is_zero_ether_addr(proto->group_address))

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		rcu_assign_pointer(stp_proto, proto);

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	else

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		rcu_assign_pointer(garp_protos[proto->group_address[5] -

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					       GARP_ADDR_MIN], proto);

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out:

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	mutex_unlock(&stp_proto_mutex);

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	return err;

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}

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EXPORT_SYMBOL_GPL(stp_proto_register);

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void stp_proto_unregister(const struct stp_proto *proto)

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{

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	mutex_lock(&stp_proto_mutex);

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	if (is_zero_ether_addr(proto->group_address))

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		RCU_INIT_POINTER(stp_proto, NULL);

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	else

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		RCU_INIT_POINTER(garp_protos[proto->group_address[5] -

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					       GARP_ADDR_MIN], NULL);

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	synchronize_rcu();

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	if (--sap_registered == 0)

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		llc_sap_put(sap);

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	mutex_unlock(&stp_proto_mutex);

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}

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EXPORT_SYMBOL_GPL(stp_proto_unregister);

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MODULE_DESCRIPTION("SAP demux for IEEE 802.1D Spanning Tree Protocol (STP)");

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MODULE_LICENSE("GPL");

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