net 01/06: Add STP demux layer

[Patrick McHardy <kaber@trash.net>]

net: Add STP demux layer

Add small STP demux layer for demuxing STP PDUs based on MAC address.
This is needed to run both GARP and STP in parallel (or even load the
modules) since both use LLC_SAP_BSPAN.

Signed-off-by: Patrick McHardy <kaber@trash.net>

---
commit 6c0be0e52a154f1991c221a6f60c6b9be71a10c8
tree 6dcdf3d929edeae8463c6957e688f1e91ca6cfe5
parent 44d28ab19c64d095314ac66f765d0c747519f4ed
author Patrick McHardy <kaber@trash.net> Thu, 03 Jul 2008 18:05:56 +0200
committer Patrick McHardy <kaber@trash.net> Thu, 03 Jul 2008 18:05:56 +0200

 include/net/stp.h |   14 +++++++
 net/802/Kconfig   |    3 ++
 net/802/Makefile  |    1 +
 net/802/stp.c     |  102 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 net/Kconfig       |    1 +
 5 files changed, 121 insertions(+), 0 deletions(-)

diff --git a/include/net/stp.h b/include/net/stp.h
new file mode 100644
index 0000000..ad447f1
--- /dev/null
+++ b/include/net/stp.h
@@ -0,0 +1,14 @@
+#ifndef _NET_STP_H
+#define _NET_STP_H
+
+struct stp_proto {
+	unsigned char	group_address[ETH_ALEN];
+	void		(*rcv)(const struct stp_proto *, struct sk_buff *,
+			       struct net_device *);
+	void		*data;
+};
+
+extern int stp_proto_register(const struct stp_proto *proto);
+extern void stp_proto_unregister(const struct stp_proto *proto);
+
+#endif /* _NET_STP_H */
diff --git a/net/802/Kconfig b/net/802/Kconfig
new file mode 100644
index 0000000..01cb094
--- /dev/null
+++ b/net/802/Kconfig
@@ -0,0 +1,3 @@
+config STP
+	tristate
+	select LLC
diff --git a/net/802/Makefile b/net/802/Makefile
index 68569ff..c441d89 100644
--- a/net/802/Makefile
+++ b/net/802/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_FDDI)	+=                 fddi.o
 obj-$(CONFIG_HIPPI)	+=                 hippi.o
 obj-$(CONFIG_IPX)	+= p8022.o psnap.o p8023.o
 obj-$(CONFIG_ATALK)	+= p8022.o psnap.o
+obj-$(CONFIG_STP)	+= stp.o
diff --git a/net/802/stp.c b/net/802/stp.c
new file mode 100644
index 0000000..0b7a244
--- /dev/null
+++ b/net/802/stp.c
@@ -0,0 +1,102 @@
+/*
+ *	STP SAP demux
+ *
+ *	Copyright (c) 2008 Patrick McHardy <kaber@trash.net>
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	version 2 as published by the Free Software Foundation.
+ */
+#include <linux/mutex.h>
+#include <linux/skbuff.h>
+#include <linux/etherdevice.h>
+#include <linux/llc.h>
+#include <net/llc.h>
+#include <net/llc_pdu.h>
+#include <net/stp.h>
+
+/* 01:80:c2:00:00:20 - 01:80:c2:00:00:2F */
+#define GARP_ADDR_MIN	0x20
+#define GARP_ADDR_MAX	0x2F
+#define GARP_ADDR_RANGE	(GARP_ADDR_MAX - GARP_ADDR_MIN)
+
+static const struct stp_proto *garp_protos[GARP_ADDR_RANGE + 1] __read_mostly;
+static const struct stp_proto *stp_proto __read_mostly;
+
+static struct llc_sap *sap __read_mostly;
+static unsigned int sap_registered;
+static DEFINE_MUTEX(stp_proto_mutex);
+
+/* Called under rcu_read_lock from LLC */
+static int stp_pdu_rcv(struct sk_buff *skb, struct net_device *dev,
+		       struct packet_type *pt, struct net_device *orig_dev)
+{
+	const struct ethhdr *eh = eth_hdr(skb);
+	const struct llc_pdu_un *pdu = llc_pdu_un_hdr(skb);
+	const struct stp_proto *proto;
+
+	if (pdu->ssap != LLC_SAP_BSPAN ||
+	    pdu->dsap != LLC_SAP_BSPAN ||
+	    pdu->ctrl_1 != LLC_PDU_TYPE_U)
+		goto err;
+
+	if (eh->h_dest[5] >= GARP_ADDR_MIN && eh->h_dest[5] <= GARP_ADDR_MAX) {
+		proto = rcu_dereference(garp_protos[eh->h_dest[5] -
+						    GARP_ADDR_MIN]);
+		if (proto &&
+		    compare_ether_addr(eh->h_dest, proto->group_address))
+			goto err;
+	} else
+		proto = rcu_dereference(stp_proto);
+
+	if (!proto)
+		goto err;
+
+	proto->rcv(proto, skb, dev);
+	return 0;
+
+err:
+	kfree_skb(skb);
+	return 0;
+}
+
+int stp_proto_register(const struct stp_proto *proto)
+{
+	int err = 0;
+
+	mutex_lock(&stp_proto_mutex);
+	if (sap_registered++ == 0) {
+		sap = llc_sap_open(LLC_SAP_BSPAN, stp_pdu_rcv);
+		if (!sap) {
+			err = -ENOMEM;
+			goto out;
+		}
+	}
+	if (is_zero_ether_addr(proto->group_address))
+		rcu_assign_pointer(stp_proto, proto);
+	else
+		rcu_assign_pointer(garp_protos[proto->group_address[5] -
+					       GARP_ADDR_MIN], proto);
+out:
+	mutex_unlock(&stp_proto_mutex);
+	return err;
+}
+EXPORT_SYMBOL_GPL(stp_proto_register);
+
+void stp_proto_unregister(const struct stp_proto *proto)
+{
+	mutex_lock(&stp_proto_mutex);
+	if (is_zero_ether_addr(proto->group_address))
+		rcu_assign_pointer(stp_proto, NULL);
+	else
+		rcu_assign_pointer(garp_protos[proto->group_address[5] -
+					       GARP_ADDR_MIN], NULL);
+	synchronize_rcu();
+
+	if (--sap_registered == 0)
+		llc_sap_put(sap);
+	mutex_unlock(&stp_proto_mutex);
+}
+EXPORT_SYMBOL_GPL(stp_proto_unregister);
+
+MODULE_LICENSE("GPL");
diff --git a/net/Kconfig b/net/Kconfig
index acbf7c6..b986687 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -181,6 +181,7 @@ source "net/dccp/Kconfig"
 source "net/sctp/Kconfig"
 source "net/tipc/Kconfig"
 source "net/atm/Kconfig"
+source "net/802/Kconfig"
 source "net/bridge/Kconfig"
 source "net/8021q/Kconfig"
 source "net/decnet/Kconfig"