/*
   *	Spanning tree protocol; BPDU handling
   *	Linux ethernet bridge
   *
   *	Authors:
   *	Lennert Buytenhek		<buytenh@gnu.org>
   *

   *	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/kernel.h>
  #include <linux/netfilter_bridge.h>

  #include <linux/etherdevice.h>
  #include <linux/llc.h>

  #include <linux/slab.h>

  #include <linux/pkt_sched.h>

  #include <net/net_namespace.h>

  #include <net/llc.h>

  #include <net/llc_pdu.h>

  #include <net/stp.h>

  #include <asm/unaligned.h>

  
  #include "br_private.h"
  #include "br_private_stp.h"

  #define STP_HZ		256

  #define LLC_RESERVE sizeof(struct llc_pdu_un)

  static int br_send_bpdu_finish(struct net *net, struct sock *sk,
  			       struct sk_buff *skb)

  {
  	return dev_queue_xmit(skb);
  }

  static void br_send_bpdu(struct net_bridge_port *p,

  			 const unsigned char *data, int length)

  {

  	struct sk_buff *skb;

  	skb = dev_alloc_skb(length+LLC_RESERVE);
  	if (!skb)

  		return;

  	skb->dev = p->dev;

  	skb->protocol = htons(ETH_P_802_2);

  	skb->priority = TC_PRIO_CONTROL;

  
  	skb_reserve(skb, LLC_RESERVE);

  	__skb_put_data(skb, data, length);

  
  	llc_pdu_header_init(skb, LLC_PDU_TYPE_U, LLC_SAP_BSPAN,
  			    LLC_SAP_BSPAN, LLC_PDU_CMD);
  	llc_pdu_init_as_ui_cmd(skb);
  
  	llc_mac_hdr_init(skb, p->dev->dev_addr, p->br->group_addr);

  	skb_reset_mac_header(skb);

  	NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_OUT,
  		dev_net(p->dev), NULL, skb, NULL, skb->dev,

  		br_send_bpdu_finish);

  }

  static inline void br_set_ticks(unsigned char *dest, int j)

  {

  	unsigned long ticks = (STP_HZ * j)/ HZ;

  	put_unaligned_be16(ticks, dest);

  }

  static inline int br_get_ticks(const unsigned char *src)

  {

  	unsigned long ticks = get_unaligned_be16(src);

  	return DIV_ROUND_UP(ticks * HZ, STP_HZ);

  }
  
  /* called under bridge lock */
  void br_send_config_bpdu(struct net_bridge_port *p, struct br_config_bpdu *bpdu)
  {

  	unsigned char buf[35];

  	if (p->br->stp_enabled != BR_KERNEL_STP)
  		return;

  	buf[0] = 0;
  	buf[1] = 0;
  	buf[2] = 0;
  	buf[3] = BPDU_TYPE_CONFIG;
  	buf[4] = (bpdu->topology_change ? 0x01 : 0) |

  		(bpdu->topology_change_ack ? 0x80 : 0);

  	buf[5] = bpdu->root.prio[0];
  	buf[6] = bpdu->root.prio[1];
  	buf[7] = bpdu->root.addr[0];
  	buf[8] = bpdu->root.addr[1];
  	buf[9] = bpdu->root.addr[2];
  	buf[10] = bpdu->root.addr[3];
  	buf[11] = bpdu->root.addr[4];
  	buf[12] = bpdu->root.addr[5];
  	buf[13] = (bpdu->root_path_cost >> 24) & 0xFF;
  	buf[14] = (bpdu->root_path_cost >> 16) & 0xFF;
  	buf[15] = (bpdu->root_path_cost >> 8) & 0xFF;
  	buf[16] = bpdu->root_path_cost & 0xFF;
  	buf[17] = bpdu->bridge_id.prio[0];
  	buf[18] = bpdu->bridge_id.prio[1];
  	buf[19] = bpdu->bridge_id.addr[0];
  	buf[20] = bpdu->bridge_id.addr[1];
  	buf[21] = bpdu->bridge_id.addr[2];
  	buf[22] = bpdu->bridge_id.addr[3];
  	buf[23] = bpdu->bridge_id.addr[4];
  	buf[24] = bpdu->bridge_id.addr[5];
  	buf[25] = (bpdu->port_id >> 8) & 0xFF;
  	buf[26] = bpdu->port_id & 0xFF;
  
  	br_set_ticks(buf+27, bpdu->message_age);
  	br_set_ticks(buf+29, bpdu->max_age);
  	br_set_ticks(buf+31, bpdu->hello_time);
  	br_set_ticks(buf+33, bpdu->forward_delay);
  
  	br_send_bpdu(p, buf, 35);

  }
  
  /* called under bridge lock */
  void br_send_tcn_bpdu(struct net_bridge_port *p)
  {

  	unsigned char buf[4];

  	if (p->br->stp_enabled != BR_KERNEL_STP)
  		return;

  	buf[0] = 0;
  	buf[1] = 0;
  	buf[2] = 0;
  	buf[3] = BPDU_TYPE_TCN;

  	br_send_bpdu(p, buf, 4);

  }

  /*
   * Called from llc.
   *

   * NO locks, but rcu_read_lock

   */

  void br_stp_rcv(const struct stp_proto *proto, struct sk_buff *skb,
  		struct net_device *dev)

  {

  	const unsigned char *dest = eth_hdr(skb)->h_dest;

  	struct net_bridge_port *p;

  	struct net_bridge *br;

  	const unsigned char *buf;

  	if (!pskb_may_pull(skb, 4))
  		goto err;
  
  	/* compare of protocol id and version */
  	buf = skb->data;
  	if (buf[0] != 0 || buf[1] != 0 || buf[2] != 0)
  		goto err;

  	p = br_port_get_check_rcu(dev);

  	if (!p)
  		goto err;

  	br = p->br;
  	spin_lock(&br->lock);

  	if (br->stp_enabled != BR_KERNEL_STP)
  		goto out;
  
  	if (!(br->dev->flags & IFF_UP))
  		goto out;
  
  	if (p->state == BR_STATE_DISABLED)

  		goto out;

  	if (!ether_addr_equal(dest, br->group_addr))

  		goto out;

  	if (p->flags & BR_BPDU_GUARD) {
  		br_notice(br, "BPDU received on blocked port %u(%s)
  ",
  			  (unsigned int) p->port_no, p->dev->name);
  		br_stp_disable_port(p);
  		goto out;
  	}

  	buf = skb_pull(skb, 3);

  	if (buf[0] == BPDU_TYPE_CONFIG) {
  		struct br_config_bpdu bpdu;
  
  		if (!pskb_may_pull(skb, 32))

  			goto out;

  
  		buf = skb->data;
  		bpdu.topology_change = (buf[1] & 0x01) ? 1 : 0;
  		bpdu.topology_change_ack = (buf[1] & 0x80) ? 1 : 0;
  
  		bpdu.root.prio[0] = buf[2];
  		bpdu.root.prio[1] = buf[3];
  		bpdu.root.addr[0] = buf[4];
  		bpdu.root.addr[1] = buf[5];
  		bpdu.root.addr[2] = buf[6];
  		bpdu.root.addr[3] = buf[7];
  		bpdu.root.addr[4] = buf[8];
  		bpdu.root.addr[5] = buf[9];
  		bpdu.root_path_cost =
  			(buf[10] << 24) |
  			(buf[11] << 16) |
  			(buf[12] << 8) |
  			buf[13];
  		bpdu.bridge_id.prio[0] = buf[14];
  		bpdu.bridge_id.prio[1] = buf[15];
  		bpdu.bridge_id.addr[0] = buf[16];
  		bpdu.bridge_id.addr[1] = buf[17];
  		bpdu.bridge_id.addr[2] = buf[18];
  		bpdu.bridge_id.addr[3] = buf[19];
  		bpdu.bridge_id.addr[4] = buf[20];
  		bpdu.bridge_id.addr[5] = buf[21];
  		bpdu.port_id = (buf[22] << 8) | buf[23];
  
  		bpdu.message_age = br_get_ticks(buf+24);
  		bpdu.max_age = br_get_ticks(buf+26);
  		bpdu.hello_time = br_get_ticks(buf+28);
  		bpdu.forward_delay = br_get_ticks(buf+30);

  		if (bpdu.message_age > bpdu.max_age) {
  			if (net_ratelimit())
  				br_notice(p->br,
  					  "port %u config from %pM"
  					  " (message_age %ul > max_age %ul)
  ",
  					  p->port_no,
  					  eth_hdr(skb)->h_source,
  					  bpdu.message_age, bpdu.max_age);
  			goto out;
  		}

  		br_received_config_bpdu(p, &bpdu);

  	} else if (buf[0] == BPDU_TYPE_TCN) {

  		br_received_tcn_bpdu(p);
  	}
   out:

  	spin_unlock(&br->lock);

   err:
  	kfree_skb(skb);

  }