text: /*
   *	Handle incoming frames
   *	Linux ethernet bridge
   *
   *	Authors:
   *	Lennert Buytenhek		<buytenh@gnu.org>
   *
   *	$Id: br_input.c,v 1.10 2001/12/24 04:50:20 davem Exp $
   *
   *	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/netdevice.h>
  #include <linux/etherdevice.h>
  #include <linux/netfilter_bridge.h>
  #include "br_private.h"
  
  /* Bridge group multicast address 802.1d (pg 51). */
  const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
  
  static void br_pass_frame_up(struct net_bridge *br, struct sk_buff *skb)
  {
  	struct net_device *indev;
  
  	br->statistics.rx_packets++;
  	br->statistics.rx_bytes += skb->len;
  
  	indev = skb->dev;
  	skb->dev = br->dev;
  
  	NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
  		netif_receive_skb);
  }
  
  /* note: already called with rcu_read_lock (preempt_disabled) */
  int br_handle_frame_finish(struct sk_buff *skb)
  {
  	const unsigned char *dest = eth_hdr(skb)->h_dest;
  	struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
  	struct net_bridge *br;
  	struct net_bridge_fdb_entry *dst;
  	int passedup = 0;
  
  	if (!p || p->state == BR_STATE_DISABLED)
  		goto drop;
  
  	/* insert into forwarding database after filtering to avoid spoofing */
  	br = p->br;
  	br_fdb_update(br, p, eth_hdr(skb)->h_source);
  
  	if (p->state == BR_STATE_LEARNING)
  		goto drop;
  
  	if (br->dev->flags & IFF_PROMISC) {
  		struct sk_buff *skb2;
  
  		skb2 = skb_clone(skb, GFP_ATOMIC);
  		if (skb2 != NULL) {
  			passedup = 1;
  			br_pass_frame_up(br, skb2);
  		}
  	}
  
  	if (is_multicast_ether_addr(dest)) {
  		br->statistics.multicast++;
  		br_flood_forward(br, skb, !passedup);
  		if (!passedup)
  			br_pass_frame_up(br, skb);
  		goto out;
  	}
  
  	dst = __br_fdb_get(br, dest);
  	if (dst != NULL && dst->is_local) {
  		if (!passedup)
  			br_pass_frame_up(br, skb);
  		else
  			kfree_skb(skb);
  		goto out;
  	}
  
  	if (dst != NULL) {
  		br_forward(dst->dst, skb);
  		goto out;
  	}
  
  	br_flood_forward(br, skb, 0);
  
  out:
  	return 0;
  drop:
  	kfree_skb(skb);
  	goto out;
  }
  
  /* note: already called with rcu_read_lock (preempt_disabled) */
  static int br_handle_local_finish(struct sk_buff *skb)
  {
  	struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
  
  	if (p && p->state != BR_STATE_DISABLED)
  		br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
  
  	return 0;	 /* process further */
  }
  
  /* Does address match the link local multicast address.
   * 01:80:c2:00:00:0X
   */
  static inline int is_link_local(const unsigned char *dest)
  {
  	return memcmp(dest, br_group_address, 5) == 0 && (dest[5] & 0xf0) == 0;
  }
  
  /*
   * Called via br_handle_frame_hook.
   * Return 0 if *pskb should be processed furthur
   *	  1 if *pskb is handled
   * note: already called with rcu_read_lock (preempt_disabled)
   */
  int br_handle_frame(struct net_bridge_port *p, struct sk_buff **pskb)
  {
  	struct sk_buff *skb = *pskb;
  	const unsigned char *dest = eth_hdr(skb)->h_dest;
  
  	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
  		goto err;
  
  	if (unlikely(is_link_local(dest))) {
  		skb->pkt_type = PACKET_HOST;
  		return NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
  			       NULL, br_handle_local_finish) != 0;
  	}
  
  	if (p->state == BR_STATE_FORWARDING || p->state == BR_STATE_LEARNING) {
  		if (br_should_route_hook) {
  			if (br_should_route_hook(pskb))
  				return 0;
  			skb = *pskb;
  			dest = eth_hdr(skb)->h_dest;
  		}
  
  		if (!compare_ether_addr(p->br->dev->dev_addr, dest))
  			skb->pkt_type = PACKET_HOST;
  
  		NF_HOOK(PF_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
  			br_handle_frame_finish);
  		return 1;
  	}
  
  err:
  	kfree_skb(skb);
  	return 1;
  }
  