text: /*
   *	Forwarding decision
   *	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/err.h>
  #include <linux/slab.h>
  #include <linux/kernel.h>
  #include <linux/netdevice.h>
  #include <linux/netpoll.h>
  #include <linux/skbuff.h>
  #include <linux/if_vlan.h>
  #include <linux/netfilter_bridge.h>
  #include "br_private.h"
  
  static int deliver_clone(const struct net_bridge_port *prev,
  			 struct sk_buff *skb,
  			 void (*__packet_hook)(const struct net_bridge_port *p,
  					       struct sk_buff *skb));
  
  /* Don't forward packets to originating port or forwarding disabled */
  static inline int should_deliver(const struct net_bridge_port *p,
  				 const struct sk_buff *skb)
  {
  	return ((p->flags & BR_HAIRPIN_MODE) || skb->dev != p->dev) &&
  		br_allowed_egress(p->br, nbp_get_vlan_info(p), skb) &&
  		p->state == BR_STATE_FORWARDING;
  }
  
  int br_dev_queue_push_xmit(struct sk_buff *skb)
  {
  	/* ip_fragment doesn't copy the MAC header */
  	if (nf_bridge_maybe_copy_header(skb) ||
  	    !is_skb_forwardable(skb->dev, skb)) {
  		kfree_skb(skb);
  	} else {
  		skb_push(skb, ETH_HLEN);
  		br_drop_fake_rtable(skb);
  		dev_queue_xmit(skb);
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(br_dev_queue_push_xmit);
  
  int br_forward_finish(struct sk_buff *skb)
  {
  	return NF_HOOK(NFPROTO_BRIDGE, NF_BR_POST_ROUTING, skb, NULL, skb->dev,
  		       br_dev_queue_push_xmit);
  
  }
  EXPORT_SYMBOL_GPL(br_forward_finish);
  
  static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
  {
  	skb = br_handle_vlan(to->br, nbp_get_vlan_info(to), skb);
  	if (!skb)
  		return;
  
  	skb->dev = to->dev;
  
  	if (unlikely(netpoll_tx_running(to->br->dev))) {
  		if (!is_skb_forwardable(skb->dev, skb))
  			kfree_skb(skb);
  		else {
  			skb_push(skb, ETH_HLEN);
  			br_netpoll_send_skb(to, skb);
  		}
  		return;
  	}
  
  	NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
  		br_forward_finish);
  }
  
  static void __br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
  {
  	struct net_device *indev;
  
  	if (skb_warn_if_lro(skb)) {
  		kfree_skb(skb);
  		return;
  	}
  
  	skb = br_handle_vlan(to->br, nbp_get_vlan_info(to), skb);
  	if (!skb)
  		return;
  
  	indev = skb->dev;
  	skb->dev = to->dev;
  	skb_forward_csum(skb);
  
  	NF_HOOK(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, indev, skb->dev,
  		br_forward_finish);
  }
  
  /* called with rcu_read_lock */
  void br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
  {
  	if (to && should_deliver(to, skb)) {
  		__br_deliver(to, skb);
  		return;
  	}
  
  	kfree_skb(skb);
  }
  EXPORT_SYMBOL_GPL(br_deliver);
  
  /* called with rcu_read_lock */
  void br_forward(const struct net_bridge_port *to, struct sk_buff *skb, struct sk_buff *skb0)
  {
  	if (should_deliver(to, skb)) {
  		if (skb0)
  			deliver_clone(to, skb, __br_forward);
  		else
  			__br_forward(to, skb);
  		return;
  	}
  
  	if (!skb0)
  		kfree_skb(skb);
  }
  
  static int deliver_clone(const struct net_bridge_port *prev,
  			 struct sk_buff *skb,
  			 void (*__packet_hook)(const struct net_bridge_port *p,
  					       struct sk_buff *skb))
  {
  	struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
  
  	skb = skb_clone(skb, GFP_ATOMIC);
  	if (!skb) {
  		dev->stats.tx_dropped++;
  		return -ENOMEM;
  	}
  
  	__packet_hook(prev, skb);
  	return 0;
  }
  
  static struct net_bridge_port *maybe_deliver(
  	struct net_bridge_port *prev, struct net_bridge_port *p,
  	struct sk_buff *skb,
  	void (*__packet_hook)(const struct net_bridge_port *p,
  			      struct sk_buff *skb))
  {
  	int err;
  
  	if (!should_deliver(p, skb))
  		return prev;
  
  	if (!prev)
  		goto out;
  
  	err = deliver_clone(prev, skb, __packet_hook);
  	if (err)
  		return ERR_PTR(err);
  
  out:
  	return p;
  }
  
  /* called under bridge lock */
  static void br_flood(struct net_bridge *br, struct sk_buff *skb,
  		     struct sk_buff *skb0,
  		     void (*__packet_hook)(const struct net_bridge_port *p,
  					   struct sk_buff *skb),
  		     bool unicast)
  {
  	struct net_bridge_port *p;
  	struct net_bridge_port *prev;
  
  	prev = NULL;
  
  	list_for_each_entry_rcu(p, &br->port_list, list) {
  		/* Do not flood unicast traffic to ports that turn it off */
  		if (unicast && !(p->flags & BR_FLOOD))
  			continue;
  		prev = maybe_deliver(prev, p, skb, __packet_hook);
  		if (IS_ERR(prev))
  			goto out;
  	}
  
  	if (!prev)
  		goto out;
  
  	if (skb0)
  		deliver_clone(prev, skb, __packet_hook);
  	else
  		__packet_hook(prev, skb);
  	return;
  
  out:
  	if (!skb0)
  		kfree_skb(skb);
  }
  
  
  /* called with rcu_read_lock */
  void br_flood_deliver(struct net_bridge *br, struct sk_buff *skb, bool unicast)
  {
  	br_flood(br, skb, NULL, __br_deliver, unicast);
  }
  
  /* called under bridge lock */
  void br_flood_forward(struct net_bridge *br, struct sk_buff *skb,
  		      struct sk_buff *skb2, bool unicast)
  {
  	br_flood(br, skb, skb2, __br_forward, unicast);
  }
  
  #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
  /* called with rcu_read_lock */
  static void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
  			       struct sk_buff *skb, struct sk_buff *skb0,
  			       void (*__packet_hook)(
  					const struct net_bridge_port *p,
  					struct sk_buff *skb))
  {
  	struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
  	struct net_bridge *br = netdev_priv(dev);
  	struct net_bridge_port *prev = NULL;
  	struct net_bridge_port_group *p;
  	struct hlist_node *rp;
  
  	rp = rcu_dereference(hlist_first_rcu(&br->router_list));
  	p = mdst ? rcu_dereference(mdst->ports) : NULL;
  	while (p || rp) {
  		struct net_bridge_port *port, *lport, *rport;
  
  		lport = p ? p->port : NULL;
  		rport = rp ? hlist_entry(rp, struct net_bridge_port, rlist) :
  			     NULL;
  
  		port = (unsigned long)lport > (unsigned long)rport ?
  		       lport : rport;
  
  		prev = maybe_deliver(prev, port, skb, __packet_hook);
  		if (IS_ERR(prev))
  			goto out;
  
  		if ((unsigned long)lport >= (unsigned long)port)
  			p = rcu_dereference(p->next);
  		if ((unsigned long)rport >= (unsigned long)port)
  			rp = rcu_dereference(hlist_next_rcu(rp));
  	}
  
  	if (!prev)
  		goto out;
  
  	if (skb0)
  		deliver_clone(prev, skb, __packet_hook);
  	else
  		__packet_hook(prev, skb);
  	return;
  
  out:
  	if (!skb0)
  		kfree_skb(skb);
  }
  
  /* called with rcu_read_lock */
  void br_multicast_deliver(struct net_bridge_mdb_entry *mdst,
  			  struct sk_buff *skb)
  {
  	br_multicast_flood(mdst, skb, NULL, __br_deliver);
  }
  
  /* called with rcu_read_lock */
  void br_multicast_forward(struct net_bridge_mdb_entry *mdst,
  			  struct sk_buff *skb, struct sk_buff *skb2)
  {
  	br_multicast_flood(mdst, skb, skb2, __br_forward);
  }
  #endif
  