br_forward.c 3.48 KB
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/*
 *	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/kernel.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
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#include <linux/if_vlan.h>
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#include <linux/netfilter_bridge.h>
#include "br_private.h"

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/* Don't forward packets to originating port or forwarding diasabled */
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static inline int should_deliver(const struct net_bridge_port *p,
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				 const struct sk_buff *skb)
{
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	return (((p->flags & BR_HAIRPIN_MODE) || skb->dev != p->dev) &&
		p->state == BR_STATE_FORWARDING);
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}

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static inline unsigned packet_length(const struct sk_buff *skb)
{
	return skb->len - (skb->protocol == htons(ETH_P_8021Q) ? VLAN_HLEN : 0);
}

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int br_dev_queue_push_xmit(struct sk_buff *skb)
{
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	/* drop mtu oversized packets except gso */
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	if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))
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		kfree_skb(skb);
	else {
		/* ip_refrag calls ip_fragment, doesn't copy the MAC header. */
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		if (nf_bridge_maybe_copy_header(skb))
			kfree_skb(skb);
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		else {
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			skb_push(skb, ETH_HLEN);
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			dev_queue_xmit(skb);
		}
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	}

	return 0;
}

int br_forward_finish(struct sk_buff *skb)
{
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	return NF_HOOK(PF_BRIDGE, NF_BR_POST_ROUTING, skb, NULL, skb->dev,
		       br_dev_queue_push_xmit);
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}

static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
{
	skb->dev = to->dev;
	NF_HOOK(PF_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;

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	if (skb_warn_if_lro(skb)) {
		kfree_skb(skb);
		return;
	}

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	indev = skb->dev;
	skb->dev = to->dev;
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	skb_forward_csum(skb);
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	NF_HOOK(PF_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 (should_deliver(to, skb)) {
		__br_deliver(to, skb);
		return;
	}

	kfree_skb(skb);
}

/* called with rcu_read_lock */
void br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
{
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	if (should_deliver(to, skb)) {
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		__br_forward(to, skb);
		return;
	}

	kfree_skb(skb);
}

/* called under bridge lock */
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static void br_flood(struct net_bridge *br, struct sk_buff *skb,
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		     struct sk_buff *skb0,
		     void (*__packet_hook)(const struct net_bridge_port *p,
					   struct sk_buff *skb))
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{
	struct net_bridge_port *p;
	struct net_bridge_port *prev;
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	struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
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	prev = NULL;

	list_for_each_entry_rcu(p, &br->port_list, list) {
		if (should_deliver(p, skb)) {
			if (prev != NULL) {
				struct sk_buff *skb2;

				if ((skb2 = skb_clone(skb, GFP_ATOMIC)) == NULL) {
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					dev->stats.tx_dropped++;
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					goto out;
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				}

				__packet_hook(prev, skb2);
			}

			prev = p;
		}
	}

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	if (!prev)
		goto out;

	if (skb0) {
		skb = skb_clone(skb, GFP_ATOMIC);
		if (!skb) {
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			dev->stats.tx_dropped++;
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			goto out;
		}
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	}
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	__packet_hook(prev, skb);
	return;
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out:
	if (!skb0)
		kfree_skb(skb);
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}


/* called with rcu_read_lock */
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void br_flood_deliver(struct net_bridge *br, struct sk_buff *skb)
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{
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	br_flood(br, skb, NULL, __br_deliver);
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}

/* called under bridge lock */
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void br_flood_forward(struct net_bridge *br, struct sk_buff *skb,
		      struct sk_buff *skb2)
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{
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	br_flood(br, skb, skb2, __br_forward);
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}