br_forward.c 6.52 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.
 */

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#include <linux/err.h>
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#include <linux/slab.h>
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#include <linux/kernel.h>
#include <linux/netdevice.h>
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#include <linux/netpoll.h>
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#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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static int deliver_clone(const struct net_bridge_port *prev,
			 struct sk_buff *skb,
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			 void (*__packet_hook)(const struct net_bridge_port *p,
					       struct sk_buff *skb));

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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) &&
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		br_allowed_egress(p->br, nbp_get_vlan_info(p), skb) &&
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		p->state == BR_STATE_FORWARDING);
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}

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static inline unsigned int packet_length(const struct sk_buff *skb)
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{
	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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	/* ip_fragment doesn't copy the MAC header */
	if (nf_bridge_maybe_copy_header(skb) ||
	    (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))) {
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		kfree_skb(skb);
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	} else {
		skb_push(skb, ETH_HLEN);
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		br_drop_fake_rtable(skb);
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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(NFPROTO_BRIDGE, NF_BR_POST_ROUTING, skb, NULL, skb->dev,
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		       br_dev_queue_push_xmit);
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}

static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
{
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	skb = br_handle_vlan(to->br, nbp_get_vlan_info(to), skb);
	if (!skb)
		return;

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	skb->dev = to->dev;
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	if (unlikely(netpoll_tx_running(to->br->dev))) {
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		if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb))
			kfree_skb(skb);
		else {
			skb_push(skb, ETH_HLEN);
			br_netpoll_send_skb(to, skb);
		}
		return;
	}

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	NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_OUT, skb, NULL, skb->dev,
		br_forward_finish);
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}

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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	skb = br_handle_vlan(to->br, nbp_get_vlan_info(to), skb);
	if (!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(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, indev, skb->dev,
		br_forward_finish);
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}

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

	kfree_skb(skb);
}

/* called with rcu_read_lock */
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void br_forward(const struct net_bridge_port *to, struct sk_buff *skb, struct sk_buff *skb0)
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{
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	if (should_deliver(to, skb)) {
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		if (skb0)
			deliver_clone(to, skb, __br_forward);
		else
			__br_forward(to, skb);
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		return;
	}

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	if (!skb0)
		kfree_skb(skb);
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}

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static int deliver_clone(const struct net_bridge_port *prev,
			 struct sk_buff *skb,
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			 void (*__packet_hook)(const struct net_bridge_port *p,
					       struct sk_buff *skb))
{
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	struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;

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	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;
}

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/* 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,
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					   struct sk_buff *skb),
		     bool unicast)
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{
	struct net_bridge_port *p;
	struct net_bridge_port *prev;

	prev = NULL;

	list_for_each_entry_rcu(p, &br->port_list, list) {
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		/* Do not flood unicast traffic to ports that turn it off */
		if (unicast && !(p->flags & BR_FLOOD))
			continue;
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		prev = maybe_deliver(prev, p, skb, __packet_hook);
		if (IS_ERR(prev))
			goto out;
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	}

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	if (!prev)
		goto out;

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	if (skb0)
		deliver_clone(prev, skb, __packet_hook);
	else
		__packet_hook(prev, skb);
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	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, bool unicast)
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{
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	br_flood(br, skb, NULL, __br_deliver, unicast);
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}

/* called under bridge lock */
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void br_flood_forward(struct net_bridge *br, struct sk_buff *skb,
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		      struct sk_buff *skb2, bool unicast)
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{
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	br_flood(br, skb, skb2, __br_forward, unicast);
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}
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#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);
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	struct net_bridge_port *prev = NULL;
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	struct net_bridge_port_group *p;
	struct hlist_node *rp;

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	rp = rcu_dereference(hlist_first_rcu(&br->router_list));
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	p = mdst ? rcu_dereference(mdst->ports) : NULL;
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	while (p || rp) {
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		struct net_bridge_port *port, *lport, *rport;

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		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)
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			p = rcu_dereference(p->next);
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		if ((unsigned long)rport >= (unsigned long)port)
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			rp = rcu_dereference(hlist_next_rcu(rp));
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	}

	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