br_input.c

/*
 *	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)
{
	const u16 *a = (const u16 *) dest;
	static const u16 *const b = (const u16 *const ) br_group_address;
	static const u16 m = __constant_cpu_to_be16(0xfff0);

	return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
}

/*
 * Called via br_handle_frame_hook.
 * Return NULL if skb is handled
 * note: already called with rcu_read_lock (preempt_disabled)
 */
struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
{
	const unsigned char *dest = eth_hdr(skb)->h_dest;

	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
		goto drop;

	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) ? skb : NULL;
	}

	switch (p->state) {
	case BR_STATE_FORWARDING:

		if (br_should_route_hook) {
			if (br_should_route_hook(&skb))
				return skb;
			dest = eth_hdr(skb)->h_dest;
		}
		/* fall through */
	case BR_STATE_LEARNING:
		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);
		break;
	default:
drop:
		kfree_skb(skb);
	}
	return NULL;
}