br_input.c 4.6 KB
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/*
 *	Handle incoming frames
 *	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/slab.h>
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#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/netfilter_bridge.h>
#include "br_private.h"

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/* Bridge group multicast address 802.1d (pg 51). */
const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
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static int br_pass_frame_up(struct sk_buff *skb)
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{
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	struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
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	struct net_bridge *br = netdev_priv(brdev);
	struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);
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	u64_stats_update_begin(&brstats->syncp);
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	brstats->rx_packets++;
	brstats->rx_bytes += skb->len;
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	u64_stats_update_end(&brstats->syncp);
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	indev = skb->dev;
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	skb->dev = brdev;
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	return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
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		       netif_receive_skb);
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}

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/* note: already called with rcu_read_lock */
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int br_handle_frame_finish(struct sk_buff *skb)
{
	const unsigned char *dest = eth_hdr(skb)->h_dest;
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	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
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	struct net_bridge *br;
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	struct net_bridge_fdb_entry *dst;
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	struct net_bridge_mdb_entry *mdst;
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	struct sk_buff *skb2;
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	if (!p || p->state == BR_STATE_DISABLED)
		goto drop;

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	/* insert into forwarding database after filtering to avoid spoofing */
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	br = p->br;
	br_fdb_update(br, p, eth_hdr(skb)->h_source);
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	if (is_multicast_ether_addr(dest) &&
	    br_multicast_rcv(br, p, skb))
		goto drop;

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	if (p->state == BR_STATE_LEARNING)
		goto drop;
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	BR_INPUT_SKB_CB(skb)->brdev = br->dev;

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	/* The packet skb2 goes to the local host (NULL to skip). */
	skb2 = NULL;
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	if (br->dev->flags & IFF_PROMISC)
		skb2 = skb;

	dst = NULL;
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	if (is_multicast_ether_addr(dest)) {
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		mdst = br_mdb_get(br, skb);
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		if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
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			if ((mdst && !hlist_unhashed(&mdst->mglist)) ||
			    br_multicast_is_router(br))
				skb2 = skb;
			br_multicast_forward(mdst, skb, skb2);
			skb = NULL;
			if (!skb2)
				goto out;
		} else
			skb2 = skb;

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		br->dev->stats.multicast++;
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	} else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
		skb2 = skb;
		/* Do not forward the packet since it's local. */
		skb = NULL;
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	}

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	if (skb) {
		if (dst)
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			br_forward(dst->dst, skb, skb2);
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		else
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			br_flood_forward(br, skb, skb2);
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	}
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	if (skb2)
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		return br_pass_frame_up(skb2);
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out:
	return 0;
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drop:
	kfree_skb(skb);
	goto out;
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}

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/* note: already called with rcu_read_lock */
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static int br_handle_local_finish(struct sk_buff *skb)
{
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	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
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	br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
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	return 0;	 /* process further */
}

/* Does address match the link local multicast address.
 * 01:80:c2:00:00:0X
 */
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static inline int is_link_local(const unsigned char *dest)
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{
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	__be16 *a = (__be16 *)dest;
	static const __be16 *b = (const __be16 *)br_group_address;
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	static const __be16 m = cpu_to_be16(0xfff0);
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	return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
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}

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/*
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 * Return NULL if skb is handled
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 * note: already called with rcu_read_lock
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 */
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struct sk_buff *br_handle_frame(struct sk_buff *skb)
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{
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	struct net_bridge_port *p;
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	const unsigned char *dest = eth_hdr(skb)->h_dest;
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	int (*rhook)(struct sk_buff *skb);
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	if (skb->pkt_type == PACKET_LOOPBACK)
		return skb;

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	if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
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		goto drop;
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	skb = skb_share_check(skb, GFP_ATOMIC);
	if (!skb)
		return NULL;

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	p = br_port_get_rcu(skb->dev);
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	if (unlikely(is_link_local(dest))) {
		/* Pause frames shouldn't be passed up by driver anyway */
		if (skb->protocol == htons(ETH_P_PAUSE))
			goto drop;

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		/* If STP is turned off, then forward */
		if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
			goto forward;

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		if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
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			    NULL, br_handle_local_finish))
			return NULL;	/* frame consumed by filter */
		else
			return skb;	/* continue processing */
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	}
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forward:
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	switch (p->state) {
	case BR_STATE_FORWARDING:
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		rhook = rcu_dereference(br_should_route_hook);
		if (rhook != NULL) {
			if (rhook(skb))
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				return skb;
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			dest = eth_hdr(skb)->h_dest;
		}
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		/* fall through */
	case BR_STATE_LEARNING:
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		if (!compare_ether_addr(p->br->dev->dev_addr, dest))
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			skb->pkt_type = PACKET_HOST;

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		NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
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			br_handle_frame_finish);
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		break;
	default:
drop:
		kfree_skb(skb);
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	}
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	return NULL;
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}