br_input.c 8.15 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>
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#include <linux/neighbour.h>
#include <net/arp.h>
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#include <linux/export.h>
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#include <linux/rculist.h>
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#include "br_private.h"

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/* Hook for brouter */
br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
EXPORT_SYMBOL(br_should_route_hook);

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static int
br_netif_receive_skb(struct net *net, struct sock *sk, struct sk_buff *skb)
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{
	return netif_receive_skb(skb);
}

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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);
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	struct net_bridge_vlan_group *vg;
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	struct pcpu_sw_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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	vg = br_vlan_group_rcu(br);
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	/* Bridge is just like any other port.  Make sure the
	 * packet is allowed except in promisc modue when someone
	 * may be running packet capture.
	 */
	if (!(brdev->flags & IFF_PROMISC) &&
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	    !br_allowed_egress(vg, skb)) {
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		kfree_skb(skb);
		return NET_RX_DROP;
	}

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	indev = skb->dev;
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	skb->dev = brdev;
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	skb = br_handle_vlan(br, vg, skb);
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	if (!skb)
		return NET_RX_DROP;
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	/* update the multicast stats if the packet is IGMP/MLD */
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	br_multicast_count(br, NULL, skb, br_multicast_igmp_type(skb),
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			   BR_MCAST_DIR_TX);
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	return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
		       dev_net(indev), NULL, skb, indev, NULL,
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		       br_netif_receive_skb);
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}

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static void br_do_proxy_arp(struct sk_buff *skb, struct net_bridge *br,
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			    u16 vid, struct net_bridge_port *p)
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{
	struct net_device *dev = br->dev;
	struct neighbour *n;
	struct arphdr *parp;
	u8 *arpptr, *sha;
	__be32 sip, tip;

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	BR_INPUT_SKB_CB(skb)->proxyarp_replied = false;

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	if (dev->flags & IFF_NOARP)
		return;

	if (!pskb_may_pull(skb, arp_hdr_len(dev))) {
		dev->stats.tx_dropped++;
		return;
	}
	parp = arp_hdr(skb);

	if (parp->ar_pro != htons(ETH_P_IP) ||
	    parp->ar_op != htons(ARPOP_REQUEST) ||
	    parp->ar_hln != dev->addr_len ||
	    parp->ar_pln != 4)
		return;

	arpptr = (u8 *)parp + sizeof(struct arphdr);
	sha = arpptr;
	arpptr += dev->addr_len;	/* sha */
	memcpy(&sip, arpptr, sizeof(sip));
	arpptr += sizeof(sip);
	arpptr += dev->addr_len;	/* tha */
	memcpy(&tip, arpptr, sizeof(tip));

	if (ipv4_is_loopback(tip) ||
	    ipv4_is_multicast(tip))
		return;

	n = neigh_lookup(&arp_tbl, &tip, dev);
	if (n) {
		struct net_bridge_fdb_entry *f;

		if (!(n->nud_state & NUD_VALID)) {
			neigh_release(n);
			return;
		}

		f = __br_fdb_get(br, n->ha, vid);
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		if (f && ((p->flags & BR_PROXYARP) ||
			  (f->dst && (f->dst->flags & BR_PROXYARP_WIFI)))) {
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			arp_send(ARPOP_REPLY, ETH_P_ARP, sip, skb->dev, tip,
				 sha, n->ha, sha);
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			BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
		}
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		neigh_release(n);
	}
}

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/* note: already called with rcu_read_lock */
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int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
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{
	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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	bool unicast = true;
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	u16 vid = 0;
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	if (!p || p->state == BR_STATE_DISABLED)
		goto drop;

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	if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid))
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		goto out;
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	/* insert into forwarding database after filtering to avoid spoofing */
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	br = p->br;
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	if (p->flags & BR_LEARNING)
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		br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
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	if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
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	    br_multicast_rcv(br, p, skb, vid))
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		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_ENABLED(CONFIG_INET) && skb->protocol == htons(ETH_P_ARP))
		br_do_proxy_arp(skb, br, vid, p);
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	if (is_broadcast_ether_addr(dest)) {
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		skb2 = skb;
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		unicast = false;
	} else if (is_multicast_ether_addr(dest)) {
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		mdst = br_mdb_get(br, skb, vid);
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		if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
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		    br_multicast_querier_exists(br, eth_hdr(skb))) {
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			if ((mdst && mdst->mglist) ||
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			    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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		unicast = false;
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		br->dev->stats.multicast++;
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	} else if ((dst = __br_fdb_get(br, dest, vid)) &&
			dst->is_local) {
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		skb2 = skb;
		/* Do not forward the packet since it's local. */
		skb = NULL;
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	}

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	if (skb) {
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		if (dst) {
			dst->used = jiffies;
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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, unicast);
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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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EXPORT_SYMBOL_GPL(br_handle_frame_finish);
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static void __br_handle_local_finish(struct sk_buff *skb)
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{
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	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
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	u16 vid = 0;
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	/* check if vlan is allowed, to avoid spoofing */
	if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
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		br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
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}

/* note: already called with rcu_read_lock */
static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
{
	struct net_bridge_port *p = br_port_get_rcu(skb->dev);

	__br_handle_local_finish(skb);
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	BR_INPUT_SKB_CB(skb)->brdev = p->br->dev;
	br_pass_frame_up(skb);
	return 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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rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
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{
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	struct net_bridge_port *p;
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	struct sk_buff *skb = *pskb;
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	const unsigned char *dest = eth_hdr(skb)->h_dest;
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	br_should_route_hook_t *rhook;
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	if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
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		return RX_HANDLER_PASS;
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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)
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		return RX_HANDLER_CONSUMED;
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	p = br_port_get_rcu(skb->dev);
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	if (unlikely(is_link_local_ether_addr(dest))) {
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		u16 fwd_mask = p->br->group_fwd_mask_required;

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		/*
		 * See IEEE 802.1D Table 7-10 Reserved addresses
		 *
		 * Assignment		 		Value
		 * Bridge Group Address		01-80-C2-00-00-00
		 * (MAC Control) 802.3		01-80-C2-00-00-01
		 * (Link Aggregation) 802.3	01-80-C2-00-00-02
		 * 802.1X PAE address		01-80-C2-00-00-03
		 *
		 * 802.1AB LLDP 		01-80-C2-00-00-0E
		 *
		 * Others reserved for future standardization
		 */
		switch (dest[5]) {
		case 0x00:	/* Bridge Group Address */
			/* If STP is turned off,
			   then must forward to keep loop detection */
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			if (p->br->stp_enabled == BR_NO_STP ||
			    fwd_mask & (1u << dest[5]))
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				goto forward;
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			*pskb = skb;
			__br_handle_local_finish(skb);
			return RX_HANDLER_PASS;
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		case 0x01:	/* IEEE MAC (Pause) */
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			goto drop;

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		default:
			/* Allow selective forwarding for most other protocols */
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			fwd_mask |= p->br->group_fwd_mask;
			if (fwd_mask & (1u << dest[5]))
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				goto forward;
		}
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		/* Deliver packet to local host only */
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		NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, dev_net(skb->dev),
			NULL, skb, skb->dev, NULL, br_handle_local_finish);
		return RX_HANDLER_CONSUMED;
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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);
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		if (rhook) {
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			if ((*rhook)(skb)) {
				*pskb = skb;
				return RX_HANDLER_PASS;
			}
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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 (ether_addr_equal(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,
			dev_net(skb->dev), NULL, 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 RX_HANDLER_CONSUMED;
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}