br_forward.c 7.64 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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/* Don't forward packets to originating port or forwarding disabled */
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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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	struct net_bridge_vlan_group *vg;

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	vg = nbp_vlan_group_rcu(p);
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	return ((p->flags & BR_HAIRPIN_MODE) || skb->dev != p->dev) &&
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		br_allowed_egress(vg, skb) && p->state == BR_STATE_FORWARDING &&
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		nbp_switchdev_allowed_egress(p, skb) &&
		!br_skb_isolated(p, skb);
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}

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int br_dev_queue_push_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
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{
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	if (!is_skb_forwardable(skb->dev, skb))
		goto drop;

	skb_push(skb, ETH_HLEN);
	br_drop_fake_rtable(skb);

	if (skb->ip_summed == CHECKSUM_PARTIAL &&
	    (skb->protocol == htons(ETH_P_8021Q) ||
	     skb->protocol == htons(ETH_P_8021AD))) {
		int depth;

		if (!__vlan_get_protocol(skb, skb->protocol, &depth))
			goto drop;

		skb_set_network_header(skb, depth);
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	}

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	dev_queue_xmit(skb);

	return 0;

drop:
	kfree_skb(skb);
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	return 0;
}
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EXPORT_SYMBOL_GPL(br_dev_queue_push_xmit);
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int br_forward_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
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{
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	skb->tstamp = 0;
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	return NF_HOOK(NFPROTO_BRIDGE, NF_BR_POST_ROUTING,
		       net, sk, skb, NULL, skb->dev,
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		       br_dev_queue_push_xmit);
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}
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EXPORT_SYMBOL_GPL(br_forward_finish);
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static void __br_forward(const struct net_bridge_port *to,
			 struct sk_buff *skb, bool local_orig)
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{
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	struct net_bridge_vlan_group *vg;
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	struct net_device *indev;
	struct net *net;
	int br_hook;
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	vg = nbp_vlan_group_rcu(to);
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	skb = br_handle_vlan(to->br, to, vg, skb);
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	if (!skb)
		return;

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	indev = skb->dev;
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	skb->dev = to->dev;
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	if (!local_orig) {
		if (skb_warn_if_lro(skb)) {
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			kfree_skb(skb);
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			return;
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		}
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		br_hook = NF_BR_FORWARD;
		skb_forward_csum(skb);
		net = dev_net(indev);
	} else {
		if (unlikely(netpoll_tx_running(to->br->dev))) {
			if (!is_skb_forwardable(skb->dev, skb)) {
				kfree_skb(skb);
			} else {
				skb_push(skb, ETH_HLEN);
				br_netpoll_send_skb(to, skb);
			}
			return;
		}
		br_hook = NF_BR_LOCAL_OUT;
		net = dev_net(skb->dev);
		indev = NULL;
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	}

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	NF_HOOK(NFPROTO_BRIDGE, br_hook,
		net, NULL, skb, indev, skb->dev,
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		br_forward_finish);
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}

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static int deliver_clone(const struct net_bridge_port *prev,
			 struct sk_buff *skb, bool local_orig)
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{
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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;
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	}

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	__br_forward(prev, skb, local_orig);
	return 0;
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}

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/**
 * br_forward - forward a packet to a specific port
 * @to: destination port
 * @skb: packet being forwarded
 * @local_rcv: packet will be received locally after forwarding
 * @local_orig: packet is locally originated
 *
 * Should be called with rcu_read_lock.
 */
void br_forward(const struct net_bridge_port *to,
		struct sk_buff *skb, bool local_rcv, bool local_orig)
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{
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	if (unlikely(!to))
		goto out;

	/* redirect to backup link if the destination port is down */
	if (rcu_access_pointer(to->backup_port) && !netif_carrier_ok(to->dev)) {
		struct net_bridge_port *backup_port;

		backup_port = rcu_dereference(to->backup_port);
		if (unlikely(!backup_port))
			goto out;
		to = backup_port;
	}

	if (should_deliver(to, skb)) {
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		if (local_rcv)
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			deliver_clone(to, skb, local_orig);
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		else
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			__br_forward(to, skb, local_orig);
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		return;
	}

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out:
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	if (!local_rcv)
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		kfree_skb(skb);
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}
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EXPORT_SYMBOL_GPL(br_forward);
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static struct net_bridge_port *maybe_deliver(
	struct net_bridge_port *prev, struct net_bridge_port *p,
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	struct sk_buff *skb, bool local_orig)
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{
	int err;

	if (!should_deliver(p, skb))
		return prev;

	if (!prev)
		goto out;

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	err = deliver_clone(prev, skb, local_orig);
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	if (err)
		return ERR_PTR(err);

out:
	return p;
}

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/* called under rcu_read_lock */
void br_flood(struct net_bridge *br, struct sk_buff *skb,
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	      enum br_pkt_type pkt_type, bool local_rcv, bool local_orig)
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{
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	u8 igmp_type = br_multicast_igmp_type(skb);
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	struct net_bridge_port *prev = NULL;
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	struct net_bridge_port *p;
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	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, nor
		 * other traffic if flood off, except for traffic we originate
		 */
		switch (pkt_type) {
		case BR_PKT_UNICAST:
			if (!(p->flags & BR_FLOOD))
				continue;
			break;
		case BR_PKT_MULTICAST:
			if (!(p->flags & BR_MCAST_FLOOD) && skb->dev != br->dev)
				continue;
			break;
		case BR_PKT_BROADCAST:
			if (!(p->flags & BR_BCAST_FLOOD) && skb->dev != br->dev)
				continue;
			break;
		}
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		/* Do not flood to ports that enable proxy ARP */
		if (p->flags & BR_PROXYARP)
			continue;
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		if ((p->flags & (BR_PROXYARP_WIFI | BR_NEIGH_SUPPRESS)) &&
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		    BR_INPUT_SKB_CB(skb)->proxyarp_replied)
			continue;
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		prev = maybe_deliver(prev, p, skb, local_orig);
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		if (IS_ERR(prev))
			goto out;
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		if (prev == p)
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			br_multicast_count(p->br, p, skb, igmp_type,
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					   BR_MCAST_DIR_TX);
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	}

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	if (!prev)
		goto out;

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	if (local_rcv)
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		deliver_clone(prev, skb, local_orig);
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	else
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		__br_forward(prev, skb, local_orig);
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	return;
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out:
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	if (!local_rcv)
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		kfree_skb(skb);
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}

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#ifdef CONFIG_BRIDGE_IGMP_SNOOPING
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static void maybe_deliver_addr(struct net_bridge_port *p, struct sk_buff *skb,
			       const unsigned char *addr, bool local_orig)
{
	struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
	const unsigned char *src = eth_hdr(skb)->h_source;

	if (!should_deliver(p, skb))
		return;

	/* Even with hairpin, no soliloquies - prevent breaking IPv6 DAD */
	if (skb->dev == p->dev && ether_addr_equal(src, addr))
		return;

	skb = skb_copy(skb, GFP_ATOMIC);
	if (!skb) {
		dev->stats.tx_dropped++;
		return;
	}

	if (!is_broadcast_ether_addr(addr))
		memcpy(eth_hdr(skb)->h_dest, addr, ETH_ALEN);

	__br_forward(p, skb, local_orig);
}

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/* called with rcu_read_lock */
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void br_multicast_flood(struct net_bridge_mdb_entry *mdst,
			struct sk_buff *skb,
			bool local_rcv, bool local_orig)
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{
	struct net_device *dev = BR_INPUT_SKB_CB(skb)->brdev;
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	u8 igmp_type = br_multicast_igmp_type(skb);
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	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;
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		rport = hlist_entry_safe(rp, struct net_bridge_port, rlist);
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		if ((unsigned long)lport > (unsigned long)rport) {
			port = lport;

			if (port->flags & BR_MULTICAST_TO_UNICAST) {
				maybe_deliver_addr(lport, skb, p->eth_addr,
						   local_orig);
				goto delivered;
			}
		} else {
			port = rport;
		}
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		prev = maybe_deliver(prev, port, skb, local_orig);
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delivered:
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		if (IS_ERR(prev))
			goto out;
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		if (prev == port)
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			br_multicast_count(port->br, port, skb, igmp_type,
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					   BR_MCAST_DIR_TX);
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		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;

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	if (local_rcv)
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		deliver_clone(prev, skb, local_orig);
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	else
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		__br_forward(prev, skb, local_orig);
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	return;

out:
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	if (!local_rcv)
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		kfree_skb(skb);
}
#endif