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Commit 1a4ba64d authored by Pablo Neira Ayuso's avatar Pablo Neira Ayuso
Browse files

netfilter: bridge: use rcu hook to resolve br_netfilter dependency 



e5de75bf ("netfilter: bridge: move DNAT helper to br_netfilter") results
in the following link problem:

net/bridge/br_device.c:29: undefined reference to `br_nf_prerouting_finish_bridge`

Moreover it creates a hard dependency between br_netfilter and the
bridge core, which is what we've been trying to avoid so far.

Resolve this problem by using a hook structure so we reduce #ifdef
pollution and keep bridge netfilter specific code under br_netfilter.c
which was the original intention.

Reported-by: default avatarSimon Horman <simon.horman@netronome.com>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent a03a8dbe

net/bridge/br_device.c

+6 −1
Original line number Diff line number Diff line
@@ -25,6 +25,9 @@ 
#define COMMON_FEATURES (NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA | \

			 NETIF_F_GSO_MASK | NETIF_F_HW_CSUM)



const struct nf_br_ops __rcu *nf_br_ops __read_mostly;

EXPORT_SYMBOL_GPL(nf_br_ops);



/* net device transmit always called with BH disabled */

netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)

{
@@ -33,10 +36,12 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev) 
	struct net_bridge_fdb_entry *dst;

	struct net_bridge_mdb_entry *mdst;

	struct pcpu_sw_netstats *brstats = this_cpu_ptr(br->stats);

	const struct nf_br_ops *nf_ops;

	u16 vid = 0;



	rcu_read_lock();

	if (br_nf_prerouting_finish_bridge(skb)) {

	nf_ops = rcu_dereference(nf_br_ops);

	if (nf_ops && nf_ops->br_dev_xmit_hook(skb)) {

		rcu_read_unlock();

		return NETDEV_TX_OK;

	}

net/bridge/br_netfilter.c

+7 −2
Original line number Diff line number Diff line
@@ -914,7 +914,7 @@ static void br_nf_pre_routing_finish_bridge_slow(struct sk_buff *skb) 
	br_handle_frame_finish(skb);

}



int br_nf_prerouting_finish_bridge(struct sk_buff *skb)

static int br_nf_dev_xmit(struct sk_buff *skb)

{

	if (skb->nf_bridge && (skb->nf_bridge->mask & BRNF_BRIDGED_DNAT)) {

		br_nf_pre_routing_finish_bridge_slow(skb);
@@ -922,7 +922,10 @@ int br_nf_prerouting_finish_bridge(struct sk_buff *skb) 
	}

	return 0;

}

EXPORT_SYMBOL_GPL(br_nf_prerouting_finish_bridge);



static const struct nf_br_ops br_ops = {

	.br_dev_xmit_hook =	br_nf_dev_xmit,

};



void br_netfilter_enable(void)

{
@@ -1061,12 +1064,14 @@ static int __init br_netfilter_init(void) 
		return -ENOMEM;

	}

#endif

	RCU_INIT_POINTER(nf_br_ops, &br_ops);

	printk(KERN_NOTICE "Bridge firewalling registered\n");

	return 0;

}



static void __exit br_netfilter_fini(void)

{

	RCU_INIT_POINTER(nf_br_ops, NULL);

	nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));

#ifdef CONFIG_SYSCTL

	unregister_net_sysctl_table(brnf_sysctl_header);

net/bridge/br_private.h

+5 −5
Original line number Diff line number Diff line
@@ -763,17 +763,17 @@ static inline int br_vlan_enabled(struct net_bridge *br) 
}

#endif



struct nf_br_ops {

	int (*br_dev_xmit_hook)(struct sk_buff *skb);

};

extern const struct nf_br_ops __rcu *nf_br_ops;



/* br_netfilter.c */

#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)

int br_nf_prerouting_finish_bridge(struct sk_buff *skb);

int br_nf_core_init(void);

void br_nf_core_fini(void);

void br_netfilter_rtable_init(struct net_bridge *);

#else

static inline int br_nf_prerouting_finish_bridge(struct sk_buff *skb)

{

        return 0;

}

static inline int br_nf_core_init(void) { return 0; }

static inline void br_nf_core_fini(void) {}

#define br_netfilter_rtable_init(x)