Commit 607f725f authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
Browse files

net: replace dst_cache ip6_tunnel implementation with the generic one 



This also fix a potential race into the existing tunnel code, which
could lead to the wrong dst to be permanenty cached:

CPU1:					CPU2:
  <xmit on ip6_tunnel>
  <cache lookup fails>
  dst = ip6_route_output(...)
					<tunnel params are changed via nl>
					dst_cache_reset() // no effect,
							// the cache is empty
  dst_cache_set() // the wrong dst
	// is permanenty stored
	// into the cache

With the new dst implementation the above race is not possible
since the first cache lookup after dst_cache_reset will fail due
to the timestamp check

Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Suggested-and-acked-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 911362c7

include/net/ip6_tunnel.h

+2 −12
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#include <linux/if_tunnel.h>

#include <linux/ip6_tunnel.h>

#include <net/ip_tunnels.h>

#include <net/dst_cache.h>



#define IP6TUNNEL_ERR_TIMEO (30*HZ)
@@ -33,12 +34,6 @@ struct __ip6_tnl_parm { 
	__be32			o_key;

};



struct ip6_tnl_dst {

	seqlock_t lock;

	struct dst_entry __rcu *dst;

	u32 cookie;

};



/* IPv6 tunnel */

struct ip6_tnl {

	struct ip6_tnl __rcu *next;	/* next tunnel in list */
@@ -46,7 +41,7 @@ struct ip6_tnl { 
	struct net *net;	/* netns for packet i/o */

	struct __ip6_tnl_parm parms;	/* tunnel configuration parameters */

	struct flowi fl;	/* flowi template for xmit */

	struct ip6_tnl_dst __percpu *dst_cache;	/* cached dst */

	struct dst_cache dst_cache;	/* cached dst */



	int err_count;

	unsigned long err_time;
@@ -66,11 +61,6 @@ struct ipv6_tlv_tnl_enc_lim { 
	__u8 encap_limit;	/* tunnel encapsulation limit   */

} __packed;



struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t);

int ip6_tnl_dst_init(struct ip6_tnl *t);

void ip6_tnl_dst_destroy(struct ip6_tnl *t);

void ip6_tnl_dst_reset(struct ip6_tnl *t);

void ip6_tnl_dst_set(struct ip6_tnl *t, struct dst_entry *dst);

int ip6_tnl_rcv_ctl(struct ip6_tnl *t, const struct in6_addr *laddr,

		const struct in6_addr *raddr);

int ip6_tnl_xmit_ctl(struct ip6_tnl *t, const struct in6_addr *laddr,

net/ipv6/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -207,6 +207,7 @@ config IPV6_NDISC_NODETYPE 
config IPV6_TUNNEL

	tristate "IPv6: IP-in-IPv6 tunnel (RFC2473)"

	select INET6_TUNNEL

	select DST_CACHE

	---help---

	  Support for IPv6-in-IPv6 and IPv4-in-IPv6 tunnels described in

	  RFC 2473.

net/ipv6/ip6_gre.c

+6 −6
Original line number Diff line number Diff line
@@ -360,7 +360,7 @@ static void ip6gre_tunnel_uninit(struct net_device *dev) 
	struct ip6gre_net *ign = net_generic(t->net, ip6gre_net_id);



	ip6gre_tunnel_unlink(ign, t);

	ip6_tnl_dst_reset(t);

	dst_cache_reset(&t->dst_cache);

	dev_put(dev);

}
@@ -633,7 +633,7 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb, 
	}



	if (!fl6->flowi6_mark)

		dst = ip6_tnl_dst_get(tunnel);

		dst = dst_cache_get(&tunnel->dst_cache);



	if (!dst) {

		dst = ip6_route_output(net, NULL, fl6);
@@ -702,7 +702,7 @@ static netdev_tx_t ip6gre_xmit2(struct sk_buff *skb, 
	}



	if (!fl6->flowi6_mark && ndst)

		ip6_tnl_dst_set(tunnel, ndst);

		dst_cache_set_ip6(&tunnel->dst_cache, ndst, &fl6->saddr);

	skb_dst_set(skb, dst);



	proto = NEXTHDR_GRE;
@@ -1009,7 +1009,7 @@ static int ip6gre_tnl_change(struct ip6_tnl *t, 
	t->parms.o_key = p->o_key;

	t->parms.i_flags = p->i_flags;

	t->parms.o_flags = p->o_flags;

	ip6_tnl_dst_reset(t);

	dst_cache_reset(&t->dst_cache);

	ip6gre_tnl_link_config(t, set_mtu);

	return 0;

}
@@ -1219,7 +1219,7 @@ static void ip6gre_dev_free(struct net_device *dev) 
{

	struct ip6_tnl *t = netdev_priv(dev);



	ip6_tnl_dst_destroy(t);

	dst_cache_destroy(&t->dst_cache);

	free_percpu(dev->tstats);

	free_netdev(dev);

}
@@ -1257,7 +1257,7 @@ static int ip6gre_tunnel_init_common(struct net_device *dev) 
	if (!dev->tstats)

		return -ENOMEM;



	ret = ip6_tnl_dst_init(tunnel);

	ret = dst_cache_init(&tunnel->dst_cache, GFP_KERNEL);

	if (ret) {

		free_percpu(dev->tstats);

		dev->tstats = NULL;

net/ipv6/ip6_tunnel.c

+6 −97
Original line number Diff line number Diff line
@@ -122,97 +122,6 @@ static struct net_device_stats *ip6_get_stats(struct net_device *dev) 
	return &dev->stats;

}



/*

 * Locking : hash tables are protected by RCU and RTNL

 */



static void ip6_tnl_per_cpu_dst_set(struct ip6_tnl_dst *idst,

				    struct dst_entry *dst)

{

	write_seqlock_bh(&idst->lock);

	dst_release(rcu_dereference_protected(

			    idst->dst,

			    lockdep_is_held(&idst->lock.lock)));

	if (dst) {

		dst_hold(dst);

		idst->cookie = rt6_get_cookie((struct rt6_info *)dst);

	} else {

		idst->cookie = 0;

	}

	rcu_assign_pointer(idst->dst, dst);

	write_sequnlock_bh(&idst->lock);

}



struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t)

{

	struct ip6_tnl_dst *idst;

	struct dst_entry *dst;

	unsigned int seq;

	u32 cookie;



	idst = raw_cpu_ptr(t->dst_cache);



	rcu_read_lock();

	do {

		seq = read_seqbegin(&idst->lock);

		dst = rcu_dereference(idst->dst);

		cookie = idst->cookie;

	} while (read_seqretry(&idst->lock, seq));



	if (dst && !atomic_inc_not_zero(&dst->__refcnt))

		dst = NULL;

	rcu_read_unlock();



	if (dst && dst->obsolete && !dst->ops->check(dst, cookie)) {

		ip6_tnl_per_cpu_dst_set(idst, NULL);

		dst_release(dst);

		dst = NULL;

	}

	return dst;

}

EXPORT_SYMBOL_GPL(ip6_tnl_dst_get);



void ip6_tnl_dst_reset(struct ip6_tnl *t)

{

	int i;



	for_each_possible_cpu(i)

		ip6_tnl_per_cpu_dst_set(per_cpu_ptr(t->dst_cache, i), NULL);

}

EXPORT_SYMBOL_GPL(ip6_tnl_dst_reset);



void ip6_tnl_dst_set(struct ip6_tnl *t, struct dst_entry *dst)

{

	ip6_tnl_per_cpu_dst_set(raw_cpu_ptr(t->dst_cache), dst);



}

EXPORT_SYMBOL_GPL(ip6_tnl_dst_set);



void ip6_tnl_dst_destroy(struct ip6_tnl *t)

{

	if (!t->dst_cache)

		return;



	ip6_tnl_dst_reset(t);

	free_percpu(t->dst_cache);

}

EXPORT_SYMBOL_GPL(ip6_tnl_dst_destroy);



int ip6_tnl_dst_init(struct ip6_tnl *t)

{

	int i;



	t->dst_cache = alloc_percpu(struct ip6_tnl_dst);

	if (!t->dst_cache)

		return -ENOMEM;



	for_each_possible_cpu(i)

		seqlock_init(&per_cpu_ptr(t->dst_cache, i)->lock);



	return 0;

}

EXPORT_SYMBOL_GPL(ip6_tnl_dst_init);



/**

 * ip6_tnl_lookup - fetch tunnel matching the end-point addresses

 *   @remote: the address of the tunnel exit-point
@@ -329,7 +238,7 @@ static void ip6_dev_free(struct net_device *dev) 
{

	struct ip6_tnl *t = netdev_priv(dev);



	ip6_tnl_dst_destroy(t);

	dst_cache_destroy(&t->dst_cache);

	free_percpu(dev->tstats);

	free_netdev(dev);

}
@@ -462,7 +371,7 @@ ip6_tnl_dev_uninit(struct net_device *dev) 
		RCU_INIT_POINTER(ip6n->tnls_wc[0], NULL);

	else

		ip6_tnl_unlink(ip6n, t);

	ip6_tnl_dst_reset(t);

	dst_cache_reset(&t->dst_cache);

	dev_put(dev);

}
@@ -1069,7 +978,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb, 
		memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));

		neigh_release(neigh);

	} else if (!fl6->flowi6_mark)

		dst = ip6_tnl_dst_get(t);

		dst = dst_cache_get(&t->dst_cache);



	if (!ip6_tnl_xmit_ctl(t, &fl6->saddr, &fl6->daddr))

		goto tx_err_link_failure;
@@ -1133,7 +1042,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb, 
	}



	if (!fl6->flowi6_mark && ndst)

		ip6_tnl_dst_set(t, ndst);

		dst_cache_set_ip6(&t->dst_cache, ndst, &fl6->saddr);

	skb_dst_set(skb, dst);



	skb->transport_header = skb->network_header;
@@ -1366,7 +1275,7 @@ ip6_tnl_change(struct ip6_tnl *t, const struct __ip6_tnl_parm *p) 
	t->parms.flowinfo = p->flowinfo;

	t->parms.link = p->link;

	t->parms.proto = p->proto;

	ip6_tnl_dst_reset(t);

	dst_cache_reset(&t->dst_cache);

	ip6_tnl_link_config(t);

	return 0;

}
@@ -1637,7 +1546,7 @@ ip6_tnl_dev_init_gen(struct net_device *dev) 
	if (!dev->tstats)

		return -ENOMEM;



	ret = ip6_tnl_dst_init(t);

	ret = dst_cache_init(&t->dst_cache, GFP_KERNEL);

	if (ret) {

		free_percpu(dev->tstats);

		dev->tstats = NULL;

net/ipv6/ip6_vti.c

+1 −1
Original line number Diff line number Diff line
@@ -640,7 +640,7 @@ vti6_tnl_change(struct ip6_tnl *t, const struct __ip6_tnl_parm *p) 
	t->parms.i_key = p->i_key;

	t->parms.o_key = p->o_key;

	t->parms.proto = p->proto;

	ip6_tnl_dst_reset(t);

	dst_cache_reset(&t->dst_cache);

	vti6_link_config(t);

	return 0;

}

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