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net: replace dst_cache ip6_tunnel implementation with the generic one
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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: Paolo Abeni <pabeni@redhat.com>
Suggested-and-acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Paolo Abeni authored and David S. Miller committed Feb 17, 2016
1 parent 911362c commit 607f725
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Showing 5 changed files with 16 additions and 116 deletions.
14 changes: 2 additions & 12 deletions include/net/ip6_tunnel.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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)

Expand Down Expand Up @@ -33,20 +34,14 @@ 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 */
struct net_device *dev; /* virtual device associated with tunnel */
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;
Expand All @@ -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,
Expand Down
1 change: 1 addition & 0 deletions net/ipv6/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -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.
Expand Down
12 changes: 6 additions & 6 deletions net/ipv6/ip6_gre.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
}

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
}
Expand Down Expand Up @@ -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);
}
Expand Down Expand Up @@ -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;
Expand Down
103 changes: 6 additions & 97 deletions net/ipv6/ip6_tunnel.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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);
}
Expand Down Expand Up @@ -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);
}

Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
}
Expand Down Expand Up @@ -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;
Expand Down
2 changes: 1 addition & 1 deletion net/ipv6/ip6_vti.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
}
Expand Down

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