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Subject[PATCH 4.4 002/193] net: replace dst_cache ip6_tunnel implementation with the generic one
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paolo Abeni <pabeni@redhat.com>

commit 607f725f6f7d5ec3759fbc16224afb60e2152a5b upstream.

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>
Signed-off-by: Manoj Boopathi Raj <manojboopathi@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/net/ip6_tunnel.h | 15 ----
net/ipv6/Kconfig | 1
net/ipv6/ip6_gre.c | 12 +--
net/ipv6/ip6_tunnel.c | 151 +++++++----------------------------------------
net/ipv6/ip6_vti.c | 2
5 files changed, 35 insertions(+), 146 deletions(-)

--- a/include/net/ip6_tunnel.h
+++ b/include/net/ip6_tunnel.h
@@ -5,6 +5,8 @@
#include <linux/netdevice.h>
#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)

@@ -32,12 +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 */
@@ -45,7 +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;
@@ -65,11 +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,
--- a/net/ipv6/Kconfig
+++ b/net/ipv6/Kconfig
@@ -205,6 +205,7 @@ 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.
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -362,7 +362,7 @@ static void ip6gre_tunnel_uninit(struct
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);
}

@@ -640,7 +640,7 @@ static netdev_tx_t ip6gre_xmit2(struct s
}

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);
@@ -709,7 +709,7 @@ static netdev_tx_t ip6gre_xmit2(struct s
}

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;
@@ -1017,7 +1017,7 @@ static int ip6gre_tnl_change(struct ip6_
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;
}
@@ -1228,7 +1228,7 @@ static void ip6gre_dev_free(struct net_d
{
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);
}
@@ -1266,7 +1266,7 @@ static int ip6gre_tunnel_init_common(str
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;
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -122,97 +122,6 @@ static struct net_device_stats *ip6_get_
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
@@ -331,7 +240,7 @@ static void ip6_dev_free(struct net_devi
{
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);
}
@@ -464,7 +373,7 @@ ip6_tnl_dev_uninit(struct net_device *de
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);
}

@@ -1053,7 +962,6 @@ static int ip6_tnl_xmit2(struct sk_buff
struct ipv6_tel_txoption opt;
struct dst_entry *dst = NULL, *ndst = NULL;
struct net_device *tdev;
- bool use_cache = false;
int mtu;
unsigned int max_headroom = sizeof(struct ipv6hdr);
u8 proto;
@@ -1061,39 +969,28 @@ static int ip6_tnl_xmit2(struct sk_buff

/* NBMA tunnel */
if (ipv6_addr_any(&t->parms.raddr)) {
- if (skb->protocol == htons(ETH_P_IPV6)) {
- struct in6_addr *addr6;
- struct neighbour *neigh;
- int addr_type;
-
- if (!skb_dst(skb))
- goto tx_err_link_failure;
-
- neigh = dst_neigh_lookup(skb_dst(skb),
- &ipv6_hdr(skb)->daddr);
- if (!neigh)
- goto tx_err_link_failure;
+ struct in6_addr *addr6;
+ struct neighbour *neigh;
+ int addr_type;
+
+ if (!skb_dst(skb))
+ goto tx_err_link_failure;

- addr6 = (struct in6_addr *)&neigh->primary_key;
- addr_type = ipv6_addr_type(addr6);
+ neigh = dst_neigh_lookup(skb_dst(skb),
+ &ipv6_hdr(skb)->daddr);
+ if (!neigh)
+ goto tx_err_link_failure;

- if (addr_type == IPV6_ADDR_ANY)
- addr6 = &ipv6_hdr(skb)->daddr;
+ addr6 = (struct in6_addr *)&neigh->primary_key;
+ addr_type = ipv6_addr_type(addr6);

- memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
- neigh_release(neigh);
- }
- } else if (t->parms.proto != 0 && !(t->parms.flags &
- (IP6_TNL_F_USE_ORIG_TCLASS |
- IP6_TNL_F_USE_ORIG_FWMARK))) {
- /* enable the cache only if neither the outer protocol nor the
- * routing decision depends on the current inner header value
- */
- use_cache = true;
- }
+ if (addr_type == IPV6_ADDR_ANY)
+ addr6 = &ipv6_hdr(skb)->daddr;

- if (use_cache)
- dst = ip6_tnl_dst_get(t);
+ memcpy(&fl6->daddr, addr6, sizeof(fl6->daddr));
+ neigh_release(neigh);
+ } else if (!fl6->flowi6_mark)
+ dst = dst_cache_get(&t->dst_cache);

if (!ip6_tnl_xmit_ctl(t, &fl6->saddr, &fl6->daddr))
goto tx_err_link_failure;
@@ -1156,8 +1053,8 @@ static int ip6_tnl_xmit2(struct sk_buff
skb = new_skb;
}

- if (use_cache && ndst)
- ip6_tnl_dst_set(t, ndst);
+ if (!fl6->flowi6_mark && ndst)
+ dst_cache_set_ip6(&t->dst_cache, ndst, &fl6->saddr);
skb_dst_set(skb, dst);

skb->transport_header = skb->network_header;
@@ -1392,7 +1289,7 @@ ip6_tnl_change(struct ip6_tnl *t, const
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;
}
@@ -1663,7 +1560,7 @@ ip6_tnl_dev_init_gen(struct net_device *
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;
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -645,7 +645,7 @@ vti6_tnl_change(struct ip6_tnl *t, const
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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