4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Paolo Abeni <pab...@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 <pab...@redhat.com>
Suggested-and-acked-by: Hannes Frederic Sowa <han...@stressinduktion.org>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Manoj Boopathi Raj <manojboopa...@google.com>
Signed-off-by: Greg Kroah-Hartman <gre...@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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