[PATCH 4.4 001/193] net: add dst_cache support

[Greg Kroah-Hartman]

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

--

From: Paolo Abeni 

commit 911362c70df5b766c243dc297fadeaced786ffd8 upstream.

This patch add a generic, lockless dst cache implementation.
The need for lock is avoided updating the dst cache fields
only in per cpu scope, and requiring that the cache manipulation
functions are invoked with the local bh disabled.

The refresh_ts and reset_ts fields are used to ensure the cache
consistency in case of cuncurrent cache update (dst_cache_set*) and
reset operation (dst_cache_reset).

Consider the following scenario:

CPU1:   CPU2:
  
  

dst_cache_reset()
  dst_cache_set()

The dst entry set passed to dst_cache_set() should not be used
for later dst cache lookup, because it's obtained using old
configuration values.

Since the refresh_ts is updated only on dst_cache lookup, the
cached value in the above scenario will be discarded on the next
lookup.

Signed-off-by: Paolo Abeni 
Suggested-and-acked-by: Hannes Frederic Sowa 
Signed-off-by: David S. Miller 
Signed-off-by: Manoj Boopathi Raj 
Signed-off-by: Greg Kroah-Hartman 

---
 include/net/dst_cache.h |   97 +++
 net/Kconfig |4 +
 net/core/Makefile   |1 
 net/core/dst_cache.c|  168 
 4 files changed, 270 insertions(+)

--- /dev/null
+++ b/include/net/dst_cache.h
@@ -0,0 +1,97 @@
+#ifndef _NET_DST_CACHE_H
+#define _NET_DST_CACHE_H
+
+#include 
+#include 
+#if IS_ENABLED(CONFIG_IPV6)
+#include 
+#endif
+
+struct dst_cache {
+   struct dst_cache_pcpu __percpu *cache;
+   unsigned long reset_ts;
+};
+
+/**
+ * dst_cache_get - perform cache lookup
+ * @dst_cache: the cache
+ *
+ * The caller should use dst_cache_get_ip4() if it need to retrieve the
+ * source address to be used when xmitting to the cached dst.
+ * local BH must be disabled.
+ */
+struct dst_entry *dst_cache_get(struct dst_cache *dst_cache);
+
+/**
+ * dst_cache_get_ip4 - perform cache lookup and fetch ipv4 source address
+ * @dst_cache: the cache
+ * @saddr: return value for the retrieved source address
+ *
+ * local BH must be disabled.
+ */
+struct rtable *dst_cache_get_ip4(struct dst_cache *dst_cache, __be32 *saddr);
+
+/**
+ * dst_cache_set_ip4 - store the ipv4 dst into the cache
+ * @dst_cache: the cache
+ * @dst: the entry to be cached
+ * @saddr: the source address to be stored inside the cache
+ *
+ * local BH must be disabled.
+ */
+void dst_cache_set_ip4(struct dst_cache *dst_cache, struct dst_entry *dst,
+  __be32 saddr);
+
+#if IS_ENABLED(CONFIG_IPV6)
+
+/**
+ * dst_cache_set_ip6 - store the ipv6 dst into the cache
+ * @dst_cache: the cache
+ * @dst: the entry to be cached
+ * @saddr: the source address to be stored inside the cache
+ *
+ * local BH must be disabled.
+ */
+void dst_cache_set_ip6(struct dst_cache *dst_cache, struct dst_entry *dst,
+  const struct in6_addr *addr);
+
+/**
+ * dst_cache_get_ip6 - perform cache lookup and fetch ipv6 source address
+ * @dst_cache: the cache
+ * @saddr: return value for the retrieved source address
+ *
+ * local BH must be disabled.
+ */
+struct dst_entry *dst_cache_get_ip6(struct dst_cache *dst_cache,
+   struct in6_addr *saddr);
+#endif
+
+/**
+ * dst_cache_reset - invalidate the cache contents
+ * @dst_cache: the cache
+ *
+ * This do not free the cached dst to avoid races and contentions.
+ * the dst will be freed on later cache lookup.
+ */
+static inline void dst_cache_reset(struct dst_cache *dst_cache)
+{
+   dst_cache->reset_ts = jiffies;
+}
+
+/**
+ * dst_cache_init - initialize the cache, allocating the required storage
+ * @dst_cache: the cache
+ * @gfp: allocation flags
+ */
+int dst_cache_init(struct dst_cache *dst_cache, gfp_t gfp);
+
+/**
+ * dst_cache_destroy - empty the cache and free the allocated storage
+ * @dst_cache: the cache
+ *
+ * No synchronization is enforced: it must be called only when the cache
+ * is unsed.
+ */
+void dst_cache_destroy(struct dst_cache *dst_cache);
+
+#endif
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -383,6 +383,10 @@ config LWTUNNEL
  weight tunnel endpoint. Tunnel encapsulation parameters are stored
  with light weight tunnel state associated with fib routes.
 
+config DST_CACHE
+   bool "dst cache"
+   default n
+
 endif   # if NET
 
 # Used by archs to tell that they support BPF_JIT
--- a/net/core/Makefile
+++ b/net/core/Makefile
@@ -24,3 +24,4 @@ obj-$(CONFIG_NET_PTP_CLASSIFY) += ptp_cl
 

[PATCH 4.4 001/193] net: add dst_cache support

[Greg Kroah-Hartman]

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

--

From: Paolo Abeni 

commit 911362c70df5b766c243dc297fadeaced786ffd8 upstream.

This patch add a generic, lockless dst cache implementation.
The need for lock is avoided updating the dst cache fields
only in per cpu scope, and requiring that the cache manipulation
functions are invoked with the local bh disabled.

The refresh_ts and reset_ts fields are used to ensure the cache
consistency in case of cuncurrent cache update (dst_cache_set*) and
reset operation (dst_cache_reset).

Consider the following scenario:

CPU1:   CPU2:
  
  

dst_cache_reset()
  dst_cache_set()

The dst entry set passed to dst_cache_set() should not be used
for later dst cache lookup, because it's obtained using old
configuration values.

Since the refresh_ts is updated only on dst_cache lookup, the
cached value in the above scenario will be discarded on the next
lookup.

Signed-off-by: Paolo Abeni 
Suggested-and-acked-by: Hannes Frederic Sowa 
Signed-off-by: David S. Miller 
Signed-off-by: Manoj Boopathi Raj 
Signed-off-by: Greg Kroah-Hartman 

---
 include/net/dst_cache.h |   97 +++
 net/Kconfig |4 +
 net/core/Makefile   |1 
 net/core/dst_cache.c|  168 
 4 files changed, 270 insertions(+)

--- /dev/null
+++ b/include/net/dst_cache.h
@@ -0,0 +1,97 @@
+#ifndef _NET_DST_CACHE_H
+#define _NET_DST_CACHE_H
+
+#include 
+#include 
+#if IS_ENABLED(CONFIG_IPV6)
+#include 
+#endif
+
+struct dst_cache {
+   struct dst_cache_pcpu __percpu *cache;
+   unsigned long reset_ts;
+};
+
+/**
+ * dst_cache_get - perform cache lookup
+ * @dst_cache: the cache
+ *
+ * The caller should use dst_cache_get_ip4() if it need to retrieve the
+ * source address to be used when xmitting to the cached dst.
+ * local BH must be disabled.
+ */
+struct dst_entry *dst_cache_get(struct dst_cache *dst_cache);
+
+/**
+ * dst_cache_get_ip4 - perform cache lookup and fetch ipv4 source address
+ * @dst_cache: the cache
+ * @saddr: return value for the retrieved source address
+ *
+ * local BH must be disabled.
+ */
+struct rtable *dst_cache_get_ip4(struct dst_cache *dst_cache, __be32 *saddr);
+
+/**
+ * dst_cache_set_ip4 - store the ipv4 dst into the cache
+ * @dst_cache: the cache
+ * @dst: the entry to be cached
+ * @saddr: the source address to be stored inside the cache
+ *
+ * local BH must be disabled.
+ */
+void dst_cache_set_ip4(struct dst_cache *dst_cache, struct dst_entry *dst,
+  __be32 saddr);
+
+#if IS_ENABLED(CONFIG_IPV6)
+
+/**
+ * dst_cache_set_ip6 - store the ipv6 dst into the cache
+ * @dst_cache: the cache
+ * @dst: the entry to be cached
+ * @saddr: the source address to be stored inside the cache
+ *
+ * local BH must be disabled.
+ */
+void dst_cache_set_ip6(struct dst_cache *dst_cache, struct dst_entry *dst,
+  const struct in6_addr *addr);
+
+/**
+ * dst_cache_get_ip6 - perform cache lookup and fetch ipv6 source address
+ * @dst_cache: the cache
+ * @saddr: return value for the retrieved source address
+ *
+ * local BH must be disabled.
+ */
+struct dst_entry *dst_cache_get_ip6(struct dst_cache *dst_cache,
+   struct in6_addr *saddr);
+#endif
+
+/**
+ * dst_cache_reset - invalidate the cache contents
+ * @dst_cache: the cache
+ *
+ * This do not free the cached dst to avoid races and contentions.
+ * the dst will be freed on later cache lookup.
+ */
+static inline void dst_cache_reset(struct dst_cache *dst_cache)
+{
+   dst_cache->reset_ts = jiffies;
+}
+
+/**
+ * dst_cache_init - initialize the cache, allocating the required storage
+ * @dst_cache: the cache
+ * @gfp: allocation flags
+ */
+int dst_cache_init(struct dst_cache *dst_cache, gfp_t gfp);
+
+/**
+ * dst_cache_destroy - empty the cache and free the allocated storage
+ * @dst_cache: the cache
+ *
+ * No synchronization is enforced: it must be called only when the cache
+ * is unsed.
+ */
+void dst_cache_destroy(struct dst_cache *dst_cache);
+
+#endif
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -383,6 +383,10 @@ config LWTUNNEL
  weight tunnel endpoint. Tunnel encapsulation parameters are stored
  with light weight tunnel state associated with fib routes.
 
+config DST_CACHE
+   bool "dst cache"
+   default n
+
 endif   # if NET
 
 # Used by archs to tell that they support BPF_JIT
--- a/net/core/Makefile
+++ b/net/core/Makefile
@@ -24,3 +24,4 @@ obj-$(CONFIG_NET_PTP_CLASSIFY) += ptp_cl
 obj-$(CONFIG_CGROUP_NET_PRIO) += netprio_cgroup.o
 obj-$(CONFIG_CGROUP_NET_CLASSID) += netclassid_cgroup.o
 obj-$(CONFIG_LWTUNNEL) +=