Refactor the ARP throttle into a common type so it can be reused

Change-Id: Ic7f7af983d5b6d756748023aa0c650f53e9285cf
Signed-off-by: Neale Ranns <neale.ranns@cisco.com>

1 files changed, 79 insertions, 0 deletions

diff --git a/src/vnet/util/throttle.h b/src/vnet/util/throttle.h
new file mode 100644
index 00000000000..0c518d3555b
--- /dev/null
+++ b/src/vnet/util/throttle.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2018 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __THROTTLE_H__
+#define __THROTTLE_H__
+
+#include <vlib/vlib.h>
+
+/**
+ * @brief A throttle
+ *  Used in the data plane to decide if a given hash should be throttled,
+ *  i.e. that the hash has been seen alreay 'recently'. Recent is the time
+ *  given in the throttle's initialisation.
+ */
+typedef struct throttle_t_
+{
+  f64 time;
+  uword **bitmaps;
+  u32 *seeds;
+  f64 *last_seed_change_time;
+} throttle_t;
+
+#define THROTTLE_BITS	(512)
+
+extern void throttle_init (throttle_t * t, u32 n_threads, f64 time);
+
+always_inline u32
+throttle_seed (throttle_t * t, u32 thread_index, f64 time_now)
+{
+  if (time_now - t->last_seed_change_time[thread_index] > t->time)
+    {
+      (void) random_u32 (&t->seeds[thread_index]);
+      memset (t->bitmaps[thread_index], 0, THROTTLE_BITS / BITS (u8));
+
+      t->last_seed_change_time[thread_index] = time_now;
+    }
+  return t->seeds[thread_index];
+}
+
+always_inline int
+throttle_check (throttle_t * t, u32 thread_index, u32 hash, u32 seed)
+{
+  int drop;
+  uword m;
+  u32 w;
+
+  hash ^= seed;
+  /* Select bit number */
+  hash &= THROTTLE_BITS - 1;
+  w = hash / BITS (uword);
+  m = (uword) 1 << (hash % BITS (uword));
+
+  drop = (t->bitmaps[thread_index][w] & m) != 0;
+  t->bitmaps[thread_index][w] |= m;
+
+  return (drop);
+}
+
+#endif
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */