/*
 * Copyright (c) 2016 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.
 */

#include <vnet/vnet.h>
#include "ip6_ioam_seqno.h"

static inline void BIT_SET (u64 *p, u32 n)
{
  p[ n>>5 ] |= (1 << (n&31));
}

static inline int BIT_TEST (u64 *p, u32 n)
{
  return p[ n>>5 ] & (1 << (n&31));
}

static void BIT_CLEAR (u64 *p, u64 start, int  num_bits, u32 mask)
{
  int n, t;
  int start_index = (start >> 5);
  int mask_index = (mask >> 5);

  start_index &= mask_index;
  if (start & 0x1f)
    {
      int start_bit = (start & 0x1f);

      n = (1 << start_bit)-1;
      t = start_bit + num_bits;
      if (t < 32)
        {
          n |= ~((1 << t)-1);
          p[ start_index ] &= n;
          return;
        }
      p[ start_index ] &= n;
      start_index = (start_index + 1) & mask_index;
      num_bits -= (32 - start_bit);
    }
  while (num_bits >= 32)
    {
      p[ start_index ] = 0;
      start_index = (start_index + 1) & mask_index;
      num_bits -= 32;
    }
  n = ~((1 << num_bits) - 1);
  p[ start_index ] &= n;
}

static inline u8 seqno_check_wraparound(u32 a, u32 b)
{
  if ((a != b) && (a > b) && ((a - b) > SEQ_CHECK_VALUE))
    {
      return 1;
    }
  return 0;
}

/*
 * Function to analyze the PPC value recevied.
 *     - Updates the bitmap with received sequence number
 *     - counts the received/lost/duplicate/reordered packets
 */
void ioam_analyze_seqno (seqno_rx_info *seqno_rx, u64 seqno)
{
  int diff;
  static int peer_dead_count;
  seqno_bitmap *bitmap = &seqno_rx->bitmap;

  seqno_rx->rx_packets++;

  if (seqno > bitmap->highest)
    {   /* new larger sequence number */
      peer_dead_count = 0;
      diff = seqno - bitmap->highest;
      if (diff < bitmap->window_size)
        {
          if (diff > 1)
            { /* diff==1 is *such* a common case it's a win to optimize it */
              BIT_CLEAR(bitmap->array, bitmap->highest+1, diff-1, bitmap->mask);
              seqno_rx->lost_packets += diff -1;
            }
        }
      else
        {
          seqno_rx->lost_packets += diff -1;
          memset( bitmap->array, 0, bitmap->array_size * sizeof(u64) );
        }
      BIT_SET(bitmap->array, seqno & bitmap->mask);
      bitmap->highest = seqno;
      return;
    }

  /* we've seen a bigger seq number before */
  diff = bitmap->highest - seqno;
  if (diff >= bitmap->window_size)
    {
      if (seqno_check_wraparound(bitmap->highest, seqno))
        {
          memset( bitmap->array, 0, bitmap->array_size * sizeof(u64));
          BIT_SET(bitmap->array, seqno & bitmap->mask);
          bitmap->highest = seqno;
          return;
        }
      else
        {
          peer_dead_count++;
          if (peer_dead_count > 25)
            {
              peer_dead_count = 0;
              memset( bitmap->array, 0, bitmap->array_size * sizeof(u64) );
              BIT_SET(bitmap->array, seqno & bitmap->mask);
              bitmap->highest = seqno;
            }
          //ppc_rx->reordered_packets++;
        }
      return;
    }

  if (BIT_TEST(bitmap->array, seqno & bitmap->mask))
    {
      seqno_rx->dup_packets++;
      return;    /* Already seen */
    }
  seqno_rx->reordered_packets++;
  seqno_rx->lost_packets--;
  BIT_SET(bitmap->array, seqno & bitmap->mask);
  return;
}