/*
 * Copyright (c) 2015 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 __ESP_H__
#define __ESP_H__

#include <vnet/ip/ip.h>
#include <vnet/crypto/crypto.h>
#include <vnet/ipsec/ipsec.h>

typedef struct
{
  u32 spi;
  u32 seq;
  u8 data[0];
} esp_header_t;

typedef struct
{
  u8 pad_length;
  u8 next_header;
} esp_footer_t;

/* *INDENT-OFF* */
typedef CLIB_PACKED (struct {
  ip4_header_t ip4;
  esp_header_t esp;
}) ip4_and_esp_header_t;
/* *INDENT-ON* */

/* *INDENT-OFF* */
typedef CLIB_PACKED (struct {
  ip4_header_t ip4;
  udp_header_t udp;
  esp_header_t esp;
}) ip4_and_udp_and_esp_header_t;
/* *INDENT-ON* */

/* *INDENT-OFF* */
typedef CLIB_PACKED (struct {
  ip6_header_t ip6;
  esp_header_t esp;
}) ip6_and_esp_header_t;
/* *INDENT-ON* */

#define ESP_WINDOW_SIZE		(64)
#define ESP_SEQ_MAX		(4294967295UL)
#define ESP_MAX_BLOCK_SIZE	(16)
#define ESP_MAX_ICV_SIZE	(16)

u8 *format_esp_header (u8 * s, va_list * args);

always_inline int
esp_replay_check (ipsec_sa_t * sa, u32 seq)
{
  u32 diff;

  if (PREDICT_TRUE (seq > sa->last_seq))
    return 0;

  diff = sa->last_seq - seq;

  if (ESP_WINDOW_SIZE > diff)
    return (sa->replay_window & (1ULL << diff)) ? 1 : 0;
  else
    return 1;

  return 0;
}

always_inline int
esp_replay_check_esn (ipsec_sa_t * sa, u32 seq)
{
  u32 tl = sa->last_seq;
  u32 th = sa->last_seq_hi;
  u32 diff = tl - seq;

  if (PREDICT_TRUE (tl >= (ESP_WINDOW_SIZE - 1)))
    {
      if (seq >= (tl - ESP_WINDOW_SIZE + 1))
	{
	  sa->seq_hi = th;
	  if (seq <= tl)
	    return (sa->replay_window & (1ULL << diff)) ? 1 : 0;
	  else
	    return 0;
	}
      else
	{
	  sa->seq_hi = th + 1;
	  return 0;
	}
    }
  else
    {
      if (seq >= (tl - ESP_WINDOW_SIZE + 1))
	{
	  sa->seq_hi = th - 1;
	  return (sa->replay_window & (1ULL << diff)) ? 1 : 0;
	}
      else
	{
	  sa->seq_hi = th;
	  if (seq <= tl)
	    return (sa->replay_window & (1ULL << diff)) ? 1 : 0;
	  else
	    return 0;
	}
    }

  return 0;
}

/* TODO seq increment should be atomic to be accessed by multiple workers */
always_inline void
esp_replay_advance (ipsec_sa_t * sa, u32 seq)
{
  u32 pos;

  if (seq > sa->last_seq)
    {
      pos = seq - sa->last_seq;
      if (pos < ESP_WINDOW_SIZE)
	sa->replay_window = ((sa->replay_window) << pos) | 1;
      else
	sa->replay_window = 1;
      sa->last_seq = seq;
    }
  else
    {
      pos = sa->last_seq - seq;
      sa->replay_window |= (1ULL << pos);
    }
}

always_inline void
esp_replay_advance_esn (ipsec_sa_t * sa, u32 seq)
{
  int wrap = sa->seq_hi - sa->last_seq_hi;
  u32 pos;

  if (wrap == 0 && seq > sa->last_seq)
    {
      pos = seq - sa->last_seq;
      if (pos < ESP_WINDOW_SIZE)
	sa->replay_window = ((sa->replay_window) << pos) | 1;
      else
	sa->replay_window = 1;
      sa->last_seq = seq;
    }
  else if (wrap > 0)
    {
      pos = ~seq + sa->last_seq + 1;
      if (pos < ESP_WINDOW_SIZE)
	sa->replay_window = ((sa->replay_window) << pos) | 1;
      else
	sa->replay_window = 1;
      sa->last_seq = seq;
      sa->last_seq_hi = sa->seq_hi;
    }
  else if (wrap < 0)
    {
      pos = ~seq + sa->last_seq + 1;
      sa->replay_window |= (1ULL << pos);
    }
  else
    {
      pos = sa->last_seq - seq;
      sa->replay_window |= (1ULL << pos);
    }
}

always_inline int
esp_seq_advance (ipsec_sa_t * sa)
{
  if (PREDICT_TRUE (sa->use_esn))
    {
      if (PREDICT_FALSE (sa->seq == ESP_SEQ_MAX))
	{
	  if (PREDICT_FALSE
	      (sa->use_anti_replay && sa->seq_hi == ESP_SEQ_MAX))
	    return 1;
	  sa->seq_hi++;
	}
      sa->seq++;
    }
  else
    {
      if (PREDICT_FALSE (sa->use_anti_replay && sa->seq == ESP_SEQ_MAX))
	return 1;
      sa->seq++;
    }

  return 0;
}


always_inline unsigned int
hmac_calc (vlib_main_t * vm, ipsec_sa_t * sa, u8 * data, int data_len,
	   u8 * signature)
{
  vnet_crypto_op_t _op, *op = &_op;

  if (PREDICT_FALSE (sa->integ_op_type == 0))
    return 0;

  op->op = sa->integ_op_type;
  op->key = sa->integ_key.data;
  op->key_len = sa->integ_key.len;
  op->src = data;
  op->len = data_len;
  op->dst = signature;
  op->hmac_trunc_len = sa->integ_trunc_size;

  if (sa->use_esn)
    {
      u32 seq_hi = clib_host_to_net_u32 (sa->seq_hi);

      op->len += 4;
      clib_memcpy (data + data_len, &seq_hi, 4);
    }

  vnet_crypto_process_ops (vm, op, 1);
  return sa->integ_trunc_size;
}

#endif /* __ESP_H__ */

/*
 * fd.io coding-style-patch-verification: ON
 *
 * Local Variables:
 * eval: (c-set-style "gnu")
 * End:
 */