ip_checksum.c

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/*
 * 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.
 */
/*
 * ip4/ip_checksum.c: ip/tcp/udp checksums
 *
 * Copyright (c) 2008 Eliot Dresselhaus
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include <vnet/ip/ip.h>

static ip_csum_t
_ip_incremental_checksum (ip_csum_t sum, void *_data, uword n_bytes)
{
  uword data = pointer_to_uword (_data);
  ip_csum_t sum0, sum1;

  sum0 = 0;
  sum1 = sum;

  /*
   * Align pointer to 64 bits. The ip checksum is a 16-bit
   * one's complememt sum. It's impractical to optimize
   * the calculation if the incoming address is odd.
   */
#define _(t)                                    \
do {                                            \
  if (n_bytes >= sizeof (t)                     \
      && sizeof (t) < sizeof (ip_csum_t)        \
      && (data % (2 * sizeof (t))) != 0)        \
    {                                           \
      sum0 += * uword_to_pointer (data, t *);   \
      data += sizeof (t);                       \
      n_bytes -= sizeof (t);                    \
    }                                           \
} while (0)

  if (PREDICT_TRUE ((data & 1) == 0))
    {
      _(u16);
      if (BITS (ip_csum_t) > 32)
        _(u32);
    }
#undef _

  {
    ip_csum_t *d = uword_to_pointer (data, ip_csum_t *);

    while (n_bytes >= 2 * sizeof (d[0]))
      {
        sum0 = ip_csum_with_carry (sum0, d[0]);
        sum1 = ip_csum_with_carry (sum1, d[1]);
        d += 2;
        n_bytes -= 2 * sizeof (d[0]);
      }

    data = pointer_to_uword (d);
  }

#define _(t)                                                            \
do {                                                                    \
  if (n_bytes >= sizeof (t) && sizeof (t) <= sizeof (ip_csum_t))        \
    {                                                                   \
      sum0 = ip_csum_with_carry (sum0, * uword_to_pointer (data, t *)); \
      data += sizeof (t);                                               \
      n_bytes -= sizeof (t);                                            \
    }                                                                   \
} while (0)

  if (BITS (ip_csum_t) > 32)
    _(u64);
  _(u32);
  _(u16);
  _(u8);

#undef _

  /* Combine even and odd sums. */
  sum0 = ip_csum_with_carry (sum0, sum1);

  return sum0;
}

/*
 * Note: the tcp / udp checksum calculation is performance critical
 * [e.g. when NIC h/w offload is not available],
 * so it's worth producing architecture-dependent code.
 *
 * ip_incremental_checksum() is an always-inlined static
 * function which uses the function pointer we set up in
 * ip_checksum_init().
 */

ip_csum_t (*vnet_incremental_checksum_fp) (ip_csum_t, void *, uword);

static clib_error_t *
ip_checksum_init (vlib_main_t * vm)
{
  vnet_incremental_checksum_fp = _ip_incremental_checksum;
  return 0;
}

VLIB_INIT_FUNCTION (ip_checksum_init);

#if CLIB_DEBUG > 0

static const char test_pkt[] = {
  0x45, 0x00, 0x00, 0x3c, 0x5d, 0x6f, 0x40, 0x00,
  0x40, 0x06, 0x3f, 0x6b, 0x0a, 0x76, 0x72, 0x44,
  0x0a, 0x56, 0x16, 0xd2,
};

static clib_error_t *
test_ip_checksum_fn (vlib_main_t * vm,
                     unformat_input_t * input, vlib_cli_command_t * cmd)
{
  u16 csum;
  ip4_header_t *hp;
  u8 *align_test = 0;
  int offset;

  vec_validate (align_test, ARRAY_LEN (test_pkt) + 7);

  for (offset = 0; offset < 8; offset++)
    {
      memcpy (align_test + offset, test_pkt, ARRAY_LEN (test_pkt));

      hp = (ip4_header_t *) (align_test + offset);
      csum = ip4_header_checksum (hp);

      vlib_cli_output (vm, "offset %d checksum %u expected result 27455",
                       offset, (u32) csum);
    }

  return 0;
}

/* *INDENT-OFF* */
VLIB_CLI_COMMAND (test_checksum, static) =
{
  .path = "test ip checksum",
  .short_help = "test ip checksum",
  .function = test_ip_checksum_fn,
};
/* *INDENT-ON* */

#endif /* CLIB_DEBUG */

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