/****************************************************************************
* net/utils/net_chksum.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#ifdef CONFIG_NET
#include "utils/utils.h"
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: chksum
*
* Description:
* Calculate the raw change sum over the memory region described by
* data and len.
*
* Input Parameters:
* sum - Partial calculations carried over from a previous call to
* chksum(). This should be zero on the first time that check
* sum is called.
* data - Beginning of the data to include in the checksum.
* len - Length of the data to include in the checksum.
*
* Returned Value:
* The updated checksum value.
*
****************************************************************************/
#ifndef CONFIG_NET_ARCH_CHKSUM
uint16_t chksum(uint16_t sum, FAR const uint8_t *data, uint16_t len)
{
FAR const uint8_t *dataptr;
FAR const uint8_t *last_byte;
uint16_t t;
dataptr = data;
last_byte = data + len - 1;
while (dataptr < last_byte)
{
/* At least two more bytes */
t = ((uint16_t)dataptr[0] << 8) + dataptr[1];
sum += t;
if (sum < t)
{
sum++; /* carry */
}
dataptr += 2;
}
if (dataptr == last_byte)
{
t = (dataptr[0] << 8) + 0;
sum += t;
if (sum < t)
{
sum++; /* carry */
}
}
/* Return sum in host byte order. */
return sum;
}
#endif /* CONFIG_NET_ARCH_CHKSUM */
/****************************************************************************
* Name: chksum_iob
*
* Description:
* Calculate the Internet checksum over an iob chain buffer.
*
* Input Parameters:
* sum - Partial calculations carried over from a previous call to
* chksum(). This should be zero on the first time that check
* sum is called.
* iob - An iob chain buffer over which the checksum is to be computed.
* offset - Specifies the byte offset of the start of valid data.
*
* Returned Value:
* The updated checksum value.
*
****************************************************************************/
#ifdef CONFIG_MM_IOB
uint16_t chksum_iob(uint16_t sum, FAR struct iob_s *iob, uint16_t offset)
{
/* Skip to the I/O buffer containing the data offset */
while (iob != NULL && offset > iob->io_len)
{
offset -= iob->io_len;
iob = iob->io_flink;
}
/* If the link pointer is not empty, loop to walk through all I/O buffer
* and accumulate the sum
*/
while (iob != NULL)
{
sum = chksum(sum, iob->io_data + iob->io_offset + offset,
iob->io_len - offset);
iob = iob->io_flink;
offset = 0;
}
return sum;
}
#endif /* CONFIG_MM_IOB */
/****************************************************************************
* Name: net_chksum
*
* Description:
* Calculate the Internet checksum over a buffer.
*
* The Internet checksum is the one's complement of the one's complement
* sum of all 16-bit words in the buffer.
*
* See RFC1071.
*
* If CONFIG_NET_ARCH_CHKSUM is defined, then this function must be
* provided by architecture-specific logic.
*
* Input Parameters:
*
* buf - A pointer to the buffer over which the checksum is to be computed.
*
* len - The length of the buffer over which the checksum is to be
* computed.
*
* Returned Value:
* The Internet checksum of the buffer.
*
****************************************************************************/
#ifndef CONFIG_NET_ARCH_CHKSUM
uint16_t net_chksum(FAR uint16_t *data, uint16_t len)
{
return HTONS(chksum(0, (uint8_t *)data, len));
}
#endif /* CONFIG_NET_ARCH_CHKSUM */
/****************************************************************************
* Name: net_chksum_iob
*
* Description:
* Calculate the Internet checksum over an iob chain buffer.
*
* The Internet checksum is the one's complement of the one's complement
* sum of all 16-bit words in the buffer.
*
* See RFC1071.
*
* If CONFIG_NET_ARCH_CHKSUM is defined, then this function must be
* provided by architecture-specific logic.
*
* Input Parameters:
* sum - Partial calculations carried over from a previous call to
* chksum(). This should be zero on the first time that check
* sum is called.
* iob - An iob chain buffer over which the checksum is to be computed.
* offset - Specifies the byte offset of the start of valid data.
*
* Returned Value:
* The Internet checksum of the given iob chain buffer.
*
****************************************************************************/
#ifdef CONFIG_MM_IOB
uint16_t net_chksum_iob(uint16_t sum, FAR struct iob_s *iob, uint16_t offset)
{
return HTONS(chksum_iob(sum, iob, offset));
}
#endif /* CONFIG_MM_IOB */
/****************************************************************************
* Name: net_chksum_adjust
*
* Description:
* Adjusts the checksum of a packet without having to completely
* recalculate it, as described in RFC 3022, Section 4.2, Page 9.
*
* Input Parameters:
* chksum - points to the chksum in the packet
* optr - points to the old data in the packet
* olen - length of old data
* nptr - points to the new data in the packet
* nlen - length of new data
*
* Limitations:
* The algorithm is applicable only for even offsets and even lengths.
****************************************************************************/
void net_chksum_adjust(FAR uint16_t *chksum,
FAR const uint16_t *optr, ssize_t olen,
FAR const uint16_t *nptr, ssize_t nlen)
{
int32_t x;
int32_t oldval;
int32_t newval;
x = NTOHS(*chksum);
x = ~x & 0xffff;
while (olen > 0)
{
oldval = NTOHS(*optr);
x -= oldval & 0xffff;
if (x <= 0)
{
x--;
x &= 0xffff;
}
optr++;
olen -= 2;
}
while (nlen > 0)
{
newval = NTOHS(*nptr);
x += newval & 0xffff;
if ((x & 0x10000) != 0)
{
x++;
x &= 0xffff;
}
nptr++;
nlen -= 2;
}
x = ~x & 0xffff;
*chksum = HTONS(x);
}
#endif /* CONFIG_NET */