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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** NetX Component */
/** */
/** Internet Protocol Checksum Computation */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SOURCE_CODE
/* Include necessary system files. */
#include "nx_api.h"
#include "nx_icmp.h"
#include "nx_icmpv6.h"
#include "nx_ip.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_ip_checksum_compute PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* Yuxin Zhou, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function computes the checksum from the supplied packet */
/* pointer and IP address fields required for the pseudo header. */
/* */
/* INPUT */
/* */
/* packet_ptr Pointer to packet */
/* protocol Protocol type */
/* data_length Size of the protocol payload */
/* src_ip_addr IPv4 or IPv6 address, used in */
/* constructing pseudo header.*/
/* dest_ip_addr IPv4 or IPv6 address, used in */
/* constructing pseudo header.*/
/* */
/* OUTPUT */
/* */
/* computed checksum */
/* */
/* CALLS */
/* */
/* None */
/* */
/* CALLED BY */
/* */
/* NetX Duo internal routines */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Yuxin Zhou Initial Version 6.0 */
/* 09-30-2020 Yuxin Zhou Modified comment(s), */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
USHORT _nx_ip_checksum_compute(NX_PACKET *packet_ptr, ULONG protocol,
UINT data_length, ULONG *src_ip_addr,
ULONG *dest_ip_addr)
{
ULONG checksum = 0;
USHORT tmp;
USHORT *short_ptr;
ULONG *long_ptr;
#ifndef NX_DISABLE_PACKET_CHAIN
ULONG packet_size;
#endif /* NX_DISABLE_PACKET_CHAIN */
NX_PACKET *current_packet;
ALIGN_TYPE end_ptr;
#ifdef FEATURE_NX_IPV6
UINT i;
#endif
/* For computing TCP/UDP/ICMPv6, we need to include the pseudo header.
The ICMPv4 checksum does not cover the pseudo header. */
if ((protocol == NX_PROTOCOL_UDP) ||
#ifdef FEATURE_NX_IPV6
(protocol == NX_PROTOCOL_ICMPV6) ||
#endif /* FEATURE_NX_IPV6 */
(protocol == NX_PROTOCOL_TCP))
{
USHORT *src_ip_short, *dest_ip_short;
checksum = protocol;
/* The addresses must not be null. */
NX_ASSERT((src_ip_addr != NX_NULL) && (dest_ip_addr != NX_NULL));
/*lint -e{929} -e{740} suppress cast of pointer to pointer, since it is necessary */
src_ip_short = (USHORT *)src_ip_addr;
/*lint -e{929} -e{740} suppress cast of pointer to pointer, since it is necessary */
dest_ip_short = (USHORT *)dest_ip_addr;
checksum += src_ip_short[0];
checksum += src_ip_short[1];
checksum += dest_ip_short[0];
checksum += dest_ip_short[1];
#ifdef FEATURE_NX_IPV6
/* Note that the IPv6 address is 128 bits/4 words
compared with the 32 IPv4 address.*/
if (packet_ptr -> nx_packet_ip_version == NX_IP_VERSION_V6)
{
for (i = 2; i < 8; i++)
{
checksum += dest_ip_short[i];
checksum += src_ip_short[i];
}
}
#endif /* FEATURE_NX_IPV6 */
/* Take care of data length */
checksum += data_length;
/* Fold a 4-byte value into a two byte value */
checksum = (checksum >> 16) + (checksum & 0xFFFF);
/* Do it again in case previous operation generates an overflow */
checksum = (checksum >> 16) + (checksum & 0xFFFF);
/* Convert to network byte order. */
tmp = (USHORT)checksum;
NX_CHANGE_USHORT_ENDIAN(tmp);
checksum = tmp;
}
/* Now we need to go through the payloads */
/* Setup the pointer to the start of the packet. */
/*lint -e{927} -e{826} suppress cast of pointer to pointer, since it is necessary */
long_ptr = (ULONG *)packet_ptr -> nx_packet_prepend_ptr;
/* Initialize the current packet to the input packet pointer. */
current_packet = packet_ptr;
#ifndef NX_DISABLE_PACKET_CHAIN
/* Loop the packet. */
while (current_packet)
{
/* Calculate current packet size. */
/*lint -e{946} -e{947} suppress pointer subtraction, since it is necessary. */
packet_size = (ULONG)(current_packet -> nx_packet_append_ptr - current_packet -> nx_packet_prepend_ptr);
/* Calculate the end address in this packet. */
if (data_length > (UINT)packet_size)
{
/*lint -e{927} -e{923} -e{826} suppress cast of pointer to pointer, since it is necessary */
end_ptr = ((ALIGN_TYPE)current_packet -> nx_packet_append_ptr) & (ALIGN_TYPE)(~3);
}
else
{
#endif /* NX_DISABLE_PACKET_CHAIN */
/*lint -e{927} -e{826} suppress cast of pointer to pointer, since it is necessary */
end_ptr = (ALIGN_TYPE)current_packet -> nx_packet_prepend_ptr + data_length - 3;
#ifndef NX_DISABLE_PACKET_CHAIN
}
#endif /* NX_DISABLE_PACKET_CHAIN */
/* Set the start address in this packet. */
/*lint -e{927} -e{826} suppress cast of pointer to pointer, since it is necessary */
long_ptr = (ULONG *)current_packet -> nx_packet_prepend_ptr;
/*lint -e{946} suppress pointer subtraction, since it is necessary. */
if ((ALIGN_TYPE)long_ptr < end_ptr)
{
/* Calculate the data_length. */
/*lint -e{923} suppress cast of pointer to ULONG. */
data_length -= (UINT)(((end_ptr + 3) & (ALIGN_TYPE)(~3llu)) - (ALIGN_TYPE)long_ptr);
/* Loop to calculate the packet's checksum. */
/*lint -e{946} suppress pointer subtraction, since it is necessary. */
while ((ALIGN_TYPE)long_ptr < end_ptr)
{
checksum += (*long_ptr & NX_LOWER_16_MASK);
checksum += (*long_ptr >> NX_SHIFT_BY_16);
long_ptr++;
}
}
#ifndef NX_DISABLE_PACKET_CHAIN
/* Determine if we are at the end of the current packet. */
if ((data_length > 0) && (current_packet -> nx_packet_next))
{
/* Is append_ptr two bytes aligned but not four bytes aligned? */
/*lint -e{923} suppress cast of pointer to ULONG. */
if ((((ALIGN_TYPE)current_packet -> nx_packet_append_ptr) & 3) == 2)
{
/* Yes it is. Process the last two bytes in chaining packets. */
/*lint -e{929} -e{740} suppress cast of pointer to pointer, since it is necessary */
short_ptr = (USHORT *)long_ptr;
/*lint -e{929} -e{740} suppress cast of pointer to pointer, since it is necessary */
checksum += *short_ptr;
data_length -= 2;
}
/* We have crossed the packet boundary. Move to the next packet
structure. */
current_packet = current_packet -> nx_packet_next;
}
else
{
/* End the loop. */
current_packet = NX_NULL;
}
}
#endif /* NX_DISABLE_PACKET_CHAIN */
/* Determine if there is only one byte left. */
if (data_length)
{
/* Set the short_ptr. */
short_ptr = (USHORT *)(long_ptr);
/* Check the data length. */
if (data_length == 1)
{
*((UCHAR *)short_ptr + 1) = 0;
}
else if (data_length == 3)
{
checksum += *short_ptr;
short_ptr++;
*((UCHAR *)short_ptr + 1) = 0;
}
checksum += *short_ptr;
}
/* Fold a 4-byte value into a two byte value */
checksum = (checksum >> 16) + (checksum & 0xFFFF);
/* Do it again in case previous operation generates an overflow */
checksum = (checksum >> 16) + (checksum & 0xFFFF);
/* Convert to host byte order. */
tmp = (USHORT)checksum;
NX_CHANGE_USHORT_ENDIAN(tmp);
/* Return the computed checksum. */
return(tmp);
}
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