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net/utils: add net_chksum_adjust defined by RFC3022

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net_chksum_adjust is used for fast checksum adjustment after modifying some fields in a network packet. Will be used in NAT.

Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
This commit is contained in:
Zhe Weng 2022-10-31 14:48:46 +08:00 committed by Petro Karashchenko
parent 1befe6076f
commit 66bc2ffbe6
2 changed files with 87 additions and 0 deletions
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65
net/utils/net_chksum.c
View File

@ -123,4 +123,69 @@ uint16_t net_chksum(FAR uint16_t *data, uint16_t len)
}
#endif /* CONFIG_NET_ARCH_CHKSUM */
/****************************************************************************
* 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)
{
#ifdef CONFIG_ENDIAN_BIG
# warning "Not verified on big-endian yet."
#endif
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 */

22
net/utils/utils.h
View File

@ -238,6 +238,28 @@ uint16_t chksum(uint16_t sum, FAR const uint8_t *data, uint16_t len);
uint16_t net_chksum(FAR uint16_t *data, uint16_t len);
/****************************************************************************
* 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);
/****************************************************************************
* Name: ipv4_upperlayer_chksum
*