import checksum..[ch] from sgsnemu of osmo-ggsn.git

This commit is contained in:
Harald Welte 2021-10-24 11:37:00 +02:00
commit 9cf4b4a3e8
2 changed files with 224 additions and 0 deletions

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/*
*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* IP/TCP/UDP checksumming routines
*
* Authors: Jorge Cwik, <jorge@laser.satlink.net>
* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
* Tom May, <ftom@netcom.com>
* Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de>
* Lots of code moved from tcp.c and ip.c; see those files
* for more names.
*
* 03/02/96 Jes Sorensen, Andreas Schwab, Roman Hodek:
* Fixed some nasty bugs, causing some horrible crashes.
* A: At some points, the sum (%0) was used as
* length-counter instead of the length counter
* (%1). Thanks to Roman Hodek for pointing this out.
* B: GCC seems to mess up if one uses too many
* data-registers to hold input values and one tries to
* specify d0 and d1 as scratch registers. Letting gcc
* choose these registers itself solves the problem.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
/* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access
kills, so most of the assembly has to go. */
#if defined(__FreeBSD__)
#define _KERNEL /* needed on FreeBSD 10.x for s6_addr32 */
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/endian.h>
#endif
#include "checksum.h"
#include <arpa/inet.h>
static inline unsigned short from32to16(unsigned int x)
{
/* add up 16-bit and 16-bit for 16+c bit */
x = (x & 0xffff) + (x >> 16);
/* add up carry.. */
x = (x & 0xffff) + (x >> 16);
return x;
}
static unsigned int do_csum(const unsigned char *buff, int len)
{
int odd;
unsigned int result = 0;
if (len <= 0)
goto out;
odd = 1 & (unsigned long) buff;
if (odd) {
#if BYTE_ORDER == LITTLE_ENDIAN
result += (*buff << 8);
#else
result = *buff;
#endif
len--;
buff++;
}
if (len >= 2) {
if (2 & (unsigned long) buff) {
result += *(unsigned short *) buff;
len -= 2;
buff += 2;
}
if (len >= 4) {
const unsigned char *end = buff + ((unsigned)len & ~3);
unsigned int carry = 0;
do {
unsigned int w = *(unsigned int *) buff;
buff += 4;
result += carry;
result += w;
carry = (w > result);
} while (buff < end);
result += carry;
result = (result & 0xffff) + (result >> 16);
}
if (len & 2) {
result += *(unsigned short *) buff;
buff += 2;
}
}
if (len & 1)
#if BYTE_ORDER == LITTLE_ENDIAN
result += *buff;
#else
result += (*buff << 8);
#endif
result = from32to16(result);
if (odd)
result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
out:
return result;
}
/*
* This is a version of ip_compute_csum() optimized for IP headers,
* which always checksum on 4 octet boundaries.
*/
uint16_t ip_fast_csum(const void *iph, unsigned int ihl)
{
return (uint16_t)~do_csum(iph, ihl*4);
}
/*
* computes the checksum of a memory block at buff, length len,
* and adds in "sum" (32-bit)
*
* returns a 32-bit number suitable for feeding into itself
* or csum_tcpudp_magic
*
* this function must be called with even lengths, except
* for the last fragment, which may be odd
*
* it's best to have buff aligned on a 32-bit boundary
*/
uint32_t csum_partial(const void *buff, int len, uint32_t wsum)
{
unsigned int sum = (unsigned int)wsum;
unsigned int result = do_csum(buff, len);
/* add in old sum, and carry.. */
result += sum;
if (sum > result)
result += 1;
return (uint32_t)result;
}
/*
* this routine is used for miscellaneous IP-like checksums, mainly
* in icmp.c
*/
uint16_t ip_compute_csum(const void *buff, int len)
{
return (uint16_t)~do_csum(buff, len);
}
uint16_t csum_ipv6_magic(const struct in6_addr *saddr,
const struct in6_addr *daddr,
uint32_t len, uint8_t proto, uint32_t csum)
{
int carry;
uint32_t ulen;
uint32_t uproto;
uint32_t sum = (uint32_t)csum;
sum += (uint32_t)saddr->s6_addr32[0];
carry = (sum < (uint32_t)saddr->s6_addr32[0]);
sum += carry;
sum += (uint32_t)saddr->s6_addr32[1];
carry = (sum < (uint32_t)saddr->s6_addr32[1]);
sum += carry;
sum += (uint32_t)saddr->s6_addr32[2];
carry = (sum < (uint32_t)saddr->s6_addr32[2]);
sum += carry;
sum += (uint32_t)saddr->s6_addr32[3];
carry = (sum < (uint32_t)saddr->s6_addr32[3]);
sum += carry;
sum += (uint32_t)daddr->s6_addr32[0];
carry = (sum < (uint32_t)daddr->s6_addr32[0]);
sum += carry;
sum += (uint32_t)daddr->s6_addr32[1];
carry = (sum < (uint32_t)daddr->s6_addr32[1]);
sum += carry;
sum += (uint32_t)daddr->s6_addr32[2];
carry = (sum < (uint32_t)daddr->s6_addr32[2]);
sum += carry;
sum += (uint32_t)daddr->s6_addr32[3];
carry = (sum < (uint32_t)daddr->s6_addr32[3]);
sum += carry;
ulen = (uint32_t)htonl((uint32_t) len);
sum += ulen;
carry = (sum < ulen);
sum += carry;
uproto = (uint32_t)htonl(proto);
sum += uproto;
carry = (sum < uproto);
sum += carry;
return csum_fold((uint32_t)sum);
}
/* fold a partial checksum */
uint16_t csum_fold(uint32_t csum)
{
uint32_t sum = (uint32_t)csum;
sum = (sum & 0xffff) + (sum >> 16);
sum = (sum & 0xffff) + (sum >> 16);
return (uint16_t)~sum;
}

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#pragma once
#include <stdint.h>
#include <netinet/in.h>
uint16_t ip_fast_csum(const void *iph, unsigned int ihl);
uint32_t csum_partial(const void *buff, int len, uint32_t wsum);
uint16_t ip_compute_csum(const void *buff, int len);
uint16_t csum_ipv6_magic(const struct in6_addr *saddr,
const struct in6_addr *daddr,
uint32_t len, uint8_t proto, uint32_t csum);
uint16_t csum_fold(uint32_t csum);