net: Add a separate file for IP checksumming

Move the checksum code out into its own file so it can be used elsewhere.
Also use a new version which supports a length which is not a multiple of
2 and add a new function to add two checksums.

Signed-off-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Simon Glass 2015-01-19 22:16:07 -07:00
parent 5da38086bd
commit 9b0e35cb48
3 changed files with 91 additions and 0 deletions

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@ -482,6 +482,36 @@ extern void net_set_ip_header(uchar *pkt, IPaddr_t dest, IPaddr_t source);
extern void net_set_udp_header(uchar *pkt, IPaddr_t dest, int dport,
int sport, int len);
/**
* compute_ip_checksum() - Compute IP checksum
*
* @addr: Address to check (must be 16-bit aligned)
* @nbytes: Number of bytes to check (normally a multiple of 2)
* @return 16-bit IP checksum
*/
unsigned compute_ip_checksum(const void *addr, unsigned nbytes);
/**
* add_ip_checksums() - add two IP checksums
*
* @offset: Offset of first sum (if odd we do a byte-swap)
* @sum: First checksum
* @new_sum: New checksum to add
* @return updated 16-bit IP checksum
*/
unsigned add_ip_checksums(unsigned offset, unsigned sum, unsigned new_sum);
/**
* ip_checksum_ok() - check if a checksum is correct
*
* This works by making sure the checksum sums to 0
*
* @addr: Address to check (must be 16-bit aligned)
* @nbytes: Number of bytes to check (normally a multiple of 2)
* @return true if the checksum matches, false if not
*/
int ip_checksum_ok(const void *addr, unsigned nbytes);
/* Checksum */
extern int NetCksumOk(uchar *, int); /* Return true if cksum OK */
extern uint NetCksum(uchar *, int); /* Calculate the checksum */

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@ -7,6 +7,7 @@
#ccflags-y += -DDEBUG
obj-y += checksum.o
obj-$(CONFIG_CMD_NET) += arp.o
obj-$(CONFIG_CMD_NET) += bootp.o
obj-$(CONFIG_CMD_CDP) += cdp.o

60
net/checksum.c Normal file
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@ -0,0 +1,60 @@
/*
* This file was originally taken from the FreeBSD project.
*
* Copyright (c) 2001 Charles Mott <cm@linktel.net>
* Copyright (c) 2008 coresystems GmbH
* All rights reserved.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <common.h>
#include <net.h>
unsigned compute_ip_checksum(const void *vptr, unsigned nbytes)
{
int sum, oddbyte;
const unsigned short *ptr = vptr;
sum = 0;
while (nbytes > 1) {
sum += *ptr++;
nbytes -= 2;
}
if (nbytes == 1) {
oddbyte = 0;
((u8 *)&oddbyte)[0] = *(u8 *)ptr;
((u8 *)&oddbyte)[1] = 0;
sum += oddbyte;
}
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
sum = ~sum & 0xffff;
return sum;
}
unsigned add_ip_checksums(unsigned offset, unsigned sum, unsigned new)
{
unsigned long checksum;
sum = ~sum & 0xffff;
new = ~new & 0xffff;
if (offset & 1) {
/*
* byte-swap the sum if it came from an odd offset; since the
* computation is endian independant this works.
*/
new = ((new >> 8) & 0xff) | ((new << 8) & 0xff00);
}
checksum = sum + new;
if (checksum > 0xffff)
checksum -= 0xffff;
return (~checksum) & 0xffff;
}
int ip_checksum_ok(const void *addr, unsigned nbytes)
{
return !(compute_ip_checksum(addr, nbytes) & 0xfffe);
}