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networking: consolidate the IP checksum code. -129 bytes.

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Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Baruch Siach
2011-09-07 17:52:37 +02:00
committed by Denys Vlasenko
parent 8c84f7545c
commit e8f36330d9
7 changed files with 48 additions and 95 deletions
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6
libbb/Kbuild.src
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@ -166,6 +166,12 @@ lib-$(CONFIG_IOSTAT) += get_cpu_count.o
lib-$(CONFIG_MPSTAT) += get_cpu_count.o
lib-$(CONFIG_POWERTOP) += get_cpu_count.o
lib-$(CONFIG_PING) += inet_cksum.o
lib-$(CONFIG_TRACEROUTE) += inet_cksum.o
lib-$(CONFIG_TRACEROUTE6) += inet_cksum.o
lib-$(CONFIG_UDHCPC) += inet_cksum.o
lib-$(CONFIG_UDHCPD) += inet_cksum.o
# We shouldn't build xregcomp.c if we don't need it - this ensures we don't
# require regex.h to be in the include dir even if we don't need it thereby
# allowing us to build busybox even if uclibc regex support is disabled.

32
libbb/inet_cksum.c Normal file
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@ -0,0 +1,32 @@
/*
* Checksum routine for Internet Protocol family headers (C Version)
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
#include "libbb.h"
uint16_t FAST_FUNC inet_cksum(uint16_t *addr, int nleft)
{
/*
* Our algorithm is simple, using a 32 bit accumulator,
* we add sequential 16 bit words to it, and at the end, fold
* back all the carry bits from the top 16 bits into the lower
* 16 bits.
*/
unsigned sum = 0;
while (nleft > 1) {
sum += *addr++;
nleft -= 2;
}
/* Mop up an odd byte, if necessary */
if (nleft)
sum += *(uint8_t*)addr;
/* Add back carry outs from top 16 bits to low 16 bits */
sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
sum += (sum >> 16); /* add carry */
return (uint16_t)~sum;
}