From e8f36330d9bb27f9f7e66aa6f01ff92c07d86f62 Mon Sep 17 00:00:00 2001 From: Baruch Siach Date: Wed, 7 Sep 2011 17:52:37 +0200 Subject: networking: consolidate the IP checksum code. -129 bytes. Signed-off-by: Baruch Siach Signed-off-by: Denys Vlasenko --- libbb/inet_cksum.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 libbb/inet_cksum.c (limited to 'libbb/inet_cksum.c') diff --git a/libbb/inet_cksum.c b/libbb/inet_cksum.c new file mode 100644 index 000000000..31bf8c4d9 --- /dev/null +++ b/libbb/inet_cksum.c @@ -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; +} -- cgit v1.2.3