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| author | Baruch Siach <baruch@tkos.co.il> | 2011-09-07 17:52:37 +0200 |
|---|---|---|
| committer | Denys Vlasenko <vda.linux@googlemail.com> | 2011-09-07 17:55:40 +0200 |
| commit | e8f36330d9bb27f9f7e66aa6f01ff92c07d86f62 (patch) | |
| tree | 863018163a166cc690902d8027a3f04f9f812dd3 /libbb/inet_cksum.c | |
| parent | 8c84f7545cf08925edb23d94d9f6519b338267c6 (diff) | |
| download | busybox-w32-e8f36330d9bb27f9f7e66aa6f01ff92c07d86f62.tar.gz busybox-w32-e8f36330d9bb27f9f7e66aa6f01ff92c07d86f62.tar.bz2 busybox-w32-e8f36330d9bb27f9f7e66aa6f01ff92c07d86f62.zip | |
networking: consolidate the IP checksum code. -129 bytes.
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'libbb/inet_cksum.c')
| -rw-r--r-- | libbb/inet_cksum.c | 32 |
1 files changed, 32 insertions, 0 deletions
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 @@ | |||
| 1 | /* | ||
| 2 | * Checksum routine for Internet Protocol family headers (C Version) | ||
| 3 | * | ||
| 4 | * Licensed under GPLv2, see file LICENSE in this source tree. | ||
| 5 | */ | ||
| 6 | |||
| 7 | #include "libbb.h" | ||
| 8 | |||
| 9 | uint16_t FAST_FUNC inet_cksum(uint16_t *addr, int nleft) | ||
| 10 | { | ||
| 11 | /* | ||
| 12 | * Our algorithm is simple, using a 32 bit accumulator, | ||
| 13 | * we add sequential 16 bit words to it, and at the end, fold | ||
| 14 | * back all the carry bits from the top 16 bits into the lower | ||
| 15 | * 16 bits. | ||
| 16 | */ | ||
| 17 | unsigned sum = 0; | ||
| 18 | while (nleft > 1) { | ||
| 19 | sum += *addr++; | ||
| 20 | nleft -= 2; | ||
| 21 | } | ||
| 22 | |||
| 23 | /* Mop up an odd byte, if necessary */ | ||
| 24 | if (nleft) | ||
| 25 | sum += *(uint8_t*)addr; | ||
| 26 | |||
| 27 | /* Add back carry outs from top 16 bits to low 16 bits */ | ||
| 28 | sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */ | ||
| 29 | sum += (sum >> 16); /* add carry */ | ||
| 30 | |||
| 31 | return (uint16_t)~sum; | ||
| 32 | } | ||