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authorOndrej Zajicek <santiago@crfreenet.org>2010-04-25 19:13:49 +0200
committerOndrej Zajicek <santiago@crfreenet.org>2010-04-25 19:13:49 +0200
commitc1b51598d49ff737b926bd8ad2e308a5a15ce3a2 (patch)
treed7cf127181d86870eb1f07f780ba65097e04f27f
parent0ea8fb4abe5acad0b8f470bbdc5cc929b6a58ced (diff)
downloadbird-c1b51598d49ff737b926bd8ad2e308a5a15ce3a2.tar
bird-c1b51598d49ff737b926bd8ad2e308a5a15ce3a2.zip
Implements changes in checksum alg suggested by Joakim Tjernlund.
-rw-r--r--lib/checksum.c51
1 files changed, 18 insertions, 33 deletions
diff --git a/lib/checksum.c b/lib/checksum.c
index 33cb386..18b1f92 100644
--- a/lib/checksum.c
+++ b/lib/checksum.c
@@ -15,26 +15,21 @@
#include "nest/bird.h"
#include "checksum.h"
-static u16 /* One-complement addition */
-add16(u16 sum, u16 x)
-{
- u16 z = sum + x;
- return z + (z < sum);
-}
-
-static u32
+static inline u32
add32(u32 sum, u32 x)
{
u32 z = sum + x;
- return z + (z < sum);
+// return z + (z < sum);
+
+ /* add carry */
+ if (z < x)
+ z++;
+ return z;
}
static u16
-ipsum_calc_block(u16 *x, unsigned len, u16 sum)
+ipsum_calc_block(u32 *buf, unsigned len, u16 isum)
{
- int rest;
- u32 tmp, *xx;
-
/*
* A few simple facts about the IP checksum (see RFC 1071 for detailed
* discussion):
@@ -47,27 +42,17 @@ ipsum_calc_block(u16 *x, unsigned len, u16 sum)
* usual alignment requirements and is reasonably fast.
*/
- ASSERT(!(len % 2));
+ ASSERT(!(len % 4));
if (!len)
- return sum;
- len >>= 1;
- if ((unsigned long) x & 2) /* Align to 32-bit boundary */
- {
- sum = add16(sum, *x++);
- len--;
- }
- rest = len & 1;
- len >>= 1;
- tmp = 0;
- xx = (u32 *) x;
- while (len)
- {
- tmp = add32(tmp, *xx++);
- len--;
- }
- sum = add16(sum, add16(tmp & 0xffff, tmp >> 16U));
- if (rest)
- sum = add16(sum, *(u16 *) xx);
+ return isum;
+
+ u32 *end = buf + (len >> 2);
+ u32 sum = isum;
+ while (buf < end)
+ sum = add32(sum, *buf++);
+
+ sum = (sum >> 16) + (sum & 0xffff); /* add high-16 to low-16 */
+ sum += (sum >> 16); /* add carry */
return sum;
}