diff options
| -rw-r--r-- | lib/checksum.c | 51 |
1 files changed, 18 insertions, 33 deletions
diff --git a/lib/checksum.c b/lib/checksum.c index 33cb3865..18b1f92c 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; } |