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#ifndef CSUM_H
#define CSUM_H
#include <string.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include "built_in.h"
static inline unsigned short csum(unsigned short *buf, int nwords)
{
unsigned long sum;
for (sum = 0; nwords > 0; nwords--)
sum += *buf++;
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return ~sum;
}
static inline uint16_t calc_csum(void *addr, size_t len)
{
return csum(addr, len >> 1);
}
static inline uint16_t csum_expected(uint16_t sum, uint16_t computed_sum)
{
uint32_t shouldbe;
shouldbe = sum;
shouldbe += ntohs(computed_sum);
shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
return shouldbe;
}
/* Taken and modified from tcpdump, Copyright belongs to them! */
struct cksum_vec {
const uint8_t *ptr;
int len;
};
#define ADDCARRY(x) \
do { if ((x) > 65535) \
(x) -= 65535; \
} while (0)
#define REDUCE \
do { \
l_util.l = sum; \
sum = l_util.s[0] + l_util.s[1]; \
ADDCARRY(sum); \
} while (0)
static inline uint16_t __in_cksum(const struct cksum_vec *vec, int veclen)
{
const uint16_t *w;
int sum = 0, mlen = 0;
int byte_swapped = 0;
union {
uint8_t c[2];
uint16_t s;
} s_util;
union {
uint16_t s[2];
uint32_t l;
} l_util;
for (; veclen != 0; vec++, veclen--) {
if (vec->len == 0)
continue;
w = (const uint16_t *) (const void *) vec->ptr;
if (mlen == -1) {
s_util.c[1] = *(const uint8_t *) w;
sum += s_util.s;
w = (const uint16_t *) (const void *) ((const uint8_t *) w + 1);
mlen = vec->len - 1;
} else
mlen = vec->len;
if ((1 & (unsigned long) w) && (mlen > 0)) {
REDUCE;
sum <<= 8;
s_util.c[0] = *(const uint8_t *) w;
w = (const uint16_t *) (const void *) ((const uint8_t *) w + 1);
mlen--;
byte_swapped = 1;
}
while ((mlen -= 32) >= 0) {
sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
w += 16;
}
mlen += 32;
while ((mlen -= 8) >= 0) {
sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
w += 4;
}
mlen += 8;
if (mlen == 0 && byte_swapped == 0)
continue;
REDUCE;
while ((mlen -= 2) >= 0) {
sum += *w++;
}
if (byte_swapped) {
REDUCE;
sum <<= 8;
byte_swapped = 0;
if (mlen == -1) {
s_util.c[1] = *(const uint8_t *) w;
sum += s_util.s;
mlen = 0;
} else
mlen = -1;
} else if (mlen == -1)
s_util.c[0] = *(const uint8_t *) w;
}
if (mlen == -1) {
s_util.c[1] = 0;
sum += s_util.s;
}
REDUCE;
return (~sum & 0xffff);
}
static inline uint16_t p4_csum(const struct ip *ip, const uint8_t *data,
uint16_t len, uint8_t next_proto)
{
struct cksum_vec vec[2];
struct pseudo_hdr {
uint32_t src;
uint32_t dst;
uint8_t mbz;
uint8_t proto;
uint16_t len;
} ph;
ph.src = ip->ip_src.s_addr;
ph.dst = ip->ip_dst.s_addr;
ph.mbz = 0;
ph.proto = next_proto;
ph.len = htons(len);
vec[0].ptr = (const uint8_t *) (void *) &ph;
vec[0].len = sizeof(ph);
vec[1].ptr = data;
vec[1].len = len;
return __in_cksum(vec, 2);
}
static inline uint16_t p6_csum(const struct ip6_hdr *ip6, const uint8_t *data,
uint32_t len, uint8_t next_proto)
{
struct cksum_vec vec[2];
struct pseudo_hdr {
uint8_t src[16];
uint8_t dst[16];
uint32_t len;
uint8_t mbz[3];
uint8_t proto;
} __packed ph;
memcpy(&ph.src, ip6->ip6_src.s6_addr, sizeof(ph.src));
memcpy(&ph.dst, ip6->ip6_dst.s6_addr, sizeof(ph.dst));
ph.len = htons(len);
memset(&ph.mbz, 0, sizeof(ph.mbz));
ph.proto = next_proto;
vec[0].ptr = (const uint8_t *) (void *) &ph;
vec[0].len = sizeof(ph);
vec[1].ptr = data;
vec[1].len = len;
return __in_cksum(vec, 2);
}
#endif /* CSUM_H */
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