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/* PASST - Plug A Simple Socket Transport
*
* util.c - Convenience helpers
*
* Author: Stefano Brivio <sbrivio@redhat.com>
* License: GPLv2
*
*/
#include <stdio.h>
#include <stdint.h>
#include <stddef.h>
#include <linux/ipv6.h>
#include <arpa/inet.h>
/**
* csum_fold() - Fold long sum for IP and TCP checksum
* @sum: Original long sum
*
* Return: 16-bit folded sum
*/
uint16_t csum_fold(uint32_t sum)
{
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
return sum;
}
/**
* csum_ipv4() - Calculate IPv4 checksum
* @buf: Packet buffer, L3 headers
* @len: Total L3 packet length
*
* Return: 16-bit IPv4-style checksum
*/
uint16_t csum_ip4(void *buf, size_t len)
{
uint32_t sum = 0;
uint16_t *p = buf;
size_t len1 = len / 2;
size_t off;
for (off = 0; off < len1; off++, p++)
sum += *p;
if (len % 2)
sum += *p & 0xff;
return ~csum_fold(sum);
}
unsigned char *ipv6_l4hdr(struct ipv6hdr *ip6h, uint8_t *proto)
{
int offset, len, hdrlen;
struct ipv6_opt_hdr *o;
uint8_t nh;
len = ntohs(ip6h->payload_len);
offset = 0;
while (offset < len) {
if (!offset) {
nh = ip6h->nexthdr;
hdrlen = sizeof(struct ipv6hdr);
} else {
nh = o->nexthdr;
hdrlen = (o->hdrlen + 1) * 8;
}
if (nh == 59)
return NULL;
if (nh == 0 || nh == 43 || nh == 44 || nh == 50 ||
nh == 51 || nh == 60 || nh == 135 || nh == 139 ||
nh == 140 || nh == 253 || nh == 254) {
offset += hdrlen;
o = (struct ipv6_opt_hdr *)(unsigned char *)ip6h +
offset;
} else {
*proto = nh;
return (unsigned char *)(ip6h + 1) + offset;
}
}
return NULL;
}
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