net/ipv6/ip6_checksum.c

#include <net/ip.h>
#include <net/udp.h>
#include <net/udplite.h>
#include <asm/checksum.h>

#ifndef _HAVE_ARCH_IPV6_CSUM
__sum16 csum_ipv6_magic(const struct in6_addr *saddr,
			const struct in6_addr *daddr,
			__u32 len, unsigned short proto,
			__wsum csum)
{

	int carry;
	__u32 ulen;
	__u32 uproto;
	__u32 sum = (__force u32)csum;

	sum += (__force u32)saddr->s6_addr32[0];
	carry = (sum < (__force u32)saddr->s6_addr32[0]);
	sum += carry;

	sum += (__force u32)saddr->s6_addr32[1];
	carry = (sum < (__force u32)saddr->s6_addr32[1]);
	sum += carry;

	sum += (__force u32)saddr->s6_addr32[2];
	carry = (sum < (__force u32)saddr->s6_addr32[2]);
	sum += carry;

	sum += (__force u32)saddr->s6_addr32[3];
	carry = (sum < (__force u32)saddr->s6_addr32[3]);
	sum += carry;

	sum += (__force u32)daddr->s6_addr32[0];
	carry = (sum < (__force u32)daddr->s6_addr32[0]);
	sum += carry;

	sum += (__force u32)daddr->s6_addr32[1];
	carry = (sum < (__force u32)daddr->s6_addr32[1]);
	sum += carry;

	sum += (__force u32)daddr->s6_addr32[2];
	carry = (sum < (__force u32)daddr->s6_addr32[2]);
	sum += carry;

	sum += (__force u32)daddr->s6_addr32[3];
	carry = (sum < (__force u32)daddr->s6_addr32[3]);
	sum += carry;

	ulen = (__force u32)htonl((__u32) len);
	sum += ulen;
	carry = (sum < ulen);
	sum += carry;

	uproto = (__force u32)htonl(proto);
	sum += uproto;
	carry = (sum < uproto);
	sum += carry;

	return csum_fold((__force __wsum)sum);
}
EXPORT_SYMBOL(csum_ipv6_magic);
#endif

int udp6_csum_init(struct sk_buff *skb, struct udphdr *uh, int proto)
{
	int err;

	UDP_SKB_CB(skb)->partial_cov = 0;
	UDP_SKB_CB(skb)->cscov = skb->len;

	if (proto == IPPROTO_UDPLITE) {
		err = udplite_checksum_init(skb, uh);
		if (err)
			return err;
	}

	/* To support RFC 6936 (allow zero checksum in UDP/IPV6 for tunnels)
	 * we accept a checksum of zero here. When we find the socket
	 * for the UDP packet we'll check if that socket allows zero checksum
	 * for IPv6 (set by socket option).
	 */
	return skb_checksum_init_zero_check(skb, proto, uh->check,
					   ip6_compute_pseudo);
}
EXPORT_SYMBOL(udp6_csum_init);