// SPDX-License-Identifier: GPL-2.0
#include <net/ip.h>
#include <net/ip6_checksum.h>
#include <net/udp.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, __u8 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

/* Function to set UDP checksum for an IPv6 UDP packet. This is intended
 * for the simple case like when setting the checksum for a UDP tunnel.
 */
void udp6_set_csum(bool nocheck, struct sk_buff *skb,
                   const struct in6_addr *saddr,
                   const struct in6_addr *daddr, int len)
{
        struct udphdr *uh = udp_hdr(skb);

        if (nocheck)
                uh->check = 0;
        else if (skb_is_gso(skb))
                uh->check = ~udp_v6_check(len, saddr, daddr, 0);
        else if (skb->ip_summed == CHECKSUM_PARTIAL) {
                uh->check = 0;
                uh->check = udp_v6_check(len, saddr, daddr, lco_csum(skb));
                if (uh->check == 0)
                        uh->check = CSUM_MANGLED_0;
        } else {
                skb->ip_summed = CHECKSUM_PARTIAL;
                skb->csum_start = skb_transport_header(skb) - skb->head;
                skb->csum_offset = offsetof(struct udphdr, check);
                uh->check = ~udp_v6_check(len, saddr, daddr, 0);
        }
}
EXPORT_SYMBOL(udp6_set_csum);