// SPDX-License-Identifier: GPL-2.0
#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, __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

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;

                if (UDP_SKB_CB(skb)->partial_cov) {
                        skb->csum = ip6_compute_pseudo(skb, proto);
                        return 0;
                }
        }

        /* 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).
         *
         * Note, we are only interested in != 0 or == 0, thus the
         * force to int.
         */
        err = (__force int)skb_checksum_init_zero_check(skb, proto, uh->check,
                                                        ip6_compute_pseudo);
        if (err)
                return err;

        if (skb->ip_summed == CHECKSUM_COMPLETE && !skb->csum_valid) {
                /* If SW calculated the value, we know it's bad */
                if (skb->csum_complete_sw)
                        return 1;

                /* HW says the value is bad. Let's validate that.
                 * skb->csum is no longer the full packet checksum,
                 * so don't treat is as such.
                 */
                skb_checksum_complete_unset(skb);
        }

        return 0;
}
EXPORT_SYMBOL(udp6_csum_init);

/* 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);