/*      $NetBSD: cpu_in_cksum.c,v 1.2 2025/01/05 22:11:17 andvar Exp $  */
/*-
 * Copyright (c) 2008 Joerg Sonnenberger <joerg@NetBSD.org>.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: cpu_in_cksum.c,v 1.2 2025/01/05 22:11:17 andvar Exp $");

#include <sys/param.h>
#include <sys/mbuf.h>
#include <sys/systm.h>

#include <netinet/in.h>

/*
 * Taken from sys/netinet/cpu_in_cksum.c and modified to use old MD oc_cksum().
 */

/* in <m68k/m68k/oc_cksum.s> */
extern int oc_cksum(uint8_t *, int, uint32_t);

int
cpu_in_cksum(struct mbuf *m, int len, int off, uint32_t initial_sum)
{
        int mlen;
        uint32_t sum, partial;
        unsigned int final_acc;
        uint8_t *data;
        bool needs_swap, started_on_odd;

        KASSERT(len >= 0);
        KASSERT(off >= 0);

        needs_swap = false;
        started_on_odd = false;
        sum = (initial_sum >> 16) + (initial_sum & 0xffff);

        for (;;) {
                if (__predict_false(m == NULL)) {
                        printf("in_cksum: out of data\n");
                        return -1;
                }
                mlen = m->m_len;
                if (mlen > off) {
                        mlen -= off;
                        data = mtod(m, uint8_t *) + off;
                        goto post_initial_offset;
                }
                off -= mlen;
                if (len == 0)
                        break;
                m = m->m_next;
        }

        for (; len > 0; m = m->m_next) {
                if (__predict_false(m == NULL)) {
                        printf("in_cksum: out of data\n");
                        return -1;
                }
                mlen = m->m_len;
                data = mtod(m, uint8_t *);
 post_initial_offset:
                if (mlen == 0)
                        continue;
                if (mlen > len)
                        mlen = len;
                len -= mlen;

                partial = 0;
                if ((uintptr_t)data & 1) {
                        /* Align on word boundary */
                        started_on_odd = !started_on_odd;
                        /* We are big endian */
                        partial = *data;
                        ++data;
                        --mlen;
                }
                needs_swap = started_on_odd;

                /* A possible trailing odd byte is handled in oc_cksum() */
                if (mlen & 1)
                        started_on_odd = !started_on_odd;
                /* 16 bit word alignment is enough on m68k */
                partial = oc_cksum(data, mlen, partial);

                if (needs_swap)
                        partial = (partial << 8) + (partial >> 24);
                sum += (partial >> 16) + (partial & 0xffff);
                /*
                 * Reduce sum to allow potential byte swap
                 * in the next iteration without carry.
                 */
                sum = (sum >> 16) + (sum & 0xffff);
        }
        final_acc = ((sum >> 16) & 0xffff) + (sum & 0xffff);
        final_acc = (final_acc >> 16) + (final_acc & 0xffff);
        return ~final_acc & 0xffff;
}