/*      $NetBSD: in6_cksum.c,v 1.28 2011/04/25 22:05:05 yamt 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: in6_cksum.c,v 1.28 2011/04/25 22:05:05 yamt Exp $");

#include <sys/param.h>
#include <sys/mbuf.h>
#include <netinet/in.h>
#include <netinet/ip6.h>

/*
 * Checksum of the IPv6 pseudo header.
 *
 * off is supposed to be the skipped IPv6 header, len is the payload size.
 */

int
in6_cksum(struct mbuf *m, u_int8_t nxt, uint32_t off, uint32_t len)
{
        union {
                uint16_t words[16];
                struct {
                        struct in6_addr ip6_src;
                        struct in6_addr ip6_dst;
                } addrs;
        } u;
        const struct in6_addr *in6_src;
        const struct in6_addr *in6_dst;
        const struct ip6_hdr *ip6;
        uint32_t sum;
        const uint16_t *w;
        const char *cp;

        if (nxt == 0)
                return cpu_in_cksum(m, len, off, 0);

        if (__predict_false(off < sizeof(struct ip6_hdr)))
                panic("in6_cksum: offset too short for IPv6 header");
        if (__predict_false(m->m_len < sizeof(struct ip6_hdr)))
                panic("in6_cksum: mbuf too short for IPv6 header");

        /*
         * Compute the equivalent of:
         * struct ip6_hdr_pseudo ip6;
         *
         * bzero(sizeof(*ip6));
         * ip6.ip6ph_nxt = nxt;
         * ip6.ip6ph_len = htonl(len);
         * ipv6.ip6ph_src = mtod(m, struct ip6_hdr *)->ip6_src;
         * in6_clearscope(&ip6->ip6ph_src);
         * ipv6.ip6ph_dst = mtod(m, struct ip6_hdr *)->ip6_dst;
         * in6_clearscope(&ip6->ip6ph_dst);
         * sum = one_add(&ip6);
         */

#if BYTE_ORDER == LITTLE_ENDIAN
        sum = ((len & 0xffff) + ((len >> 16) & 0xffff) + nxt) << 8;
#else
        sum = (len & 0xffff) + ((len >> 16) & 0xffff) + nxt;
#endif
        cp = mtod(m, const char *);
        w = (const uint16_t *)(cp + offsetof(struct ip6_hdr, ip6_src));
        ip6 = (const void *)cp;
        if (__predict_true((uintptr_t)w % 2 == 0)) {
                in6_src = &ip6->ip6_src;
                in6_dst = &ip6->ip6_dst;
        } else {
                memcpy(&u, &ip6->ip6_src, 32);
                w = u.words;
                in6_src = &u.addrs.ip6_src;
                in6_dst = &u.addrs.ip6_dst;
        }

        sum += w[0];
        if (!IN6_IS_SCOPE_EMBEDDABLE(in6_src))
                sum += w[1];
        sum += w[2];
        sum += w[3];
        sum += w[4];
        sum += w[5];
        sum += w[6];
        sum += w[7];
        w += 8;
        sum += w[0];
        if (!IN6_IS_SCOPE_EMBEDDABLE(in6_dst))
                sum += w[1];
        sum += w[2];
        sum += w[3];
        sum += w[4];
        sum += w[5];
        sum += w[6];
        sum += w[7];

        return cpu_in_cksum(m, len, off, sum);
}