/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * 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.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT 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 PROJECT 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.
 *
 *      $KAME: in6_cksum.c,v 1.10 2000/12/03 00:53:59 itojun Exp $
 */

/*-
 * Copyright (c) 1988, 1992, 1993
 *      The Regents of the University of California.  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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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/param.h>
#include <sys/mbuf.h>
#include <sys/systm.h>
#include <netinet/in.h>
#include <netinet/ip6.h>
#include <netinet6/scope6_var.h>

/*
 * Checksum routine for Internet Protocol family headers (Portable Version).
 *
 * This routine is very heavily used in the network
 * code and should be modified for each CPU to be as fast as possible.
 */

#define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; (void)ADDCARRY(sum);}

union l_util {
        uint16_t        s[2];
        uint32_t        l;
};

union s_util {
        uint8_t         c[2];
        uint16_t        s;
};

static int
_in6_cksum_pseudo(struct ip6_hdr *ip6, uint32_t len, uint8_t nxt, uint16_t csum)
{
        int sum;
        uint16_t scope, *w;
        union {
                u_int16_t phs[4];
                struct {
                        u_int32_t       ph_len;
                        u_int8_t        ph_zero[3];
                        u_int8_t        ph_nxt;
                } __packed ph;
        } uph;

        sum = csum;

        /*
         * First create IP6 pseudo header and calculate a summary.
         */
        uph.ph.ph_len = htonl(len);
        uph.ph.ph_zero[0] = uph.ph.ph_zero[1] = uph.ph.ph_zero[2] = 0;
        uph.ph.ph_nxt = nxt;

        /* Payload length and upper layer identifier. */
        sum += uph.phs[0];  sum += uph.phs[1];
        sum += uph.phs[2];  sum += uph.phs[3];

        /* IPv6 source address. */
        scope = in6_getscope(&ip6->ip6_src);
        w = (u_int16_t *)&ip6->ip6_src;
        sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
        sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
        if (scope != 0)
                sum -= scope;

        /* IPv6 destination address. */
        scope = in6_getscope(&ip6->ip6_dst);
        w = (u_int16_t *)&ip6->ip6_dst;
        sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
        sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
        if (scope != 0)
                sum -= scope;

        return (sum);
}

int
in6_cksum_pseudo(struct ip6_hdr *ip6, uint32_t len, uint8_t nxt, uint16_t csum)
{
        union l_util l_util;
        int sum;

        sum = _in6_cksum_pseudo(ip6, len, nxt, csum);
        REDUCE;
        return (sum);
}

static int
in6_cksumdata(void *data, int *lenp, uint8_t *residp, int rlen)
{
        union l_util l_util;
        union s_util s_util;
        uint16_t *w;
        int len, sum;
        bool byte_swapped;

        KASSERT(*lenp >= 0, ("%s: negative len %d", __func__, *lenp));
        KASSERT(rlen == 0 || rlen == 1, ("%s: rlen %d", __func__, rlen));

        len = *lenp;
        sum = 0;

        if (len == 0) {
                len = rlen;
                goto out;
        }

        byte_swapped = false;
        w = data;

        /*
         * Do we have a residual byte left over from the previous buffer?
         */
        if (rlen == 1) {
                s_util.c[0] = *residp;
                s_util.c[1] = *(uint8_t *)w;
                sum += s_util.s;
                w = (uint16_t *)((uint8_t *)w + 1);
                len--;
                rlen = 0;
        }

        /*
         * Force to even boundary.
         */
        if ((1 & (uintptr_t)w) && len > 0) {
                REDUCE;
                sum <<= 8;
                s_util.c[0] = *(uint8_t *)w;
                w = (uint16_t *)((uint8_t *)w + 1);
                len--;
                byte_swapped = true;
        }

        /*
         * Unroll the loop to make overhead from branches &c small.
         */
        while ((len -= 32) >= 0) {
                sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
                sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
                sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
                sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
                w += 16;
        }
        len += 32;
        while ((len -= 8) >= 0) {
                sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
                w += 4;
        }
        len += 8;
        if (len == 0 && !byte_swapped)
                goto out;
        REDUCE;
        while ((len -= 2) >= 0) {
                sum += *w++;
        }
        if (byte_swapped) {
                REDUCE;
                sum <<= 8;
                if (len == -1) {
                        s_util.c[1] = *(uint8_t *)w;
                        sum += s_util.s;
                } else /* len == -2 */
                        *residp = s_util.c[0];
                len++;
        } else if (len == -1)
                *residp = *(uint8_t *)w;
out:
        *lenp = len & 1;
        return (sum);
}

struct in6_cksum_partial_arg {
        int     sum;
        int     rlen;
        uint8_t resid;
};

static int
in6_cksum_partial_one(void *_arg, void *data, u_int len)
{
        struct in6_cksum_partial_arg *arg = _arg;

        arg->sum += in6_cksumdata(data, &len, &arg->resid, arg->rlen);
        arg->rlen = len;
        return (0);
}

/*
 * m MUST contain a contiguous IP6 header.
 * off_l3 is an offset where ipv6 header starts.
 * off_l4 is an offset where TCP/UDP/ICMP6 header starts.
 * len is a total length of a transport segment.
 * (e.g. TCP header + TCP payload)
 * cov is the number of bytes to be taken into account for the checksum
 */
int
in6_cksum_partial_l2(struct mbuf *m, uint8_t nxt, uint32_t off_l3,
    uint32_t off_l4, uint32_t len, uint32_t cov)
{
        struct in6_cksum_partial_arg arg;
        union l_util l_util;
        union s_util s_util;
        struct ip6_hdr *ip6;
        uint16_t *w, scope;
        int sum;
        union {
                uint16_t phs[4];
                struct {
                        uint32_t        ph_len;
                        uint8_t         ph_zero[3];
                        uint8_t         ph_nxt;
                } __packed ph;
        } uph;

        /* Sanity check. */
        KASSERT(m->m_pkthdr.len >= off_l4 + len,
            ("%s: mbuf len (%d) < off(%d)+len(%d)",
            __func__, m->m_pkthdr.len, off_l4, len));
        KASSERT(m->m_len >= off_l3 + sizeof(*ip6),
            ("%s: mbuf len %d < sizeof(ip6)", __func__, m->m_len));

        /*
         * First create IP6 pseudo header and calculate a summary.
         */
        uph.ph.ph_len = htonl(len);
        uph.ph.ph_zero[0] = uph.ph.ph_zero[1] = uph.ph.ph_zero[2] = 0;
        uph.ph.ph_nxt = nxt;

        /* Payload length and upper layer identifier. */
        sum = uph.phs[0];  sum += uph.phs[1];
        sum += uph.phs[2];  sum += uph.phs[3];

        ip6 = mtodo(m, off_l3);

        /* IPv6 source address. */
        scope = in6_getscope(&ip6->ip6_src);
        w = (uint16_t *)&ip6->ip6_src;
        sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
        sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
        if (scope != 0)
                sum -= scope;

        /* IPv6 destination address. */
        scope = in6_getscope(&ip6->ip6_dst);
        w = (uint16_t *)&ip6->ip6_dst;
        sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
        sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
        if (scope != 0)
                sum -= scope;

        /*
         * Loop over the rest of the mbuf chain and compute the rest of the
         * checksum.  m_apply() handles unmapped mbufs.
         */
        arg.sum = sum;
        arg.rlen = 0;
        (void)m_apply(m, off_l4, cov, in6_cksum_partial_one, &arg);
        sum = arg.sum;

        /*
         * Handle a residual byte.
         */
        if (arg.rlen == 1) {
                s_util.c[0] = arg.resid;
                s_util.c[1] = 0;
                sum += s_util.s;
        }
        REDUCE;
        return (~sum & 0xffff);
}

int
in6_cksum_partial(struct mbuf *m, uint8_t nxt, uint32_t off, uint32_t len,
    uint32_t cov)
{
        return (in6_cksum_partial_l2(m, nxt, 0, off, len, cov));
}

int
in6_cksum(struct mbuf *m, uint8_t nxt, uint32_t off, uint32_t len)
{
        return (in6_cksum_partial(m, nxt, off, len, len));
}