/*      $OpenBSD: in_cksum.c,v 1.10 2022/02/01 15:30:10 miod Exp $      */
/*      $NetBSD: in_cksum.c,v 1.4 1996/11/13 21:13:06 cgd Exp $ */

/*
 * Copyright (c) 1988, 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 * Copyright (c) 1996
 *      Matt Thomas <matt@3am-software.com>
 *
 * 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.
 *
 *      @(#)in_cksum.c  8.1 (Berkeley) 6/10/93
 */

#include <sys/param.h>
#include <sys/mbuf.h>
#include <sys/systm.h>
#include <sys/socketvar.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>

/*
 * Checksum routine for Internet Protocol family headers
 *    (Portable Alpha 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 REDUCE32                                                          \
    {                                                                     \
        q_util.q = sum;                                                   \
        sum = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3];      \
    }
#define REDUCE16                                                          \
    {                                                                     \
        q_util.q = sum;                                                   \
        l_util.l = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3]; \
        sum = l_util.s[0] + l_util.s[1];                                  \
        ADDCARRY(sum);                                                    \
    }

static const u_int32_t in_masks[] = {
        /*0 bytes*/ /*1 byte*/  /*2 bytes*/ /*3 bytes*/
        0x00000000, 0x000000FF, 0x0000FFFF, 0x00FFFFFF, /* offset 0 */
        0x00000000, 0x0000FF00, 0x00FFFF00, 0xFFFFFF00, /* offset 1 */
        0x00000000, 0x00FF0000, 0xFFFF0000, 0xFFFF0000, /* offset 2 */
        0x00000000, 0xFF000000, 0xFF000000, 0xFF000000, /* offset 3 */
};

union l_util {
        u_int16_t s[2];
        u_int32_t l;
};
union q_util {
        u_int16_t s[4];
        u_int32_t l[2];
        u_int64_t q;
};

static u_int64_t
in_cksumdata(caddr_t buf, int len)
{
        const u_int32_t *lw = (u_int32_t *) buf;
        u_int64_t sum = 0;
        u_int64_t prefilled;
        int offset;
        union q_util q_util;

        if ((3 & (long) lw) == 0 && len == 20) {
             sum = (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3] + lw[4];
             REDUCE32;
             return sum;
        }

        if ((offset = 3 & (long) lw) != 0) {
                const u_int32_t *masks = in_masks + (offset << 2);
                lw = (u_int32_t *) (((long) lw) - offset);
                sum = *lw++ & masks[len >= 3 ? 3 : len];
                len -= 4 - offset;
                if (len <= 0) {
                        REDUCE32;
                        return sum;
                }
        }
#if 0
        /*
         * Force to cache line boundary.
         */
        offset = 32 - (0x1f & (long) lw);
        if (offset < 32 && len > offset) {
                len -= offset;
                if (4 & offset) {
                        sum += (u_int64_t) lw[0];
                        lw += 1;
                }
                if (8 & offset) {
                        sum += (u_int64_t) lw[0] + lw[1];
                        lw += 2;
                }
                if (16 & offset) {
                        sum += (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3];
                        lw += 4;
                }
        }
#endif
        /*
         * access prefilling to start load of next cache line.
         * then add current cache line
         * save result of prefilling for loop iteration.
         */
        prefilled = lw[0];
        while ((len -= 32) >= 4) {
                u_int64_t prefilling = lw[8];
                sum += prefilled + lw[1] + lw[2] + lw[3]
                        + lw[4] + lw[5] + lw[6] + lw[7];
                lw += 8;
                prefilled = prefilling;
        }
        if (len >= 0) {
                sum += prefilled + lw[1] + lw[2] + lw[3]
                        + lw[4] + lw[5] + lw[6] + lw[7];
                lw += 8;
        } else {
                len += 32;
        }
        while ((len -= 16) >= 0) {
                sum += (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3];
                lw += 4;
        }
        len += 16;
        while ((len -= 4) >= 0) {
                sum += (u_int64_t) *lw++;
        }
        len += 4;
        if (len > 0)
                sum += (u_int64_t) (in_masks[len] & *lw);
        REDUCE32;
        return sum;
}

int
in_cksum(struct mbuf *m, int len)
{
        u_int64_t sum = 0;
        int mlen = 0;
        int clen = 0;
        caddr_t addr;
        union l_util l_util;
        union q_util q_util;

        for (; m && len; m = m->m_next) {
                if (m->m_len == 0)
                        continue;
                mlen = m->m_len;
                if (len < mlen)
                        mlen = len;
                addr = mtod(m, caddr_t);
                if ((clen ^ (long) addr) & 1)
                    sum += in_cksumdata(addr, mlen) << 8;
                else
                    sum += in_cksumdata(addr, mlen);

                clen += mlen;
                len -= mlen;
        }
        REDUCE16;
        return (~sum & 0xffff);
}

int
in4_cksum(struct mbuf *m, u_int8_t nxt, int off, int len)
{
        u_int64_t sum = 0;
        int mlen = 0;
        int clen = 0;
        caddr_t addr;
        union q_util q_util;
        union l_util l_util;
        struct ipovly ipov;

        if (nxt != 0) {
#ifdef DEBUG
                /* pseudo header */
                if (off < sizeof(struct ipovly))
                        panic("in4_cksum: offset too short");
                if (m->m_len < sizeof(struct ip))
                        panic("in4_cksum: bad mbuf chain");
#endif

                ipov.ih_x1[8] = 0;
                ipov.ih_pr = nxt;
                ipov.ih_len = htons(len);
                ipov.ih_src = mtod(m, struct ip *)->ip_src;
                ipov.ih_dst = mtod(m, struct ip *)->ip_dst;

                /* first 8 bytes are zeroes */
                sum += in_cksumdata((caddr_t) &ipov + 8, sizeof(ipov) - 8);
        }

        /* skip over unnecessary part */
        while (m != NULL && off > 0) {
                if (m->m_len > off)
                        break;
                off -= m->m_len;
                m = m->m_next;
        }

        for (; m && len; m = m->m_next, off = 0) {
                if (m->m_len == 0)
                        continue;
                mlen = m->m_len - off;
                if (len < mlen)
                        mlen = len;
                addr = mtod(m, caddr_t) + off;
                if ((clen ^ (long) addr) & 1)
                        sum += in_cksumdata(addr, mlen) << 8;
                else
                        sum += in_cksumdata(addr, mlen);

                clen += mlen;
                len -= mlen;
        }
        REDUCE16;
        return (~sum & 0xffff);
}