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      1 /*	$NetBSD: cpu_in_cksum.c,v 1.2 2025/01/05 22:11:17 andvar Exp $	*/
      2 /*-
      3  * Copyright (c) 2008 Joerg Sonnenberger <joerg (at) NetBSD.org>.
      4  * All rights reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  *
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in
     14  *    the documentation and/or other materials provided with the
     15  *    distribution.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     18  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     20  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
     21  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     22  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
     23  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     24  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     25  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     26  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     27  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     28  * SUCH DAMAGE.
     29  */
     30 
     31 #include <sys/cdefs.h>
     32 __KERNEL_RCSID(0, "$NetBSD: cpu_in_cksum.c,v 1.2 2025/01/05 22:11:17 andvar Exp $");
     33 
     34 #include <sys/param.h>
     35 #include <sys/mbuf.h>
     36 #include <sys/systm.h>
     37 
     38 #include <netinet/in.h>
     39 
     40 /*
     41  * Taken from sys/netinet/cpu_in_cksum.c and modified to use old MD oc_cksum().
     42  */
     43 
     44 /* in <m68k/m68k/oc_cksum.s> */
     45 extern int oc_cksum(uint8_t *, int, uint32_t);
     46 
     47 int
     48 cpu_in_cksum(struct mbuf *m, int len, int off, uint32_t initial_sum)
     49 {
     50 	int mlen;
     51 	uint32_t sum, partial;
     52 	unsigned int final_acc;
     53 	uint8_t *data;
     54 	bool needs_swap, started_on_odd;
     55 
     56 	KASSERT(len >= 0);
     57 	KASSERT(off >= 0);
     58 
     59 	needs_swap = false;
     60 	started_on_odd = false;
     61 	sum = (initial_sum >> 16) + (initial_sum & 0xffff);
     62 
     63 	for (;;) {
     64 		if (__predict_false(m == NULL)) {
     65 			printf("in_cksum: out of data\n");
     66 			return -1;
     67 		}
     68 		mlen = m->m_len;
     69 		if (mlen > off) {
     70 			mlen -= off;
     71 			data = mtod(m, uint8_t *) + off;
     72 			goto post_initial_offset;
     73 		}
     74 		off -= mlen;
     75 		if (len == 0)
     76 			break;
     77 		m = m->m_next;
     78 	}
     79 
     80 	for (; len > 0; m = m->m_next) {
     81 		if (__predict_false(m == NULL)) {
     82 			printf("in_cksum: out of data\n");
     83 			return -1;
     84 		}
     85 		mlen = m->m_len;
     86 		data = mtod(m, uint8_t *);
     87  post_initial_offset:
     88 		if (mlen == 0)
     89 			continue;
     90 		if (mlen > len)
     91 			mlen = len;
     92 		len -= mlen;
     93 
     94 		partial = 0;
     95 		if ((uintptr_t)data & 1) {
     96 			/* Align on word boundary */
     97 			started_on_odd = !started_on_odd;
     98 			/* We are big endian */
     99 			partial = *data;
    100 			++data;
    101 			--mlen;
    102 		}
    103 		needs_swap = started_on_odd;
    104 
    105 		/* A possible trailing odd byte is handled in oc_cksum() */
    106 		if (mlen & 1)
    107 			started_on_odd = !started_on_odd;
    108 		/* 16 bit word alignment is enough on m68k */
    109 		partial = oc_cksum(data, mlen, partial);
    110 
    111 		if (needs_swap)
    112 			partial = (partial << 8) + (partial >> 24);
    113 		sum += (partial >> 16) + (partial & 0xffff);
    114 		/*
    115 		 * Reduce sum to allow potential byte swap
    116 		 * in the next iteration without carry.
    117 		 */
    118 		sum = (sum >> 16) + (sum & 0xffff);
    119 	}
    120 	final_acc = ((sum >> 16) & 0xffff) + (sum & 0xffff);
    121 	final_acc = (final_acc >> 16) + (final_acc & 0xffff);
    122 	return ~final_acc & 0xffff;
    123 }
    124