1/* $NetBSD: in4_cksum.c,v 1.19 2013/03/12 21:54:36 christos Exp $ */ 2 3/*- 4 * Copyright (c) 2008 Joerg Sonnenberger <joerg@NetBSD.org>. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 19 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 21 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 22 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 23 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 24 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 25 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 26 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 27 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 28 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32#include <sys/cdefs.h> 33__KERNEL_RCSID(0, "$NetBSD: in4_cksum.c,v 1.19 2013/03/12 21:54:36 christos Exp $"); 34 35#include <sys/param.h> 36#include <sys/mbuf.h> 37#include <netinet/in.h> 38#include <netinet/in_systm.h> 39#include <netinet/ip.h> 40 41/* 42 * Checksum of the IPv4 pseudo header. 43 * 44 * off is supposed to be the skipped IPv4 header, len is the payload size. 45 */ 46#ifdef DIAGNOSTIC 47#define PANIC(a,...) panic(a, __VA_ARGS__) 48#else 49#define PANIC(a,...) do { \ 50 printf(a, __VA_ARGS__); \ 51 return -1; \ 52} while (/*CONSTCOND*/0) 53#endif 54 55int 56in4_cksum(struct mbuf *m, u_int8_t nxt, int off, int len) 57{ 58 uint32_t sum; 59 uint16_t *w; 60 61 if (__predict_false(m->m_len < sizeof(struct ip))) 62 PANIC("%s: mbuf %d too short for IP header %zu", __func__, 63 m->m_len, sizeof(struct ip)); 64 65 if (nxt == 0) 66 return cpu_in_cksum(m, len, off, 0); 67 68 if (__predict_false(off < sizeof(struct ip))) 69 PANIC("%s: offset %d too short for IP header %zu", __func__, 70 off, sizeof(struct ip)); 71 72 /* 73 * Compute the equivalent of: 74 * struct ipovly ip; 75 * 76 * bzero(sizeof(*ip)); 77 * ip.ih_pr = nxt; 78 * ip.ip_len = htons(len); 79 * ip.ih_src = mtod(m, struct ip *)->ip_src; 80 * ip.ih_dst = mtod(m, struct ip *)->ip_dst; 81 * sum = one_add(&ip); 82 */ 83 84#if BYTE_ORDER == LITTLE_ENDIAN 85 sum = ((len & 0xffff) + nxt) << 8; 86#else 87 sum = (len & 0xffff) + nxt; 88#endif 89 w = (uint16_t *)(mtod(m, char *) + offsetof(struct ip, ip_src)); 90 if (__predict_true((uintptr_t)w % 2 == 0)) { 91 sum += w[0]; 92 sum += w[1]; 93 sum += w[2]; 94 sum += w[3]; 95 } else { 96 uint32_t partial; 97 w = (void *)((uintptr_t)w - 1); 98#if BYTE_ORDER == LITTLE_ENDIAN 99 partial = w[0] & 0xff00; 100#else 101 partial = w[0] & 0x00ff; 102#endif 103 partial += w[1]; 104 partial += w[2]; 105 partial += w[3]; 106#if BYTE_ORDER == LITTLE_ENDIAN 107 partial += w[4] & 0x00ff; 108#else 109 partial += w[4] & 0xff00; 110#endif 111 sum += partial << 8; 112 } 113 114 return cpu_in_cksum(m, len, off, sum); 115} 116