1 /* $NetBSD: in4_cksum.c,v 1.17 2008/02/12 13:05:55 joerg 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 1.17 2008/02/12 13:05:55 joerg 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 47 int 48 in4_cksum(struct mbuf *m, u_int8_t nxt, int off, int len) 49 { 50 uint32_t sum; 51 uint16_t *w; 52 53 if (__predict_false(off < sizeof(struct ip))) 54 panic("in4_cksum: offset too short for IP header"); 55 if (__predict_false(m->m_len < sizeof(struct ip))) 56 panic("in4_cksum: mbuf too short for IP header"); 57 58 if (nxt == 0) 59 return cpu_in_cksum(m, len, off, 0); 60 61 /* 62 * Compute the equivalent of: 63 * struct ipovly ip; 64 * 65 * bzero(sizeof(*ip)); 66 * ip.ih_pr = nxt; 67 * ip.ip_len = htons(len); 68 * ip.ih_src = mtod(m, struct ip *)->ip_src; 69 * ip.ih_dst = mtod(m, struct ip *)->ip_dst; 70 * sum = one_add(&ip); 71 */ 72 73 #if BYTE_ORDER == LITTLE_ENDIAN 74 sum = ((len & 0xffff) + nxt) << 8; 75 #else 76 sum = (len & 0xffff) + nxt; 77 #endif 78 w = (uint16_t *)(mtod(m, char *) + offsetof(struct ip, ip_src)); 79 if (__predict_true((uintptr_t)w % 2 == 0)) { 80 sum += w[0]; 81 sum += w[1]; 82 sum += w[2]; 83 sum += w[3]; 84 } else { 85 uint32_t partial; 86 w = (void *)((uintptr_t)w - 1); 87 #if BYTE_ORDER == LITTLE_ENDIAN 88 partial = w[0] & 0xff00; 89 #else 90 partial = w[0] & 0x00ff; 91 #endif 92 partial += w[1]; 93 partial += w[2]; 94 partial += w[3]; 95 #if BYTE_ORDER == LITTLE_ENDIAN 96 partial += w[4] & 0x00ff; 97 #else 98 partial += w[4] & 0xff00; 99 #endif 100 sum += partial << 8; 101 } 102 103 return cpu_in_cksum(m, len, off, sum); 104 } 105