| 1 | /* $NetBSD: in4_cksum.c,v 1.20 2014/11/30 18:15:41 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 1.20 2014/11/30 18:15:41 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 | |
| 55 | int |
| 56 | in4_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 | |