Harald Welte | d46bcd2 | 2017-08-08 23:27:22 +0200 | [diff] [blame] | 1 | /* |
| 2 | * |
| 3 | * INET An implementation of the TCP/IP protocol suite for the LINUX |
| 4 | * operating system. INET is implemented using the BSD Socket |
| 5 | * interface as the means of communication with the user level. |
| 6 | * |
| 7 | * IP/TCP/UDP checksumming routines |
| 8 | * |
| 9 | * Authors: Jorge Cwik, <jorge@laser.satlink.net> |
| 10 | * Arnt Gulbrandsen, <agulbra@nvg.unit.no> |
| 11 | * Tom May, <ftom@netcom.com> |
| 12 | * Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de> |
| 13 | * Lots of code moved from tcp.c and ip.c; see those files |
| 14 | * for more names. |
| 15 | * |
| 16 | * 03/02/96 Jes Sorensen, Andreas Schwab, Roman Hodek: |
| 17 | * Fixed some nasty bugs, causing some horrible crashes. |
| 18 | * A: At some points, the sum (%0) was used as |
| 19 | * length-counter instead of the length counter |
| 20 | * (%1). Thanks to Roman Hodek for pointing this out. |
| 21 | * B: GCC seems to mess up if one uses too many |
| 22 | * data-registers to hold input values and one tries to |
| 23 | * specify d0 and d1 as scratch registers. Letting gcc |
| 24 | * choose these registers itself solves the problem. |
| 25 | * |
| 26 | * This program is free software; you can redistribute it and/or |
| 27 | * modify it under the terms of the GNU General Public License |
| 28 | * as published by the Free Software Foundation; either version |
| 29 | * 2 of the License, or (at your option) any later version. |
| 30 | */ |
| 31 | |
| 32 | /* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access |
| 33 | kills, so most of the assembly has to go. */ |
| 34 | |
| 35 | #if defined(__FreeBSD__) |
| 36 | #define _KERNEL /* needed on FreeBSD 10.x for s6_addr32 */ |
| 37 | #include <sys/types.h> |
| 38 | #include <netinet/in.h> |
| 39 | #include <sys/endian.h> |
| 40 | #endif |
| 41 | |
| 42 | #include "checksum.h" |
| 43 | #include <arpa/inet.h> |
| 44 | |
| 45 | static inline unsigned short from32to16(unsigned int x) |
| 46 | { |
| 47 | /* add up 16-bit and 16-bit for 16+c bit */ |
| 48 | x = (x & 0xffff) + (x >> 16); |
| 49 | /* add up carry.. */ |
| 50 | x = (x & 0xffff) + (x >> 16); |
| 51 | return x; |
| 52 | } |
| 53 | |
| 54 | static unsigned int do_csum(const unsigned char *buff, int len) |
| 55 | { |
| 56 | int odd; |
| 57 | unsigned int result = 0; |
| 58 | |
| 59 | if (len <= 0) |
| 60 | goto out; |
| 61 | odd = 1 & (unsigned long) buff; |
| 62 | if (odd) { |
| 63 | #if BYTE_ORDER == LITTLE_ENDIAN |
| 64 | result += (*buff << 8); |
| 65 | #else |
| 66 | result = *buff; |
| 67 | #endif |
| 68 | len--; |
| 69 | buff++; |
| 70 | } |
| 71 | if (len >= 2) { |
| 72 | if (2 & (unsigned long) buff) { |
| 73 | result += *(unsigned short *) buff; |
| 74 | len -= 2; |
| 75 | buff += 2; |
| 76 | } |
| 77 | if (len >= 4) { |
| 78 | const unsigned char *end = buff + ((unsigned)len & ~3); |
| 79 | unsigned int carry = 0; |
| 80 | do { |
| 81 | unsigned int w = *(unsigned int *) buff; |
| 82 | buff += 4; |
| 83 | result += carry; |
| 84 | result += w; |
| 85 | carry = (w > result); |
| 86 | } while (buff < end); |
| 87 | result += carry; |
| 88 | result = (result & 0xffff) + (result >> 16); |
| 89 | } |
| 90 | if (len & 2) { |
| 91 | result += *(unsigned short *) buff; |
| 92 | buff += 2; |
| 93 | } |
| 94 | } |
| 95 | if (len & 1) |
| 96 | #if BYTE_ORDER == LITTLE_ENDIAN |
| 97 | result += *buff; |
| 98 | #else |
| 99 | result += (*buff << 8); |
| 100 | #endif |
| 101 | result = from32to16(result); |
| 102 | if (odd) |
| 103 | result = ((result >> 8) & 0xff) | ((result & 0xff) << 8); |
| 104 | out: |
| 105 | return result; |
| 106 | } |
| 107 | |
| 108 | /* |
| 109 | * This is a version of ip_compute_csum() optimized for IP headers, |
| 110 | * which always checksum on 4 octet boundaries. |
| 111 | */ |
| 112 | uint16_t ip_fast_csum(const void *iph, unsigned int ihl) |
| 113 | { |
| 114 | return (uint16_t)~do_csum(iph, ihl*4); |
| 115 | } |
| 116 | |
| 117 | /* |
| 118 | * computes the checksum of a memory block at buff, length len, |
| 119 | * and adds in "sum" (32-bit) |
| 120 | * |
| 121 | * returns a 32-bit number suitable for feeding into itself |
| 122 | * or csum_tcpudp_magic |
| 123 | * |
| 124 | * this function must be called with even lengths, except |
| 125 | * for the last fragment, which may be odd |
| 126 | * |
| 127 | * it's best to have buff aligned on a 32-bit boundary |
| 128 | */ |
| 129 | uint32_t csum_partial(const void *buff, int len, uint32_t wsum) |
| 130 | { |
| 131 | unsigned int sum = (unsigned int)wsum; |
| 132 | unsigned int result = do_csum(buff, len); |
| 133 | |
| 134 | /* add in old sum, and carry.. */ |
| 135 | result += sum; |
| 136 | if (sum > result) |
| 137 | result += 1; |
| 138 | return (uint32_t)result; |
| 139 | } |
| 140 | |
| 141 | /* |
| 142 | * this routine is used for miscellaneous IP-like checksums, mainly |
| 143 | * in icmp.c |
| 144 | */ |
| 145 | uint16_t ip_compute_csum(const void *buff, int len) |
| 146 | { |
| 147 | return (uint16_t)~do_csum(buff, len); |
| 148 | } |
| 149 | |
| 150 | uint16_t csum_ipv6_magic(const struct in6_addr *saddr, |
| 151 | const struct in6_addr *daddr, |
| 152 | uint32_t len, uint8_t proto, uint32_t csum) |
| 153 | { |
| 154 | int carry; |
| 155 | uint32_t ulen; |
| 156 | uint32_t uproto; |
| 157 | uint32_t sum = (uint32_t)csum; |
| 158 | |
| 159 | sum += (uint32_t)saddr->s6_addr32[0]; |
| 160 | carry = (sum < (uint32_t)saddr->s6_addr32[0]); |
| 161 | sum += carry; |
| 162 | |
| 163 | sum += (uint32_t)saddr->s6_addr32[1]; |
| 164 | carry = (sum < (uint32_t)saddr->s6_addr32[1]); |
| 165 | sum += carry; |
| 166 | |
| 167 | sum += (uint32_t)saddr->s6_addr32[2]; |
| 168 | carry = (sum < (uint32_t)saddr->s6_addr32[2]); |
| 169 | sum += carry; |
| 170 | |
| 171 | sum += (uint32_t)saddr->s6_addr32[3]; |
| 172 | carry = (sum < (uint32_t)saddr->s6_addr32[3]); |
| 173 | sum += carry; |
| 174 | |
| 175 | sum += (uint32_t)daddr->s6_addr32[0]; |
| 176 | carry = (sum < (uint32_t)daddr->s6_addr32[0]); |
| 177 | sum += carry; |
| 178 | |
| 179 | sum += (uint32_t)daddr->s6_addr32[1]; |
| 180 | carry = (sum < (uint32_t)daddr->s6_addr32[1]); |
| 181 | sum += carry; |
| 182 | |
| 183 | sum += (uint32_t)daddr->s6_addr32[2]; |
| 184 | carry = (sum < (uint32_t)daddr->s6_addr32[2]); |
| 185 | sum += carry; |
| 186 | |
| 187 | sum += (uint32_t)daddr->s6_addr32[3]; |
| 188 | carry = (sum < (uint32_t)daddr->s6_addr32[3]); |
| 189 | sum += carry; |
| 190 | |
| 191 | ulen = (uint32_t)htonl((uint32_t) len); |
| 192 | sum += ulen; |
| 193 | carry = (sum < ulen); |
| 194 | sum += carry; |
| 195 | |
| 196 | uproto = (uint32_t)htonl(proto); |
| 197 | sum += uproto; |
| 198 | carry = (sum < uproto); |
| 199 | sum += carry; |
| 200 | |
| 201 | return csum_fold((uint32_t)sum); |
| 202 | } |
| 203 | |
| 204 | /* fold a partial checksum */ |
| 205 | uint16_t csum_fold(uint32_t csum) |
| 206 | { |
| 207 | uint32_t sum = (uint32_t)csum; |
| 208 | sum = (sum & 0xffff) + (sum >> 16); |
| 209 | sum = (sum & 0xffff) + (sum >> 16); |
| 210 | return (uint16_t)~sum; |
| 211 | } |