1 /* 2 * Copyright 2011 Daniel Drown 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 * 16 * checksum.c - ipv4/ipv6 checksum calculation 17 */ 18 #include <netinet/in.h> 19 #include <netinet/ip.h> 20 #include <netinet/ip_icmp.h> 21 #include <netinet/udp.h> 22 #include <netinet/tcp.h> 23 #include <netinet/ip6.h> 24 #include <netinet/icmp6.h> 25 #include <linux/icmp.h> 26 27 #include "checksum.h" 28 29 /* function: ip_checksum_add 30 * adds data to a checksum 31 * current - the current checksum (or 0 to start a new checksum) 32 * data - the data to add to the checksum 33 * len - length of data 34 */ 35 uint32_t ip_checksum_add(uint32_t current, const void *data, int len) { 36 uint32_t checksum = current; 37 int left = len; 38 const uint16_t *data_16 = data; 39 40 while(left > 1) { 41 checksum += *data_16; 42 data_16++; 43 left -= 2; 44 } 45 if(left) { 46 checksum += *(uint8_t *)data_16; 47 } 48 49 return checksum; 50 } 51 52 /* function: ip_checksum_finish 53 * close the checksum 54 * temp_sum - sum from ip_checksum_add 55 */ 56 uint16_t ip_checksum_finish(uint32_t temp_sum) { 57 while(temp_sum > 0xffff) 58 temp_sum = (temp_sum >> 16) + (temp_sum & 0xFFFF); 59 60 temp_sum = (~temp_sum) & 0xffff; 61 62 return temp_sum; 63 } 64 65 /* function: ip_checksum 66 * combined ip_checksum_add and ip_checksum_finish 67 * data - data to checksum 68 * len - length of data 69 */ 70 uint16_t ip_checksum(const void *data, int len) { 71 uint32_t temp_sum; 72 73 temp_sum = ip_checksum_add(0,data,len); 74 return ip_checksum_finish(temp_sum); 75 } 76 77 /* function: ipv6_pseudo_header_checksum 78 * calculate the pseudo header checksum for use in tcp/udp/icmp headers 79 * current - the current checksum or 0 to start a new checksum 80 * ip6 - the ipv6 header 81 * len - the transport length (transport header + payload) 82 */ 83 uint32_t ipv6_pseudo_header_checksum(uint32_t current, const struct ip6_hdr *ip6, uint16_t len) { 84 uint32_t checksum_len, checksum_next; 85 86 checksum_len = htonl((uint32_t) len); 87 checksum_next = htonl(ip6->ip6_nxt); 88 89 current = ip_checksum_add(current, &(ip6->ip6_src), sizeof(struct in6_addr)); 90 current = ip_checksum_add(current, &(ip6->ip6_dst), sizeof(struct in6_addr)); 91 current = ip_checksum_add(current, &checksum_len, sizeof(checksum_len)); 92 current = ip_checksum_add(current, &checksum_next, sizeof(checksum_next)); 93 94 return current; 95 } 96 97 /* function: ipv4_pseudo_header_checksum 98 * calculate the pseudo header checksum for use in tcp/udp headers 99 * current - the current checksum or 0 to start a new checksum 100 * ip - the ipv4 header 101 * len - the transport length (transport header + payload) 102 */ 103 uint32_t ipv4_pseudo_header_checksum(uint32_t current, const struct iphdr *ip, uint16_t len) { 104 uint16_t temp_protocol, temp_length; 105 106 temp_protocol = htons(ip->protocol); 107 temp_length = htons(len); 108 109 current = ip_checksum_add(current, &(ip->saddr), sizeof(uint32_t)); 110 current = ip_checksum_add(current, &(ip->daddr), sizeof(uint32_t)); 111 current = ip_checksum_add(current, &temp_protocol, sizeof(uint16_t)); 112 current = ip_checksum_add(current, &temp_length, sizeof(uint16_t)); 113 114 return current; 115 } 116
