145 lines
4.4 KiB
C++
145 lines
4.4 KiB
C++
#include "ipv6.h"
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#include "udp.h"
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namespace ipv6 {
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/******** costants ********/
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const IPv6Addr ALL_NODES_ADDRESS("\xff\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01"); /* ff02::1 */
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/******** FUNCTIONS *******/
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uint16_t compute_checksum(const IPv6Addr* src_addr, const IPv6Addr* dst_addr, uint8_t next_header, int upper_len, const char* payload, int len) {
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char buffer[LEN];
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uint32_t total;
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uint16_t* ptr;
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int words;
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int i = len;
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/* prepare buffer with all data to checksum:
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- the actual payload
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- the pseudo ipv6 header
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*/
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/* actual payload */
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memcpy(buffer, payload, len);
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if (len % 2) { /* pad with 0 if length is odd */
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buffer[len] = 0;
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i++;
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}
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/* pseudo ipv6 header -- see RFC 2460, Section 8.1 */
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memcpy(buffer + i, src_addr, 16); i += 16;
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memcpy(buffer + i, dst_addr, 16); i += 16;
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memset(buffer + i, 0, 3); i+= 3; /* first 3 bytes always 0, because len always < 256 */
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buffer[i] = upper_len & 0xff; i += 1;
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memset(buffer + i, 0, 3); i += 3; /* zero, as per-standard */
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buffer[i] = next_header; i += 1;
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/* do computation */
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total = 0;
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ptr = (uint16_t*)buffer;
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words = (i + 1) / 2;
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while (words--) total += *ptr++;
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while (total & 0xffff0000) {
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total = (total >> 16) + (total & 0xffff);
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}
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return ~((uint16_t) total);
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}
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/******** IPv6Addr ********/
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IPv6Addr::IPv6Addr() {;}
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IPv6Addr::IPv6Addr(const char* address) {
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memcpy(this->address, address, 16);
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}
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/******** IPv6Packet ********/
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IPv6Packet::IPv6Packet() {
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memset(packet, 0, LEN);
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*(packet) = 0x60; /* IP version 6 */
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*(packet + 7) = 64; /* hop limit / ttl */
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}
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IPv6Packet::IPv6Packet(const char* buffer, int len) {
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memcpy(this->packet, buffer, len);
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}
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void IPv6Packet::setNextHeader(uint8_t next_header) {
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*(packet + 6) = next_header;
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}
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void IPv6Packet::setSrcAddress(const IPv6Addr* address) {
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memcpy(packet + 8, address, 16);
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}
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void IPv6Packet::setDstAddress(const IPv6Addr* address) {
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memcpy(packet + 24, address, 16);
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}
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void IPv6Packet::setFlow(const char* flow) {
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/* three bytes
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4 most significant bits are ignored
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because only 20 bits can be used */
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*(packet + 1) = (*(packet + 1)) | (flow[0] & 0x0f); /* pay attention to TC field */
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memcpy(packet + 2, flow + 1, 2);
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}
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void IPv6Packet::setPayload(char* payload, int len) {
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*(packet + 4 + 0) = len >> 8;
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*(packet + 4 + 1) = len & 0xff;
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memcpy(packet + 40, payload, len); /* payload */
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}
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void IPv6Packet::doAction() {
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/* if destination is my address, or destination is "all nodes" address, then... */
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if ((memcmp(&(ALL_NODES_ADDRESS), packet + 24, 16) == 0) || (memcmp(&(coppino::address), packet + 24, 16) == 0)) {
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int len = ((*(packet + 4)) << 8) + (*(packet + 5));
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switch(*(packet + 6)) { /* next header */
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case NH_ICMP:
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handleICMP((IPv6Addr*)(packet + 8), (IPv6Addr*)(packet + 24), packet + 1, packet + 40, len);
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break;
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case NH_UDP:
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udp::handleUDP((IPv6Addr*)(packet + 8), (IPv6Addr*)(packet + 24), packet + 1, packet + 40, len);
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break;
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default:
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/* no other protocols are known here, sorry :-) */
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break;
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}
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}
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}
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void handleICMP(const IPv6Addr* src_addr, const IPv6Addr* dst_addr, const char* flow, char* packet, int len) {
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uint8_t type = *(packet);
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if (type == ICMP_ECHO_REQUEST_TYPE) { /* if it is ICMPv6 Echo Request, then... */
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/* compute checksum, and assert validity of incoming message */
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char received_checksum[2];
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memcpy(received_checksum, packet + 2, 2);
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memset(packet + 2, 0, 2); /* zero-checksum */
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uint16_t computed_checksum = compute_checksum(src_addr, dst_addr, NH_ICMP, len, packet, len);
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if (memcmp(&computed_checksum, received_checksum, 2) == 0) { /* if checksum is valid, then... */
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/* Build an echo reply:
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* the reply has the same exact format of the request,
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* except for Type and Checksum */
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*(packet) = ICMP_ECHO_REPLY_TYPE;
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memset(packet + 2, 0, 2); /* zero-checksum */
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uint16_t checksum = compute_checksum(src_addr, dst_addr, NH_ICMP, len, packet, len);
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memcpy(packet + 2, &checksum, 2);
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IPv6Packet reply_packet;
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reply_packet.setPayload(packet, len);
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reply_packet.setFlow(flow);
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reply_packet.setSrcAddress(dst_addr);
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reply_packet.setDstAddress(src_addr);
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reply_packet.setNextHeader(NH_ICMP);
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slip::send((void*)&reply_packet, 40 + len);
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}
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}
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return;
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}
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}
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