From c5fcf7179a83ef65c86c6a4a390029149e518649 Mon Sep 17 00:00:00 2001 From: Franciszek Malinka Date: Tue, 5 Oct 2021 21:49:54 +0200 Subject: Duzy commit ze smieciami --- semestr-4/sieci/pracownia1/traceroute.c | 240 ++++++++++++++++++++++++++++++++ 1 file changed, 240 insertions(+) create mode 100644 semestr-4/sieci/pracownia1/traceroute.c (limited to 'semestr-4/sieci/pracownia1/traceroute.c') diff --git a/semestr-4/sieci/pracownia1/traceroute.c b/semestr-4/sieci/pracownia1/traceroute.c new file mode 100644 index 0000000..0e51c14 --- /dev/null +++ b/semestr-4/sieci/pracownia1/traceroute.c @@ -0,0 +1,240 @@ +/* Pracownia programistyczna nr 1 - traceroute + * Imię i nazwisko: Franciszek Malinka + * Nr indeksu: 316093 + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define MAX_TTL 30 +#define MESSAGES_PER_TTL 3 +#define NO_MESSAGES -1 +#define TOO_FEW_MESSAGES -2137 + +void print_as_bytes (unsigned char* buff, ssize_t length) +{ + for (ssize_t i = 0; i < length; i++, buff++) + printf ("%.2x ", *buff); +} + +void debug_received(uint8_t *buffer, struct sockaddr_in *sender, int packet_len) { + char ip_str[20]; + inet_ntop(AF_INET, &(sender->sin_addr), ip_str, sizeof(ip_str)); + + printf("IP packet with ICMP content from: %s\n", ip_str); + struct ip* ip_header = (struct ip*) buffer; + ssize_t ip_header_len = 4 * ip_header->ip_hl; + + printf ("IP header: "); + print_as_bytes (buffer, ip_header_len); + printf("\n"); + + printf ("IP data: "); + print_as_bytes (buffer + ip_header_len, packet_len - ip_header_len); + printf("\n\n"); +} + +struct sockaddr_in get_sockaddr_from_ip(char *ip) { + struct sockaddr_in sock; + bzero(&sock, sizeof(sock)); + sock.sin_family = AF_INET; + if (!inet_pton(AF_INET, ip, &sock.sin_addr)) { + fprintf(stderr, "Given ip is invalid: %s\n", ip); + exit(EXIT_FAILURE); + } + return sock; +} + +int create_raw_icmp_socket() { + int sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP); + if (sockfd < 0) { + fprintf(stderr, "socket error: %s\n", strerror(errno)); + exit(EXIT_FAILURE); + } + return sockfd; +} + +uint16_t compute_icmp_checksum(const void *buff, int length) +{ + uint32_t sum; + const uint16_t* ptr = buff; + assert (length % 2 == 0); + for (sum = 0; length > 0; length -= 2) + sum += *ptr++; + sum = (sum >> 16) + (sum & 0xffff); + return (uint16_t)(~(sum + (sum >> 16))); +} + +struct icmp create_icmp_header(uint16_t seq) { + struct icmp header; + header.icmp_type = ICMP_ECHO; + header.icmp_code = 0; + header.icmp_id = (uint16_t)getpid(); + header.icmp_seq = seq; + header.icmp_cksum = 0; + header.icmp_cksum = compute_icmp_checksum( + (uint16_t*)&header, sizeof(header)); + + return header; +} + +void send_icmp_packet(int sockfd, struct sockaddr_in *destination, int ttl) { + struct icmp header = create_icmp_header(ttl); + setsockopt(sockfd, IPPROTO_IP, IP_TTL, &ttl, sizeof(int)); + + ssize_t bytes_sent = sendto( + sockfd, + &header, + sizeof(header), + 0, + (struct sockaddr*)destination, + sizeof(*destination) + ); + if (bytes_sent == -1) { + fprintf(stderr, "Error while sending ICMP packet: %s\n", strerror(errno)); + exit(EXIT_FAILURE); + } +} + +/* Return ip address of the sender of recceived package */ +ssize_t recv_packet(int sockfd, struct sockaddr_in *sender, uint8_t *buffer) { + socklen_t sender_len = sizeof(*sender); + ssize_t packet_len = recvfrom(sockfd, buffer, IP_MAXPACKET, 0, + (struct sockaddr*)sender, &sender_len); + + if (packet_len == -1) { + fprintf(stderr, "Error while recieving a packet: %s\n", strerror(errno)); + exit(EXIT_FAILURE); + } + return packet_len; +} + +void send_icmp_requests(int sockfd, struct sockaddr_in *destination, int ttl, int tries) { + for (int i = 0; i < tries; i++) { + send_icmp_packet(sockfd, destination, ttl); + } +} + +int try_select(int sockfd, struct timeval *tv) { + fd_set descriptors; + FD_ZERO(&descriptors); + FD_SET(sockfd, &descriptors); + return select(sockfd+1, &descriptors, NULL, NULL, tv); +} + +void pretty_print_router(int ttl, struct in_addr *senders, float mean_wait_time, int messages_received) { + char ip_str[20]; + printf("%d.\t", ttl); + if (messages_received == 0) { + printf("*\n"); + } + else { + for (int i = 0; i < messages_received; i++) { + bool already_printed = false; + for (int j = 0; j < i; j++) { + if (senders[i].s_addr == senders[j].s_addr) { + already_printed = true; + break; + } + } + if (already_printed) continue; + inet_ntop(AF_INET, senders + i, ip_str, sizeof(ip_str)); + printf("%-15s ", ip_str); + } + if (messages_received < MESSAGES_PER_TTL) printf("\t???\n"); + else printf("\t%.2fms\n", mean_wait_time); + } +} + +// This function decapsulates important data from the IMCP replies +void get_important_data(uint8_t *buffer, uint8_t *code, uint16_t *id, uint16_t *seq) { + struct ip* ip_header = (struct ip*) buffer; + ssize_t offset = 4 * ip_header->ip_hl; + *code = ((struct icmp *)(buffer + offset))->icmp_type; + if (*code != ICMP_ECHOREPLY && *code != ICMP_TIMXCEED) { + return; + } else if (*code == ICMP_TIMXCEED) { + offset += ICMP_MINLEN; + offset += 4 * ((struct ip *)(buffer + offset))->ip_hl; + *seq = ((struct icmp *)(buffer + offset))->icmp_seq; + *id = ((struct icmp *)(buffer + offset))->icmp_id; + } else { + *seq = ((struct icmp *)(buffer + offset))->icmp_seq; + *id = ((struct icmp *)(buffer + offset))->icmp_id; + } +} + +// timeout in milliseconds +float get_replies(int sockfd, long timeout, int ttl, int *messages_received, struct in_addr *senders) { + struct sockaddr_in sender; + uint8_t buffer[IP_MAXPACKET]; + int ready; + long mean_wait_time = 0; + struct timeval tv; tv.tv_sec = timeout / 1000; tv.tv_usec = 0; + *messages_received = 0; + + while ((ready = try_select(sockfd, &tv))) { + if (ready < 0) { + fprintf(stderr, "Select error: %s\n", strerror(errno)); + exit(EXIT_FAILURE); + } + + recv_packet(sockfd, &sender, buffer); + uint8_t icmp_code = 0; + uint16_t seq = 0, id = 0; + + get_important_data(buffer, &icmp_code, &id, &seq); + if (seq == ttl) { + senders[(*messages_received)++] = sender.sin_addr; + mean_wait_time += timeout * 1000 - tv.tv_usec; + + if (*messages_received == MESSAGES_PER_TTL) break; + } + } + // changing from microseconds to miliseconds + return (float)mean_wait_time / 3.0 / 1000.0; +} + +// Core of the program. +void traceroute(struct sockaddr_in *destination) { + int sockfd = create_raw_icmp_socket(), messages_received = 0; + struct in_addr senders[MESSAGES_PER_TTL]; + + for (int ttl = 1; ttl <= MAX_TTL; ++ttl) { + send_icmp_requests(sockfd, destination, ttl, MESSAGES_PER_TTL); + float mean_wait_time = get_replies(sockfd, 1000, ttl, &messages_received, senders); + pretty_print_router(ttl, senders, mean_wait_time, messages_received); + + // what if our packet branched and we got to the destination faster by some path? + // we gotta make a loop, not an if + for (int i = 0; i < messages_received; i++) { + if (senders[i].s_addr == destination->sin_addr.s_addr) { + return; + } + } + } +} + +int main(int argc, char * argv[]) { + if (argc < 2) { + fprintf(stderr, "Usage:\n\t%s [host ip]\n", argv[0]); + return 1; + } + + struct sockaddr_in destination = get_sockaddr_from_ip(argv[1]); + fprintf(stdout, "traceroute to %s, %d hops max\n", argv[1], MAX_TTL); + traceroute(&destination); + + return 0; +} \ No newline at end of file -- cgit v1.2.3