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#include <stdio.h>
#include <errno.h>
#include <strings.h>
#include <string.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <stdint.h>
#include <stdlib.h>
#include <poll.h>
#include <time.h>
#include <unistd.h>
#define SERVER_PORT 54321
#define TURN_LEN_S 5
#define TURN_LEN_MS (1000 * TURN_LEN_S)
#define TURN_LEN_US (1000000 * TURN_LEN_S)
#define NS_TO_MS(X) ((long)(X) / (long)1000000)
#define S_TO_MS(X) ((long)(X) * (long)1000)
struct router_addr {
struct in_addr addr;
uint16_t distance;
uint8_t netmask;
};
struct in_addr get_broadcast_address(struct router_addr ra) {
struct in_addr result = ra.addr;
/* bitshift by more than 31 is UB */
if (ra.netmask < 32) {
result.s_addr |= ~((1<<ra.netmask) - 1);
}
return result;
}
void pretty_print(struct router_addr ra) {
char ip_addr[20];
inet_ntop(AF_INET, &ra.addr, ip_addr, sizeof(ip_addr));
printf("%s/%d distance %d\n", ip_addr, ra.netmask, ra.distance);
}
/* converts string of IP with netmask in CIDR notation to router_addr */
struct router_addr stora(char *str) {
struct router_addr result;
char addr[20];
size_t ip_preffix = strcspn(str, "/");
strncpy(addr, str, strlen(str));
addr[ip_preffix] = 0;
inet_pton(AF_INET, addr, &(result.addr));
result.netmask = atoi(str + ip_preffix + 1);
return result;
}
int get_socket() {
int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd < 0) {
fprintf(stderr, "Socket error: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
return sockfd;
}
void bind_to_port(int sockfd, uint16_t port) {
struct sockaddr_in server_address;
bzero(&server_address, sizeof(server_address));
server_address.sin_family = AF_INET;
server_address.sin_port = htons(port);
server_address.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(sockfd, (struct sockaddr*)&server_address, sizeof(server_address)) < 0) {
fprintf(stderr, "Bind error: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
int broadcastPermission = 1;
setsockopt (sockfd, SOL_SOCKET, SO_BROADCAST, (void *)&broadcastPermission, sizeof(broadcastPermission));
}
uint16_t read_configuration(struct router_addr** networks) {
uint16_t n;
scanf("%hd", &n);
*networks = malloc(n * sizeof(struct router_addr));
for (int i = 0; i < n; i++) {
char addr[20];
char _dist[10];
uint16_t dist;
scanf(" %s %s %hd", addr, _dist, &dist);
(*networks)[i] = stora(addr);
(*networks)[i].distance = dist;
}
return n;
}
long get_time_interval(struct timespec start, struct timespec finish) {
return S_TO_MS(finish.tv_sec - start.tv_sec) + NS_TO_MS(finish.tv_nsec - start.tv_nsec);
}
int poll_modify_timeout(struct pollfd *fds, nfds_t nfd, int *timeout) {
if (*timeout < 0) {
fprintf(stderr, "poll_modify_timeout: timeout is negative.\n");
exit(EXIT_FAILURE);
}
struct timespec start;
clock_gettime(CLOCK_REALTIME, &start);
int result = poll(fds, nfd, *timeout);
if (result == -1) {
fprintf(stderr, "poll error: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
if (result == 0) {
*timeout = 0;
return 0;
}
struct timespec finish;
clock_gettime(CLOCK_REALTIME, &finish);
*timeout -= get_time_interval(start, finish);
printf("Timeout: %dms, time waiting: %ldms.\n", *timeout, get_time_interval(start, finish));
return result;
}
/* For debug purposes only */
void recv_and_print(int sockfd, int networks_number, struct router_addr *networks) {
struct sockaddr_in sender;
socklen_t sender_len = sizeof(sender);
uint8_t buffer[IP_MAXPACKET + 1];
ssize_t datagram_len = recvfrom(sockfd, buffer, IP_MAXPACKET, 0,
(struct sockaddr*)&sender, &sender_len);
if (datagram_len < 0) {
fprintf(stderr, "recvfrom error: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
for (int i = 0; i < networks_number; i++) {
if (networks[i].addr.s_addr == sender.sin_addr.s_addr) {
return;
}
}
char sender_ip_str[20];
inet_ntop(AF_INET, &(sender.sin_addr), sender_ip_str, sizeof(sender_ip_str));
printf("Received UDP packet from IP address: %s, port %d\n",
sender_ip_str, ntohs(sender.sin_port));
buffer[datagram_len] = 0;
printf("%ld-byte message: +%s+\n", datagram_len, buffer);
}
void listen_for_routers(int sockfd, int timeout, int networks_number, struct router_addr *netowrks) {
printf("Listening for %dms.\n", timeout);
struct pollfd fds;
fds.fd = sockfd;
fds.events = POLLIN;
fds.revents = 0;
while (poll_modify_timeout(&fds, 1, &timeout)) {
printf("Poll returned, remaining timeout: %dms.\n", timeout);
recv_and_print(sockfd, networks_number, netowrks);
}
printf("Finished listening\n");
}
int send_distance_vector(int sockfd, struct in_addr network) {
struct sockaddr_in network_address;
bzero (&network_address, sizeof(network_address));
network_address.sin_family = AF_INET;
network_address.sin_port = htons(SERVER_PORT);
network_address.sin_addr = network;
char* message = "Hello server! My name is S1\n";
ssize_t message_len = strlen(message);
int result;
char addr[20];
inet_ntop(AF_INET, &network, addr, sizeof(addr));
printf("Sending datagram to %s\n", addr);
if ((result = sendto(sockfd, message, message_len, 0, (struct sockaddr*) &network_address, sizeof(network_address))) != message_len) {
fprintf(stderr, "sendto error: %s\n", strerror(errno));
// return EXIT_FAILURE;
}
}
void propagate_distance_vector(int sockfd, int networks_number, struct router_addr *networks) {
printf("Propagating distance vector\n");
for (int i = 0; i < networks_number; i++) {
struct in_addr broadcast_address = get_broadcast_address(networks[i]);
send_distance_vector(sockfd, broadcast_address);
}
printf("Distance vector propagated.\n");
}
void router_loop(int sockfd, int networks_number, struct router_addr *networks) {
printf("Starting the router loop...\n");
for (;;) {
listen_for_routers(sockfd, TURN_LEN_MS, networks_number, networks);
propagate_distance_vector(sockfd, networks_number, networks);
}
}
int main() {
struct router_addr* networks;
int n = read_configuration(&networks);
for (int i = 0; i < n; i++) {
pretty_print(networks[i]);
}
int sockfd = get_socket();
bind_to_port(sockfd, SERVER_PORT);
router_loop(sockfd, n, networks);
close(sockfd);
free(networks);
}
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