beacon.c

/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause) */

#include "config.h"
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <pthread.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <syslog.h>

#include "socketcand.h"
#include "beacon.h"

void *beacon_loop(void *ptr) {
	int i, n, chars_left, ret;
	int udp_socket;
	int optval;
	char buffer[BEACON_LENGTH];
	char hostname[32];

	if ((udp_socket = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
		PRINT_ERROR("Failed to create broadcast socket");
		return NULL;
	}

	/* Activate broadcast option */
	optval = 1;
	ret = setsockopt(udp_socket, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(int));
	if(ret) {
		PRINT_ERROR("Could not activate SO_BROADCAST\n");
	}

	/* Connect the socket */
	if(connect(udp_socket, (struct sockaddr *) &broadcast_addr, sizeof(broadcast_addr)) < 0) {
		PRINT_ERROR("Failed to connect broadcast socket");
		return NULL;
	}

	while(1) {
		/* Build the beacon */
		gethostname((char *) &hostname, (size_t)  32);
		snprintf(buffer, BEACON_LENGTH, "<CANBeacon name=\"%s\" type=\"%s\" description=\"%s\">\n<URL>can://%s:%d</URL>",
			 hostname, BEACON_TYPE, description, inet_ntoa( saddr.sin_addr ), port);

		for(i=0;i<interface_count;i++) {
			/* Find \0 in beacon buffer */
			for(n=0;;n++) {
				if(buffer[n] == '\0')
					break;
			}
			chars_left = BEACON_LENGTH - n;

			snprintf(buffer+(n*sizeof(char)), chars_left, "<Bus name=\"%s\"/>", interface_names[i]);
		}
        
		/* Find \0 in beacon buffer */
		for(n=0;;n++) {
			if(buffer[n] == '\0')
				break;
		}
		chars_left = BEACON_LENGTH - n;

		snprintf(buffer+(n*sizeof(char)), chars_left, "</CANBeacon>");

		ret = send(udp_socket, buffer, strlen(buffer), 0);
		if(ret == -1) {
			PRINT_ERROR("Error in beacon send()\n");
		}
		sleep(3);
	}

	return NULL;
}