Funny network packets with unknown hardware address - linux

Question

I have written a little program to investigate my home network, to see what packets are underway. I print the hardware address, and the number of packets.
Looks quite normal, i know all these addresses. But when i start Firefox, some new source addresses pop up. What are these? Normally i would say, there is a bug in my code, but they appear, when i start firefox, especially if i open a new tab?!
I have a Kubuntu 22.04 with Firefox 101.0.1
device: 00:00:40:11:4f:a5 --> 1 packets
device: 00:00:40:11:54:fa --> 1 packets
device: 00:00:40:11:66:c5 --> 1 packets
device: 00:00:40:11:69:30 --> 1 packets
device: 00:00:40:11:69:4e --> 1 packets
device: 00:00:40:11:6e:e1 --> 1 packets
device: 00:00:40:11:79:3a --> 1 packets
device: 00:00:40:11:7d:32 --> 1 packets
device: 00:00:40:11:83:05 --> 1 packets
device: 00:00:40:11:9a:ca --> 1 packets
device: 00:00:40:11:9c:2d --> 1 packets
device: 00:00:40:11:9c:30 --> 1 packets
My code is (g++ code.cpp -o code, run it with sudo):
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
#include <arpa/inet.h>
#include <errno.h>
#include <ctype.h>
#include <unistd.h>
#include <stdlib.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <netpacket/packet.h>
#include <linux/if_ether.h>
#include <linux/udp.h>
#include <netinet/if_ether.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <ctime>
#include <map>
#define BUFSIZE 2048*8
struct hwaddr{
uint8_t c[6];
bool operator<(const struct hwaddr &other) const{
for(int i = 0; i<6; i++){
if(c[i] != other.c[i]){
return c[i] < other.c[i];
}
}
return false;
}
};
void printeth(struct ether_header * e){
uint8_t * hwa;
hwa = e->ether_dhost;
printf("dest: %02x:%02x:%02x:%02x:%02x:%02x ", hwa[0], hwa[1], hwa[2], hwa[3], hwa[4], hwa[5]);
hwa = e->ether_shost;
printf("sour: %02x:%02x:%02x:%02x:%02x:%02x ", hwa[0], hwa[1], hwa[2], hwa[3], hwa[4], hwa[5]);
printf("type: %04x\n", (int)ntohs(e->ether_type));
}
void printcounter(std::map<struct hwaddr, uint64_t> const & counter){
static uint64_t last = std::time(0);
uint64_t const now = std::time(0);
if(now == last){
return;
}
last = now;
printf("\033[2J\033[1;1H");
printf("size: %d\n", (int)counter.size());
for(const auto & a : counter){
uint8_t * hwa = (uint8_t*)&a.first;
printf("device: %02x:%02x:%02x:%02x:%02x:%02x --> %8lu packets\n", hwa[0], hwa[1], hwa[2], hwa[3], hwa[4], hwa[5], a.second);
}
}
int main(int argc, char ** argv){
char buf[sizeof(struct ether_header)];
std::map<struct hwaddr,uint64_t> counter;
int const sockfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
if (sockfd < 0){
printf("ERROR opening socket: %s\n", strerror(errno));
return 0;
}
while (1) {
int const n = recv(sockfd, buf, sizeof(struct ether_header), 0);
if(n >= sizeof(struct ether_header)){
struct ether_header * e = (struct ether_header*)buf;
//printeth(e);
counter[*(struct hwaddr*)&e->ether_shost]++;
printcounter(counter);
}
}
return 0;
}