Windows doesn't receive multicast IPv6 packets from all interfaces

Question

I am trying to receive IPv6 multicast packets (sent to the ff02::1 address) on Windows using this python 2.7 code-

import socket
import win_inet_pton
import          


        

Answer 1

Solved it :)

So apparently IPv6 doesn't listen to multicast from all interfaces. This syntax

mreq = group + struct.pack('@I', 0)

was wrong. According to this, mreq is composed of the group id and the interface id, where 0 is the default interface (in my case- WiFi). In order to listen to multicast from other interfaces, the network interface index should be specified.

The network interface index is the number thet appears after the % in the ipv6 address when running ipconfig, and can also be found running "route print" in cmd.

I used this code to find it on python:

import netifaces as ni
import _winreg as wr # use "winreg" in python3

def get_ethernet_ipv6_ifindex():
    x=ni.interfaces()
    con_names=get_connection_name_from_guid(x)
    ethernet_index= con_names.index('Ethernet')

    addresses= ni.ifaddresses(x[ethernet_index])
    brod_addr=addresses[socket.AF_INET6][-1]["broadcast"]

    return int(brod_addr[brod_addr.find("%")+1:])

"""
Taken from the very helpful https://stackoverflow.com/questions/29913516/how-to-get-meaningful-network-interface-names-instead-of-guids-with-netifaces-un
"""
def get_connection_name_from_guid(iface_guids):
    iface_names = ['(unknown)' for i in range(len(iface_guids))]
    reg = wr.ConnectRegistry(None, wr.HKEY_LOCAL_MACHINE)
    reg_key = wr.OpenKey(reg, r'SYSTEM\CurrentControlSet\Control\Network\{4d36e972-e325-11ce-bfc1-08002be10318}')
    for i in range(len(iface_guids)):
        try:
            reg_subkey = wr.OpenKey(reg_key, iface_guids[i] + r'\Connection')
            iface_names[i] = wr.QueryValueEx(reg_subkey, 'Name')[0]
        except WindowsError:
            pass
    return iface_names

And then-

mreq = group + struct.pack('@I', get_ethernet_ipv6_ifindex())