cmol

cmol@qui-gon:~$ ruby src/multicast.rb
Using local interface wlp4s0 with address fe80::71c0:aa40:6d16:7c59%wlp4s0
========= Sending echo REQUEST from fe80::71c0:aa40:6d16:7c59%wlp4s0
[REQUEST] Hello from fe80::ade4:80af:c170:6340%enp0s31f6
========= Sending echo REPLY to fe80::ade4:80af:c170:6340%wlp4s0
[REQUEST] Hello from fe80::a00:27ff:fe07:dea6%enp0s3
========= Sending echo REPLY to fe80::a00:27ff:fe07:dea6%wlp4s0
[REPLY]   Hello from fe80::ade4:80af:c170:6340%enp0s31f6

cmol

def send_request(socket, linklocal_addr, multicast_addr, multicast_port,
                 flags)
  puts "========= Sending echo REQUEST from #{linklocal_addr}"
  socket.send("[REQUEST] Hello from #{linklocal_addr}",
              flags, multicast_addr, multicast_port)
end

cmol

def create_socket(multicast_addr, multicast_port, ifindex)
  # Create, bind, and return a UDP multicast socket
  UDPSocket.new(Socket::AF_INET6).tap do | s |
    ip = IPAddr.new(multicast_addr).hton + [ifindex].pack('I')
    s.setsockopt(Socket::IPPROTO_IPV6, Socket::IPV6_JOIN_GROUP, ip)
    s.setsockopt(Socket::IPPROTO_IPV6, Socket::IPV6_MULTICAST_HOPS, [1].pack('I'))
    s.setsockopt(Socket::IPPROTO_IPV6, Socket::IPV6_MULTICAST_IF, [ifindex].pack('I'))
    s.bind("::", multicast_port)
  end
end

cmol

cmol@second-host:~$ ruby src/multicast.rb
Using local interface enp0s31f6 with address fe80::ade4:80af:c170:6340%enp0s31f6
[REPLY]   Hello from fe80::71c0:aa40:6d16:7c59%wlp4s0

cmol

cmol@qui-gon:~$ ruby src/multicast.rb
Using local interface wlp4s0 with address fe80::71c0:aa40:6d16:7c59%wlp4s0
========= Sending echo REQUEST from fe80::71c0:aa40:6d16:7c59%wlp4s0

cmol

cmol@third-host:~$ ruby src/multicast.rb
Using local interface enp0s3 with address fe80::a00:27ff:fe07:dea6%enp0s3
========= Sending echo REQUEST from fe80::a00:27ff:fe07:dea6%enp0s3
[REPLY]   Hello from fe80::71c0:aa40:6d16:7c59%wlp4s0
[REPLY]   Hello from fe80::ade4:80af:c170:6340%enp0s31f6

cmol

require 'socket'
require 'ipaddr'

def get_interface_info(name)
  ifaddrs = Socket.getifaddrs.reject do |ifaddr|
    !ifaddr.addr&.ipv6_linklocal? || (ifaddr.flags & Socket::IFF_MULTICAST == 0)
  end
  ifaddrs.select! {|ifaddr| ifaddr.name == name } if name
  ifaddrs.map {|ifaddr| [ifaddr.name, ifaddr.ifindex, ifaddr.addr.ip_address] }
end

cmol

[["if_name", index, "ip_address"],[...]]

cmol

def echo_listener(socket, linklocal_addr, multicast_addr, multicast_port,
                  flags, msg_length)
  loop do
    # Listen for messages of up to specified length
    message, client = socket.recvfrom(msg_length)

    # Extract client information given as array and log connection
    addr_info = Addrinfo.new(client)

    # We are not interested in messages from our selves

cmol

def get_interface_info(name)
  ifaddrs = Socket.getifaddrs.reject do |ifaddr|
    !ifaddr.addr&.ipv6_linklocal? || (ifaddr.flags & Socket::IFF_MULTICAST == 0)
  end
  ifaddrs.select! {|ifaddr| ifaddr.name == name } if name
  ifaddrs.map {|ifaddr| [ifaddr.name, ifaddr.ifindex, ifaddr.addr.ip_address] }
end