title: Where multicast packets could be filtered?
body: <p>I installed openWRT distro on my router and enable support of avahi in it. My goal is to discover network services in my network. </p>
  
  <p>I plugged my PC to LAN port with announced services. On router I run tcpdump on bridge interface : <code>tcpdump -i br0 -vvn udp port 5353</code> </p>
  
  <p>During avahi browse execution i receive output:
  root@localhost:~# avahi-browse -art</p>
  
  <pre><code>21:55:22.995004 IP (tos 0x0, ttl 255, id 0, offset 0, flags [DF], proto UDP (17), length 74)
      192.168.1.1.5353 &gt; 224.0.0.251.5353: [udp sum ok] 0 PTR (QM)? _services._dns-sd._udp.local. (46)
  </code></pre>
  
  <p>But on my PC wireshark didn't show any multicast queries during that call, hence no services found. </p>
  
  <p>Does it mean that router filter multicast packets somehow? 
  Only way that i know is to filter in ebtables, which shows nothing about filtering of mDNS addresses:</p>
  
  <pre><code>root@localhost:~# ebtables -L
  Bridge table: filter
  
  Bridge chain: INPUT, entries: 1, policy: ACCEPT
  -j RO_INPUT
  
  Bridge chain: FORWARD, entries: 1, policy: ACCEPT
  -j RO
  
  Bridge chain: OUTPUT, entries: 1, policy: ACCEPT
  -j IGMPPROXY
  
  Bridge chain: RO, entries: 0, policy: RETURN
  
  Bridge chain: RO_INPUT, entries: 0, policy: RETURN
  
  Bridge chain: IGMPPROXY, entries: 4, policy: RETURN
  -p IPv4 -o wl0.1 --ip-dst 239.0.0.0/8 -j DROP 
  -p IPv4 -o wl0.2 --ip-dst 239.0.0.0/8 -j DROP 
  -p IPv4 -o wl0.3 --ip-dst 239.0.0.0/8 -j DROP 
  -p IPv4 -o br0 --ip-dst 239.0.0.0/8 -j DROP 
  </code></pre>
  
  <p>Where these multicast packets could be filtered/dropped?</p>