OpenWrt "Chaos Calmer" 15.05 released [LWN.net]

OpenWrt "Chaos Calmer" 15.05 released

Posted Sep 17, 2015 14:28 UTC (Thu) by smckay (guest, #103253)
In reply to: OpenWrt "Chaos Calmer" 15.05 released by raven667
Parent article: OpenWrt "Chaos Calmer" 15.05 released

I tried turning off avahi-daemon on the router--same behavior. Multicast packets crossing from one AP to the other have their source address changed to the router's. Some misconfiguration, maybe. It's not a huge deal, but this bridge is misbehaving and refusing to tell me whty--it's like learning vi all over again.

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OpenWrt "Chaos Calmer" 15.05 released

Posted Sep 17, 2015 16:12 UTC (Thu) by nybble41 (subscriber, #55106) [Link] (3 responses)

The source address & port changes you described sound more like NAT than bridging.

OpenWrt "Chaos Calmer" 15.05 released

Posted Sep 17, 2015 16:24 UTC (Thu) by smckay (guest, #103253) [Link] (2 responses)

Yeah, they do, which might make a little bit of sense if multicasts were also being sent out the WAN port, but they aren't.

OpenWrt "Chaos Calmer" 15.05 released

Posted Sep 17, 2015 17:54 UTC (Thu) by nybble41 (subscriber, #55106) [Link] (1 responses)

Perhaps the NAT rules for the WAN port are erroneously being applied to packets traversing the bridge? IIRC the decision of whether to mangle a packet for NAT is separate from the decision to route the packet out over any particular interface, and if you have multiple interfaces you need to include a condition (e.g. in my case it's "-A POSTROUTING -t nat -s $LOCAL_IP_RANGE -o $WAN_DEV -j MASQUERADE") to prevent NATing of internal packets. If the "-o $WAN_DEV" condition were omitted it could cause the symptoms you're seeing.

OpenWrt "Chaos Calmer" 15.05 released

Posted Sep 17, 2015 18:23 UTC (Thu) by marcH (subscriber, #57642) [Link]

The easiest to troubleshoot bridging is to temporarily iptables --flush and see whether the problem still happens or not.