DragonFly bugs List (threaded) for 2011-04
Re: ssh + IPV6 + bridge => connection freezes
Forgot to mention - IPv6 connections to the vkernels attached to
the bridge work fine.
On Sun, 24 Apr 2011 11:04:30 -0700 (PDT)
Matthew Dillon <firstname.lastname@example.org> wrote:
> : Hi,
> : If IPV6 is enabled on a box and a bridge interface is enabled on
> :the same interface then any ssh connection to the box using the IPv6
> :address will freeze after a little activity (30 seconds of typing random
> :commands seems to be enough), bringing the bridge down with ifconfig will
> :restore activity to the ssh sessions (left alone they time out). I have
> seen :this with both 32 and 64 bit systems using up to date master code.
> : I'm also not sure that it's appropriate for a bridge interface to
> :have an IPv6 link local address - perhaps this is connected.
> :Steve O'Hara-Smith | Directable Mirror Arrays
> This is probably an issue with the MAC learning for the bridge.
> IPV6 works differently than IPV4, I think the MAC is built into
> the IPV6 address and there's no interface ARP (not sure though).
> We would need to explicitly support that in the bridge code.
> The reason it works for 30-seconds is probably due to the bridge's
> auto-learning. When the bridge doesn't know how to route a packet
> it basically just broadcasts it. It is probably learning the wrong
> thing, thinks it knows how to route the packet, but is not actually
> routing it to the right place. You can test this by issuing a bridge
> flush command with ifconfig (man bridge), then determine if bridging
> works again for a little bit. That isn't optimal since it's
> broadcasting in that state, so we will have to figure out the correct
> Another problem is the MAC munging the bridge does. When you connect
> an interface to a bridge *all* packets sent from that interface use
> the bridge's MAC address (otherwise there would be mass confusion).
> IPV6 is probably circumventing this by pulling the MAC out of the IPV6
> address (which is initially formed using the interface MAC) instead
> of using the interface MAC.
> Matthew Dillon
Steve O'Hara-Smith | Directable Mirror Arrays
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