Red Hat Bugzilla – Bug 836475
bridging, transparent proxying and wifi yeild untrue destination unreachable
Last modified: 2013-07-31 22:11:31 EDT
Description of problem:
I have several virtual machines on a machine acting as a router. That router does TPROXY 4 with squid for filtering and virus scanning.
Some of the virtual machines act as Samba 4 servers.
The router has three real interfaces. An external ethernet that acts as the physical layer for pppoe. An internal ethernet and a wireless ethernet.
All have private ipv4 setups and private and public ipv6 setups.
With /proc/sys/net/ipv4/conf/wlan0/rp_filter set to 1, from time to time the wifi (wlan0) starts telling the virtual machine (virtio bridged ethernet for the vm) that the destination is unreachable for laptops (when the laptop is on the address and responding). I have NOT seen this for any wired ethernet device. Once it starts doing this, it seems to do it regularly until the device which it says is unreachable restarts its wifi (usually through reboot).
With rp_filter set to 0, this problem seems to go away.
I have seen a lot of strange behavior with virtio in bridged mode (virtual bridge not to any physical device). It seems that with rp_filter at 2, I might see this, but none of the kvm-qemu (AMD hardware viritualization) should trip up the wifi interface when set to 1 as they should NEVER appear to come from wlan0 or anything but virbr0 or virbr1 (yes, I have one for what will eventually be a DMZ and one for a common area for various networks).
I do not know if it is the transparent proxying stuff needed at this location or something else http://wiki.squid-cache.org/Features/Tproxy4#ebtables_on_a_Bridging_device
So, what is the bug: either rp_filter is broken, or something in virtual bridge/virtual machine is broken. I suppose both could be, but I doubt it. Logs, firewall configuration, whatever else are available, but I would prefer if the bug is either only available to developers, or that things are sent through email.
Version-Release number of selected component (if applicable):
I am not entirely positive, but this may have shown up about May 30th. Regardless, I have had no false "destination unreachable" on ipv6 on wlan0 in the described setup since I turned off rp_filter on wlan0.
To be perfectly honest, you are better off reporting this phenomenon directly to the upstream networking developers. They are going to be in a much better position to help you than we are. I'd recommend emailing your setup and issue to firstname.lastname@example.org and work directly with them.
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I believe I found the problem.
Wifi is a bit noisy. After a while Windows decides to reconnect to the Wifi Network. Windows, by default, uses IPv6 privacy extensions. In addition to whatever timed changes, any reconnection causes IPv6 address to change. So, you end up with hung connections on Linux Samba servers, which hangs Samba after so many until the connections timeout.
I do not believe this is a bug that can be fixed.
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