Linux Ethernet Bridging - Feb 2016 - [Bridge] Help with Ubuntu + bridge + tap + qemu + Windows

Hi guys

I have been researching this problem for weeks, and I have tried everything
every web page has even remotely suggested, and nothing works. I am at my wits
end, and I simply *must* get my issue resolved.

Basically, when I bring up one or more VMs using tap# on a br# on an eth#, the
network interface will work for a random amount of time, but inevitably
something will die, and the ?TX packets? stops incrementing, and the ?TX packets
dropped? takes over. At that point, I can shut down and start up my VM, and go
through the cycle again with a different random time and packets transmitted.

tap2      Link encap:Ethernet  HWaddr 8a:21:a8:cb:f5:98  
          inet6 addr: fe80::8821:a8ff:fecb:f598/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:51870 errors:0 dropped:0 overruns:0 frame:0
          TX packets:741595 errors:0 dropped:5702 overruns:0 carrier:0
          collisions:0 txqueuelen:500 
          RX bytes:3220139 (3.2 MB)  TX bytes:1113177111 (1.1 GB)

I could obviously post every shred of information I have, ethtool, iptables,
netstat, brctl, etc. but I hate to create a 10K email with mostly unnecessary
outputs. If anyone has a specific set of questions they need answered, I am more
than happy to provide. I?m running the latest Ubuntu and get updates daily. The
uname -a as of this morning is:

Darwin Carolyns-MacBook-Air.local 15.3.0 Darwin Kernel Version 15.3.0: Thu Dec
10 18:40:58 PST 2015; root:xnu-3248.30.4~1/RELEASE_X86_64 x86_64

What in the world am I doing wrong, or where is this failing, how do I find it,
and most importantly, how do I fix it? :)

Thank you,
David Logan

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oops. Wrong machine. The uname -a really is

Linux server2 3.16.0-59-generic #79~14.04.1-Ubuntu SMP Mon Jan 18 15:41:27 UTC
2016 x86_64 x86_64 x86_64 GNU/Linux

David Logan


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On Tue, Feb 2, 2016 at 1:21 AM, David Logan <djlogan2.dl at gmail.com>
wrote:
>
> tap2      Link encap:Ethernet  HWaddr 8a:21:a8:cb:f5:98
>           inet6 addr: fe80::8821:a8ff:fecb:f598/64 Scope:Link
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:51870 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:741595 errors:0 dropped:5702 overruns:0 carrier:0
>           collisions:0 txqueuelen:500
>           RX bytes:3220139 (3.2 MB)  TX bytes:1113177111 (1.1 GB)
You are seeing TX packets dropped at the tap interface. So these are
packets that are being sent from the bridge to the VM on the tap
device, but getting dropped, probably because the tap device's queue
is full. This would mean that the packets are not getting read by the
VM fast enough, or may be not read at all after some point, since you
see only the dropped increase after a while. So the issue is likely to
be related to the virtualization software, rather than the bridge.
Have you tried asking about this on forums related to the
virtualization system you are using?