** Tags added: kernel-bug-exists-upstream
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MTU probing does not work
Status in linux package in Ubuntu:
1) The release of Ubuntu you are using, via 'lsb_release -rd' or System ->
Ubuntu 16.04.1 LTS
2) The version of the package you are using, via 'apt-cache policy
pkgname' or by checking in Software Center
Kernel version 4.4.0-36
3) What you expected to happen
MTU probing should work automatically, there should be no network
connectivity problems due to too large MTU.
4) What happened instead
I'm having an Ubuntu 16.04 32bit installation running inside
Virtualbox, inside Ubuntu 16.04 64bit installation. Let's call the
virtualized server as A and the host server as B.
B is connected to Internet with static, public IP address. There are
no problems in its network connectivity i.e. it can be reached well
with any service from Internet.
A has been given a static, public IP address. Actually A is using B's
network card in connecting, but in my earlier virtual server
installations, this hasn't caused any problems. In earlier
installations (14.04 and before), there were no problems with network
Now, in the fresh 16.04.01 32bit installation on A (i.e. virtual
host), it seems that MTU is not probed properly. For example, if I'm
trying to have a SSH connection from some internet host into A, the
SSH connection freezes in "expecting SSH2_MSG_KEX_ECDH_REPLY" phase.
I tried manually setting net.ipv4.tcp_mtu_probing value to 1 and also
2, but it did not help. After I manually set the MTU value for lower
value, connectivity problems went away.
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-36-generic 4.4.0-36.55
ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16
Uname: Linux 4.4.0-36-generic i686
AlsaVersion: Advanced Linux Sound Architecture Driver Version
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/by-path',
'/dev/snd/pcmC0D1c', '/dev/snd/pcmC0D0c', '/dev/snd/pcmC0D0p',
'/dev/snd/controlC0', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Card0.Amixer.info: Error: [Errno 2] No such file or directory: 'amixer'
Card0.Amixer.values: Error: [Errno 2] No such file or directory: 'amixer'
Date: Tue Sep 13 10:02:55 2016
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
Bus 001 Device 002: ID 80ee:0021 VirtualBox USB Tablet
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
MachineType: innotek GmbH VirtualBox
ProcFB: 0 vboxdrmfb
root=UUID=952c3908-dbd9-48d0-899a-a3a14a678b7b ro splash quiet
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.vendor: innotek GmbH
dmi.board.vendor: Oracle Corporation
dmi.chassis.vendor: Oracle Corporation
dmi.sys.vendor: innotek GmbH
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