** Also affects: linux (Ubuntu Bionic)
Importance: Medium
Assignee: Joseph Salisbury (jsalisbury)
Status: In Progress
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https://bugs.launchpad.net/bugs/1743746
Title:
4.13: unable to increase MTU configuration for GRE devices
Status in linux package in Ubuntu:
In Progress
Status in linux source package in Artful:
In Progress
Status in linux source package in Bionic:
In Progress
Bug description:
[Impact]
GRE overlay networks can't carry traffic with MTU > 1500
[Test Case]
sudo add-apt-repository cloud-archive:pike
sudo apt update
sudo apt install openvswitch-switch
sudo ovs-vsctl add-br br-tun
sudo ovs-vsctl add-port br-tun gre0 -- set interface gre0 type=gre
options:remote_ip=10.100.1.1
gre_sys device will be configured with MTU 1472.
sudo ip link set gre_sys mtu 65000
will fail with EINVAL.
[Regression Potential]
[Bug Report]
Under Linux 4.13 its not possible to configure GRE tunnel devices with
a MTU larger than 1500; this impacts on Open vSwitch (which creates
tunnel devices for GRE overlay networking) and the ip tools.
The kernel will error with:
gre_sys: Invalid MTU 65000 requested, hw max 1500
The side effect of this is that if overlay networks are configured
with high MTUs, the gre devices fragment the packets and networking is
generally slow/broken.
This is resolved as part of the upcoming 4.15 kernel under:
https://github.com/torvalds/linux/commit/cfddd4c33c254954927942599d299b3865743146
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