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Message #151583
[Bug 1499827] Re: [ipv6] Network manager incorrectly lowers MTU when IPv6 is enabled
Hello Bryan, or anyone else affected,
Accepted network-manager into wily-proposed. The package will build now
and be available at https://launchpad.net/ubuntu/+source/network-
manager/1.0.4-0ubuntu5.2 in a few hours, and then in the -proposed
repository.
Please help us by testing this new package. See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to
enable and use -proposed. Your feedback will aid us getting this update
out to other Ubuntu users.
If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, and change the tag
from verification-needed to verification-done. If it does not fix the
bug for you, please add a comment stating that, and change the tag to
verification-failed. In either case, details of your testing will help
us make a better decision.
Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in
advance!
** Changed in: network-manager (Ubuntu Wily)
Status: Triaged => Fix Committed
** Tags added: verification-needed
--
You received this bug notification because you are a member of Desktop
Packages, which is subscribed to network-manager in Ubuntu.
https://bugs.launchpad.net/bugs/1499827
Title:
[ipv6] Network manager incorrectly lowers MTU when IPv6 is enabled
Status in NetworkManager:
Fix Released
Status in network-manager package in Ubuntu:
Fix Released
Status in network-manager source package in Wily:
Fix Committed
Bug description:
[Impact]
Users with IPv6-supporting networks will see the messages below in the bug description appear repeatedly as NM mistakes a 0 value for MTU in internal NM code with 0-size packets instead of meaning "use default MTU".
[Test case]
- Run network-manager on a network supporting IPv6.
- Check /var/log/syslog for <warn> messages from NetworkManager.
[Regression Potential]
This changes behavior for handling the MTU value for IPv6, which should be no higher than the device MTU. Since 0 is an invalid value for MTU anyway, this should not otherwise affect MTU handling for devices.
Possible regressions from the change might include invalid (too high) set MTU for a device due to the failure to recognize cases where the MTU needs to be adjusted, leading to packet loss on IPv6.
--
Network manager is sending out a lot of warnings about changing the MTU:
Sep 25 14:13:03 desktop NetworkManager[703]: <warn> (wlan0): Lowering IPv6 MTU (1480) to match device MTU (1280)
Sep 25 14:13:21 desktop NetworkManager[703]: <warn> (wlan0): Lowering IPv6 MTU (1480) to match device MTU (0)
Sep 25 14:13:21 desktop NetworkManager[703]: <warn> (wlan0): IPv6 MTU (0) smaller than 1280, adjusting
Sep 25 14:13:21 desktop NetworkManager[703]: <warn> (wlan0): Raising device MTU (0) to match IPv6 MTU (1280)
Sep 25 14:13:29 desktop NetworkManager[703]: <warn> (wlan0): Lowering IPv6 MTU (1480) to match device MTU (1280)
Lowering IPv6 MTU (1480) to match device MTU (1280) repeats about 16
times between the other messages (about 2 mins round).
This doesn't appear to be Ubuntu specific -
https://bbs.archlinux.org/viewtopic.php?pid=1552751
ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: network-manager 1.0.4-0ubuntu3
ProcVersionSignature: Ubuntu 4.2.0-11.13-generic 4.2.1
Uname: Linux 4.2.0-11-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.19-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Fri Sep 25 14:09:20 2015
IfupdownConfig:
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
InstallationDate: Installed on 2015-01-08 (259 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Alpha amd64 (20150108)
NetworkManager.state:
[main]
NetworkingEnabled=true
WirelessEnabled=true
WWANEnabled=true
WimaxEnabled=true
RfKill:
0: phy0: Wireless LAN
Soft blocked: no
Hard blocked: no
SourcePackage: network-manager
UpgradeStatus: Upgraded to wily on 2015-08-12 (43 days ago)
nmcli-nm: Error: command ['nmcli', '-f', 'all', 'nm'] failed with exit code 2: Error: Object 'nm' is unknown, try 'nmcli help'.
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References