Activity log for bug #1399064

Date Who What changed Old value New value Message
2014-12-04 04:16:50 Simon Déziel bug added bug
2014-12-04 04:30:14 Brad Figg linux (Ubuntu): status New Confirmed
2014-12-04 18:43:38 Joseph Salisbury linux (Ubuntu): importance Undecided Medium
2014-12-04 18:44:27 Joseph Salisbury tags amd64 apport-bug package-from-proposed trusty amd64 apport-bug kernel-da-key package-from-proposed trusty
2014-12-04 18:44:33 Joseph Salisbury linux (Ubuntu): status Confirmed Incomplete
2014-12-04 19:03:04 Simon Déziel tags amd64 apport-bug kernel-da-key package-from-proposed trusty amd64 apport-bug kernel-bug-exists-upstream kernel-da-key package-from-proposed trusty
2014-12-04 19:03:06 Simon Déziel description A linux bridge always adopts the smallest MTU of the enslaved devices. When no device are enslaved, it defaults to a MTU of 1500 and refuses to use a larger one. This is problematic when using bridges enslaving only virtual NICs (vnetX) like it's common with KVM guests. Steps to reproduce the problem 1) sudo ip link add br-test0 type bridge # create an empty bridge 2) sudo ip link add br-test0 mtu 9000 # attempt to set MTU > 1500 3) ip link show dev br-test0 # confirm MTU Here, 2) returns "RTNETLINK answers: Invalid argument". One (cumbersome) way around this is: 4) sudo modprobe dummy 5) sudo ip link set dummy0 mtu 9000 master br-test0 Then the bridge's MTU can be changed from anywhere to 9000. This bug is especially annoying for the virtualization case because the KVM's tap driver will by default adopt the bridge's MTU on startup making it impossible (without the workaround) to use a large MTU on the guest VMs. Additional information: $ lsb_release -rd Description: Ubuntu 14.04.1 LTS Release: 14.04 $ apt-cache policy linux-image-3.13.0-41-generic iproute2 linux-image-3.13.0-41-generic: Installed: 3.13.0-41.70 Candidate: 3.13.0-41.70 Version table: *** 3.13.0-41.70 0 500 http://archive.ubuntu.com/ubuntu/ trusty-proposed/main amd64 Packages 100 /var/lib/dpkg/status iproute2: Installed: 3.12.0-2 Candidate: 3.12.0-2 Version table: *** 3.12.0-2 0 500 http://archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages 100 /var/lib/dpkg/status ProblemType: Bug DistroRelease: Ubuntu 14.04 Package: linux-image-3.13.0-41-generic 3.13.0-41.70 ProcVersionSignature: Ubuntu 3.13.0-41.70-generic 3.13.11.11 Uname: Linux 3.13.0-41-generic x86_64 ApportVersion: 2.14.1-0ubuntu3.6 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: simon 4594 F.... pulseaudio CurrentDesktop: Unity CurrentDmesg: dmesg: klogctl failed: Operation not permitted Date: Wed Dec 3 23:02:25 2014 HibernationDevice: RESUME=UUID=8e7a3220-158f-413b-81b2-55b236bb1f3f InstallationDate: Installed on 2014-01-26 (311 days ago) InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140124) MachineType: LENOVO 2516CTO ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-41-generic root=/dev/mapper/crypt-root ro quiet splash cryptopts=target=crypt,source=/dev/sda1,lvm=crypt-root possible_cpus=4 nmi_watchdog=0 vt.handoff=7 RelatedPackageVersions: linux-restricted-modules-3.13.0-41-generic N/A linux-backports-modules-3.13.0-41-generic N/A linux-firmware 1.127.10 RfKill: 0: phy0: Wireless LAN Soft blocked: no Hard blocked: no SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 02/14/2013 dmi.bios.vendor: LENOVO dmi.bios.version: 6IET85WW (1.45 ) dmi.board.name: 2516CTO dmi.board.vendor: LENOVO dmi.board.version: Not Available dmi.chassis.asset.tag: No Asset Information dmi.chassis.type: 10 dmi.chassis.vendor: LENOVO dmi.chassis.version: Not Available dmi.modalias: dmi:bvnLENOVO:bvr6IET85WW(1.45):bd02/14/2013:svnLENOVO:pn2516CTO:pvrThinkPadT410:rvnLENOVO:rn2516CTO:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable: dmi.product.name: 2516CTO dmi.product.version: ThinkPad T410 dmi.sys.vendor: LENOVO A linux bridge always adopts the smallest MTU of the enslaved devices. When no device are enslaved, it defaults to a MTU of 1500 and refuses to use a larger one. This is problematic when using bridges enslaving only virtual NICs (vnetX) like it's common with KVM guests. Steps to reproduce the problem 1) sudo ip link add br-test0 type bridge # create an empty bridge 2) sudo ip link set br-test0 mtu 9000 # attempt to set MTU > 1500 3) ip link show dev br-test0 # confirm MTU Here, 2) returns "RTNETLINK answers: Invalid argument". One (cumbersome) way around this is: 4) sudo modprobe dummy 5) sudo ip link set dummy0 mtu 9000 master br-test0 Then the bridge's MTU can be changed from anywhere to 9000. This bug is especially annoying for the virtualization case because the KVM's tap driver will by default adopt the bridge's MTU on startup making it impossible (without the workaround) to use a large MTU on the guest VMs. Additional information: $ lsb_release -rd Description: Ubuntu 14.04.1 LTS Release: 14.04 $ apt-cache policy linux-image-3.13.0-41-generic iproute2 linux-image-3.13.0-41-generic:   Installed: 3.13.0-41.70   Candidate: 3.13.0-41.70   Version table:  *** 3.13.0-41.70 0         500 http://archive.ubuntu.com/ubuntu/ trusty-proposed/main amd64 Packages         100 /var/lib/dpkg/status iproute2:   Installed: 3.12.0-2   Candidate: 3.12.0-2   Version table:  *** 3.12.0-2 0         500 http://archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages         100 /var/lib/dpkg/status ProblemType: Bug DistroRelease: Ubuntu 14.04 Package: linux-image-3.13.0-41-generic 3.13.0-41.70 ProcVersionSignature: Ubuntu 3.13.0-41.70-generic 3.13.11.11 Uname: Linux 3.13.0-41-generic x86_64 ApportVersion: 2.14.1-0ubuntu3.6 Architecture: amd64 AudioDevicesInUse:  USER PID ACCESS COMMAND  /dev/snd/controlC0: simon 4594 F.... pulseaudio CurrentDesktop: Unity CurrentDmesg: dmesg: klogctl failed: Operation not permitted Date: Wed Dec 3 23:02:25 2014 HibernationDevice: RESUME=UUID=8e7a3220-158f-413b-81b2-55b236bb1f3f InstallationDate: Installed on 2014-01-26 (311 days ago) InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140124) MachineType: LENOVO 2516CTO ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-41-generic root=/dev/mapper/crypt-root ro quiet splash cryptopts=target=crypt,source=/dev/sda1,lvm=crypt-root possible_cpus=4 nmi_watchdog=0 vt.handoff=7 RelatedPackageVersions:  linux-restricted-modules-3.13.0-41-generic N/A  linux-backports-modules-3.13.0-41-generic N/A  linux-firmware 1.127.10 RfKill:  0: phy0: Wireless LAN   Soft blocked: no   Hard blocked: no SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 02/14/2013 dmi.bios.vendor: LENOVO dmi.bios.version: 6IET85WW (1.45 ) dmi.board.name: 2516CTO dmi.board.vendor: LENOVO dmi.board.version: Not Available dmi.chassis.asset.tag: No Asset Information dmi.chassis.type: 10 dmi.chassis.vendor: LENOVO dmi.chassis.version: Not Available dmi.modalias: dmi:bvnLENOVO:bvr6IET85WW(1.45):bd02/14/2013:svnLENOVO:pn2516CTO:pvrThinkPadT410:rvnLENOVO:rn2516CTO:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable: dmi.product.name: 2516CTO dmi.product.version: ThinkPad T410 dmi.sys.vendor: LENOVO
2014-12-04 19:03:20 Simon Déziel linux (Ubuntu): status Incomplete Confirmed
2014-12-04 19:33:09 Joseph Salisbury linux (Ubuntu): status Confirmed Triaged
2014-12-07 22:53:31 penalvch tags amd64 apport-bug kernel-bug-exists-upstream kernel-da-key package-from-proposed trusty amd64 apport-bug kernel-bug-exists-upstream kernel-da-key latest-bios-1.45 package-from-proposed trusty
2015-08-09 03:04:01 Nobuto Murata bug added subscriber Nobuto Murata
2015-10-10 13:12:33 Saverio bug added subscriber Saverio
2016-03-12 17:23:37 CvB bug added subscriber CvB
2016-05-03 14:15:05 Eberhard Pasch bug added subscriber Eberhard Pasch
2016-07-13 14:53:10 Alvaro Uria tags amd64 apport-bug kernel-bug-exists-upstream kernel-da-key latest-bios-1.45 package-from-proposed trusty amd64 apport-bug canonical-bootstack kernel-bug-exists-upstream kernel-da-key latest-bios-1.45 package-from-proposed trusty
2017-01-24 02:55:20 Ken Sharp tags amd64 apport-bug canonical-bootstack kernel-bug-exists-upstream kernel-da-key latest-bios-1.45 package-from-proposed trusty amd64 apport-bug canonical-bootstack kernel-bug-exists-upstream kernel-da-key latest-bios-1.45 package-from-proposed trusty xenial
2017-09-18 19:48:18 Gabriel Maduro bug added subscriber Gabriel Maduro
2019-02-16 19:59:08 Matt LaPlante bug added subscriber Matt LaPlante
2023-08-18 05:17:59 Trent Lloyd linux (Ubuntu): status Triaged Fix Released