networkd doesn't set MTUBytes if interface is already up

Bug #1850704 reported by Dan Streetman on 2019-10-30
8
This bug affects 1 person
Affects Status Importance Assigned to Milestone
systemd
Fix Released
Unknown
systemd (Ubuntu)
Undecided
Unassigned
Bionic
Medium
Dan Streetman

Bug Description

[impact]

if a networkd .network file specifies a [Link] section with MTUBytes=XXX set, networkd will only apply that mtu if the interface is down when networkd starts; if the interface is already up, the mtu won't be applied.

[test case]

on a bionic system, create a .network file like:

[Match]
Name=ens8

[Link]
MTUBytes=6666

then, reboot. The interface should be set correctly with that mtu:

$ ip l show ens8
3: ens8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 6666 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:30:4c:1e brd ff:ff:ff:ff:ff:ff

now, manually change the interface back to 1500 mtu, and restart networkd, then recheck the mtu:

$ ip l show ens8
3: ens8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 6666 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:30:4c:1e brd ff:ff:ff:ff:ff:ff
$ sudo ip l set mtu 1500 dev ens8
$ ip l show ens8
3: ens8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:30:4c:1e brd ff:ff:ff:ff:ff:ff
$ sudo systemctl restart systemd-networkd
$ ip l show ens8
3: ens8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:30:4c:1e brd ff:ff:ff:ff:ff:ff

[regression potential]

low, but any regression would likely involve failure to correctly set the configured mtu.

this is needed only in bionic, it's fixed in disco and later already.

Dan Streetman (ddstreet) on 2019-10-30
Changed in systemd (Ubuntu):
status: New → Fix Released
Changed in systemd (Ubuntu Bionic):
assignee: nobody → Dan Streetman (ddstreet)
importance: Undecided → Medium
status: New → In Progress
Changed in systemd:
status: Unknown → Fix Released

Hello Dan, or anyone else affected,

Accepted systemd into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/systemd/237-3ubuntu10.32 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 on 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-bionic to verification-done-bionic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-bionic. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

Changed in systemd (Ubuntu Bionic):
status: In Progress → Fix Committed
tags: added: verification-needed verification-needed-bionic

All autopkgtests for the newly accepted systemd (237-3ubuntu10.32) for bionic have finished running.
The following regressions have been reported in tests triggered by the package:

gvfs/1.36.1-0ubuntu1.3.3 (ppc64el)
linux/unknown (ppc64el)

Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-migration/bionic/update_excuses.html#systemd

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

Dan Streetman (ddstreet) wrote :

the backport for this bug has caused regression-proposed bug 1852754

tags: added: verification-failed verification-failed-bionic
removed: verification-needed verification-needed-bionic

Hello Dan, or anyone else affected,

Accepted systemd into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/systemd/237-3ubuntu10.33 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 on 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-bionic to verification-done-bionic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-bionic. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

tags: added: verification-needed verification-needed-bionic
removed: verification-failed verification-failed-bionic

All autopkgtests for the newly accepted systemd (237-3ubuntu10.33) for bionic have finished running.
The following regressions have been reported in tests triggered by the package:

gvfs/1.36.1-0ubuntu1.3.3 (ppc64el, amd64)
dovecot/1:2.2.33.2-1ubuntu4.5 (armhf)
umockdev/0.11.1-1 (ppc64el)

Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-migration/bionic/update_excuses.html#systemd

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

Dan Streetman (ddstreet) wrote :

ubuntu@lp1850704-b:~$ cat /etc/systemd/network/10-ens3.network
[Match]
Name=ens3

[Network]
DHCP=ipv4
LinkLocalAddressing=ipv6

[Link]
MTUBytes=6666

ubuntu@lp1850704-b:~$ dpkg -l systemd|grep ii
ii systemd 237-3ubuntu10.33 amd64 system and service manager
ubuntu@lp1850704-b:~$ ip l show ens3
2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 6666 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:86:c7:44 brd ff:ff:ff:ff:ff:ff
ubuntu@lp1850704-b:~$ sudo ip l set mtu 1500 dev ens3
ubuntu@lp1850704-b:~$ ip l show ens3
2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:86:c7:44 brd ff:ff:ff:ff:ff:ff
ubuntu@lp1850704-b:~$ sudo systemctl restart systemd-networkd
ubuntu@lp1850704-b:~$ ip l show ens3
2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 6666 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:86:c7:44 brd ff:ff:ff:ff:ff:ff

tags: added: verification-done verification-done-bionic
removed: verification-needed verification-needed-bionic
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package systemd - 237-3ubuntu10.33

---------------
systemd (237-3ubuntu10.33) bionic; urgency=medium

  * d/p/lp1852754/0001-network-do-not-re-set-MTU-when-current-and-requested.patch,
    d/p/lp1852754/0002-network-call-link_acquire_conf-and-link_enter_join_n.patch,
    d/p/lp1852754/0003-network-prohibit-to-set-MTUBytes-and-UseMTU-simultan.patch:
    - Complete link setup after setting mtu (LP: #1852754)

systemd (237-3ubuntu10.32) bionic; urgency=medium

  [ Victor Tapia ]
  * d/p/resolved_disable-connection-downgrade-when-DNSSEC-yes.patch
    Fix regression introduced by
    resolved-Mitigate-DVE-2018-0001-by-retrying-NXDOMAIN-with.patch when
    DNSSEC=yes (LP: #1796501)

  [ Dan Streetman ]
  * d/p/fix-typo-lp1668771-resolved-switch-cache-option-to-a-tri-state-option-s.patch:
    - Fix typo in previous patch
  * d/p/lp1840640-shared-seccomp-add-sync_file_range2.patch:
    - allow sync_file_range2 in nspawn container
      (LP: #1840640)
  * d/p/lp1783994-dissect-Don-t-count-RPMB-and-boot-partitions-8609.patch:
    - avoid systemd-gpt-auto-generator failure if mmc dev present
      (LP: #1783994)
  * d/p/lp1832672-resolved-rework-parsing-of-etc-hosts.patch:
    - do not fail entire file on error when parsing /etc/hosts
    - parse # char anywhere in line as start of comment
      (LP: #1832672)
  * d/p/lp1843381-dell_passthrough_skip_rename_retry.patch,
    debian/extra/rules/73-usb-net-by-mac.rules:
    - fix rename delay for systems using "Dell MAC passthrough"
      (LP: #1843381)
  * d/p/lp1849733/0001-resolved-longlived-TCP-connections.patch,
    d/p/lp1849733/0002-resolved-line-split-dns_stream_new-function-signatur.patch,
    d/p/lp1849733/0003-resolved-add-some-assert-s.patch,
    d/p/lp1849733/0004-stream-track-type-of-DnsStream-object.patch,
    d/p/lp1849733/0005-llmnr-add-comment-why-we-install-no-complete-handler.patch,
    d/p/lp1849733/0006-resolved-restart-stream-timeout-whenever-we-managed-.patch,
    d/p/lp1849733/0007-resolved-only-call-complete-with-zero-argument-in-LL.patch,
    d/p/lp1849733/0008-resolved-add-comment-to-dns_stream_complete-about-it.patch,
    d/p/lp1849733/0009-resolved-keep-stub-stream-connections-up-for-as-long.patch,
    d/p/lp1849733/0010-resolved-if-we-can-t-append-EDNS-OPT-RR-then-indicat.patch,
    d/p/lp1849733/0011-resolved-don-t-let-EDNS0-OPT-dgram-size-affect-TCP.patch,
    d/p/lp1849733/0012-resolved-add-new-accessor-dns_stream_take_read_packe.patch,
    d/p/lp1849733/0013-resolve-do-not-complete-stream-transaction-when-it-i.patch:
    - add TCP pipelining to handle getaddrinfo() fallback to TCP
    - ignore EDNS0 payload limit when responding over TCP (LP: #1849733)
  * d/p/lp1849658-resolved-set-stream-type-during-DnsStream-creation.patch:
    - Fix bug in refcounting TCP stream types (LP: #1849658)
  * d/p/lp1850704/0001-networkd-Unify-set-MTU.patch,
    d/p/lp1850704/0002-network-drop-redundant-lines.patch:
    - Fix setting mtu if interface already up (LP: #1850704)
  * d/extra/dhclient-enter-resolved-hook:
    - only restart resolved if dhclient conf changed (LP: #1805183)

 -- Dan Streetman <email address hidden> Fri, 15 Nov 2019 10:01:16 -0500

Changed in systemd (Ubuntu Bionic):
status: Fix Committed → Fix Released

The verification of the Stable Release Update for systemd has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

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