networkd doesn't set MTUBytes if interface is already up

[Dan Streetman]

[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.

[Łukasz Zemczak (sil2100)]

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.

[Ubuntu SRU Bot (ubuntu-sru-bot)]

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)]

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

[Steve Langasek (vorlon)]

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.

[Ubuntu SRU Bot (ubuntu-sru-bot)]

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)]

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

[Launchpad Janitor (janitor)]

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

[Steve Langasek (vorlon)]

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.