(re)starting networkd removes still-valid RFC 4941 ipv6 addrs

[Shivaram Lingamneni]

I updated my Ubuntu 18.04.2 server from systemd 237-3ubuntu10.24 to 237-3ubuntu10.25. This caused a restart of systemd-networkd, breaking all TCP-over-IPv6 connections.

apt history entry:

Start-Date: 2019-08-06 19:46:21
Commandline: apt-get dist-upgrade -y
Requested-By: shivaram (1000)
Upgrade: libsystemd0:amd64 (237-3ubuntu10.24, 237-3ubuntu10.25), udev:amd64 (237-3ubuntu10.24, 237-3ubuntu10.25), libudev1:amd64 (237-3ubuntu10.24, 237-3ubuntu10.25), systemd-sysv:amd64 (237-3ubuntu10.24, 237-3ubuntu10.25), libpam-systemd:amd64 (237-3ubuntu10.24, 237-3ubuntu10.25), systemd:amd64 (237-3ubuntu10.24, 237-3ubuntu10.25), libnss-systemd:amd64 (237-3ubuntu10.24, 237-3ubuntu10.25), base-files:amd64 (10.1ubuntu2.5, 10.1ubuntu2.6)
End-Date: 2019-08-06 19:54:17

systemd journal output:

Aug 06 19:47:40 pentos systemd[1]: Reloading.
Aug 06 19:47:57 pentos systemd[1]: Reexecuting.
Aug 06 19:47:58 pentos systemd[1]: systemd 237 running in system mode. (+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD -IDN2 +IDN -PCRE2 default-hie
Aug 06 19:47:58 pentos systemd[1]: Detected architecture x86-64.
Aug 06 19:47:58 pentos systemd[1]: Stopping Network Service...
Aug 06 19:47:58 pentos systemd[1]: Stopped Network Service.
Aug 06 19:47:58 pentos systemd[1]: Starting Network Service...
Aug 06 19:47:59 pentos systemd-networkd[11513]: ens5: Gained IPv6LL
Aug 06 19:47:59 pentos systemd-networkd[11513]: Enumeration completed
Aug 06 19:47:59 pentos systemd[1]: Started Network Service.
Aug 06 19:47:59 pentos systemd-networkd[11513]: lo: Link is not managed by us
Aug 06 19:47:59 pentos systemd-networkd[11513]: ens5: DHCPv4 address 192.168.1.103/24 via 192.168.1.1
Aug 06 19:47:59 pentos dbus-daemon[947]: [system] Activating via systemd: service name='org.freedesktop.hostname1' unit='dbus-org.freedesktop.hostname1.service' requested by ':1.2341' (uid=100 pid=11513 comm="/lib/systemd/systemd-network
Aug 06 19:47:59 pentos systemd-networkd[11513]: ens5: Configured

[Dan Streetman (ddstreet)]

upgrading systemd does restart networkd, but it should not remove any existing managed configuration while restarting (or stopping). For example:

ubuntu@lp1839231:~$ sudo systemctl start systemd-networkd
ubuntu@lp1839231:~$ ip a show ens3
2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:54:00:e8:e2:3f brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.25/24 brd 192.168.122.255 scope global dynamic ens3
       valid_lft 3537sec preferred_lft 3537sec
    inet6 fe80::5054:ff:fee8:e23f/64 scope link
       valid_lft forever preferred_lft forever
ubuntu@lp1839231:~$ sudo systemctl stop systemd-networkd
Warning: Stopping systemd-networkd.service, but it can still be activated by:
  systemd-networkd.socket
ubuntu@lp1839231:~$ ip a show ens3
2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:54:00:e8:e2:3f brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.25/24 brd 192.168.122.255 scope global dynamic ens3
       valid_lft 3529sec preferred_lft 3529sec
    inet6 fe80::5054:ff:fee8:e23f/64 scope link
       valid_lft forever preferred_lft forever
ubuntu@lp1839231:~$ sudo systemctl start systemd-networkd
ubuntu@lp1839231:~$ ip a show ens3
2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 52:54:00:e8:e2:3f brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.25/24 brd 192.168.122.255 scope global dynamic ens3
       valid_lft 3599sec preferred_lft 3599sec
    inet6 fe80::5054:ff:fee8:e23f/64 scope link
       valid_lft forever preferred_lft forever

What specific config is in your networkd config files? What specific interface(s) or address(es) are you having trouble with?

[Shivaram Lingamneni (slingamn)]

Thanks! This system is using netplan, with ipv6-privacy enabled in netplan (subsequent to the fix in bug #1750392):

root@pentos:~# cat /etc/netplan/01-netcfg.yaml
# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network:
  version: 2
  renderer: networkd
  ethernets:
    ens5:
      dhcp4: true
      ipv6-privacy: true

The issue reproduces with the ens5 interface. Stopping systemd-networkd does not change any addresses, but starting it again removes all the "deprecated" addresses, even if they are in use by TCP connections:

root@pentos:~# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: ens5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether [mac-redacted] brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.103/24 brd 192.168.1.255 scope global dynamic ens5
       valid_lft 52839sec preferred_lft 52839sec
    inet6 [redacted-ipv6-/64]:8d03:bfce:131d:190/64 scope global temporary dynamic
       valid_lft 596sec preferred_lft 596sec
    inet6 [redacted-ipv6-/64]:306e:2bf2:9d28:ef32/64 scope global temporary deprecated dynamic
       valid_lft 596sec preferred_lft 0sec
    inet6 [redacted-ipv6-/64]:c060:f52:5638:10e9/64 scope global temporary deprecated dynamic
       valid_lft 596sec preferred_lft 0sec
    inet6 [redacted-ipv6-/64]:d941:e7ff:cc75:9968/64 scope global temporary deprecated dynamic
       valid_lft 596sec preferred_lft 0sec
    inet6 [redacted-ipv6-/64]:2dae:1ae3:c572:ed57/64 scope global temporary deprecated dynamic
       valid_lft 596sec preferred_lft 0sec
    inet6 [redacted-ipv6-/64]:90ec:5051:54de:f345/64 scope global temporary deprecated dynamic
       valid_lft 596sec preferred_lft 0sec
    inet6 [redacted-ipv6-/64]:5497:3bdc:6452:c67f/64 scope global temporary deprecated dynamic
       valid_lft 596sec preferred_lft 0sec
    inet6 [redacted-ipv6-/64]:[slaac-redacted]/64 scope global dynamic mngtmpaddr noprefixroute
       valid_lft 596sec preferred_lft 596sec
    inet6 fe80::[ll-redacted]/64 scope link
       valid_lft forever preferred_lft forever
root@pentos:~# systemctl stop systemd-networkd
root@pentos:~# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: ens5: <BROA...

[Dan Streetman (ddstreet)]

This appears to need patching upstream; have you opened a bug there yet?

[Nick Rosbrook (enr0n)]

Please re-open if this is still an issue on newer releases.