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Description of problem:
The network target is reached before IPv6 adresses are assigned:
May 5 22:32:09 localhost network: Bringing up loopback interface: [ OK ]
May 5 22:32:09 localhost network: Bringing up interface eth0: [ OK ]
May 5 22:32:09 localhost network: Bringing up interface eth1: [ OK ]
May 5 22:32:09 localhost network: Bringing up interface eth2: [ OK ]
May 5 22:32:09 localhost systemd: Started LSB: Bring up/down networking.
May 5 22:32:09 localhost systemd: Reached target Network.
Which in turn causes dovecot to fail to start up one second later:
May 5 22:32:10 localhost dovecot: Error: bind(x:x:x:x:x:x:x:x, 995) failed: Cannot assign requested address
May 5 22:32:10 localhost dovecot: Error: service(pop3-login): listen(pop3s.dovecot, 995) failed: Cannot assign requested address
May 5 22:32:10 localhost dovecot: Error: bind(x:x:x:x:x:x:x:x, 993) failed: Cannot assign requested address
May 5 22:32:10 localhost dovecot: Error: service(imap-login): listen(imaps.dovecot, 993) failed: Cannot assign requested address
May 5 22:32:10 localhost dovecot: Fatal: Failed to start listeners
Adding the following acts as a workaround:
[root@localhost ~]# cat /etc/sysctl.d/90-dovecot-workaround.conf
net.ipv6.conf.eth0.accept_dad = 0
Full explanation of the bug is here: https://serverfault.com/questions/766253/ensure-systemd-wait-for-ipv6-before-start-service-unit
Version-Release number of selected component (if applicable):
systemd-219-62.el7_6.6.x86_64
How reproducible:
Always
Steps to Reproduce:
- Ask dovecot to bind to a specific static IPv6 address.
- Boot machine
Actual results:
- Dovecot fails to start
Expected results:
- Dovecot starts normally
Additional info:
Hi Graham,
It looks that the issue is triggered by IPV6_FAILURE_FATAL=no in corresponding /etc/sysconfig/network-scripts/ifcfg-XXX or ipv6.may-fail=yes by nmcli command.
It means that NetworkManager-wait-online service doesn't wait for IPV6 connectivity.
So, ipv.may-fail=no by nmcli command or IPV6_FAILURE_FATAL=yes may resolve your issue.
Thanks,
Keigo
Hi Thomas,
I suggest improving the systemd manpage as well, see 1825666#c6:
"
Below is where the issue is:
systemd.special(7) states:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
network-online.target
[...]
What precisely this requires is left to the implementation
of the network managing service.
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
This is already obscure, the admin must understand that on RHEL8, it's NetworkManager and achieved through exectuing NetworkManager-wait-online.service.
First I think that a patch should be made in systemd manpage to clear state NetworkManager is the network managing service.
"
Beniamino did some work on RHEL8's BZ 1825666
> I suggest improving the systemd manpage as well, see 1825666#c6:
OK. Makes sense...
I think this bug is a duplicate to bug 1825666, with the difference that this bug is for NetworkManager@rhel-7 and the other is for NetworkManager@rhel-8. As far as NetworkManager package is concerned (and the man page that it provides), I think this will be soon fixed.
Please clone this or the other bug to systemd (depending on whether you want it for rhel-7 or rhel-8), which provides systemd.special man page. Usually, I would clone the bug myself, but I don't overly agree that this change to the manual page should be done, so I have no good arguments of my own to argue in favour of the change. Renaud, if you feel systemd should adjust their manual page, please clone the bug (or the other one, for rhel-8).
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory (Moderate: NetworkManager security and bug fix update), and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2020:4003