Bug 1409596 - Issue w/ Sendmail, NetworkManager and V6 DNS
Summary: Issue w/ Sendmail, NetworkManager and V6 DNS
Alias: None
Product: Fedora
Classification: Fedora
Component: sendmail
Version: 25
Hardware: x86_64
OS: Linux
Target Milestone: ---
Assignee: Jaroslav Škarvada
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2017-01-02 15:11 UTC by dan
Modified: 2017-12-12 10:18 UTC (History)
4 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Last Closed: 2017-12-12 10:18:13 UTC
Type: Bug

Attachments (Terms of Use)

Description dan 2017-01-02 15:11:57 UTC
Description of problem:

When sendmail first tries to start right after system boot it does not appear to make use of the IPv6 nameservers configured on my system.  Therefore any mail sent receives:

451 4.1.8 Domain of sender address dan@somehost.com does not resolve

A restart of sendmail cures the problem.

This occurs when resolv.conf contains only IPv6 nameservers.  If IPv4 nameservers are added prior to the v6 listings the problem does not occur.

I enabled the NetworkManager-wait-online.service but it did not help.

I then booted the host using only the v6 nameservers, had tcpdump running, and saw that on a connection to port 25, the recipient destination was not being queried on the v6 DNS listed in resolv.conf.  There was no DNS traffic.  I restarted sendmail and then the v6 queries worked properly.

The DNS servers, whether IPv4 or 6 are being provided by NetworkManager.

Comment 1 dan 2017-01-02 23:07:27 UTC
Confirmed that this is something between sendmail and NetworkManager.  Disabled NetworkManager.service and enabled the older network.service and the problem evaporates.

Comment 2 John Damm Sørensen 2017-03-20 10:35:17 UTC
I have a similar problem with only IPv4 name servers.

After a reboot mails are deferred:

From mailq: (host map: lookup (yahoo.com): deferred)

The log shows:
 --- 451 yahoo.com: Name server timeout
 --- 050 <XXXXXXXXXX@yahoo.com>... Transient parse error -- message queued for future delivery
 --- 451 yahoo.com: Name server timeout

I too tried the NetworkManager-wait-online.service and increased the time out to 300 seconds. But that didn't help either.

I also tried to increase the sendmail resolver retries:
O Timeout.resolver.retry.first=40000
Assuming that this would cause sendmail to keep retying for  5*40000 seconds.

I then disabled NetworkManager services and enabled the old network.service and now sendmail works without a restart after reboot.

So there is definitely a problem with the interaction between sendmail and NetworkManager. Only problem is what and how to debug it further.

Comment 3 John Damm Sørensen 2017-03-20 16:32:33 UTC
This problem is rather strange.

I thought that the most likely reason for this problem to appear would be that the file /var/run/NetworkManager/resolv.conf (pointed to by the symbolic link /etc/resolv.conf) is created after sendmail starts thus making the resolver fail. That would explain why increasing the resolver retries didn't help.

So I disabled network.service and enabled NetworkManager.service and rebooted.

Now sendmail works without a restart and examining the time stamps of /var/run/NetworkManager/resolv.conf and the start up time of sendmail shows that sendmail starts after the creation of /var/run/NetworkManager/resolv.conf.

Mar 20 17:09:47 www sm-msp-queue[2448]: starting daemon (8.15.2): queueing@01:00:00
Mar 20 17:09:49 www sendmail[2435]: NOQUEUE: stopping daemon, reason=signal
Mar 20 17:09:49 www sendmail[2532]: starting daemon (8.15.2): SMTP+queueing@01:00:00
Mar 20 17:09:49 www sendmail[2532]: STARTTLS: CRLFile missing
Mar 20 17:09:49 www sendmail[2532]: STARTTLS=server, Diffie-Hellman init, key=2048 bit (I)
Mar 20 17:09:49 www sendmail[2532]: STARTTLS=server, init=1
Mar 20 17:09:49 www sendmail[2532]: started as: /usr/sbin/sendmail -bd -q1h
Mar 20 17:09:49 www sm-msp-queue[2544]: starting daemon (8.15.2): queueing@01:00:00

# stat /var/run/NetworkManager/
   Fil: '/var/run/NetworkManager/'
  Stør: 60              Blokke: 0          IO-blokke: 4096   katalog
Enhed: 15t/21d  Inode: 24823       Lænker: 2
Adgang: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Adgang: 2017-03-20 17:09:39.355124166 +0100
Redig.: 2017-03-20 17:09:42.728226631 +0100
Ændret: 2017-03-20 17:09:42.728226631 +0100
Opret.: -

# stat /var/run/NetworkManager/resolv.conf
   Fil: '/var/run/NetworkManager/resolv.conf'
  Stør: 68              Blokke: 8          IO-blokke: 4096   almindelig fil
Enhed: 15t/21d  Inode: 30719       Lænker: 1
Adgang: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Adgang: 2017-03-20 17:13:55.974222842 +0100
Redig.: 2017-03-20 17:09:42.728226631 +0100
Ændret: 2017-03-20 17:09:42.728226631 +0100
Opret.: -

Comment 4 Fedora End Of Life 2017-11-16 19:22:20 UTC
This message is a reminder that Fedora 25 is nearing its end of life.
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Comment 5 Fedora End Of Life 2017-12-12 10:18:13 UTC
Fedora 25 changed to end-of-life (EOL) status on 2017-12-12. Fedora 25 is
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