Bug 988718

Created attachment 778706 [details]
libvirt debug log

Upstream patch proposed:
https://www.redhat.com/archives/libvir-list/2013-July/msg01711.html

Now fixed upstream:
commit 461fd86a661f32a9aa8044190b2a63b05290332f
Author:     Ján Tomko <jtomko>
AuthorDate: 2013-07-26 12:11:21 +0200
Commit:     Ján Tomko <jtomko>
CommitDate: 2013-07-26 12:53:45 +0200

    Don't check validity of missing attributes in DNS SRV XML
    
    This fixes a crash if one of them is missing.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=988718

git describe: v1.1.1-rc1-35-g461fd86


virsh net-update default delete dns-host "<host protocol='name'/>"
was also crashing if there were no dns host records in the network, fixed by:
commit c4e23388e6c7f769e45d1c162f880cd81e4d4d3b
Author:     Ján Tomko <jtomko>
AuthorDate: 2013-07-26 12:04:32 +0200
Commit:     Ján Tomko <jtomko>
CommitDate: 2013-07-26 12:50:34 +0200

    Set the number of elements 0 in virNetwork*Clear
    
    Decrementing it when it was already 0 causes an invalid free
    in virNetworkDefUpdateDNSHost if virNetworkDNSHostDefParseXML
    fails and virNetworkDNSHostDefClear gets called twice.
    
    virNetworkForwardDefClear left the number untouched even if it
    freed all the elements.

git describe: v1.1.1-rc1-34-gc4e2338

Verify this bug with libvirt-1.1.1-1.el7.x86_64.
Following the reproduce steps in comment0:
Create/Define,start a libvirt network
# virsh net-list
 Name                 State      Autostart     Persistent
----------------------------------------------------------
 default              active     yes           yes
 network              active     no            no

# virsh net-update network delete dns-srv "<srv service='name'/>"
Updated network network live state

# virsh net-dumpxml network
<network>
  <name>network</name>
  <uuid>2531df5b-adf0-471f-95f7-68d627053342</uuid>
  <bridge name='virbr2' stp='on' delay='0' />
  <mac address='52:54:00:90:a1:29'/>
  <domain name='example.com'/>
  <dns>
    <txt name='example' value='example value' />
    <host ip='192.168.10.2'>
      <hostname>myhost</hostname>
      <hostname>myhostalias</hostname>
    </host>
  </dns>
  <ip address='192.168.10.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.10.2' end='192.168.10.254' />
    </dhcp>
  </ip>
</network>
# virsh net-update network add dns-srv "<srv service='name' protocol='tcp'/>"
Updated network network live state

# virsh net-update network delete dns-txt "<txt name='example' value='example value'/>"
Updated network network live state

This request was resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you have further questions about the request.

Hi jtomko,

As comment 5 above, it indicates that the dns-srv, dns-txt, dns-host(I have tried) can be updated by the command net-update. But in fact, it can not take effect immediately. Perhaps it needs to re-run dnsmasq to pick up the changes just like update ip-dhcp-range. what do you think about it?

# virsh net-dumpxml network
<network>
  <name>network</name>
  <uuid>2531df5b-adf0-471f-95f7-68d627053342</uuid>
  <bridge name='virbr2' stp='on' delay='0'/>
  <mac address='52:54:00:90:a1:29'/>
  <domain name='example.com'/>
  <dns>
    <txt name='example' value='example value'/>
    <srv service='name' protocol='tcp' domain='test-domain-name' target='englab.nay.redhat.com' port='1024' priority='10' weight='10'/>
    <host ip='192.168.10.2'>
      <hostname>myhost</hostname>
      <hostname>myhostalias</hostname>
    </host>
  </dns>
  <ip address='192.168.10.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.10.2' end='192.168.10.254'/>
    </dhcp>
  </ip>
</network>
# virsh net-update network delete dns-srv "<srv service='name' protocol='tcp'/>"
Updated network network live state
# virsh net-update network delete dns-txt "<txt name='example'/>"
Updated network network live state
# virsh net-dumpxml network
<network>
  <name>network</name>
  <uuid>2531df5b-adf0-471f-95f7-68d627053342</uuid>
  <bridge name='virbr2' stp='on' delay='0'/>
  <mac address='52:54:00:90:a1:29'/>
  <domain name='example.com'/>
  <dns>
    <host ip='192.168.10.2'>
      <hostname>myhost</hostname>
      <hostname>myhostalias</hostname>
    </host>
  </dns>
  <ip address='192.168.10.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.10.2' end='192.168.10.254'/>
    </dhcp>
  </ip>
</network>
# cat /var/lib/libvirt/dnsmasq/network.conf
##WARNING:  THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
##OVERWRITTEN AND LOST.  Changes to this configuration should be made using:
##    virsh net-edit network
## or other application using the libvirt API.
##
## dnsmasq conf file created by libvirt
strict-order
domain=example.com
expand-hosts
pid-file=/var/run/libvirt/network/network.pid
except-interface=lo
bind-dynamic
interface=virbr2
dhcp-option=3
no-resolv
txt-record=example,example value
srv-host=_name._tcp.test-domain-name,englab.nay.redhat.com,1024,10,10
dhcp-range=192.168.10.2,192.168.10.254
dhcp-no-override
dhcp-lease-max=253
dhcp-hostsfile=/var/lib/libvirt/dnsmasq/network.hostsfile
addn-hosts=/var/lib/libvirt/dnsmasq/network.addnhosts

The txt and srv still exists in the network.conf file after delete. And still can parse correctly in the guest.

comment 8 test on libvirt-1.3.4-1.el7.x86_64

Yes, it is possible libvirtd forgot to write the config file. That is unrelated to this bug about libvirtd crashing, please file a separate one.

I haven't seen a separate bug filed yet, but I do see the source of the problem and have posted a patch upstream:

https://www.redhat.com/archives/libvir-list/2016-May/msg02122.html

If you do file a bug, please note this patch email and assign it to me.

file Bug 1341460 to track the issue in comment 8.