Bug 1332758

A workaround for this - just restart libvirtd. That will reset all the connection counts.

Test on below packages, net-update will bring broken settings as this connection issue.

libvirt-3.2.0-5.el7.x86_64
qemu-kvm-rhev-2.9.0-5.el7.x86_64

1. Start a macvtap network with passthrough mode. And 1 guest with 2 interface connected to the network.

# virsh net-dumpxml direct-macvtap
<network connections='1'>
  <name>direct-macvtap</name>
  <uuid>07d91730-8a76-432a-a7f2-bd3e0b650c98</uuid>
  <forward dev='p1p1_0' mode='passthrough'>
    <interface dev='p1p1_0' connections='1'/>
  </forward>
</network>

2. Use net-update to add 1 more interface dev to the network, the connections will gone, but the guest network works well.

# virsh net-update direct-macvtap add-last forward-interface "<interface dev='p1p1_2'/>"
Updated network direct-macvtap live state

# virsh net-dumpxml direct-macvtap                                                      
<network>
  <name>direct-macvtap</name>
  <uuid>07d91730-8a76-432a-a7f2-bd3e0b650c98</uuid>
  <forward dev='p1p1_0' mode='passthrough'>
    <interface dev='p1p1_0'/>
    <interface dev='p1p1_2'/>
  </forward>
</network>

#  ip a show | grep macvtap
61: macvtap0@p1p1_0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 500

3. Add 1 more interface to guest connecting to the network, there will be broken settings.

# virsh attach-interface rhel7.2 network direct-macvtap
Interface attached successfully

# virsh net-dumpxml direct-macvtap
<network connections='1'>
  <name>direct-macvtap</name>
  <uuid>07d91730-8a76-432a-a7f2-bd3e0b650c98</uuid>
  <forward dev='p1p1_0' mode='passthrough'>
    <interface dev='p1p1_0' connections='1'/>
    <interface dev='p1p1_2'/>
  </forward>
</network>

# ip a show | grep macvtap                             
63: macvtap1@p1p1_0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 500

expect there will be "macvtap1@p1p1_2" and "macvtap0@p1p1_0", but the original macvtap0 is gone.

Possible duplicates:

 - https://bugzilla.redhat.com/show_bug.cgi?id=1751580

 - https://bugzilla.redhat.com/show_bug.cgi?id=1745815

 - https://bugzilla.redhat.com/show_bug.cgi?id=1711180

Laine/Daniel, please have a look if it should be closed as duplicated or it is not relevant.  Thanks

(In reply to Martin Kletzander from comment #7)
> Possible duplicates:
> 
>  - https://bugzilla.redhat.com/show_bug.cgi?id=1751580
> 
>  - https://bugzilla.redhat.com/show_bug.cgi?id=1745815

These two bugs are fixing a problem only introduced in 5.3.0, so not the same as this bug.

> 
>  - https://bugzilla.redhat.com/show_bug.cgi?id=1711180

I don't think this is the same bug either.

> Laine/Daniel, please have a look if it should be closed as duplicated or it
> is not relevant.  Thanks

I think this is a bug we need to investigate for RHEL-7. Possibly its already fixed upstream, since libvirt-3.2.0-5.el7.x86_64 is quite old now.

Tested on below packages, for scenario in comment 0, it is the same. And the workaround that restart libvirtd did recover the connection counts as comment 3 suggested;

For scenario in comment 5, the behavior changes, and I think it is expected currently.
Check the details below:

# rpm -q libvirt qemu-kvm-rhev kernel
libvirt-4.5.0-35.el7.x86_64
qemu-kvm-rhev-2.12.0-47.el7.x86_64
kernel-3.10.0-1127.8.2.el7.x86_64

1. start a guest connecting the direct-passthrough network:
# virsh start rhel
Domain rhel started

# virsh net-dumpxml direct-passthrough
<network connections='1'>
  <name>direct-passthrough</name>
  <uuid>5a9ec3b8-428a-49f2-90c7-7c415a27848b</uuid>
  <forward dev='p4p2_0' mode='passthrough'>
    <interface dev='p4p2_0' connections='1'/>
  </forward>
</network>

2. Add one more forward interface:
# virsh net-update direct-passthrough add-last forward-interface "<interface dev='p4p2_1'/>"
Updated network direct-passthrough live state

# virsh net-dumpxml direct-passthrough
<network>
  <name>direct-passthrough</name>
  <uuid>5a9ec3b8-428a-49f2-90c7-7c415a27848b</uuid>
  <forward dev='p4p2_0' mode='passthrough'>
    <interface dev='p4p2_0'/>
    <interface dev='p4p2_1'/>
  </forward>
</network>

# ip a show | grep macvtap
23: macvtap0@p4p2_0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 500

# virsh attach-interface rhel network direct-passthrough
error: Failed to attach interface
error: error creating macvtap interface macvtap1@p4p2_0 (52:54:00:4e:86:9a): Invalid argument

After the net-update, the connections cleared as in comment 0. But the original macvtap device will not be override during next attach.

After evaluating this issue, there are no plans to address it further or fix it in an upcoming release.  Therefore, it is being closed.  If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.

After evaluating this issue, there are no plans to address it further or fix it in an upcoming release.  Therefore, it is being closed.  If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.