Bug 1189007

Easy to reproduce it
# rpm -q libvirt 
libvirt-1.2.8-15.el7.x86_64

1. 
# qemu-img create /var/lib/libvirt/images/backing -f qcow2 10M 
Formatting '/var/lib/libvirt/images/backing', fmt=qcow2 size=10485760 encryption=off cluster_size=65536 lazy_refcounts=off

2.
# qemu-nbd -f qcow2  /var/lib/libvirt/images/backing 

3. 
# qemu-img create -f qcow2 /var/lib/libvirt/images/nbd -o backing_file=nbd://localhost 
Formatting '/var/lib/libvirt/images/nbd', fmt=qcow2 size=10485760 backing_file='nbd://localhost' encryption=off cluster_size=65536 lazy_refcounts=off 

4. 
# virsh pool-refresh default
error: failed to connect to the hypervisor
error: no valid connection
error: Cannot recv data: Connection reset by peer

Verified on libvirt-1.2.15-2.el7.x86_64

Steps
1. storage file backed by gluster://$IP
# qemu-img create -f qcow2 /var/lib/libvirt/images/gluster.img 100M
Formatting '/var/lib/libvirt/images/gluster.img', fmt=qcow2 size=104857600 encryption=off cluster_size=65536 lazy_refcounts=off 
[root@rhel7_test ~]# qemu-img rebase -u -f qcow2 -F raw -b gluster://10.66.4.164 /var/lib/libvirt/images/gluster.img
[root@rhel7_test ~]# qemu-img info /var/lib/libvirt/images/gluster.img
image: /var/lib/libvirt/images/gluster.img
file format: qcow2
virtual size: 100M (104857600 bytes)
disk size: 196K
cluster_size: 65536
backing file: gluster://10.66.4.164
backing file format: raw
Format specific information:
    compat: 1.1
    lazy refcounts: false
    corrupt: false
[root@rhel7_test ~]# virsh pool-refresh default
error: Failed to refresh pool default
error: unsupported configuration: missing volume name and path for gluster volume

2. storage file backed by iscsi://$IP
# qemu-img create -f qcow2 /var/lib/libvirt/images/iscsi.img 100M
Formatting '/var/lib/libvirt/images/iscsi.img', fmt=qcow2 size=104857600 encryption=off cluster_size=65536 lazy_refcounts=off 
# qemu-img rebase -u -f qcow2 -F raw -b iscsi://10.66.5.155 /var/lib/libvirt/images/iscsi.img
# qemu-img info /var/lib/libvirt/images/iscsi.img
image: /var/lib/libvirt/images/iscsi.img
file format: qcow2
virtual size: 100M (104857600 bytes)
disk size: 196K
cluster_size: 65536
backing file: iscsi://10.66.5.155
backing file format: raw
Format specific information:
    compat: 1.1
    lazy refcounts: false
# virsh pool-refresh default
Pool default refreshed

[root@ibm-x3650m4-04 ~]# virsh vol-list default
 Name                 Path                                    
------------------------------------------------------------------------------
 iscsi.img            /var/lib/libvirt/images/iscsi.img

# virsh vol-dumpxml iscsi.img default
<volume type='file'>
  <name>iscsi.img</name>
  <key>/var/lib/libvirt/images/iscsi.img</key>
  <source>
  </source>
  <capacity unit='bytes'>104857600</capacity>
  <allocation unit='bytes'>200704</allocation>
  <target>
    <path>/var/lib/libvirt/images/iscsi.img</path>
    <format type='qcow2'/>
    <permissions>
      <mode>0644</mode>
      <owner>0</owner>
      <group>0</group>
      <label>unconfined_u:object_r:virt_image_t:s0</label>
    </permissions>
    <timestamps>
      <atime>1424927649.973662076</atime>
      <mtime>1424927643.008717986</mtime>
      <ctime>1424927643.008717986</ctime>
    </timestamps>
    <compat>1.1</compat>
    <features/>
  </target>
  <backingStore>
    <path>iscsi://10.66.5.155</path>
    <format type='raw'/>
  </backingStore>
</volume>

3. storage file backed by nbd://localhost
# qemu-img create -f qcow2 /var/lib/libvirt/images/nbd.img 100M
Formatting '/var/lib/libvirt/images/nbd.img', fmt=qcow2 size=104857600 encryption=off cluster_size=65536 lazy_refcounts=off 
[root@rhel7_test ~]# qemu-img rebase -u -f qcow2 -F raw -b nbd://localhost /var/lib/libvirt/images/nbd.img
[root@rhel7_test ~]# qemu-img info /var/lib/libvirt/images/nbd.img
image: /var/lib/libvirt/images/nbd.img
file format: qcow2
virtual size: 100M (104857600 bytes)
disk size: 196K
cluster_size: 65536
backing file: nbd://localhost
backing file format: raw
Format specific information:
    compat: 1.1
    lazy refcounts: false
    corrupt: false
[root@rhel7_test ~]# virsh pool-refresh default
Pool default refreshed

[root@rhel7_test ~]# virsh vol-info nbd.img default
Name:           nbd.img
Type:           file
Capacity:       100.00 MiB
Allocation:     196.00 KiB

4.storage file backed by rbd://localhost
# qemu-img create -f qcow2 /var/lib/libvirt/images/rbd.img 100M
Formatting '/var/lib/libvirt/images/rbd.img', fmt=qcow2 size=104857600 encryption=off cluster_size=65536 lazy_refcounts=off 
[root@rhel7_test ~]# qemu-img rebase -u -f qcow2 -F raw -b rbd://localhost /var/lib/libvirt/images/rbd.img
[root@rhel7_test ~]# qemu-img info /var/lib/libvirt/images/rbd.img
image: /var/lib/libvirt/images/rbd.img
file format: qcow2
virtual size: 100M (104857600 bytes)
disk size: 196K
cluster_size: 65536
backing file: rbd://localhost
backing file format: raw
Format specific information:
    compat: 1.1
    lazy refcounts: false
    corrupt: false
[root@rhel7_test ~]# virsh pool-refresh default
Pool default refreshed

[root@rhel7_test ~]# virsh vol-info rbd.img default
Name:           rbd.img
Type:           file
Capacity:       100.00 MiB
Allocation:     196.00 KiB

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, 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://rhn.redhat.com/errata/RHBA-2015-2202.html