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Bug 1035336

Summary: iptables rules not properly updated in some cases by net-update
Product: Red Hat Enterprise Linux 7 Reporter: Laine Stump <laine>
Component: libvirtAssignee: Laine Stump <laine>
Status: CLOSED CURRENTRELEASE QA Contact: Virtualization Bugs <virt-bugs>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 7.0CC: acathrow, dallan, dyuan, gsun, honzhang, mzhan
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: libvirt-1.1.1-15.el7 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2014-06-13 10:43:38 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Laine Stump 2013-11-27 15:07:33 UTC 
1) if the change to a network definition causes the dhcp service for the network to be no longer needed (or creates the need for a dhcp service), the mangle rule that fixes up the checksum of DHCP responses will not be added/removed.

2) In general, if any change to the network would create the need for a change in the iptables rules for that network, libvirt attempts to remove the *new* rules, then re-add those same rules (because it is doing its rule removal after updating the network definition. Instead, the old rules should be removed based on the old state of the network definition, then after updating the definition, new rules should be added.


(1) can result in a failure to get dhcp addresses by some older clients. (2) can result in old unwanted iptables rules sticking around on the system. These rules may or may not have an adverse effect.
Comment 1 Laine Stump 2013-12-11 11:19:08 UTC 
The following patch was pushed upstream:

commit 54f9492353170b1ffc78a44c06ed3f9ecaab6ccf
Author: Laine Stump <laine>
Date:   Wed Nov 27 17:07:34 2013 +0200

    network: properly update iptables rules during net-update
Comment 4 hongming 2013-12-19 06:43:03 UTC 
Verify it as follows. The result is expected.Move its status to VERIFIED.

Versions
libvirt-1.1.1-15.el7.x86_64
qemu-kvm-1.5.3-19.el7.x86_64
kernel-3.10.0-33.el7.x86_64


[root@localhost images]# virsh net-list 
 Name                 State      Autostart     Persistent
----------------------------------------------------------
 default1             active     no            yes

[root@localhost images]# virsh net-dumpxml default1
<network>
  <name>default1</name>
  <uuid>7392199b-dd2e-44f5-a260-1f71ee9db6fb</uuid>
  <forward mode='nat'>
    <nat>
      <port start='1024' end='65535'/>
    </nat>
  </forward>
  <bridge name='virbr1' stp='on' delay='0' />
  <mac address='52:54:00:71:f8:62'/>
  <ip address='192.168.122.1' netmask='255.255.255.0'>
    <dhcp>
      <range start='192.168.122.2' end='192.168.122.254' />
      <host mac='12:34:56:78:90:ac' name='aaa' ip='192.168.122.123' />
    </dhcp>
  </ip>
</network>

[root@localhost images]# iptables -L POSTROUTING -t nat
Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination         
MASQUERADE  tcp  --  192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
MASQUERADE  udp  --  192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
MASQUERADE  all  --  192.168.122.0/24    !192.168.122.0/24    
POSTROUTING_direct  all  --  anywhere             anywhere            
POSTROUTING_ZONES_SOURCE  all  --  anywhere             anywhere            
POSTROUTING_ZONES  all  --  anywhere             anywhere            

[root@localhost images]# virsh net-update default1 delete ip-dhcp-host "<host mac='12:34:56:78:90:ac' name='aaa' ip='192.168.122.123' />"
Updated network default1 live state

[root@localhost images]# virsh net-update default1 add ip-dhcp-host "<host mac='12:34:56:78:90:ac' name='bbb' ip='192.168.122.123' />"
Updated network default1 live state

[root@localhost images]# cat /var/lib/libvirt/dnsmasq/default1.hostsfile
12:34:56:78:90:ac,192.168.122.123,bbb

[root@localhost images]# iptables -L POSTROUTING -t nat
Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination         
MASQUERADE  tcp  --  192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
MASQUERADE  udp  --  192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
MASQUERADE  all  --  192.168.122.0/24    !192.168.122.0/24    
POSTROUTING_direct  all  --  anywhere             anywhere            
POSTROUTING_ZONES_SOURCE  all  --  anywhere             anywhere            
POSTROUTING_ZONES  all  --  anywhere             anywhere            

[root@localhost images]# virsh net-update default1 delete ip-dhcp-range "<range start='192.168.122.2' end='192.168.122.254' />"
Updated network default1 live state

[root@localhost images]# virsh net-update default1 add ip-dhcp-range "<range start='192.168.122.3' end='192.168.122.253' />"
Updated network default1 live state

[root@localhost images]# cat /var/lib/libvirt/dnsmasq/default1.conf|grep dhcp-range
dhcp-range=192.168.122.3,192.168.122.253

[root@localhost images]# iptables -L POSTROUTING -t nat
Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination         
MASQUERADE  tcp  --  192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
MASQUERADE  udp  --  192.168.122.0/24    !192.168.122.0/24     masq ports: 1024-65535
MASQUERADE  all  --  192.168.122.0/24    !192.168.122.0/24    
POSTROUTING_direct  all  --  anywhere             anywhere            
POSTROUTING_ZONES_SOURCE  all  --  anywhere             anywhere            
POSTROUTING_ZONES  all  --  anywhere             anywhere  

Check guest' network simultaneously ,it works fine
Comment 5 Ludek Smid 2014-06-13 10:43:38 UTC 
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.