[libvirt] [PATCH] [nwfilter] Fix libvirt upgrade path when nwfilter is used

[Stefan Berger]

Between revision 65fb9d49 and before this patch, an upgrade of libvirt while
VMs are running and instantiating iptables filtering rules due to nwfilter
rules, may leave stray iptables rules behind when shutting VMs down.
Left-over iptables rules may look like this:

Chain FP-vnet0 (1 references)
target     prot opt source               destination
DROP       tcp  --  0.0.0.0/0            0.0.0.0/0            tcp spt:122
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0

[...]

Chain libvirt-out (1 references)
target     prot opt source               destination
FO-vnet0   all  --  0.0.0.0/0            0.0.0.0/0 [goto]  PHYSDEV match 
--physdev-out vnet0



The reason is that the recent nwfilter code only removed filtering rules in
the libvirt-out chain that contain the --physdev-is-bridged parameter.
Older rules didn't match and were not removed.

Note that the user-defined chain FO-vnet0 could not be removed due to the
reference from the rule in libvirt-out.

Often the work around may be done through

service iptables restart
kill -SIGHUP $(pidof libvirtd)

This patch now also removes older libvirt versions' iptables rules.

Signed-off-by: Stefan Berger <stefanb at linux.vnet.ibm.com>

---
  src/nwfilter/nwfilter_ebiptables_driver.c |   22 ++++++++++++++++++++++
  1 file changed, 22 insertions(+)

Index: libvirt-acl/src/nwfilter/nwfilter_ebiptables_driver.c
===================================================================
--- libvirt-acl.orig/src/nwfilter/nwfilter_ebiptables_driver.c
+++ libvirt-acl/src/nwfilter/nwfilter_ebiptables_driver.c
@@ -167,16 +167,24 @@ static const char ebiptables_script_set_

  #define PHYSDEV_IN  "--physdev-in"
  #define PHYSDEV_OUT "--physdev-is-bridged --physdev-out"
+/*
+ * Previous versions of libvirt only used --physdev-out.
+ * To be able to upgrade with running VMs we need to be able to
+ * remove rules generated by those older versions of libvirt.
+ */
+#define PHYSDEV_OUT_OLD  "--physdev-out"

  static const char *m_state_out_str   = "-m state --state NEW,ESTABLISHED";
  static const char *m_state_in_str    = "-m state --state ESTABLISHED";
  static const char *m_physdev_in_str  = "-m physdev " PHYSDEV_IN;
  static const char *m_physdev_out_str = "-m physdev " PHYSDEV_OUT;
+static const char *m_physdev_out_old_str = "-m physdev " PHYSDEV_OUT_OLD;

  #define MATCH_STATE_OUT    m_state_out_str
  #define MATCH_STATE_IN     m_state_in_str
  #define MATCH_PHYSDEV_IN   m_physdev_in_str
  #define MATCH_PHYSDEV_OUT  m_physdev_out_str
+#define MATCH_PHYSDEV_OUT_OLD  m_physdev_out_old_str

  #define COMMENT_VARNAME "comment"

@@ -821,6 +829,8 @@ _iptablesUnlinkRootChain(virBufferPtr bu
                                      : CHAINPREFIX_HOST_OUT;
      const char *match = (incoming) ? MATCH_PHYSDEV_IN
                                     : MATCH_PHYSDEV_OUT;
+    const char *old_match = (incoming) ? NULL
+                                       : MATCH_PHYSDEV_OUT_OLD;

      PRINT_IPT_ROOT_CHAIN(chain, chainPrefix, ifname);

@@ -830,6 +840,18 @@ _iptablesUnlinkRootChain(virBufferPtr bu
                        basechain,
                        match, ifname, chain);

+    /*
+     * Previous versions of libvirt may have created a rule
+     * with the --physdev-is-bridged missing. Remove this one
+     * as well.
+     */
+    if (old_match)
+        virBufferAsprintf(buf,
+                          "$IPT -D %s "
+                          "%s %s -g %s" CMD_SEPARATOR,
+                          basechain,
+                          old_match, ifname, chain);
+
      return 0;
  }