[libvirt] [PATCH] qemu: support live update of an interface's filter

[Laine Stump]

Since we can't (currently) rely on the ability to provide blanket
support for all possible network changes by calling the toplevel
netdev hostside disconnect/connect functions (due to qemu only
supporting a lockstep between initialization of host side and guest
side of devices), in order to support live change of an interface's
nwfilter we need to make a special purpose function to only call the
nwfilter teardown and setup functions if the filter for an interface
(or its parameters) changes. The pattern is nearly identical to that
used to change the bridge that an interface is connected to.

This patch was inspired by a request from Guido Winkelmann
<guido at sagersystems.de>, who tested an earlier version, and wrote an
initial version of the nwfilterHashTable comparison function.

I didn't spend any time trying to understand the contents of the
nwfilterHashTable entries, or whether the comparison function is
fully/correctly comparing the entries. I would appreciate if someone
with better knowledge of that data structure (Stefan?) could check it
out and provide suggestions.
---
 src/conf/nwfilter_params.c | 24 ++++++++++++++++++++
 src/conf/nwfilter_params.h |  4 +++-
 src/libvirt_private.syms   |  1 +
 src/qemu/qemu_hotplug.c    | 55 +++++++++++++++++++++++++++++++++++++++++++---
 4 files changed, 80 insertions(+), 4 deletions(-)

diff --git a/src/conf/nwfilter_params.c b/src/conf/nwfilter_params.c
index 6dc4baa..e42a54c 100644
--- a/src/conf/nwfilter_params.c
+++ b/src/conf/nwfilter_params.c
@@ -764,6 +764,30 @@ err_exit:
     return -1;
 }
 
+static int
+virNWFilterHashTableCompare(const void *a, const void *b)
+{
+    /* need to return 0 if equal */
+    return STRNEQ_NULLABLE(a, b);
+}
+
+bool
+virNWFilterHashTableEqual(virNWFilterHashTablePtr a,
+                          virNWFilterHashTablePtr b)
+{
+    if (!(a || b))
+        return true;
+    if (!(a && b))
+        return false;
+    if (a->nNames != b->nNames)
+        return false;
+    if (!(a->hashTable || b->hashTable))
+        return true;
+    if (!(a->hashTable && b->hashTable))
+        return false;
+
+    return virHashEqual(a->hashTable, b->hashTable, virNWFilterHashTableCompare);
+}
 
 static bool
 isValidVarName(const char *var)
diff --git a/src/conf/nwfilter_params.h b/src/conf/nwfilter_params.h
index cedf9cd..e310bb1 100644
--- a/src/conf/nwfilter_params.h
+++ b/src/conf/nwfilter_params.h
@@ -1,7 +1,7 @@
 /*
  * nwfilter_params.h: parsing and data maintenance of filter parameters
  *
- * Copyright (C) 2011 Red Hat, Inc.
+ * Copyright (C) 2011-2012 Red Hat, Inc.
  * Copyright (C) 2010 IBM Corporation
  *
  * This library is free software; you can redistribute it and/or
@@ -85,6 +85,8 @@ void *virNWFilterHashTableRemoveEntry(virNWFilterHashTablePtr table,
                                       const char *name);
 int virNWFilterHashTablePutAll(virNWFilterHashTablePtr src,
                                virNWFilterHashTablePtr dest);
+bool virNWFilterHashTableEqual(virNWFilterHashTablePtr a,
+                               virNWFilterHashTablePtr b);
 
 # define VALID_VARNAME \
   "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_"
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 756d7bd..d637142 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -946,6 +946,7 @@ virNWFilterIPAddrMapShutdown;
 
 # nwfilter_params.h
 virNWFilterHashTableCreate;
+virNWFilterHashTableEqual;
 virNWFilterHashTableFree;
 virNWFilterHashTablePut;
 virNWFilterHashTablePutAll;
diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index ae8381e..581204a 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -1330,6 +1330,43 @@ cleanup:
     return ret;
 }
 
+static int
+qemuDomainChangeNetFilter(virConnectPtr conn,
+                          virDomainObjPtr vm,
+                          virDomainNetDefPtr olddev,
+                          virDomainNetDefPtr newdev)
+{
+    /* make sure this type of device supports filters. */
+    switch (virDomainNetGetActualType(newdev)) {
+    case VIR_DOMAIN_NET_TYPE_ETHERNET:
+    case VIR_DOMAIN_NET_TYPE_BRIDGE:
+    case VIR_DOMAIN_NET_TYPE_NETWORK:
+        break;
+    default:
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("filters not supported on interfaces of type %s"),
+                       virDomainNetTypeToString(virDomainNetGetActualType(newdev)));
+        return -1;
+    }
+
+    virDomainConfNWFilterTeardown(olddev);
+
+    if (virDomainConfNWFilterInstantiate(conn, vm->def->uuid, newdev) < 0) {
+        virErrorPtr errobj;
+
+        virReportError(VIR_ERR_OPERATION_FAILED,
+                       _("failed to add new filter rules to '%s' "
+                         "- attempting to restore old rules"),
+                       olddev->ifname);
+        errobj = virSaveLastError();
+        ignore_value(virDomainConfNWFilterInstantiate(conn, vm->def->uuid, olddev));
+        virSetError(errobj);
+        virFreeError(errobj);
+        return -1;
+    }
+    return 0;
+}
+
 int qemuDomainChangeNetLinkState(struct qemud_driver *driver,
                                  virDomainObjPtr vm,
                                  virDomainNetDefPtr dev,
@@ -1373,6 +1410,7 @@ qemuDomainChangeNet(struct qemud_driver *driver,
     int oldType, newType;
     bool needReconnect = false;
     bool needBridgeChange = false;
+    bool needFilterChange = false;
     bool needLinkStateChange = false;
     bool needReplaceDevDef = false;
     int ret = -1;
@@ -1506,8 +1544,10 @@ qemuDomainChangeNet(struct qemud_driver *driver,
     }
     /* (end of device info checks) */
 
-    if (STRNEQ_NULLABLE(olddev->filter, newdev->filter))
-        needReconnect = true;
+    if (STRNEQ_NULLABLE(olddev->filter, newdev->filter) ||
+        !virNWFilterHashTableEqual(olddev->filterparams, newdev->filterparams)) {
+        needFilterChange = true;
+    }
 
     /* bandwidth can be modified, and will be checked later */
     /* vlan can be modified, and will be checked later */
@@ -1665,7 +1705,16 @@ qemuDomainChangeNet(struct qemud_driver *driver,
             goto cleanup;
         /* we successfully switched to the new bridge, and we've
          * determined that the rest of newdev is equivalent to olddev,
-         * so move newdev into place, so that the  */
+         * so move newdev into place */
+        needReplaceDevDef = true;
+    }
+
+    if (needFilterChange) {
+        if (qemuDomainChangeNetFilter(dom->conn, vm, olddev, newdev) < 0)
+            goto cleanup;
+        /* we successfully switched to the new filter, and we've
+         * determined that the rest of newdev is equivalent to olddev,
+         * so move newdev into place */
         needReplaceDevDef = true;
     }
 
-- 
1.7.11.7