[libvirt] [PATCH v2] libxl: free ifname on libxlDomainMigrationPrepareDef

[Joao Martins]

Commit d2e5538b1 changes virDomainDef to include ifnames
that autogenerated by libxl, and that are also cleared
on domain cleanup. One place that's missing is on
migration, when domain xml is sent to dst libvirtd and
would contain ifnames from the source libvirtd. This
would lead to erronous behaviour (as seen in osstest CI)
such as failing to migrate when a vif with the same name
existed (belonging to another domain) on destination.

This patch adds a helper libxlDomainFreeIfaceNames for
clearing ifnames on both migration prepare phase and domain
cleanup. It is done on prepare phase so that we don't affect
source domain (specially in cases when the migration fails),
while still allowing interface stats to be consulted during
the migration.

Signed-off-by: Joao Martins <joao.m.martins at oracle.com>
---
Changes since v1:
 - Commit message is changed
 - Clear ifnames on prepare phase as opposed to begin phase.
---
 src/libxl/libxl_domain.c    | 32 ++++++++++++++++++++++----------
 src/libxl/libxl_domain.h    |  3 +++
 src/libxl/libxl_migration.c |  2 ++
 3 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c
index ef92974..487589d 100644
--- a/src/libxl/libxl_domain.c
+++ b/src/libxl/libxl_domain.c
@@ -728,16 +728,7 @@ libxlDomainCleanup(libxlDriverPrivatePtr driver,
         }
     }
 
-    if ((vm->def->nnets)) {
-        size_t i;
-
-        for (i = 0; i < vm->def->nnets; i++) {
-            virDomainNetDefPtr net = vm->def->nets[i];
-
-            if (STRPREFIX(net->ifname, "vif"))
-                VIR_FREE(net->ifname);
-        }
-    }
+    libxlDomainFreeIfaceNames(vm->def);
 
     if (virAsprintf(&file, "%s/%s.xml", cfg->stateDir, vm->def->name) > 0) {
         if (unlink(file) < 0 && errno != ENOENT && errno != ENOTDIR)
@@ -923,6 +914,27 @@ libxlDomainCreateIfaceNames(virDomainDefPtr def, libxl_domain_config *d_config)
     }
 }
 
+/*
+ * Removes autogenerated interface names for the network devices in
+ * parameter def. User-provided interface names are skipped.
+ */
+void
+libxlDomainFreeIfaceNames(virDomainDefPtr def)
+{
+    size_t i;
+
+    for (i = 0; i < def->nnets; i++) {
+        virDomainNetDefPtr net = def->nets[i];
+
+        if (!net->ifname)
+            continue;
+
+        if (STRPREFIX(net->ifname, "vif"))
+            VIR_FREE(net->ifname);
+    }
+}
+
+
 
 /*
  * Start a domain through libxenlight.
diff --git a/src/libxl/libxl_domain.h b/src/libxl/libxl_domain.h
index 44b3e0b..70c139c 100644
--- a/src/libxl/libxl_domain.h
+++ b/src/libxl/libxl_domain.h
@@ -135,6 +135,9 @@ int
 libxlDomainSetVcpuAffinities(libxlDriverPrivatePtr driver,
                              virDomainObjPtr vm);
 
+void
+libxlDomainFreeIfaceNames(virDomainDefPtr def);
+
 int
 libxlDomainStart(libxlDriverPrivatePtr driver,
                  virDomainObjPtr vm,
diff --git a/src/libxl/libxl_migration.c b/src/libxl/libxl_migration.c
index 0d23e5f..1ca31ab 100644
--- a/src/libxl/libxl_migration.c
+++ b/src/libxl/libxl_migration.c
@@ -288,6 +288,8 @@ libxlDomainMigrationPrepareDef(libxlDriverPrivatePtr driver,
                                         VIR_DOMAIN_DEF_PARSE_INACTIVE)))
         goto cleanup;
 
+    libxlDomainFreeIfaceNames(def);
+
     if (dname) {
         name = def->name;
         if (VIR_STRDUP(def->name, dname) < 0) {
-- 
2.1.4