qemu: set default vhost-user ifname

Based on work of Mehdi Abaakouk <sileht@sileht.net>.

When parsing vhost-user interface XML and no ifname is found we
can try to fill it in in post parse callback. The way this works
is we try to make up interface name from given socket path and
then ask openvswitch whether it knows the interface.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

src/libvirt_private.syms

@@ -2072,6 +2072,7 @@ virNetDevMidonetUnbindPort;
 # util/virnetdevopenvswitch.h
 virNetDevOpenvswitchAddPort;
 virNetDevOpenvswitchGetMigrateData;
+virNetDevOpenvswitchGetVhostuserIfname;
 virNetDevOpenvswitchInterfaceStats;
 virNetDevOpenvswitchRemovePort;
 virNetDevOpenvswitchSetMigrateData;

src/qemu/qemu_domain.c

@@ -41,6 +41,7 @@
 #include "domain_addr.h"
 #include "domain_event.h"
 #include "virtime.h"
+#include "virnetdevopenvswitch.h"
 #include "virstoragefile.h"
 #include "virstring.h"
 #include "virthreadjob.h"
@@ -3004,13 +3005,21 @@ qemuDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
                                           def->emulator);
     }
 
-    if (dev->type == VIR_DOMAIN_DEVICE_NET &&
-        dev->data.net->type != VIR_DOMAIN_NET_TYPE_HOSTDEV &&
+    if (dev->type == VIR_DOMAIN_DEVICE_NET) {
+        if (dev->data.net->type != VIR_DOMAIN_NET_TYPE_HOSTDEV &&
             !dev->data.net->model) {
             if (VIR_STRDUP(dev->data.net->model,
                            qemuDomainDefaultNetModel(def, qemuCaps)) < 0)
                 goto cleanup;
         }
+        if (dev->data.net->type == VIR_DOMAIN_NET_TYPE_VHOSTUSER &&
+            !dev->data.net->ifname) {
+            if (virNetDevOpenvswitchGetVhostuserIfname(
+                   dev->data.net->data.vhostuser->data.nix.path,
+                   &dev->data.net->ifname) < 0)
+                goto cleanup;
+        }
+    }
 
     /* set default disk types and drivers */
     if (dev->type == VIR_DOMAIN_DEVICE_DISK) {

src/util/virnetdevopenvswitch.c

@@ -377,3 +377,56 @@ virNetDevOpenvswitchInterfaceStats(const char *ifname,
     virCommandFree(cmd);
     return ret;
 }
+
+/**
+ * virNetDevOpenvswitchVhostuserGetIfname:
+ * @path: the path of the unix socket
+ * @ifname: the retrieved name of the interface
+ *
+ * Retreives the ovs ifname from vhostuser unix socket path.
+ *
+ * Returns: 1 if interface is an openvswitch interface,
+ *          0 if it is not, but no other error occurred,
+ *         -1 otherwise.
+ */
+int
+virNetDevOpenvswitchGetVhostuserIfname(const char *path,
+                                       char **ifname)
+{
+    virCommandPtr cmd = NULL;
+    char *tmpIfname = NULL;
+    char **tokens = NULL;
+    size_t ntokens = 0;
+    int status;
+    int ret = -1;
+
+    /* Openvswitch vhostuser path are hardcoded to
+     * /<runstatedir>/openvswitch/<ifname>
+     * for example: /var/run/openvswitch/dpdkvhostuser0
+     *
+     * so we pick the filename and check it's a openvswitch interface
+     */
+    if (!path ||
+        !(tmpIfname = strrchr(path, '/'))) {
+        ret = 0;
+        goto cleanup;
+    }
+
+    cmd = virCommandNewArgList(OVSVSCTL, "--timeout=5", "get", "Interface",
+                               tmpIfname, "name", NULL);
+    if (virCommandRun(cmd, &status) < 0 ||
+        status) {
+        /* it's not a openvswitch vhostuser interface. */
+        ret = 0;
+        goto cleanup;
+    }
+
+    if (VIR_STRDUP(*ifname, tmpIfname) < 0)
+        goto cleanup;
+    ret = 1;
+
+ cleanup:
+    virStringListFreeCount(tokens, ntokens);
+    virCommandFree(cmd);
+    return ret;
+}

src/util/virnetdevopenvswitch.h

@@ -52,4 +52,8 @@ int virNetDevOpenvswitchInterfaceStats(const char *ifname,
                                        virDomainInterfaceStatsPtr stats)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
 
+int virNetDevOpenvswitchGetVhostuserIfname(const char *path,
+                                           char **ifname)
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_RETURN_CHECK;
+
 #endif /* __VIR_NETDEV_OPENVSWITCH_H__ */

tests/Makefile.am

@@ -281,6 +281,7 @@ test_helpers += qemucapsprobe
 test_libraries += libqemumonitortestutils.la \
 		libqemutestdriver.la \
 		qemuxml2argvmock.la \
+		qemuxml2xmlmock.la \
 		qemucaps2xmlmock.la \
 		qemucapsprobemock.la \
 		$(NULL)
@@ -558,6 +559,12 @@ qemuxml2argvmock_la_CFLAGS = $(AM_CFLAGS)
 qemuxml2argvmock_la_LDFLAGS = $(MOCKLIBS_LDFLAGS)
 qemuxml2argvmock_la_LIBADD = $(MOCKLIBS_LIBS)
 
+qemuxml2xmlmock_la_SOURCES = \
+	qemuxml2xmlmock.c
+qemuxml2xmlmock_la_CFLAGS = $(AM_CFLAGS)
+qemuxml2xmlmock_la_LDFLAGS = $(MOCKLIBS_LDFLAGS)
+qemuxml2xmlmock_la_LIBADD = $(MOCKLIBS_LIBS)
+
 qemuxml2xmltest_SOURCES = \
 	qemuxml2xmltest.c testutilsqemu.c testutilsqemu.h \
 	testutils.c testutils.h

tests/qemuxml2argvmock.c

@@ -28,6 +28,7 @@
 #include "virnetdev.h"
 #include "virnetdevip.h"
 #include "virnetdevtap.h"
+#include "virnetdevopenvswitch.h"
 #include "virnuma.h"
 #include "virrandom.h"
 #include "virscsi.h"
@@ -180,3 +181,10 @@ virCryptoGenerateRandom(size_t nbytes)
 
     return buf;
 }
+
+int
+virNetDevOpenvswitchGetVhostuserIfname(const char *path ATTRIBUTE_UNUSED,
+                                       char **ifname)
+{
+    return VIR_STRDUP(*ifname, "vhost-user0");
+}

tests/qemuxml2xmlmock.c

@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Author: Michal Privoznik <mprivozn@redhat.com>
+ */
+
+#include <config.h>
+
+#include "virnetdevopenvswitch.h"
+#include "virstring.h"
+
+#define VIR_FROM_THIS VIR_FROM_NONE
+
+int
+virNetDevOpenvswitchGetVhostuserIfname(const char *path ATTRIBUTE_UNUSED,
+                                       char **ifname)
+{
+    return VIR_STRDUP(*ifname, "vhost-user0");
+}

tests/qemuxml2xmloutdata/qemuxml2xmlout-net-vhostuser.xml

@@ -30,12 +30,14 @@
     <interface type='vhostuser'>
       <mac address='52:54:00:ee:96:6b'/>
       <source type='unix' path='/tmp/vhost0.sock' mode='server'/>
+      <target dev='vhost-user0'/>
       <model type='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
     </interface>
     <interface type='vhostuser'>
       <mac address='52:54:00:ee:96:6c'/>
       <source type='unix' path='/tmp/vhost1.sock' mode='client'/>
+      <target dev='vhost-user0'/>
       <model type='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
     </interface>

tests/qemuxml2xmltest.c

@@ -1059,7 +1059,7 @@ mymain(void)
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }
 
-VIRT_TEST_MAIN(mymain)
+VIRT_TEST_MAIN_PRELOAD(mymain, abs_builddir "/.libs/qemuxml2xmlmock.so")
 
 #else