[libvirt] [PATCH v2 1/1] qemu_domain: set default ovs vhostuser ifname

[Mehdi Abaakouk]

This change adds a new helper function that
return a ifname from the vhostuser unix-socket path but only
if the interface is managed by openvswitch

This new function is issue to autodetect the ifname for openvswitch
managed vhostuser interface.
---
 src/libvirt_private.syms        |  1 +
 src/qemu/qemu_domain.c          | 21 +++++++++++++++------
 src/util/virnetdevopenvswitch.c | 42 +++++++++++++++++++++++++++++++++++++++++
 src/util/virnetdevopenvswitch.h |  3 +++
 4 files changed, 61 insertions(+), 6 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 2d23e462d..9e4e8f83f 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2057,6 +2057,7 @@ virNetDevMidonetUnbindPort;
 # util/virnetdevopenvswitch.h
 virNetDevOpenvswitchAddPort;
 virNetDevOpenvswitchGetMigrateData;
+virNetDevOpenvswitchGetVhostuserIfname;
 virNetDevOpenvswitchInterfaceStats;
 virNetDevOpenvswitchRemovePort;
 virNetDevOpenvswitchSetMigrateData;
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index acfa69589..7ae487821 100644
--- a/src/qemu/qemu_domain.c
+++ b/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"
@@ -3028,12 +3029,20 @@ qemuDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
                                           def->emulator);
     }
 
-    if (dev->type == VIR_DOMAIN_DEVICE_NET &&
-        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->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 (VIR_STRDUP(dev->data.net->ifname,
+                virNetDevOpenvswitchGetVhostuserIfname(
+                    dev->data.net->data.vhostuser->data.nix.path)) < 0)
+                goto cleanup;
+        }
     }
 
     /* set default disk types and drivers */
diff --git a/src/util/virnetdevopenvswitch.c b/src/util/virnetdevopenvswitch.c
index f003b3b13..41933ce28 100644
--- a/src/util/virnetdevopenvswitch.c
+++ b/src/util/virnetdevopenvswitch.c
@@ -377,3 +377,45 @@ virNetDevOpenvswitchInterfaceStats(const char *ifname,
     virCommandFree(cmd);
     return ret;
 }
+
+/**
+ * virNetDevOpenvswitchVhostuserGetIfname:
+ * @path: the path of the unix socket
+ *
+ * Retreives the ovs ifname from vhostuser unix socket path
+ *
+ * Returns a new string which must be deallocated by caller or NULL
+ */
+char *
+virNetDevOpenvswitchGetVhostuserIfname(const char *path)
+{
+    virCommandPtr cmd = NULL;
+    char *ifname = NULL;
+    char **tokens = NULL;
+    size_t ntokens = 0;
+
+    /* 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 ((tokens = virStringSplitCount(path, "/", 0, &ntokens))) {
+         if (VIR_STRDUP(ifname, tokens[ntokens - 1]) < 0)
+             goto cleanup;
+    }
+    if (ifname != NULL) {
+        cmd = virCommandNewArgList(OVSVSCTL, "--timeout=5", "get", "Interface",
+                                   ifname, "name", NULL);
+        if (virCommandRun(cmd, NULL) < 0) {
+            /* it's not a openvswitch vhostuser interface */
+            VIR_FREE(ifname);
+        }
+    }
+
+ cleanup:
+    virStringListFreeCount(tokens, ntokens);
+    virCommandFree(cmd);
+    return ifname;
+
+}
diff --git a/src/util/virnetdevopenvswitch.h b/src/util/virnetdevopenvswitch.h
index 0f9e1dfa6..fe86e286f 100644
--- a/src/util/virnetdevopenvswitch.h
+++ b/src/util/virnetdevopenvswitch.h
@@ -52,4 +52,7 @@ int virNetDevOpenvswitchInterfaceStats(const char *ifname,
                                        virDomainInterfaceStatsPtr stats)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
 
+char *virNetDevOpenvswitchGetVhostuserIfname(const char *path)
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
+
 #endif /* __VIR_NETDEV_OPENVSWITCH_H__ */
-- 
2.11.0