[PATCH 4/5] virnetdevtap: add virNetDevTapGetName

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

This will be used on a tap file descriptor returned by the bridge helper
to populate the <target> element, because the helper does not provide
the interface name.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 src/libvirt_private.syms |  1 +
 src/util/virnetdevtap.c  | 33 +++++++++++++++++++++++++++++++++
 src/util/virnetdevtap.h  |  3 +++
 3 files changed, 37 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index f241ec4..06085ba 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1515,6 +1515,7 @@ virNetDevOpenvswitchSetMigrateData;
 virNetDevTapCreate;
 virNetDevTapCreateInBridgePort;
 virNetDevTapDelete;
+virNetDevTapGetName;
 
 
 # util/virnetdevveth.h
diff --git a/src/util/virnetdevtap.c b/src/util/virnetdevtap.c
index a884de1..e9fddf1 100644
--- a/src/util/virnetdevtap.c
+++ b/src/util/virnetdevtap.c
@@ -44,6 +44,39 @@
 #define VIR_FROM_THIS VIR_FROM_NONE
 
 /**
+ * virNetDevTapGetName:
+ * @tapfd: a tun/tap file descriptor
+ * @ifname: a pointer that will receive the interface name
+ *
+ * Retrieve the interface name given a file descriptor for a tun/tap
+ * interface.
+ *
+ * Returns 0 if the interface name is successfully queried, -1 otherwise
+ */
+int
+virNetDevTapGetName(int tapfd, char **ifname)
+{
+#ifdef TUNGETIFF
+    struct ifreq ifr;
+
+    /* The kernel will always return -1 at this point.
+     * If TUNGETIFF is not implemented then errno == EBADFD.
+     */
+    if (ioctl(tapfd, TUNGETIFF, &ifr) < 0) {
+        virReportSystemError(errno, "%s",
+                             _("Unable to query tap interface name"));
+        return -1;
+    }
+
+    *ifname = strdup(ifr.ifr_name);
+    return 0;
+#else
+    return -1;
+#endif
+}
+
+
+/**
  * virNetDevProbeVnetHdr:
  * @tapfd: a tun/tap file descriptor
  *
diff --git a/src/util/virnetdevtap.h b/src/util/virnetdevtap.h
index 980db61..6bfc80c 100644
--- a/src/util/virnetdevtap.h
+++ b/src/util/virnetdevtap.h
@@ -35,6 +35,9 @@ int virNetDevTapCreate(char **ifname,
 int virNetDevTapDelete(const char *ifname)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
 
+int virNetDevTapGetName(int tapfd, char **ifname)
+    ATTRIBUTE_NONNULL(2) ATTRIBUTE_RETURN_CHECK;
+
 typedef enum {
    VIR_NETDEV_TAP_CREATE_NONE = 0,
    /* Bring the interface up */
-- 
1.8.1.4


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