From 1b46566eed0c9c23251d05c8fedb3522d711f5c0 Mon Sep 17 00:00:00 2001
From: Laine Stump <laine@redhat.com>
Date: Mon, 26 Aug 2019 01:24:08 -0400
Subject: [PATCH] util: new function virNetDevMacVLanIsMacvtap()
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This function returns T if the given name is a macvtap device. This is
determined by 1) getting the ifindex of the device with that name (if
there is one), and 2) checking for existence of /dev/tapXX, where "XX"
is the ifindex learned in (1).

It's also possible to learn this by getting a netlink dump of the
interface and parsing through it to look for some attributes, but that
is complicated to figure out, takes longer to execute, and I'm lazy.

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 src/libvirt_private.syms    |  1 +
 src/util/virnetdevmacvlan.c | 23 +++++++++++++++++++++++
 src/util/virnetdevmacvlan.h |  3 +++
 3 files changed, 27 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index f1fe7259f9..7adb07aac0 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2524,6 +2524,7 @@ virNetDevMacVLanCreate;
 virNetDevMacVLanCreateWithVPortProfile;
 virNetDevMacVLanDelete;
 virNetDevMacVLanDeleteWithVPortProfile;
+virNetDevMacVLanIsMacvtap;
 virNetDevMacVLanModeTypeFromString;
 virNetDevMacVLanReleaseName;
 virNetDevMacVLanReserveName;
diff --git a/src/util/virnetdevmacvlan.c b/src/util/virnetdevmacvlan.c
index 3302522289..79aa7ed5ac 100644
--- a/src/util/virnetdevmacvlan.c
+++ b/src/util/virnetdevmacvlan.c
@@ -278,6 +278,29 @@ virNetDevMacVLanReleaseName(const char *name)
 }
 
 
+/**
+ * virNetDevMacVLanIsMacvtap:
+ * @ifname: Name of the interface
+ *
+ * Return T if the named netdev exists and is a macvtap device
+ * F in all other cases.
+ */
+bool
+virNetDevMacVLanIsMacvtap(const char *ifname)
+{
+    int ifindex;
+    VIR_AUTOFREE(char *) tapname = NULL;
+
+    if (virNetDevGetIndex(ifname, &ifindex) < 0)
+        return false;
+
+    if (virAsprintf(&tapname, "/dev/tap%d", ifindex) < 0)
+        return false;
+
+    return virFileExists(tapname);
+}
+
+
 /**
  * virNetDevMacVLanCreate:
  *
diff --git a/src/util/virnetdevmacvlan.h b/src/util/virnetdevmacvlan.h
index d1b479ed9f..8ac7643e49 100644
--- a/src/util/virnetdevmacvlan.h
+++ b/src/util/virnetdevmacvlan.h
@@ -57,6 +57,9 @@ typedef enum {
 int virNetDevMacVLanReserveName(const char *name, bool quietfail);
 int virNetDevMacVLanReleaseName(const char *name);
 
+bool virNetDevMacVLanIsMacvtap(const char *ifname)
+   ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK ATTRIBUTE_NOINLINE;
+
 int virNetDevMacVLanCreate(const char *ifname,
                            const char *type,
                            const virMacAddr *macaddress,