virNetDevMacVLanTapSetup: Rework to support multiple FDs

For the multiqueue on macvtaps we are going to need to open
the device multiple times. Currently, this is not supported.
Rework the function, so that upper layers can be reworked too.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/util/virnetdevmacvlan.c

@@ -286,10 +286,9 @@ virNetDevMacVLanTapOpen(const char *ifname,
 
 /**
  * virNetDevMacVLanTapSetup:
- * @tapfd: file descriptor of the macvtap tap
- * @vnet_hdr: 1 to enable IFF_VNET_HDR, 0 to disable it
- *
- * Returns 0 on success, -1 in case of fatal error, error code otherwise.
+ * @tapfd: array of file descriptors of the macvtap tap
+ * @tapfdSize: number of file descriptors in @tapfd
+ * @vnet_hdr: whether to enable or disable IFF_VNET_HDR
  *
  * Turn the IFF_VNET_HDR flag, if requested and available, make sure
  * it's off in the other cases.
@@ -297,47 +296,52 @@ virNetDevMacVLanTapOpen(const char *ifname,
  * be turned off for some reason. This is reported with -1. Other fatal
  * error is not being able to read the interface flags. In that case the
  * macvtap device should not be used.
+ *
+ * Returns 0 on success, -1 in case of fatal error, error code otherwise.
  */
 static int
-virNetDevMacVLanTapSetup(int tapfd, int vnet_hdr)
+virNetDevMacVLanTapSetup(int *tapfd, size_t tapfdSize, bool vnet_hdr)
 {
     unsigned int features;
     struct ifreq ifreq;
     short new_flags = 0;
     int rc_on_fail = 0;
     const char *errmsg = NULL;
+    size_t i;
 
-    memset(&ifreq, 0, sizeof(ifreq));
-
-    if (ioctl(tapfd, TUNGETIFF, &ifreq) < 0) {
-        virReportSystemError(errno, "%s",
-                             _("cannot get interface flags on macvtap tap"));
-        return -1;
-    }
-
-    new_flags = ifreq.ifr_flags;
+    for (i = 0; i < tapfdSize; i++) {
+        memset(&ifreq, 0, sizeof(ifreq));
 
-    if ((ifreq.ifr_flags & IFF_VNET_HDR) && !vnet_hdr) {
-        new_flags = ifreq.ifr_flags & ~IFF_VNET_HDR;
-        rc_on_fail = -1;
-        errmsg = _("cannot clean IFF_VNET_HDR flag on macvtap tap");
-    } else if ((ifreq.ifr_flags & IFF_VNET_HDR) == 0 && vnet_hdr) {
-        if (ioctl(tapfd, TUNGETFEATURES, &features) < 0) {
+        if (ioctl(tapfd[i], TUNGETIFF, &ifreq) < 0) {
             virReportSystemError(errno, "%s",
-                   _("cannot get feature flags on macvtap tap"));
+                                 _("cannot get interface flags on macvtap tap"));
             return -1;
         }
-        if ((features & IFF_VNET_HDR)) {
-            new_flags = ifreq.ifr_flags | IFF_VNET_HDR;
-            errmsg = _("cannot set IFF_VNET_HDR flag on macvtap tap");
+
+        new_flags = ifreq.ifr_flags;
+
+        if ((ifreq.ifr_flags & IFF_VNET_HDR) && !vnet_hdr) {
+            new_flags = ifreq.ifr_flags & ~IFF_VNET_HDR;
+            rc_on_fail = -1;
+            errmsg = _("cannot clean IFF_VNET_HDR flag on macvtap tap");
+        } else if ((ifreq.ifr_flags & IFF_VNET_HDR) == 0 && vnet_hdr) {
+            if (ioctl(tapfd[i], TUNGETFEATURES, &features) < 0) {
+                virReportSystemError(errno, "%s",
+                                     _("cannot get feature flags on macvtap tap"));
+                return -1;
+            }
+            if ((features & IFF_VNET_HDR)) {
+                new_flags = ifreq.ifr_flags | IFF_VNET_HDR;
+                errmsg = _("cannot set IFF_VNET_HDR flag on macvtap tap");
+            }
         }
-    }
 
-    if (new_flags != ifreq.ifr_flags) {
-        ifreq.ifr_flags = new_flags;
-        if (ioctl(tapfd, TUNSETIFF, &ifreq) < 0) {
-            virReportSystemError(errno, "%s", errmsg);
-            return rc_on_fail;
+        if (new_flags != ifreq.ifr_flags) {
+            ifreq.ifr_flags = new_flags;
+            if (ioctl(tapfd[i], TUNSETIFF, &ifreq) < 0) {
+                virReportSystemError(errno, "%s", errmsg);
+                return rc_on_fail;
+            }
         }
     }
 
@@ -848,7 +852,7 @@ int virNetDevMacVLanCreateWithVPortProfile(const char *tgifname,
         if (virNetDevMacVLanTapOpen(cr_ifname, &rc, 1, 10) < 0)
             goto disassociate_exit;
 
-        if (virNetDevMacVLanTapSetup(rc, vnet_hdr) < 0) {
+        if (virNetDevMacVLanTapSetup(&rc, 1, vnet_hdr) < 0) {
             VIR_FORCE_CLOSE(rc); /* sets rc to -1 */
             goto disassociate_exit;
         }