libxl/xend: name tap devices vifX.Y-emu

This prevents the udev scripts from operating on other tap devices (e.g.
openvpn etc)

Correct the documentation for the "vifname" option which suggested it applied
to HVM tap devices only, which is not the case.

Reported by Michael Young.

Also fix the use of vifname with emulated devices. This is slightly complex.
The current hotplug scripts rely on being able to parse the "tapX.Y" (now
"vifX.Y-emu") name in order to locate the xenstore backend dir relating to the
corresponding vif. This is because we cannot inject our own environment vars
into the tap hotplug events. However this means that if the tap is initially
named with a user specified name (which will not match the expected scheme) we
fail to do anything useful with the device. So now we create the initial tap
device with the standard "vifX.Y-emu" name and the hotplug script will handle
the rename to the desired name. This is also how PV vif devices work -- they
are always created by netback with the name vifX.Y and renamed in the script.

Lastly also move libxl__device_* to a better place in the header, otherwise the
comment about evgen stuff isn't next to the associated functions (noticed jsut
because I was going to add nic_devname near to the setdefault functions)

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson.citrix.com>

6 files changed, 52 insertions, 32 deletions

diff --git a/tools/hotplug/Linux/vif-common.sh b/tools/hotplug/Linux/vif-common.sh
index c9c5d41da0..fff22bbf9d 100644
--- a/tools/hotplug/Linux/vif-common.sh
+++ b/tools/hotplug/Linux/vif-common.sh
@@ -85,12 +85,23 @@ elif [ "$type_if" = tap ]; then
     : ${INTERFACE:?}
 
     # Get xenbus_path from device name.
-    # The name is built like that: "tap${domid}.${devid}".
-    dev_=${dev#tap}
+    # The name is built like that: "vif${domid}.${devid}-emu".
+    dev_=${dev#vif}
+    dev_=${dev_%-emu}
     domid=${dev_%.*}
     devid=${dev_#*.}
 
     XENBUS_PATH="/local/domain/0/backend/vif/$domid/$devid"
+    vifname=$(xenstore_read_default "$XENBUS_PATH/vifname" "")
+    if [ "$vifname" ]
+    then
+        vifname="${vifname}-emu"
+        if [ "$command" == "add" ] && ! ip link show "$vifname" >&/dev/null
+        then
+            do_or_die ip link set "$dev" name "$vifname"
+        fi
+        dev="$vifname"
+    fi
 fi
 
 ip=${ip:-}
diff --git a/tools/hotplug/Linux/xen-backend.rules b/tools/hotplug/Linux/xen-backend.rules
index 40f2658eb2..405387f1a9 100644
--- a/tools/hotplug/Linux/xen-backend.rules
+++ b/tools/hotplug/Linux/xen-backend.rules
@@ -13,4 +13,4 @@ KERNEL=="blktap-control", NAME="xen/blktap-2/control", MODE="0600"
 KERNEL=="gntdev", NAME="xen/%k", MODE="0600"
 KERNEL=="pci_iomul", NAME="xen/%k", MODE="0600"
 KERNEL=="tapdev[a-z]*", NAME="xen/blktap-2/tapdev%m", MODE="0600"
-SUBSYSTEM=="net", KERNEL=="tap*", ACTION=="add", RUN+="/etc/xen/scripts/vif-setup $env{ACTION} type_if=tap"
+SUBSYSTEM=="net", KERNEL=="vif*-emu", ACTION=="add", RUN+="/etc/xen/scripts/vif-setup $env{ACTION} type_if=tap"
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 14791d6e81..c420e19b69 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -2087,6 +2087,21 @@ int libxl_device_nic_getinfo(libxl_ctx *ctx, uint32_t domid,
     return 0;
 }
 
+const char *libxl__device_nic_devname(libxl__gc *gc,
+                                      uint32_t domid,
+                                      uint32_t devid,
+                                      libxl_nic_type type)
+{
+    switch (type) {
+    case LIBXL_NIC_TYPE_VIF:
+        return GCSPRINTF("vif%u.%d", domid, devid);
+    case LIBXL_NIC_TYPE_IOEMU:
+        return GCSPRINTF("vif%u.%d" TAP_DEVICE_SUFFIX, domid, devid);
+    default:
+        abort();
+    }
+}
+
 /******************************************************************************/
 int libxl__device_console_add(libxl__gc *gc, uint32_t domid,
                               libxl__device_console *console,
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 48c7ed52dc..ec967f784a 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -209,12 +209,9 @@ static char ** libxl__build_device_model_args_old(libxl__gc *gc,
             if (vifs[i].nictype == LIBXL_NIC_TYPE_IOEMU) {
                 char *smac = libxl__sprintf(gc,
                                    LIBXL_MAC_FMT, LIBXL_MAC_BYTES(vifs[i].mac));
-                char *ifname;
-                if (!vifs[i].ifname)
-                    ifname = libxl__sprintf(gc,
-                                            "tap%d.%d", domid, vifs[i].devid);
-                else
-                    ifname = vifs[i].ifname;
+                const char *ifname = libxl__device_nic_devname(gc,
+                                                domid, vifs[i].devid,
+                                                LIBXL_NIC_TYPE_IOEMU);
                 flexarray_vappend(dm_args,
                                   "-net",
                                   GCSPRINTF(
@@ -456,13 +453,9 @@ static char ** libxl__build_device_model_args_new(libxl__gc *gc,
             if (vifs[i].nictype == LIBXL_NIC_TYPE_IOEMU) {
                 char *smac = libxl__sprintf(gc,
                                 LIBXL_MAC_FMT, LIBXL_MAC_BYTES(vifs[i].mac));
-                char *ifname;
-                if (!vifs[i].ifname) {
-                    ifname = libxl__sprintf(gc, "tap%d.%d",
-                                            guest_domid, vifs[i].devid);
-                } else {
-                    ifname = vifs[i].ifname;
-                }
+                const char *ifname = libxl__device_nic_devname(gc,
+                                                guest_domid, vifs[i].devid,
+                                                LIBXL_NIC_TYPE_IOEMU);
                 flexarray_append(dm_args, "-device");
                 flexarray_append(dm_args,
                    libxl__sprintf(gc, "%s,id=nic%d,netdev=net%d,mac=%s",
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 34ea15ca86..c047253f21 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -83,6 +83,7 @@
 #define STUBDOM_CONSOLE_RESTORE 2
 #define STUBDOM_CONSOLE_SERIAL 3
 #define STUBDOM_SPECIAL_CONSOLES 3
+#define TAP_DEVICE_SUFFIX "-emu"
 
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
 
@@ -196,17 +197,6 @@ _hidden libxl__ev_xswatch *libxl__watch_slot_contents(libxl__gc *gc,
  * version of the _evdisable_FOO function; the internal one is
  * used during cleanup.
  */
-_hidden int libxl__domain_create_info_setdefault(libxl__gc *gc,
-                                        libxl_domain_create_info *c_info);
-_hidden int libxl__domain_build_info_setdefault(libxl__gc *gc,
-                                        libxl_domain_build_info *b_info);
-_hidden int libxl__device_disk_setdefault(libxl__gc *gc,
-                                          libxl_device_disk *disk);
-_hidden int libxl__device_nic_setdefault(libxl__gc *gc, libxl_device_nic *nic);
-_hidden int libxl__device_vfb_setdefault(libxl__gc *gc, libxl_device_vfb *vfb);
-_hidden int libxl__device_vkb_setdefault(libxl__gc *gc, libxl_device_vkb *vkb);
-_hidden int libxl__device_pci_setdefault(libxl__gc *gc, libxl_device_pci *pci);
-
 struct libxl__evgen_domain_death {
     uint32_t domid;
     unsigned shutdown_reported:1, death_reported:1;
@@ -705,6 +695,21 @@ _hidden int libxl__wait_for_backend(libxl__gc *gc, char *be_path, char *state);
  *     All libxl API functions are expected to have arranged for this
  *     to be called before using any values within these structures.
  */
+_hidden int libxl__domain_create_info_setdefault(libxl__gc *gc,
+                                        libxl_domain_create_info *c_info);
+_hidden int libxl__domain_build_info_setdefault(libxl__gc *gc,
+                                        libxl_domain_build_info *b_info);
+_hidden int libxl__device_disk_setdefault(libxl__gc *gc,
+                                          libxl_device_disk *disk);
+_hidden int libxl__device_nic_setdefault(libxl__gc *gc, libxl_device_nic *nic);
+_hidden int libxl__device_vfb_setdefault(libxl__gc *gc, libxl_device_vfb *vfb);
+_hidden int libxl__device_vkb_setdefault(libxl__gc *gc, libxl_device_vkb *vkb);
+_hidden int libxl__device_pci_setdefault(libxl__gc *gc, libxl_device_pci *pci);
+
+_hidden const char *libxl__device_nic_devname(libxl__gc *gc,
+                                              uint32_t domid,
+                                              uint32_t devid,
+                                              libxl_nic_type type);
 
 /* Arranges that dev will be removed from its guest.  When
  * this is done, the ao will be completed.  An error
diff --git a/tools/python/xen/xend/image.py b/tools/python/xen/xend/image.py
index f3768b4612..e08417282d 100644
--- a/tools/python/xen/xend/image.py
+++ b/tools/python/xen/xend/image.py
@@ -917,11 +917,7 @@ class HVMImageHandler(ImageHandler):
             ret.append("-net")
             ret.append("nic,vlan=%d,macaddr=%s,model=%s" %
                        (nics, mac, model))
-            vifname = devinfo.get('vifname')
-            if vifname:
-                vifname = "tap-" + vifname
-            else:
-                vifname = "tap%d.%d" % (self.vm.getDomid(), nics-1)
+            vifname = "vif%d.%d-emu" % (self.vm.getDomid(), nics-1)
             ret.append("-net")
             ret.append("tap,vlan=%d,ifname=%s,bridge=%s" %
                        (nics, vifname, bridge))