[PATCH v4 08/10] libxl: call hotplug scripts for disk devices from libxl

[Roger Pau Monne <roger.pau@citrix.com>]

Since most of the needed work is already done in previous patches,
this patch only contains the necessary code to call hotplug scripts
for disk devices, that should be called when the device is added or
removed from a guest.

We will chain the launch of the disk hotplug scripts after the
device_backend_callback callback, or directly from
libxl__initiate_device_{add,remove} if the device is already in the
desired state.

Changes since v2:

 * Added array size check with assert.

 * Added NetBSD code (so compilation is not broken).

 * Removed a check for null in device_hotplug_timeout_cb.

Changes since v1:

 * Moved all the event related code that was inside libxl_linux.c into
   libxl_device.c, so the flow of the device addition/removal event is
   all in the same file.

Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
---
 tools/hotplug/Linux/xen-backend.rules     |    6 +-
 tools/hotplug/Linux/xen-hotplug-common.sh |    6 ++
 tools/libxl/libxl.c                       |   10 +++
 tools/libxl/libxl_device.c                |  121 ++++++++++++++++++++++++++++-
 tools/libxl/libxl_internal.h              |   20 +++++
 tools/libxl/libxl_linux.c                 |   98 +++++++++++++++++++++++
 tools/libxl/libxl_netbsd.c                |    9 ++
 7 files changed, 266 insertions(+), 4 deletions(-)

diff --git a/tools/hotplug/Linux/xen-backend.rules b/tools/hotplug/Linux/xen-backend.rules
index 405387f..d55ff11 100644
--- a/tools/hotplug/Linux/xen-backend.rules
+++ b/tools/hotplug/Linux/xen-backend.rules
@@ -1,11 +1,11 @@
-SUBSYSTEM=="xen-backend", KERNEL=="tap*", RUN+="/etc/xen/scripts/blktap $env{ACTION}"
-SUBSYSTEM=="xen-backend", KERNEL=="vbd*", RUN+="/etc/xen/scripts/block $env{ACTION}"
+SUBSYSTEM=="xen-backend", KERNEL=="tap*", ENV{UDEV_CALL}="1", RUN+="/etc/xen/scripts/blktap $env{ACTION}"
+SUBSYSTEM=="xen-backend", KERNEL=="vbd*", ENV{UDEV_CALL}="1", RUN+="/etc/xen/scripts/block $env{ACTION}"
 SUBSYSTEM=="xen-backend", KERNEL=="vtpm*", RUN+="/etc/xen/scripts/vtpm $env{ACTION}"
 SUBSYSTEM=="xen-backend", KERNEL=="vif2-*", RUN+="/etc/xen/scripts/vif2 $env{ACTION}"
 SUBSYSTEM=="xen-backend", KERNEL=="vif-*", ACTION=="online", RUN+="/etc/xen/scripts/vif-setup online type_if=vif"
 SUBSYSTEM=="xen-backend", KERNEL=="vif-*", ACTION=="offline", RUN+="/etc/xen/scripts/vif-setup offline type_if=vif"
 SUBSYSTEM=="xen-backend", KERNEL=="vscsi*", RUN+="/etc/xen/scripts/vscsi $env{ACTION}"
-SUBSYSTEM=="xen-backend", ACTION=="remove", RUN+="/etc/xen/scripts/xen-hotplug-cleanup"
+SUBSYSTEM=="xen-backend", ACTION=="remove", ENV{UDEV_CALL}="1", RUN+="/etc/xen/scripts/xen-hotplug-cleanup"
 KERNEL=="evtchn", NAME="xen/%k"
 SUBSYSTEM=="xen", KERNEL=="blktap[0-9]*", NAME="xen/%k", MODE="0600"
 SUBSYSTEM=="blktap2", KERNEL=="blktap[0-9]*", NAME="xen/blktap-2/%k", MODE="0600"
diff --git a/tools/hotplug/Linux/xen-hotplug-common.sh b/tools/hotplug/Linux/xen-hotplug-common.sh
index 8f6557d..4a7bc73 100644
--- a/tools/hotplug/Linux/xen-hotplug-common.sh
+++ b/tools/hotplug/Linux/xen-hotplug-common.sh
@@ -15,6 +15,12 @@
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 #
 
+# Hack to prevent the execution of hotplug scripts from udev if the domain
+# has been launched from libxl
+if [ -n "${UDEV_CALL}" ] && \
+   xenstore-read "libxl/disable_udev" >/dev/null 2>&1; then
+    exit 0
+fi
 
 dir=$(dirname "$0")
 . "$dir/hotplugpath.sh"
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 2f27fd5..ccb5bdc 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -1607,6 +1607,11 @@ void libxl__device_disk_add(libxl__egc *egc, uint32_t domid,
             flexarray_append(back, "params");
             flexarray_append(back, dev);
 
+            flexarray_append(back, "script");
+            flexarray_append(back, GCSPRINTF("%s/%s",
+                                             libxl__xen_script_dir_path(),
+                                             "block"));
+
             assert(device->backend_kind == LIBXL__DEVICE_KIND_VBD);
             break;
         case LIBXL_DISK_BACKEND_TAP:
@@ -1622,6 +1627,11 @@ void libxl__device_disk_add(libxl__egc *egc, uint32_t domid,
                 libxl__device_disk_string_of_format(disk->format),
                 disk->pdev_path));
 
+            flexarray_append(back, "script");
+            flexarray_append(back, GCSPRINTF("%s/%s",
+                                             libxl__xen_script_dir_path(),
+                                             "blktap"));
+
             /* now create a phy device to export the device to the guest */
             goto do_backend_phy;
         case LIBXL_DISK_BACKEND_QDISK:
diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index 9933cc2..8e1ec0f 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -569,6 +569,14 @@ static void device_backend_callback(libxl__egc *egc, libxl__ev_devstate *ds,
 static void device_backend_cleanup(libxl__gc *gc,
                                    libxl__ao_device *aodev);
 
+static void device_hotplug(libxl__egc *egc, libxl__ao_device *aodev);
+
+static void device_hotplug_fork_cb(libxl__egc *egc, libxl__ev_child *child,
+                                   pid_t pid, int status);
+
+static void device_hotplug_timeout_cb(libxl__egc *egc, libxl__ev_time *ev,
+                                      const struct timeval *requested_abs);
+
 void libxl__initiate_device_add(libxl__egc *egc, libxl__ao_device *aodev)
 {
     STATE_AO_GC(aodev->ao);
@@ -657,7 +665,7 @@ retry_transaction:
 
  out_ok:
     if (t) xs_transaction_end(ctx->xsh, t, 0);
-    aodev->callback(egc, aodev);
+    device_hotplug(egc, aodev);
     return;
 }
 
@@ -689,6 +697,9 @@ static void device_backend_callback(libxl__egc *egc, libxl__ev_devstate *ds,
         goto out;
     }
 
+    device_hotplug(egc, aodev);
+    return;
+
 out:
     aodev->rc = rc;
     aodev->callback(egc, aodev);
@@ -701,6 +712,114 @@ static void device_backend_cleanup(libxl__gc *gc, libxl__ao_device *aodev)
     libxl__ev_devstate_cancel(gc, &aodev->ds);
 }
 
+static void device_hotplug(libxl__egc *egc, libxl__ao_device *aodev)
+{
+    STATE_AO_GC(aodev->ao);
+    char *be_path = libxl__device_backend_path(gc, aodev->dev);
+    char **args, **env;
+    int rc = 0;
+    int hotplug;
+
+    /* Check if we have to execute hotplug scripts for this device
+     * and return the necessary args/env vars for execution */
+    hotplug = libxl__get_hotplug_script_info(gc, aodev->dev, &args, &env,
+                                             aodev->action);
+    switch (hotplug) {
+    case 0:
+        /* no hotplug script to execute */
+        goto out;
+    case 1:
+        /* execute hotplug script */
+        break;
+    default:
+        /* everything else is an error */
+        LOG(ERROR, "unable to get args/env to execute hotplug script for "
+                   "device %s", libxl__device_backend_path(gc, aodev->dev));
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    /* Set hotplug timeout */
+    libxl__ev_time_init(&aodev->ev);
+    rc = libxl__ev_time_register_rel(gc, &aodev->ev, device_hotplug_timeout_cb,
+                                     LIBXL_HOTPLUG_TIMEOUT * 1000);
+    if (rc) {
+        LOG(ERROR, "unable to register timeout for hotplug device %s", be_path);
+        goto out;
+    }
+
+    aodev->what = GCSPRINTF("%s %s", args[0], args[1]);
+    LOG(DEBUG, "calling hotplug script: %s %s", args[0], args[1]);
+    libxl__ev_child_init(&aodev->child);
+
+    /* fork and execute hotplug script */
+    aodev->pid = libxl__ev_child_fork(gc, &aodev->child,
+                                      device_hotplug_fork_cb);
+    if (aodev->pid == -1) {
+        LOG(ERROR, "unable to fork");
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    if (!aodev->pid) {
+        /* child */
+        libxl__exec(gc, -1, -1, -1, args[0], args, env);
+        /* notreached */
+        abort();
+    }
+
+    if (!libxl__ev_child_inuse(&aodev->child)) {
+        /* hotplug launch failed */
+        LOG(ERROR, "unable to launch hotplug script for device %s", be_path);
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    return;
+
+out:
+    libxl__ev_time_deregister(gc, &aodev->ev);
+    aodev->rc = rc;
+    aodev->callback(egc, aodev);
+    return;
+}
+
+static void device_hotplug_fork_cb(libxl__egc *egc, libxl__ev_child *child,
+                                   pid_t pid, int status)
+{
+    libxl__ao_device *aodev = CONTAINER_OF(child, *aodev, child);
+    STATE_AO_GC(aodev->ao);
+
+    libxl__ev_time_deregister(gc, &aodev->ev);
+
+    if (status) {
+        libxl_report_child_exitstatus(CTX, aodev->rc ? LIBXL__LOG_ERROR
+                                                     : LIBXL__LOG_WARNING,
+                                      aodev->what, pid, status);
+        aodev->rc = ERROR_FAIL;
+    }
+    aodev->callback(egc, aodev);
+}
+
+static void device_hotplug_timeout_cb(libxl__egc *egc, libxl__ev_time *ev,
+                                      const struct timeval *requested_abs)
+{
+    libxl__ao_device *aodev = CONTAINER_OF(ev, *aodev, ev);
+    STATE_AO_GC(aodev->ao);
+
+    if (libxl__ev_child_inuse(&aodev->child)) {
+        if (kill(aodev->pid, SIGKILL)) {
+            LOGEV(ERROR, errno, "unable to kill hotplug script %s [%ld]",
+                                aodev->what, (unsigned long)aodev->pid);
+            goto out;
+        }
+    }
+
+out:
+    libxl__ev_time_deregister(gc, &aodev->ev);
+    return;
+}
+
 static void device_remove_callback(libxl__egc *egc, libxl__ao_device *aodev)
 {
     STATE_AO_GC(aodev->ao);
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 45b776c..da5b02b 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -72,6 +72,7 @@
 
 #define LIBXL_INIT_TIMEOUT 10
 #define LIBXL_DESTROY_TIMEOUT 10
+#define LIBXL_HOTPLUG_TIMEOUT 10
 #define LIBXL_DEVICE_MODEL_START_TIMEOUT 10
 #define LIBXL_XENCONSOLE_LIMIT 1048576
 #define LIBXL_XENCONSOLE_PROTOCOL "vt100"
@@ -1814,6 +1815,11 @@ struct libxl__ao_device {
     int rc;
     libxl__ev_devstate ds;
     void *base;
+    /* device hotplug execution */
+    pid_t pid;
+    char *what;
+    libxl__ev_time ev;
+    libxl__ev_child child;
 };
 
 /* Internal AO operation to connect a disk device */
@@ -1842,6 +1848,20 @@ _hidden void libxl__initiate_device_add(libxl__egc*, libxl__ao_device *aodev);
 _hidden void libxl__initiate_device_remove(libxl__egc *egc,
                                            libxl__ao_device *aodev);
 
+/*
+ * libxl__get_hotplug_script_info returns the args and env that should
+ * be passed to the hotplug script for the requested device.
+ *
+ * Since a device might not need to execute any hotplug script, this function
+ * can return the following values:
+ * < 0: Error
+ * 0: No need to execute hotplug script
+ * 1: Execute hotplug script
+ */
+_hidden int libxl__get_hotplug_script_info(libxl__gc *gc, libxl__device *dev,
+                                           char ***args, char ***env,
+                                           libxl__device_action action);
+
 /*----- Domain destruction -----*/
 
 /* Domain destruction has been split into two functions:
diff --git a/tools/libxl/libxl_linux.c b/tools/libxl/libxl_linux.c
index 925248b..98cd25f 100644
--- a/tools/libxl/libxl_linux.c
+++ b/tools/libxl/libxl_linux.c
@@ -25,3 +25,101 @@ int libxl__try_phy_backend(mode_t st_mode)
 
     return 1;
 }
+
+/* Hotplug scripts helpers */
+
+static char **get_hotplug_env(libxl__gc *gc, libxl__device *dev)
+{
+    char *be_path = libxl__device_backend_path(gc, dev);
+    char *script;
+    const char *type = libxl__device_kind_to_string(dev->backend_kind);
+    char **env;
+    int nr = 0, arraysize = 9;
+
+    script = libxl__xs_read(gc, XBT_NULL,
+                            GCSPRINTF("%s/%s", be_path, "script"));
+    if (!script) {
+        LOGEV(ERROR, errno, "unable to read script from %s", be_path);
+        return NULL;
+    }
+
+    GCNEW_ARRAY(env, arraysize);
+    env[nr++] = "script";
+    env[nr++] = script;
+    env[nr++] = "XENBUS_TYPE";
+    env[nr++] = libxl__strdup(gc, type);
+    env[nr++] = "XENBUS_PATH";
+    env[nr++] = GCSPRINTF("backend/%s/%u/%d", type, dev->domid, dev->devid);
+    env[nr++] = "XENBUS_BASE_PATH";
+    env[nr++] = "backend";
+    env[nr++] = NULL;
+    assert(nr == arraysize);
+
+    return env;
+}
+
+/* Hotplug scripts caller functions */
+
+static int libxl__hotplug_disk(libxl__gc *gc, libxl__device *dev,
+                               char ***args, char ***env,
+                               libxl__device_action action)
+{
+    char *be_path = libxl__device_backend_path(gc, dev);
+    char *script;
+    int nr = 0, rc = 0, arraysize = 3;
+
+    script = libxl__xs_read(gc, XBT_NULL,
+                            GCSPRINTF("%s/%s", be_path, "script"));
+    if (!script) {
+        LOGEV(ERROR, errno, "unable to read script from %s", be_path);
+        rc = ERROR_FAIL;
+        goto error;
+    }
+
+    *env = get_hotplug_env(gc, dev);
+    if (!*env) {
+        rc = ERROR_FAIL;
+        goto error;
+    }
+
+    GCNEW_ARRAY(*args, arraysize);
+    (*args)[nr++] = script;
+    (*args)[nr++] = action == DEVICE_CONNECT ? "add" : "remove";
+    (*args)[nr++] = NULL;
+    assert(nr == arraysize);
+
+    rc = 0;
+
+error:
+    return rc;
+}
+
+int libxl__get_hotplug_script_info(libxl__gc *gc, libxl__device *dev,
+                                   char ***args, char ***env,
+                                   libxl__device_action action)
+{
+    char *disable_udev = libxl__xs_read(gc, XBT_NULL, DISABLE_UDEV_PATH);
+    int rc;
+
+    /* Check if we have to run hotplug scripts */
+    if (!disable_udev) {
+        rc = 0;
+        goto out;
+    }
+
+    switch (dev->backend_kind) {
+    case LIBXL__DEVICE_KIND_VBD:
+        rc = libxl__hotplug_disk(gc, dev, args, env, action);
+        if (!rc) rc = 1;
+        break;
+    default:
+        /* If no need to execute any hotplug scripts,
+         * call the callback manually
+         */
+        rc = 0;
+        break;
+    }
+
+out:
+    return rc;
+}
diff --git a/tools/libxl/libxl_netbsd.c b/tools/libxl/libxl_netbsd.c
index 9e0ed6d..0f2cdaa 100644
--- a/tools/libxl/libxl_netbsd.c
+++ b/tools/libxl/libxl_netbsd.c
@@ -24,3 +24,12 @@ int libxl__try_phy_backend(mode_t st_mode)
 
     return 0;
 }
+
+/* Hotplug scripts caller functions */
+
+int libxl__get_hotplug_script_info(libxl__gc *gc, libxl__device *dev,
+                                   char ***args, char ***env,
+                                   libxl__device_action action)
+{
+    return 0;
+}
\ No newline at end of file
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