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[Libguestfs] [PATCH 6/8 v2 DISCUSSION ONLY] Add guestfs_add_domain 'live' flag.



-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming blog: http://rwmj.wordpress.com
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>From 59d06155bf48f6656e5bc75dba99fc2b34515919 Mon Sep 17 00:00:00 2001
From: Richard W.M. Jones <rjones redhat com>
Date: Fri, 28 Jan 2011 13:19:52 +0000
Subject: [PATCH 6/8] Add guestfs_add_domain 'live' flag.

This optional flag controls whether this API call will try to connect
to a running virtual machine 'guestfsd' process.

If the flag is given and the virtual machine is running, then the
libvirt XML is parsed looking for a suitable <channel> element, and
'guestfs_set_attach_method' is called with the corresponding
virtio-serial socket path.
---
 fish/fish.c                    |    2 +-
 generator/generator_actions.ml |   18 +++-
 src/virt.c                     |  192 ++++++++++++++++++++++++++++++++++-----
 3 files changed, 183 insertions(+), 29 deletions(-)

diff --git a/fish/fish.c b/fish/fish.c
index 10f645f..eb7c8fe 100644
--- a/fish/fish.c
+++ b/fish/fish.c
@@ -1,5 +1,5 @@
 /* guestfish - the filesystem interactive shell
- * Copyright (C) 2009-2010 Red Hat Inc.
+ * Copyright (C) 2009-2011 Red Hat Inc.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
diff --git a/generator/generator_actions.ml b/generator/generator_actions.ml
index a2e7467..192df77 100644
--- a/generator/generator_actions.ml
+++ b/generator/generator_actions.ml
@@ -1074,7 +1074,7 @@ Please read L<guestfs(3)/INSPECTION> for more details.");
 This returns the internal QEMU command line.  'debug' commands are
 not part of the formal API and can be removed or changed at any time.");
 
-  ("add_domain", (RInt "nrdisks", [String "dom"], [String "libvirturi"; Bool "readonly"; String "iface"]), -1, [FishAlias "domain"],
+  ("add_domain", (RInt "nrdisks", [String "dom"], [String "libvirturi"; Bool "readonly"; String "iface"; Bool "live"]), -1, [FishAlias "domain"],
    [],
    "add the disk(s) from a named libvirt domain",
    "\
@@ -1101,12 +1101,18 @@ we connect to the default libvirt URI (or one set through an
 environment variable, see the libvirt documentation for full
 details).
 
+The optional C<live> flag controls whether this call will try
+to connect to a running virtual machine C<guestfsd> process if
+it sees a suitable E<lt>channelE<gt> element in the libvirt
+XML definition.  The default (if the flag is omitted) is never
+to try.
+
 The other optional parameters are passed directly through to
 C<guestfs_add_drive_opts>.");
 
 (*
 This interface is not quite baked yet. -- RWMJ 2010-11-11
-  ("add_libvirt_dom", (RInt "nrdisks", [Pointer ("virDomainPtr", "dom")], [Bool "readonly"; String "iface"]), -1, [NotInFish],
+  ("add_libvirt_dom", (RInt "nrdisks", [Pointer ("virDomainPtr", "dom")], [Bool "readonly"; String "iface"; Bool "live"]), -1, [NotInFish],
    [],
    "add the disk(s) from a libvirt domain",
    "\
@@ -1129,7 +1135,13 @@ from a remote libvirt connection (see L<http://libvirt.org/remote.html>)
 will fail unless those disks are accessible via the same device path
 locally too.
 
-The optional parameters are passed directly through to
+The optional C<live> flag controls whether this call will try
+to connect to a running virtual machine C<guestfsd> process if
+it sees a suitable E<lt>channelE<gt> element in the libvirt
+XML definition.  The default (if the flag is omitted) is never
+to try.
+
+The other optional parameters are passed directly through to
 C<guestfs_add_drive_opts>.");
 *)
 
diff --git a/src/virt.c b/src/virt.c
index 9f84908..4b66cc8 100644
--- a/src/virt.c
+++ b/src/virt.c
@@ -59,6 +59,8 @@ struct guestfs___add_libvirt_dom_argv {
   int readonly;
 #define GUESTFS___ADD_LIBVIRT_DOM_IFACE_BITMASK (UINT64_C(1)<<1)
   const char *iface;
+#define GUESTFS___ADD_LIBVIRT_DOM_LIVE_BITMASK (UINT64_C(1)<<2)
+  int live;
 };
 
 static int guestfs___add_libvirt_dom (guestfs_h *g, virDomainPtr dom, const struct guestfs___add_libvirt_dom_argv *optargs);
@@ -73,6 +75,7 @@ guestfs__add_domain (guestfs_h *g, const char *domain_name,
   int r = -1;
   const char *libvirturi;
   int readonly;
+  int live;
   const char *iface;
   struct guestfs___add_libvirt_dom_argv optargs2 = { .bitmask = 0 };
 
@@ -82,6 +85,13 @@ guestfs__add_domain (guestfs_h *g, const char *domain_name,
              ? optargs->readonly : 0;
   iface = optargs->bitmask & GUESTFS_ADD_DOMAIN_IFACE_BITMASK
           ? optargs->iface : NULL;
+  live = optargs->bitmask & GUESTFS_ADD_DOMAIN_LIVE_BITMASK
+         ? optargs->live : 0;
+
+  if (live && readonly) {
+    error (g, _("you cannot set both live and readonly flags"));
+    return -1;
+  }
 
   /* Connect to libvirt, find the domain. */
   conn = virConnectOpenReadOnly (libvirturi);
@@ -108,6 +118,10 @@ guestfs__add_domain (guestfs_h *g, const char *domain_name,
     optargs2.bitmask |= GUESTFS___ADD_LIBVIRT_DOM_IFACE_BITMASK;
     optargs2.iface = iface;
   }
+  if (live) {
+    optargs2.bitmask |= GUESTFS___ADD_LIBVIRT_DOM_LIVE_BITMASK;
+    optargs2.live = live;
+  }
 
   r = guestfs___add_libvirt_dom (g, dom, &optargs2);
 
@@ -282,49 +296,63 @@ guestfs___for_each_disk (guestfs_h *g,
   return r;
 }
 
-static int
-add_disk (guestfs_h *g, const char *filename, const char *format,
-          void *optargs_vp)
-{
-  struct guestfs_add_drive_opts_argv *optargs = optargs_vp;
-
-  if (format) {
-    optargs->bitmask |= GUESTFS_ADD_DRIVE_OPTS_FORMAT_BITMASK;
-    optargs->format = format;
-  } else
-    optargs->bitmask &= ~GUESTFS_ADD_DRIVE_OPTS_FORMAT_BITMASK;
+/* This was proposed as an external API, but it's not quite baked yet. */
 
-  return guestfs__add_drive_opts (g, filename, optargs);
-}
+static int add_disk (guestfs_h *g, const char *filename, const char *format, void *optargs_vp);
+static int connect_live (guestfs_h *g, virDomainPtr dom);
 
-/* This was proposed as an external API, but it's not quite baked yet. */
 static int
 guestfs___add_libvirt_dom (guestfs_h *g, virDomainPtr dom,
                            const struct guestfs___add_libvirt_dom_argv *optargs)
 {
-  int r = -1;
-  virErrorPtr err;
   int cmdline_pos;
+  int r;
+  int readonly;
+  const char *iface;
+  int live;
 
-  cmdline_pos = guestfs___checkpoint_cmdline (g);
-
-  int readonly =
+  readonly =
     optargs->bitmask & GUESTFS___ADD_LIBVIRT_DOM_READONLY_BITMASK
     ? optargs->readonly : 0;
-  const char *iface =
+  iface =
     optargs->bitmask & GUESTFS___ADD_LIBVIRT_DOM_IFACE_BITMASK
     ? optargs->iface : NULL;
+  live =
+    optargs->bitmask & GUESTFS___ADD_LIBVIRT_DOM_LIVE_BITMASK
+    ? optargs->live : 0;
+
+  if (live && readonly) {
+    error (g, _("you cannot set both live and readonly flags"));
+    return -1;
+  }
 
   if (!readonly) {
     virDomainInfo info;
+    virErrorPtr err;
+    int vm_running;
+
     if (virDomainGetInfo (dom, &info) == -1) {
       err = virGetLastError ();
       error (g, _("error getting domain info: %s"), err->message);
-      goto cleanup;
+      return -1;
     }
-    if (info.state != VIR_DOMAIN_SHUTOFF) {
-      error (g, _("error: domain is a live virtual machine.\nYou must use readonly access because write access to a running virtual machine\ncan cause disk corruption."));
-      goto cleanup;
+    vm_running = info.state != VIR_DOMAIN_SHUTOFF;
+
+    if (vm_running) {
+      /* If the caller specified the 'live' flag, then they want us to
+       * try to connect to guestfsd if the domain is running.  Note
+       * that live readonly connections are not possible.
+       */
+      if (live)
+        return connect_live (g, dom);
+
+      /* Dangerous to modify the disks of a running VM. */
+      error (g, _("error: domain is a live virtual machine.\n"
+                  "Writing to the disks of a running virtual machine can cause disk corruption.\n"
+                  "Either use read-only access, or if the guest is running the guestfsd daemon\n"
+                  "specify live access.  In most libguestfs tools these options are --ro or\n"
+                  "--live respectively.  Consult the documentation for further information."));
+      return -1;
     }
   }
 
@@ -339,10 +367,124 @@ guestfs___add_libvirt_dom (guestfs_h *g, virDomainPtr dom,
     optargs2.iface = iface;
   }
 
+  /* Checkpoint the command line around the operation so that either
+   * all disks are added or none are added.
+   */
+  cmdline_pos = guestfs___checkpoint_cmdline (g);
   r = guestfs___for_each_disk (g, dom, add_disk, &optargs2);
+  if (r == -1)
+    guestfs___rollback_cmdline (g, cmdline_pos);
+
+  return r;
+}
+
+static int
+add_disk (guestfs_h *g, const char *filename, const char *format,
+          void *optargs_vp)
+{
+  struct guestfs_add_drive_opts_argv *optargs = optargs_vp;
+
+  if (format) {
+    optargs->bitmask |= GUESTFS_ADD_DRIVE_OPTS_FORMAT_BITMASK;
+    optargs->format = format;
+  } else
+    optargs->bitmask &= ~GUESTFS_ADD_DRIVE_OPTS_FORMAT_BITMASK;
+
+  return guestfs__add_drive_opts (g, filename, optargs);
+}
+
+static int
+connect_live (guestfs_h *g, virDomainPtr dom)
+{
+  int i, r = -1;
+  virErrorPtr err;
+  xmlDocPtr doc = NULL;
+  xmlXPathContextPtr xpathCtx = NULL;
+  xmlXPathObjectPtr xpathObj = NULL;
+  char *xml = NULL;
+  char *path = NULL;
+  char *attach_method = NULL;
+
+  /* Domain XML. */
+  xml = virDomainGetXMLDesc (dom, 0);
+
+  if (!xml) {
+    err = virGetLastError ();
+    error (g, _("error reading libvirt XML information: %s"),
+           err->message);
+    goto cleanup;
+  }
+
+  /* Parse XML to document. */
+  doc = xmlParseMemory (xml, strlen (xml));
+  if (doc == NULL) {
+    error (g, _("unable to parse XML information returned by libvirt"));
+    goto cleanup;
+  }
+
+  xpathCtx = xmlXPathNewContext (doc);
+  if (xpathCtx == NULL) {
+    error (g, _("unable to create new XPath context"));
+    goto cleanup;
+  }
+
+  /* This gives us a set of all the <channel> nodes related to the
+   * guestfsd virtio-serial channel.
+   */
+  xpathObj = xmlXPathEvalExpression (BAD_CAST
+      "//devices/channel[ type=\"unix\" and "
+                        "./source/@mode=\"bind\" and "
+                        "./source/@path and "
+                        "./target/@type=\"virtio\" and "
+                        "./target/@name=\"org.libguestfs.channel.0\"]",
+                                     xpathCtx);
+  if (xpathObj == NULL) {
+    error (g, _("unable to evaluate XPath expression"));
+    goto cleanup;
+  }
+
+  xmlNodeSetPtr nodes = xpathObj->nodesetval;
+  for (i = 0; i < nodes->nodeNr; ++i) {
+    xmlXPathObjectPtr xppath;
+
+    /* See note in function above. */
+    xpathCtx->node = nodes->nodeTab[i];
+
+    /* The path is in <source path=..> attribute. */
+    xppath = xmlXPathEvalExpression (BAD_CAST "./source/@path", xpathCtx);
+    if (xppath == NULL ||
+        xppath->nodesetval == NULL ||
+        xppath->nodesetval->nodeNr == 0) {
+      xmlXPathFreeObject (xppath);
+      continue;                 /* no type attribute, skip it */
+    }
+    assert (xppath->nodesetval->nodeTab[0]);
+    assert (xppath->nodesetval->nodeTab[0]->type == XML_ATTRIBUTE_NODE);
+    xmlAttrPtr attr = (xmlAttrPtr) xppath->nodesetval->nodeTab[0];
+    path = (char *) xmlNodeListGetString (doc, attr->children, 1);
+    xmlXPathFreeObject (xppath);
+    break;
+  }
+
+  if (path == NULL) {
+    error (g, _("this guest has no libvirt <channel> definition for guestfsd"));
+    goto cleanup;
+  }
+
+  /* Got a path. */
+  attach_method = safe_malloc (g, strlen (path) + 5 + 1);
+  strcpy (attach_method, "unix:");
+  strcat (attach_method, path);
+  r = guestfs_set_attach_method (g, attach_method);
 
  cleanup:
-  if (r == -1) guestfs___rollback_cmdline (g, cmdline_pos);
+  free (path);
+  free (attach_method);
+  free (xml);
+  if (xpathObj) xmlXPathFreeObject (xpathObj);
+  if (xpathCtx) xmlXPathFreeContext (xpathCtx);
+  if (doc) xmlFreeDoc (doc);
+
   return r;
 }
 
-- 
1.7.3.5


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