[PATCH] New XS_SET_TARGET

[Samuel Thibault <samuel.thibault@eu.citrix.com>]

New XS_SET_TARGET
Stubdomains (and probably other domain disagregation elements too) need
to be able to tinker with another domain.  This adds XS_SET_TARGET so
that XenStore allows domains to have permissions on files on which the
"target" has permissions.  This also adds xs_set_target, called by the
domain builder when the 'target' option is used in the configuration.

Signed-off-by: Samuel Thibault <samuel.thibault@eu.citrix.com>

---
This patch depends on the previous "New XEN_DOMCTL_set_target and
IS_PRIV_FOR" patch.

diff -u b/tools/python/xen/xend/XendDomainInfo.py b/tools/python/xen/xend/XendDomainInfo.py
--- b/tools/python/xen/xend/XendDomainInfo.py	Wed Jan 23 11:36:15 2008 +0000
+++ b/tools/python/xen/xend/XendDomainInfo.py	Wed Jan 23 11:36:15 2008 +0000
@@ -47,7 +47,7 @@
 from xen.xend.XendDevices import XendDevices
 from xen.xend.XendTask import XendTask
 from xen.xend.xenstore.xstransact import xstransact, complete
-from xen.xend.xenstore.xsutil import GetDomainPath, IntroduceDomain, ResumeDomain
+from xen.xend.xenstore.xsutil import GetDomainPath, IntroduceDomain, SetTarget, ResumeDomain
 from xen.xend.xenstore.xswatch import xswatch
 from xen.xend.XendConstants import *
 from xen.xend.XendAPIConstants import *
@@ -883,6 +883,9 @@
     def storeVm(self, *args):
         return xstransact.Store(self.vmpath, *args)
 
+    def permissionsVm(self, *args):
+        return xstransact.SetPermissions(self.vmpath, *args)
+
 
     def _readVmTxn(self, transaction,  *args):
         paths = map(lambda x: self.vmpath + "/" + x, args)
@@ -905,4 +908,8 @@
         return transaction.store(*paths)
 
+    def permissionsVmTxn(self, transaction,  *args):
+        paths = map(lambda x: self.vmpath + "/" + x, args)
+        return transaction.set_permissions(*paths)
+
     #
     # Function to update xenstore /dom/*
@@ -1694,0 +1702,9 @@
+    def _setTarget(self, target):
+        assert self.domid is not None
+
+        try:
+            SetTarget(self.domid, target)
+            self.storeDom('target', target)
+        except RuntimeError, exn:
+            raise XendError(str(exn))
+
@@ -1756,6 +1772,8 @@
                 self.native_protocol = channel_details['native_protocol'];
 
             self._introduceDomain()
+            if self.info.target():
+                self._setTarget(self.info.target())
 
             self._createDevices()
 
--- a/tools/python/xen/lowlevel/xs/xs.c	Wed Jan 23 11:21:35 2008 +0000
+++ b/tools/python/xen/lowlevel/xs/xs.c	Wed Jan 23 11:36:15 2008 +0000
@@ -619,6 +619,36 @@
     return none(result);
 }
 
+#define xspy_set_target_doc "\n"					\
+        "Tell xenstore that a domain is targetting another one so it\n" \
+        "should let it tinker with it.\n"	                        \
+	" dom    [int]   : domain id\n"					\
+	" target [int]   : domain id of the target\n"			\
+	"\n"								\
+	"Returns None on success.\n"					\
+	"Raises xen.lowlevel.xs.Error on error.\n"			\
+	"\n"
+
+static PyObject *xspy_set_target(XsHandle *self, PyObject *args)
+{
+    uint32_t dom;
+    uint32_t target;
+
+    struct xs_handle *xh = xshandle(self);
+    bool result = 0;
+
+    if (!xh)
+        return NULL;
+    if (!PyArg_ParseTuple(args, "ii", &dom, &target))
+        return NULL;
+
+    Py_BEGIN_ALLOW_THREADS
+    result = xs_set_target(xh, dom, target);
+    Py_END_ALLOW_THREADS
+
+    return none(result);
+}
+
 #define xspy_resume_domain_doc "\n"                                \
 	"Tell xenstore to clear its shutdown flag for a domain.\n" \
 	"This ensures that a subsequent shutdown will fire the\n"  \
@@ -817,6 +847,7 @@
     XSPY_METH(transaction_start, METH_NOARGS),
     XSPY_METH(transaction_end,   METH_VARARGS | METH_KEYWORDS),
     XSPY_METH(introduce_domain,  METH_VARARGS),
+    XSPY_METH(set_target,        METH_VARARGS),
     XSPY_METH(resume_domain,     METH_VARARGS),
     XSPY_METH(release_domain,    METH_VARARGS),
     XSPY_METH(close,             METH_NOARGS),
--- a/tools/python/xen/xend/image.py	Wed Jan 23 11:21:35 2008 +0000
+++ b/tools/python/xen/xend/image.py	Wed Jan 23 11:36:15 2008 +0000
@@ -222,6 +222,7 @@
             vncopts = ""
             if passwd:
                 self.vm.storeVm("vncpasswd", passwd)
+                self.vm.permissionsVm("vncpasswd", { 'dom': self.vm.getDomid(), 'read': True } )
                 vncopts = vncopts + ",password"
                 log.debug("Stored a VNC password for vfb access")
             else:
@@ -280,6 +281,9 @@
             env['XAUTHORITY'] = self.xauthority
         if self.vncconsole:
             args = args + ([ "-vncviewer" ])
+        xstransact.Mkdir("/local/domain/0/device-model/%i" % self.vm.getDomid())
+        xstransact.SetPermissions("/local/domain/0/device-model/%i" % self.vm.getDomid(),
+                        { 'dom': self.vm.getDomid(), 'read': True, 'write': True })
         log.info("spawning device models: %s %s", self.device_model, args)
         # keep track of pid and spawned options to kill it later
         self.pid = os.spawnve(os.P_NOWAIT, self.device_model, args, env)
@@ -422,7 +426,9 @@
         self.vm.storeVm(("image/dmargs", " ".join(self.dmargs)),
                         ("image/device-model", self.device_model),
                         ("image/display", self.display))
+        self.vm.permissionsVm("image/dmargs", { 'dom': self.vm.getDomid(), 'read': True } )
         self.vm.storeVm(("rtc/timeoffset", rtc_timeoffset))
+        self.vm.permissionsVm("rtc/timeoffset", { 'dom': self.vm.getDomid(), 'read': True } )
 
         self.apic = int(vmConfig['platform'].get('apic', 0))
         self.acpi = int(vmConfig['platform'].get('acpi', 0))
only in patch2:
--- a/tools/python/xen/xend/xenstore/xsutil.py	Wed Jan 23 11:21:35 2008 +0000
+++ b/tools/python/xen/xend/xenstore/xsutil.py	Wed Jan 23 11:36:15 2008 +0000
@@ -22,6 +22,9 @@
 def IntroduceDomain(domid, page, port):
     return xshandle().introduce_domain(domid, page, port)
 
+def SetTarget(domid, target):
+    return xshandle().set_target(domid, target)
+
 def GetDomainPath(domid):
     return xshandle().get_domain_path(domid)
 
--- a/tools/xenstore/xenstored_core.c	Wed Jan 23 11:21:35 2008 +0000
+++ b/tools/xenstore/xenstored_core.c	Wed Jan 23 11:36:15 2008 +0000
@@ -119,6 +119,7 @@
 	case XS_ERROR: return "ERROR";
 	case XS_IS_DOMAIN_INTRODUCED: return "XS_IS_DOMAIN_INTRODUCED";
 	case XS_RESUME: return "RESUME";
+	case XS_SET_TARGET: return "SET_TARGET";
 	default:
 		return "**UNKNOWN**";
 	}
@@ -283,6 +284,8 @@
 				break;
 		close(conn->fd);
 	}
+        if (conn->target)
+                talloc_unlink(conn, conn->target);
 	list_del(&conn->list);
 	trace_destroy(conn, "connection");
 	return 0;
@@ -472,11 +475,13 @@
 		mask &= ~XS_PERM_WRITE;
 
 	/* Owners and tools get it all... */
-	if (!conn->id || perms[0].id == conn->id)
+	if (!conn->id || perms[0].id == conn->id
+                || (conn->target && perms[0].id == conn->target->id))
 		return (XS_PERM_READ|XS_PERM_WRITE|XS_PERM_OWNER) & mask;
 
 	for (i = 1; i < num; i++)
-		if (perms[i].id == conn->id)
+		if (perms[i].id == conn->id
+                        || (conn->target && perms[i].id == conn->target->id))
 			return perms[i].perms & mask;
 
 	return perms[0].perms & mask;
@@ -1245,6 +1250,10 @@
 		do_resume(conn, onearg(in));
 		break;
 
+	case XS_SET_TARGET:
+		do_set_target(conn, in);
+		break;
+
 	default:
 		eprintf("Client unknown operation %i", in->hdr.msg.type);
 		send_error(conn, ENOSYS);
--- a/tools/xenstore/xenstored_core.h	Wed Jan 23 11:21:35 2008 +0000
+++ b/tools/xenstore/xenstored_core.h	Wed Jan 23 11:36:15 2008 +0000
@@ -84,6 +84,9 @@
 	/* The domain I'm associated with, if any. */
 	struct domain *domain;
 
+        /* The target of the domain I'm associated with. */
+        struct connection *target;
+
 	/* My watches. */
 	struct list_head watches;
 
--- a/tools/xenstore/xenstored_domain.c	Wed Jan 23 11:21:35 2008 +0000
+++ b/tools/xenstore/xenstored_domain.c	Wed Jan 23 11:36:15 2008 +0000
@@ -379,6 +379,51 @@
 	domain_conn_reset(domain);
 
 	send_ack(conn, XS_INTRODUCE);
+}
+
+void do_set_target(struct connection *conn, struct buffered_data *in)
+{
+	char *vec[2];
+	unsigned int domid, tdomid;
+        struct domain *domain, *tdomain;
+	if (get_strings(in, vec, ARRAY_SIZE(vec)) < ARRAY_SIZE(vec)) {
+		send_error(conn, EINVAL);
+		return;
+	}
+
+	if (conn->id != 0 || !conn->can_write) {
+		send_error(conn, EACCES);
+		return;
+	}
+
+	domid = atoi(vec[0]);
+	tdomid = atoi(vec[1]);
+
+        domain = find_domain_by_domid(domid);
+	if (!domain) {
+		send_error(conn, ENOENT);
+		return;
+	}
+        if (!domain->conn) {
+		send_error(conn, EINVAL);
+		return;
+	}
+
+        tdomain = find_domain_by_domid(tdomid);
+	if (!tdomain) {
+		send_error(conn, ENOENT);
+		return;
+	}
+
+        if (!tdomain->conn) {
+		send_error(conn, EINVAL);
+		return;
+	}
+
+        talloc_reference(domain->conn, tdomain->conn);
+        domain->conn->target = tdomain->conn;
+
+	send_ack(conn, XS_SET_TARGET);
 }
 
 /* domid */
--- a/tools/xenstore/xenstored_domain.h	Wed Jan 23 11:21:35 2008 +0000
+++ b/tools/xenstore/xenstored_domain.h	Wed Jan 23 11:36:15 2008 +0000
@@ -34,6 +34,9 @@
 /* domid */
 void do_resume(struct connection *conn, const char *domid_str);
 
+/* domid, target */
+void do_set_target(struct connection *conn, struct buffered_data *in);
+
 /* domid */
 void do_get_domain_path(struct connection *conn, const char *domid_str);
 
--- a/tools/xenstore/xs.c	Wed Jan 23 11:21:35 2008 +0000
+++ b/tools/xenstore/xs.c	Wed Jan 23 11:36:15 2008 +0000
@@ -708,6 +708,25 @@
 				ARRAY_SIZE(iov), NULL));
 }
 
+bool xs_set_target(struct xs_handle *h,
+			 unsigned int domid, unsigned int target)
+{
+	char domid_str[MAX_STRLEN(domid)];
+	char target_str[MAX_STRLEN(target)];
+	struct iovec iov[2];
+
+	snprintf(domid_str, sizeof(domid_str), "%u", domid);
+	snprintf(target_str, sizeof(target_str), "%u", target);
+
+	iov[0].iov_base = domid_str;
+	iov[0].iov_len = strlen(domid_str) + 1;
+	iov[1].iov_base = target_str;
+	iov[1].iov_len = strlen(target_str) + 1;
+
+	return xs_bool(xs_talkv(h, XBT_NULL, XS_SET_TARGET, iov,
+				ARRAY_SIZE(iov), NULL));
+}
+
 static void * single_with_domid(struct xs_handle *h,
 				enum xsd_sockmsg_type type,
 				unsigned int domid)
--- a/tools/xenstore/xs.h	Wed Jan 23 11:21:35 2008 +0000
+++ b/tools/xenstore/xs.h	Wed Jan 23 11:36:15 2008 +0000
@@ -132,6 +132,15 @@
 			 unsigned int domid,
 			 unsigned long mfn,
                          unsigned int eventchn); 
+
+/* Set the target of a domain
+ * This tells the store daemon that a domain is targetting another one, so
+ * it should let it tinker with it.
+ */
+bool xs_set_target(struct xs_handle *h,
+		   unsigned int domid,
+		   unsigned int target);
+
 /* Resume a domain.
  * Clear the shutdown flag for this domain in the store.
  */
--- a/xen/include/public/io/xs_wire.h	Wed Jan 23 11:21:35 2008 +0000
+++ b/xen/include/public/io/xs_wire.h	Wed Jan 23 11:36:15 2008 +0000
@@ -46,7 +46,8 @@
     XS_WATCH_EVENT,
     XS_ERROR,
     XS_IS_DOMAIN_INTRODUCED,
-    XS_RESUME
+    XS_RESUME,
+    XS_SET_TARGET
 };
 
 #define XS_WRITE_NONE "NONE"