Introduce an LXC specific public API & library

This patch introduces support for LXC specific public APIs. In
common with what was done for QEMU, this creates a libvirt_lxc.so
library and libvirt/libvirt-lxc.h header file.

The actual APIs are

  int virDomainLxcOpenNamespace(virDomainPtr domain,
                                int **fdlist,
                                unsigned int flags);

  int virDomainLxcEnterNamespace(virDomainPtr domain,
                                 unsigned int nfdlist,
                                 int *fdlist,
                                 unsigned int *noldfdlist,
                                 int **oldfdlist,
                                 unsigned int flags);

which provide a way to use the setns() system call to move the
calling process into the container's namespace. It is not
practical to write in a generically applicable manner. The
nearest that we could get to such an API would be an API which
allows to pass a command + argv to be executed inside a
container. Even if we had such a generic API, this LXC specific
API is still useful, because it allows the caller to maintain
the current process context, in particular any I/O streams they
have open.

NB the virDomainLxcEnterNamespace() API is special in that it
runs client side, so does not involve the internal driver API.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 141 insertions, 0 deletions

diff --git a/libvirt-lxc-override.c b/libvirt-lxc-override.c
new file mode 100644
index 0000000..c80668e
--- /dev/null
+++ b/libvirt-lxc-override.c
@@ -0,0 +1,141 @@
+/*
+ * libvir.c: this modules implements the main part of the glue of the
+ *           libvir library and the Python interpreter. It provides the
+ *           entry points where an automatically generated stub is
+ *           unpractical
+ *
+ * Copyright (C) 2012-2013 Red Hat, Inc.
+ *
+ * Daniel Veillard <veillard@redhat.com>
+ */
+
+#include <config.h>
+
+/* Horrible kludge to work around even more horrible name-space pollution
+   via Python.h.  That file includes /usr/include/python2.5/pyconfig*.h,
+   which has over 180 autoconf-style HAVE_* definitions.  Shame on them.  */
+#undef HAVE_PTHREAD_H
+
+#include <Python.h>
+#include "libvirt/libvirt-lxc.h"
+#include "libvirt/virterror.h"
+#include "typewrappers.h"
+#include "libvirt-lxc.h"
+#include "viralloc.h"
+#include "virfile.h"
+
+#ifndef __CYGWIN__
+extern void initlibvirtmod_lxc(void);
+#else
+extern void initcygvirtmod_lxc(void);
+#endif
+
+#if 0
+# define DEBUG_ERROR 1
+#endif
+
+#if DEBUG_ERROR
+# define DEBUG(fmt, ...)            \
+   printf(fmt, __VA_ARGS__)
+#else
+# define DEBUG(fmt, ...)            \
+   do {} while (0)
+#endif
+
+/* The two-statement sequence "Py_INCREF(Py_None); return Py_None;"
+   is so common that we encapsulate it here.  Now, each use is simply
+   return VIR_PY_NONE;  */
+#define VIR_PY_NONE (Py_INCREF (Py_None), Py_None)
+#define VIR_PY_INT_FAIL (libvirt_intWrap(-1))
+#define VIR_PY_INT_SUCCESS (libvirt_intWrap(0))
+
+/************************************************************************
+ *									*
+ *		Statistics						*
+ *									*
+ ************************************************************************/
+
+static PyObject *
+libvirt_lxc_virDomainLxcOpenNamespace(PyObject *self ATTRIBUTE_UNUSED,
+                                      PyObject *args) {
+    PyObject *py_retval;
+    virDomainPtr domain;
+    PyObject *pyobj_domain;
+    unsigned int flags;
+    int c_retval;
+    int *fdlist = NULL;
+    int i;
+
+    if (!PyArg_ParseTuple(args, (char *)"Oi:virDomainLxcOpenNamespace",
+                          &pyobj_domain, &flags))
+        return NULL;
+    domain = (virDomainPtr) PyvirDomain_Get(pyobj_domain);
+
+    if (domain == NULL)
+        return VIR_PY_NONE;
+    LIBVIRT_BEGIN_ALLOW_THREADS;
+    c_retval = virDomainLxcOpenNamespace(domain, &fdlist, flags);
+    LIBVIRT_END_ALLOW_THREADS;
+
+    if (c_retval < 0)
+        return VIR_PY_NONE;
+
+    py_retval = PyList_New(c_retval);
+    for (i = 0 ; i < c_retval ; i++) {
+        PyObject *item = NULL;
+
+        if ((item = PyInt_FromLong(fdlist[i])) == NULL)
+            goto error;
+
+        if (PyList_Append(py_retval, item) < 0) {
+            Py_DECREF(item);
+            goto error;
+        }
+    }
+    return py_retval;
+
+error:
+    for (i = 0 ; i < c_retval ; i++) {
+        VIR_FORCE_CLOSE(fdlist[i]);
+    }
+    VIR_FREE(fdlist);
+    return VIR_PY_NONE;
+}
+/************************************************************************
+ *									*
+ *			The registration stuff				*
+ *									*
+ ************************************************************************/
+static PyMethodDef libvirtLxcMethods[] = {
+#include "libvirt-lxc-export.c"
+    {(char *) "virDomainLxcOpenNamespace", libvirt_lxc_virDomainLxcOpenNamespace, METH_VARARGS, NULL},
+    {NULL, NULL, 0, NULL}
+};
+
+void
+#ifndef __CYGWIN__
+initlibvirtmod_lxc
+#else
+initcygvirtmod_lxc
+#endif
+  (void)
+{
+    static int initialized = 0;
+
+    if (initialized != 0)
+        return;
+
+    if (virInitialize() < 0)
+        return;
+
+    /* initialize the python extension module */
+    Py_InitModule((char *)
+#ifndef __CYGWIN__
+                  "libvirtmod_lxc"
+#else
+                  "cygvirtmod_lxc"
+#endif
+                  , libvirtLxcMethods);
+
+    initialized = 1;
+}