[lxc-devel] [PATCH 1/1] add c->may_control
Serge Hallyn
serge.hallyn at ubuntu.com
Sat Sep 28 02:01:07 UTC 2013
This is an api function which will return false if the container
is running, and the caller may not talk to its monitor over its
command socket. Otherwise - if the container is not running, or
the caller may access it - it returns true.
We can use this in several tools early on to prevent the segvs
etc which we currently get.
Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
---
src/lxc/commands.c | 30 ++++++++++++++++++++++++++++++
src/lxc/commands.h | 1 +
src/lxc/lxccontainer.c | 6 ++++++
src/lxc/lxccontainer.h | 6 ++++++
src/tests/Makefile.am | 6 ++++--
src/tests/may_control.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
6 files changed, 93 insertions(+), 2 deletions(-)
create mode 100644 src/tests/may_control.c
diff --git a/src/lxc/commands.c b/src/lxc/commands.c
index 7c538c6..fa6e3fb 100644
--- a/src/lxc/commands.c
+++ b/src/lxc/commands.c
@@ -291,6 +291,36 @@ out:
return ret;
}
+int lxc_try_cmd(const char *name, const char *lxcpath)
+{
+ int stopped, ret;
+ struct lxc_cmd_rr cmd = {
+ .req = { .cmd = LXC_CMD_GET_INIT_PID },
+ };
+
+ ret = lxc_cmd(name, &cmd, &stopped, lxcpath);
+
+ if (stopped)
+ return 0;
+ if (ret > 0 && cmd.rsp.ret < 0) {
+ errno = cmd.rsp.ret;
+ return -1;
+ }
+ if (ret > 0)
+ return 0;
+
+ /*
+ * At this point we weren't denied access, and the
+ * container *was* started. There was some inexplicable
+ * error in the protocol.
+ * I'm not clear on whether we should return -1 here, but
+ * we didn't receive a -EACCES, so technically it's not that
+ * we're not allowed to control the container - it's just not
+ * behaving.
+ */
+ return 0;
+}
+
/* Implentations of the commands and their callbacks */
/*
diff --git a/src/lxc/commands.h b/src/lxc/commands.h
index 2c0258c..7829aef 100644
--- a/src/lxc/commands.h
+++ b/src/lxc/commands.h
@@ -88,5 +88,6 @@ extern int lxc_cmd_init(const char *name, struct lxc_handler *handler,
const char *lxcpath);
extern int lxc_cmd_mainloop_add(const char *name, struct lxc_epoll_descr *descr,
struct lxc_handler *handler);
+extern int lxc_try_cmd(const char *name, const char *lxcpath);
#endif /* __commands_h */
diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
index 1b3f2f5..060bb70 100644
--- a/src/lxc/lxccontainer.c
+++ b/src/lxc/lxccontainer.c
@@ -2589,6 +2589,11 @@ static bool lxcapi_snapshot_restore(struct lxc_container *c, char *snapname, cha
return b;
}
+static bool lxcapi_may_control(struct lxc_container *c)
+{
+ return lxc_try_cmd(c->name, c->config_path) == 0;
+}
+
static int lxcapi_attach_run_waitl(struct lxc_container *c, lxc_attach_options_t *options, const char *program, const char *arg, ...)
{
va_list ap;
@@ -2708,6 +2713,7 @@ struct lxc_container *lxc_container_new(const char *name, const char *configpath
c->snapshot = lxcapi_snapshot;
c->snapshot_list = lxcapi_snapshot_list;
c->snapshot_restore = lxcapi_snapshot_restore;
+ c->may_control = lxcapi_may_control;
/* we'll allow the caller to update these later */
if (lxc_log_init(NULL, "none", NULL, "lxc_container", 0, c->config_path)) {
diff --git a/src/lxc/lxccontainer.h b/src/lxc/lxccontainer.h
index 225fb39..20ab8e8 100644
--- a/src/lxc/lxccontainer.h
+++ b/src/lxc/lxccontainer.h
@@ -223,6 +223,12 @@ struct lxc_container {
* Returns true on success, false on failure.
*/
bool (*snapshot_restore)(struct lxc_container *c, char *snapname, char *newname);
+
+ /*
+ * Return false if there is a control socket for the container monitor,
+ * and the caller may not access it. Return true otherwise.
+ */
+ bool (*may_control)(struct lxc_container *c);
};
struct lxc_snapshot {
diff --git a/src/tests/Makefile.am b/src/tests/Makefile.am
index 8157407..479facc 100644
--- a/src/tests/Makefile.am
+++ b/src/tests/Makefile.am
@@ -19,6 +19,7 @@ lxc_usernic_test_SOURCES = ../lxc/lxc_user_nic.c ../lxc/nl.c
lxc_usernic_test_CFLAGS = -DISTEST
lxc_test_snapshot_SOURCES = snapshot.c
lxc_test_concurrent_SOURCES = concurrent.c
+lxc_test_may_control_SOURCES = may_control.c
AM_CFLAGS=-I$(top_srcdir)/src \
-DLXCROOTFSMOUNT=\"$(LXCROOTFSMOUNT)\" \
@@ -31,7 +32,7 @@ bin_PROGRAMS = lxc-test-containertests lxc-test-locktests lxc-test-startone \
lxc-test-destroytest lxc-test-saveconfig lxc-test-createtest \
lxc-test-shutdowntest lxc-test-get_item lxc-test-getkeys lxc-test-lxcpath \
lxc-test-cgpath lxc-test-clonetest lxc-test-console lxc-usernic-test \
- lxc-test-snapshot lxc-test-concurrent
+ lxc-test-snapshot lxc-test-concurrent lxc-test-may-control
bin_SCRIPTS = lxc-test-usernic
@@ -53,4 +54,5 @@ EXTRA_DIST = \
console.c \
lxc-test-usernic \
snapshot.c \
- concurrent.c
+ concurrent.c \
+ may_control.c
diff --git a/src/tests/may_control.c b/src/tests/may_control.c
new file mode 100644
index 0000000..c176087
--- /dev/null
+++ b/src/tests/may_control.c
@@ -0,0 +1,46 @@
+/* control.c
+ *
+ * Copyright © 2013 Canonical, Inc
+ * Author: Serge Hallyn <serge.hallyn at ubuntu.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <lxc/lxccontainer.h>
+
+void usage(char *me)
+{
+ printf("Usage: %s name [lxcpath]\n", me);
+ exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+ char *lxcpath = NULL, *name;
+ bool may = false;
+ struct lxc_container *c;
+
+ if (argc < 2)
+ usage(argv[0]);
+ name = argv[1];
+ if (argc == 3)
+ lxcpath = argv[2];
+ c = lxc_container_new(name, lxcpath);
+ if (c)
+ may = c->may_control(c);
+ printf("You may%s control %s\n", may ? "" : " not", name);
+ exit(may ? 0 : 1);
+}
--
1.8.1.2
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