add c->may_control

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@ubuntu.com>
Acked-by: Dwight Engen <dwight.engen@oracle.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>

diff --git a/src/lxc/commands.c b/src/lxc/commands.c
index 7c538c6d5c8b22f79bf0f8e127bbe6cf49072cce..fa6e3fb495804716124bbec997981665b6e6c93b 100644 (file)
--- 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 2c0258ca5a046f3cafc6eeb9c1cda3f05bf6ae70..7829aef22a0962345adcb9d589bd398287ed888c 100644 (file)
--- 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 3a2ae92a42251189811d5c3508b361d9c37313d6..02126b22f3702995abc2fd4017d0d800e3dc1b6e 100644 (file)
--- a/src/lxc/lxccontainer.c
+++ b/src/lxc/lxccontainer.c
@@ -2592,6 +2592,11 @@ 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;
@@ -2711,6 +2716,7 @@ 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 225fb3995b63beb41f6ae0d44f53f3c49447c89a..20ab8e870e357389abaee8e9eebbcb66eba4cf91 100644 (file)
--- 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 815740746afa9479d752657e8dbc2c4c0f4cf1a2..479faccdf8334319b2ffebb95ee2017d1a863788 100644 (file)
--- 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 (file)
index 0000000..bb0178e
--- /dev/null
+++ b/src/tests/may_control.c
@@ -0,0 +1,46 @@
+/* control.c
+ *
+ * Copyright © 2013 Canonical, Inc
+ * Author: Serge Hallyn <serge.hallyn@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);
+}