Create --share-ipc option

doc/lxc-start.sgml.in

@@ -58,6 +58,7 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
       <arg choice="opt">-s KEY=VAL</arg>
       <arg choice="opt">-C</arg>
       <arg choice="opt">--share-net <replaceable>name|pid</replaceable></arg>
+      <arg choice="opt">--share-ipc <replaceable>name|pid</replaceable></arg>
       <arg choice="opt">command</arg>
     </cmdsynopsis>
   </refsynopsisdiv>
@@ -203,6 +204,15 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 	</listitem>
       </varlistentry>
 
+      <varlistentry>
+	<term>
+	  <option>--share-ipc <replaceable>name|pid</replaceable></option>
+	</term>
+	<listitem>
+	  <para>
+            Inherit an IPC namespace from
+	    a <replaceable>name</replaceable> container or
+	    a <replaceable>pid</replaceable>.
 	  </para>
 	</listitem>
       </varlistentry>

src/lxc/arguments.h

@@ -55,6 +55,7 @@ struct lxc_arguments {
 
 	/* for lxc-start */
 	const char *share_net;
+	const char *share_ipc;
 
 	/* for lxc-checkpoint/restart */
 	const char *statefile;

src/lxc/lxc_start.c

@@ -52,6 +52,7 @@
 #include "arguments.h"
 
 #define OPT_SHARE_NET OPT_USAGE+1
+#define OPT_SHARE_IPC OPT_USAGE+2
 
 lxc_log_define(lxc_start_ui, lxc_start);
 
@@ -146,6 +147,7 @@ static int my_parser(struct lxc_arguments* args, int c, char* arg)
 	case 's': return lxc_config_define_add(&defines, arg);
 	case 'p': args->pidfile = arg; break;
 	case OPT_SHARE_NET: args->share_net = arg; break;
+	case OPT_SHARE_IPC: args->share_ipc = arg; break;
 	}
 	return 0;
 }
@@ -159,6 +161,7 @@ static const struct option my_longopts[] = {
 	{"close-all-fds", no_argument, 0, 'C'},
 	{"pidfile", required_argument, 0, 'p'},
 	{"share-net", required_argument, 0, OPT_SHARE_NET},
+	{"share-ipc", required_argument, 0, OPT_SHARE_IPC},
 	LXC_COMMON_OPTIONS
 };
 
@@ -181,6 +184,7 @@ Options :\n\
 		         Note: --daemon implies --close-all-fds\n\
   -s, --define KEY=VAL   Assign VAL to configuration variable KEY\n\
       --share-net=NAME   Share a network namespace with another container or pid\n\
+      --share-ipc=NAME   Share an IPC namespace with another container or pid\n\
 ",
 	.options   = my_longopts,
 	.parser    = my_parser,
@@ -308,6 +312,17 @@ int main(int argc, char *argv[])
 		conf->inherit_ns_fd[LXC_NS_NET] = fd;
 	}
 
+	if (my_args.share_ipc != NULL) {
+		int pid = pid_from_lxcname(my_args.share_ipc, lxcpath);
+		if (pid < 1)
+			goto out;
+
+		int fd = open_ns(pid, "ipc");
+		if (fd < 0)
+			goto out;
+		conf->inherit_ns_fd[LXC_NS_IPC] = fd;
+	}
+
 	if (my_args.daemonize) {
 		c->want_daemonize(c);
 	}

src/lxc/start.c

@@ -727,7 +727,7 @@ int lxc_spawn(struct lxc_handler *handler)
 	if (lxc_sync_init(handler))
 		return -1;
 
-	handler->clone_flags = CLONE_NEWUTS|CLONE_NEWPID|CLONE_NEWIPC|CLONE_NEWNS;
+	handler->clone_flags = CLONE_NEWUTS|CLONE_NEWPID|CLONE_NEWNS;
 	if (!lxc_list_empty(&handler->conf->id_map)) {
 		INFO("Cloning a new user namespace");
 		handler->clone_flags |= CLONE_NEWUSER;
@@ -766,6 +766,12 @@ int lxc_spawn(struct lxc_handler *handler)
 		INFO("Inheriting a net namespace");
 	}
 
+	if (handler->conf->inherit_ns_fd[LXC_NS_IPC] == -1) {
+		handler->clone_flags |= CLONE_NEWIPC;
+	} else {
+		INFO("Inheriting an IPC namespace");
+	}
+
 
 	cgroup_meta = lxc_cgroup_load_meta();
 	if (!cgroup_meta) {