confile: add lxc.hook.version

Unblocks #2013.
Unblocks #2015.
Closes #1766.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

doc/lxc.container.conf.sgml.in

@@ -1636,9 +1636,10 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
         at various times in a container's lifetime.
       </para>
       <para>
-        When a container hook is executed, information is passed both
+        When a container hook is executed, additional information is passed
-        as command line arguments and through environment variables.
+        along. The <option>lxc.hook.version</option> argument can be used to
-        The arguments are:
+        determine if the following arguments are passed as command line
+        arguments or through environment variables. The arguments are:
         <itemizedlist>
           <listitem><para> Container name. </para></listitem>
           <listitem><para> Section (always 'lxc'). </para></listitem>
@@ -1652,13 +1653,28 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
         </itemizedlist>
         The following environment variables are set:
         <itemizedlist>
+          <listitem><para> LXC_CGNS_AWARE: indicator whether the container is
+          cgroup namespace aware. </para></listitem>
+          <listitem><para> LXC_CONFIG_FILE: the path to the container
+          configuration file. </para></listitem>
+          <listitem><para> LXC_HOOK_TYPE: the hook type (e.g. 'clone', 'mount',
+          'pre-mount'). Note that the existence of this environment variable is
+          conditional on the value of <option>lxc.hook.version</option>. If it
+          is set to 1 then LXC_HOOK_TYPE will be set.
+          </para></listitem>
+          <listitem><para> LXC_HOOK_SECTION: the section type (e.g. 'lxc',
+          'net'). Note that the existence of this environment variable is
+          conditional on the value of <option>lxc.hook.version</option>. If it
+          is set to 1 then LXC_HOOK_SECTION will be set.
+          </para></listitem>
+          <listitem><para> LXC_LOG_LEVEL: the container's log level. </para></listitem>
           <listitem><para> LXC_NAME: is the container's name. </para></listitem>
           <listitem><para> LXC_ROOTFS_MOUNT: the path to the mounted root filesystem. </para></listitem>
-          <listitem><para> LXC_CONFIG_FILE: the path to the container configuration file. </para></listitem>
+          <listitem><para> LXC_ROOTFS_PATH: this is the lxc.rootfs.path entry
-          <listitem><para> LXC_SRC_NAME: in the case of the clone hook, this is the original container's name. </para></listitem>
+          for the container. Note this is likely not where the mounted rootfs is
-          <listitem><para> LXC_ROOTFS_PATH: this is the lxc.rootfs.path entry for the container.  Note this is likely not where the mounted rootfs is to be found, use LXC_ROOTFS_MOUNT for that. </para></listitem>
+          to be found, use LXC_ROOTFS_MOUNT for that. </para></listitem>
-          <listitem><para> LXC_CGNS_AWARE: indicated whether the container is cgroup namespace aware.  </para></listitem>
+          <listitem><para> LXC_SRC_NAME: in the case of the clone hook, this is
-          <listitem><para> LXC_LOG_LEVEL: the container's log level.  </para></listitem>
+          the original container's name. </para></listitem>
         </itemizedlist>
       </para>
       <para>
@@ -1666,6 +1682,28 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
         Standard error is not logged, but can be captured by the
         hook redirecting its standard error to standard output.
       </para>
+      <variablelist>
+        <varlistentry>
+          <term>
+            <option>lxc.hook.version</option>
+          </term>
+          <listitem>
+            <para>
+            To pass the arguments in new style via environment variables set to
+            1 otherwise set to 0 to pass them as arguments.
+            This setting affects all hooks arguments that were traditionally
+            passed as arguments to the script. Specifically, it affects the
+            container name, section (e.g. 'lxc', 'net') and hook type (e.g.
+            'clone', 'mount', 'pre-mount') arguments. If new-style hooks are
+            used then the arguments will be available as environment variables.
+            The container name will be set in LXC_NAME. (This is set
+            independently of the value used for this config item.) The section
+            will be set in LXC_HOOK_SECTION and the hook type will be set in
+            LXC_HOOK_TYPE.
+            </para>
+          </listitem>
+        </varlistentry>
+      </variablelist>
       <variablelist>
         <varlistentry>
           <term>

src/lxc/conf.c

@@ -2484,6 +2484,7 @@ struct lxc_conf *lxc_conf_init(void)
 	lxc_list_init(&new->limits);
 	lxc_list_init(&new->sysctls);
 	lxc_list_init(&new->procs);
+	new->hooks_version = 0;
 	for (i = 0; i < NUM_LXC_HOOKS; i++)
 		lxc_list_init(&new->hooks[i]);
 	lxc_list_init(&new->groups);

src/lxc/conf.h

@@ -295,7 +295,11 @@ struct lxc_conf {
 	struct lxc_rootfs rootfs;
 	char *ttydir;
 	int close_all_fds;
+
+	struct {
+		unsigned int hooks_version;
 		struct lxc_list hooks[NUM_LXC_HOOKS];
+	};
 
 	char *lsm_aa_profile;
 	unsigned int lsm_aa_allow_incomplete;

src/lxc/confile.c

@@ -92,6 +92,7 @@ lxc_config_define(ephemeral);
 lxc_config_define(execute_cmd);
 lxc_config_define(group);
 lxc_config_define(hooks);
+lxc_config_define(hooks_version);
 lxc_config_define(idmaps);
 lxc_config_define(includefiles);
 lxc_config_define(init_cmd);
@@ -168,11 +169,12 @@ static struct lxc_config_t config[] = {
 	{ "lxc.hook.destroy",              false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
 	{ "lxc.hook.mount",                false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
 	{ "lxc.hook.post-stop",            false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
-	{ "lxc.hook.start-host",           false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
-	{ "lxc.hook.pre-start",            false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
 	{ "lxc.hook.pre-mount",            false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
+	{ "lxc.hook.pre-start",            false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
 	{ "lxc.hook.start",                false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
+	{ "lxc.hook.start-host",           false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
 	{ "lxc.hook.stop",                 false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
+	{ "lxc.hook.version",              false,                  set_config_hooks_version,               get_config_hooks_version,               clr_config_hooks_version,             },
 	{ "lxc.hook",                      false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
 	{ "lxc.idmap",                     false,                  set_config_idmaps,                      get_config_idmaps,                      clr_config_idmaps,                    },
 	{ "lxc.include",                   false,                  set_config_includefiles,                get_config_includefiles,                clr_config_includefiles,              },
@@ -980,6 +982,29 @@ static int set_config_hooks(const char *key, const char *value,
 	return -1;
 }
 
+static int set_config_hooks_version(const char *key, const char *value,
+				    struct lxc_conf *lxc_conf, void *data)
+{
+	int ret;
+	unsigned int tmp;
+
+	if (lxc_config_value_empty(value))
+		return clr_config_hooks_version(key, lxc_conf, NULL);
+
+	ret = lxc_safe_uint(value, &tmp);
+	if (ret < 0)
+		return -1;
+
+	if (tmp > 1) {
+		ERROR("Invalid hook version specified. Currently only 0 "
+		      "(legacy) and 1 are supported");
+		return -1;
+	}
+
+	lxc_conf->hooks_version = tmp;
+	return 0;
+}
+
 static int set_config_personality(const char *key, const char *value,
 				  struct lxc_conf *lxc_conf, void *data)
 {
@@ -3154,6 +3179,12 @@ static int get_config_hooks(const char *key, char *retv, int inlen,
 	return fulllen;
 }
 
+static int get_config_hooks_version(const char *key, char *retv, int inlen,
+				    struct lxc_conf *c, void *data)
+{
+	return lxc_get_conf_int(c, retv, inlen, c->hooks_version);
+}
+
 static int get_config_net(const char *key, char *retv, int inlen,
 			  struct lxc_conf *c, void *data)
 {
@@ -3688,6 +3719,14 @@ static inline int clr_config_hooks(const char *key, struct lxc_conf *c,
 	return lxc_clear_hooks(c, key);
 }
 
+static inline int clr_config_hooks_version(const char *key, struct lxc_conf *c,
+					   void *data)
+{
+	/* default to legacy hooks version */
+	c->hooks_version = 0;
+	return 0;
+}
+
 static inline int clr_config_net(const char *key, struct lxc_conf *c,
 				 void *data)
 {

src/tests/parse_config_file.c

@@ -301,16 +301,16 @@ static int set_get_compare_clear_save_load_network(
 
 int main(int argc, char *argv[])
 {
+	int ret;
 	struct lxc_container *c;
-	int fd = -1;
+	int fd = -1, fret = EXIT_FAILURE;
-	int ret = EXIT_FAILURE;
 	char tmpf[] = "lxc-parse-config-file-XXXXXX";
 	char retval[4096] = {0};
 
 	fd = mkstemp(tmpf);
 	if (fd < 0) {
 		lxc_error("%s\n", "Could not create temporary file");
-		exit(ret);
+		exit(fret);
 	}
 	close(fd);
 
@@ -1110,10 +1110,23 @@ int main(int argc, char *argv[])
 		goto non_test_error;
 	}
 
-	ret = EXIT_SUCCESS;
+	ret = set_get_compare_clear_save_load(c, "lxc.hook.version", "1", tmpf, true);
+	if (ret < 0) {
+		lxc_error("%s\n", "lxc.hook.version");
+		goto non_test_error;
+	}
+
+	ret = set_get_compare_clear_save_load(c, "lxc.hook.version", "2", tmpf, true);
+	if (ret == 0) {
+		lxc_error("%s\n", "lxc.hook.version");
+		goto non_test_error;
+	}
+
+	fret = EXIT_SUCCESS;
+
 non_test_error:
 	(void)unlink(tmpf);
 	(void)rmdir(dirname(c->configfile));
 	lxc_container_put(c);
-	exit(ret);
+	exit(fret);
 }