[lxc-devel] [PATCH 1/2] Support providing env vars to container init

[Stéphane Graber]

From: Matt Palmer <mpalmer at hezmatt.org>

It's quite useful to be able to configure containers by specifying
environment variables, which init (or initscripts) can use to adjust the
container's operation.

This patch adds one new configuration parameter, `lxc.environment`, which
can be specified zero or more times to define env vars to set in the
container, like this:

    lxc.environment = APP_ENV=production
    lxc.environment = SYSLOG_SERVER=192.0.2.42
    lxc.environment = SOMETHING_FUNNY=platypus

Default operation is unchanged; if the user doesn't specify any
lxc.environment parameters, the container environment will be what it is
today ('container=lxc').

Signed-off-by: Matt Palmer <mpalmer at hezmatt.org>
Acked-by: Stéphane Graber <stgraber at ubuntu.com>
---
 doc/lxc.container.conf.sgml.in | 38 ++++++++++++++++++++++++++++++++++++++
 src/lxc/conf.c                 |  1 +
 src/lxc/conf.h                 |  4 ++++
 src/lxc/confile.c              | 23 +++++++++++++++++++++++
 src/lxc/start.c                | 10 +++++++++-
 5 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/doc/lxc.container.conf.sgml.in b/doc/lxc.container.conf.sgml.in
index 4f8e4e9..d0c18fe 100644
--- a/doc/lxc.container.conf.sgml.in
+++ b/doc/lxc.container.conf.sgml.in
@@ -1514,6 +1514,44 @@ mknod errno 0
     </para>
 
     </refsect2>
+
+    <refsect2>
+      <title>Container Environment</title>
+      <para>
+	If you want to pass environment variables into the container (that
+	is, environment variables which will be available to init and all of
+	its descendents), you can use <command>lxc.environment</command>
+	parameters to do so.  Be careful that you do not pass in anything
+	sensitive; any process in the container which doesn't have its
+	environment scrubbed will have these variables available to it, and
+	environment variables are always available via
+	<command>/proc/PID/environ</command>.
+      </para>
+
+      <para>
+        This configuration parameter can be specified multiple times; once
+        for each environment variable you wish to configure.
+      </para>
+
+      <variablelist>
+	<varlistentry>
+	  <term>
+	    <option>lxc.environment</option>
+	  </term>
+	  <listitem>
+	    <para>
+	      Specify an environment variable to pass into the container.
+	      Example:
+	    </para>
+	    <programlisting>
+	      lxc.environment = APP_ENV=production
+	      lxc.environment = SYSLOG_SERVER=192.0.2.42
+	    </programlisting>
+	  </listitem>
+	</varlistentry>
+      </variablelist>
+    </refsect2>
+
   </refsect1>
 
   <refsect1>
diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index 052db98..e930b4d 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -2701,6 +2701,7 @@ struct lxc_conf *lxc_conf_init(void)
 	lxc_list_init(&new->id_map);
 	lxc_list_init(&new->includes);
 	lxc_list_init(&new->aliens);
+	lxc_list_init(&new->environment);
 	for (i=0; i<NUM_LXC_HOOKS; i++)
 		lxc_list_init(&new->hooks[i]);
 	lxc_list_init(&new->groups);
diff --git a/src/lxc/conf.h b/src/lxc/conf.h
index 3527c44..1bc6ba3 100644
--- a/src/lxc/conf.h
+++ b/src/lxc/conf.h
@@ -344,6 +344,10 @@ struct lxc_conf {
 	struct lxc_list includes;
 	/* config entries which are not "lxc.*" are aliens */
 	struct lxc_list aliens;
+
+	/* list of environment variables we'll add to the container when
+	 * started */
+	struct lxc_list environment;
 };
 
 int run_lxc_hooks(const char *name, char *hook, struct lxc_conf *conf,
diff --git a/src/lxc/confile.c b/src/lxc/confile.c
index f3cab6b..2f32776 100644
--- a/src/lxc/confile.c
+++ b/src/lxc/confile.c
@@ -96,6 +96,7 @@ static int config_haltsignal(const char *, const char *, struct lxc_conf *);
 static int config_stopsignal(const char *, const char *, struct lxc_conf *);
 static int config_start(const char *, const char *, struct lxc_conf *);
 static int config_group(const char *, const char *, struct lxc_conf *);
+static int config_environment(const char *, const char *, struct lxc_conf *);
 
 static struct lxc_config_t config[] = {
 
@@ -152,6 +153,7 @@ static struct lxc_config_t config[] = {
 	{ "lxc.start.delay",          config_start                },
 	{ "lxc.start.order",          config_start                },
 	{ "lxc.group",                config_group                },
+	{ "lxc.environment",          config_environment          },
 };
 
 struct signame {
@@ -1064,6 +1066,27 @@ static int config_group(const char *key, const char *value,
 	return ret;
 }
 
+static int config_environment(const char *key, const char *value,
+                              struct lxc_conf *lxc_conf)
+{
+	struct lxc_list *list_item = NULL;
+
+	list_item = malloc(sizeof(*list_item));
+	if (!list_item)
+		goto freak_out;
+
+	list_item->elem = strdup(value);
+
+	lxc_list_add_tail(&lxc_conf->environment, list_item);
+
+	return 0;
+
+freak_out:
+	if (list_item) free(list_item);
+
+	return -1;
+}
+
 static int config_tty(const char *key, const char *value,
 		      struct lxc_conf *lxc_conf)
 {
diff --git a/src/lxc/start.c b/src/lxc/start.c
index 555e4c4..bb136af 100644
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -609,6 +609,7 @@ static int read_unpriv_netifindex(struct lxc_list *network)
 
 static int do_start(void *data)
 {
+	struct lxc_list *iterator;
 	struct lxc_handler *handler = data;
 	const char *lsm_label = NULL;
 
@@ -727,8 +728,15 @@ static int do_start(void *data)
 		/* don't error out though */
 	}
 
+	lxc_list_for_each(iterator, &handler->conf->environment) {
+		if (putenv((char *)iterator->elem)) {
+			SYSERROR("failed to set environment variable '%s'", (char *)iterator->elem);
+			goto out_warn_father;
+		}
+	}
+
 	if (putenv("container=lxc")) {
-		SYSERROR("failed to set environment variable");
+		SYSERROR("failed to set environment variable 'container=lxc'");
 		goto out_warn_father;
 	}
 
-- 
1.9.1