[lxc-devel] [PATCH 1/2] Support providing env vars to container init
Serge Hallyn
serge.hallyn at ubuntu.com
Mon Jul 21 23:44:50 UTC 2014
Quoting Stéphane Graber (stgraber at ubuntu.com):
> 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);
putenv will segv if the allocation fails here (i.e. list_item->elem is NULL).
Please do add a check for that. Other than that,
Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
> + 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
>
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