[lxc-devel] [lxc/master] add a pre-start-host hook
hallyn on Github
lxc-bot at linuxcontainers.org
Wed Sep 20 23:16:41 UTC 2017
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From ae188acca4190c8c9fe5c6ada12fba27f3c74e89 Mon Sep 17 00:00:00 2001
From: Serge Hallyn <shallyn at cisco.com>
Date: Wed, 20 Sep 2017 21:22:46 +0000
Subject: [PATCH] add a pre-start-host hook
This should satisfy several use cases. The one I tested for was CNI.
I replaced the network configuration in a root owned container with:
lxc.net.0.type = empty
lxc.hook.pre-start-host = /bin/lxc-prestart-netns
where /bin/lxc-prestart-netns contained:
=================================
echo "starting" > /tmp/debug
ip link add host1 type veth peer name peer1
ip link set host1 master lxcbr0
ip link set host1 up
ip link set peer1 netns "${LXC_PID}"
=================================
The nic 'peer1' was placed into the container as expected.
FOr this to work, we pass the container init's pid as LXC_PID in
an environment variable, since lxc-info cannot work at that point.
Signed-off-by: Serge Hallyn <shallyn at cisco.com>
---
src/lxc/conf.c | 5 ++++-
src/lxc/conf.h | 1 +
src/lxc/confile.c | 4 ++++
src/lxc/start.c | 15 +++++++++++++--
src/lxc/sync.h | 2 +-
5 files changed, 23 insertions(+), 4 deletions(-)
diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index b6dfa915c..a043b05a8 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -236,7 +236,8 @@ extern int memfd_create(const char *name, unsigned int flags);
char *lxchook_names[NUM_LXC_HOOKS] = {"pre-start", "pre-mount", "mount",
"autodev", "start", "stop",
- "post-stop", "clone", "destroy"};
+ "post-stop", "clone", "destroy",
+ "pre-start-host"};
struct mount_opt {
char *name;
@@ -3285,6 +3286,8 @@ int run_lxc_hooks(const char *name, char *hook, struct lxc_conf *conf,
if (strcmp(hook, "pre-start") == 0)
which = LXCHOOK_PRESTART;
+ else if (strcmp(hook, "pre-start-host") == 0)
+ which = LXCHOOK_PRESTART_HOST;
else if (strcmp(hook, "pre-mount") == 0)
which = LXCHOOK_PREMOUNT;
else if (strcmp(hook, "mount") == 0)
diff --git a/src/lxc/conf.h b/src/lxc/conf.h
index 946ae4a23..292d5138a 100644
--- a/src/lxc/conf.h
+++ b/src/lxc/conf.h
@@ -228,6 +228,7 @@ enum lxchooks {
LXCHOOK_POSTSTOP,
LXCHOOK_CLONE,
LXCHOOK_DESTROY,
+ LXCHOOK_PRESTART_HOST,
NUM_LXC_HOOKS
};
diff --git a/src/lxc/confile.c b/src/lxc/confile.c
index ed83d5dc8..bdc7f9494 100644
--- a/src/lxc/confile.c
+++ b/src/lxc/confile.c
@@ -155,6 +155,7 @@ 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.pre-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.start", false, set_config_hooks, get_config_hooks, clr_config_hooks, },
@@ -980,6 +981,8 @@ static int set_config_hooks(const char *key, const char *value,
if (strcmp(key + 9, "pre-start") == 0)
return add_hook(lxc_conf, LXCHOOK_PRESTART, copy);
+ else if (strcmp(key + 9, "pre-start-host") == 0)
+ return add_hook(lxc_conf, LXCHOOK_PRESTART_HOST, copy);
else if (strcmp(key + 9, "pre-mount") == 0)
return add_hook(lxc_conf, LXCHOOK_PREMOUNT, copy);
else if (strcmp(key + 9, "autodev") == 0)
@@ -4445,6 +4448,7 @@ int lxc_list_subkeys(struct lxc_conf *conf, const char *key, char *retv,
strprint(retv, inlen, "post-stop\n");
strprint(retv, inlen, "pre-mount\n");
strprint(retv, inlen, "pre-start\n");
+ strprint(retv, inlen, "pre-start-host\n");
strprint(retv, inlen, "start\n");
strprint(retv, inlen, "stop\n");
} else if (!strcmp(key, "lxc.cap")) {
diff --git a/src/lxc/start.c b/src/lxc/start.c
index 3baed693a..7ddb6970f 100644
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -1151,6 +1151,7 @@ static int lxc_spawn(struct lxc_handler *handler)
{
int i, flags, ret;
const char *name = handler->name;
+ char pidstr[20];
bool wants_to_map_ids;
int saved_ns_fd[LXC_NS_MAX];
struct lxc_list *id_map;
@@ -1341,13 +1342,23 @@ static int lxc_spawn(struct lxc_handler *handler)
cgroup_disconnect();
cgroups_connected = false;
+ snprintf(pidstr, 20, "%d", handler->pid);
+ if (setenv("LXC_PID", pidstr, 1))
+ SYSERROR("Failed to set environment variable: LXC_PID=%s.", pidstr);
+
+ /* Run any host-side pre-start hooks */
+ if (run_lxc_hooks(name, "pre-start-host", handler->conf, handler->lxcpath, NULL)) {
+ ERROR("Failed to run lxc.hook.pre-start-host for container \"%s\".", name);
+ return -1;
+ }
+
/* Tell the child to complete its initialization and wait for it to exec
* or return an error. (The child will never return
- * LXC_SYNC_POST_CGROUP+1. It will either close the sync pipe, causing
+ * LXC_SYNC_READY_START+1. It will either close the sync pipe, causing
* lxc_sync_barrier_child to return success, or return a different
* value, causing us to error out).
*/
- if (lxc_sync_barrier_child(handler, LXC_SYNC_POST_CGROUP))
+ if (lxc_sync_barrier_child(handler, LXC_SYNC_READY_START))
return -1;
if (lxc_network_recv_name_and_ifindex_from_child(handler) < 0) {
diff --git a/src/lxc/sync.h b/src/lxc/sync.h
index 744db613e..5c0fb3431 100644
--- a/src/lxc/sync.h
+++ b/src/lxc/sync.h
@@ -32,7 +32,7 @@ enum {
LXC_SYNC_CGROUP,
LXC_SYNC_CGROUP_UNSHARE,
LXC_SYNC_CGROUP_LIMITS,
- LXC_SYNC_POST_CGROUP,
+ LXC_SYNC_READY_START,
LXC_SYNC_RESTART,
LXC_SYNC_POST_RESTART,
LXC_SYNC_ERROR = -1 /* Used to report errors from another process */
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