[lxc-devel] [RFC PATCH] lxc: add clone hook.
Serge Hallyn
serge.hallyn at ubuntu.com
Wed May 15 15:13:23 UTC 2013
Quoting Stéphane Graber (stgraber at ubuntu.com):
> On 05/15/2013 10:23 AM, Serge Hallyn wrote:
> > Add a clone hook called from api_clone. Pass arguments to it from
> > lxc_clone.c.
> >
> > The clone update hook is called while the container's bdev is mounted.
> > Information about the container is passed in through environment
> > variables LXC_ROOTFS_PATH, LXC_NAME, The LXC_ROOTFS_MOUNT, and
> > LXC_CONFIG_FILE.
> >
> > LXC_ROOTFS_MOUNT=/usr/lib/x86_64-linux-gnu/lxc
> > LXC_CONFIG_FILE=/var/lib/lxc/demo3/config
> > LXC_ROOTFS_PATH=/var/lib/lxc/demo3/rootfs
> > LXC_NAME=demo3
> >
> > So from the hook, updates to the container should be made under
> > $LXC_ROOTFS_MOUNT/ .
> >
> > The hook also receives command line arguments as follows:
> > First argument is container name, second is always 'lxc', third
> > is the hook name (always clone), then come the arguments which
> > were passed to lxc-clone. I.e. when I did:
> >
> > sudo lxc-clone demo2 demo3 -- hey there dude
> >
> > the arguments passed in were "demo3 lxc clone hey there dude"
> >
> > I personally would like to drop the first two arguments. The
> > name is available as $LXC_NAME, and the section argument ('lxc')
> > is meaningless. However, doing so risks invalidating existing
> > hooks.
> >
> > Soon analogous create and destroy hooks will be added as well.
>
> I think I'd have preferred storing the command arguments in
> LXC_CLONE_ARGS instead of directly in argv. Doing so would allow us to
> remove/add other arguments without breaking all existing hooks.
>
> The user could then do "set -- $LXC_CLONE_ARGS" and just use $1... as usual.
>
> But I'm not horribly opposed to the proposed implementation and the rest
> looks good.
Actually,
yeah that would let menot add the argv[] to run_lxc_hooks, and make the
patch quite a bit shorter.
I'll redo it like that.
Please don't apply :)
> Acked-by: Stéphane Graber <stgraber at ubuntu.com>
>
> > Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
> > ---
> > src/lxc/conf.c | 63 +++++++++++++++++++++++++++++++++++++++++++++-----
> > src/lxc/conf.h | 4 ++--
> > src/lxc/confile.c | 3 +++
> > src/lxc/lxc_clone.c | 16 ++++++-------
> > src/lxc/lxccontainer.c | 55 ++++++++++++++++++++++++++++++-------------
> > src/lxc/lxccontainer.h | 2 +-
> > src/lxc/start.c | 6 ++---
> > 7 files changed, 113 insertions(+), 36 deletions(-)
> >
> > diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> > index 746a2db..61e45b1 100644
> > --- a/src/lxc/conf.c
> > +++ b/src/lxc/conf.c
> > @@ -173,7 +173,7 @@ return -1;
> > #endif
> >
> > char *lxchook_names[NUM_LXC_HOOKS] = {
> > - "pre-start", "pre-mount", "mount", "autodev", "start", "post-stop" };
> > + "pre-start", "pre-mount", "mount", "autodev", "start", "post-stop", "clone" };
> >
> > typedef int (*instanciate_cb)(struct lxc_handler *, struct lxc_netdev *);
> >
> > @@ -336,6 +336,55 @@ static int run_buffer(char *buffer)
> > return 0;
> > }
> >
> > +static int run_script_argv(const char *name, const char *section,
> > + const char *script, const char *hook, char **argsin)
> > +{
> > + int ret, i;
> > + char *buffer;
> > + size_t size = 0;
> > +
> > + INFO("Executing script '%s' for container '%s', config section '%s'",
> > + script, name, section);
> > +
> > + for (i=0; argsin && argsin[i]; i++)
> > + size += strlen(argsin[i]) + 1;
> > +
> > + size += strlen(hook) + 1;
> > +
> > + size += strlen(script);
> > + size += strlen(name);
> > + size += strlen(section);
> > + size += 3;
> > +
> > + if (size > INT_MAX)
> > + return -1;
> > +
> > + buffer = alloca(size);
> > + if (!buffer) {
> > + ERROR("failed to allocate memory");
> > + return -1;
> > + }
> > +
> > + ret = snprintf(buffer, size, "%s %s %s %s", script, name, section, hook);
> > + if (ret < 0 || ret >= size) {
> > + ERROR("Script name too long");
> > + return -1;
> > + }
> > +
> > + for (i=0; argsin && argsin[i]; i++) {
> > + int len = size-ret;
> > + int rc;
> > + rc = snprintf(buffer + ret, len, " %s", argsin[i]);
> > + if (rc < 0 || rc >= len) {
> > + ERROR("Script args too long");
> > + return -1;
> > + }
> > + ret += rc;
> > + }
> > +
> > + return run_buffer(buffer);
> > +}
> > +
> > static int run_script(const char *name, const char *section,
> > const char *script, ...)
> > {
> > @@ -2752,7 +2801,7 @@ int lxc_setup(const char *name, struct lxc_conf *lxc_conf)
> > return -1;
> > }
> >
> > - if (run_lxc_hooks(name, "pre-mount", lxc_conf)) {
> > + if (run_lxc_hooks(name, "pre-mount", lxc_conf, NULL)) {
> > ERROR("failed to run pre-mount hooks for container '%s'.", name);
> > return -1;
> > }
> > @@ -2779,13 +2828,13 @@ int lxc_setup(const char *name, struct lxc_conf *lxc_conf)
> > return -1;
> > }
> >
> > - if (run_lxc_hooks(name, "mount", lxc_conf)) {
> > + if (run_lxc_hooks(name, "mount", lxc_conf, NULL)) {
> > ERROR("failed to run mount hooks for container '%s'.", name);
> > return -1;
> > }
> >
> > if (lxc_conf->autodev) {
> > - if (run_lxc_hooks(name, "autodev", lxc_conf)) {
> > + if (run_lxc_hooks(name, "autodev", lxc_conf, NULL)) {
> > ERROR("failed to run autodev hooks for container '%s'.", name);
> > return -1;
> > }
> > @@ -2852,7 +2901,7 @@ int lxc_setup(const char *name, struct lxc_conf *lxc_conf)
> > return 0;
> > }
> >
> > -int run_lxc_hooks(const char *name, char *hook, struct lxc_conf *conf)
> > +int run_lxc_hooks(const char *name, char *hook, struct lxc_conf *conf, char *argv[])
> > {
> > int which = -1;
> > struct lxc_list *it;
> > @@ -2869,12 +2918,14 @@ int run_lxc_hooks(const char *name, char *hook, struct lxc_conf *conf)
> > which = LXCHOOK_START;
> > else if (strcmp(hook, "post-stop") == 0)
> > which = LXCHOOK_POSTSTOP;
> > + else if (strcmp(hook, "clone") == 0)
> > + which = LXCHOOK_CLONE;
> > else
> > return -1;
> > lxc_list_for_each(it, &conf->hooks[which]) {
> > int ret;
> > char *hookname = it->elem;
> > - ret = run_script(name, "lxc", hookname, hook, NULL);
> > + ret = run_script_argv(name, "lxc", hookname, hook, argv);
> > if (ret)
> > return ret;
> > }
> > diff --git a/src/lxc/conf.h b/src/lxc/conf.h
> > index 465b1ec..5139aa3 100644
> > --- a/src/lxc/conf.h
> > +++ b/src/lxc/conf.h
> > @@ -237,7 +237,7 @@ struct lxc_rootfs {
> > */
> > enum lxchooks {
> > LXCHOOK_PRESTART, LXCHOOK_PREMOUNT, LXCHOOK_MOUNT, LXCHOOK_AUTODEV,
> > - LXCHOOK_START, LXCHOOK_POSTSTOP, NUM_LXC_HOOKS};
> > + LXCHOOK_START, LXCHOOK_POSTSTOP, LXCHOOK_CLONE, NUM_LXC_HOOKS};
> > extern char *lxchook_names[NUM_LXC_HOOKS];
> >
> > struct saved_nic {
> > @@ -284,7 +284,7 @@ struct lxc_conf {
> > char *rcfile; // Copy of the top level rcfile we read
> > };
> >
> > -int run_lxc_hooks(const char *name, char *hook, struct lxc_conf *conf);
> > +int run_lxc_hooks(const char *name, char *hook, struct lxc_conf *conf, char *argv[]);
> >
> > extern int setup_cgroup(const char *cgpath, struct lxc_list *cgroups);
> > extern int detect_shared_rootfs(void);
> > diff --git a/src/lxc/confile.c b/src/lxc/confile.c
> > index aec8177..fb851c9 100644
> > --- a/src/lxc/confile.c
> > +++ b/src/lxc/confile.c
> > @@ -117,6 +117,7 @@ static struct lxc_config_t config[] = {
> > { "lxc.hook.autodev", config_hook },
> > { "lxc.hook.start", config_hook },
> > { "lxc.hook.post-stop", config_hook },
> > + { "lxc.hook.clone", config_hook },
> > { "lxc.network.type", config_network_type },
> > { "lxc.network.flags", config_network_flags },
> > { "lxc.network.link", config_network_link },
> > @@ -894,6 +895,8 @@ static int config_hook(const char *key, const char *value,
> > return add_hook(lxc_conf, LXCHOOK_START, copy);
> > else if (strcmp(key, "lxc.hook.post-stop") == 0)
> > return add_hook(lxc_conf, LXCHOOK_POSTSTOP, copy);
> > + else if (strcmp(key, "lxc.hook.clone") == 0)
> > + return add_hook(lxc_conf, LXCHOOK_CLONE, copy);
> > SYSERROR("Unknown key: %s", key);
> > free(copy);
> > return -1;
> > diff --git a/src/lxc/lxc_clone.c b/src/lxc/lxc_clone.c
> > index b9c7a6e..2b0ee43 100644
> > --- a/src/lxc/lxc_clone.c
> > +++ b/src/lxc/lxc_clone.c
> > @@ -16,7 +16,7 @@
> >
> > lxc_log_define(lxc_clone, lxc);
> >
> > -void usage(char *me)
> > +void usage(const char *me)
> > {
> > printf("Usage: %s [-s] [-B backingstore] [-L size] [-K] [-M] [-H]\n", me);
> > printf(" [-p lxcpath] [-P newlxcpath] orig new\n");
> > @@ -60,6 +60,7 @@ int main(int argc, char *argv[])
> > long newsize = 0;
> > char *bdevtype = NULL, *lxcpath = NULL, *newpath = NULL, *fstype = NULL;
> > char *orig = NULL, *new = NULL, *vgname = NULL;
> > + char **args = NULL;
> > char c;
> >
> > if (argc < 3)
> > @@ -86,14 +87,13 @@ int main(int argc, char *argv[])
> > default: break;
> > }
> > }
> > - if (optind == argc-2 && !orig)
> > + if (optind < argc && !orig)
> > orig = argv[optind++];
> > - if (optind == argc-1 && !new)
> > + if (optind < argc && !new)
> > new = argv[optind++];
> > - if (optind < argc) {
> > - printf("%d extraneous arguments\n", argc-optind);
> > - usage(argv[0]);
> > - }
> > + if (optind < argc)
> > + /* arguments for the clone hook */
> > + args = &argv[optind];
> > if (!new || !orig) {
> > printf("Error: you must provide orig and new names\n");
> > usage(argv[0]);
> > @@ -124,7 +124,7 @@ int main(int argc, char *argv[])
> > lxc_container_put(c1);
> > exit(1);
> > }
> > - c2 = c1->clone(c1, new, newpath, flags, bdevtype, NULL, newsize);
> > + c2 = c1->clone(c1, new, newpath, flags, bdevtype, NULL, newsize, args);
> > if (c2 == NULL) {
> > lxc_container_put(c1);
> > fprintf(stderr, "clone failed\n");
> > diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> > index bac94c2..23db6f2 100644
> > --- a/src/lxc/lxccontainer.c
> > +++ b/src/lxc/lxccontainer.c
> > @@ -1364,16 +1364,14 @@ static int copy_storage(struct lxc_container *c0, struct lxc_container *c,
> > return 0;
> > }
> >
> > -static int clone_update_rootfs(struct lxc_container *c, int flags)
> > +static int clone_update_rootfs(struct lxc_container *c, int flags, char **hookargs)
> > {
> > int ret = -1;
> > char path[MAXPATHLEN];
> > struct bdev *bdev;
> > FILE *fout;
> > pid_t pid;
> > -
> > - if (flags & LXC_CLONE_KEEPNAME)
> > - return 0;
> > + struct lxc_conf *conf = c->lxc_conf;
> >
> > /* update hostname in rootfs */
> > /* we're going to mount, so run in a clean namespace to simplify cleanup */
> > @@ -1393,17 +1391,41 @@ static int clone_update_rootfs(struct lxc_container *c, int flags)
> > exit(1);
> > if (bdev->ops->mount(bdev) < 0)
> > exit(1);
> > - ret = snprintf(path, MAXPATHLEN, "%s/etc/hostname", bdev->dest);
> > - if (ret < 0 || ret >= MAXPATHLEN)
> > - exit(1);
> > - if (!(fout = fopen(path, "w"))) {
> > - SYSERROR("unable to open %s: ignoring\n", path);
> > - exit(0);
> > +
> > + if (!lxc_list_empty(&conf->hooks[LXCHOOK_CLONE])) {
> > + /* Start of environment variable setup for hooks */
> > + if (setenv("LXC_NAME", c->name, 1)) {
> > + SYSERROR("failed to set environment variable for container name");
> > + }
> > + if (setenv("LXC_CONFIG_FILE", conf->rcfile, 1)) {
> > + SYSERROR("failed to set environment variable for config path");
> > + }
> > + if (setenv("LXC_ROOTFS_MOUNT", conf->rootfs.mount, 1)) {
> > + SYSERROR("failed to set environment variable for rootfs mount");
> > + }
> > + if (setenv("LXC_ROOTFS_PATH", conf->rootfs.path, 1)) {
> > + SYSERROR("failed to set environment variable for rootfs mount");
> > + }
> > +
> > + if (run_lxc_hooks(c->name, "clone", conf, hookargs)) {
> > + ERROR("Error executing clone hook for %s", c->name);
> > + exit(1);
> > + }
> > + }
> > +
> > + if (!(flags & LXC_CLONE_KEEPNAME)) {
> > + ret = snprintf(path, MAXPATHLEN, "%s/etc/hostname", bdev->dest);
> > + if (ret < 0 || ret >= MAXPATHLEN)
> > + exit(1);
> > + if (!(fout = fopen(path, "w"))) {
> > + SYSERROR("unable to open %s: ignoring\n", path);
> > + exit(0);
> > + }
> > + if (fprintf(fout, "%s", c->name) < 0)
> > + exit(1);
> > + if (fclose(fout) < 0)
> > + exit(1);
> > }
> > - if (fprintf(fout, "%s", c->name) < 0)
> > - exit(1);
> > - if (fclose(fout) < 0)
> > - exit(1);
> > exit(0);
> > }
> >
> > @@ -1436,7 +1458,8 @@ static int create_file_dirname(char *path)
> >
> > struct lxc_container *lxcapi_clone(struct lxc_container *c, const char *newname,
> > const char *lxcpath, int flags,
> > - const char *bdevtype, const char *bdevdata, unsigned long newsize)
> > + const char *bdevtype, const char *bdevdata, unsigned long newsize,
> > + char **hookargs)
> > {
> > struct lxc_container *c2 = NULL;
> > char newpath[MAXPATHLEN];
> > @@ -1525,7 +1548,7 @@ struct lxc_container *lxcapi_clone(struct lxc_container *c, const char *newname,
> > if (!c2->save_config(c2, NULL))
> > goto out;
> >
> > - if (clone_update_rootfs(c2, flags) < 0)
> > + if (clone_update_rootfs(c2, flags, hookargs) < 0)
> > goto out;
> >
> > // TODO: update c's lxc.snapshot = count
> > diff --git a/src/lxc/lxccontainer.h b/src/lxc/lxccontainer.h
> > index b6bd97c..67fbed4 100644
> > --- a/src/lxc/lxccontainer.h
> > +++ b/src/lxc/lxccontainer.h
> > @@ -105,7 +105,7 @@ struct lxc_container {
> > */
> > struct lxc_container *(*clone)(struct lxc_container *c, const char *newname,
> > const char *lxcpath, int flags, const char *bdevtype,
> > - const char *bdevdata, unsigned long newsize);
> > + const char *bdevdata, unsigned long newsize, char **hookargs);
> >
> > #if 0
> > bool (*commit_cgroups)(struct lxc_container *c);
> > diff --git a/src/lxc/start.c b/src/lxc/start.c
> > index fd96d4f..995460e 100644
> > --- a/src/lxc/start.c
> > +++ b/src/lxc/start.c
> > @@ -461,7 +461,7 @@ struct lxc_handler *lxc_init(const char *name, struct lxc_conf *conf, const char
> > }
> > /* End of environment variable setup for hooks */
> >
> > - if (run_lxc_hooks(name, "pre-start", conf)) {
> > + if (run_lxc_hooks(name, "pre-start", conf, NULL)) {
> > ERROR("failed to run pre-start hooks for container '%s'.", name);
> > goto out_aborting;
> > }
> > @@ -513,7 +513,7 @@ static void lxc_fini(const char *name, struct lxc_handler *handler)
> > lxc_set_state(name, handler, STOPPING);
> > lxc_set_state(name, handler, STOPPED);
> >
> > - if (run_lxc_hooks(name, "post-stop", handler->conf))
> > + if (run_lxc_hooks(name, "post-stop", handler->conf, NULL))
> > ERROR("failed to run post-stop hooks for container '%s'.", name);
> >
> > /* reset mask set by setup_signal_fd */
> > @@ -676,7 +676,7 @@ static int do_start(void *data)
> > if (lxc_seccomp_load(handler->conf) != 0)
> > goto out_warn_father;
> >
> > - if (run_lxc_hooks(handler->name, "start", handler->conf)) {
> > + if (run_lxc_hooks(handler->name, "start", handler->conf, NULL)) {
> > ERROR("failed to run start hooks for container '%s'.", handler->name);
> > goto out_warn_father;
> > }
> >
>
>
> --
> Stéphane Graber
> Ubuntu developer
> http://www.ubuntu.com
>
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