[lxc-devel] [PATCH 1/1] lxc: manually move NICs back to host after container stops

[Stéphane Graber]

On Fri, Mar 07, 2014 at 12:24:27PM -0600, Serge Hallyn wrote:
> This prevents things like bridges from being destroyed by the kernel.
> 
> My hope is that just doing this will be enough to also ensure that
> the device will be available to be renamed immediately, so that
> we don't need to do a retry loop.
> 
> Tested with a dummy device.  renaming dummy0 to dummy5 in container,
> then shutting down container, returns dummy0 to the host.
> 
> Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>

Acked-by: Stéphane Graber <stgraber at ubuntu.com>

> ---
>  src/lxc/conf.c  | 40 +++++++++++++++++++++++++++++++++++++++-
>  src/lxc/conf.h  |  2 +-
>  src/lxc/start.c | 26 +++++++++++++++++++++++++-
>  3 files changed, 65 insertions(+), 3 deletions(-)
> 
> diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> index 1cb058d..58a9b4f 100644
> --- a/src/lxc/conf.c
> +++ b/src/lxc/conf.c
> @@ -2558,11 +2558,49 @@ static int setup_network(struct lxc_list *network)
>  	return 0;
>  }
>  
> -void lxc_rename_phys_nics_on_shutdown(struct lxc_conf *conf)
> +/* try to move physical nics to the init netns */
> +void restore_phys_nics_to_netns(int netnsfd, struct lxc_conf *conf)
> +{
> +	int i, ret, oldfd;
> +	char path[MAXPATHLEN];
> +
> +	if (netnsfd < 0)
> +		return;
> +
> +	ret = snprintf(path, MAXPATHLEN, "/proc/self/ns/net");
> +	if (ret < 0 || ret >= MAXPATHLEN) {
> +		WARN("Failed to open monitor netns fd");
> +		return;
> +	}
> +	if ((oldfd = open(path, O_RDONLY)) < 0) {
> +		SYSERROR("Failed to open monitor netns fd");
> +		return;
> +	}
> +	if (setns(netnsfd, 0) != 0) {
> +		SYSERROR("Failed to enter container netns to reset nics");
> +		close(oldfd);
> +		return;
> +	}
> +	for (i=0; i<conf->num_savednics; i++) {
> +		struct saved_nic *s = &conf->saved_nics[i];
> +		if (lxc_netdev_move_by_index(s->ifindex, 1))
> +			WARN("Error moving nic index:%d back to host netns",
> +					s->ifindex);
> +	}
> +	if (setns(oldfd, 0) != 0)
> +		SYSERROR("Failed to re-enter monitor's netns");
> +	close(oldfd);
> +}
> +
> +void lxc_rename_phys_nics_on_shutdown(int netnsfd, struct lxc_conf *conf)
>  {
>  	int i;
>  
> +	if (conf->num_savednics == 0)
> +		return;
> +
>  	INFO("running to reset %d nic names", conf->num_savednics);
> +	restore_phys_nics_to_netns(netnsfd, conf);
>  	for (i=0; i<conf->num_savednics; i++) {
>  		struct saved_nic *s = &conf->saved_nics[i];
>  		INFO("resetting nic %d to %s", s->ifindex, s->orig_name);
> diff --git a/src/lxc/conf.h b/src/lxc/conf.h
> index 4591470..2804212 100644
> --- a/src/lxc/conf.h
> +++ b/src/lxc/conf.h
> @@ -369,7 +369,7 @@ extern int lxc_clear_groups(struct lxc_conf *c);
>  struct cgroup_process_info;
>  extern int lxc_setup(struct lxc_handler *handler);
>  
> -extern void lxc_rename_phys_nics_on_shutdown(struct lxc_conf *conf);
> +extern void lxc_rename_phys_nics_on_shutdown(int netnsfd, struct lxc_conf *conf);
>  
>  extern int find_unmapped_nsuid(struct lxc_conf *conf, enum idtype idtype);
>  extern int mapped_hostid(unsigned id, struct lxc_conf *conf, enum idtype idtype);
> diff --git a/src/lxc/start.c b/src/lxc/start.c
> index eb1c659..bae01e4 100644
> --- a/src/lxc/start.c
> +++ b/src/lxc/start.c
> @@ -1000,12 +1000,33 @@ out_abort:
>  	return -1;
>  }
>  
> +int get_netns_fd(int pid)
> +{
> +	char path[MAXPATHLEN];
> +	int ret, fd;
> +
> +	ret = snprintf(path, MAXPATHLEN, "/proc/%d/ns/net", pid);
> +	if (ret < 0 || ret >= MAXPATHLEN) {
> +		WARN("Failed to pin netns file for pid %d", pid);
> +		return -1;
> +	}
> +
> +	fd = open(path, O_RDONLY);
> +	if (fd < 0) {
> +		WARN("Failed to pin netns file %s for pid %d: %s",
> +				path, pid, strerror(errno));
> +		return -1;
> +	}
> +	return fd;
> +}
> +
>  int __lxc_start(const char *name, struct lxc_conf *conf,
>  		struct lxc_operations* ops, void *data, const char *lxcpath)
>  {
>  	struct lxc_handler *handler;
>  	int err = -1;
>  	int status;
> +	int netnsfd = -1;
>  
>  	handler = lxc_init(name, conf, lxcpath);
>  	if (!handler) {
> @@ -1032,6 +1053,8 @@ int __lxc_start(const char *name, struct lxc_conf *conf,
>  		goto out_fini_nonet;
>  	}
>  
> +	netnsfd = get_netns_fd(handler->pid);
> +
>  	err = lxc_poll(name, handler);
>  	if (err) {
>  		ERROR("mainloop exited with an error");
> @@ -1065,7 +1088,8 @@ int __lxc_start(const char *name, struct lxc_conf *conf,
>  		}
>          }
>  
> -	lxc_rename_phys_nics_on_shutdown(handler->conf);
> +	lxc_rename_phys_nics_on_shutdown(netnsfd, handler->conf);
> +	close(netnsfd);
>  
>  	if (handler->pinfd >= 0) {
>  		close(handler->pinfd);
> -- 
> 1.9.0
> 
> _______________________________________________
> lxc-devel mailing list
> lxc-devel at lists.linuxcontainers.org
> http://lists.linuxcontainers.org/listinfo/lxc-devel

-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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