[CRIU] Re: [PATCH 5/5] util: move network socket to free FD during restore

[Pavel Emelyanov]

On 08/21/2012 07:20 PM, Adrian Reber wrote:
> The socket listening on the network has to be moved during the
> restore so that it does not collide with FDs which are trying
> to be restored.
> 
> Signed-off-by: Adrian Reber <adrian at lisas.de>
> ---
>  image.c           |    7 +++++++
>  include/crtools.h |    1 +
>  util.c            |    9 +++++++++
>  3 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/image.c b/image.c
> index 969017a..0d84c5c 100644
> --- a/image.c
> +++ b/image.c
> @@ -366,3 +366,10 @@ int reopen_listen_socket()
>  		return open_listen_socket(network_host, network_port);
>  	return 0;
>  }
> +
> +void update_listen_socket(int fd)
> +{
> +	if (sockfd == -1)
> +		return;
> +	sockfd = fd;
> +}
> diff --git a/include/crtools.h b/include/crtools.h
> index c092802..f056327 100644
> --- a/include/crtools.h
> +++ b/include/crtools.h
> @@ -135,6 +135,7 @@ extern void close_image_dir(void);
>  extern int open_listen_socket(char *host, int port);
>  extern void close_listen_socket();
>  extern int reopen_listen_socket();
> +extern void update_listen_socket(int fd);
>  
>  int open_image(int type, unsigned long flags, ...);
>  #define open_image_ro(type, ...) open_image(type, O_RDONLY, ##__VA_ARGS__)
> diff --git a/util.c b/util.c
> index 4969e8d..91795d1 100644
> --- a/util.c
> +++ b/util.c
> @@ -83,6 +83,15 @@ int reopen_fd_as_safe(char *file, int line, int new_fd, int old_fd, bool allow_r
>  	if (old_fd != new_fd) {
>  
>  		if (!allow_reuse_fd) {
> +			/* see if we are running a network migration */
> +			tmp = open_listen_socket(NULL, 0);
> +			if (tmp != -1) {
> +				int tmp2;
> +				/* yes, network socket is open; let's move it */
> +				tmp2 = fcntl(tmp, F_DUPFD, new_fd);
> +				update_listen_socket(tmp2);
> +				close(tmp);

You should just place a call to move_img_fd to proper place to prevent
it from being overwritten by the restore fd.

> +			}
>  			if (fcntl(new_fd, F_GETFD) != -1 || errno != EBADF) {
>  				if (new_fd < 3) {
>  					/*