[CRIU] Re: [PATCH 04/10] util-net: Add send_fds and recv_fds

[Pavel Emelyanov]

On 03/27/2012 08:23 PM, Cyrill Gorcunov wrote:
> 
> We will need these helpers to transfer file
> descriptors from dumpee to our space.
> 
> Also make send_fd/recv_fd to be a wrappers over
> send_fds/revc_fds to not duplicate the code.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
> ---
>  include/util-net.h |   22 +++++++-
>  util-net.c         |  144 ++++++++++++++++++++++++++++++++++++---------------
>  2 files changed, 120 insertions(+), 46 deletions(-)
> 

> +static int *scm_fdset_init(struct scm_fdset *fdset, struct sockaddr_un *saddr, int saddr_len)
>  {
> -	char cmsgbuf[CMSG_SPACE(sizeof(int))];
> -	struct msghdr hdr = { };
> -	struct iovec data = { };
> -	struct cmsghdr* cmsg;
> -	int *cmsg_data;
> -	char dummy = '*';
> +	struct cmsghdr *cmsg;
>  
> -	data.iov_base	= &dummy;
> -	data.iov_len	= sizeof(dummy);
> +	BUILD_BUG_ON(CR_SCM_MAX_FD > SCM_MAX_FD);
> +	BUILD_BUG_ON(sizeof(fdset->msg_buf) < (CMSG_SPACE(sizeof(int) * CR_SCM_MAX_FD)));
>  
> -	hdr.msg_name	= (struct sockaddr *)saddr;
> -	hdr.msg_namelen	= len;
> -	hdr.msg_iov	= &data;
> -	hdr.msg_iovlen	= 1;
> +	fdset->msg			= 0;
>  
> -	hdr.msg_control = &cmsgbuf;
> -	hdr.msg_controllen = CMSG_LEN(sizeof(int));
> +	fdset->iov.iov_base		= &fdset->msg;
> +	fdset->iov.iov_len		= sizeof(fdset->msg);
>  
> -	cmsg = CMSG_FIRSTHDR(&hdr);
> -	cmsg->cmsg_len   = hdr.msg_controllen;
> -	cmsg->cmsg_level = SOL_SOCKET;
> -	cmsg->cmsg_type  = SCM_RIGHTS;
> +	fdset->hdr.msg_iov		= &fdset->iov;
> +	fdset->hdr.msg_iovlen		= 1;
> +	fdset->hdr.msg_name		= (struct sockaddr *)saddr;
> +	fdset->hdr.msg_namelen		= saddr_len;
>  
> -	cmsg_data = (int *)CMSG_DATA(cmsg);
> -	*cmsg_data = fd;
> +	fdset->hdr.msg_control		= &fdset->msg_buf;
> +	fdset->hdr.msg_controllen	= CMSG_LEN(sizeof(int) * CR_SCM_MAX_FD);
>  
> -	return sys_sendmsg(sock, &hdr, 0);
> +	cmsg				= CMSG_FIRSTHDR(&fdset->hdr);
> +	cmsg->cmsg_len			= fdset->hdr.msg_controllen;
> +	cmsg->cmsg_level		= SOL_SOCKET;
> +	cmsg->cmsg_type			= SCM_RIGHTS;
> +
> +	return (int *)CMSG_DATA(cmsg);
> +}
> +
> +static int scm_fdset_send(int sock, struct scm_fdset *fdset)
> +{
> +	int ret = sys_sendmsg(sock, &fdset->hdr, 0);
> +	if (ret <= 0)
> +		return ret ? : -1;
> +	return 0;
>  }


You did three changes here.

1. Move all on-stack vars into one one-stack structure
2. Changed the way message (char dummy) is sent
3. Added support for more than one fd per message

Please, remove step #2 and make steps 1 and 3 be in separate patches.

Thanks,
Pavel