Re: [Qemu-devel] [PATCH 06/17] migration-local: add send_pipefd()

[Daniel P. Berrange]

On Mon, Dec 02, 2013 at 05:19:06PM +0800, Lei Li wrote:
> This patch adds send_pipefd() to pass the pipe file descriptor
> to destination process.
> 
> Signed-off-by: Lei Li <address@hidden>
> ---
>  migration-local.c |   46 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 46 insertions(+), 0 deletions(-)
> 
> diff --git a/migration-local.c b/migration-local.c
> index 929ed60..f479530 100644
> --- a/migration-local.c
> +++ b/migration-local.c
> @@ -167,3 +167,49 @@ fail:
>      g_free(s);
>      return NULL;
>  }
> +
> +
> +/*
> + * Pass a pipe file descriptor to another process.
> + *
> + * Return negative value If pipefd < 0. Return 0 on
> + * success.
> + *
> + */
> +static int send_pipefd(int sockfd, int pipefd)
> +{
> +    struct msghdr msg;
> +    struct iovec iov[1];
> +    ssize_t ret;
> +    char req[1] = { 0x01 };
> +
> +    union {
> +      struct cmsghdr cm;
> +      char control[CMSG_SPACE(sizeof(int))];
> +    } control_un;
> +    struct cmsghdr *cmptr;
> +
> +    msg.msg_control = control_un.control;
> +    msg.msg_controllen = sizeof(control_un.control);
> +
> +    cmptr = CMSG_FIRSTHDR(&msg);
> +    cmptr->cmsg_len = CMSG_LEN(sizeof(int));
> +    cmptr->cmsg_level = SOL_SOCKET;
> +    cmptr->cmsg_type = SCM_RIGHTS;
> +    *((int *) CMSG_DATA(cmptr)) = pipefd;
> +
> +    msg.msg_name = NULL;
> +    msg.msg_namelen = 0;
> +
> +    iov[0].iov_base = req;
> +    iov[0].iov_len = sizeof(req);
> +    msg.msg_iov = iov;
> +    msg.msg_iovlen = 1;
> +
> +    ret = sendmsg(sockfd, &msg, 0);
> +    if (ret <= 0) {
> +        DPRINTF("sendmsg error: %s\n", strerror(errno));
> +    }
> +
> +    return ret;
> +}

Just a reminder about my comments from previous posting. This is
introducing a 3rd private function for sending FDs. The existing
code should be refactored into qemu-socket.{c,h} and shared.

Daniel
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