From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58684) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VnoX4-0007B6-Ge for qemu-devel@nongnu.org; Tue, 03 Dec 2013 06:52:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VnoWw-0007oa-29 for qemu-devel@nongnu.org; Tue, 03 Dec 2013 06:52:50 -0500 Received: from mail-qc0-x22e.google.com ([2607:f8b0:400d:c01::22e]:65391) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VnoWv-0007nu-TE for qemu-devel@nongnu.org; Tue, 03 Dec 2013 06:52:41 -0500 Received: by mail-qc0-f174.google.com with SMTP id n7so612539qcx.33 for ; Tue, 03 Dec 2013 03:52:41 -0800 (PST) Sender: Paolo Bonzini Message-ID: <529DC602.6000702@redhat.com> Date: Tue, 03 Dec 2013 12:52:34 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1385975957-22941-1-git-send-email-lilei@linux.vnet.ibm.com> <1385975957-22941-7-git-send-email-lilei@linux.vnet.ibm.com> <20131202093341.GA1980@redhat.com> <529DBE4C.8060205@linux.vnet.ibm.com> In-Reply-To: <529DBE4C.8060205@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 06/17] migration-local: add send_pipefd() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Lei Li Cc: aarcange@redhat.com, quintela@redhat.com, qemu-devel@nongnu.org, mrhines@linux.vnet.ibm.com, aliguori@amazon.com, lagarcia@br.ibm.com, rcj@linux.vnet.ibm.com Il 03/12/2013 12:19, Lei Li ha scritto: > On 12/02/2013 05:33 PM, Daniel P. Berrange wrote: >> 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 >>> --- >>> 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. > > Hi Daniel, > > Yes, I remembered your suggestion. As my reply in the previous version, > I'll make this refactoring in a separate thread. There are some differences > between these private functions (like data type and length of bytes > transmitted), may need a little time to get the common method settle down, > and would be better to do some test to make sure there is no impact on > them. You would have to implement it in such a way that the buffer is specified in the function, for example: ssize_t qemu_send_with_fd(int sockfd, int passed_fd, const void *buf, size_t len); ssize_t qemu_recv_with_fd(int sockfd, int *passed_fd, void *buf, size_t len); The functions can go in util/ (I think not in qemu-socket.c, a new file is preferrable). I don't think it's particularly important, but it's definitely welcome. Paolo