On Wed, Mar 09, 2011 at 06:45:45PM -0700, Eric Blake wrote:
> Currently, the hook function in virFileOperation is extremely limited:
> it must be async-signal-safe, and cannot modify any memory in the
> parent process. It is much handier to return a valid fd and operate
> on it in the parent than to deal with hook restrictions.
>
> * src/util/util.h (VIR_FILE_OP_RETURN_FD): New flag.
> * src/util/util.c (virFileOperationNoFork, virFileOperation):
> Honor new flag.
> ---
> src/util/util.c | 139 ++++++++++++++++++++++++++++++++++++++++++++++++------
> src/util/util.h | 4 +-
> 2 files changed, 126 insertions(+), 17 deletions(-)
ACK,
> + memset(&msg, 0, sizeof(msg));
> + iov.iov_base = &dummy;
> + iov.iov_len = 1;
> + msg.msg_iov = &iov;
> + msg.msg_iovlen = 1;
> + msg.msg_control = buf;
> + msg.msg_controllen = sizeof(buf);
> + cmsg = CMSG_FIRSTHDR(&msg);
> + cmsg->cmsg_level = SOL_SOCKET;
> + cmsg->cmsg_type = SCM_RIGHTS;
> + cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
> + }
....
> + if (flags & VIR_FILE_OP_RETURN_FD) {
> + VIR_FORCE_CLOSE(pair[1]);
> +
> + do {
> + ret = recvmsg(pair[0], &msg, 0);
> + } while (ret < 0 && errno == EINTR);
> +
> + if (ret < 0) {
> + ret = -errno;
> + VIR_FORCE_CLOSE(pair[0]);
> + while ((waitret = waitpid(pid, NULL, 0) == -1)
> + && (errno == EINTR));
> + goto parenterror;
> + }
> + VIR_FORCE_CLOSE(pair[0]);
> +
> + /* See if fd was transferred. */
> + cmsg = CMSG_FIRSTHDR(&msg);
> + if (cmsg && cmsg->cmsg_len == CMSG_LEN(sizeof(fd)) &&
> + cmsg->cmsg_level == SOL_SOCKET &&
> + cmsg->cmsg_type == SCM_RIGHTS) {
> + memcpy(&fd, CMSG_DATA(cmsg), sizeof(fd));
> + }
Also might be nice to create two helper methods for this
int virFileHandleSendToSocket(int unixfd, int sendfd);
int virFileHandleRecvFromSocket(int unixfd);
which we can also use in the monitor code that does the
same thing
Daniel
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