[libvirt] [PATCH v2 8/8] rpc: pass listen FD to the daemon being started

[Daniel P. Berrange]

On Wed, Jul 16, 2014 at 08:30:02PM +0200, Martin Kletzander wrote:
> - retry:
> -    if (connect(fd, &remoteAddr.data.sa, remoteAddr.len) < 0) {
> -        if ((errno == ECONNREFUSED ||
> -             errno == ENOENT) &&
> -            spawnDaemon && retries < 20) {
> -            VIR_DEBUG("Connection refused for %s, trying to spawn %s",
> -                      path, binary);
> -            if (retries == 0 &&
> -                virNetSocketForkDaemon(binary) < 0)
> -                goto error;
> +    if (spawnDaemon) {
> +        if ((passfd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0) {
> +            virReportSystemError(errno, "%s", _("Failed to create socket"));
> +            goto error;
> +        }
> 
> -            retries++;
> -            usleep(1000 * 100 * retries);
> -            goto retry;
> +        /*
> +         * We cannot do the umask() trick here because that's not
> +         * thread-safe.  fchmod(), however, is not guaranteed to work on
> +         * some BSD favours, but *should* work on Linux before the socket
> +         * is bound.  POSIX says the behaviour of fchmod() called on
> +         * socket is unspecified, though.
> +         */

IIUC, the entire concept of UNIX domain socket permissions is entirely
unspecified not just fchmod().

We could however use umask() here if you use a virFork() to start a
single threaded process. Set umask, create the socket, and then exit,
allowing the parent to continue.

> +        if (fchmod(passfd, 0700) < 0) {
> +            virReportSystemError(errno, "%s",
> +                                 _("Failed to change permissions on socket"));
> +            goto error;
>          }
> 

Regards,
Daniel
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