Re: [Qemu-devel] [PATCH v4 1/7] qemu-char: Add MSG_CMSG_CLOEXEC flag to recvmsg

[Corey Bryant]

On 06/25/2012 05:16 AM, Stefan Hajnoczi wrote:
> On Fri, Jun 22, 2012 at 01:31:17PM -0600, Eric Blake wrote:
> > On 06/22/2012 12:36 PM, Corey Bryant wrote:
> > > This sets the close-on-exec flag for the file descriptor received
> > > via SCM_RIGHTS.
> > >
> > > Signed-off-by: Corey Bryant <address@hidden>
> > > ---
> > > v4
> > >   -This patch is new in v4 (address@hidden)
> > >
> > >   qemu-char.c |    2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/qemu-char.c b/qemu-char.c
> > > index c2aaaee..f890113 100644
> > > --- a/qemu-char.c
> > > +++ b/qemu-char.c
> > > @@ -2263,7 +2263,7 @@ static ssize_t tcp_chr_recv(CharDriverState *chr, char 
> > > *buf, size_t len)
> > >       msg.msg_control = &msg_control;
> > >       msg.msg_controllen = sizeof(msg_control);
> > >
> > > -    ret = recvmsg(s->fd, &msg, 0);
> > > +    ret = recvmsg(s->fd, &msg, MSG_CMSG_CLOEXEC);
> >
> > MSG_CMSG_CLOEXEC is not (yet) in POSIX (although it has been proposed
> > for addition); therefore, at the moment, it only exists on Linux and
> > Cygwin.  Does this need to have conditional code to allow compilation on
> > BSD, such as:
> >
> > #ifndef MSG_CMSG_CLOEXEC
> > # define MSG_CMSG_CLOEXEC 0
> > #endif
> >
> > as well as fallback code that sets FD_CLOEXEC manually via fcntl() when
> > MSG_CMSG_CLOEXEC is missing?
>
> Good point.  I think the answer is yes.  Just like qemu_open() we can
> wrap "recvmsg(2) with fd" so that platforms with MSG_CMSG_CLOEXEC use
> that flag and other platforms use qemu_set_cloexec().
>
> Stefan

Thanks for pointing this out.  I'll make the updates in v5.

--
Regards,
Corey