[libvirt] [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 <coreyb at linux.vnet.ibm.com>
>>> ---
>>> v4
>>>   -This patch is new in v4 (eblake at redhat.com)
>>>
>>>   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