Re: [Qemu-devel] Question on unixsocket-based chardevs and vhost-user

[Felipe Franciosi]

Hi Paolo,

> On 28 Sep 2016, at 17:59, Paolo Bonzini <address@hidden> wrote:
> 
> On 28/09/2016 18:56, Felipe Franciosi wrote:
>> Hi Daniel/Paolo,
>> 
>> 
>> 
>> I have a question regarding this commit:
>> 
>> -------------8<-------------
>> Author:     Daniel P. Berrange <address@hidden>
>> AuthorDate: Tue Jan 19 11:14:29 2016 +0000
>> Commit:     Paolo Bonzini <address@hidden>
>> CommitDate: Tue Jan 26 15:58:11 2016 +0100
>> -------------8<-------------
>> 
>> One of the hunks replace unix_send_msgfds() with io_channel_send_full():
>> 
>> According to the code (qemu-char.c:968), io_channel_send_full() is just
>> ignoring the s->write_msgfds parameter.
> 
> Hmm, no, it's passing it down:
> 
>        ret = qio_channel_writev_full(
>            ioc, &iov, 1,
>            fds, nfds, NULL);
> 
> See the implementation of qio_channel_socket_writev in io/channel-socket.c.

Ah, so my socket has been plumbed with qio_channel_file_writev() for some 
reason. That's definitely ignoring the fds. I'll look into why it's not 
qio_channel_socket_writev().

Thanks!
Felipe

> 
> Thanks,
> 
> Paolo
> 
>> So my question is: when using a chardev implemented by unix sockets, how
>> does one pass file descriptors for vhost-user applications?
>> 
>> I’m actually searching qemu-char.c for “write_msgfds” and scratching my
>> head. There are functions to set it, clear it, etc, but none to send it.