[Spice-devel] [PATCH spice 5/9] reds-stream: add send_msgfd()

[Marc-André Lureau]

Hi

----- Original Message -----
> > 
> > From: Marc-André Lureau <mlureau at redhat.com>
> > 
> > A new function to send fd with unix socket anciliary data.
> > 
> > Signed-off-by: Marc-André Lureau <marcandre.lureau at gmail.com>
> > ---
> >  server/reds-stream.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> >  server/reds-stream.h |  1 +
> >  2 files changed, 43 insertions(+)
> > 
> > diff --git a/server/reds-stream.c b/server/reds-stream.c
> > index d87cb23..4829b43 100644
> > --- a/server/reds-stream.c
> > +++ b/server/reds-stream.c
> > @@ -28,6 +28,7 @@
> >  #include <netdb.h>
> >  #include <unistd.h>
> >  #include <sys/socket.h>
> > +#include <fcntl.h>
> >  
> >  #include <glib.h>
> >  
> > @@ -254,6 +255,47 @@ int reds_stream_is_plain_unix(const RedsStream *s)
> >  
> >  }
> >  
> > +int reds_stream_send_msgfd(RedsStream *stream, int fd)
> > +{
> > +    struct msghdr msgh;
> > +    struct iovec iov;
> > +    int r;
> > +
> > +    size_t fd_size = 1 * sizeof(int);
> 
> const here?

Yeah, I am not that strict about internal variables. Sure why not?

> 
> > +    char control[CMSG_SPACE(fd_size)];
> 
> This would be better to be an union of data and struct cmsghdr, something
> like
> 
> union {
>    struct cmsghdr hdr;
>    char data[CMSG_SPACE(fd_size)];
> } control;
> 
> (of course this needs some other changes in the code).

Ok

> 
> > +    struct cmsghdr *cmsg;
> > +
> > +    spice_return_val_if_fail(reds_stream_is_plain_unix(stream), -1);
> > +
> > +    memset(&msgh, 0, sizeof(msgh));
> > +    memset(control, 0, sizeof(control));
> > +    /* set the payload */
> > +    iov.iov_base = (char*)"@";
> 
> is the cast required?

yes, "assignment discards 'const' qualifier from pointer target type"

> 
> > +    iov.iov_len = 1;
> > +
> > +    if (fd != -1) {
> > +        msgh.msg_iovlen = 1;
> > +        msgh.msg_iov = &iov;
> > +        msgh.msg_control = control;
> > +        msgh.msg_controllen = sizeof(control);
> > +
> > +        cmsg = CMSG_FIRSTHDR(&msgh);
> > +
> > +        cmsg->cmsg_len = CMSG_LEN(fd_size);
> > +        cmsg->cmsg_level = SOL_SOCKET;
> > +        cmsg->cmsg_type = SCM_RIGHTS;
> > +        memcpy(CMSG_DATA(cmsg), &fd, fd_size);
> > +    } else {
> > +        msgh.msg_iovlen = 0;
> 
> So you don't send nothing if no file descriptor is passes?
> How do you handle the read on the other end?

The read of one byte takes place, but no fd get through. The client should not always expect a fd with the msg, depending on the msg. For SPICE_MSG_DISPLAY_GL_SCANOUT_UNIX, it's possible to send no fd to "unset" the current scanout.

> > +    }
> > +
> > +    do {
> > +        r = sendmsg(stream->socket, &msgh, 0);
> 
> MSG_NOSIGNAL as flag?

Why not? does that really change something here?

> 
> > +    } while (r < 0 && (errno == EINTR || errno == EAGAIN));
> > +
> > +    return r;
> > +}
> > +
> >  ssize_t reds_stream_writev(RedsStream *s, const struct iovec *iov, int
> >  iovcnt)
> >  {
> >      int i;
> > diff --git a/server/reds-stream.h b/server/reds-stream.h
> > index 9e53b22..72e5dd1 100644
> > --- a/server/reds-stream.h
> > +++ b/server/reds-stream.h
> > @@ -74,6 +74,7 @@ int reds_stream_enable_ssl(RedsStream *stream, SSL_CTX
> > *ctx);
> >  void reds_stream_set_info_flag(RedsStream *stream, unsigned int flag);
> >  int reds_stream_get_family(const RedsStream *stream);
> >  int reds_stream_is_plain_unix(const RedsStream *stream);
> > +int reds_stream_send_msgfd(RedsStream *stream, int fd);
> >  
> >  typedef enum {
> >      REDS_SASL_ERROR_OK,


thanks for the review