Re: [Qemu-devel] [RFC v2 10/32] vhub: Support sending fds back to qemu

[Marc-André Lureau]

Hi

On Thu, Aug 24, 2017 at 12:27 PM, Dr. David Alan Gilbert (git)
<address@hidden> wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
>
> Allow replies with fds (for postcopy)
>
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  contrib/libvhost-user/libvhost-user.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/contrib/libvhost-user/libvhost-user.c 
> b/contrib/libvhost-user/libvhost-user.c
> index 8bbdf5fb40..47884c0a15 100644
> --- a/contrib/libvhost-user/libvhost-user.c
> +++ b/contrib/libvhost-user/libvhost-user.c
> @@ -213,6 +213,30 @@ vu_message_write(VuDev *dev, int conn_fd, VhostUserMsg 
> *vmsg)
>  {
>      int rc;
>      uint8_t *p = (uint8_t *)vmsg;
> +    char control[CMSG_SPACE(VHOST_MEMORY_MAX_NREGIONS * sizeof(int))] = { };
> +    struct iovec iov = {
> +        .iov_base = (char *)vmsg,
> +        .iov_len = VHOST_USER_HDR_SIZE,
> +    };
> +    struct msghdr msg = {
> +        .msg_iov = &iov,
> +        .msg_iovlen = 1,
> +        .msg_control = control,
> +    };
> +    struct cmsghdr *cmsg;
> +
> +    memset(control, 0, sizeof(control));
> +    if (vmsg->fds) {

This is going to be always true, right? Check vmsg->fd_num > 0 instead?

I would also add check or assert(vmsg->fd_num <= VHOST_MEMORY_MAX_NREGIONS)

> +        size_t fdsize = vmsg->fd_num * sizeof(int);
> +        msg.msg_controllen = CMSG_SPACE(fdsize);
> +        cmsg = CMSG_FIRSTHDR(&msg);
> +        cmsg->cmsg_len = CMSG_LEN(fdsize);
> +        cmsg->cmsg_level = SOL_SOCKET;
> +        cmsg->cmsg_type = SCM_RIGHTS;
> +        memcpy(CMSG_DATA(cmsg), vmsg->fds, fdsize);
> +    } else {
> +        msg.msg_controllen = 0;
> +    }
>
>      /* Set the version in the flags when sending the reply */
>      vmsg->flags &= ~VHOST_USER_VERSION_MASK;
> @@ -220,7 +244,7 @@ vu_message_write(VuDev *dev, int conn_fd, VhostUserMsg 
> *vmsg)
>      vmsg->flags |= VHOST_USER_REPLY_MASK;
>
>      do {
> -        rc = write(conn_fd, p, VHOST_USER_HDR_SIZE);
> +        rc = sendmsg(conn_fd, &msg, 0);
>      } while (rc < 0 && (errno == EINTR || errno == EAGAIN));
>
>      do {
> @@ -313,6 +337,7 @@ vu_get_features_exec(VuDev *dev, VhostUserMsg *vmsg)
>      }
>
>      vmsg->size = sizeof(vmsg->payload.u64);
> +    vmsg->fd_num = 0;
>
>      DPRINT("Sending back to guest u64: 0x%016"PRIx64"\n", vmsg->payload.u64);
>
> @@ -454,6 +479,7 @@ vu_set_log_base_exec(VuDev *dev, VhostUserMsg *vmsg)
>      dev->log_size = log_mmap_size;
>
>      vmsg->size = sizeof(vmsg->payload.u64);
> +    vmsg->fd_num = 0;
>
>      return true;
>  }
> @@ -698,6 +724,7 @@ vu_get_protocol_features_exec(VuDev *dev, VhostUserMsg 
> *vmsg)
>
>      vmsg->payload.u64 = features;
>      vmsg->size = sizeof(vmsg->payload.u64);
> +    vmsg->fd_num = 0;
>
>      return true;
>  }
> --
> 2.13.5
>
>

other than that
Reviewed-by: Marc-André Lureau <address@hidden>



-- 
Marc-André Lureau