Hi Jens,

In the "io_uring: add support for IORING_OP_IOCTL" thread I wrote this:

> I could use also use a generic way for an async fd-based syscall.
> I thought about using sendmsg() with special CMSG_ elements, but
> currently it's not possible with IORING_OP_SENDMSG to do an async
> io_kiocb based completion, using msg_iocb.

I just noticed that __sys_sendmsg_sock doesn't allow
msg->msg_control || msg->msg_controllen.

Why is that the case?
I could use that in several places for my smbdirect driver.

Optionally turning on msg_iocb usage would also be great,
I'd use that in combination with MSG_OOB and CMSG_
and this OOB message is not ordered like the typical
sendmsg stream socket flow.

Do you think we can add support for this usecase?

Thanks!
metze