sosend() and mbuf

[Maslan]

> Is it possible to call kern_open() from within a kernel thread anyway?
I think yes, It worked on the parent thread before creating a new kthread.
See OpenKETA source, its using the same approach.
> kern_open() depends on a file descriptor table, right?
Yes, it returns a fd in the curthread->td_retval[0], which i should
use within the same thread to deal with this file.