>       struct iovec {
>           void *iov_base;
>           size_t iov_len;
> 	 uint32_t flags;
>       };

If you're going to do this, _please_ do a const-poisoning-friendly
version!  Off the cuff, I'd suggest something like

	struct iovec_f {
	  union {
	    void *iovu_base_r;
	    const void *iovu_base_w;
	  } iov_u;
#define iov_base_r iov_u.iovu_base_r
#define iov_base_w iov_u.iovu_base_w
	  ...other members...
	} ;

I'm not sure whether it's worth having volatile-modified versions as
well - I've never wanted them, but that doesn't necessarily mean much.

The incompatability between writev() and const-poisoning is perhaps the
most annoying single thing about writev, in my experience....

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