[9fans] sendfile interface

["Roman V. Shaposhnick" <vugluskr@unicorn.math.spbu.ru>]

While studying how Linux implements sendfile(2), I couldn't help
but notice, that it is yet another hack a'la mmap. "There must
be a better way to do that" I though at the moment.

Now, I imagine, that for Plan9 there should be no problem telling
kernel that one Chan should server as an "alias", or proxy if you
will, for another one. By doing that, it should be possible to
eliminate the whole "copy to userland buffer; copy back to kernel"
routine and it could be even possible to utilize hardware
scattered-write. How easy it will be for network connections ? Or may
be I'm stretching my imagination too far, and there's no really
a better way to do it. Please comment.

Thanks,
Roman.