On Tue, Feb 28, 2017 at 2:40 PM, Eric Dumazet <eric.duma...@gmail.com> wrote: > On Tue, 2017-02-28 at 14:25 -0800, Andy Lutomirski wrote: >> On Tue, Feb 28, 2017 at 1:47 PM, Eric Dumazet <eric.duma...@gmail.com> wrote: >> > On Tue, 2017-02-28 at 13:09 -0800, Andy Lutomirski wrote: >> > >> >> Does this mean that a user program that does a zerocopy send can cause >> >> a retransmitted segment to contain different data than the original >> >> segment? If so, is that okay? >> > >> > Same remark applies to sendfile() already >> >> True. >> >> >, or other zero copy modes >> > (vmsplice() + splice() ) >> >> I hate vmsplice(). I thought I remembered it being essentially >> disabled at some point due to security problems. > > Right, zero copy is hard ;) > > vmsplice() is not disabled in current kernels, unless I missed > something. >
I think you're right. That being said, from the man page: The user pages are a gift to the kernel. The application may not modify this memory ever, otherwise the page cache and on-disk data may differ. This is just not okay IMO.
