Re: [RFC PATCH v2 04/48] net: Declare MSG_SPLICE_PAGES internal sendmsg() flag

Willem de Bruijn
2023-03-30T17:52:08Z

David Howells wrote:
> Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote:
>
> > No need to modify __sys_sendmmsg explicitly, as it ends up calling
> > __sys_sendmsg?
> >
> > Also, sendpage does this flags masking in the internal sock_FUNC
> > helpers rather than __sys_FUNC. Might be preferable.
>
> I was wondering whether other flags, such as MSG_BATCH should be added to the
> list. Is it bad if userspace sets that in sendmsg()? AF_KCM, at least, looks
> at it.

That flag was added exactly for AF_KCM. A process that explicitly
sets it might experience bad behavior (increased latency), but
there are no legacy AF_KCM applications that precede the flag.