On Mon, 26 Jun 2023 22:14:41 +0100 David Howells wrote:
> Do you know if ->sendmsg() might alter the msghdr struct it is passed as an
> argument? Certainly it can alter msg_iter, but can it also modify,
> say, msg_flags?
I'm not aware of a precedent either way.
Eric or Paolo would know better than me, tho.
On Mon, 2023-06-26 at 14:22 -0700, Jakub Kicinski wrote:
> On Mon, 26 Jun 2023 22:14:41 +0100 David Howells wrote:
> > Do you know if ->sendmsg() might alter the msghdr struct it is passed as an
> > argument? Certainly it can alter msg_iter, but can it also modify,
> > say, msg_flags?
>
> I'm not aware of a precedent either way.
> Eric or Paolo would know better than me, tho.
udp_sendmsg() can set the MSG_TRUNC bit in msg->msg_flags, so I guess
that kind of actions are sort of allowed. Still, AFAICS, the kernel
based msghdr is not copied back to the user-space, so such change
should be almost a no-op in practice.
@David: which would be the end goal for such action?
Cheers,
Paolo