Hi Jason, On Tue, Mar 9, 2021 at 4:57 PM Jason Wang <jasow...@redhat.com> wrote: > > > On 2021/3/9 4:35 下午, Bin Meng wrote: > > Hi Jason, > > > > On Tue, Mar 9, 2021 at 4:23 PM Jason Wang <jasow...@redhat.com> wrote: > >> > >> On 2021/3/8 6:22 下午, Peter Maydell wrote: > >>> On Mon, 8 Mar 2021 at 03:48, Jason Wang <jasow...@redhat.com> wrote: > >>>> Do we need to care about other type of networking backends? E.g socket. > >>>> > >>>> Or at least we should keep the padding logic if we can't audit all of > >>>> the backends. > >>> I think the key thing we need to do here is make a decision > >>> and be clear about what we're doing. There are three options > >>> I can see: > >>> > >>> (1) we say that the net API demands that backends pad > >>> packets they emit to the minimum ethernet frame length > >>> unless they specifically are intending to emit a short frame, > >>> and we fix any backends that don't comply (or equivalently, > >>> add support in the core code for a backend to mark itself > >>> as "I don't pad; please do it for me"). > >>> > >>> (2) we say that the networking subsystem doesn't support > >>> short packets, and just have the common code always enforce > >>> padding short frames to the minimum length somewhere between > >>> when it receives a packet from a backend and passes it to > >>> a NIC model. > >>> > >>> (3) we say that it's the job of the NIC models to pad > >>> short frames as they see them coming in. > >>> > >>> I think (3) is pretty clearly the worst of these, since it > >>> requires every NIC model to handle it; it has no advantages > >>> over (2) that I can see. I don't have a strong take on whether > >>> we'd rather have (1) or (2): it's a tradeoff between whether > >>> we support modelling of short frames vs simplicity of code. > >>> I'd just like us to be clear about what point or points in > >>> the code have the responsibility for padding short frames. > >> > >> I'm not sure how much value we can gain from (1). So (2) looks better to > >> me. > >> > >> Bin or Philippe, want to send a new version? > >> > > I think this series does what (2) asks for. Or am I missing anything? > > > It only did the padding for user/TAP.
Ah, so we want this:
