Re: [PATCH RFC net-next v1 5/5] net: devmem: Implement TX path

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

> > > +struct net_devmem_dmabuf_binding *
> > > +net_devmem_get_sockc_binding(struct sock *sk, struct sockcm_cookie *sockc)
> > > +{
> > > +     struct net_devmem_dmabuf_binding *binding;
> > > +     int err = 0;
> > > +
> > > +     binding = net_devmem_lookup_dmabuf(sockc->dmabuf_id);
> >
> > This lookup is from global xarray net_devmem_dmabuf_bindings.
> >
> > Is there a check that the socket is sending out through the device
> > to which this dmabuf was bound with netlink? Should there be?
> > (e.g., SO_BINDTODEVICE).
> >
> 
> Yes, I think it may be an issue if the user triggers a send from a
> different netdevice, because indeed when we bind a dmabuf we bind it
> to a specific netdevice.
> 
> One option is as you say to require TX sockets to be bound and to
> check that we're bound to the correct netdev. I also wonder if I can
> make this work without SO_BINDTODEVICE, by querying the netdev the
> sock is currently trying to send out on and doing a check in the
> tcp_sendmsg. I'm not sure if this is possible but I'll give it a look.

I was a bit quick on mentioning SO_BINDTODEVICE. Agreed that it is
vastly preferable to not require that, but infer the device from
the connected TCP sock.