On Tue, 30 Jul 2019 16:17:56 -0700, Alexei Starovoitov wrote:

On Tue, Jul 30, 2019 at 03:59:15PM -0700, Jakub Kicinski wrote:

quoted

On Wed, 31 Jul 2019 03:48:19 +0900, Daniel T. Lee wrote:  

quoted

Currently, bpftool net only supports dumping progs loaded on the
interface. To load XDP prog on interface, user must use other tool
(eg. iproute2). By this patch, with `bpftool net (un)load`, user can
(un)load XDP prog on interface.  

I don't understand why using another tool is a bad thing :(
What happened to the Unix philosophy?

I remain opposed to duplicating iproute2's functionality under 
bpftool net :( The way to attach bpf programs in the networking
subsystem is through the iproute2 commends - ip and tc.. 

It seems easy enough to add a feature to bpftool but from 
a perspective of someone adding a new feature to the kernel, 
and wanting to update user space components it's quite painful :(

So could you describe to me in more detail why this is a good idea?
Perhaps others can chime in?  

I don't think it has anything to do with 'unix philosophy'.
Here the proposal to teach bpftool to attach xdp progs.
I see nothing wrong with that.

Nothing meaning you disagree it's duplicated effort and unnecessary 
LoC the community has to maintain, review, test..?

Another reason is iproute2 is still far away from adopting libbpf.
So all the latest goodness like BTF, introspection, etc will not
be available to iproute2 users for some time.

Duplicating the same features in bpftool will only diminish the
incentive for moving iproute2 to libbpf. And for folks who deal
with a wide variety of customers, often novices maintaining two
ways of doing the same thing is a hassle :(

Even when iproute2 is ready it would be convenient for folks like me
(who need to debug stuff in production) to remember cmd line of
bpftool only to introspect the server. Debugging often includes
detaching/attaching progs. Not only doing 'bpftool p s'.

Let's just put the two commands next to each other:

       ip link set xdp $PROG dev $DEV

bpftool net attach xdp $PROG dev $DEV

Are they that different?

If bpftool was taught to do equivalent of 'ip link' that would be
very different story and I would be opposed to that.

Yes, that'd be pretty clear cut, only the XDP stuff is a bit more 
of a judgement call.