On 5/2/18 5:13 AM, Jesper Dangaard Brouer wrote:

On Sun, 29 Apr 2018 11:07:52 -0700 David Ahern [off-list ref] wrote:

quoted

+	/* verify egress index has xdp support */
+	// TO-DO bpf_map_lookup_elem(&tx_port, &key) fails with
+	//       cannot pass map_type 14 into func bpf_map_lookup_elem#1:

I just want to point out that I/we are aware of this "usability"
problem with the sample program, but I don't want to block the FIB
helper going upstream, we can fix this problem later.

The problem is that if you load this bpf/xdp prog, then all incoming
traffic (on that interface), will be forward using XDP, regardless
whether the egress ifindex support XDP or not.  And if not supported,
then packets are dropped hard (only detectable via tracepoints).

If the bpf prog could tell/know that the egress ifindex doesn't
support XDP xmit, then it could simply return XDP_PASS to fallback to
the normal network stack.

That's what the above lookup is intending but DEVMAP type does not
handle lookups from xdp programs. Any chance of fixing that?