> On 16 May 2017, at 10:55, Tomas Brännström <tomas.a.brannst...@tieto.com>
> wrote:
>
> Hi
> I'm struggling a bit to understand how VPP processes the node graph. If we
> take the sample plugin for example, it registers itself to the "device-input"
> arc. Then it is run after "af-packet-input" among others. But looking at the
> af-packet-input-node, it has the following "next" nodes in the graph:
>
> af-packet-input ip4-input-no-checksum [0]
> ip4-input [1]
> ip6-input [2]
> mpls-input [3]
> ethernet-input [4]
> error-drop [5]
> sample [6]
>
> But how does af-packet-input decide which of these nodes to run? Is it simply
> in descending order so since sample is at the bottom, it will be run before
> ethernet-input etc?
Sample plugin is using feature arcs. It registers himself for “device-input”
arc and when you enable it for specific interface, af-packet-input node will
start sending packets to the first node on the arc.
Key function in af-packet-input node code is (in
src/vnet/devices/af_packet/node.c)
/* redirect if feature path enabled */
vnet_feature_start_device_input_x1 (apif->sw_if_index, &next0, b0);
It basically alters next0 if feature arc is enabled for specific sw_if_index ….
>
> Also, is there a document somewhere that explains exactly how a node is input
> into the graph? I think I understand how it works on some level, but I'm not
> 100% clear what for example VPP actually does with ".arc_name",
> ".runs_before" and so on.
Everything we have is public (including youtube recordings and wiki).
Feel free to ask here if you have specific questions...
_______________________________________________
vpp-dev mailing list
vpp-dev@lists.fd.io
https://lists.fd.io/mailman/listinfo/vpp-dev
