On 03/26, Alexei Starovoitov wrote: > On Tue, Mar 26, 2019 at 10:52 AM Willem de Bruijn > <willemdebruijn.ker...@gmail.com> wrote: > > The BPF flow dissector should work the same. It is fine to pass the > > data including ethernet header, but parsing can start at nhoff with > > proto explicitly passed. > > > > We should not assume Ethernet link layer. > > then skb-less dissector has to be different program type > because semantics are different. The semantics are the same as for c-based __skb_flow_dissect. We just need to pass nhoff and proto that has been passed to __skb_flow_dissect to the bpf program. In case of with-skb, take this initial data from skb, like __skb_flow_dissect does (and don't ask BPF program to do it essentially):
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/tree/net/core/flow_dissector.c#n763 I was thinking of passing proto as flow_keys->n_proto and we already pass flow_keys->nhoff, so no need to do anything for it. With that, BPF program doesn't need to look into skb and can parse optional vlan and L3+ headers. The same way __skb_flow_dissect does that.
