> > So I've [finally] started looking into implementing XDP for qede, and > > there's one thing I feel like I'm missing in regard to XDP_TX - what's > > the guarantee/requirement that the bpf program isn't going to > > transmute some fields of the rx packet in a way that would prevent the > > forwarding? > > > I think there are really two separate questions you're probably asking. 1) Can > XDP modify a packet in such a way that it won't be forwarded by the driver > when > XDP_TX is returned, ie. driver would drop packet 2) Does anything prevent the > BPF program from modifying the packet such that it becomes malformed (bad > checksum, mangled headers, etc.). > > I believe the answer to #1 is "no", the XDP interface assumes raw packets. If > program returns XDP_TX then the driver will forward the raw packet without any > further consideration. > > The answer to #2 is "no", there is no check that packet produced is sensible. > We > assume that the user setting the XDP program knows what they are doing.
O.k., thanks - so I can safely assume forwarding wouldn't require any HW offloading. BTW, are we considering some offload where the eBPF would return a set of changes [based on some pre-set capabilities set by driver] done on buffer and let the HW offload those? I understand end goal is eBPF hw-offloading, but seems like there are a lot of existing offload facilities that might be leveraged.
