Some immediate thoughts after glancing through this: > --- Use cases --- > > The goal of this series is to add two new standard-ish places > in the transmit path: > > 1. Right before the packet is transmitted (with access to TX > descriptors) > 2. Right after the packet is actually transmitted and we've received the > completion (again, with access to TX completion descriptors) > > Accessing TX descriptors unlocks the following use-cases: > > - Setting device hints at TX: XDP/AF_XDP might use these new hooks to > use device offloads. The existing case implements TX timestamp. > - Observability: global per-netdev hooks can be used for tracing > the packets and exploring completion descriptors for all sorts of > device errors. > > Accessing TX descriptors also means that the hooks have to be called > from the drivers. > > The hooks are a light-weight alternative to XDP at egress and currently > don't provide any packet modification abilities. However, eventually, > can expose new kfuncs to operate on the packet (or, rather, the actual > descriptors; for performance sake). dynptr? > --- UAPI --- > > The hooks are implemented in a HID-BPF style. Meaning they don't > expose any UAPI and are implemented as tracing programs that call > a bunch of kfuncs. The attach/detach operation happen via BPF syscall > programs. The series expands device-bound infrastructure to tracing > programs. Not a fan of the "attach from BPF syscall program" thing. These are part of the XDP data path API, and I think we should expose them as proper bpf_link attachments from userspace with introspection etc. But I guess the bpf_mprog thing will give us that? > --- skb vs xdp --- > > The hooks operate on a new light-weight devtx_frame which contains: > - data > - len > - sinfo > > This should allow us to have a unified (from BPF POW) place at TX > and not be super-taxing (we need to copy 2 pointers + len to the stack > for each invocation). Not sure what I think about this one. At the very least I think we should expose xdp->data_meta as well. I'm not sure what the use case for accessing skbs is? If that *is* indeed useful, probably there will also end up being a use case for accessing the full skb? > --- Multiprog attachment --- > > Currently, attach/detach don't expose links and don't support multiple > programs. I'm planning to use Daniel's bpf_mprog once it lands. > > --- TODO --- > > Things that I'm planning to do for the non-RFC series: > - have some real device support to verify xdp_hw_metadata works Would be good to see some performance numbers as well :) > - freplace > - Documentation/networking/xdp-rx-metadata.rst - like documentation > > --- CC --- > > CC'ing people only on the cover letter. Hopefully can find the rest via > lore. Well, I found it there, even though I was apparently left off the Cc list :( -Toke
