Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxx> writes: >> Lorenzo Bianconi <lorenzo.bianconi@xxxxxxxxxx> writes: >> >> >> >> > This series is intended as a playground to start experimenting/developing >> >> >> > with XDP/eBPF over WiFi and collect ideas/concerns about it. >> >> >> > Introduce XDP support to mt76x2e/mt76x0e drivers. Currently supported >> >> >> > actions are: >> >> >> > - XDP_PASS >> >> >> > - XDP_ABORTED >> >> >> > - XDP_DROP >> >> >> > Introduce ndo_bpf mac80211 callback in order to to load a bpf >> >> >> > program into low level driver XDP rx hook. >> >> >> > This series has been tested through a simple bpf program (available here: >> >> >> > https://github.com/LorenzoBianconi/bpf-workspace/tree/master/mt76_xdp_stats) >> >> >> > used to count frame types received by the device. >> >> >> > Possible eBPF use cases could be: >> >> >> > - implement new statistics through bpf maps >> >> >> > - implement fast packet filtering (e.g in monitor mode) >> >> >> > - ... >> >> > >> >> > Hi Kalle, >> >> > >> >> >> >> >> >> This is most likely a stupid question, but why do this in the driver and >> >> >> not in mac80211 so that all drivers could benefit from it? I guess there >> >> >> are reasons for that, I just can't figure that out. >> >> >> >> XDP achieves its speedup by running the eBPF program inside the driver >> >> NAPI loop, before the kernel even touches the data in any other capacity >> >> (and in particular, before it allocates an SKB). Which kinda means the >> >> hook needs to be in the driver... Could be a fallback in mac80211, >> >> though; although we'd have to figure out how that interacts with Generic >> >> XDP. >> >> >> >> > This is an early stage implementation, at this point I would collect >> >> > other people opinions/concerns about using bpf/xdp directly on 802.11 >> >> > frames. >> >> >> >> Thanks for looking into this! >> > >> > Hi Toke, >> > >> >> >> >> I have two concerns with running XDP on 802.11 frames: >> >> >> >> 1. It makes it more difficult to add other XDP actions (such as >> >> REDIRECT), as the XDP program would then have to make sure that the >> >> outer packet headers are removed before, say, redirecting the packet >> >> out of an ethernet interface. Also, if we do add redirect, we would >> >> be bypassing mac80211 entirely; to what extent would that mess up >> >> internal state? >> >> >> > >> > You are right, my assumption here is the logic/complexity is moved to >> > the bpf program that needs to take care of all possible issues that >> > can be introduced. More or less it is the same if a bpf program mess >> > up with TCP segments on a wired connection, isn't it? >> >> No, I guess not; except here it potentially applies to all packets >> (things like BAW tracking), and it is *in addition* to TCP. > > Yes, here it is a little bit harder, but I was meaning that the bpf program > has to be very careful when dropping a packet :) Yeah. What kind of filtering were you thinking you would use this for in the short term? -Toke
