> 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 :) > > >> 2. UI consistency; suddenly, the user needs to know which kind of > >> frames to expect, and XDP program reuse becomes more difficult. This > >> may be unavoidable given the nature of XDP, but some thought needs to > >> go into this. Especially since we wouldn't necessarily be consistent > >> between WiFi drivers (there are fullmac devices that remove 802.11 > >> headers before sending up the frame, right?). > >> > > > > Right, maybe can we have some kind of 'wifi' bpf helpers? > > Yeah, I guess we would at least need helpers to update any internal > state in mac80211 (such as BAW), or BPF programs wouldn't even be able > to drop packets without messing things up... > Correct. Regards, Lorenzo > -Toke
