On Thu, 2017-04-20 at 16:46 +0200, Daniel Borkmann wrote: > > Hmm. I don't see what "somewhere else" I could possibly have > > though, given that I want the (kernel-side) context to be "struct > > sk_buff *" to allow the skb helpers? > > I have not enough context on the wireless side, perhaps could be > somewhere under skb->dev->ieee80211_ptr or so, iff suitable.
I don't think I even have skb->dev assigned at this point :) > But > it also really doesn't matter much since this is all transparently > handled in the kernel, meaning these kind of rewrites can still be > changed at a later point in time, f.e. if it's only 'u64 boottime_ns' > right now, that could live directly in the cb[] w/o extra pointer, > and should that grow to more members, then it could be moved behind > a pointer later on and it still works as-is from the program point > of view. Well, there are 48 bytes in the cb already, so doing this would mean moving two pointer-sized things out, but yeah - as long as we don't add everything right now we can keep those things that are available to BPF in the cb and move something else out. As long as what I described there with the indirect load works, I'm fine with this, and I can even do data_end pretty easily then. johannes
