On Tue, Mar 26, 2019 at 09:45:29AM -0700, Stanislav Fomichev wrote: > On 03/25, Alexei Starovoitov wrote: > > On Sat, Mar 23, 2019 at 09:05:31AM -0700, Stanislav Fomichev wrote: > > > On 03/22, Alexei Starovoitov wrote: > > > > On Fri, Mar 22, 2019 at 06:19:57PM -0700, Stanislav Fomichev wrote: > > > > > Are we ok with breaking api in this case? I'm all in on removing this > > > > > extra information. We can always put it back if somebody complains (and > > > > > manually parse in eth_get_headlen case). > > > > > > > > Fine. That seems to be the only way forward to clean it all up. > > > > Could you submit patch 1 to bpf tree disallowing vlan fields? > > > > Patch 3 looks like candidate as well? > > > SGTM, will do. Let me also spend some time and do a simple test for > > > the vlan case, to make sure I didn't miss something important. > > > One question here though: would I need to wait for bpf and bpf-next > > > to re-merge to continues the series? Or we can cherry-pick those > > > patches to bpf-next as well (and git will work it out during the > > > merge)? > > > > > > > > We can still have protocol, because in both skb/skb-less cases we have > > > > > it. > > > > > > > > proto can work in both cases, but is it needed ? Does program benefit from it? > > > > The kernel side burns extra bytes by copying it and extra branches to handle it. > > > > May be drop it as well? > > > I feel like the program benefits from it, there is no need to go back and > > > re-parse that (and in the skb case, this data is already pulled). I was > > > also thinking about re-purposing flow_keys->n_proto for that (instead > > > of skb->protocol), so it functions as input and output, maybe that's a > > > more clear way to do it. > > > > Are you saying that skb-less and skb flow dissector progs are looking > > at different positions into the packet ? > No, sorry for confusion, they are both called to parse (optional) L2-vlan > and L3+ headers. However, with-skb case can be called with l2-vlan > parsed (post RFS) or with l2-vlan unparsed (RFS). The vlan is pulled in > __netif_receive_skb_core, but we can still invoke flow dissector prior to > that when doing RFS (get_rps_cpu). > > That's why have this 'if skb->vlan_present' check in the bpf_flow.c program > (and then also manually test for ETH_P_8021Q/ETH_P_8021AD). > > Let me try to post the patches to bpf tree somewhere this week, we > can discuss the API changes there. let's figure out what we disable for bpf/stable first. Sound like skb->protocol isn't helping. prog has to read it from eth header anyway. then let's drop it from ctx? skb->vlan_present also seems to be misleading. For normal processing skb->vlan_present means that there is a vlan hdr in the packet, but for flow dissector is some sort of weird hint whether skb-based dissector was pre- or post- rfs. I think we need make vlan semantics unambiguous first.
