On Sun, 17 Jun 2018 18:07:02 -0700 Zvi Effron <zeffron@xxxxxxxxxxxxx> wrote: > Hi XDPeople! > > In /include/uapi/linux/bpf.h, (in 4.18-rc1) the comment describing > bpf_perf_event_output says: > > /* > * Note that this helper is not restricted to tracing use cases > * and can be used with programs attached to TC or XDP as well, > * where it allows for passing data to user space listeners. Data > * can be: > * > * * Only custom structs, > * * Only the packet payload, or > * * A combination of both. > */ > > This seems to imply that for both TC and XDP, the packet can be used > for passing data. When I try this, the verifier rejects the program > with "helper access to the packet is not allowed". Looking through the > kernel it doesn't look like bpf_perf_output_event has been tagged with > the appropriate metadata to allow it to access the packet structure, > either for TC or for XDP. Neither bpf_skb_event_output_proto nor > bpf_xdp_event_output_proto have pkt_acess set to true. Is the > documentation incorrect, should that metadata be updated to allow > packet access, or is there something I'm missing? Toke (Cc'ed) recently posted a samples/bpf/ program to the kernel that implement this (but it didn't reach the merge window). Thus, I assume that this works... http://lkml.kernel.org/r/152830792912.21161.3609946361971472545.stgit@alrua-kau -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
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