On 06/27/2017 10:45 PM, Dan Siemon wrote:
[This isn't strictly an XDP question, I'm using cls_bpf but I don't know of a better place to ask] Is there a way to calculate a hash of a struct or other data from within an eBPF program? I need to build a classifier that can hash a flow encapsulated in protocols like PPPoE or GTP-U. Basically like cls_flow's use of jhash2 but at a different offset. I looked at the helpers in bpf.h but don't see anything helpful there.
Why no implement it inside the BPF prog like it's done here [1] (the example is XDP but cls_bpf should work just as well)? There's also a bpf_set_hash(struct __sk_buff *skb, u32 hash) helper (net-next) for cls_bpf, where you can then use the jhash result and set it as skb->hash. [1] http://lingrok.org/xref/linux-net-next/tools/testing/selftests/bpf/test_l4lb.c#26
Thanks.
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