Thanks for the context! I write back to the packet directly (I chain all the checksum updates through a series of bpf_csum_diff() calls and then write back the ultimate value). Since we have a mixed fleet right now, I'm guessing I'm going to need multiple versions of the TC BPF .o binary, since it looks like bpf_skb_net_shrink() EINVAL's on 5.6 with that BPF_F_ADJ_ROOM_NO_CSUM_RESET flag. A small price to pay! Again: many thanks for this; this group is really great. On Tue, Nov 2, 2021 at 5:28 PM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote: > For the update, did you use bpf_csum_update() helper or directly writing into > the pkt? --- Thomas H. Ptacek
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