From: "Mintz, Yuval" <yuval.mi...@cavium.com> Date: Mon, 31 Oct 2016 18:31:30 +0000
> So I've [finally] started looking into implementing XDP > for qede, and there's one thing I feel like I'm missing in > regard to XDP_TX - what's the guarantee/requirement > that the bpf program isn't going to transmute some fields > of the rx packet in a way that would prevent the forwarding? > > E.g., can a BPF change the TCP payload of an incoming packet > without correcting its TCP checksum, and then expect the > driver to transmit it [via XDP_TX]? If not, how is this enforced [if at all]? > > [Looked at samples/bpf/xdp2_kern.c which manipulates the > UDP header; so I'm not certain what prevents it from doing > the same when checksum modifications would be required] My understanding is that the eBPF program would be responsible for updating the checksum if it mangles the packet in such a way that such a fixup would be required.
