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    bpf: fix bpf helpers to use skb->mac_header relative offsets · a166151c
    Alexei Starovoitov 提交于
    For the short-term solution, lets fix bpf helper functions to use
    skb->mac_header relative offsets instead of skb->data in order to
    get the same eBPF programs with cls_bpf and act_bpf work on ingress
    and egress qdisc path. We need to ensure that mac_header is set
    before calling into programs. This is effectively the first option
    from below referenced discussion.
    
    More long term solution for LD_ABS|LD_IND instructions will be more
    intrusive but also more beneficial than this, and implemented later
    as it's too risky at this point in time.
    
    I.e., we plan to look into the option of moving skb_pull() out of
    eth_type_trans() and into netif_receive_skb() as has been suggested
    as second option. Meanwhile, this solution ensures ingress can be
    used with eBPF, too, and that we won't run into ABI troubles later.
    For dealing with negative offsets inside eBPF helper functions,
    we've implemented bpf_skb_clone_unwritable() to test for unwriteable
    headers.
    
    Reference: http://thread.gmane.org/gmane.linux.network/359129/focus=359694
    Fixes: 608cd71a ("tc: bpf: generalize pedit action")
    Fixes: 91bc4822 ("tc: bpf: add checksum helpers")
    Signed-off-by: NAlexei Starovoitov <ast@plumgrid.com>
    Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
    Signed-off-by: NDavid S. Miller <davem@davemloft.net>
    a166151c
bpf.h 6.6 KB