bpf: add bpf_skb_change_tail helper

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This work adds a bpf_skb_change_tail() helper for tc BPF programs. The
basic idea is to expand or shrink the skb in a controlled manner. The
eBPF program can then rewrite the rest via helpers like bpf_skb_store_bytes(),
bpf_lX_csum_replace() and others rather than passing a raw buffer for
writing here.

bpf_skb_change_tail() is really a slow path helper and intended for
replies with f.e. ICMP control messages. Concept is similar to other
helpers like bpf_skb_change_proto() helper to keep the helper without
protocol specifics and let the BPF program mangle the remaining parts.
A flags field has been added and is reserved for now should we extend
the helper in future.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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This commit is contained in:

Daniel Borkmann 2016-08-18 01:00:39 +02:00 • committed by David S. Miller

parent 45c7fffaf7

commit 5293efe62d

3 changed files with 150 additions and 4 deletions

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43

include/linux/skbuff.h

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11

include/uapi/linux/bpf.h

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100

net/core/filter.c

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