From 5293efe62df81908f2e90c9820c7edcc8e61f5e9 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Thu, 18 Aug 2016 01:00:39 +0200 Subject: bpf: add bpf_skb_change_tail helper 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 Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- include/uapi/linux/bpf.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 866d53c33298..e4c5a1baa993 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -386,6 +386,17 @@ enum bpf_func_id { */ BPF_FUNC_current_task_under_cgroup, + /** + * bpf_skb_change_tail(skb, len, flags) + * The helper will resize the skb to the given new size, + * to be used f.e. with control messages. + * @skb: pointer to skb + * @len: new skb length + * @flags: reserved + * Return: 0 on success or negative error + */ + BPF_FUNC_skb_change_tail, + __BPF_FUNC_MAX_ID, }; -- cgit v1.2.3