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SubjectRe: [PATCH] bpf: allow BPF programs access skb_shared_info->gso_segs field
Sorry, forgot to annotate the subject line with bpf-next.

On Sun, Jul 15, 2018 at 1:45 AM Eddie Hao <eddieh@google.com> wrote:
>
> This adds the ability to read gso_segs from a BPF program. This is useful
> for user space monitoring systems to get gso_segs statistics for each
> arbitrary group of flows defined by the BPF program.
>
> Signed-off-by: Eddie Hao <eddieh@google.com>
> ---
> include/uapi/linux/bpf.h | 1 +
> net/core/filter.c | 9 +++++++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index b7db3261c62d..282085445616 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2266,6 +2266,7 @@ struct __sk_buff {
> /* ... here. */
>
> __u32 data_meta;
> + unsigned short gso_segs;
> };
>
> struct bpf_tunnel_key {
> diff --git a/net/core/filter.c b/net/core/filter.c
> index b9ec916f4e3a..f17e249f3fbb 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5820,6 +5820,15 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
> bpf_target_off(struct sock_common,
> skc_num, 2, target_size));
> break;
> +
> + case offsetof(struct __sk_buff, gso_segs):
> + BUILD_BUG_ON(FIELD_SIZEOF(struct skb_shared_info, gso_segs) !=
> + sizeof(unsigned short));
> + off = offsetof(struct sk_buff, end);
> + off += offsetof(struct skb_shared_info, gso_segs);
> + *insn++ = BPF_LDX_MEM(BPF_SIZEOF(unsigned short), si->dst_reg,
> + si->src_reg, off);
> + break;
> }
>
> return insn - insn_buf;
> --
> 2.18.0.203.gfac676dfb9-goog
>

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