On Fri, Mar 1, 2019 at 12:39 PM brakmo <bra...@fb.com> wrote:
>
> This patch adds a new bpf helper BPF_FUNC_skb_ecn_set_ce
> "int bpf_skb_ecn_set_ce(struct sk_buff *skb)". It is added to
> BPF_PROG_TYPE_CGROUP_SKB typed bpf_prog which currently can
> be attached to the ingress and egress path. The helper is needed
> because his type of bpf_prog cannot modify the skb directly.
>
> This helper is used to set the ECN field of ECN capable IP packets to ce
> (congestion encountered) in the IPv6 or IPv4 header of the skb. It can be
> used by a bpf_prog to manage egress or ingress network bandwdith limit
> per cgroupv2 by inducing an ECN response in the TCP sender.
> This works best when using DCTCP.
>
> Signed-off-by: Lawrence Brakmo <bra...@fb.com>
> Signed-off-by: Martin KaFai Lau <ka...@fb.com>
Acked-by: Song Liu <songliubrav...@fb.com>
> ---
> include/uapi/linux/bpf.h | 10 +++++++++-
> net/core/filter.c | 28 ++++++++++++++++++++++++++++
> 2 files changed, 37 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 2e308e90ffea..3c38ac9a92a7 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2359,6 +2359,13 @@ union bpf_attr {
> * Return
> * A **struct bpf_tcp_sock** pointer on success, or NULL in
> * case of failure.
> + *
> + * int bpf_skb_ecn_set_ce(struct sk_buf *skb)
> + * Description
> + * Sets ECN of IP header to ce (congestion encountered) if
> + * current value is ect (ECN capable). Works with IPv6 and IPv4.
> + * Return
> + * 1 if set, 0 if not set.
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -2457,7 +2464,8 @@ union bpf_attr {
> FN(spin_lock), \
> FN(spin_unlock), \
> FN(sk_fullsock), \
> - FN(tcp_sock),
> + FN(tcp_sock), \
> + FN(skb_ecn_set_ce),
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> * function eBPF program intends to call
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 85749f6ec789..558ca72f2254 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5426,6 +5426,32 @@ static const struct bpf_func_proto bpf_tcp_sock_proto
> = {
> .arg1_type = ARG_PTR_TO_SOCK_COMMON,
> };
>
> +BPF_CALL_1(bpf_skb_ecn_set_ce, struct sk_buff *, skb)
> +{
> + unsigned int iphdr_len;
> +
> + if (skb->protocol == cpu_to_be16(ETH_P_IP))
> + iphdr_len = sizeof(struct iphdr);
> + else if (skb->protocol == cpu_to_be16(ETH_P_IPV6))
> + iphdr_len = sizeof(struct ipv6hdr);
> + else
> + return 0;
> +
> + if (skb_headlen(skb) < iphdr_len)
> + return 0;
> +
> + if (skb_cloned(skb) && !skb_clone_writable(skb, iphdr_len))
> + return 0;
> +
> + return INET_ECN_set_ce(skb);
> +}
> +
> +static const struct bpf_func_proto bpf_skb_ecn_set_ce_proto = {
> + .func = bpf_skb_ecn_set_ce,
> + .gpl_only = false,
> + .ret_type = RET_INTEGER,
> + .arg1_type = ARG_PTR_TO_CTX,
> +};
> #endif /* CONFIG_INET */
>
> bool bpf_helper_changes_pkt_data(void *func)
> @@ -5585,6 +5611,8 @@ cg_skb_func_proto(enum bpf_func_id func_id, const
> struct bpf_prog *prog)
> #ifdef CONFIG_INET
> case BPF_FUNC_tcp_sock:
> return &bpf_tcp_sock_proto;
> + case BPF_FUNC_skb_ecn_set_ce:
> + return &bpf_skb_ecn_set_ce_proto;
> #endif
> default:
> return sk_filter_func_proto(func_id, prog);
> --
> 2.17.1
>
