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Date: Fri, 25 Jan 2019 16:29:56 -0800
From: Song Liu <liu.song.a23@...il.com>
To: Stanislav Fomichev <sdf@...gle.com>
Cc: Networking <netdev@...r.kernel.org>,
"David S . Miller" <davem@...emloft.net>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next v2 1/3] net/flow_dissector: move bpf case into __skb_flow_bpf_dissect
On Thu, Jan 24, 2019 at 8:51 AM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> This way, we can reuse it for flow dissector in BPF_PROG_TEST_RUN.
>
> No functional changes.
>
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
Acked-by: Song Liu <songliubraving@...com>
> ---
> include/linux/skbuff.h | 5 +++
> net/core/flow_dissector.c | 92 +++++++++++++++++++++++----------------
> 2 files changed, 59 insertions(+), 38 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 93f56fddd92a..be762fc34ff3 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1221,6 +1221,11 @@ static inline int skb_flow_dissector_bpf_prog_detach(const union bpf_attr *attr)
> }
> #endif
>
> +struct bpf_flow_keys;
> +bool __skb_flow_bpf_dissect(struct bpf_prog *prog,
> + const struct sk_buff *skb,
> + struct flow_dissector *flow_dissector,
> + struct bpf_flow_keys *flow_keys);
> bool __skb_flow_dissect(const struct sk_buff *skb,
> struct flow_dissector *flow_dissector,
> void *target_container,
> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
> index 9f2840510e63..bb1a54747d64 100644
> --- a/net/core/flow_dissector.c
> +++ b/net/core/flow_dissector.c
> @@ -683,6 +683,46 @@ static void __skb_flow_bpf_to_target(const struct bpf_flow_keys *flow_keys,
> }
> }
>
> +bool __skb_flow_bpf_dissect(struct bpf_prog *prog,
> + const struct sk_buff *skb,
> + struct flow_dissector *flow_dissector,
> + struct bpf_flow_keys *flow_keys)
> +{
> + struct bpf_skb_data_end cb_saved;
> + struct bpf_skb_data_end *cb;
> + u32 result;
> +
> + /* Note that even though the const qualifier is discarded
> + * throughout the execution of the BPF program, all changes(the
> + * control block) are reverted after the BPF program returns.
> + * Therefore, __skb_flow_dissect does not alter the skb.
> + */
> +
> + cb = (struct bpf_skb_data_end *)skb->cb;
> +
> + /* Save Control Block */
> + memcpy(&cb_saved, cb, sizeof(cb_saved));
> + memset(cb, 0, sizeof(*cb));
> +
> + /* Pass parameters to the BPF program */
> + memset(flow_keys, 0, sizeof(*flow_keys));
> + cb->qdisc_cb.flow_keys = flow_keys;
> + flow_keys->nhoff = skb_network_offset(skb);
> + flow_keys->thoff = flow_keys->nhoff;
> +
> + bpf_compute_data_pointers((struct sk_buff *)skb);
> + result = BPF_PROG_RUN(prog, skb);
> +
> + /* Restore state */
> + memcpy(cb, &cb_saved, sizeof(cb_saved));
> +
> + flow_keys->nhoff = clamp_t(u16, flow_keys->nhoff, 0, skb->len);
> + flow_keys->thoff = clamp_t(u16, flow_keys->thoff,
> + flow_keys->nhoff, skb->len);
> +
> + return result == BPF_OK;
> +}
> +
> /**
> * __skb_flow_dissect - extract the flow_keys struct and return it
> * @skb: sk_buff to extract the flow from, can be NULL if the rest are specified
> @@ -714,7 +754,6 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
> struct flow_dissector_key_vlan *key_vlan;
> enum flow_dissect_ret fdret;
> enum flow_dissector_key_id dissector_vlan = FLOW_DISSECTOR_KEY_MAX;
> - struct bpf_prog *attached = NULL;
> int num_hdrs = 0;
> u8 ip_proto = 0;
> bool ret;
> @@ -754,53 +793,30 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
> FLOW_DISSECTOR_KEY_BASIC,
> target_container);
>
> - rcu_read_lock();
> if (skb) {
> + struct bpf_flow_keys flow_keys;
> + struct bpf_prog *attached = NULL;
> +
> + rcu_read_lock();
> +
> if (skb->dev)
> attached = rcu_dereference(dev_net(skb->dev)->flow_dissector_prog);
> else if (skb->sk)
> attached = rcu_dereference(sock_net(skb->sk)->flow_dissector_prog);
> else
> WARN_ON_ONCE(1);
> - }
> - if (attached) {
> - /* Note that even though the const qualifier is discarded
> - * throughout the execution of the BPF program, all changes(the
> - * control block) are reverted after the BPF program returns.
> - * Therefore, __skb_flow_dissect does not alter the skb.
> - */
> - struct bpf_flow_keys flow_keys = {};
> - struct bpf_skb_data_end cb_saved;
> - struct bpf_skb_data_end *cb;
> - u32 result;
> -
> - cb = (struct bpf_skb_data_end *)skb->cb;
> -
> - /* Save Control Block */
> - memcpy(&cb_saved, cb, sizeof(cb_saved));
> - memset(cb, 0, sizeof(cb_saved));
>
> - /* Pass parameters to the BPF program */
> - cb->qdisc_cb.flow_keys = &flow_keys;
> - flow_keys.nhoff = nhoff;
> - flow_keys.thoff = nhoff;
> -
> - bpf_compute_data_pointers((struct sk_buff *)skb);
> - result = BPF_PROG_RUN(attached, skb);
> -
> - /* Restore state */
> - memcpy(cb, &cb_saved, sizeof(cb_saved));
> -
> - flow_keys.nhoff = clamp_t(u16, flow_keys.nhoff, 0, skb->len);
> - flow_keys.thoff = clamp_t(u16, flow_keys.thoff,
> - flow_keys.nhoff, skb->len);
> -
> - __skb_flow_bpf_to_target(&flow_keys, flow_dissector,
> - target_container);
> + if (attached) {
> + ret = __skb_flow_bpf_dissect(attached, skb,
> + flow_dissector,
> + &flow_keys);
> + __skb_flow_bpf_to_target(&flow_keys, flow_dissector,
> + target_container);
> + rcu_read_unlock();
> + return ret;
> + }
> rcu_read_unlock();
> - return result == BPF_OK;
> }
> - rcu_read_unlock();
>
> if (dissector_uses_key(flow_dissector,
> FLOW_DISSECTOR_KEY_ETH_ADDRS)) {
> --
> 2.20.1.321.g9e740568ce-goog
>
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