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Date: Thu, 23 Nov 2023 20:37:49 +0800
From: Philo Lu <lulie@...ux.alibaba.com>
To: bpf@...r.kernel.org
Cc: xuanzhuo@...ux.alibaba.com, dust.li@...ux.alibaba.com,
alibuda@...ux.alibaba.com, guwen@...ux.alibaba.com,
hengqi@...ux.alibaba.com, edumazet@...gle.com, davem@...emloft.net,
kuba@...nel.org, pabeni@...hat.com, ast@...nel.org, daniel@...earbox.net,
andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
yonghong.song@...ux.dev, john.fastabend@...il.com, kpsingh@...nel.org,
sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org, dsahern@...nel.org,
netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next] bpf: add sock_ops callbacks for data
send/recv/acked events
Sorry, I forgot to cc the maintainers.
On 2023/11/23 11:07, Philo Lu wrote:
> Add 3 sock_ops operators, namely BPF_SOCK_OPS_DATA_SEND_CB,
> BPF_SOCK_OPS_DATA_RECV_CB, and BPF_SOCK_OPS_DATA_ACKED_CB. A flag
> BPF_SOCK_OPS_DATA_EVENT_CB_FLAG is provided to minimize the performance
> impact. The flag must be explicitly set to enable these callbacks.
>
> If the flag is enabled, bpf sock_ops program will be called every time a
> tcp data packet is sent, received, and acked.
> BPF_SOCK_OPS_DATA_SEND_CB: call bpf after a data packet is sent.
> BPF_SOCK_OPS_DATA_RECV_CB: call bpf after a data packet is receviced.
> BPF_SOCK_OPS_DATA_ACKED_CB: call bpf after a valid ack packet is
> processed (some sent data are ackknowledged).
>
> We use these callbacks for fine-grained tcp monitoring, which collects
> and analyses every tcp request/response event information. The whole
> system has been described in SIGMOD'18 (see
> https://dl.acm.org/doi/pdf/10.1145/3183713.3190659 for details). To
> achieve this with bpf, we require hooks for data events that call
> sock_ops bpf (1) when any data packet is sent/received/acked, and (2)
> after critical tcp state variables have been updated (e.g., snd_una,
> snd_nxt, rcv_nxt). However, existing sock_ops operators cannot meet our
> requirements.
>
> Besides, these hooks also help to debug tcp when data send/recv/acked.
>
> Signed-off-by: Philo Lu <lulie@...ux.alibaba.com>
> ---
> include/net/tcp.h | 9 +++++++++
> include/uapi/linux/bpf.h | 14 +++++++++++++-
> net/ipv4/tcp_input.c | 4 ++++
> net/ipv4/tcp_output.c | 2 ++
> 4 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index d2f0736b76b8..73eda03fdda5 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -2660,6 +2660,15 @@ static inline void tcp_bpf_rtt(struct sock *sk)
> tcp_call_bpf(sk, BPF_SOCK_OPS_RTT_CB, 0, NULL);
> }
>
> +/* op must be one of BPF_SOCK_OPS_DATA_SEND_CB, BPF_SOCK_OPS_DATA_RECV_CB,
> + * or BPF_SOCK_OPS_DATA_ACKED_CB.
> + */
> +static inline void tcp_bpf_data_event(struct sock *sk, int op)
> +{
> + if (BPF_SOCK_OPS_TEST_FLAG(tcp_sk(sk), BPF_SOCK_OPS_DATA_EVENT_CB_FLAG))
> + tcp_call_bpf(sk, op, 0, NULL);
> +}
> +
> #if IS_ENABLED(CONFIG_SMC)
> extern struct static_key_false tcp_have_smc;
> #endif
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 7cf8bcf9f6a2..2154a6235901 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3016,6 +3016,7 @@ union bpf_attr {
> * * **BPF_SOCK_OPS_RETRANS_CB_FLAG** (retransmission)
> * * **BPF_SOCK_OPS_STATE_CB_FLAG** (TCP state change)
> * * **BPF_SOCK_OPS_RTT_CB_FLAG** (every RTT)
> + * * **BPF_SOCK_OPS_DATA_EVENT_CB_FLAG** (data packet send/recv/acked)
> *
> * Therefore, this function can be used to clear a callback flag by
> * setting the appropriate bit to zero. e.g. to disable the RTO
> @@ -6755,8 +6756,10 @@ enum {
> * options first before the BPF program does.
> */
> BPF_SOCK_OPS_WRITE_HDR_OPT_CB_FLAG = (1<<6),
> + /* Call bpf when data send/recv/acked. */
> + BPF_SOCK_OPS_DATA_EVENT_CB_FLAG = (1<<7),
> /* Mask of all currently supported cb flags */
> - BPF_SOCK_OPS_ALL_CB_FLAGS = 0x7F,
> + BPF_SOCK_OPS_ALL_CB_FLAGS = 0xFF,
> };
>
> /* List of known BPF sock_ops operators.
> @@ -6869,6 +6872,15 @@ enum {
> * by the kernel or the
> * earlier bpf-progs.
> */
> + BPF_SOCK_OPS_DATA_SEND_CB, /* Calls BPF program when a
> + * data packet is sent. Pure ack is ignored.
> + */
> + BPF_SOCK_OPS_DATA_RECV_CB, /* Calls BPF program when a
> + * data packet is received. Pure ack is ignored.
> + */
> + BPF_SOCK_OPS_DATA_ACKED_CB, /* Calls BPF program when sent
> + * data are acknowledged.
> + */
> };
>
> /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index bcb55d98004c..72c6192e7cd0 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -824,6 +824,8 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
>
> now = tcp_jiffies32;
>
> + tcp_bpf_data_event(sk, BPF_SOCK_OPS_DATA_RECV_CB);
> +
> if (!icsk->icsk_ack.ato) {
> /* The _first_ data packet received, initialize
> * delayed ACK engine.
> @@ -3454,6 +3456,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, const struct sk_buff *ack_skb,
> flag |= FLAG_SET_XMIT_TIMER; /* set TLP or RTO timer */
> }
>
> + tcp_bpf_data_event(sk, BPF_SOCK_OPS_DATA_ACKED_CB);
> +
> if (icsk->icsk_ca_ops->pkts_acked) {
> struct ack_sample sample = { .pkts_acked = pkts_acked,
> .rtt_us = sack->rate->rtt_us };
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index eb13a55d660c..ddd6a9c2150f 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2821,6 +2821,8 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
> /* Send one loss probe per tail loss episode. */
> if (push_one != 2)
> tcp_schedule_loss_probe(sk, false);
> +
> + tcp_bpf_data_event(sk, BPF_SOCK_OPS_DATA_SEND_CB);
> return false;
> }
> return !tp->packets_out && !tcp_write_queue_empty(sk);
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