netdev - Re: [PATCH bpf-next] bpf: add sock_ops callbacks for data send/recv/acked events

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Date: Fri, 24 Nov 2023 10:47:40 +0100
From: Daniel Borkmann <daniel@...earbox.net>
To: Philo Lu <lulie@...ux.alibaba.com>, 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, 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

On 11/23/23 1:37 PM, Philo Lu wrote:
> 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(-)

Please also add selftests for the new hooks, and speaking of the latter
looks like this fails current BPF selftests :

https://github.com/kernel-patches/bpf/actions/runs/6974541866/job/18980491457

Notice: Success: 502/3526, Skipped: 56, Failed: 1
Error: #348 tcpbpf_user
   Error: #348 tcpbpf_user
   test_tcpbpf_user:PASS:open and load skel 0 nsec
   test_tcpbpf_user:PASS:test__join_cgroup(/tcpbpf-user-test) 0 nsec
   test_tcpbpf_user:PASS:attach_cgroup(bpf_testcb) 0 nsec
   run_test:PASS:start_server 0 nsec
   run_test:PASS:connect_to_fd(listen_fd) 0 nsec
   run_test:PASS:accept(listen_fd) 0 nsec
   run_test:PASS:send(cli_fd) 0 nsec
   run_test:PASS:recv(accept_fd) 0 nsec
   run_test:PASS:send(accept_fd) 0 nsec
   run_test:PASS:recv(cli_fd) 0 nsec
   run_test:PASS:recv(cli_fd) for fin 0 nsec
   run_test:PASS:recv(accept_fd) for fin 0 nsec
   verify_result:PASS:event_map 0 nsec
   verify_result:PASS:bytes_received 0 nsec
   verify_result:PASS:bytes_acked 0 nsec
   verify_result:PASS:data_segs_in 0 nsec
   verify_result:PASS:data_segs_out 0 nsec
   verify_result:FAIL:bad_cb_test_rv unexpected bad_cb_test_rv: actual 0 != expected 128
   verify_result:PASS:good_cb_test_rv 0 nsec
   verify_result:PASS:num_listen 0 nsec
   verify_result:PASS:num_close_events 0 nsec
   verify_result:PASS:tcp_save_syn 0 nsec
   verify_result:PASS:tcp_saved_syn 0 nsec
   verify_result:PASS:window_clamp_client 0 nsec
   verify_result:PASS:window_clamp_server 0 nsec
Test Results:
              bpftool: PASS
           test_progs: FAIL (returned 1)
             shutdown: CLEAN
Error: Process completed with exit code 1.