Re: [PATCH bpf-next 7/7] selftests/bpf: Test switching TCP Congestion Control algorithms.

[Kui-Feng Lee <sinquersw@gmail.com>]

On 2/16/23 14:50, Andrii Nakryiko wrote:
> On Tue, Feb 14, 2023 at 2:17 PM Kui-Feng Lee <kuifeng@meta.com> wrote:
>>
>> Create a pair of sockets that utilize the congestion control algorithm
>> under a particular name. Then switch up this congestion control
>> algorithm to another implementation and check whether newly created
>> connections using the same cc name now run the new implementation.
>>
>> Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
>> ---
>>   .../selftests/bpf/prog_tests/bpf_tcp_ca.c     | 48 ++++++++++++
>>   .../selftests/bpf/progs/tcp_ca_update.c       | 75 +++++++++++++++++++
>>   2 files changed, 123 insertions(+)
>>   create mode 100644 tools/testing/selftests/bpf/progs/tcp_ca_update.c
>>
> 
> [...]
> 
>> diff --git a/tools/testing/selftests/bpf/progs/tcp_ca_update.c b/tools/testing/selftests/bpf/progs/tcp_ca_update.c
>> new file mode 100644
>> index 000000000000..cf51fe54ac01
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/tcp_ca_update.c
>> @@ -0,0 +1,75 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +
>> +#include "vmlinux.h"
>> +
>> +#include <bpf/bpf_helpers.h>
>> +#include <bpf/bpf_tracing.h>
>> +
>> +char _license[] SEC("license") = "GPL";
>> +
>> +int ca1_cnt = 0;
>> +int ca2_cnt = 0;
>> +
>> +#define USEC_PER_SEC 1000000UL
>> +
>> +#define min(a, b) ((a) < (b) ? (a) : (b))
>> +
>> +static inline struct tcp_sock *tcp_sk(const struct sock *sk)
>> +{
>> +       return (struct tcp_sock *)sk;
>> +}
>> +
>> +SEC("struct_ops/ca_update_init")
>> +void BPF_PROG(ca_update_init, struct sock *sk)
>> +{
>> +#ifdef ENABLE_ATOMICS_TESTS
> 
> it's been 2 years since atomics were added to Clang, I think it's fine
> to just assume atomic operations are supported and not do the
> ENABLE_ATOMICS_TEST (and I'd clean up ENABLE_ATOMICS_TESTS now as
> well)

Sure!

> 
>> +       __sync_bool_compare_and_swap(&sk->sk_pacing_status, SK_PACING_NONE,
>> +                                    SK_PACING_NEEDED);
>> +#else
>> +       sk->sk_pacing_status = SK_PACING_NEEDED;
>> +#endif
>> +}
>> +
>> +SEC("struct_ops/ca_update_1_cong_control")
>> +void BPF_PROG(ca_update_1_cong_control, struct sock *sk,
>> +             const struct rate_sample *rs)
>> +{
>> +       ca1_cnt++;
>> +}
>> +
>> +SEC("struct_ops/ca_update_2_cong_control")
>> +void BPF_PROG(ca_update_2_cong_control, struct sock *sk,
>> +             const struct rate_sample *rs)
>> +{
>> +       ca2_cnt++;
>> +}
>> +
>> +SEC("struct_ops/ca_update_ssthresh")
>> +__u32 BPF_PROG(ca_update_ssthresh, struct sock *sk)
>> +{
>> +       return tcp_sk(sk)->snd_ssthresh;
>> +}
>> +
>> +SEC("struct_ops/ca_update_undo_cwnd")
>> +__u32 BPF_PROG(ca_update_undo_cwnd, struct sock *sk)
>> +{
>> +       return tcp_sk(sk)->snd_cwnd;
>> +}
>> +
>> +SEC(".struct_ops")
>> +struct tcp_congestion_ops ca_update_1 = {
>> +       .init = (void *)ca_update_init,
>> +       .cong_control = (void *)ca_update_1_cong_control,
>> +       .ssthresh = (void *)ca_update_ssthresh,
>> +       .undo_cwnd = (void *)ca_update_undo_cwnd,
>> +       .name = "tcp_ca_update",
>> +};
>> +
>> +SEC(".struct_ops")
>> +struct tcp_congestion_ops ca_update_2 = {
>> +       .init = (void *)ca_update_init,
>> +       .cong_control = (void *)ca_update_2_cong_control,
>> +       .ssthresh = (void *)ca_update_ssthresh,
>> +       .undo_cwnd = (void *)ca_update_undo_cwnd,
>> +       .name = "tcp_ca_update",
>> +};
>> --
>> 2.30.2
>>