Re: [PATCH 2/2] selftests/bpf: test a BPF CC writing app_limited

[Martin KaFai Lau <martin.lau@linux.dev>]

On 3/28/23 6:20 AM, Yixin Shen wrote:
> diff --git a/tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.c b/tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.c
> new file mode 100644
> index 000000000000..de5c9b5045a1
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/tcp_ca_write_app_limited.c
> @@ -0,0 +1,71 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include "vmlinux.h"
> +
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +#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;
> +}
> +
> +static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
> +{
> +	return tp->sacked_out + tp->lost_out;
> +}
> +
> +static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
> +{
> +	return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
> +}
> +
> +SEC("struct_ops/write_app_limited_init")
> +void BPF_PROG(write_app_limited_init, struct sock *sk)
> +{
> +#ifdef ENABLE_ATOMICS_TESTS
> +	__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/write_app_limited_cong_control")
> +void BPF_PROG(write_app_limited_cong_control, struct sock *sk,
> +	      const struct rate_sample *rs)
> +{
> +	struct tcp_sock *tp = tcp_sk(sk);
> +	unsigned long rate =
> +		((tp->snd_cwnd * tp->mss_cache * USEC_PER_SEC) << 3) /
> +		(tp->srtt_us ?: 1U << 3);
> +	sk->sk_pacing_rate = min(rate, sk->sk_max_pacing_rate);
> +	tp->app_limited = (tp->delivered + tcp_packets_in_flight(tp)) ?: 1;

Please add this line testing tp->app_limited to tcp_ca_write_sk_pacing.c instead 
of creating a new bpf prog that looks pretty much the same.

Also tag the subject with bpf-next in v2.

Others lgtm.