__bpf_kfunc u32 tcp_slow_start(struct tcp_sock *tp, u32 acked)
{
	u32 cwnd = min(tcp_snd_cwnd(tp) + acked, tp->snd_ssthresh);

	acked -= cwnd - tcp_snd_cwnd(tp);
	tcp_snd_cwnd_set(tp, min(cwnd, tp->snd_cwnd_clamp));

	return acked;
}
…
__bpf_kfunc void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked)
{
	/* If credits accumulated at a higher w, apply them gently now. */
	if (tp->snd_cwnd_cnt >= w) {
		tp->snd_cwnd_cnt = 0;
		tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
	}

	tp->snd_cwnd_cnt += acked;
	if (tp->snd_cwnd_cnt >= w) {
		u32 delta = tp->snd_cwnd_cnt / w;

		tp->snd_cwnd_cnt -= delta * w;
		tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + delta);
	}
	tcp_snd_cwnd_set(tp, min(tcp_snd_cwnd(tp), tp->snd_cwnd_clamp));
}
…
__bpf_kfunc void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
{
	struct tcp_sock *tp = tcp_sk(sk);

	if (!tcp_is_cwnd_limited(sk))
		return;

	/* In "safe" area, increase. */
	if (tcp_in_slow_start(tp)) {
		acked = tcp_slow_start(tp, acked);
		if (!acked)
			return;
	}
	/* In dangerous area, increase slowly. */
	tcp_cong_avoid_ai(tp, tcp_snd_cwnd(tp), acked);
}
…
__bpf_kfunc u32 tcp_reno_ssthresh(struct sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);

	return max(tcp_snd_cwnd(tp) >> 1U, 2U);
}

Échauffement