tcp_cong.c

https://github.com/torvalds/linux/blob/master/net/ipv4/tcp_cong.c

int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
{
	int ret = 0;

	/* all algorithms must implement these */
	if (!ca->ssthresh || !ca->undo_cwnd ||
	    !(ca->cong_avoid || ca->cong_control)) {
		pr_err("%s does not implement required ops\n", ca->name);
		return -EINVAL;
	}

	ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name));

	spin_lock(&tcp_cong_list_lock);
	if (ca->key == TCP_CA_UNSPEC || tcp_ca_find_key(ca->key)) {
		pr_notice("%s already registered or non-unique key\n",
			  ca->name);
		ret = -EEXIST;
	} else {
		list_add_tail_rcu(&ca->list, &tcp_cong_list);
		pr_debug("%s registered\n", ca->name);
	}
	spin_unlock(&tcp_cong_list_lock);

	return ret;
}

=

void tcp_init_congestion_control(struct sock *sk)
{
	const struct inet_connection_sock *icsk = inet_csk(sk);

	tcp_sk(sk)->prior_ssthresh = 0;
	if (icsk->icsk_ca_ops->init)
		icsk->icsk_ca_ops->init(sk);
	if (tcp_ca_needs_ecn(sk))
		INET_ECN_xmit(sk);
	else
		INET_ECN_dontxmit(sk);
}