[PATCHv6 net-next] tcp: Add TCP ROCCET congestion control module.

@@ -663,6 +663,18 @@ config TCP_CONG_CDG
 	    delay gradients." In Networking 2011. Preprint:
 	    http://caia.swin.edu.au/cv/dahayes/content/networking2011-cdg-preprint.pdf
 
+config TCP_CONG_ROCCET
+	tristate "ROCCET TCP"
+	default n
+	help
+	  TCP ROCCET (RTT oriented CUBIC congestion control exTension) is a
+	  sender-side-only congestion control algorithm based on the TCP CUBIC
+	  protocol stack/TCP CUBIC congestion control algorithm that optimizes
+	  its performance. Especially for networks with large buffers
+	  (wireless, cellular networks), TCP ROCCET has improved performance by
+	  maintaining a similar throughput as CUBIC while reducing latency.
+	  For more information, see: https://arxiv.org/abs/2510.25281
+
 config TCP_CONG_BBR
 	tristate "BBR TCP"
 	default n

@@ -45,6 +45,7 @@ obj-$(CONFIG_INET_TCP_DIAG) += tcp_diag.o
 obj-$(CONFIG_INET_UDP_DIAG) += udp_diag.o
 obj-$(CONFIG_INET_RAW_DIAG) += raw_diag.o
 obj-$(CONFIG_TCP_CONG_BBR) += tcp_bbr.o
+obj-$(CONFIG_TCP_CONG_ROCCET) += tcp_roccet.o
 obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o
 obj-$(CONFIG_TCP_CONG_CDG) += tcp_cdg.o
 obj-$(CONFIG_TCP_CONG_CUBIC) += tcp_cubic.o

@@ -0,0 +1,1233 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * TCP ROCCET: An RTT-Oriented CUBIC Congestion Control
+ * Extension for 5G and Beyond Networks
+ *
+ * TCP ROCCET is a new TCP congestion control
+ * algorithm suited for current cellular 5G NR beyond networks.
+ * It extends the kernel default congestion control CUBIC
+ * and improves its performance, and additionally solves an
+ * unwanted side effects of CUBIC’s implementation.
+ * ROCCET uses its own Slow Start, called LAUNCH, where loss
+ * is not considered as a congestion event.
+ * The congestion avoidance phase, called ORBITER, uses
+ * CUBIC's window growth function and adds, based on RTT
+ * and ACK rate, congestion events.
+ *
+ * A peer-reviewed paper on TCP ROCCET will be presented
+ * at the WONS 2026 conference.
+ * A draft of the paper is available here:
+ *		https://arxiv.org/abs/2510.25281
+ *
+ *
+ * Further information about CUBIC:
+ * TCP CUBIC: Binary Increase Congestion control for TCP v2.3
+ * Home page:
+ *	http://netsrv.csc.ncsu.edu/twiki/bin/view/Main/BIC
+ * This is from the implementation of CUBIC TCP in
+ * Sangtae Ha, Injong Rhee and Lisong Xu,
+ *  "CUBIC: A New TCP-Friendly High-Speed TCP Variant"
+ *  in ACM SIGOPS Operating System Review, July 2008.
+ * Available from:
+ *  http://netsrv.csc.ncsu.edu/export/cubic_a_new_tcp_2008.pdf
+ *
+ * CUBIC integrates a new slow start algorithm, called HyStart.
+ * The details of HyStart are presented in
+ *  Sangtae Ha and Injong Rhee,
+ *  "Taming the Elephants: New TCP Slow Start", NCSU TechReport 2008.
+ * Available from:
+ *  http://netsrv.csc.ncsu.edu/export/hystart_techreport_2008.pdf
+ *
+ * All testing results are available from:
+ * http://netsrv.csc.ncsu.edu/wiki/index.php/TCP_Testing
+ *
+ * Unless CUBIC is enabled and congestion window is large
+ * this behaves the same as the original Reno.
+ */
+
+#include <linux/time.h>
+#include <linux/printk.h>
+#include <linux/math64.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <net/tcp.h>
+
+/* Scale factor beta calculation (max_cwnd = snd_cwnd * beta) */
+#define BICTCP_BETA_SCALE 1024
+
+#define BICTCP_HZ 10 /* BIC HZ 2^10 = 1024 */
+
+/* Alpha value for the srRTT  multiplied by 100.
+ * Here 20 represents a value of 0.2
+ */
+#define ROCCET_ALPHA_TIMES_100 20
+
+/* min RTT probe period in ms */
+#define ROCCET_NEXT_MIN_RTT_PROBE 5000
+
+/* State in which roccet currently operates */
+enum roccet_state {
+	LAUNCH,
+	ORBITER,
+	RTT_PROBE_ENTER,
+	RTT_PROBE,
+	RTT_PROBE_REFILL,
+	DRAIN
+};
+
+/* TCP ROCCET struct based on the original BICTCP struct with
+ * additions specific to the ROCCET-Algorithm.
+ */
+struct roccettcp {
+	u32 cnt;	/* increase cwnd by 1 after ACKs */
+	u32 last_max_cwnd;	/* last maximum snd_cwnd */
+	u32 last_cwnd;	/* the last snd_cwnd */
+	u32 last_time;	/* time when updated last_cwnd */
+	u32 bic_origin_point;	/* origin point of bic function */
+	u32 bic_K;	/* time to origin point from the
+			 * beginning of the current epoch
+			 */
+	u32 delay_min;	/* min delay (usec) */
+	u32 epoch_start;	/* beginning of an epoch */
+	u32 ack_cnt;	/* number of acks */
+	u32 tcp_cwnd;	/* estimated tcp cwnd */
+	u32 curr_rtt;	/* last sample rtt of current round */
+
+	u32 roccet_last_event_time_us;	/* The last time ROCCET was triggered */
+	u32 curr_min_rtt;	/* The current observed minRTT */
+	u32 next_min_rtt_probe;	/* Next time to probe the minRTT */
+	u32 probe_min_rtt_until;	/* End of minRTT probing period.
+					 * Set while in RTT_PROBE states
+					 */
+	u32 refill_until;	/* End of pipe refill after minRTT probe.
+				 * Set while in RTT_PROBE states
+				 */
+	u32 cwnd_before_min_rtt_probe;	/* cwnd before min RTT probing. */
+	u32 curr_srrtt;	/* srRTT calculated based on the latest ACK */
+	u32 next_srrtt_check_ts;	/* Next check for srRTT */
+	u32 last_rtt;	/* sample rtt of previous round.
+			 * Used for jitter calculation
+			 */
+
+	u32 interval_snd_seq_start;
+	u32 interval_una_seq_start;
+
+	u32 ack_rate_last_rate_time;	/* Timestamp of the last ACK-rate */
+	u16 ack_rate_last_rate;	/* Last ACK-rate */
+	u16 ack_rate_curr_rate;	/* Current ACK-rate */
+	u16 ack_rate_cnt;	/* Used for counting acks */
+
+	enum roccet_state state : 3; /* Current operating state of roccet */
+	bool was_idle : 1;	/* Tracks whether the connection was idle
+				 * (had no in-flight packets)
+				 */
+	bool initial_limit_reached: 1;	/* Set to true after the connection
+					 * initially gets cwnd-limited
+					 */
+	bool is_in_initial_launch: 1;	/* true if the connection is in
+					 * the initial launch phase.
+					 */
+	u32 ack_carry_over;	/* Used to carry over leftover acks from
+				 * LAUNCH to ORBITER
+				 */
+};
+
+/* Parameters that are specific to the ROCCET-Algorithm */
+static uint sr_rtt_upper_bound __read_mostly = 100;
+static int ack_rate_diff_ss __read_mostly = 10;
+
+module_param(sr_rtt_upper_bound, uint, 0644);
+MODULE_PARM_DESC(sr_rtt_upper_bound, "ROCCET's upper bound for srRTT.");
+module_param(ack_rate_diff_ss, int, 0644);
+MODULE_PARM_DESC(ack_rate_diff_ss,
+		 "ROCCET's threshold to exit slow start if ACK-rate differs by given amount of segments.");
+
+static int fast_convergence __read_mostly = 1;
+static int beta __read_mostly = 717; /* = 717/1024 (BICTCP_BETA_SCALE) */
+static int initial_ssthresh __read_mostly;
+static int bic_scale __read_mostly = 41;
+static int tcp_friendliness __read_mostly = 1;
+
+static u32 cube_rtt_scale __read_mostly;
+static u32 beta_scale __read_mostly;
+static u64 cube_factor __read_mostly;
+
+/* Note parameters that are used for precomputing scale factors are read-only */
+module_param(fast_convergence, int, 0644);
+MODULE_PARM_DESC(fast_convergence, "turn on/off fast convergence");
+module_param(beta, int, 0644);
+MODULE_PARM_DESC(beta, "beta for multiplicative increase");
+module_param(initial_ssthresh, int, 0644);
+MODULE_PARM_DESC(initial_ssthresh, "initial value of slow start threshold");
+module_param(bic_scale, int, 0444);
+MODULE_PARM_DESC(bic_scale,
+		 "scale (scaled by 1024) value for bic function (bic_scale/1024)");
+module_param(tcp_friendliness, int, 0644);
+MODULE_PARM_DESC(tcp_friendliness, "turn on/off tcp friendliness");
+
+/* Used to check certain roccet parameters used in `param_precompute` in order
+ * to avoid invalid scale-related calculations. This validates the specified
+ * parameters or rejects them.
+ */
+static int param_check(void)
+{
+	if (beta <= 0 || beta >= BICTCP_BETA_SCALE) {
+		pr_err_once("TCP ROCCET: beta must be between 0 and %d\n",
+			    BICTCP_BETA_SCALE);
+
+		return -EINVAL;
+	}
+
+	if (bic_scale <= 0) {
+		pr_err_once("TCP ROCCET: bic_scale must be positive\n");
+
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* Precompute some values based on the provided params.
+ * These are only precomputed during module initialization and are not updated
+ * during runtime. Parameter changes at runtime will only affect the next uses
+ * of the parameters, but not the precomputed values.
+ */
+static void param_precompute(void)
+{
+	/* Precompute a bunch of the scaling factors that are used per-packet
+	 * based on sRTT of 100ms.
+	 */
+	beta_scale =
+		8 * (BICTCP_BETA_SCALE + beta) / 3 / (BICTCP_BETA_SCALE - beta);
+
+	cube_rtt_scale = (bic_scale * 10); /* 1024*c/rtt */
+
+	/* calculate the "K" for (wmax-cwnd) = c/rtt * K^3
+	 *  so K = cubic_root( (wmax-cwnd)*rtt/c )
+	 * the unit of K is bictcp_HZ=2^10, not HZ
+	 *
+	 *  c = bic_scale >> 10
+	 *  rtt = 100ms
+	 *
+	 * the following code has been designed and tested for
+	 * cwnd < 1 million packets
+	 * RTT < 100 seconds
+	 * HZ < 1,000,00  (corresponding to 10 nano-second)
+	 */
+
+	/* 1/c * 2^2*bictcp_HZ * srtt */
+	cube_factor = 1ull << (10 + 3 * BICTCP_HZ); /* 2^40 */
+
+	/* divide by bic_scale and by constant srtt (100ms) */
+	do_div(cube_factor, bic_scale * 10);
+}
+
+static void roccet_reset(struct sock *sk, struct roccettcp *ca)
+{
+	memset(ca, 0, sizeof(struct roccettcp));
+	ca->next_srrtt_check_ts = 0;
+
+	/* Initialize all RTT values to U32_MAX, so that any lower samples
+	 * will be accepted.
+	 */
+	ca->curr_min_rtt = U32_MAX;
+	ca->curr_rtt = U32_MAX;
+	ca->last_rtt = U32_MAX;
+
+	ca->roccet_last_event_time_us = 0;
+	ca->ack_rate_last_rate = 0;
+
+	/* Initialize to current time to avoid an
+	 * overflow in the ack rate calculation
+	 */
+	ca->ack_rate_last_rate_time = jiffies_to_usecs(tcp_jiffies32);
+	ca->ack_rate_curr_rate = 0;
+	ca->ack_rate_cnt = 0;
+
+	ca->interval_snd_seq_start = tcp_sk(sk)->snd_nxt;
+	ca->interval_una_seq_start = tcp_sk(sk)->snd_una;
+
+	/* Start state is LAUNCH */
+	ca->state = LAUNCH;
+	ca->probe_min_rtt_until = 0;
+	ca->refill_until = 0;
+
+	ca->initial_limit_reached = false;
+	ca->is_in_initial_launch = false;
+}
+
+static void roccet_init(struct sock *sk)
+{
+	struct roccettcp *ca = inet_csk_ca(sk);
+
+	roccet_reset(sk, ca);
+
+	/* Reset here, so it is only set during init */
+	ca->is_in_initial_launch = true;
+
+	if (initial_ssthresh)
+		WRITE_ONCE(tcp_sk(sk)->snd_ssthresh, initial_ssthresh);
+
+	cmpxchg(&sk->sk_pacing_status, SK_PACING_NONE, SK_PACING_NEEDED);
+}
+
+static void update_min_rtt(struct roccettcp *ca)
+{
+	/* Check if new lower min RTT was found. If so, set it directly.
+	 * If no valid RTT sample has been received yet, the check will fail,
+	 * since the rtt values are initialized to U32_MAX.
+	 */
+	if (ca->curr_rtt < ca->curr_min_rtt) {
+		ca->curr_min_rtt = max(ca->curr_rtt, 1);
+		/* Probe for the min RTT in ROCCET_NEXT_MIN_RTT_PROBE ms
+		 * if no other update occurs.
+		 */
+		ca->next_min_rtt_probe =
+			jiffies_to_usecs(tcp_jiffies32) +
+			ROCCET_NEXT_MIN_RTT_PROBE * USEC_PER_MSEC;
+	}
+}
+
+/* Return difference between last and current ack rate.
+ */
+static s32 get_ack_rate_diff(struct roccettcp *ca)
+{
+	if (ca->ack_rate_curr_rate < ca->ack_rate_last_rate)
+		return 0;
+	return (s32)(ca->ack_rate_curr_rate - ca->ack_rate_last_rate);
+}
+
+/* Update ack rate sampled by 100ms.
+ */
+static void update_ack_rate(struct roccettcp *ca, u32 acked, u32 now)
+{
+	const s32 idle_threshold = USEC_PER_SEC * 2;
+	const s32 interval = USEC_PER_MSEC * 100;
+
+	s32 time_delta = (s32)(ca->ack_rate_last_rate_time - now);
+
+	/* Check if the time has arrived in the new interval.
+	 * Alternatively if the connection was considered to be idle,
+	 * also treat as a new interval in order to avoid timing-overflow
+	 * problems.
+	 */
+	if (time_delta < -interval || ca->was_idle) {
+		/* Check if the connection was idle for X seconds
+		 * (e.g. no ACK for X seconds)
+		 */
+		if (time_delta < -idle_threshold) {
+			/* Reset ack counting as if a new
+			 * connection was created
+			 */
+			ca->ack_rate_last_rate = 0;
+			ca->ack_rate_last_rate_time =
+				jiffies_to_usecs(tcp_jiffies32);
+			ca->ack_rate_curr_rate = 0;
+			ca->ack_rate_cnt = 0;
+		} else {
+			/* start counting for the new interval */
+			ca->ack_rate_last_rate_time = now;
+			ca->ack_rate_last_rate = ca->ack_rate_curr_rate;
+			ca->ack_rate_curr_rate = ca->ack_rate_cnt;
+			ca->ack_rate_cnt = min_t(u32, acked, U16_MAX);
+		}
+
+		ca->was_idle = false;
+	} else {
+		/* Cap the ack count to avoid overflow */
+		ca->ack_rate_cnt = min_t(u32, ca->ack_rate_cnt + acked,
+					 U16_MAX);
+	}
+}
+
+/* Compute srRTT.
+ */
+static void update_srrtt(struct roccettcp *ca)
+{
+	u64 rrtt;
+
+	/* Avoid integer overflow in the calculation below.
+	 * This could occur in cases where we have not yet
+	 * received an RTT sample after a min_rtt reset.
+	 * In these cases, set the rtt to a safe value.
+	 */
+	if (ca->curr_rtt < ca->curr_min_rtt) {
+		ca->curr_rtt = max(ca->curr_rtt, 1);
+		ca->curr_min_rtt = ca->curr_rtt;
+	}
+
+	/* ca->curr_min_rtt can never be 0. For completeness, we check for this
+	 * anyways in order to avoid division by zero errors.
+	 */
+	if (ca->curr_min_rtt == 0) {
+		pr_err_once("TCP ROCCET: Recorded curr_min_rtt is 0");
+		return; /* skip srRTT update */
+	}
+
+	/* Calculate the new rRTT (Scaled by 100).
+	 * 100 * ((sRTT - sRTT_min) / sRTT_min).
+	 *
+	 * curr_min_rtt is always <= than curr_rtt,
+	 * since this is the minimum of the rtt.
+	 *
+	 * 0 is a valid value for rrtt.
+	 *
+	 * If we have no valid RTT sample yet, curr_rtt and curr_min_rtt will
+	 * be U32_MAX. This ultimately results in no srrtt increase, which
+	 * is ok.
+	 */
+	rrtt = div_u64(100 * (u64)(ca->curr_rtt - ca->curr_min_rtt),
+		       ca->curr_min_rtt);
+
+	/* (1 - alpha) * srRTT + alpha * rRTT */
+	ca->curr_srrtt = ((100 - ROCCET_ALPHA_TIMES_100) * (u64)ca->curr_srrtt +
+			  ROCCET_ALPHA_TIMES_100 * rrtt) /
+			 100;
+}
+
+/* Handle ROCCET loss/ECN during min RTT probing.
+ */
+static void roccet_min_rtt_probe_ce(struct roccettcp *ca, u32 cwnd)
+{
+	/* This should only be called in RTT_PROBE state */
+	if (ca->state != RTT_PROBE)
+		return;
+
+	/* If ROCCET is in min RTT probing and a loss/ECN occurs,
+	 * we use the cwnd before the probing interval to
+	 * calculate the cwnd reduction and continue probing.
+	 * After min RTT probing the cwnd is set to the reduced
+	 * value. During min RTT probing it is very likely that
+	 * congestion was caused by the cwnd value before min
+	 * RTT probing.
+	 */
+
+	if (ca->cwnd_before_min_rtt_probe == 0)
+		pr_warn_once("ROCCET: cwnd_before_min_rtt_probe is 0 during RTT_PROBE. This should not happen.");
+	else
+		cwnd = ca->cwnd_before_min_rtt_probe;
+
+	ca->cwnd_before_min_rtt_probe =
+		max((cwnd * beta) / BICTCP_BETA_SCALE, 2U);
+}
+
+/* Do a ROCCET congestion event.
+ */
+static void roccet_congestion_event(struct sock *sk, u32 now)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct roccettcp *ca = inet_csk_ca(sk);
+
+	u32 curr_cwnd = tcp_snd_cwnd(tp);
+
+	ca->epoch_start = 0;
+	ca->roccet_last_event_time_us = now;
+
+	if (ca->state == RTT_PROBE) {
+		/* In case we are in RTT_PROBE, continue with this state, as
+		 * the CE was likely caused by the cwnd before probing.
+		 * However do react to the CE.
+		 */
+		roccet_min_rtt_probe_ce(ca, curr_cwnd);
+		return;
+	}
+
+	ca->cnt = 100 * curr_cwnd;
+
+	/* Set W_max only if the current cwnd is larger */
+	if (ca->last_max_cwnd < curr_cwnd)
+		ca->last_max_cwnd = curr_cwnd;
+
+	/* Reduce cwnd by beta */
+	tcp_snd_cwnd_set(tp, min(tp->snd_cwnd_clamp,
+				 max((curr_cwnd * beta)
+				     / BICTCP_BETA_SCALE, 2U)));
+
+	if (ca->state == LAUNCH) {
+		/* Set ssthresh on ECN, so that roccet is not in slow-start */
+		tp->snd_ssthresh = tcp_snd_cwnd(tp);
+		ca->state = ORBITER;
+	} else if (ca->state == ORBITER || ca->state == RTT_PROBE_REFILL) {
+		/* If we are in orbiter or currently refilling the pipe,
+		 * abort the refill.
+		 */
+		ca->state = DRAIN;
+	}
+	/* Other states (e.g. DRAIN or RTT_PROBE_ENTER) not handled as
+	 * we don`t want any action there.
+	 */
+}
+
+static void roccet_enter_min_rtt_probe(struct sock *sk, u32 now)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct roccettcp *ca = inet_csk_ca(sk);
+	u32 interval, probe_cwnd;
+
+	/* If probing is already set, there was a mix up.
+	 * Continue anyway so we can recover.
+	 */
+	if (ca->probe_min_rtt_until > 0)
+		pr_warn_once("ROCCET: Probing time should not be set");
+
+	/* Safeguard for an "infinite" probe. This should logically never
+	 * happen but still safeguard it.
+	 */
+	if (ca->curr_rtt == U32_MAX) {
+		pr_warn_once("ROCCET: curr_rtt is U32_MAX, cannot enter RTT_PROBE");
+		ca->state = ORBITER;
+		return;
+	}
+
+	/* Start min RTT probing */
+	/* Probe 1*RTT or at least 200ms */
+	interval = max(200 * USEC_PER_MSEC, ca->curr_rtt);
+
+	/* This is to handle deep shared buffers with loss-based
+	 * congestion control like CUBIC. If the cwnd is not limited
+	 * by the application but falsely detected (see ROCCET paper),
+	 * we have to empty the pipe more.
+	 * If the limit detection is correct this will cause no harm
+	 * to the tcp flow because the cwnd is not fully utilized and
+	 * we set the cwnd to its previous value after probing.
+	 */
+	if (!tcp_is_cwnd_limited(sk))
+		probe_cwnd = max(tcp_snd_cwnd(tp) / 3, TCP_INIT_CWND);
+	else
+		probe_cwnd = max(tcp_snd_cwnd(tp) / 2, TCP_INIT_CWND);
+
+	ca->probe_min_rtt_until = now + interval;
+	ca->cwnd_before_min_rtt_probe = tcp_snd_cwnd(tp);
+
+	/* Half the cwnd to drain the buffer for probing. */
+	tcp_snd_cwnd_set(tp, probe_cwnd);
+
+	/* Reset current min RTT to allow probing for
+	 * a new lower and higher minimum RTT.
+	 */
+	ca->curr_min_rtt = U32_MAX;
+
+	/* Refill the pipe after probing.
+	 * For this we use the previous cwnd for another probing interval.
+	 */
+	ca->refill_until = ca->probe_min_rtt_until + interval;
+
+	/* Now we know that ca->probe_min_rtt_until < ca->refill_until
+	 * and we advance to the next state of the probing phase.
+	 *
+	 * Wrap-arounds of these values are handled by the relevant
+	 * if-conditions.
+	 */
+
+	ca->state = RTT_PROBE;
+}
+
+/* Do minimum RTT probing.
+ */
+static void roccet_min_rtt_probe(struct sock *sk, u32 now)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct roccettcp *ca = inet_csk_ca(sk);
+
+	/* Here we are in RTT_PROBE, so the probing time should be set.
+	 * If not just continue and enter refill phase.
+	 *
+	 * probe_min_rtt_until wrap-arounds are handled by the time_before32
+	 * check.
+	 */
+	if (ca->probe_min_rtt_until == 0)
+		pr_warn_once("ROCCET: Probing time should be set");
+	else if (time_before32(now, ca->probe_min_rtt_until))
+		/* No state change if we are in the probing interval. */
+		return;
+
+	/* If the interval has passed we likely just entered the refill
+	 * interval, so go into RTT_PROBE_REFILL.
+	 * If we are not in the interval, something went wrong and we should
+	 * quickly exit the probing phase.
+	 *
+	 * Wraps-arounds of refill_until are caught by the time_after32 check.
+	 */
+	if (time_after32(now, ca->refill_until))
+		pr_warn_once("ROCCET: Skipped refill interval.");
+
+	/* Reset cwnd to refill the pipe and consequently clear the stored
+	 * window.
+	 * Also perform sanity check. THis should never happen.
+	 */
+	if (ca->cwnd_before_min_rtt_probe == 0)
+		pr_warn_once("ROCCET: cwnd_before_min_rtt_probe is 0 during RTT_PROBE.");
+	else
+		tcp_snd_cwnd_set(tp, ca->cwnd_before_min_rtt_probe);
+
+	ca->cwnd_before_min_rtt_probe = 0;
+
+	/* Exit the RTT_PROBE state */
+	ca->state = RTT_PROBE_REFILL;
+}
+
+static void roccet_rtt_probe_refill(struct roccettcp *ca, u32 now)
+{
+	/* Once the refill interval is over, we can end the probing phase. */
+	if (time_after32(now, ca->refill_until)) {
+		/* End min RTT probing phase. */
+		ca->state = ORBITER;
+	}
+}
+
+static void roccet_cwnd_event_tx_start(struct sock *sk)
+{
+	struct roccettcp *ca = inet_csk_ca(sk);
+	u32 now = tcp_jiffies32;
+	s32 delta;
+
+	delta = now - tcp_sk(sk)->lsndtime;
+
+	/* We were application limited (idle) for a while.
+	 * Shift epoch_start to keep cwnd growth to cubic curve.
+	 */
+	if (ca->epoch_start && delta > 0) {
+		ca->epoch_start += delta;
+		if (after(ca->epoch_start, now))
+			ca->epoch_start = now;
+	}
+
+	ca->was_idle = true;
+}
+
+/* calculate the cubic root of x using a table lookup followed by one
+ * Newton-Raphson iteration.
+ * Avg err ~= 0.195%
+ */
+static u32 cubic_root(u64 a)
+{
+	u32 x, b, shift;
+	/* cbrt(x) MSB values for x MSB values in [0..63].
+	 * Precomputed then refined by hand - Willy Tarreau
+	 *
+	 * For x in [0..63],
+	 *   v = cbrt(x << 18) - 1
+	 *   cbrt(x) = (v[x] + 10) >> 6
+	 */
+	static const u8 v[] = {
+		/* 0x00 */ 0,	54,  54,  54,  118, 118, 118, 118,
+		/* 0x08 */ 123, 129, 134, 138, 143, 147, 151, 156,
+		/* 0x10 */ 157, 161, 164, 168, 170, 173, 176, 179,
+		/* 0x18 */ 181, 185, 187, 190, 192, 194, 197, 199,
+		/* 0x20 */ 200, 202, 204, 206, 209, 211, 213, 215,
+		/* 0x28 */ 217, 219, 221, 222, 224, 225, 227, 229,
+		/* 0x30 */ 231, 232, 234, 236, 237, 239, 240, 242,
+		/* 0x38 */ 244, 245, 246, 248, 250, 251, 252, 254,
+	};
+
+	b = fls64(a);
+	if (b < 7) {
+		/* a in [0..63] */
+		return ((u32)v[(u32)a] + 35) >> 6;
+	}
+
+	b = ((b * 84) >> 8) - 1;
+	shift = (a >> (b * 3));
+
+	x = ((u32)(((u32)v[shift] + 10) << b)) >> 6;
+
+	/* Newton-Raphson iteration
+	 *                         2
+	 * x    = ( 2 * x  +  a / x  ) / 3
+	 *  k+1          k         k
+	 */
+	x = (2 * x + (u32)div64_u64(a, (u64)x * (u64)(x - 1)));
+	x = ((x * 341) >> 10);
+	return x;
+}
+
+/* Compute congestion window to use.
+ */
+static void bictcp_update(struct roccettcp *ca, u32 cwnd,
+			  u32 acked)
+{
+	u32 delta, bic_target, max_cnt;
+	u64 offs, t;
+
+	ca->ack_cnt += acked; /* count the number of ACKed packets */
+
+	if (ca->last_cwnd == cwnd &&
+	    (s32)(tcp_jiffies32 - ca->last_time) <= HZ / 32)
+		return;
+
+	/* The CUBIC function can update ca->cnt at most once per jiffy.
+	 * On all cwnd reduction events, ca->epoch_start is set to 0,
+	 * which will force a recalculation of ca->cnt.
+	 */
+	if (ca->epoch_start && tcp_jiffies32 == ca->last_time)
+		goto tcp_friendliness;
+
+	ca->last_cwnd = cwnd;
+	ca->last_time = tcp_jiffies32;
+
+	if (ca->epoch_start == 0) {
+		ca->epoch_start = tcp_jiffies32; /* record beginning */
+		ca->ack_cnt = acked; /* start counting */
+		ca->tcp_cwnd = cwnd; /* syn with cubic */
+
+		if (ca->last_max_cwnd <= cwnd) {
+			ca->bic_K = 0;
+			ca->bic_origin_point = cwnd;
+		} else {
+			/* Compute new K based on
+			 * (wmax-cwnd) * (srtt>>3 / HZ) / c * 2^(3*bictcp_HZ)
+			 */
+			ca->bic_K = cubic_root(cube_factor *
+					       (ca->last_max_cwnd - cwnd));
+			ca->bic_origin_point = ca->last_max_cwnd;
+		}
+	}
+
+	/* In case there are any ACKs left over from LAUNCH,
+	 * apply them after the new epoch-reset
+	 */
+	if (ca->ack_carry_over) {
+		ca->ack_cnt += ca->ack_carry_over;
+		ca->ack_carry_over = 0;
+	}
+
+	/* cubic function - calc */
+	/* calculate c * time^3 / rtt,
+	 *  while considering overflow in calculation of time^3
+	 * (so time^3 is done by using 64 bit)
+	 * and without the support of division of 64bit numbers
+	 * (so all divisions are done by using 32 bit)
+	 *  also NOTE the unit of those variables
+	 *	  time  = (t - K) / 2^bictcp_HZ
+	 *	  c = bic_scale >> 10
+	 * rtt  = (srtt >> 3) / HZ
+	 * !!! The following code does not have overflow problems,
+	 * if the cwnd < 1 million packets !!!
+	 */
+
+	t = (s32)(tcp_jiffies32 - ca->epoch_start);
+	t += usecs_to_jiffies(ca->delay_min);
+
+	/* change the unit from HZ to bictcp_HZ */
+	t <<= BICTCP_HZ;
+	do_div(t, HZ);
+
+	if (t < ca->bic_K) /* t - K */
+		offs = ca->bic_K - t;
+	else
+		offs = t - ca->bic_K;
+
+	/* c/rtt * (t-K)^3 */
+	delta = (cube_rtt_scale * offs * offs * offs) >> (10 + 3 * BICTCP_HZ);
+	if (t < ca->bic_K) /* below origin*/
+		bic_target = ca->bic_origin_point - delta;
+	else /* above origin*/
+		bic_target = ca->bic_origin_point + delta;
+
+	/* cubic function - calc bictcp_cnt*/
+	if (bic_target > cwnd)
+		ca->cnt = cwnd / (bic_target - cwnd);
+	else
+		ca->cnt = 100 * cwnd; /* very small increment*/
+
+	/* The initial growth of cubic function may be too conservative
+	 * when the available bandwidth is still unknown.
+	 */
+	if (ca->last_max_cwnd == 0 && ca->cnt > 20)
+		ca->cnt = 20; /* increase cwnd 5% per RTT */
+
+tcp_friendliness:
+	/* TCP Friendly */
+	if (tcp_friendliness) {
+		u32 scale = beta_scale;
+
+		delta = (cwnd * scale) >> 3;
+		if (delta > 0) {
+			while (ca->ack_cnt > delta) { /* update tcp cwnd */
+				ca->ack_cnt -= delta;
+				ca->tcp_cwnd++;
+			}
+		}
+
+		if (ca->tcp_cwnd > cwnd) { /* if bic is slower than tcp */
+			delta = ca->tcp_cwnd - cwnd;
+			max_cnt = cwnd / delta;
+			if (ca->cnt > max_cnt)
+				ca->cnt = max_cnt;
+		}
+	}
+
+	/* The maximum rate of cwnd increase CUBIC allows is 1 packet per
+	 * 2 packets ACKed, meaning cwnd grows at 1.5x per RTT.
+	 */
+	ca->cnt = max(ca->cnt, 2U);
+}
+
+static void roccet_launch_update(struct sock *sk, u32 acked)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct roccettcp *ca = inet_csk_ca(sk);
+
+	u32 now = jiffies_to_usecs(tcp_jiffies32);
+
+	/* LAUNCH: Detect an exit point for tcp slow start
+	 * in networks with large buffers of multiple BDP
+	 * Like in cellular networks (5G, ...).
+	 *
+	 * Or exit LAUNCH if cwnd is too large for application layer
+	 * data rate (tcp cwnd validation).
+	 */
+	if ((ca->curr_srrtt > sr_rtt_upper_bound &&
+	     get_ack_rate_diff(ca) <= ack_rate_diff_ss) ||
+	    (!tcp_is_cwnd_limited(sk) && ca->initial_limit_reached)) {
+		ca->epoch_start = 0;
+
+		/* Handle initial LAUNCH. Most bufferbloat occurs here */
+		if (ca->is_in_initial_launch) {
+			/* Halving the cwnd will undo the previous step of slow
+			 * start. Which is fine since the pipe is already full.
+			 */
+			tcp_snd_cwnd_set(tp, max(tcp_snd_cwnd(tp) / 2,
+						 TCP_INIT_CWND));
+		} else {
+			tcp_snd_cwnd_set(tp, max(tcp_snd_cwnd(tp) -
+						 (tcp_snd_cwnd(tp) / 3),
+						 TCP_INIT_CWND));
+		}
+		tp->snd_ssthresh = tcp_snd_cwnd(tp);
+		ca->roccet_last_event_time_us = now;
+		ca->state = ORBITER;
+		return;
+	}
+
+	/* If not already exiting LAUNCH, grow cwnd similar to slow-start */
+	acked = tcp_slow_start(tp, acked);
+	/* If cwnd hits ssthresh, go to ORBITER and if any ACKs are
+	 * leftover save them for ORBITER.
+	 * Check via tcp_in_slow_start() in case no ACKs are left.
+	 */
+	if (!tcp_in_slow_start(tp)) {
+		ca->state = ORBITER;
+		ca->epoch_start = 0;
+		ca->ack_carry_over = acked;
+	}
+}
+
+static void roccet_orbiter_update(struct sock *sk, u32 acked)
+{
+	/* ORBITER: Increase the cwnd by using the CUBIC cwnd growth function,
+	 * if no roccet congestion event is detected.
+	 */
+
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct roccettcp *ca = inet_csk_ca(sk);
+
+	u32 now = jiffies_to_usecs(tcp_jiffies32);
+	bool evaluate_srrtt = false;
+	bool sent_more_than_acked = false;
+	u32 roccet_xj, jitter, sent, received;
+
+	/* Enter DRAIN when roccet was recently triggered */
+	if (ca->roccet_last_event_time_us &&
+	    time_before32(now, ca->roccet_last_event_time_us +
+			  100 * USEC_PER_MSEC)) {
+		ca->state = DRAIN;
+		return;
+	}
+
+	/* Enter RTT_PROBE when the "timer" has expired.
+	 *
+	 * Since we are in ORBITER, we should have already received at least
+	 * one RTT sample. However safeguard against it if not.
+	 */
+	if (time_after32(now, ca->next_min_rtt_probe) &&
+	    ca->curr_rtt != U32_MAX) {
+		ca->state = RTT_PROBE_ENTER;
+		return;
+	}
+
+	/* Calculate jitter.
+	 * Since we are in ORBITER, we should have already received at least
+	 * one RTT sample. Even if not, ca->curr_rtt and ca->curr_min_rtt
+	 * (the divisor later on) are U32_MAX, so they cancel each other out.
+	 * And if ca->last_rtt is U32_MAX, roccet_xj will be very large, so
+	 * the srRTT will not exceed it.
+	 */
+	if ((s32)(ca->curr_rtt - ca->last_rtt) < 0)
+		jitter = ca->last_rtt - ca->curr_rtt;
+	else
+		jitter = ca->curr_rtt - ca->last_rtt;
+
+	/* Calculate if more bytes were sent than received
+	 * in the time interval.
+	 *
+	 * Handle wrap arounds by relying on unsigned subtraction.
+	 * e.g. if snd_nxt wraps to 10 and seq_start is U32_MAX - 10,
+	 * the subtraction will result in the value of 21.
+	 */
+	sent = tp->snd_nxt - ca->interval_snd_seq_start;
+	received = tp->snd_una - ca->interval_una_seq_start;
+
+	/* Check sent and received bytes from the previous interval.
+	 * Here we use a guard space of 1% of the current cwnd.
+	 * We do this to avoid a false positive evaluation due
+	 * to delays caused by jitter or scheduling.
+	 */
+	sent_more_than_acked =
+		sent >
+		received + ((tcp_snd_cwnd(tp) * tp->mss_cache) / 100);
+
+	/* Check if it's time to evaluate the srRTT */
+	if (time_after32(now, ca->next_srrtt_check_ts)) {
+		evaluate_srrtt = true;
+
+		/* reset struct and set next end of period */
+		ca->next_srrtt_check_ts = now + 5 * ca->curr_rtt;
+
+		/* Reset Rate calculation */
+		ca->interval_snd_seq_start = tp->snd_nxt;
+		ca->interval_una_seq_start = tp->snd_una;
+	}
+
+	/* Respects the jitter of the connection and add it on top of
+	 * the upper bound for the srRTT.
+	 */
+	roccet_xj = div_u64((u64)jitter * 100, ca->curr_min_rtt) +
+			sr_rtt_upper_bound;
+
+	/* The srRTT exceeds the upper bound if bufferbloat happens.
+	 * Here, we want to reduce the cwnd and drain the buffer.
+	 */
+	if (ca->curr_srrtt > roccet_xj && evaluate_srrtt &&
+	    sent_more_than_acked) {
+		roccet_congestion_event(sk, now);
+		return;
+	}
+
+	/* Terminates this function if cwnd is not fully utilized.
+	 * In mobile networks like 5G, this termination causes the
+	 * cwnd to be frozen at an excessively high value. This is
+	 * because slow start or HyStart massively exceed the available
+	 * bandwidth and leave the cwnd at an excessively high value.
+	 * The cwnd cannot therefore be fully utilized because it is
+	 * limited by the connection capacity.
+	 */
+	if (!tcp_is_cwnd_limited(sk) || sent_more_than_acked)
+		return;
+
+	bictcp_update(ca, tcp_snd_cwnd(tp), acked);
+	tcp_cong_avoid_ai(tp, max(1, ca->cnt), acked);
+}
+
+/* The Cubic ssthresh calculation is also used for ROCCET.
+ * Called before TCP-CC state changes to TCP_CA_Recovery, TCP_CA_CWR or
+ * TCP_CA_Loss. cwnd reduction is then handled in the roccet_state() callback.
+ */
+static u32 roccet_recalc_ssthresh(struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct roccettcp *ca = inet_csk_ca(sk);
+	u32 cwnd = tcp_snd_cwnd(tp);
+
+	/* In LAUNCH, we want no reduction on loss/ECN.
+	 * On ECN this is set later on in roccet_state()
+	 */
+	if (ca->state == LAUNCH)
+		return cwnd;
+
+	/* In min RTT probe, use the cwnd before the probe to not undershoot */
+	if (ca->state == RTT_PROBE)
+		cwnd = ca->cwnd_before_min_rtt_probe;
+
+	ca->epoch_start = 0;	/* end of epoch */
+
+	/* Wmax and fast convergence */
+	if (cwnd < ca->last_max_cwnd && fast_convergence)
+		ca->last_max_cwnd = (cwnd * (BICTCP_BETA_SCALE + beta))
+			/ (2 * BICTCP_BETA_SCALE);
+	else
+		ca->last_max_cwnd = cwnd;
+
+	return max((cwnd * beta) / BICTCP_BETA_SCALE, 2U);
+}
+
+/* Handle a recovery event and return the new cwnd.
+ */
+static u32 roccet_handle_recovery(struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct roccettcp *ca = inet_csk_ca(sk);
+	u32 cwnd = tcp_snd_cwnd(tp);
+
+	/* If a loss occurs in the refill phase of min RTT probing
+	 * we reduce the cwnd and abort the refill.
+	 */
+	if (ca->state == RTT_PROBE_REFILL)
+		ca->state = ORBITER;
+
+	/* In RTT_PROBE we don`t want to change state or immediately reduce
+	 * the cwnd.
+	 */
+	if (ca->state == RTT_PROBE) {
+		roccet_min_rtt_probe_ce(ca, cwnd);
+		return tcp_snd_cwnd(tp);
+	}
+
+	/* On loss in LAUNCH, enter ORBITER without a cwnd reduction. */
+	if (ca->state == LAUNCH) {
+		ca->state = ORBITER;
+		return cwnd;
+	}
+
+	return max((cwnd * beta) / BICTCP_BETA_SCALE, 2U);
+}
+
+/* Checks for state roccet-transitions and performs necessary state (re)sets.
+ * This is done in order to avoid the possibility of forgetting to correctly
+ * set a state when entering certain states.
+ *
+ * This is used whenever a state change is possible
+ * (e.g. in roccet_state() or roccet_control()).
+ */
+static void roccet_handle_state_transitions(struct roccettcp *ca,
+					    enum roccet_state prev_state,
+					    u32 now)
+{
+	if (ca->state == prev_state)
+		return;
+
+	/* When we exit LAUNCH we can be sure that we are no longer in the
+	 * initial_launch. Even on LAUNCH to LAUNCH transitions (on RTO).
+	 */
+	if (prev_state == LAUNCH)
+		ca->is_in_initial_launch = false;
+
+	/* Whenever we enter ORBITER, we need to schedule the next SRTT check.
+	 * This will be set before evaluating the next_srrtt_check_ts condition
+	 * as this is only done in ORBITER.
+	 */
+	if (ca->state == ORBITER)
+		ca->next_srrtt_check_ts = now + 5 * ca->curr_rtt;
+
+	/* Whenever we leave the min RTT probing states (and not just
+	 * transition between them), we want to reset the probing timers.
+	 */
+	if ((prev_state == RTT_PROBE_ENTER || prev_state == RTT_PROBE ||
+	     prev_state == RTT_PROBE_REFILL) &&
+	    (ca->state != RTT_PROBE && ca->state != RTT_PROBE_REFILL)) {
+		ca->probe_min_rtt_until = 0;
+		ca->refill_until = 0;
+	}
+}
+
+/* Handle different loss-states and perform adequate cwnd reductions.
+ */
+static void roccet_state(struct sock *sk, u8 new_state)
+{
+	struct roccettcp *ca = inet_csk_ca(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+	u32 cwnd;
+	u32 now = jiffies_to_usecs(tcp_jiffies32);
+	enum roccet_state prev_state = ca->state;
+
+	if (new_state == TCP_CA_Loss) {
+		roccet_reset(sk, ca);
+		tcp_snd_cwnd_set(tp, TCP_INIT_CWND);
+	} else if (new_state == TCP_CA_CWR) {
+		/* Handle CWR as ROCCET congestion event,
+		 * however afterwards always set Wmax to the current cwnd.
+		 */
+		cwnd = tcp_snd_cwnd(tp);
+		roccet_congestion_event(sk, now);
+		ca->last_max_cwnd = cwnd;
+	} else if (new_state == TCP_CA_Recovery) {
+		/* Directly reduce cwnd and rely on pacing */
+		cwnd = roccet_handle_recovery(sk);
+		tcp_snd_cwnd_set(tp, cwnd);
+	}
+
+	roccet_handle_state_transitions(ca, prev_state, now);
+}
+
+/* Update RTT samples and min RTT.
+ */
+static void roccet_acked(struct sock *sk, const struct ack_sample *sample)
+{
+	struct roccettcp *ca = inet_csk_ca(sk);
+	u32 delay;
+
+	/* Some calls are for duplicates without timestamps */
+	if (sample->rtt_us < 0)
+		return;
+
+	/* Discard delay samples right after fast recovery */
+	if (ca->epoch_start && (s32)(tcp_jiffies32 - ca->epoch_start) < HZ)
+		return;
+
+	delay = sample->rtt_us;
+
+	if (delay == 0)
+		delay = 1;
+
+	/* first call or link delay decreases */
+	if (ca->delay_min == 0 || (s32)(delay - ca->delay_min) < 0)
+		ca->delay_min = delay;
+
+	/* Get valid sample for roccet */
+	if (sample->rtt_us > 0) {
+		ca->last_rtt = ca->curr_rtt;
+		ca->curr_rtt = sample->rtt_us;
+	}
+}
+
+/* Custom Pacing Rate for ROCCET TCP.
+ * The code here is similar to the pacing rate adjustments in tcp_input.c
+ * tcp_cong_control(). In LAUNCH (slow start) we want a pacing of 200% and
+ * in ORBITER (congestion avoidance) we adjust the pacing to 100% and do not
+ * use the sysctl_tcp_pacing_ca_ratio.
+ */
+static void roccet_update_pacing_rate(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	u64 rate;
+
+	/* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
+	rate = (u64)tp->mss_cache * ((USEC_PER_SEC / 100) << 3);
+
+	/* current rate is (cwnd * mss) / srtt
+	 * In slow-start [1], set sk_pacing_rate to 200% the current rate.
+	 * Otherwise, set it to 100% the current rate.
+	 *
+	 * [1]: Normal Slow Start cond is (tp->snd_cwnd < tp->snd_ssthresh)
+	 *	 If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
+	 *	 end of slow start and should slow down.
+	 */
+	if (tcp_snd_cwnd(tp) < tp->snd_ssthresh / 2)
+		rate *= READ_ONCE
+			(sock_net(sk)->ipv4.sysctl_tcp_pacing_ss_ratio);
+	else
+		/* Pacing rate of 100%
+		 * (instead of ipv4.sysctl_tcp_pacing_ca_ratio)
+		 */
+		rate *= 100;
+
+	rate *= max(tcp_snd_cwnd(tp), tp->packets_out);
+
+	if (likely(tp->srtt_us))
+		do_div(rate, tp->srtt_us);
+
+	/* WRITE_ONCE() is needed because sch_fq fetches sk_pacing_rate
+	 * without any lock. We want to make sure compiler won't store
+	 * intermediate values in this location.
+	 */
+	WRITE_ONCE(sk->sk_pacing_rate,
+		   min_t(u64, rate, READ_ONCE(sk->sk_max_pacing_rate)));
+}
+
+static void roccet_drain_update(struct sock *sk, u32 now)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct roccettcp *ca = inet_csk_ca(sk);
+
+	if (ca->roccet_last_event_time_us &&
+	    time_after32(now, ca->roccet_last_event_time_us +
+			 100 * USEC_PER_MSEC)) {
+		if (tcp_in_slow_start(tp))
+			ca->state = LAUNCH;
+		else
+			ca->state = ORBITER;
+	}
+}
+
+static void roccet_control(struct sock *sk, u32 ack, int flag,
+			   const struct rate_sample *rs)
+{
+	struct roccettcp *ca = inet_csk_ca(sk);
+
+	u32 now = jiffies_to_usecs(tcp_jiffies32);
+	enum roccet_state prev_state = ca->state;
+
+	/* Update ack rate. Even on no new acks/sacks. */
+	update_ack_rate(ca, rs->acked_sacked, now);
+	/* Only update RTT metrics if we have new acks/sacks in order to keep
+	 * EWMA from running multiple times for no new acks.
+	 */
+	if (rs->acked_sacked > 0) {
+		update_min_rtt(ca);
+		update_srrtt(ca);
+	}
+
+	/* Evaluate roccet state */
+	switch (ca->state) {
+	case LAUNCH:
+		roccet_launch_update(sk, rs->acked_sacked);
+		break;
+	case ORBITER:
+		roccet_orbiter_update(sk, rs->acked_sacked);
+		break;
+	case DRAIN:
+		/* In DRAIN the cwnd should not be increased */
+		roccet_drain_update(sk, now);
+		break;
+	case RTT_PROBE_ENTER:
+		roccet_enter_min_rtt_probe(sk, now);
+		break;
+	case RTT_PROBE:
+		roccet_min_rtt_probe(sk, now);
+		break;
+	case RTT_PROBE_REFILL:
+		roccet_rtt_probe_refill(ca, now);
+		break;
+	default:
+		pr_err_once("TCP ROCCET: Invalid state %d", ca->state);
+	}
+
+	roccet_handle_state_transitions(ca, prev_state, now);
+
+	roccet_update_pacing_rate(sk);
+
+	if (tcp_is_cwnd_limited(sk))
+		ca->initial_limit_reached = true;
+}
+
+static struct tcp_congestion_ops roccet_tcp __read_mostly = {
+	.init = roccet_init,
+	.ssthresh = roccet_recalc_ssthresh,
+	.set_state = roccet_state,
+	.undo_cwnd = tcp_reno_undo_cwnd,
+	.cwnd_event_tx_start = roccet_cwnd_event_tx_start,
+	.pkts_acked = roccet_acked,
+	.cong_control = roccet_control,
+	.owner = THIS_MODULE,
+	.name = "roccet",
+};
+
+static int __init roccet_register(void)
+{
+	int param_err;
+
+	BUILD_BUG_ON(sizeof(struct roccettcp) > ICSK_CA_PRIV_SIZE);
+
+	/* Check for valid parameter ranges and then precompute factors */
+	param_err = param_check();
+
+	if (param_err)
+		return param_err;
+
+	param_precompute();
+
+	return tcp_register_congestion_control(&roccet_tcp);
+}
+
+static void __exit roccet_unregister(void)
+{
+	tcp_unregister_congestion_control(&roccet_tcp);
+}
+
+module_init(roccet_register);
+module_exit(roccet_unregister);
+
+MODULE_AUTHOR("Lukas Prause, Tim Füchsel");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("ROCCET TCP");