forked from mirrors/linux
		
	tcp: add CDG congestion control
CAIA Delay-Gradient (CDG) is a TCP congestion control that modifies
the TCP sender in order to [1]:
  o Use the delay gradient as a congestion signal.
  o Back off with an average probability that is independent of the RTT.
  o Coexist with flows that use loss-based congestion control, i.e.,
    flows that are unresponsive to the delay signal.
  o Tolerate packet loss unrelated to congestion. (Disabled by default.)
Its FreeBSD implementation was presented for the ICCRG in July 2012;
slides are available at http://www.ietf.org/proceedings/84/iccrg.html
Running the experiment scenarios in [1] suggests that our implementation
achieves more goodput compared with FreeBSD 10.0 senders, although it also
causes more queueing delay for a given backoff factor.
The loss tolerance heuristic is disabled by default due to safety concerns
for its use in the Internet [2, p. 45-46].
We use a variant of the Hybrid Slow start algorithm in tcp_cubic to reduce
the probability of slow start overshoot.
[1] D.A. Hayes and G. Armitage. "Revisiting TCP congestion control using
    delay gradients." In Networking 2011, pages 328-341. Springer, 2011.
[2] K.K. Jonassen. "Implementing CAIA Delay-Gradient in Linux."
    MSc thesis. Department of Informatics, University of Oslo, 2015.
Cc: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: David Hayes <davihay@ifi.uio.no>
Cc: Andreas Petlund <apetlund@simula.no>
Cc: Dave Taht <dave.taht@bufferbloat.net>
Cc: Nicolas Kuhn <nicolas.kuhn@telecom-bretagne.eu>
Signed-off-by: Kenneth Klette Jonassen <kennetkl@ifi.uio.no>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
			
			
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		|  | @ -615,6 +615,22 @@ config TCP_CONG_DCTCP | |||
| 	For further details see: | ||||
| 	  http://simula.stanford.edu/~alizade/Site/DCTCP_files/dctcp-final.pdf | ||||
| 
 | ||||
| config TCP_CONG_CDG | ||||
| 	tristate "CAIA Delay-Gradient (CDG)" | ||||
| 	default n | ||||
| 	---help--- | ||||
| 	CAIA Delay-Gradient (CDG) is a TCP congestion control that modifies | ||||
| 	the TCP sender in order to: | ||||
| 
 | ||||
| 	  o Use the delay gradient as a congestion signal. | ||||
| 	  o Back off with an average probability that is independent of the RTT. | ||||
| 	  o Coexist with flows that use loss-based congestion control. | ||||
| 	  o Tolerate packet loss unrelated to congestion. | ||||
| 
 | ||||
| 	For further details see: | ||||
| 	  D.A. Hayes and G. Armitage. "Revisiting TCP congestion control using | ||||
| 	  delay gradients." In Networking 2011. Preprint: http://goo.gl/No3vdg | ||||
| 
 | ||||
| choice | ||||
| 	prompt "Default TCP congestion control" | ||||
| 	default DEFAULT_CUBIC | ||||
|  | @ -646,6 +662,9 @@ choice | |||
| 	config DEFAULT_DCTCP | ||||
| 		bool "DCTCP" if TCP_CONG_DCTCP=y | ||||
| 
 | ||||
| 	config DEFAULT_CDG | ||||
| 		bool "CDG" if TCP_CONG_CDG=y | ||||
| 
 | ||||
| 	config DEFAULT_RENO | ||||
| 		bool "Reno" | ||||
| endchoice | ||||
|  | @ -668,6 +687,7 @@ config DEFAULT_TCP_CONG | |||
| 	default "veno" if DEFAULT_VENO | ||||
| 	default "reno" if DEFAULT_RENO | ||||
| 	default "dctcp" if DEFAULT_DCTCP | ||||
| 	default "cdg" if DEFAULT_CDG | ||||
| 	default "cubic" | ||||
| 
 | ||||
| config TCP_MD5SIG | ||||
|  |  | |||
|  | @ -42,6 +42,7 @@ obj-$(CONFIG_INET_TCP_DIAG) += tcp_diag.o | |||
| obj-$(CONFIG_INET_UDP_DIAG) += udp_diag.o | ||||
| obj-$(CONFIG_NET_TCPPROBE) += tcp_probe.o | ||||
| obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o | ||||
| obj-$(CONFIG_TCP_CONG_CDG) += tcp_cdg.o | ||||
| obj-$(CONFIG_TCP_CONG_CUBIC) += tcp_cubic.o | ||||
| obj-$(CONFIG_TCP_CONG_DCTCP) += tcp_dctcp.o | ||||
| obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o | ||||
|  |  | |||
							
								
								
									
										433
									
								
								net/ipv4/tcp_cdg.c
									
									
									
									
									
										Normal file
									
								
							
							
						
						
									
										433
									
								
								net/ipv4/tcp_cdg.c
									
									
									
									
									
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							|  | @ -0,0 +1,433 @@ | |||
| /*
 | ||||
|  * CAIA Delay-Gradient (CDG) congestion control | ||||
|  * | ||||
|  * This implementation is based on the paper: | ||||
|  *   D.A. Hayes and G. Armitage. "Revisiting TCP congestion control using | ||||
|  *   delay gradients." In IFIP Networking, pages 328-341. Springer, 2011. | ||||
|  * | ||||
|  * Scavenger traffic (Less-than-Best-Effort) should disable coexistence | ||||
|  * heuristics using parameters use_shadow=0 and use_ineff=0. | ||||
|  * | ||||
|  * Parameters window, backoff_beta, and backoff_factor are crucial for | ||||
|  * throughput and delay. Future work is needed to determine better defaults, | ||||
|  * and to provide guidelines for use in different environments/contexts. | ||||
|  * | ||||
|  * Except for window, knobs are configured via /sys/module/tcp_cdg/parameters/. | ||||
|  * Parameter window is only configurable when loading tcp_cdg as a module. | ||||
|  * | ||||
|  * Notable differences from paper/FreeBSD: | ||||
|  *   o Using Hybrid Slow start and Proportional Rate Reduction. | ||||
|  *   o Add toggle for shadow window mechanism. Suggested by David Hayes. | ||||
|  *   o Add toggle for non-congestion loss tolerance. | ||||
|  *   o Scaling parameter G is changed to a backoff factor; | ||||
|  *     conversion is given by: backoff_factor = 1000/(G * window). | ||||
|  *   o Limit shadow window to 2 * cwnd, or to cwnd when application limited. | ||||
|  *   o More accurate e^-x. | ||||
|  */ | ||||
| #include <linux/kernel.h> | ||||
| #include <linux/random.h> | ||||
| #include <linux/module.h> | ||||
| #include <net/tcp.h> | ||||
| 
 | ||||
| #define HYSTART_ACK_TRAIN	1 | ||||
| #define HYSTART_DELAY		2 | ||||
| 
 | ||||
| static int window __read_mostly = 8; | ||||
| static unsigned int backoff_beta __read_mostly = 0.7071 * 1024; /* sqrt 0.5 */ | ||||
| static unsigned int backoff_factor __read_mostly = 42; | ||||
| static unsigned int hystart_detect __read_mostly = 3; | ||||
| static unsigned int use_ineff __read_mostly = 5; | ||||
| static bool use_shadow __read_mostly = true; | ||||
| static bool use_tolerance __read_mostly; | ||||
| 
 | ||||
| module_param(window, int, 0444); | ||||
| MODULE_PARM_DESC(window, "gradient window size (power of two <= 256)"); | ||||
| module_param(backoff_beta, uint, 0644); | ||||
| MODULE_PARM_DESC(backoff_beta, "backoff beta (0-1024)"); | ||||
| module_param(backoff_factor, uint, 0644); | ||||
| MODULE_PARM_DESC(backoff_factor, "backoff probability scale factor"); | ||||
| module_param(hystart_detect, uint, 0644); | ||||
| MODULE_PARM_DESC(hystart_detect, "use Hybrid Slow start " | ||||
| 		 "(0: disabled, 1: ACK train, 2: delay threshold, 3: both)"); | ||||
| module_param(use_ineff, uint, 0644); | ||||
| MODULE_PARM_DESC(use_ineff, "use ineffectual backoff detection (threshold)"); | ||||
| module_param(use_shadow, bool, 0644); | ||||
| MODULE_PARM_DESC(use_shadow, "use shadow window heuristic"); | ||||
| module_param(use_tolerance, bool, 0644); | ||||
| MODULE_PARM_DESC(use_tolerance, "use loss tolerance heuristic"); | ||||
| 
 | ||||
| struct minmax { | ||||
| 	union { | ||||
| 		struct { | ||||
| 			s32 min; | ||||
| 			s32 max; | ||||
| 		}; | ||||
| 		u64 v64; | ||||
| 	}; | ||||
| }; | ||||
| 
 | ||||
| enum cdg_state { | ||||
| 	CDG_UNKNOWN = 0, | ||||
| 	CDG_NONFULL = 1, | ||||
| 	CDG_FULL    = 2, | ||||
| 	CDG_BACKOFF = 3, | ||||
| }; | ||||
| 
 | ||||
| struct cdg { | ||||
| 	struct minmax rtt; | ||||
| 	struct minmax rtt_prev; | ||||
| 	struct minmax *gradients; | ||||
| 	struct minmax gsum; | ||||
| 	bool gfilled; | ||||
| 	u8  tail; | ||||
| 	u8  state; | ||||
| 	u8  delack; | ||||
| 	u32 rtt_seq; | ||||
| 	u32 undo_cwnd; | ||||
| 	u32 shadow_wnd; | ||||
| 	u16 backoff_cnt; | ||||
| 	u16 sample_cnt; | ||||
| 	s32 delay_min; | ||||
| 	u32 last_ack; | ||||
| 	u32 round_start; | ||||
| }; | ||||
| 
 | ||||
| /**
 | ||||
|  * nexp_u32 - negative base-e exponential | ||||
|  * @ux: x in units of micro | ||||
|  * | ||||
|  * Returns exp(ux * -1e-6) * U32_MAX. | ||||
|  */ | ||||
| static u32 __pure nexp_u32(u32 ux) | ||||
| { | ||||
| 	static const u16 v[] = { | ||||
| 		/* exp(-x)*65536-1 for x = 0, 0.000256, 0.000512, ... */ | ||||
| 		65535, | ||||
| 		65518, 65501, 65468, 65401, 65267, 65001, 64470, 63422, | ||||
| 		61378, 57484, 50423, 38795, 22965, 8047,  987,   14, | ||||
| 	}; | ||||
| 	u32 msb = ux >> 8; | ||||
| 	u32 res; | ||||
| 	int i; | ||||
| 
 | ||||
| 	/* Cut off when ux >= 2^24 (actual result is <= 222/U32_MAX). */ | ||||
| 	if (msb > U16_MAX) | ||||
| 		return 0; | ||||
| 
 | ||||
| 	/* Scale first eight bits linearly: */ | ||||
| 	res = U32_MAX - (ux & 0xff) * (U32_MAX / 1000000); | ||||
| 
 | ||||
| 	/* Obtain e^(x + y + ...) by computing e^x * e^y * ...: */ | ||||
| 	for (i = 1; msb; i++, msb >>= 1) { | ||||
| 		u32 y = v[i & -(msb & 1)] + U32_C(1); | ||||
| 
 | ||||
| 		res = ((u64)res * y) >> 16; | ||||
| 	} | ||||
| 
 | ||||
| 	return res; | ||||
| } | ||||
| 
 | ||||
| /* Based on the HyStart algorithm (by Ha et al.) that is implemented in
 | ||||
|  * tcp_cubic. Differences/experimental changes: | ||||
|  *   o Using Hayes' delayed ACK filter. | ||||
|  *   o Using a usec clock for the ACK train. | ||||
|  *   o Reset ACK train when application limited. | ||||
|  *   o Invoked at any cwnd (i.e. also when cwnd < 16). | ||||
|  *   o Invoked only when cwnd < ssthresh (i.e. not when cwnd == ssthresh). | ||||
|  */ | ||||
| static void tcp_cdg_hystart_update(struct sock *sk) | ||||
| { | ||||
| 	struct cdg *ca = inet_csk_ca(sk); | ||||
| 	struct tcp_sock *tp = tcp_sk(sk); | ||||
| 
 | ||||
| 	ca->delay_min = min_not_zero(ca->delay_min, ca->rtt.min); | ||||
| 	if (ca->delay_min == 0) | ||||
| 		return; | ||||
| 
 | ||||
| 	if (hystart_detect & HYSTART_ACK_TRAIN) { | ||||
| 		u32 now_us = local_clock() / NSEC_PER_USEC; | ||||
| 
 | ||||
| 		if (ca->last_ack == 0 || !tcp_is_cwnd_limited(sk)) { | ||||
| 			ca->last_ack = now_us; | ||||
| 			ca->round_start = now_us; | ||||
| 		} else if (before(now_us, ca->last_ack + 3000)) { | ||||
| 			u32 base_owd = max(ca->delay_min / 2U, 125U); | ||||
| 
 | ||||
| 			ca->last_ack = now_us; | ||||
| 			if (after(now_us, ca->round_start + base_owd)) { | ||||
| 				NET_INC_STATS_BH(sock_net(sk), | ||||
| 						 LINUX_MIB_TCPHYSTARTTRAINDETECT); | ||||
| 				NET_ADD_STATS_BH(sock_net(sk), | ||||
| 						 LINUX_MIB_TCPHYSTARTTRAINCWND, | ||||
| 						 tp->snd_cwnd); | ||||
| 				tp->snd_ssthresh = tp->snd_cwnd; | ||||
| 				return; | ||||
| 			} | ||||
| 		} | ||||
| 	} | ||||
| 
 | ||||
| 	if (hystart_detect & HYSTART_DELAY) { | ||||
| 		if (ca->sample_cnt < 8) { | ||||
| 			ca->sample_cnt++; | ||||
| 		} else { | ||||
| 			s32 thresh = max(ca->delay_min + ca->delay_min / 8U, | ||||
| 					 125U); | ||||
| 
 | ||||
| 			if (ca->rtt.min > thresh) { | ||||
| 				NET_INC_STATS_BH(sock_net(sk), | ||||
| 						 LINUX_MIB_TCPHYSTARTDELAYDETECT); | ||||
| 				NET_ADD_STATS_BH(sock_net(sk), | ||||
| 						 LINUX_MIB_TCPHYSTARTDELAYCWND, | ||||
| 						 tp->snd_cwnd); | ||||
| 				tp->snd_ssthresh = tp->snd_cwnd; | ||||
| 			} | ||||
| 		} | ||||
| 	} | ||||
| } | ||||
| 
 | ||||
| static s32 tcp_cdg_grad(struct cdg *ca) | ||||
| { | ||||
| 	s32 gmin = ca->rtt.min - ca->rtt_prev.min; | ||||
| 	s32 gmax = ca->rtt.max - ca->rtt_prev.max; | ||||
| 	s32 grad; | ||||
| 
 | ||||
| 	if (ca->gradients) { | ||||
| 		ca->gsum.min += gmin - ca->gradients[ca->tail].min; | ||||
| 		ca->gsum.max += gmax - ca->gradients[ca->tail].max; | ||||
| 		ca->gradients[ca->tail].min = gmin; | ||||
| 		ca->gradients[ca->tail].max = gmax; | ||||
| 		ca->tail = (ca->tail + 1) & (window - 1); | ||||
| 		gmin = ca->gsum.min; | ||||
| 		gmax = ca->gsum.max; | ||||
| 	} | ||||
| 
 | ||||
| 	/* We keep sums to ignore gradients during cwnd reductions;
 | ||||
| 	 * the paper's smoothed gradients otherwise simplify to: | ||||
| 	 * (rtt_latest - rtt_oldest) / window. | ||||
| 	 * | ||||
| 	 * We also drop division by window here. | ||||
| 	 */ | ||||
| 	grad = gmin > 0 ? gmin : gmax; | ||||
| 
 | ||||
| 	/* Extrapolate missing values in gradient window: */ | ||||
| 	if (!ca->gfilled) { | ||||
| 		if (!ca->gradients && window > 1) | ||||
| 			grad *= window; /* Memory allocation failed. */ | ||||
| 		else if (ca->tail == 0) | ||||
| 			ca->gfilled = true; | ||||
| 		else | ||||
| 			grad = (grad * window) / (int)ca->tail; | ||||
| 	} | ||||
| 
 | ||||
| 	/* Backoff was effectual: */ | ||||
| 	if (gmin <= -32 || gmax <= -32) | ||||
| 		ca->backoff_cnt = 0; | ||||
| 
 | ||||
| 	if (use_tolerance) { | ||||
| 		/* Reduce small variations to zero: */ | ||||
| 		gmin = DIV_ROUND_CLOSEST(gmin, 64); | ||||
| 		gmax = DIV_ROUND_CLOSEST(gmax, 64); | ||||
| 
 | ||||
| 		if (gmin > 0 && gmax <= 0) | ||||
| 			ca->state = CDG_FULL; | ||||
| 		else if ((gmin > 0 && gmax > 0) || gmax < 0) | ||||
| 			ca->state = CDG_NONFULL; | ||||
| 	} | ||||
| 	return grad; | ||||
| } | ||||
| 
 | ||||
| static bool tcp_cdg_backoff(struct sock *sk, u32 grad) | ||||
| { | ||||
| 	struct cdg *ca = inet_csk_ca(sk); | ||||
| 	struct tcp_sock *tp = tcp_sk(sk); | ||||
| 
 | ||||
| 	if (prandom_u32() <= nexp_u32(grad * backoff_factor)) | ||||
| 		return false; | ||||
| 
 | ||||
| 	if (use_ineff) { | ||||
| 		ca->backoff_cnt++; | ||||
| 		if (ca->backoff_cnt > use_ineff) | ||||
| 			return false; | ||||
| 	} | ||||
| 
 | ||||
| 	ca->shadow_wnd = max(ca->shadow_wnd, tp->snd_cwnd); | ||||
| 	ca->state = CDG_BACKOFF; | ||||
| 	tcp_enter_cwr(sk); | ||||
| 	return true; | ||||
| } | ||||
| 
 | ||||
| /* Not called in CWR or Recovery state. */ | ||||
| static void tcp_cdg_cong_avoid(struct sock *sk, u32 ack, u32 acked) | ||||
| { | ||||
| 	struct cdg *ca = inet_csk_ca(sk); | ||||
| 	struct tcp_sock *tp = tcp_sk(sk); | ||||
| 	u32 prior_snd_cwnd; | ||||
| 	u32 incr; | ||||
| 
 | ||||
| 	if (tp->snd_cwnd < tp->snd_ssthresh && hystart_detect) | ||||
| 		tcp_cdg_hystart_update(sk); | ||||
| 
 | ||||
| 	if (after(ack, ca->rtt_seq) && ca->rtt.v64) { | ||||
| 		s32 grad = 0; | ||||
| 
 | ||||
| 		if (ca->rtt_prev.v64) | ||||
| 			grad = tcp_cdg_grad(ca); | ||||
| 		ca->rtt_seq = tp->snd_nxt; | ||||
| 		ca->rtt_prev = ca->rtt; | ||||
| 		ca->rtt.v64 = 0; | ||||
| 		ca->last_ack = 0; | ||||
| 		ca->sample_cnt = 0; | ||||
| 
 | ||||
| 		if (grad > 0 && tcp_cdg_backoff(sk, grad)) | ||||
| 			return; | ||||
| 	} | ||||
| 
 | ||||
| 	if (!tcp_is_cwnd_limited(sk)) { | ||||
| 		ca->shadow_wnd = min(ca->shadow_wnd, tp->snd_cwnd); | ||||
| 		return; | ||||
| 	} | ||||
| 
 | ||||
| 	prior_snd_cwnd = tp->snd_cwnd; | ||||
| 	tcp_reno_cong_avoid(sk, ack, acked); | ||||
| 
 | ||||
| 	incr = tp->snd_cwnd - prior_snd_cwnd; | ||||
| 	ca->shadow_wnd = max(ca->shadow_wnd, ca->shadow_wnd + incr); | ||||
| } | ||||
| 
 | ||||
| static void tcp_cdg_acked(struct sock *sk, u32 num_acked, s32 rtt_us) | ||||
| { | ||||
| 	struct cdg *ca = inet_csk_ca(sk); | ||||
| 	struct tcp_sock *tp = tcp_sk(sk); | ||||
| 
 | ||||
| 	if (rtt_us <= 0) | ||||
| 		return; | ||||
| 
 | ||||
| 	/* A heuristic for filtering delayed ACKs, adapted from:
 | ||||
| 	 * D.A. Hayes. "Timing enhancements to the FreeBSD kernel to support | ||||
| 	 * delay and rate based TCP mechanisms." TR 100219A. CAIA, 2010. | ||||
| 	 */ | ||||
| 	if (tp->sacked_out == 0) { | ||||
| 		if (num_acked == 1 && ca->delack) { | ||||
| 			/* A delayed ACK is only used for the minimum if it is
 | ||||
| 			 * provenly lower than an existing non-zero minimum. | ||||
| 			 */ | ||||
| 			ca->rtt.min = min(ca->rtt.min, rtt_us); | ||||
| 			ca->delack--; | ||||
| 			return; | ||||
| 		} else if (num_acked > 1 && ca->delack < 5) { | ||||
| 			ca->delack++; | ||||
| 		} | ||||
| 	} | ||||
| 
 | ||||
| 	ca->rtt.min = min_not_zero(ca->rtt.min, rtt_us); | ||||
| 	ca->rtt.max = max(ca->rtt.max, rtt_us); | ||||
| } | ||||
| 
 | ||||
| static u32 tcp_cdg_ssthresh(struct sock *sk) | ||||
| { | ||||
| 	struct cdg *ca = inet_csk_ca(sk); | ||||
| 	struct tcp_sock *tp = tcp_sk(sk); | ||||
| 
 | ||||
| 	ca->undo_cwnd = tp->snd_cwnd; | ||||
| 
 | ||||
| 	if (ca->state == CDG_BACKOFF) | ||||
| 		return max(2U, (tp->snd_cwnd * min(1024U, backoff_beta)) >> 10); | ||||
| 
 | ||||
| 	if (ca->state == CDG_NONFULL && use_tolerance) | ||||
| 		return tp->snd_cwnd; | ||||
| 
 | ||||
| 	ca->shadow_wnd = min(ca->shadow_wnd >> 1, tp->snd_cwnd); | ||||
| 	if (use_shadow) | ||||
| 		return max3(2U, ca->shadow_wnd, tp->snd_cwnd >> 1); | ||||
| 	return max(2U, tp->snd_cwnd >> 1); | ||||
| } | ||||
| 
 | ||||
| static u32 tcp_cdg_undo_cwnd(struct sock *sk) | ||||
| { | ||||
| 	struct cdg *ca = inet_csk_ca(sk); | ||||
| 
 | ||||
| 	return max(tcp_sk(sk)->snd_cwnd, ca->undo_cwnd); | ||||
| } | ||||
| 
 | ||||
| static void tcp_cdg_cwnd_event(struct sock *sk, const enum tcp_ca_event ev) | ||||
| { | ||||
| 	struct cdg *ca = inet_csk_ca(sk); | ||||
| 	struct tcp_sock *tp = tcp_sk(sk); | ||||
| 	struct minmax *gradients; | ||||
| 
 | ||||
| 	switch (ev) { | ||||
| 	case CA_EVENT_CWND_RESTART: | ||||
| 		gradients = ca->gradients; | ||||
| 		if (gradients) | ||||
| 			memset(gradients, 0, window * sizeof(gradients[0])); | ||||
| 		memset(ca, 0, sizeof(*ca)); | ||||
| 
 | ||||
| 		ca->gradients = gradients; | ||||
| 		ca->rtt_seq = tp->snd_nxt; | ||||
| 		ca->shadow_wnd = tp->snd_cwnd; | ||||
| 		break; | ||||
| 	case CA_EVENT_COMPLETE_CWR: | ||||
| 		ca->state = CDG_UNKNOWN; | ||||
| 		ca->rtt_seq = tp->snd_nxt; | ||||
| 		ca->rtt_prev = ca->rtt; | ||||
| 		ca->rtt.v64 = 0; | ||||
| 		break; | ||||
| 	default: | ||||
| 		break; | ||||
| 	} | ||||
| } | ||||
| 
 | ||||
| static void tcp_cdg_init(struct sock *sk) | ||||
| { | ||||
| 	struct cdg *ca = inet_csk_ca(sk); | ||||
| 	struct tcp_sock *tp = tcp_sk(sk); | ||||
| 
 | ||||
| 	/* We silently fall back to window = 1 if allocation fails. */ | ||||
| 	if (window > 1) | ||||
| 		ca->gradients = kcalloc(window, sizeof(ca->gradients[0]), | ||||
| 					GFP_NOWAIT | __GFP_NOWARN); | ||||
| 	ca->rtt_seq = tp->snd_nxt; | ||||
| 	ca->shadow_wnd = tp->snd_cwnd; | ||||
| } | ||||
| 
 | ||||
| static void tcp_cdg_release(struct sock *sk) | ||||
| { | ||||
| 	struct cdg *ca = inet_csk_ca(sk); | ||||
| 
 | ||||
| 	kfree(ca->gradients); | ||||
| } | ||||
| 
 | ||||
| struct tcp_congestion_ops tcp_cdg __read_mostly = { | ||||
| 	.cong_avoid = tcp_cdg_cong_avoid, | ||||
| 	.cwnd_event = tcp_cdg_cwnd_event, | ||||
| 	.pkts_acked = tcp_cdg_acked, | ||||
| 	.undo_cwnd = tcp_cdg_undo_cwnd, | ||||
| 	.ssthresh = tcp_cdg_ssthresh, | ||||
| 	.release = tcp_cdg_release, | ||||
| 	.init = tcp_cdg_init, | ||||
| 	.owner = THIS_MODULE, | ||||
| 	.name = "cdg", | ||||
| }; | ||||
| 
 | ||||
| static int __init tcp_cdg_register(void) | ||||
| { | ||||
| 	if (backoff_beta > 1024 || window < 1 || window > 256) | ||||
| 		return -ERANGE; | ||||
| 	if (!is_power_of_2(window)) | ||||
| 		return -EINVAL; | ||||
| 
 | ||||
| 	BUILD_BUG_ON(sizeof(struct cdg) > ICSK_CA_PRIV_SIZE); | ||||
| 	tcp_register_congestion_control(&tcp_cdg); | ||||
| 	return 0; | ||||
| } | ||||
| 
 | ||||
| static void __exit tcp_cdg_unregister(void) | ||||
| { | ||||
| 	tcp_unregister_congestion_control(&tcp_cdg); | ||||
| } | ||||
| 
 | ||||
| module_init(tcp_cdg_register); | ||||
| module_exit(tcp_cdg_unregister); | ||||
| MODULE_AUTHOR("Kenneth Klette Jonassen"); | ||||
| MODULE_LICENSE("GPL"); | ||||
| MODULE_DESCRIPTION("TCP CDG"); | ||||
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	 Kenneth Klette Jonassen
						Kenneth Klette Jonassen