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Commit 9e36ced6 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'tcp-cong-undo_cwnd-mandatory' 



Florian Westphal says:

====================
tcp: make undo_cwnd mandatory for congestion modules

highspeed, illinois, scalable, veno and yeah congestion control algorithms
don't provide a 'cwnd_undo' function.  This makes the stack default to a
'reno undo' which doubles cwnd.  However, the ssthresh implementation of
these algorithms do not halve the slowstart threshold. This causes similar
issue as the one fixed for dctcp in ce6dd233 ("dctcp: avoid bogus
doubling of cwnd after loss").

In light of this it seems better to remove the fallback and make undo_cwnd
mandatory.

First patch fixes those spots where reno undo seems incorrect by providing
.cwnd_undo functions, second patch removes the fallback.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 2fcb58ab e9799183

include/net/tcp.h

+1 −0
Original line number Diff line number Diff line
@@ -958,6 +958,7 @@ u32 tcp_slow_start(struct tcp_sock *tp, u32 acked); 
void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);



u32 tcp_reno_ssthresh(struct sock *sk);

u32 tcp_reno_undo_cwnd(struct sock *sk);

void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);

extern struct tcp_congestion_ops tcp_reno;

net/ipv4/tcp_cong.c

+12 −2
Original line number Diff line number Diff line
@@ -68,8 +68,9 @@ int tcp_register_congestion_control(struct tcp_congestion_ops *ca) 
{

	int ret = 0;



	/* all algorithms must implement ssthresh and cong_avoid ops */

	if (!ca->ssthresh || !(ca->cong_avoid || ca->cong_control)) {

	/* 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;

	}
@@ -441,10 +442,19 @@ u32 tcp_reno_ssthresh(struct sock *sk) 
}

EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);



u32 tcp_reno_undo_cwnd(struct sock *sk)

{

	const struct tcp_sock *tp = tcp_sk(sk);



	return max(tp->snd_cwnd, tp->snd_ssthresh << 1);

}

EXPORT_SYMBOL_GPL(tcp_reno_undo_cwnd);



struct tcp_congestion_ops tcp_reno = {

	.flags		= TCP_CONG_NON_RESTRICTED,

	.name		= "reno",

	.owner		= THIS_MODULE,

	.ssthresh	= tcp_reno_ssthresh,

	.cong_avoid	= tcp_reno_cong_avoid,

	.undo_cwnd	= tcp_reno_undo_cwnd,

};

net/ipv4/tcp_dctcp.c

+1 −0
Original line number Diff line number Diff line
@@ -342,6 +342,7 @@ static struct tcp_congestion_ops dctcp __read_mostly = { 
static struct tcp_congestion_ops dctcp_reno __read_mostly = {

	.ssthresh	= tcp_reno_ssthresh,

	.cong_avoid	= tcp_reno_cong_avoid,

	.undo_cwnd	= tcp_reno_undo_cwnd,

	.get_info	= dctcp_get_info,

	.owner		= THIS_MODULE,

	.name		= "dctcp-reno",

net/ipv4/tcp_highspeed.c

+10 −1
Original line number Diff line number Diff line
@@ -94,6 +94,7 @@ static const struct hstcp_aimd_val { 


struct hstcp {

	u32	ai;

	u32	loss_cwnd;

};



static void hstcp_init(struct sock *sk)
@@ -150,16 +151,24 @@ static void hstcp_cong_avoid(struct sock *sk, u32 ack, u32 acked) 
static u32 hstcp_ssthresh(struct sock *sk)

{

	const struct tcp_sock *tp = tcp_sk(sk);

	const struct hstcp *ca = inet_csk_ca(sk);

	struct hstcp *ca = inet_csk_ca(sk);



	ca->loss_cwnd = tp->snd_cwnd;

	/* Do multiplicative decrease */

	return max(tp->snd_cwnd - ((tp->snd_cwnd * hstcp_aimd_vals[ca->ai].md) >> 8), 2U);

}



static u32 hstcp_cwnd_undo(struct sock *sk)

{

	const struct hstcp *ca = inet_csk_ca(sk);



	return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);

}



static struct tcp_congestion_ops tcp_highspeed __read_mostly = {

	.init		= hstcp_init,

	.ssthresh	= hstcp_ssthresh,

	.undo_cwnd	= hstcp_cwnd_undo,

	.cong_avoid	= hstcp_cong_avoid,



	.owner		= THIS_MODULE,

net/ipv4/tcp_hybla.c

+1 −0
Original line number Diff line number Diff line
@@ -166,6 +166,7 @@ static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 acked) 
static struct tcp_congestion_ops tcp_hybla __read_mostly = {

	.init		= hybla_init,

	.ssthresh	= tcp_reno_ssthresh,

	.undo_cwnd	= tcp_reno_undo_cwnd,

	.cong_avoid	= hybla_cong_avoid,

	.set_state	= hybla_state,