Date:	Tue,  3 Jun 2014 23:57:08 +0100
From:	raffaello@....abdn.ac.uk
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, Raffaello Secchi <r.secchi@...il.com>,
	Raffaello Secchi <raffaello@....abdn.ac.uk>
Subject: [PATCH RFC] Resubmitting patch - new-CWV for Linux

From: Raffaello Secchi <r.secchi@...il.com>

One file was missing.

Thanks Vlad.

Raffaello


---
 include/linux/tcp.h        |   13 ++++
 include/net/tcp.h          |   14 ++++-
 net/ipv4/Makefile          |    2 +-
 net/ipv4/sysctl_net_ipv4.c |    7 +++
 net/ipv4/tcp_cong.c        |   13 +++-
 net/ipv4/tcp_input.c       |   20 +++++++
 net/ipv4/tcp_newcwv.c      |  140 ++++++++++++++++++++++++++++++++++++++++++++
 net/ipv4/tcp_output.c      |    3 +
 8 files changed, 207 insertions(+), 5 deletions(-)
 create mode 100644 net/ipv4/tcp_newcwv.c

Signed-off-by: Raffaello Secchi <raffaello@....abdn.ac.uk>
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 2399468..fb82343 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -323,6 +323,19 @@ struct tcp_sock {
 	 * socket. Used to retransmit SYNACKs etc.
 	 */
 	struct request_sock *fastopen_rsk;
+
+/* TCP newcwv related information */
+	u32 psample[4];		/* pipeACK samples circular buffer */
+	u32 time_stamp[4];
+	u32 head;		/* index for psample buffer */
+
+	u32 pipeack;		/* pipeACK value after filtering */
+	u32 loss_flight_size;	/* flightsize at loss detection */
+	u32 prior_retrans;	/* Retransmission before going into FR */
+	u32 prev_snd_una;	/* snd_una of last record */
+	u32 prev_snd_nxt;	/* snd_nxt of last record */
+	u32 cwnd_valid_ts;	/* last time cwnd was found valid */
+
 };
 
 enum tsq_flags {
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 87d8774..738292c 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -235,6 +235,10 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
  */
 #define	TFO_SERVER_ALWAYS	0x1000
 
+/* NewCWV defaults */
+#define NCWV_UNDEF		0xFFFFFFFF
+#define NCWV_FIVEMINS		(HZ*300)
+
 extern struct inet_timewait_death_row tcp_death_row;
 
 /* sysctl variables for tcp */
@@ -284,6 +288,7 @@ extern int sysctl_tcp_challenge_ack_limit;
 extern unsigned int sysctl_tcp_notsent_lowat;
 extern int sysctl_tcp_min_tso_segs;
 extern int sysctl_tcp_autocorking;
+extern int sysctl_tcp_newcwv;
 
 extern atomic_long_t tcp_memory_allocated;
 extern struct percpu_counter tcp_sockets_allocated;
@@ -975,7 +980,7 @@ static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
 {
 	return tp->snd_una + tp->snd_wnd;
 }
-bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight);
+bool tcp_is_cwnd_limited(struct sock *sk, u32 in_flight);
 
 static inline void tcp_check_probe_timer(struct sock *sk)
 {
@@ -1324,6 +1329,13 @@ struct tcp_fastopen_context {
 	struct rcu_head		rcu;
 };
 
+/* TCP New CWV functions */
+void tcp_newcwv_update_pipeack(struct sock *sk);
+void tcp_newcwv_datalim_closedown(struct sock *sk);
+void tcp_newcwv_enter_recovery(struct sock *sk);
+void tcp_newcwv_end_recovery(struct sock *sk);
+void tcp_newcwv_reset(struct sock *sk);
+
 /* write queue abstraction */
 static inline void tcp_write_queue_purge(struct sock *sk)
 {
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index f032688..f687746 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -10,7 +10,7 @@ obj-y     := route.o inetpeer.o protocol.o \
 	     tcp_minisocks.o tcp_cong.o tcp_metrics.o tcp_fastopen.o \
 	     tcp_offload.o datagram.o raw.o udp.o udplite.o \
 	     udp_offload.o arp.o icmp.o devinet.o af_inet.o igmp.o \
-	     fib_frontend.o fib_semantics.o fib_trie.o \
+	     fib_frontend.o fib_semantics.o fib_trie.o tcp_newcwv.o \
 	     inet_fragment.o ping.o ip_tunnel_core.o gre_offload.o
 
 obj-$(CONFIG_NET_IP_TUNNEL) += ip_tunnel.o
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 5cde8f2..bfdf30e 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -493,6 +493,13 @@ static struct ctl_table ipv4_table[] = {
 		.proc_handler	= proc_dointvec
 	},
 	{
+		.procname	= "tcp_newcwv",
+		.data		= &sysctl_tcp_newcwv,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec
+	},
+	{
 		.procname	= "tcp_reordering",
 		.data		= &sysctl_tcp_reordering,
 		.maxlen		= sizeof(int),
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 2b9464c..6fb0719 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -93,6 +93,9 @@ void tcp_init_congestion_control(struct sock *sk)
 		rcu_read_unlock();
 	}
 
+	/* draft-ietf-tcpm-newcwv initial state */
+	tcp_newcwv_reset(sk);
+
 	if (icsk->icsk_ca_ops->init)
 		icsk->icsk_ca_ops->init(sk);
 }
@@ -279,13 +282,17 @@ int tcp_set_congestion_control(struct sock *sk, const char *name)
 /* RFC2861 Check whether we are limited by application or congestion window
  * This is the inverse of cwnd check in tcp_tso_should_defer
  */
-bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight)
+bool tcp_is_cwnd_limited(struct sock *sk, u32 in_flight)
 {
-	const struct tcp_sock *tp = tcp_sk(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
 	u32 left;
 
-	if (in_flight >= tp->snd_cwnd)
+	/* draft-ietf-tcpm-newcwv relaxes conditions for growing cwnd */
+	if (in_flight >= tp->snd_cwnd || (sysctl_tcp_newcwv &&
+	    tp->pipeack >= (tp->snd_cwnd*tp->mss_cache >> 1))) {
+		tp->cwnd_valid_ts = tcp_time_stamp;
 		return true;
+	}
 
 	left = tp->snd_cwnd - in_flight;
 	if (sk_can_gso(sk) &&
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3a26b3b..274fbf3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1927,6 +1927,7 @@ void tcp_enter_loss(struct sock *sk, int how)
 	tp->snd_cwnd	   = 1;
 	tp->snd_cwnd_cnt   = 0;
 	tp->snd_cwnd_stamp = tcp_time_stamp;
+	tcp_newcwv_reset(sk);
 
 	tcp_clear_retrans_partial(tp);
 
@@ -2522,7 +2523,16 @@ static inline void tcp_end_cwnd_reduction(struct sock *sk)
 	    (tp->undo_marker && tp->snd_ssthresh < TCP_INFINITE_SSTHRESH)) {
 		tp->snd_cwnd = tp->snd_ssthresh;
 		tp->snd_cwnd_stamp = tcp_time_stamp;
+
+		/* draft-ietf-tcpm-newcwv actions at the end of recovery */
+		if (sysctl_tcp_newcwv) {
+			if (tp->loss_flight_size)
+				tcp_newcwv_end_recovery(sk);
+			tcp_newcwv_reset(sk);
+		}
 	}
+	tp->loss_flight_size = 0;
+
 	tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
 }
 
@@ -2666,6 +2676,11 @@ static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
 	tp->undo_marker = tp->snd_una;
 	tp->undo_retrans = tp->retrans_out;
 
+	/* draft-ietf-tcpm-newcwv reduction at start of recovery */
+	if (sysctl_tcp_newcwv &&
+	    tp->pipeack <= (tp->snd_cwnd*tp->mss_cache >> 1))
+		tcp_newcwv_enter_recovery(sk);
+
 	if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
 		if (!ece_ack)
 			tp->prior_ssthresh = tcp_current_ssthresh(sk);
@@ -3449,6 +3464,11 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 				    sack_rtt_us);
 	acked -= tp->packets_out;
 
+	/* draft-ietf-tcpm-newcwv pipeack estimation */
+	if (sysctl_tcp_newcwv && icsk->icsk_ca_state <= TCP_CA_Disorder
+	    && (flag & FLAG_DATA_ACKED))
+		tcp_newcwv_update_pipeack(sk);
+
 	/* Advance cwnd if state allows */
 	if (tcp_may_raise_cwnd(sk, flag))
 		tcp_cong_avoid(sk, ack, acked, prior_in_flight);
diff --git a/net/ipv4/tcp_newcwv.c b/net/ipv4/tcp_newcwv.c
new file mode 100644
index 0000000..5a19549
--- /dev/null
+++ b/net/ipv4/tcp_newcwv.c
@@ -0,0 +1,140 @@
+/*
+ * New-CWV implementation for Linux: draft-ietf-tcpm-newcwv.txt
+ */
+
+#include <linux/module.h>
+#include <net/tcp.h>
+
+#define nextbin(x)  (((x)+1) & 0x03)
+#define prevbin(x)  (((x)-1) & 0x03)
+
+int sysctl_tcp_newcwv __read_mostly;
+
+/* returns pipeack in MSSs */
+static u32 pa_pkts(struct tcp_sock *tp)
+{
+	if (tp->pipeack == NCWV_UNDEF || !tp->mss_cache)
+		return 0;
+
+	return (tp->pipeack)/tp->mss_cache;
+}
+
+/* initialies newcwv variables */
+void tcp_newcwv_reset(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	tp->prev_snd_una = tp->snd_una;
+	tp->prev_snd_nxt = tp->snd_nxt;
+	tp->cwnd_valid_ts = tcp_time_stamp;
+	tp->loss_flight_size = 0;
+
+	tp->head = 0;
+	tp->psample[0] = NCWV_UNDEF;
+	tp->pipeack = NCWV_UNDEF;
+}
+
+/* This fuction removes all the expired elements from the circular buffer
+ * and returns the maximum from the remaining elements
+ */
+static int remove_expired_element(struct tcp_sock *tp, u32 psp)
+{
+	int k = tp->head;
+	int tmp = tp->psample[tp->head];
+
+	while (tp->psample[k] != NCWV_UNDEF) {
+		/* remove expired */
+		if (tp->time_stamp[k] < tcp_time_stamp - psp) {
+			tp->psample[k] = NCWV_UNDEF;
+			continue;
+		}
+
+		/* search the maximum */
+		if (tp->psample[k] > tmp)
+			tmp = tp->psample[k];
+
+		k = prevbin(k);
+		if (k == tp->head)
+			return tmp;
+	}
+
+	return tmp;
+}
+
+/* updates pipeack when an ACK is received */
+void tcp_newcwv_update_pipeack(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	u32 tmp_pipeack, psp, h;
+
+	psp = max_t(u32, 3*usecs_to_jiffies(tp->srtt_us>>3), (u32) HZ);
+
+	if (tp->snd_una >= tp->prev_snd_nxt) {
+
+		/* now get a new pipeack sample */
+		tmp_pipeack = tp->snd_una - tp->prev_snd_una;
+		tp->prev_snd_una = tp->snd_una;
+		tp->prev_snd_nxt = tp->snd_nxt;
+
+		h = tp->head;
+
+		/* create a new element at the end of current pmp */
+		if (tp->psample[h] == NCWV_UNDEF ||
+		    tcp_time_stamp > tp->time_stamp[h] + (psp >> 2)) {
+
+			/* Add an element to circular the buffer */
+			tp->head = nextbin(h);
+			tp->psample[tp->head] = tmp_pipeack;
+			tp->time_stamp[tp->head] = tcp_time_stamp;
+
+		} else if (tmp_pipeack > tp->psample[h])
+			tp->psample[h] = tmp_pipeack;
+	}
+
+	tp->pipeack = remove_expired_element(tp, psp);
+}
+
+/* newcwv actions at loss detection */
+void tcp_newcwv_enter_recovery(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	u32 pipe;
+
+	if (tp->pipeack == NCWV_UNDEF)
+		return;
+
+	tp->prior_retrans = tp->total_retrans;
+	tp->loss_flight_size = tcp_packets_in_flight(tp);
+
+	pipe =  max_t(u32, pa_pkts(tp), tp->loss_flight_size);
+	tp->snd_cwnd = max_t(u32, pipe >> 1, 1UL);
+}
+
+/* newcwv actions at the end of recovery */
+void tcp_newcwv_end_recovery(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	u32 retrans, pipe;
+
+	retrans = tp->total_retrans - tp->prior_retrans;
+	pipe = max_t(u32, pa_pkts(tp), tp->loss_flight_size) - retrans;
+	tp->snd_ssthresh = max_t(u32, pipe >> 1, 1UL);
+	tp->snd_cwnd = tp->snd_ssthresh;
+}
+
+
+/* reduces the cwnd after 5mins of non-validated phase */
+void tcp_newcwv_datalim_closedown(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	while ((tcp_time_stamp -  tp->cwnd_valid_ts) > NCWV_FIVEMINS &&
+		tp->snd_cwnd > TCP_INIT_CWND) {
+		tp->cwnd_valid_ts += NCWV_FIVEMINS;
+
+		tp->snd_ssthresh =
+		    max_t(u32, (3 * tp->snd_cwnd) >> 2, tp->snd_ssthresh);
+		tp->snd_cwnd =
+		    max_t(u32, tp->snd_cwnd >> 1, TCP_INIT_CWND);
+	}
+}
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 12d6016..e868211 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -168,6 +168,9 @@ static void tcp_event_data_sent(struct tcp_sock *tp,
 	const u32 now = tcp_time_stamp;
 	const struct dst_entry *dst = __sk_dst_get(sk);
 
+	if (sysctl_tcp_newcwv)
+		tcp_newcwv_datalim_closedown(sk);
+
 	if (sysctl_tcp_slow_start_after_idle &&
 	    (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
 		tcp_cwnd_restart(sk, __sk_dst_get(sk));
-- 
1.7.9.5

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