From: Yves-Alexis Perez <corsac@debian.org>
Date: Mon, 8 Jan 2018 09:58:43 +0000 (+0100)
Subject: Revert "tcp: invalidate rate samples during SACK reneging"
X-Git-Tag: archive/raspbian/4.9.80-2+rpi1~8^2~5
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/success/%22http:/www.example.com/cgi/success?a=commitdiff_plain;h=312d37d4b4d55a3eb8de937864a98ecd39a026da;p=linux-4.9.git

Revert "tcp: invalidate rate samples during SACK reneging"

This reverts commit e74fe7268e7eadb2880d3842fe167131220d5616 which is
d4761754b4fb2ef8d9a1e9d121c4bec84e1fe292 upstream. Prevent changing the
tcp_sock structure, causing an ABI change.

Gbp-Pq: Topic debian
Gbp-Pq: Name revert-tcp-invalidate-rate-samples-during-SACK-reneg.patch
---

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index f50b717ce644..647532b0eb03 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -219,8 +219,7 @@ struct tcp_sock {
 	} rack;
 	u16	advmss;		/* Advertised MSS			*/
 	u8	rate_app_limited:1,  /* rate_{delivered,interval_us} limited? */
-		is_sack_reneg:1,    /* in recovery from loss with SACK reneg? */
-		unused:6;
+		unused:7;
 	u8	nonagle     : 4,/* Disable Nagle algorithm?             */
 		thin_lto    : 1,/* Use linear timeouts for thin streams */
 		thin_dupack : 1,/* Fast retransmit on first dupack      */
diff --git a/include/net/tcp.h b/include/net/tcp.h
index caf35e062639..fba4fc46871d 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1001,7 +1001,7 @@ void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb);
 void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
 			    struct rate_sample *rs);
 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
-		  bool is_sack_reneg, struct skb_mstamp *now, struct rate_sample *rs);
+		  struct skb_mstamp *now, struct rate_sample *rs);
 void tcp_rate_check_app_limited(struct sock *sk);
 
 /* These functions determine how the current flow behaves in respect of SACK
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 7efa6b062049..8cf5a2e2dd9b 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2300,7 +2300,6 @@ int tcp_disconnect(struct sock *sk, int flags)
 	tp->snd_cwnd_cnt = 0;
 	tp->window_clamp = 0;
 	tcp_set_ca_state(sk, TCP_CA_Open);
-	tp->is_sack_reneg = 0;
 	tcp_clear_retrans(tp);
 	inet_csk_delack_init(sk);
 	/* Initialize rcv_mss to TCP_MIN_MSS to avoid division by 0
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2f107e46355c..05255a286888 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1966,8 +1966,6 @@ void tcp_enter_loss(struct sock *sk)
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSACKRENEGING);
 		tp->sacked_out = 0;
 		tp->fackets_out = 0;
-		/* Mark SACK reneging until we recover from this loss event. */
-		tp->is_sack_reneg = 1;
 	}
 	tcp_clear_all_retrans_hints(tp);
 
@@ -2465,7 +2463,6 @@ static bool tcp_try_undo_recovery(struct sock *sk)
 		return true;
 	}
 	tcp_set_ca_state(sk, TCP_CA_Open);
-	tp->is_sack_reneg = 0;
 	return false;
 }
 
@@ -2497,10 +2494,8 @@ static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo)
 			NET_INC_STATS(sock_net(sk),
 					LINUX_MIB_TCPSPURIOUSRTOS);
 		inet_csk(sk)->icsk_retransmits = 0;
-		if (frto_undo || tcp_is_sack(tp)) {
+		if (frto_undo || tcp_is_sack(tp))
 			tcp_set_ca_state(sk, TCP_CA_Open);
-			tp->is_sack_reneg = 0;
-		}
 		return true;
 	}
 	return false;
@@ -3594,7 +3589,6 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	struct tcp_sacktag_state sack_state;
 	struct rate_sample rs = { .prior_delivered = 0 };
 	u32 prior_snd_una = tp->snd_una;
-	bool is_sack_reneg = tp->is_sack_reneg;
 	u32 ack_seq = TCP_SKB_CB(skb)->seq;
 	u32 ack = TCP_SKB_CB(skb)->ack_seq;
 	bool is_dupack = false;
@@ -3717,7 +3711,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 		tcp_schedule_loss_probe(sk);
 	delivered = tp->delivered - delivered;	/* freshly ACKed or SACKed */
 	lost = tp->lost - lost;			/* freshly marked lost */
-	tcp_rate_gen(sk, delivered, lost, is_sack_reneg, &now, &rs);
+	tcp_rate_gen(sk, delivered, lost, &now, &rs);
 	tcp_cong_control(sk, ack, delivered, flag, &rs);
 	tcp_xmit_recovery(sk, rexmit);
 	return 1;
diff --git a/net/ipv4/tcp_rate.c b/net/ipv4/tcp_rate.c
index 18309f58ab8d..9be1581a5a08 100644
--- a/net/ipv4/tcp_rate.c
+++ b/net/ipv4/tcp_rate.c
@@ -106,7 +106,7 @@ void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb,
 
 /* Update the connection delivery information and generate a rate sample. */
 void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
-		  bool is_sack_reneg, struct skb_mstamp *now, struct rate_sample *rs)
+		  struct skb_mstamp *now, struct rate_sample *rs)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	u32 snd_us, ack_us;
@@ -124,12 +124,8 @@ void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost,
 
 	rs->acked_sacked = delivered;	/* freshly ACKed or SACKed */
 	rs->losses = lost;		/* freshly marked lost */
-	/* Return an invalid sample if no timing information is available or
-	 * in recovery from loss with SACK reneging. Rate samples taken during
-	 * a SACK reneging event may overestimate bw by including packets that
-	 * were SACKed before the reneg.
-	 */
-	if (!rs->prior_mstamp.v64 || is_sack_reneg) {
+	/* Return an invalid sample if no timing information is available. */
+	if (!rs->prior_mstamp.v64) {
 		rs->delivered = -1;
 		rs->interval_us = -1;
 		return;