commit b9ce204f0a265f819d10c943a607746abb62f245
author Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Fri Jun 15 15:08:43 2007 -0700
committer David S. Miller <davem@davemloft.net> Fri Jun 15 15:08:43 2007 -0700
tree 45078d076bcd952d8820c590653939b312d06ac2
parent 22b1a9203ea634ac0ee5240e021613da3328275f

[TCP]: Congestion control API RTT sampling fix

Commit 164891aadf1721fca4dce473bb0e0998181537c6 broke RTT
sampling of congestion control modules. Inaccurate timestamps
could be fed to them without providing any way for them to
identify such cases. Previously RTT sampler was called only if
FLAG_RETRANS_DATA_ACKED was not set filtering inaccurate
timestamps nicely. In addition, the new behavior could give an
invalid timestamp (zero) to RTT sampler if only skbs with
TCPCB_RETRANS were ACKed. This solves both problems.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_illinois.c

diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c
index 4adc47c..b2b2256 100644
--- a/net/ipv4/tcp_illinois.c
+++ b/net/ipv4/tcp_illinois.c
@@ -90,6 +90,9 @@
 
 	ca->acked = pkts_acked;
 
+	if (ktime_equal(last, net_invalid_timestamp()))
+		return;
+
 	rtt = ktime_to_us(net_timedelta(last));
 
 	/* ignore bogus values, this prevents wraparound in alpha math */

net/ipv4/tcp_input.c

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d6d0f9b..aaf6f666 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2409,7 +2409,7 @@
 	int acked = 0;
 	int prior_packets = tp->packets_out;
 	__s32 seq_rtt = -1;
-	ktime_t last_ackt = ktime_set(0,0);
+	ktime_t last_ackt = net_invalid_timestamp();
 
 	while ((skb = tcp_write_queue_head(sk)) &&
 	       skb != tcp_send_head(sk)) {
@@ -2487,6 +2487,10 @@
 		tcp_ack_update_rtt(sk, acked, seq_rtt);
 		tcp_ack_packets_out(sk);
 
+		/* Is the ACK triggering packet unambiguous? */
+		if (acked & FLAG_RETRANS_DATA_ACKED)
+			last_ackt = net_invalid_timestamp();
+
 		if (ca_ops->pkts_acked)
 			ca_ops->pkts_acked(sk, pkts_acked, last_ackt);
 	}

net/ipv4/tcp_lp.c

diff --git a/net/ipv4/tcp_lp.c b/net/ipv4/tcp_lp.c
index 43294ad..e49836c 100644
--- a/net/ipv4/tcp_lp.c
+++ b/net/ipv4/tcp_lp.c
@@ -266,7 +266,8 @@
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct lp *lp = inet_csk_ca(sk);
 
-	tcp_lp_rtt_sample(sk,  ktime_to_us(net_timedelta(last)));
+	if (!ktime_equal(last, net_invalid_timestamp()))
+		tcp_lp_rtt_sample(sk,  ktime_to_us(net_timedelta(last)));
 
 	/* calc inference */
 	if (tcp_time_stamp > tp->rx_opt.rcv_tsecr)

net/ipv4/tcp_vegas.c

diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index 73e19cf..e218a51 100644
--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -117,6 +117,9 @@
 	struct vegas *vegas = inet_csk_ca(sk);
 	u32 vrtt;
 
+	if (ktime_equal(last, net_invalid_timestamp()))
+		return;
+
 	/* Never allow zero rtt or baseRTT */
 	vrtt = ktime_to_us(net_timedelta(last)) + 1;
 

net/ipv4/tcp_veno.c

diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
index 9edb340..ec854cc 100644
--- a/net/ipv4/tcp_veno.c
+++ b/net/ipv4/tcp_veno.c
@@ -74,6 +74,9 @@
 	struct veno *veno = inet_csk_ca(sk);
 	u32 vrtt;
 
+	if (ktime_equal(last, net_invalid_timestamp()))
+		return;
+
 	/* Never allow zero rtt or baseRTT */
 	vrtt = ktime_to_us(net_timedelta(last)) + 1;