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Message-Id: <1374385170-358-1-git-send-email-ycheng@google.com>
Date: Sat, 20 Jul 2013 22:39:27 -0700
From: Yuchung Cheng <ycheng@...gle.com>
To: davem@...emloft.net, ncardwell@...gle.com, edumazet@...gle.com
Cc: nanditad@...gle.com, netdev@...r.kernel.org,
Yuchung Cheng <ycheng@...gle.com>
Subject: [PATCH 1/4 net-next] tcp: consolidate SYNACK RTT sampling
This patch series improve RTT sampling in three ways:
1. Sample RTT during fast recovery and reordering events.
2. Favor ack-based RTT to timestamps because of broken TS ECR fields
3. Consolidate the RTT measurement logic.
The first patch consolidates SYNACK and other RTT measurement to use a
central function tcp_ack_update_rtt(). A (small) bonus is now SYNACK
RTT measurement happens after PAWS check, potentially reducing the
impact of RTO seeding on bad TCP timestamps values.
Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
---
include/net/tcp.h | 9 ---------
net/ipv4/tcp_input.c | 11 +++++++++++
net/ipv4/tcp_ipv4.c | 2 --
net/ipv4/tcp_minisocks.c | 8 ++------
net/ipv6/tcp_ipv6.c | 2 --
5 files changed, 13 insertions(+), 19 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index d198005..f9777db 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1094,15 +1094,6 @@ static inline void tcp_openreq_init(struct request_sock *req,
ireq->loc_port = tcp_hdr(skb)->dest;
}
-/* Compute time elapsed between SYNACK and the ACK completing 3WHS */
-static inline void tcp_synack_rtt_meas(struct sock *sk,
- struct request_sock *req)
-{
- if (tcp_rsk(req)->snt_synack)
- tcp_valid_rtt_meas(sk,
- tcp_time_stamp - tcp_rsk(req)->snt_synack);
-}
-
extern void tcp_enter_memory_pressure(struct sock *sk);
static inline int keepalive_intvl_when(const struct tcp_sock *tp)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 28af45a..988e816 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2853,6 +2853,17 @@ static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
tcp_ack_no_tstamp(sk, seq_rtt, flag);
}
+/* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
+static void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req)
+{
+ struct tcp_sock *tp = tcp_sk(sk);
+ s32 seq_rtt = -1;
+
+ if (tp->lsndtime && !tp->total_retrans)
+ seq_rtt = tcp_time_stamp - tp->lsndtime;
+ tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, seq_rtt);
+}
+
static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index b299da5..2e3f129 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1671,8 +1671,6 @@ struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;
tcp_initialize_rcv_mss(newsk);
- tcp_synack_rtt_meas(newsk, req);
- newtp->total_retrans = req->num_retrans;
#ifdef CONFIG_TCP_MD5SIG
/* Copy over the MD5 key from the original socket */
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index ab1c086..58a3e69 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -411,6 +411,8 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
newtp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
tcp_enable_early_retrans(newtp);
newtp->tlp_high_seq = 0;
+ newtp->lsndtime = treq->snt_synack;
+ newtp->total_retrans = req->num_retrans;
/* So many TCP implementations out there (incorrectly) count the
* initial SYN frame in their delayed-ACK and congestion control
@@ -666,12 +668,6 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
if (!(flg & TCP_FLAG_ACK))
return NULL;
- /* Got ACK for our SYNACK, so update baseline for SYNACK RTT sample. */
- if (tmp_opt.saw_tstamp && tmp_opt.rcv_tsecr)
- tcp_rsk(req)->snt_synack = tmp_opt.rcv_tsecr;
- else if (req->num_retrans) /* don't take RTT sample if retrans && ~TS */
- tcp_rsk(req)->snt_synack = 0;
-
/* For Fast Open no more processing is needed (sk is the
* child socket).
*/
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 6e1649d..80fe69e 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1237,8 +1237,6 @@ static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;
tcp_initialize_rcv_mss(newsk);
- tcp_synack_rtt_meas(newsk, req);
- newtp->total_retrans = req->num_retrans;
newinet->inet_daddr = newinet->inet_saddr = LOOPBACK4_IPV6;
newinet->inet_rcv_saddr = LOOPBACK4_IPV6;
--
1.8.3
--
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