From 9d186cac7ffb1831e9f34cb4a3a8b22abb9dd9d4 Mon Sep 17 00:00:00 2001 From: Andrey Vagin Date: Wed, 13 Aug 2014 16:03:10 +0400 Subject: tcp: don't use timestamp from repaired skb-s to calculate RTT (v2) We don't know right timestamp for repaired skb-s. Wrong RTT estimations isn't good, because some congestion modules heavily depends on it. This patch adds the TCPCB_REPAIRED flag, which is included in TCPCB_RETRANS. Thanks to Eric for the advice how to fix this issue. This patch fixes the warning: [ 879.562947] WARNING: CPU: 0 PID: 2825 at net/ipv4/tcp_input.c:3078 tcp_ack+0x11f5/0x1380() [ 879.567253] CPU: 0 PID: 2825 Comm: socket-tcpbuf-l Not tainted 3.16.0-next-20140811 #1 [ 879.567829] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 879.568177] 0000000000000000 00000000c532680c ffff880039643d00 ffffffff817aa2d2 [ 879.568776] 0000000000000000 ffff880039643d38 ffffffff8109afbd ffff880039d6ba80 [ 879.569386] ffff88003a449800 000000002983d6bd 0000000000000000 000000002983d6bc [ 879.569982] Call Trace: [ 879.570264] [] dump_stack+0x4d/0x66 [ 879.570599] [] warn_slowpath_common+0x7d/0xa0 [ 879.570935] [] warn_slowpath_null+0x1a/0x20 [ 879.571292] [] tcp_ack+0x11f5/0x1380 [ 879.571614] [] tcp_rcv_established+0x1ed/0x710 [ 879.571958] [] tcp_v4_do_rcv+0x10a/0x370 [ 879.572315] [] release_sock+0x89/0x1d0 [ 879.572642] [] do_tcp_setsockopt.isra.36+0x120/0x860 [ 879.573000] [] ? rcu_read_lock_held+0x6e/0x80 [ 879.573352] [] tcp_setsockopt+0x32/0x40 [ 879.573678] [] sock_common_setsockopt+0x14/0x20 [ 879.574031] [] SyS_setsockopt+0x80/0xf0 [ 879.574393] [] system_call_fastpath+0x16/0x1b [ 879.574730] ---[ end trace a17cbc38eb8c5c00 ]--- v2: moving setting of skb->when for repaired skb-s in tcp_write_xmit, where it's set for other skb-s. Fixes: 431a91242d8d ("tcp: timestamp SYN+DATA messages") Fixes: 740b0f1841f6 ("tcp: switch rtt estimations to usec resolution") Cc: Eric Dumazet Cc: Pavel Emelyanov Cc: "David S. Miller" Signed-off-by: Andrey Vagin Signed-off-by: David S. Miller --- net/ipv4/tcp.c | 14 +++++++------- net/ipv4/tcp_output.c | 5 ++++- 2 files changed, 11 insertions(+), 8 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 181b70ebd964..541f26a67ba2 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1187,13 +1187,6 @@ new_segment: if (!skb) goto wait_for_memory; - /* - * All packets are restored as if they have - * already been sent. - */ - if (tp->repair) - TCP_SKB_CB(skb)->when = tcp_time_stamp; - /* * Check whether we can use HW checksum. */ @@ -1203,6 +1196,13 @@ new_segment: skb_entail(sk, skb); copy = size_goal; max = size_goal; + + /* All packets are restored as if they have + * already been sent. skb_mstamp isn't set to + * avoid wrong rtt estimation. + */ + if (tp->repair) + TCP_SKB_CB(skb)->sacked |= TCPCB_REPAIRED; } /* Try to append data to the end of skb. */ diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index ef4a051de018..ff3f0f75cc6c 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1934,8 +1934,11 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, tso_segs = tcp_init_tso_segs(sk, skb, mss_now); BUG_ON(!tso_segs); - if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) + if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) { + /* "when" is used as a start point for the retransmit timer */ + TCP_SKB_CB(skb)->when = tcp_time_stamp; goto repair; /* Skip network transmission */ + } cwnd_quota = tcp_cwnd_test(tp, skb); if (!cwnd_quota) { -- cgit v1.2.3