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authorAndrey Vagin <avagin@openvz.org>2014-08-13 16:03:10 +0400
committerDavid S. Miller <davem@davemloft.net>2014-08-14 14:38:54 -0700
commit9d186cac7ffb1831e9f34cb4a3a8b22abb9dd9d4 (patch)
treebb689167aa49110128c81e0ca131abc3a08a1097
parentfdd42e4400fcb5fe837a20a8d837ef094d5a26fb (diff)
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] [<ffffffff817aa2d2>] dump_stack+0x4d/0x66 [ 879.570599] [<ffffffff8109afbd>] warn_slowpath_common+0x7d/0xa0 [ 879.570935] [<ffffffff8109b0ea>] warn_slowpath_null+0x1a/0x20 [ 879.571292] [<ffffffff816d0a05>] tcp_ack+0x11f5/0x1380 [ 879.571614] [<ffffffff816d10bd>] tcp_rcv_established+0x1ed/0x710 [ 879.571958] [<ffffffff816dc9da>] tcp_v4_do_rcv+0x10a/0x370 [ 879.572315] [<ffffffff81657459>] release_sock+0x89/0x1d0 [ 879.572642] [<ffffffff816c81a0>] do_tcp_setsockopt.isra.36+0x120/0x860 [ 879.573000] [<ffffffff8110a52e>] ? rcu_read_lock_held+0x6e/0x80 [ 879.573352] [<ffffffff816c8912>] tcp_setsockopt+0x32/0x40 [ 879.573678] [<ffffffff81654ac4>] sock_common_setsockopt+0x14/0x20 [ 879.574031] [<ffffffff816537b0>] SyS_setsockopt+0x80/0xf0 [ 879.574393] [<ffffffff817b40a9>] 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 <edumazet@google.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrey Vagin <avagin@openvz.org> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--include/net/tcp.h4
-rw-r--r--net/ipv4/tcp.c14
-rw-r--r--net/ipv4/tcp_output.c5
3 files changed, 14 insertions, 9 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h
index dafa1cbc149b..36f55254573f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -705,8 +705,10 @@ struct tcp_skb_cb {
#define TCPCB_SACKED_RETRANS 0x02 /* SKB retransmitted */
#define TCPCB_LOST 0x04 /* SKB is lost */
#define TCPCB_TAGBITS 0x07 /* All tag bits */
+#define TCPCB_REPAIRED 0x10 /* SKB repaired (no skb_mstamp) */
#define TCPCB_EVER_RETRANS 0x80 /* Ever retransmitted frame */
-#define TCPCB_RETRANS (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS)
+#define TCPCB_RETRANS (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
+ TCPCB_REPAIRED)
__u8 ip_dsfield; /* IPv4 tos or IPv6 dsfield */
/* 1 byte hole */
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
@@ -1188,13 +1188,6 @@ new_segment:
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.
*/
if (sk->sk_route_caps & NETIF_F_ALL_CSUM)
@@ -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) {