Messages in this thread | | | From | Yuchung Cheng <> | Date | Tue, 12 Aug 2014 07:53:57 -0700 | Subject | Re: [PATCH] tcp: don't use timestamp from repaired skb-s to calculate RTT |
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On Tue, Aug 12, 2014 at 2:45 AM, Andrey Vagin <avagin@openvz.org> wrote: > 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 ]--- > > 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> > --- > include/net/tcp.h | 4 +++- > net/ipv4/tcp.c | 16 +++++++++------- > 2 files changed, 12 insertions(+), 8 deletions(-) > > diff --git a/include/net/tcp.h b/include/net/tcp.h > index dafa1cb..36f5525 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 181b70e..cb5f548 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 +1196,15 @@ 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; > + TCP_SKB_CB(skb)->when = tcp_time_stamp; But this still allow RTT samples from TCP timestamp options even if the packet is marked retransmitted/repaired in tcp_ack_update_rtt()?
> + } > } > > /* Try to append data to the end of skb. */ > -- > 1.9.3 > > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
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