netdev - Re: [PATCH] tcp: TCP_USER_TIMEOUT can not work in tcp_probe

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Message-ID: <1505228700.15310.138.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 12 Sep 2017 08:05:00 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     liujian <liujian56@...wei.com>
Cc:     davem@...emloft.net, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org,
        edumazet@...gle.com, ycheng@...gle.com, hkchu@...gle.com,
        netdev@...r.kernel.org, weiyongjun1@...wei.com,
        wangkefeng 00227729 <wangkefeng.wang@...wei.com>
Subject: Re: [PATCH] tcp: TCP_USER_TIMEOUT can not work in tcp_probe_timer()

On Tue, 2017-09-12 at 14:08 +0800, liujian wrote:
> Hi,
> 
> In the scenario, tcp server side IP changed, and at that memont,
> userspace application still send data continuously;
> tcp_send_head(sk)'s timestamp always be refreshed.
> 
> Here is the packetdrill script:
> 
>    0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
>    +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
>    +0 bind(3, ..., ...) = 0
>    +0 listen(3, 1) = 0
> 
>    +0 < S 0:0(0) win 0 <mss 1460,sackOK,nop,nop,nop,wscale 7>
>    +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 7>
> 
>   +.1 < . 1:1(0) ack 1 win 65530
>    +0 accept(3, ..., ...) = 4
> 
>    +0 setsockopt(4, SOL_TCP, TCP_USER_TIMEOUT, [3000], 4) = 0
>    +0 write(4, ..., 24) = 24
>    +0 > P. 1:25(24) ack 1 win 229
>    +.1 < . 1:1(0) ack 25 win 65530
> 
> //change the ipaddress
>    +1 `ifconfig tun0 192.168.0.10/16`
> 
>    +1 write(4, ..., 24) = 24
>    +1 write(4, ..., 24) = 24
>    +1 write(4, ..., 24) = 24
>    +1 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
>    +3 write(4, ..., 24) = 24
> 
>    +0 `ifconfig tun0 192.168.0.1/16`
>    +0 < . 1:1(0) ack 1 win 1000
>    +0 write(4, ..., 24) = -1
> 
> 

This has nothing to do with the code patch you have changed.

How have you tested your patch exactly ?


> [root@...alhost ~]# time ./gtests/net/packetdrill/packetdrill test.pkt
> test.pkt:50: runtime error in write call: Expected result -1 but got 24 with errno 2 (No such file or directory)
> 
> real	1m11.364s
> user	0m0.028s
> sys	0m0.106s
> 
> [root@...alhost ~]# netstat -toen
> Active Internet connections (w/o servers)
> Proto Recv-Q Send-Q Local Address           Foreign Address         State       User       Inode      Timer
> tcp        0    504 192.168.0.1:8080        192.0.2.1:33993         ESTABLISHED 0          45453      probe (22.38/0/7)
> 
> since the script didn't wait for enough time, here only got 7 probes.
> 
> 在 2017/9/11 23:22, Eric Dumazet 写道:
> > On Mon, 2017-09-11 at 08:13 -0700, Eric Dumazet wrote:
> > 
> >> You can see we got only 3 probes, not 4.
> > 
> > Here is complete packetdrill test showing that code behaves as expected.
> > 
> >     0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
> >    +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> >    +0 bind(3, ..., ...) = 0
> >    +0 listen(3, 1) = 0
> > 
> >    +0 < S 0:0(0) win 0 <mss 1460,sackOK,nop,nop,nop,wscale 7>
> >    +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
> > 
> > // Client advertises a zero receive window, so we can't send.
> >   +.1 < . 1:1(0) ack 1 win 0
> >    +0 accept(3, ..., ...) = 4
> > 
> >    +0 setsockopt(4, SOL_TCP, TCP_USER_TIMEOUT, [3000], 4) = 0
> >    +0 write(4, ..., 2920) = 2920
> > 
> > // Window probes are scheduled just like RTOs.
> >   +.3~+.31 > . 0:0(0) ack 1
> >   +.6~+.62 > . 0:0(0) ack 1
> >  +1.2~+1.24 > . 0:0(0) ack 1
> > 
> > // Peer opens its window too late !
> >    +3 < . 1:1(0) ack 1 win 1000
> >    +0 > R 1:1(0)
> > 
> > 
> > 
> > .
> > 
>