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

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Date:   Tue, 12 Sep 2017 08:38:06 -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 08:05 -0700, Eric Dumazet wrote:
> 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 ?
> 


lpaa23:~# ss -toenmi src :8080
State      Recv-Q Send-Q Local Address:Port               Peer
Address:Port              
ESTAB      0      144    192.168.134.161:8080
192.0.2.1:51165               timer:(persist,8.262ms,5) ino:1
82083 sk:3 <->
	 skmem:(r0,rb359040,t0,tb46080,f1792,w2304,o0,bl0,d0) sack cubic
wscale:7,8 rto:301 backoff:5 rtt:100.127/37.576 
mss:1460 rcvmss:536 advmss:1460 cwnd:10 bytes_acked:24 segs_out:12
segs_in:3 data_segs_out:12 send 1.2Mbps lastsnd:1370 l
astrcv:13348 lastack:13248 pacing_rate 2.3Mbps delivery_rate 116.7Kbps
app_limited busy:11346ms rcv_space:29200 notsent:1
44 minrtt:100.043

This is the typical RTO timer, not zero window probe.