On Mon, 2017-09-11 at 07:49 -0700, Eric Dumazet wrote:
> On Mon, 2017-09-11 at 14:27 +0800, liujia...@huawei.com wrote:
> > From: liujian <liujia...@huawei.com>
> >
> > After the tcp socket go to ESTABLISHED stat, change IP address (server
> > side),
> > then the tcp socket will go tcp_probe_timer process.
> >
> > [root@localhost net]# netstat -toe
> > Active Internet connections (w/o servers)
> > Proto Recv-Q Send-Q Local Address Foreign Address State
> > User Inode Timer
> > tcp 0 1104 9.81.254:personal-agent 9.84.201.213:23597
> > ESTABLISHED root 12819 probe (4.36/0/7)
> > [root@localhost net]# cat /proc/net/tcp
> > sl local_address rem_address st tx_queue rx_queue tr tm->when retrnsmt
> > uid timeout inode
> > 3: B1FE5109:15B3 D5C95409:5C2D 01 00000495:00000000 04:0000005E 00000000
> > 0 7 12819 2 ffff95cdcf45a000 20 4 1 10 -1
> >
> > In my test case, tcp_write_queue_head(sk) and tcp_send_head(sk) is same
> > SKB.
> > And ((s32)(tcp_time_stamp(tp) - start_ts) >
> > jiffies_to_msecs(icsk->icsk_user_timeout))
> > always is false.
>
> Interesting.
>
> > Here use keepalive_time_elapsed(tp) to do the compare as
> > tcp_keepalive_timer do.
>
>
> But zero window probe and TCP_USER_TIMEOUT can be used without
> keepalives...
>
>
> A packetdrill test would help, I will write one.
So existing code seems to work :
# cat window-probe-without-data-user-timeout.pkt
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
+2.4~+2.48 > . 0:0(0) ack 1
# ./packetdrill window-probe-without-data-user_timeout.pkt
08:10:39.306137 IP 192.0.2.1.58149 > 192.168.79.31.8080: Flags [S], seq 0, win
0, options [mss 1460,sackOK,nop,nop,nop,wscale 7], length 0
08:10:39.306166 IP 192.168.79.31.8080 > 192.0.2.1.58149: Flags [S.], seq
3982794529, ack 1, win 29200, options [mss 1460,nop,nop,sackOK,nop,wscale 8],
length 0
08:10:39.406296 IP 192.0.2.1.58149 > 192.168.79.31.8080: Flags [.], ack 1, win
0, length 0
08:10:39.716004 IP 192.168.79.31.8080 > 192.0.2.1.58149: Flags [.], ack 1, win
115, length 0
08:10:40.327133 IP 192.168.79.31.8080 > 192.0.2.1.58149: Flags [.], ack 1, win
115, length 0
08:10:41.540243 IP 192.168.79.31.8080 > 192.0.2.1.58149: Flags [.], ack 1, win
115, length 0
You can see we got only 3 probes, not 4.
