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 [root@localhost ~]# 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@localhost ~]# 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) > > > > . >
