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)
