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// SPDX-License-Identifier: GPL-2.0
// Test RFC 3042 "Limited Transmit": "sending a new data segment in
// response to each of the first two duplicate acknowledgments that
// arrive at the sender".
// This variation tests a receiver that supports SACK.
`./defaults.sh`
// Establish a connection.
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
+.1 < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7>
+0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
+.1 < . 1:1(0) ack 1 win 320
+0 accept(3, ..., ...) = 4
// Write some data, and send the initial congestion window.
+0 write(4, ..., 15000) = 15000
+0 > P. 1:10001(10000) ack 1
// Limited transmit: on first dupack, send a new data segment.
+.11 < . 1:1(0) ack 1 win 320 <sack 1001:2001,nop,nop>
+0 > . 10001:11001(1000) ack 1
// Limited transmit: on second dupack, send a new data segment.
+.01 < . 1:1(0) ack 1 win 320 <sack 1001:3001,nop,nop>
+0 > . 11001:12001(1000) ack 1
// It turned out to be reordering, not loss.
+.01 < . 1:1(0) ack 3001 win 320
+0 > P. 12001:14001(2000) ack 1
+.02 < . 1:1(0) ack 5001 win 320
+0 > P. 14001:15001(1000) ack 1
// Client gradually ACKs all data.
+.02 < . 1:1(0) ack 7001 win 320
+.02 < . 1:1(0) ack 9001 win 320
+.02 < . 1:1(0) ack 11001 win 320
+.02 < . 1:1(0) ack 13001 win 320
+.02 < . 1:1(0) ack 15001 win 320
// Clean up.
+.17 close(4) = 0
+0 > F. 15001:15001(0) ack 1
+.1 < F. 1:1(0) ack 15002 win 257
+0 > . 15002:15002(0) ack 2
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