47 lines
2.1 KiB
Plaintext
47 lines
2.1 KiB
Plaintext
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// SPDX-License-Identifier: GPL-2.0
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//
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// A reproducer case for a TFO SYNACK RTO undo bug in:
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// 794200d66273 ("tcp: undo cwnd on Fast Open spurious SYNACK retransmit")
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// This sequence that tickles this bug is:
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// - Fast Open server receives TFO SYN with data, sends SYNACK
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// - (client receives SYNACK and sends ACK, but ACK is lost)
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// - server app sends some data packets
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// - (N of the first data packets are lost)
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// - server receives client ACK that has a TS ECR matching first SYNACK,
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// and also SACKs suggesting the first N data packets were lost
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// - server performs undo of SYNACK RTO, then immediately enters recovery
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// - buggy behavior in 794200d66273 then performed an undo that caused
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// the connection to be in a bad state, in CA_Open with retrans_out != 0
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// Check that outbound TS Val ticks are as we would expect with 1000 usec per
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// timestamp tick:
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--tcp_ts_tick_usecs=1000
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`./defaults.sh`
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// Initialize connection
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0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
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+0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
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+0 setsockopt(3, SOL_TCP, TCP_FASTOPEN, [1], 4) = 0
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+0 bind(3, ..., ...) = 0
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+0 listen(3, 1) = 0
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+0 < S 0:1000(1000) win 65535 <mss 1012,sackOK,TS val 1000 ecr 0,wscale 7,nop,nop,nop,FO TFO_COOKIE>
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+0 > S. 0:0(0) ack 1001 <mss 1460,sackOK,TS val 2000 ecr 1000,nop,wscale 8>
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+0 accept(3, ..., ...) = 4
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// Application writes more data
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+.010 write(4, ..., 10000) = 10000
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+0 > P. 1:5001(5000) ack 1001 <nop,nop,TS val 2010 ecr 1000>
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+0 > P. 5001:10001(5000) ack 1001 <nop,nop,TS val 2010 ecr 1000>
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+0 %{ assert tcpi_snd_cwnd == 10, tcpi_snd_cwnd }%
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+0 < . 1001:1001(0) ack 1 win 257 <TS val 1010 ecr 2000,sack 2001:5001>
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+0 > P. 1:2001(2000) ack 1001 <nop,nop,TS val 2010 ecr 1010>
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+0 %{ assert tcpi_ca_state == TCP_CA_Recovery, tcpi_ca_state }%
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+0 %{ assert tcpi_snd_cwnd == 7, tcpi_snd_cwnd }%
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+0 < . 1001:1001(0) ack 1 win 257 <TS val 1011 ecr 2000,sack 2001:6001>
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+0 %{ assert tcpi_ca_state == TCP_CA_Recovery, tcpi_ca_state }%
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+0 %{ assert tcpi_snd_cwnd == 7, tcpi_snd_cwnd }%
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