Open Menu / tools / testing / selftests / net / packetdrill / tcp_ts_recent_invalid_ack.pkt 
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// SPDX-License-Identifier: GPL-2.0
// Test that we reject TS val updates on a packet with invalid ACK sequence

`./defaults.sh
`

// Create a socket.
    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

// Establish a connection.
  +.1 < S 0:0(0) win 20000 <mss 1000,sackOK,TS val 100 ecr 0>
   +0 > S. 0:0(0) ack 1 <mss 1460,sackOK,TS val 100 ecr 100>
  +.1 < . 1:1(0) ack 1 win 20000 <nop,nop,TS val 200 ecr 100>
   +0 accept(3, ..., ...) = 4

// bad packet with high tsval (its ACK sequence is above our sndnxt)
   +0 < F. 1:1(0) ack 9999 win 20000 <nop,nop,TS val 200000 ecr 100>
// Challenge ACK for SEG.ACK > SND.NXT (RFC 5961 5.2 / RFC 793 3.9).
// ecr=200 (not 200000) proves ts_recent was not updated from the bad packet.
   +0 > . 1:1(0) ack 1 <nop,nop,TS val 200 ecr 200>

   +0 < . 1:1001(1000) ack 1 win 20000 <nop,nop,TS val 201 ecr 100>
   +0 > . 1:1(0) ack 1001 <nop,nop,TS val 200 ecr 201>