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// SPDX-License-Identifier: GPL-2.0
// Test what happens when client does not provide MD5 on SYN,
// but then does on the ACK that completes the three-way handshake.
`./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
+0 < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 10>
+0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
// Ooh, weird: client provides MD5 option on the ACK:
+.01 < . 1:1(0) ack 1 win 514 <md5 000102030405060708090a0b0c0d0e0f,nop,nop>
+.01 < . 1:1(0) ack 1 win 514 <md5 000102030405060708090a0b0c0d0e0f,nop,nop>
// The TCP listener refcount should be 2, but on buggy kernels it can be 0:
+0 `grep " 0A " /proc/net/tcp /proc/net/tcp6 | grep ":1F90"`
// Now here comes the legit ACK:
+.01 < . 1:1(0) ack 1 win 514
// Make sure the connection is OK:
+0 accept(3, ..., ...) = 4
+.01 write(4, ..., 1000) = 1000
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