Revert "tcp: fix TFO SYN_RECV to not zero retrans_stamp with retransmits out"

This reverts commit 2daffbd which is
commit 27c80ef upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Id7b3803b6df3424c52939cd7503aae4e2afa6c88
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: gregkh

net/ipv4/tcp_input.c

@@ -6570,17 +6570,10 @@ static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
 	if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss && !tp->packets_out)
 		tcp_try_undo_recovery(sk);
 
+	/* Reset rtx states to prevent spurious retransmits_timed_out() */
 	tcp_update_rto_time(tp);
+	tp->retrans_stamp = 0;
 	inet_csk(sk)->icsk_retransmits = 0;
-	/* In tcp_fastopen_synack_timer() on the first SYNACK RTO we set
-	 * retrans_stamp but don't enter CA_Loss, so in case that happened we
-	 * need to zero retrans_stamp here to prevent spurious
-	 * retransmits_timed_out(). However, if the ACK of our SYNACK caused us
-	 * to enter CA_Recovery then we need to leave retrans_stamp as it was
-	 * set entering CA_Recovery, for correct retransmits_timed_out() and
-	 * undo behavior.
-	 */
-	tcp_retrans_stamp_cleanup(sk);
 
 	/* Once we leave TCP_SYN_RECV or TCP_FIN_WAIT_1,
 	 * we no longer need req so release it.