tcp: Don't mistake a FIN segment with no data for a Fast Retransmit request

It carries no data and usually duplicates the previous ACK sequence,
but it's just a FIN.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/tcp.c b/tcp.c
index baf3c08..9f9b62d 100644
--- a/tcp.c
+++ b/tcp.c
@@ -2007,7 +2007,8 @@ static void tcp_data_from_tap(struct ctx *c, struct tcp_tap_conn *conn,
 			    ack_seq - max_ack_seq < MAX_WINDOW) {
 
 				/* Fast re-transmit */
-				retr = !len && ack_seq == max_ack_seq &&
+				retr = !len && !th->fin &&
+				       ack_seq == max_ack_seq &&
 				       max_ack_seq_wnd == ntohs(th->window);
 
 				max_ack_seq_wnd = ntohs(th->window);