[PATCH v4 1/8] tcp: FIN flags have to be retransmitted as well

[Stefano Brivio <sbrivio@redhat.com>]

If we're retransmitting any data, and we sent a FIN segment to our
peer, regardless of whether it was received, we obviously have to
retransmit it as well, given that it can only come with the last data
segment, or after it.

Unconditionally clear the internal TAP_FIN_SENT flag whenever we
re-transmit, so that we know we have to send it again, in case.

Reported-by: Paul Holzinger <pholzing@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---
 tcp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tcp.c b/tcp.c
index 253cdb3..9b7a9b0 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1778,6 +1778,7 @@ static int tcp_data_from_tap(const struct ctx *c, struct tcp_tap_conn *conn,
 			   "fast re-transmit, ACK: %u, previous sequence: %u",
 			   max_ack_seq, conn->seq_to_tap);
 		conn->seq_to_tap = max_ack_seq;
+		conn->events &= ~TAP_FIN_SENT;
 		if (tcp_set_peek_offset(conn, 0)) {
 			tcp_rst(c, conn);
 			return -1;
@@ -2312,6 +2313,7 @@ void tcp_timer_handler(const struct ctx *c, union epoll_ref ref)
 			flow_dbg(conn, "ACK timeout, retry");
 			conn->retrans++;
 			conn->seq_to_tap = conn->seq_ack_from_tap;
+			conn->events &= ~TAP_FIN_SENT;
 			if (!conn->wnd_from_tap)
 				conn->wnd_from_tap = 1; /* Zero-window probe */
 			if (tcp_set_peek_offset(conn, 0)) {
-- 
@@ -1778,6 +1778,7 @@ static int tcp_data_from_tap(const struct ctx *c, struct tcp_tap_conn *conn,
 			   "fast re-transmit, ACK: %u, previous sequence: %u",
 			   max_ack_seq, conn->seq_to_tap);
 		conn->seq_to_tap = max_ack_seq;
+		conn->events &= ~TAP_FIN_SENT;
 		if (tcp_set_peek_offset(conn, 0)) {
 			tcp_rst(c, conn);
 			return -1;
@@ -2312,6 +2313,7 @@ void tcp_timer_handler(const struct ctx *c, union epoll_ref ref)
 			flow_dbg(conn, "ACK timeout, retry");
 			conn->retrans++;
 			conn->seq_to_tap = conn->seq_ack_from_tap;
+			conn->events &= ~TAP_FIN_SENT;
 			if (!conn->wnd_from_tap)
 				conn->wnd_from_tap = 1; /* Zero-window probe */
 			if (tcp_set_peek_offset(conn, 0)) {
-- 
2.43.0