Re: [PATCH 1/6] tcp: FIN flags have to be retransmitted as well

On Fri, Aug 15, 2025 at 06:10:37PM +0200, Stefano Brivio wrote:

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 Signed-off-by: Stefano Brivio

Reviewed-by: David Gibson

--- tcp.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/tcp.c b/tcp.c index 957b498..7c1f237 100644 --- a/tcp.c +++ b/tcp.c @@ -1759,6 +1759,7 @@ 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; @@ -2286,6 +2287,7 @@ 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)) {

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson