[PATCH v2 03/16] ratp: send missing RST in behavior C2

[Aleksander Morgado]

The reference says:

    If SYN was set we assume that the other end crashed and has
    attempted to open a new connection.  We respond by sending a
    legal reset:
        <SN=received AN><AN=received SN+1 modulo 2><CTL=RST, ACK>

Add this missing step.

This issue affects the barebox<->bbremote interaction if bbremote
crashes without closing the channel and restarts opening a complete
new connection.

Signed-off-by: Aleksander Morgado <aleksander at aleksander.es>
---
 lib/ratp.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lib/ratp.c b/lib/ratp.c
index e9536499e..a8ac52c75 100644
--- a/lib/ratp.c
+++ b/lib/ratp.c
@@ -731,8 +731,15 @@ static int ratp_behaviour_c2(struct ratp_internal *ri, void *pkt)
 		return 1;
 
 	if (hdr->control & RATP_CONTROL_SYN) {
+		uint8_t control;
+
 		ri->status = -ECONNRESET;
 		pr_debug("Error: Connection reset\n");
+
+		control = RATP_CONTROL_RST | RATP_CONTROL_ACK |
+			ratp_set_sn(ratp_an(hdr)) | ratp_set_an(!ratp_sn(hdr));
+		ratp_send_hdr(ri, control);
+
 		ratp_state_change(ri, RATP_STATE_CLOSED);
 		return 1;
 	}
-- 
2.13.1