From 9060e0d140f7de9b1158944f6129b9b029db48c6 Mon Sep 17 00:00:00 2001
From: Shawn Nock <shawn@monadnock.ca>
Date: Sat, 3 Aug 2019 04:36:45 -0500
Subject: [PATCH] Fixes ACK number off-by-one

---
 src/main.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/src/main.c b/src/main.c
index 751ebfd..ee10354 100644
--- a/src/main.c
+++ b/src/main.c
@@ -129,7 +129,7 @@ static struct h5 {
 	struct k_fifo		event_queue;
 
 	u8_t			tx_win;
-    u8_t            last_seen_seq_from_host;
+    u8_t            next_expected_seq_from_host;
     u8_t			local_seq;
 
 	linkstate_t link_state;
@@ -280,7 +280,7 @@ void h5_send(const u8_t *payload, u8_t type, int len)
 	h5_hdr_t hdr = {0};
 
 	/* Set ACK for outgoing packet and stop delayed work */
-	hdr.ack = h5.last_seen_seq_from_host;
+	hdr.ack = h5.next_expected_seq_from_host;
     k_delayed_work_cancel(&ack_work);
 
     LOG_INF("ACK'd %d", hdr.ack);
@@ -468,8 +468,10 @@ void bt_uart_isr(struct device *unused)
                        if (buf->len > 0) {
                            net_buf_put(&h5.unprocessed_queue, buf);
                            buf = NULL;
+                           slip_state = SLIP_NOSYNC;
+                       } else {
+                           slip_state = SLIP_SYNC;
                        }
-                       slip_state = SLIP_SYNC;
                    } else {
                        net_buf_add_u8(buf, byte);
                    }
@@ -548,19 +550,12 @@ static void unproc_thread(void) {
             LOG_DBG("Header: seq %d, ack %d, rel: %s, has_crc16: %s", hdr.seq, hdr.ack,
                     hdr.is_reliable ? "true" : "false",
                     hdr.crc_after_payload ? "true" : "false");
-            u8_t expected_seq;
-            if (h5.initializing) {
-                expected_seq = 0;
-                h5.initializing = false;
-            } else {
-                expected_seq = next_seq(h5.last_seen_seq_from_host);
-            }
-            if (hdr.seq != expected_seq) {
-                LOG_ERR("Seq expected %u got %u. Drop packet", expected_seq, hdr.seq);
+            if (hdr.seq != h5.next_expected_seq_from_host) {
+                LOG_ERR("Seq expected %u got %u. Drop packet", h5.next_expected_seq_from_host, hdr.seq);
                 goto next;
             }
             k_delayed_work_submit(&ack_work, H5_RX_ACK_TIMEOUT);
-            h5.last_seen_seq_from_host = hdr.seq;
+            h5.next_expected_seq_from_host = next_seq(hdr.seq);
         }
 
 		if (h5.link_state < ACTIVE && hdr.packet_type != HCI_3WIRE_LINK_PKT) {
@@ -889,7 +884,7 @@ static linkstate_t do_init(struct net_buf const *buf) {
         return INIT;
     case H5_CONFIG_RESPONSE:
         h5.tx_win = conf_rsp[2] & 0x7;
-        h5.last_seen_seq_from_host = 0;
+        h5.next_expected_seq_from_host = 0;
         h5.local_seq = 0;
         h5.initializing = true;
         LOG_DBG("Finished H5 configuration, tx_win %u: INIT -> ACTIVE", h5.tx_win);
@@ -921,7 +916,6 @@ static linkstate_t do_active(struct net_buf *buf) {
         // Presumably something from the controller
         if (bt_buf_get_type(buf) == BT_BUF_EVT) {
             h5_send(buf->data, HCI_EVENT_PKT, buf->len);
-            k_yield();
         } else {
             LOG_HEXDUMP_ERR(buf->data, buf->len, "Unexpected buffer in host_queue");
         }