CP: Don't update sequence number on command retry probes

Fixes: #274
Signed-off-by: Siddharth Chandrasekaran <sidcha.dev@gmail.com>

Author: sidcha

src/osdp_common.h

@@ -413,6 +413,7 @@ struct osdp_pd {
 	int state;             /* FSM state (CP mode only) */
 	int phy_state;         /* phy layer FSM state (CP mode only) */
 	int phy_retry_count;   /* command retry counter */
+	int phy_tx_seq;        /* seq number embedded in last TX packet */
 	uint32_t wait_ms;      /* wait time in MS to retry communication */
 	tick_t tstamp;         /* Last POLL command issued time in ticks */
 	tick_t sc_tstamp;      /* Last received secure reply time in ticks */

src/osdp_cp.c

@@ -814,7 +814,12 @@ static int cp_phy_state_update(struct osdp_pd *pd)
 		pd->phy_state = OSDP_CP_PHY_STATE_SEND_CMD;
 		__fallthrough;
 	case OSDP_CP_PHY_STATE_SEND_CMD:
-		/* Check if we have any commands in the queue */
+		if (pd->phy_retry_count > 0) {
+			struct osdp_channel *channel = &pd_to_osdp(pd)->channel;
+			if (channel->flush)
+				channel->flush(channel->data);
+			pd->seq_number = pd->phy_tx_seq - 1;
+		}
 		if (cp_build_and_send_packet(pd)) {
 			LOG_ERR("Failed to build/send packet for CMD: %s(%02x)",
 				osdp_cmd_name(pd->cmd_id), pd->cmd_id);

src/osdp_phy.c

@@ -233,6 +233,7 @@ int osdp_phy_packet_init(struct osdp_pd *pd, uint8_t *buf, int max_len)
 		id = pd->cmd_id;
 	}
 	pkt->control = phy_get_next_seq_number(pd);
+	pd->phy_tx_seq = pkt->control & PKT_CONTROL_SQN;
 	if (is_pd_mode(pd) ||
 	    (is_cp_mode(pd) && ISSET_FLAG(pd, PD_FLAG_CP_USE_CRC))) {
 		pkt->control |= PKT_CONTROL_CRC;
@@ -899,6 +900,7 @@ void osdp_phy_state_reset(struct osdp_pd *pd, bool is_error)
 	pd->packet_buf = osdp_tx_staging_buf(pd);
 	if (is_error) {
 		pd->phy_retry_count = 0;
+		pd->phy_tx_seq = 0;
 		phy_reset_seq_number(pd);
 		if (channel->flush) {
 			channel->flush(channel->data);