CP: Fix bug in sequence number progression

Commit 7f6d3c3 introduced a fix for the long-standing sequence number
mismatch issue by an explicit sequence progression logic. By this logic,
when there are no errors, the sequence number is progressed. But it
failed to handle the case when the PD respond with a valid packet, and
the CP finds an application layer error in the packet, the sequence
number must be progressed as the PD would have (correctly) incremented
it's sequence number.

To fix this, let's introduce a new CP error code to use for any future
application layer errors and use that to hook into the sequence
progression logic.

Fixes: #244
Fixes: 7f6d3c3
Signed-off-by: Siddharth Chandrasekaran <sidcha.dev@gmail.com>
(cherry picked from commit b922873)

Author: sidcha

src/osdp_cp.c

@@ -53,6 +53,7 @@ enum osdp_cp_error_e {
 	OSDP_CP_ERR_INPROG = -5,
 	OSDP_CP_ERR_UNKNOWN = -6,
 	OSDP_CP_ERR_SEQ_NUM = -7,
+	OSDP_CP_ERR_APP = -8, /* Application layer error */
 };
 
 struct cp_cmd_node {
@@ -640,7 +641,7 @@ static int cp_decode_response(struct osdp_pd *pd, uint8_t *buf, int len)
 		osdp_compute_session_keys(pd);
 		if (osdp_verify_pd_cryptogram(pd) != 0) {
 			LOG_ERR("Failed to verify PD cryptogram");
-			return OSDP_CP_ERR_GENERIC;
+			return OSDP_CP_ERR_APP;
 		}
 		ret = OSDP_CP_ERR_NONE;
 		break;
@@ -878,19 +879,20 @@ static int cp_phy_state_update(struct osdp_pd *pd)
 		break;
 	case OSDP_CP_PHY_STATE_REPLY_WAIT:
 		rc = cp_process_reply(pd);
-		if (rc == OSDP_CP_ERR_NONE) {
+		if (rc == OSDP_CP_ERR_NONE || rc == OSDP_CP_ERR_APP) {
 			pd->tstamp = osdp_millis_now();
 			osdp_phy_progress_sequence(pd);
-			cp_phy_state_done(pd);
-			return OSDP_CP_ERR_NONE;
 		}
-		if (rc == OSDP_CP_ERR_SEQ_NUM ||
+		if (rc == OSDP_CP_ERR_NONE ||
+		    rc == OSDP_CP_ERR_SEQ_NUM ||
 		    (rc == OSDP_CP_ERR_UNKNOWN && pd->cmd_id == CMD_POLL &&
 		     ISSET_FLAG(pd, OSDP_FLAG_IGN_UNSOLICITED))) {
 			cp_phy_state_done(pd);
 			return OSDP_CP_ERR_NONE;
 		}
-		if (rc == OSDP_CP_ERR_GENERIC || rc == OSDP_CP_ERR_UNKNOWN) {
+		if (rc == OSDP_CP_ERR_GENERIC ||
+		    rc == OSDP_CP_ERR_UNKNOWN ||
+		    rc == OSDP_CP_ERR_APP) {
 			goto error;
 		}
 		if (rc == OSDP_CP_ERR_RETRY_CMD) {