Move payload CRC to layer 2

Layer 1 only does decoding of the FEC, but the CRC check for data integrity is
done in layer 2 now.

impl/src/config.h

@@ -16,7 +16,7 @@
 #define PAYLOAD_CHANNEL_CODE   LIQUID_FEC_CONV_V27P34
 #define PAYLOAD_MODULATION     LIQUID_MODEM_QAM16
 
-#define HEADER_CHANNEL_CODE   LIQUID_FEC_HAMMING84
+#define HEADER_CHANNEL_CODE   LIQUID_FEC_HAMMING128
 #define HEADER_MODULATION     LIQUID_MODEM_QPSK
 
 #define PAYLOAD_CRC_SCHEME    LIQUID_CRC_16

impl/src/layer1/packet_mod.c

@@ -81,7 +81,6 @@ result_t packet_mod_set_data(packet_mod_ctx_t *ctx, const unsigned char *data, s
 	memcpy(ctx->pkt_bytes, data, length);
 	ctx->length = length;
 
-	ctx->raw_data_crc = crc_generate_key(PAYLOAD_CRC_SCHEME, (unsigned char *)data, length);
 	ctx->raw_data_len = length;
 
 	ctx->state = DATA_RAW;
@@ -173,18 +172,12 @@ result_t packet_mod_add_header(packet_mod_ctx_t *ctx)
 	}
 
 	// build the header. All field are transferred in network byte order (big endian).
-	uint8_t header[5];
+	uint8_t header[2];
 
 	// set length
 	header[0] = (ctx->raw_data_len >> 8) & 0x07;
 	header[0] |= ctx->modcod << 3;
 	header[1] = (ctx->raw_data_len >> 0) & 0xFF;
-	// set raw data CRC
-	header[2] = (ctx->raw_data_crc >> 8) & 0xFF;
-	header[3] = (ctx->raw_data_crc >> 0) & 0xFF;
-
-	// append an 8-bit CRC to the header
-	crc_append_key(LIQUID_CRC_8, header, 4);
 
 	// note: the header is coded and modulated differently than the data.
 

impl/src/layer1/packet_mod.h

@@ -30,7 +30,6 @@ typedef struct
 	modem hdr_modem;
 	fec   hdr_fec;
 
-	uint16_t raw_data_crc;
 	uint16_t raw_data_len;
 
 	uint8_t modcod;

impl/src/layer1/rx.c

@@ -20,7 +20,7 @@
 
 #define SYMBOL_BUFFER_SIZE 16384
 
-#define HEADER_SIZE_BYTES 5 // including CRC
+#define HEADER_SIZE_BYTES 2
 #define FREQ_EST_L 24
 
 #define AGC_BW_ACQUISITION 5e-2f
@@ -370,18 +370,7 @@ result_t layer1_rx_process(layer1_rx_t *rx, const float complex *samples, size_t
 							break;
 						}
 
-						// CRC check
-						if(crc_check_key(LIQUID_CRC_8, header, HEADER_SIZE_BYTES) != LIQUID_OK) {
-							uint8_t expected_crc = crc_generate_key(LIQUID_CRC_8, header, 4);
-							LOG(LVL_WARN, "@%zu: Header CRC check failed! Expected: 0x%02x, received: 0x%02x",
-									rx->sample_index, expected_crc, header[4]);
-							rx->state = RX_STATE_ACQUISITION;
-							rx->callback(RX_EVT_HEADER_ERROR, rx, NULL, 0);
-							break;
-						}
-
 						rx->payload_len_bytes = (((uint16_t)header[0] << 8) | header[1]) & 0x07FF;
-						rx->payload_crc       = ((uint16_t)header[2] << 8) | header[3];
 						rx->modcod            = header[0] >> 3;
 
 						// check the received information
@@ -417,7 +406,6 @@ result_t layer1_rx_process(layer1_rx_t *rx, const float complex *samples, size_t
 
 						LOG(LVL_DUMP, "=== DECODED HEADER @%zu ===", rx->sample_index);
 						LOG(LVL_DUMP, "Payload length: %u symbols, %u bytes encoded, %u bytes decoded", rx->payload_len_symbols, rx->payload_len_enc_bytes, rx->payload_len_bytes);
-						LOG(LVL_DUMP, "CRC16: 0x%04x", rx->payload_crc);
 						LOG(LVL_DUMP, "======================");
 
 						//dump_array_cf(symbols_cpx, symbol_counter, 1.0f, "/tmp/hdr.cpx");
@@ -461,22 +449,25 @@ result_t layer1_rx_process(layer1_rx_t *rx, const float complex *samples, size_t
 									payload_enc, 8, sizeof(payload_enc), &nsyms));
 
 						fec payload_fec = modcod_create_fec(rx->modcod);
-						fec_decode(payload_fec, rx->payload_len_bytes, payload_enc, payload);
+						result_t res = fec_decode(payload_fec, rx->payload_len_bytes, payload_enc, payload);
 						fec_destroy(payload_fec);
 
+						if(res != LIQUID_OK) {
+							LOG(LVL_WARN, "@%zu: Payload decoding failed!", rx->sample_index);
+							rx->state = RX_STATE_ACQUISITION;
+							rx->callback(RX_EVT_DECODE_FAILED, rx, NULL, 0);
+							break;
+						}
+
 						// de-whiten the data
 						whitening_apply_in_place(payload, rx->payload_len_bytes);
 
-						int valid = crc_validate_message(PAYLOAD_CRC_SCHEME, payload, rx->payload_len_bytes, rx->payload_crc);
+						// note: CRC is included in data and checked in layer 2
 
 						payload[rx->payload_len_bytes] = '\0';
 
 						//dump_array_cf(symbols_cpx, symbol_counter, 1.0f, "/tmp/payload.cpx");
-						if(valid) {
 						rx->callback(RX_EVT_PACKET_RECEIVED, rx, payload, rx->payload_len_bytes);
-						} else {
-							rx->callback(RX_EVT_CHECKSUM_ERROR, rx, payload, rx->payload_len_bytes);
-						}
 
 						modem_destroy(rx->payload_demod);
 						rx->state = RX_STATE_ACQUISITION;

impl/src/layer1/rx.h

@@ -20,7 +20,7 @@ typedef enum {
 	RX_EVT_PACKET_RECEIVED,
 	RX_EVT_PREAMBLE_FOUND,
 	RX_EVT_HEADER_ERROR,
-	RX_EVT_CHECKSUM_ERROR,
+	RX_EVT_DECODE_FAILED,
 	RX_EVT_PACKET_DEBUG_INFO_COMPLETE,
 } rx_evt_t;
 
@@ -69,7 +69,6 @@ typedef struct layer1_rx_s
 	// Information from the decoded header
 	uint16_t payload_len_symbols;
 	uint16_t payload_len_bytes;
-	uint16_t payload_crc;
 	uint16_t payload_len_enc_bytes;
 	modcod_t modcod;
 

impl/src/main.c

@@ -116,7 +116,7 @@ void cb_rx(rx_evt_t evt, const struct layer1_rx_s *rx, uint8_t *packet_data, siz
 
 	switch(evt)
 	{
-		case RX_EVT_CHECKSUM_ERROR:
+		case RX_EVT_DECODE_FAILED:
 			//LOG(LVL_WARN, "Received a message of %zu bytes, but decoding failed.", packet_len);
 			//LOG(LVL_INFO, "=== FAILED PAYLOAD ===");
 			//hexdump(packet_data, packet_len);
@@ -138,7 +138,15 @@ void cb_rx(rx_evt_t evt, const struct layer1_rx_s *rx, uint8_t *packet_data, siz
 
 			block_tx_for(TX_SWITCH_BACKOFF_END_OF_PACKET_MS);
 
-			ret = write(m_tunfd, packet_data, packet_len);
+			unsigned int data_size = packet_len - crc_sizeof_key(PAYLOAD_CRC_SCHEME);
+
+			// FIXME: move to layer 2
+			if(!crc_check_key(PAYLOAD_CRC_SCHEME, packet_data, data_size)) {
+				LOG(LVL_WARN, "payload CRC check failed!");
+				break;
+			}
+
+			ret = write(m_tunfd, packet_data, data_size);
 			if(ret < 0) {
 				LOG(LVL_ERR, "write: %s", strerror(errno));
 			}
@@ -278,6 +286,16 @@ int main(int argc, char **argv)
 					break;
 				}
 
+				/* append CRC to packet */
+
+				unsigned int crc_size = crc_sizeof_key(PAYLOAD_CRC_SCHEME);
+				if((unsigned)ret > sizeof(packetbuf) - crc_size) {
+					LOG(LVL_ERR, "Packet is too large to append CRC! %i bytes.", ret);
+					break;
+				}
+
+				crc_append_key(PAYLOAD_CRC_SCHEME, packetbuf, ret);
+
 				LOG(LVL_DEBUG, "Transmitting packet with %d bytes.", ret);
 
 				RESULT_CHECK(layer1_tx_reset(&tx));

impl/test/layer1/test_loopback.c

@@ -12,6 +12,7 @@
 #include "logger.h"
 
 #include "utils.h"
+#include "config.h"
 
 #define RESULT_CHECK(stmt) { \
 	result_t res = stmt; \
@@ -77,9 +78,11 @@ void cb_rx(rx_evt_t evt, const layer1_rx_t *rx, uint8_t *packet_data, size_t pac
 {
 	(void)rx;
 
+	unsigned int data_size;
+
 	switch(evt)
 	{
-		case RX_EVT_CHECKSUM_ERROR:
+		case RX_EVT_DECODE_FAILED:
 			LOG(LVL_ERR, "Received a message of %zu bytes, but decoding failed.", packet_len);
 			LOG(LVL_INFO, "=== FAILED PAYLOAD ===");
 			hexdump(packet_data, packet_len);
@@ -87,10 +90,19 @@ void cb_rx(rx_evt_t evt, const layer1_rx_t *rx, uint8_t *packet_data, size_t pac
 			break;
 
 		case RX_EVT_PACKET_RECEIVED:
-			LOG(LVL_INFO, "A message of %zu bytes was decoded successfully.", packet_len);
+			data_size = packet_len - crc_sizeof_key(PAYLOAD_CRC_SCHEME);
+
 			LOG(LVL_INFO, "=== DECODED PAYLOAD (%4zu bytes) ===", packet_len);
-			hexdump(packet_data, packet_len < 64 ? packet_len : 64);
+			hexdump(packet_data, packet_len);
 			LOG(LVL_INFO, "====================================");
+
+			// FIXME: move to layer 2
+			if(!crc_check_key(PAYLOAD_CRC_SCHEME, packet_data, data_size)) {
+				LOG(LVL_WARN, "payload CRC check failed!");
+				break;
+			}
+
+			LOG(LVL_INFO, "A message of %zu bytes was decoded successfully.", packet_len);
 			break;
 
 		case RX_EVT_HEADER_ERROR:
@@ -127,19 +139,24 @@ int main(void)
 
 	RESULT_CHECK(layer1_tx_reset(&tx));
 
-	uint8_t packetbuf1[] = "Hello World! 1234567890";
+	uint8_t packetbuf1[64] = "Hello World! 1234567890";
-	size_t l = sizeof(packetbuf1);
+	size_t crc_size = crc_sizeof_key(PAYLOAD_CRC_SCHEME);
+	size_t l = strlen((char*)packetbuf1);
 
-	LOG(LVL_INFO, "Transmitting packet with %zd bytes.", l);
+	crc_append_key(PAYLOAD_CRC_SCHEME, packetbuf1, l);
 
-	RESULT_CHECK(layer1_tx_add_packet_to_burst(&tx, packetbuf1, l));
+	LOG(LVL_INFO, "Transmitting packet with %zd bytes.", l + crc_size);
 
-	uint8_t packetbuf2[] = "This is just a test message. Just writing some stuff here to create a longer packet.";
+	RESULT_CHECK(layer1_tx_add_packet_to_burst(&tx, packetbuf1, l + crc_size));
-	l = sizeof(packetbuf2);
 
-	LOG(LVL_INFO, "Transmitting packet with %zd bytes.", l);
+	uint8_t packetbuf2[128] = "This is just a test message. Just writing some stuff here to create a longer packet.";
+	l = strlen((char*)packetbuf2);
 
-	RESULT_CHECK(layer1_tx_add_packet_to_burst(&tx, packetbuf2, l));
+	crc_append_key(PAYLOAD_CRC_SCHEME, packetbuf2, l);
+
+	LOG(LVL_INFO, "Transmitting packet with %zd bytes.", l + crc_size);
+
+	RESULT_CHECK(layer1_tx_add_packet_to_burst(&tx, packetbuf2, l + crc_size));
 
 	RESULT_CHECK(layer1_tx_finalize_burst(&tx));
 
@@ -150,7 +167,7 @@ int main(void)
 
 	// ** Simulate channel effects **
 	channel_cccf ch = channel_cccf_create();
-	channel_cccf_add_awgn(ch, -30, 10);
+	channel_cccf_add_awgn(ch, -30, 30);
 	//channel_cccf_add_carrier_offset(ch, 0.05f, 1.23f);
 
 	float complex whole_burst_ch[burst_len];

impl/test/layer1/test_rx_file.c

@@ -64,9 +64,11 @@ void cb_rx(rx_evt_t evt, const layer1_rx_t *rx, uint8_t *packet_data, size_t pac
 	(void)packet_len;
 	(void)rx;
 
+	unsigned int data_size;
+
 	switch(evt)
 	{
-		case RX_EVT_CHECKSUM_ERROR:
+		case RX_EVT_DECODE_FAILED:
 			//LOG(LVL_WARN, "Received a message of %zu bytes, but decoding failed.", packet_len);
 			//LOG(LVL_INFO, "=== FAILED PAYLOAD ===");
 			//hexdump(packet_data, packet_len);
@@ -84,6 +86,14 @@ void cb_rx(rx_evt_t evt, const layer1_rx_t *rx, uint8_t *packet_data, size_t pac
 			//hexdump(packet_data, packet_len < 64 ? packet_len : 64);
 			//LOG(LVL_INFO, "====================================");
 
+			data_size = packet_len - crc_sizeof_key(PAYLOAD_CRC_SCHEME);
+
+			// FIXME: move to layer 2
+			if(!crc_check_key(PAYLOAD_CRC_SCHEME, packet_data, data_size)) {
+				LOG(LVL_WARN, "payload CRC check failed!");
+				break;
+			}
+
 			m_rx_stats.successful_decodes++;
 			break;