1 files changed, 95 insertions, 0 deletions
diff --git a/src/gsm/iuup_crc.c b/src/gsm/iuup_crc.c
new file mode 100644
index 00000000..1cefe5a3
--- /dev/null
+++ b/src/gsm/iuup_crc.c
@@ -0,0 +1,95 @@
+#include <stdint.h>
+#include <stdio.h>
+
+#include <osmocom/core/crc8gen.h>
+#include <osmocom/core/crc16gen.h>
+
+static const struct osmo_crc8gen_code iuup_hdr_crc_code = {
+	.bits = 6,
+	.poly = 47,
+	.init = 0,
+	.remainder = 0,
+};
+
+static const struct osmo_crc16gen_code iuup_data_crc_code = {
+	.bits = 10,
+	.poly = 563,
+	.init = 0,
+	.remainder = 0,
+};
+
+static int iuup_get_payload_offset(const uint8_t *iuup_pdu)
+{
+	uint8_t pdu_type = iuup_pdu[0] >> 4;
+	switch (pdu_type) {
+	case 0:
+	case 14:
+		return 4;
+	case 1:
+		return 3;
+	default:
+		return -1;
+	}
+}
+
+int osmo_iuup_compute_payload_crc(const uint8_t *iuup_pdu, unsigned int pdu_len)
+{
+	ubit_t buf[1024*8];
+	uint8_t pdu_type;
+	int offset, payload_len_bytes;
+
+	if (pdu_len < 1)
+		return -1;
+
+	pdu_type = iuup_pdu[0] >> 4;
+
+	/* Type 1 has no CRC */
+	if (pdu_type == 1)
+		return 0;
+
+	offset = iuup_get_payload_offset(iuup_pdu, pdu_len);
+	if (offset < 0)
+		return offset;
+
+	if (pdu_len < offset)
+		return -1;
+
+	payload_len_bytes = pdu_eln - offset;
+	osmo_pbit2ubit(buf, iuup_pdu+offset, payload_len_bytes*8);
+	return osmo_crc16gen_compute_bits(&iuup_data_crc_code, buf, payload_len_bytes*8);
+}
+
+int osmo_iuup_compute_header_crc(const uint8_t *iuup_pdu, unsigned int pdu_len)
+{
+	ubit_t buf[2*8];
+
+	if (pdu_len < 2)
+		return -1;
+
+	osmo_pbit2ubit(buf, iuup_pdu, 2*8);
+	return osmo_crc8gen_compute_bits(&iuup_hdr_crc_code, buf, 2*8);
+}
+
+#if 0
+/* Frame 29 of MobileOriginatingCall_AMR.cap */
+const uint8_t iuup_frame29[] = {
+	0x02, 0x00, 0x7d, 0x27, 0x55, 0x00, 0x88, 0xb6, 0x66, 0x79, 0xe1, 0xe0,
+	0x01, 0xe7, 0xcf, 0xf0, 0x00, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+};
+
+
+int main(int argc, char **argv)
+{
+	ubit_t buf[1024*8];
+	int rc;
+
+	osmo_pbit2ubit(buf, iuup_frame29, 2*8);
+	rc = osmo_crc8gen_compute_bits(&iuup_hdr_crc_code, buf, 2*8);
+	printf("Header CRC = 0x%02x\n", rc);
+
+	osmo_pbit2ubit(buf, iuup_frame29+4, 31*8);
+	rc = osmo_crc16gen_compute_bits(&iuup_data_crc_code, buf, 31*8);
+	printf("Payload CRC = 0x%03x\n", rc);
+}
+#endif