Add a GSM RLP decoder and encoder
This code implements a decoder and encoder for the RLP (Radio Link
Protocol) as used in the bearer channel of GSM CSD (Circuit Switched
Data).
Change-Id: I2d9bd8eb4f0cd0f72c436996767b199429596917
diff --git a/include/osmocom/gsm/Makefile.am b/include/osmocom/gsm/Makefile.am
index f840a27..5678a51 100644
--- a/include/osmocom/gsm/Makefile.am
+++ b/include/osmocom/gsm/Makefile.am
@@ -48,6 +48,7 @@
l1sap.h \
oap.h \
oap_client.h \
+ rlp.h \
rsl.h \
rxlev_stat.h \
sysinfo.h \
diff --git a/include/osmocom/gsm/rlp.h b/include/osmocom/gsm/rlp.h
new file mode 100644
index 0000000..47b0a6c
--- /dev/null
+++ b/include/osmocom/gsm/rlp.h
@@ -0,0 +1,81 @@
+/*
+ * GSM RLP (Radio Link Protocol) as used in CSD (3GPP TS 44.022)
+ *
+ * Copyright (C) 2022-2023 Harald Welte <laforge@osmocom.org>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+
+
+#pragma once
+#include <stdint.h>
+#include <stdbool.h>
+#include <osmocom/core/utils.h>
+
+/*! \defgroup rlp GSM RLP (Radio Link Protocol) as used in CSD (3GPP TS 24.022)
+ * @{
+ * \file rlp.h */
+
+/*! RLP frame type as per 3GPP TS 24.022 Section 5.2.1 */
+enum osmo_rlp_ftype {
+ OSMO_RLP_FT_U,
+ OSMO_RLP_FT_S,
+ OSMO_RLP_FT_IS,
+};
+extern const struct value_string osmo_rlp_ftype_vals[];
+
+/*! RLP U-Frame Type as per 3GPP TS 24.022 Section 5.2.1 */
+enum osmo_rlp_u_ftype {
+ OSMO_RLP_U_FT_SABM = 0x07,
+ OSMO_RLP_U_FT_UA = 0x0c,
+ OSMO_RLP_U_FT_DISC = 0x08,
+ OSMO_RLP_U_FT_DM = 0x03,
+ OSMO_RLP_U_FT_NULL = 0x0f,
+ OSMO_RLP_U_FT_UI = 0x00,
+ OSMO_RLP_U_FT_XID = 0x17,
+ OSMO_RLP_U_FT_TEST = 0x1c,
+ OSMO_RLP_U_FT_REMAP = 0x11,
+};
+extern const struct value_string osmo_rlp_ftype_u_vals[];
+
+/*! RLP S-Frame type as per 3GPP TS 24.022 Section 5.2.1 */
+enum osmo_rlp_s_ftype {
+ OSMO_RLP_S_FT_RR = 0,
+ OSMO_RLP_S_FT_REJ = 2,
+ OSMO_RLP_S_FT_RNR = 1,
+ OSMO_RLP_S_FT_SREJ = 3,
+};
+extern const struct value_string osmo_rlp_ftype_s_vals[];
+
+/*! Data structure representing one decoded RLP frame */
+struct osmo_rlp_frame_decoded {
+ uint8_t version;
+ enum osmo_rlp_ftype ftype;
+ enum osmo_rlp_u_ftype u_ftype;
+ enum osmo_rlp_s_ftype s_ftype;
+ bool c_r;
+ bool p_f;
+ uint8_t s_bits;
+ uint16_t n_s;
+ uint16_t n_r;
+ uint32_t fcs;
+ uint8_t info[536/8];
+ uint16_t info_len;
+};
+
+int osmo_rlp_decode(struct osmo_rlp_frame_decoded *out, uint8_t version, const uint8_t *data, size_t data_len);
+int osmo_rlp_encode(uint8_t *out, size_t out_size, const struct osmo_rlp_frame_decoded *in);
+uint32_t osmo_rlp_fcs_compute(const uint8_t *in, size_t in_len);
+
+/*! @} */