commit 4f4905fac590be8feea0b22010444ed40d7b11b5
author Philipp Maier <pmaier@sysmocom.de> Fri Nov 30 13:36:12 2018 +0100
committer Harald Welte <laforge@gnumonks.org> Sat Dec 08 19:29:34 2018 +0000
tree 26870a2f21aca35188d3c34bd5027be45603e562
parent e190e032d97d6a67524efc4f6169a30789c86048

gsm0808: add encoder for cause codes and use it

At the moment the all gsm0808 cause codes are encoded directly using the
tlv API directly to put a one byte TLV field. This works ok for most
situations where the cause code consists of a single byte. However,
gsm0808 specifies a two byte cause code model where cause codes may be
extended up to two bytes. Instead of implementing the encoding over and
over and again, let's rather have an encoder function we can call.

- Add an encoder function that can generate single byte and extended
  cause codeds and makes the length decision automatically.

- Use only this function to append cause codes

Change-Id: I71d58fad89502a43532f60717ca022c15c73f8bb

src/gsm/gsm0808.c

diff --git a/src/gsm/gsm0808.c b/src/gsm/gsm0808.c
index c0d5f39..e951ab1 100644
--- a/src/gsm/gsm0808.c
+++ b/src/gsm/gsm0808.c
@@ -141,7 +141,7 @@
 		return NULL;
 
 	msgb_v_put(msg, BSS_MAP_MSG_RESET);
-	msgb_tlv_put(msg, GSM0808_IE_CAUSE, 1, &cause);
+	gsm0808_enc_cause(msg, cause);
 	msg->l3h = msgb_tv_push(msg, BSSAP_MSG_BSS_MANAGEMENT, msgb_length(msg));
 
 	return msg;
@@ -190,7 +190,7 @@
 
 	msg->l3h = msgb_tv_put(msg, BSSAP_MSG_BSS_MANAGEMENT, 4);
 	msgb_v_put(msg, BSS_MAP_MSG_CLEAR_CMD);
-	msgb_tlv_put(msg, GSM0808_IE_CAUSE, 1, &cause);
+	gsm0808_enc_cause(msg, cause);
 
 	return msg;
 }
@@ -273,7 +273,7 @@
 
 	msgb_v_put(msg, BSS_MAP_MSG_CIPHER_MODE_REJECT);
 
-	msgb_tlv_put(msg, GSM0808_IE_CAUSE, 1, (const uint8_t *)&cause);
+	gsm0808_enc_cause(msg, cause);
 
 	msg->l3h = msgb_tv_push(msg, BSSAP_MSG_BSS_MANAGEMENT, msgb_length(msg));
 
@@ -286,18 +286,22 @@
  *  \returns callee-allocated msgb with BSSMAP Cipher Mode Reject message */
 struct msgb *gsm0808_create_cipher_reject_ext(enum gsm0808_cause_class class, uint8_t ext)
 {
-	uint8_t c[2];
+	uint16_t cause;
 	struct msgb *msg = msgb_alloc_headroom(BSSMAP_MSG_SIZE, BSSMAP_MSG_HEADROOM,
 					       "bssmap: cipher mode reject");
 	if (!msg)
 		return NULL;
 
-	c[0] = 0x80 | (class << 4); /* set the high bit to indicate extended cause */
-	c[1] = ext;
+	/* Set cause code class in the upper byte */
+	cause = 0x80 | (class << 4);
+	cause = cause << 8;
+
+	/* Set cause code extension in the lower byte */
+	cause |= ext;
 
 	msgb_v_put(msg, BSS_MAP_MSG_CIPHER_MODE_REJECT);
 
-	msgb_tlv_put(msg, GSM0808_IE_CAUSE, 2, c);
+	gsm0808_enc_cause(msg, cause);
 
 	msg->l3h = msgb_tv_push(msg, BSSAP_MSG_BSS_MANAGEMENT, msgb_length(msg));
 
@@ -572,7 +576,7 @@
 		return NULL;
 
 	msgb_v_put(msg, BSS_MAP_MSG_ASSIGMENT_FAILURE);
-	msgb_tlv_put(msg, GSM0808_IE_CAUSE, 1, &cause);
+	gsm0808_enc_cause(msg, cause);
 
 	/* RR cause 3.2.2.22 */
 	if (rr_cause)
@@ -614,7 +618,7 @@
 		return NULL;
 
 	msgb_v_put(msg, BSS_MAP_MSG_CLEAR_RQST);
-	msgb_tlv_put(msg, GSM0808_IE_CAUSE, 1, &cause);
+	gsm0808_enc_cause(msg, cause);
 	msg->l3h = msgb_tv_push(msg, BSSAP_MSG_BSS_MANAGEMENT, msgb_length(msg));
 
 	return msg;
@@ -751,7 +755,7 @@
 	msgb_v_put(msg, BSS_MAP_MSG_HANDOVER_REQUIRED);
 
 	/* Cause, 3.2.2.5 */
-	msgb_tlv_put(msg, GSM0808_IE_CAUSE, params->cause & 0x80? 2 : 1, (const uint8_t*)&params->cause);
+	gsm0808_enc_cause(msg, params->cause);
 
 	/* Cell Identifier List, 3.2.2.27 */
 	gsm0808_enc_cell_id_list2(msg, &params->cil);
@@ -876,7 +880,7 @@
 	msgb_v_put(msg, BSS_MAP_MSG_HANDOVER_FAILURE);
 
 	/* Cause, 3.2.2.5 */
-	msgb_tlv_put(msg, GSM0808_IE_CAUSE, params->cause & 0x80? 2 : 1, (const uint8_t*)&params->cause);
+	gsm0808_enc_cause(msg, params->cause);
 
 	/* RR Cause, 3.2.2.22 */
 	if (params->rr_cause_present)
@@ -907,7 +911,7 @@
 	msgb_v_put(msg, BSS_MAP_MSG_HANDOVER_PERFORMED);
 
 	/* Cause, 3.2.2.5 */
-	msgb_tlv_put(msg, GSM0808_IE_CAUSE, gsm0808_cause_ext(params->cause) ? 2 : 1, (const uint8_t *)&params->cause);
+	gsm0808_enc_cause(msg, params->cause);
 
 	/* Cell Identifier, 3.2.2.17 */
 	gsm0808_enc_cell_id(msg, &params->cell_id);

src/gsm/gsm0808_utils.c

diff --git a/src/gsm/gsm0808_utils.c b/src/gsm/gsm0808_utils.c
index c58d828..38a8664 100644
--- a/src/gsm/gsm0808_utils.c
+++ b/src/gsm/gsm0808_utils.c
@@ -48,6 +48,32 @@
  *  \file gsm0808_utils.c
  */
 
+/*! Encode TS 08.08 AoIP Cause IE
+ *  \param[out] msg Message Buffer to which to append IE
+ *  \param[in] cause Cause code to be used in IE
+ *  \returns number of bytes added to \a msg */
+uint8_t gsm0808_enc_cause(struct msgb *msg, uint16_t cause)
+{
+	/* See also 3GPP TS 48.008 3.2.2.5 Cause */
+	uint8_t *old_tail;
+	bool extended;
+
+	old_tail = msg->tail;
+
+	extended = gsm0808_cause_ext(cause >> 8);
+
+	msgb_put_u8(msg, GSM0808_IE_CAUSE);
+	if (extended) {
+		msgb_put_u8(msg, 2);
+		msgb_put_u16(msg, cause);
+	} else {
+		msgb_put_u8(msg, 1);
+		msgb_put_u8(msg, (uint8_t) (cause & 0xFF));
+	}
+
+	return (uint8_t) (msg->tail - old_tail);
+}
+
 /*! Encode TS 08.08 AoIP transport address IE
  *  \param[out] msg Message Buffer to which to append IE
  *  \param[in] ss Socket Address to be used in IE

src/gsm/libosmogsm.map

diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index e9a9e4f..dc4e0a6 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -183,6 +183,7 @@
 gsm0808_create_handover_failure;
 gsm0808_create_handover_performed;
 gsm0808_prepend_dtap_header;
+gsm0808_enc_cause;
 gsm0808_enc_aoip_trasp_addr;
 gsm0808_dec_aoip_trasp_addr;
 gsm0808_enc_speech_codec;