Adding LLC-XID encoder / decoder and unit test
The lle-xid encoder/decoder is needed to encode and decode llc
xid parameter messages. We need this to exchange sndcp-parameters
(SNDCP-XID) and also simple parameters such as encryption IOVs
Change-Id: Ia06e4cb08bf9b48c2a4682606d1b1a91d19a9d37
diff --git a/openbsc/src/gprs/Makefile.am b/openbsc/src/gprs/Makefile.am
index 6dc7e16..8cbdd91 100644
--- a/openbsc/src/gprs/Makefile.am
+++ b/openbsc/src/gprs/Makefile.am
@@ -28,7 +28,7 @@
sgsn_ctrl.c sgsn_auth.c gprs_subscriber.c \
gprs_utils.c gprs_gsup_client.c \
sgsn_cdr.c sgsn_ares.c \
- oap.c oap_messages.c
+ oap.c oap_messages.c gprs_llc_xid.c
osmo_sgsn_LDADD = \
$(top_builddir)/src/libcommon/libcommon.a \
-lgtp $(OSMO_LIBS) $(LIBOSMOABIS_LIBS) $(LIBCARES_LIBS) \
diff --git a/openbsc/src/gprs/gprs_llc_xid.c b/openbsc/src/gprs/gprs_llc_xid.c
new file mode 100644
index 0000000..4b1685e
--- /dev/null
+++ b/openbsc/src/gprs/gprs_llc_xid.c
@@ -0,0 +1,262 @@
+/* GPRS LLC XID field encoding/decoding as per 3GPP TS 44.064 */
+
+/* (C) 2016 by sysmocom s.f.m.c. GmbH <info@sysmocom.de>
+ * All Rights Reserved
+ *
+ * Author: Philipp Maier
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include <errno.h>
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/talloc.h>
+
+#include <openbsc/debug.h>
+#include <openbsc/gprs_llc.h>
+#include <openbsc/sgsn.h>
+#include <openbsc/gprs_llc_xid.h>
+
+/* Parse XID parameter field */
+static int decode_xid_field(struct gprs_llc_xid_field *xid_field,
+ const uint8_t *src, uint8_t src_len)
+{
+ uint8_t xl;
+ uint8_t type;
+ uint8_t len;
+ int src_counter = 0;
+
+ /* Exit immediately if it is clear that no
+ * parseable data is present */
+ if (src_len < 1 || !src)
+ return -EINVAL;
+
+ /* Extract header info */
+ xl = (*src >> 7) & 1;
+ type = (*src >> 2) & 0x1F;
+
+ /* Extract length field */
+ len = (*src) & 0x3;
+ src++;
+ src_counter++;
+ if (xl) {
+ if (src_len < 2)
+ return -EINVAL;
+ len = (len << 6) & 0xC0;
+ len |= ((*src) >> 2) & 0x3F;
+ src++;
+ src_counter++;
+ }
+
+ /* Fill out struct */
+ xid_field->type = type;
+ xid_field->data_len = len;
+ if (len > 0) {
+ if (src_len < src_counter + len)
+ return -EINVAL;
+ xid_field->data =
+ talloc_memdup(xid_field,src,xid_field->data_len);
+ } else
+ xid_field->data = NULL;
+
+ /* Return consumed length */
+ return src_counter + len;
+}
+
+/* Encode XID parameter field */
+static int encode_xid_field(uint8_t *dst, int dst_maxlen,
+ const struct gprs_llc_xid_field *xid_field)
+{
+ int xl = 0;
+
+ /* When the length does not fit into 2 bits,
+ * we need extended length fields */
+ if (xid_field->data_len > 3)
+ xl = 1;
+
+ /* Exit immediately if it is clear that no
+ * encoding result can be stored */
+ if (dst_maxlen < xid_field->data_len + 1 + xl)
+ return -EINVAL;
+
+ /* There are only 5 bits reserved for the type, exit on exceed */
+ if (xid_field->type > 31)
+ return -EINVAL;
+
+ /* Encode header */
+ memset(dst, 0, dst_maxlen);
+ if (xl)
+ dst[0] |= 0x80;
+ dst[0] |= (((xid_field->type) & 0x1F) << 2);
+
+ if (xl) {
+ dst[0] |= (((xid_field->data_len) >> 6) & 0x03);
+ dst[1] = ((xid_field->data_len) << 2) & 0xFC;
+ } else
+ dst[0] |= ((xid_field->data_len) & 0x03);
+
+ /* Append payload data */
+ if (xid_field->data && xid_field->data_len)
+ memcpy(dst + 1 + xl, xid_field->data, xid_field->data_len);
+
+ /* Return generated length */
+ return xid_field->data_len + 1 + xl;
+}
+
+/* Transform a list with XID fields into a XID message (dst) */
+int gprs_llc_compile_xid(uint8_t *dst, int dst_maxlen,
+ const struct llist_head *xid_fields)
+{
+ struct gprs_llc_xid_field *xid_field;
+ int rc;
+ int byte_counter = 0;
+
+ OSMO_ASSERT(xid_fields);
+ OSMO_ASSERT(dst);
+
+ llist_for_each_entry_reverse(xid_field, xid_fields, list) {
+ /* Encode XID-Field */
+ rc = encode_xid_field(dst, dst_maxlen, xid_field);
+ if (rc < 0)
+ return -EINVAL;
+
+ /* Advance pointer and lower maxlen for the
+ * next encoding round */
+ dst += rc;
+ byte_counter += rc;
+ dst_maxlen -= rc;
+ }
+
+ /* Return generated length */
+ return byte_counter;
+}
+
+/* Transform a XID message (dst) into a list of XID fields */
+struct llist_head *gprs_llc_parse_xid(const void *ctx, const uint8_t *src,
+ int src_len)
+{
+ struct gprs_llc_xid_field *xid_field;
+ struct llist_head *xid_fields;
+
+ int rc;
+ int max_loops = src_len;
+
+ OSMO_ASSERT(src);
+
+ xid_fields = talloc_zero(ctx, struct llist_head);
+ INIT_LLIST_HEAD(xid_fields);
+
+ while (1) {
+ /* Bail in case decode_xid_field() constantly returns zero */
+ if (max_loops <= 0) {
+ talloc_free(xid_fields);
+ return NULL;
+ }
+
+ /* Decode XID field */
+ xid_field = talloc_zero(xid_fields, struct gprs_llc_xid_field);
+ rc = decode_xid_field(xid_field, src, src_len);
+
+ /* Immediately stop on error */
+ if (rc < 0) {
+ talloc_free(xid_fields);
+ return NULL;
+ }
+
+ /* Add parsed XID field to list */
+ llist_add(&xid_field->list, xid_fields);
+
+ /* Advance pointer and lower dst_len for the next
+ * decoding round */
+ src += rc;
+ src_len -= rc;
+
+ /* We are (scuccessfully) done when no further byes are left */
+ if (src_len == 0)
+ return xid_fields;
+
+ max_loops--;
+ }
+}
+
+/* Create a duplicate of an XID-Field */
+struct gprs_llc_xid_field *gprs_llc_dup_xid_field(const void *ctx, const struct
+ gprs_llc_xid_field
+ *xid_field)
+{
+ struct gprs_llc_xid_field *dup;
+
+ OSMO_ASSERT(xid_field);
+
+ /* Create a copy of the XID field in memory */
+ dup = talloc_memdup(ctx, xid_field, sizeof(*xid_field));
+ dup->data = talloc_memdup(ctx, xid_field->data, xid_field->data_len);
+
+ /* Unlink duplicate from source list */
+ INIT_LLIST_HEAD(&dup->list);
+
+ return dup;
+}
+
+/* Copy an llist with xid fields */
+struct llist_head *gprs_llc_copy_xid(const void *ctx,
+ const struct llist_head *xid_fields)
+{
+ struct gprs_llc_xid_field *xid_field;
+ struct llist_head *xid_fields_copy;
+
+ OSMO_ASSERT(xid_fields);
+
+ xid_fields_copy = talloc_zero(ctx, struct llist_head);
+ INIT_LLIST_HEAD(xid_fields_copy);
+
+ /* Create duplicates and add them to the target list */
+ llist_for_each_entry(xid_field, xid_fields, list) {
+ llist_add(&gprs_llc_dup_xid_field(ctx, xid_field)->list,
+ xid_fields_copy);
+ }
+
+ return xid_fields_copy;
+}
+
+/* Dump a list with XID fields (Debug) */
+void gprs_llc_dump_xid_fields(const struct llist_head *xid_fields,
+ unsigned int logl)
+{
+ struct gprs_llc_xid_field *xid_field;
+
+ OSMO_ASSERT(xid_fields);
+
+ llist_for_each_entry(xid_field, xid_fields, list) {
+ if (xid_field->data_len) {
+ OSMO_ASSERT(xid_field->data);
+ LOGP(DLLC, logl,
+ "XID: type=%d, data_len=%d, data=%s\n",
+ xid_field->type, xid_field->data_len,
+ osmo_hexdump_nospc(xid_field->data,
+ xid_field->data_len));
+ } else {
+ LOGP(DLLC, logl,
+ "XID: type=%d, data_len=%d, data=NULL\n",
+ xid_field->type, xid_field->data_len);
+ }
+ }
+}