emu: Use OpenBSC code to decode the LLC and add assertions
Use the OpenBSC SGSN code to parse the LLC data and look into
the data we receive. Add assertions to verify the the sequence
number is increasing.
diff --git a/tests/emu/openbsc_clone.c b/tests/emu/openbsc_clone.c
new file mode 100644
index 0000000..707819b
--- /dev/null
+++ b/tests/emu/openbsc_clone.c
@@ -0,0 +1,216 @@
+/* (C) 2009-2010 by Harald Welte <laforge@gnumonks.org>
+ *
+ * All Rights Reserved
+ *
+ * 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 "openbsc_clone.h"
+
+#include <gprs_debug.h>
+
+#include <osmocom/core/utils.h>
+
+#include <errno.h>
+
+/* Section 6.4 Commands and Responses */
+enum gprs_llc_u_cmd {
+ GPRS_LLC_U_DM_RESP = 0x01,
+ GPRS_LLC_U_DISC_CMD = 0x04,
+ GPRS_LLC_U_UA_RESP = 0x06,
+ GPRS_LLC_U_SABM_CMD = 0x07,
+ GPRS_LLC_U_FRMR_RESP = 0x08,
+ GPRS_LLC_U_XID = 0x0b,
+ GPRS_LLC_U_NULL_CMD = 0x00,
+};
+
+#define LLC_ALLOC_SIZE 16384
+#define UI_HDR_LEN 3
+#define N202 4
+#define CRC24_LENGTH 3
+
+static const struct value_string llc_cmd_strs[] = {
+ { GPRS_LLC_NULL, "NULL" },
+ { GPRS_LLC_RR, "RR" },
+ { GPRS_LLC_ACK, "ACK" },
+ { GPRS_LLC_RNR, "RNR" },
+ { GPRS_LLC_SACK, "SACK" },
+ { GPRS_LLC_DM, "DM" },
+ { GPRS_LLC_DISC, "DISC" },
+ { GPRS_LLC_UA, "UA" },
+ { GPRS_LLC_SABM, "SABM" },
+ { GPRS_LLC_FRMR, "FRMR" },
+ { GPRS_LLC_XID, "XID" },
+ { GPRS_LLC_UI, "UI" },
+ { 0, NULL }
+};
+
+int gprs_llc_hdr_parse(struct gprs_llc_hdr_parsed *ghp,
+ const uint8_t *llc_hdr, int len)
+{
+ const uint8_t *ctrl = llc_hdr+1;
+
+ if (len <= CRC24_LENGTH)
+ return -EIO;
+
+ ghp->crc_length = len - CRC24_LENGTH;
+
+ ghp->ack_req = 0;
+
+ /* Section 5.5: FCS */
+ ghp->fcs = *(llc_hdr + len - 3);
+ ghp->fcs |= *(llc_hdr + len - 2) << 8;
+ ghp->fcs |= *(llc_hdr + len - 1) << 16;
+
+ /* Section 6.2.1: invalid PD field */
+ if (llc_hdr[0] & 0x80)
+ return -EIO;
+
+ /* This only works for the MS->SGSN direction */
+ if (llc_hdr[0] & 0x40)
+ ghp->is_cmd = 0;
+ else
+ ghp->is_cmd = 1;
+
+ ghp->sapi = llc_hdr[0] & 0xf;
+
+ /* Section 6.2.3: check for reserved SAPI */
+ switch (ghp->sapi) {
+ case 0:
+ case 4:
+ case 6:
+ case 0xa:
+ case 0xc:
+ case 0xd:
+ case 0xf:
+ return -EINVAL;
+ }
+
+ if ((ctrl[0] & 0x80) == 0) {
+ /* I (Information transfer + Supervisory) format */
+ uint8_t k;
+
+ ghp->data = ctrl + 3;
+
+ if (ctrl[0] & 0x40)
+ ghp->ack_req = 1;
+
+ ghp->seq_tx = (ctrl[0] & 0x1f) << 4;
+ ghp->seq_tx |= (ctrl[1] >> 4);
+
+ ghp->seq_rx = (ctrl[1] & 0x7) << 6;
+ ghp->seq_rx |= (ctrl[2] >> 2);
+
+ switch (ctrl[2] & 0x03) {
+ case 0:
+ ghp->cmd = GPRS_LLC_RR;
+ break;
+ case 1:
+ ghp->cmd = GPRS_LLC_ACK;
+ break;
+ case 2:
+ ghp->cmd = GPRS_LLC_RNR;
+ break;
+ case 3:
+ ghp->cmd = GPRS_LLC_SACK;
+ k = ctrl[3] & 0x1f;
+ ghp->data += 1 + k;
+ break;
+ }
+ ghp->data_len = (llc_hdr + len - 3) - ghp->data;
+ } else if ((ctrl[0] & 0xc0) == 0x80) {
+ /* S (Supervisory) format */
+ ghp->data = NULL;
+ ghp->data_len = 0;
+
+ if (ctrl[0] & 0x20)
+ ghp->ack_req = 1;
+ ghp->seq_rx = (ctrl[0] & 0x7) << 6;
+ ghp->seq_rx |= (ctrl[1] >> 2);
+
+ switch (ctrl[1] & 0x03) {
+ case 0:
+ ghp->cmd = GPRS_LLC_RR;
+ break;
+ case 1:
+ ghp->cmd = GPRS_LLC_ACK;
+ break;
+ case 2:
+ ghp->cmd = GPRS_LLC_RNR;
+ break;
+ case 3:
+ ghp->cmd = GPRS_LLC_SACK;
+ break;
+ }
+ } else if ((ctrl[0] & 0xe0) == 0xc0) {
+ /* UI (Unconfirmed Inforamtion) format */
+ ghp->cmd = GPRS_LLC_UI;
+ ghp->data = ctrl + 2;
+ ghp->data_len = (llc_hdr + len - 3) - ghp->data;
+
+ ghp->seq_tx = (ctrl[0] & 0x7) << 6;
+ ghp->seq_tx |= (ctrl[1] >> 2);
+ if (ctrl[1] & 0x02) {
+ ghp->is_encrypted = 1;
+ /* FIXME: encryption */
+ }
+ if (ctrl[1] & 0x01) {
+ /* FCS over hdr + all inf fields */
+ } else {
+ /* FCS over hdr + N202 octets (4) */
+ if (ghp->crc_length > UI_HDR_LEN + N202)
+ ghp->crc_length = UI_HDR_LEN + N202;
+ }
+ } else {
+ /* U (Unnumbered) format: 1 1 1 P/F M4 M3 M2 M1 */
+ ghp->data = NULL;
+ ghp->data_len = 0;
+
+ switch (ctrl[0] & 0xf) {
+ case GPRS_LLC_U_NULL_CMD:
+ ghp->cmd = GPRS_LLC_NULL;
+ break;
+ case GPRS_LLC_U_DM_RESP:
+ ghp->cmd = GPRS_LLC_DM;
+ break;
+ case GPRS_LLC_U_DISC_CMD:
+ ghp->cmd = GPRS_LLC_DISC;
+ break;
+ case GPRS_LLC_U_UA_RESP:
+ ghp->cmd = GPRS_LLC_UA;
+ break;
+ case GPRS_LLC_U_SABM_CMD:
+ ghp->cmd = GPRS_LLC_SABM;
+ break;
+ case GPRS_LLC_U_FRMR_RESP:
+ ghp->cmd = GPRS_LLC_FRMR;
+ break;
+ case GPRS_LLC_U_XID:
+ ghp->cmd = GPRS_LLC_XID;
+ ghp->data = ctrl + 1;
+ ghp->data_len = (llc_hdr + len - 3) - ghp->data;
+ break;
+ default:
+ return -EIO;
+ }
+ }
+
+ /* FIXME: parse sack frame */
+ if (ghp->cmd == GPRS_LLC_SACK) {
+ LOGP(DPCU, LOGL_NOTICE, "Unsupported SACK frame\n");
+ return -EIO;
+ }
+
+ return 0;
+}