gprs: Separate LLC parsing from LLC state handling
Currently LLC parsing is part of gprs_llc.c which needs large parts
of the SGSN code parsing to fulfill its link dependencies.
This patch moves the functions that just do plain parsing, dumping,
and FCS computation to a different file to avoid these dependencies
if LLC stateful processing is not needed. It also exposes
struct gprs_llc_hdr_parsed and enum gprs_llc_cmd publically.
Sponsored-by: On-Waves ehf
diff --git a/openbsc/src/gprs/gprs_llc_parse.c b/openbsc/src/gprs/gprs_llc_parse.c
new file mode 100644
index 0000000..b1f1a56
--- /dev/null
+++ b/openbsc/src/gprs/gprs_llc_parse.c
@@ -0,0 +1,243 @@
+/* GPRS LLC protocol implementation as per 3GPP TS 04.64 */
+
+/* (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 <errno.h>
+#include <stdint.h>
+
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/timer.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/gprs/gprs_bssgp.h>
+
+#include <openbsc/gsm_data.h>
+#include <openbsc/debug.h>
+#include <openbsc/gprs_sgsn.h>
+#include <openbsc/gprs_gmm.h>
+#include <openbsc/gprs_llc.h>
+#include <openbsc/crc24.h>
+
+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 }
+};
+
+#define LLC_ALLOC_SIZE 16384
+#define UI_HDR_LEN 3
+#define N202 4
+#define CRC24_LENGTH 3
+
+int gprs_llc_fcs(uint8_t *data, unsigned int len)
+{
+ uint32_t fcs_calc;
+
+ fcs_calc = crc24_calc(INIT_CRC24, data, len);
+ fcs_calc = ~fcs_calc;
+ fcs_calc &= 0xffffff;
+
+ return fcs_calc;
+}
+
+void gprs_llc_hdr_dump(struct gprs_llc_hdr_parsed *gph)
+{
+ DEBUGP(DLLC, "LLC SAPI=%u %c %c FCS=0x%06x",
+ gph->sapi, gph->is_cmd ? 'C' : 'R', gph->ack_req ? 'A' : ' ',
+ gph->fcs);
+
+ if (gph->cmd)
+ DEBUGPC(DLLC, "CMD=%s ", get_value_string(llc_cmd_strs, gph->cmd));
+
+ if (gph->data)
+ DEBUGPC(DLLC, "DATA ");
+
+ DEBUGPC(DLLC, "\n");
+}
+
+/* parse a GPRS LLC header, also check for invalid frames */
+int gprs_llc_hdr_parse(struct gprs_llc_hdr_parsed *ghp,
+ uint8_t *llc_hdr, int len)
+{
+ 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(DLLC, LOGL_NOTICE, "Unsupported SACK frame\n");
+ return -EIO;
+ }
+
+ return 0;
+}