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-rw-r--r--openbsc/src/gprs/gprs_llc.c549
1 files changed, 549 insertions, 0 deletions
diff --git a/openbsc/src/gprs/gprs_llc.c b/openbsc/src/gprs/gprs_llc.c
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index 000000000..9c75a3d4e
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+++ b/openbsc/src/gprs/gprs_llc.c
@@ -0,0 +1,549 @@
+/* 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 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.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <errno.h>
+#include <stdint.h>
+
+#include <osmocore/msgb.h>
+#include <osmocore/linuxlist.h>
+#include <osmocore/timer.h>
+#include <osmocore/talloc.h>
+
+#include <openbsc/gsm_data.h>
+#include <openbsc/debug.h>
+#include <openbsc/gprs_bssgp.h>
+#include <openbsc/gprs_llc.h>
+#include <openbsc/crc24.h>
+
+/* Section 4.5.2 Logical Link States + Annex C.2 */
+enum gprs_llc_ll_state {
+ GPRS_LLS_UNASSIGNED = 1, /* No TLLI yet */
+ GPRS_LLS_ASSIGNED_ADM = 2, /* TLLI assigned */
+ GPRS_LLS_LOCAL_EST = 3, /* Local Establishment */
+ GPRS_LLS_REMOTE_EST = 4, /* Remote Establishment */
+ GPRS_LLS_ABM = 5,
+ GPRS_LLS_LOCAL_REL = 6, /* Local Release */
+ GPRS_LLS_TIMER_REC = 7, /* Timer Recovery */
+};
+
+/* Section 4.7.1: Logical Link Entity: One per DLCI (TLLI + SAPI) */
+struct gprs_llc_lle {
+ struct llist_head list;
+ struct timer_list t200;
+ struct timer_list t201; /* wait for acknowledgement */
+
+ enum gprs_llc_ll_state state;
+
+ uint32_t tlli;
+ uint32_t sapi;
+
+ uint8_t v_sent;
+ uint8_t v_ack;
+ uint8_t v_recv;
+
+ unsigned int n200;
+ unsigned int retrans_ctr;
+
+ /* over which BSSGP BTS ctx do we need to transmit */
+ uint16_t bvci;
+ uint16_t nsei;
+};
+
+static LLIST_HEAD(gprs_llc_lles);
+void *llc_tall_ctx;
+
+/* lookup LLC Entity based on DLCI (TLLI+SAPI tuple) */
+static struct gprs_llc_lle *lle_by_tlli_sapi(uint32_t tlli, uint32_t sapi)
+{
+ struct gprs_llc_lle *lle;
+
+ llist_for_each_entry(lle, &gprs_llc_lles, list) {
+ if (lle->tlli == tlli && lle->sapi == sapi)
+ return lle;
+ }
+ return NULL;
+}
+
+static struct gprs_llc_lle *lle_alloc(uint32_t tlli, uint32_t sapi)
+{
+ struct gprs_llc_lle *lle;
+
+ lle = talloc_zero(llc_tall_ctx, struct gprs_llc_lle);
+ if (!lle)
+ return NULL;
+
+ lle->tlli = tlli;
+ lle->sapi = sapi;
+ lle->state = GPRS_LLS_UNASSIGNED;
+ llist_add(&lle->list, &gprs_llc_lles);
+
+ return lle;
+}
+
+enum gprs_llc_cmd {
+ GPRS_LLC_NULL,
+ GPRS_LLC_RR,
+ GPRS_LLC_ACK,
+ GPRS_LLC_RNR,
+ GPRS_LLC_SACK,
+ GPRS_LLC_DM,
+ GPRS_LLC_DISC,
+ GPRS_LLC_UA,
+ GPRS_LLC_SABM,
+ GPRS_LLC_FRMR,
+ GPRS_LLC_XID,
+};
+
+struct gprs_llc_hdr_parsed {
+ uint8_t sapi;
+ uint8_t is_cmd:1,
+ ack_req:1,
+ is_encrypted:1;
+ uint32_t seq_rx;
+ uint32_t seq_tx;
+ uint32_t fcs;
+ uint32_t fcs_calc;
+ uint8_t *data;
+ uint16_t data_len;
+ enum gprs_llc_cmd cmd;
+};
+
+#define LLC_ALLOC_SIZE 16384
+#define UI_HDR_LEN 3
+#define N202 4
+#define CRC24_LENGTH 3
+
+static 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;
+}
+
+static void t200_expired(void *data)
+{
+ struct gprs_llc_lle *lle = data;
+
+ /* 8.5.1.3: Expiry of T200 */
+
+ if (lle->retrans_ctr >= lle->n200) {
+ /* FIXME: LLGM-STATUS-IND, LL-RELEASE-IND/CNF */
+ lle->state = GPRS_LLS_ASSIGNED_ADM;
+ }
+
+ switch (lle->state) {
+ case GPRS_LLS_LOCAL_EST:
+ /* retransmit SABM */
+ /* re-start T200 */
+ lle->retrans_ctr++;
+ break;
+ case GPRS_LLS_LOCAL_REL:
+ /* retransmit DISC */
+ /* re-start T200 */
+ lle->retrans_ctr++;
+ break;
+ }
+
+}
+
+static void t201_expired(void *data)
+{
+ struct gprs_llc_lle *lle = data;
+
+ if (lle->retrans_ctr < lle->n200) {
+ /* transmit apropriate supervisory frame (8.6.4.1) */
+ /* set timer T201 */
+ lle->retrans_ctr++;
+ }
+}
+
+int gprs_llc_tx_u(struct msgb *msg, uint8_t sapi, int command,
+ enum gprs_llc_u_cmd u_cmd, int pf_bit)
+{
+ uint8_t *fcs, *llch;
+ uint8_t addr, ctrl;
+ uint32_t fcs_calc;
+
+ /* Identifiers from UP: (TLLI, SAPI) + (BVCI, NSEI) */
+
+ /* Address Field */
+ addr = sapi & 0xf;
+ if (command)
+ addr |= 0x40;
+
+ /* 6.3 Figure 8 */
+ ctrl = 0xe0 | u_cmd;
+ if (pf_bit)
+ ctrl |= 0x10;
+
+ /* prepend LLC UI header */
+ llch = msgb_push(msg, 2);
+ llch[0] = addr;
+ llch[1] = ctrl;
+
+ /* append FCS to end of frame */
+ fcs = msgb_put(msg, 3);
+ fcs_calc = gprs_llc_fcs(llch, fcs - llch);
+ fcs[0] = fcs_calc & 0xff;
+ fcs[1] = (fcs_calc >> 8) & 0xff;
+ fcs[2] = (fcs_calc >> 16) & 0xff;
+
+ /* Identifiers passed down: (BVCI, NSEI) */
+
+ return gprs_bssgp_tx_dl_ud(msg);
+}
+
+/* Send XID response to LLE */
+static int gprs_llc_tx_xid(struct gprs_llc_lle *lle, struct msgb *msg)
+{
+ /* copy identifiers from LLE to ensure lower layers can route */
+ msgb_tlli(msg) = lle->tlli;
+ msgb_bvci(msg) = lle->bvci;
+ msgb_nsei(msg) = lle->nsei;
+
+ return gprs_llc_tx_u(msg, lle->sapi, 0, GPRS_LLC_U_XID, 1);
+}
+
+/* Transmit a UI frame over the given SAPI */
+int gprs_llc_tx_ui(struct msgb *msg, uint8_t sapi, int command)
+{
+ struct gprs_llc_lle *lle;
+ uint8_t *fcs, *llch;
+ uint8_t addr, ctrl[2];
+ uint32_t fcs_calc;
+ uint16_t nu = 0;
+
+ /* Identifiers from UP: (TLLI, SAPI) + (BVCI, NSEI) */
+
+ /* look-up or create the LL Entity for this (TLLI, SAPI) tuple */
+ lle = lle_by_tlli_sapi(msgb_tlli(msg), sapi);
+ if (!lle)
+ lle = lle_alloc(msgb_tlli(msg), sapi);
+ /* Update LLE's (BVCI, NSEI) tuple */
+ lle->bvci = msgb_bvci(msg);
+ lle->nsei = msgb_nsei(msg);
+
+ /* Address Field */
+ addr = sapi & 0xf;
+ if (command)
+ addr |= 0x40;
+
+ /* Control Field */
+ ctrl[0] = 0xc0;
+ ctrl[0] |= nu >> 6;
+ ctrl[1] = (nu << 2) & 0xfc;
+ ctrl[1] |= 0x01; /* Protected Mode */
+
+ /* prepend LLC UI header */
+ llch = msgb_push(msg, 3);
+ llch[0] = addr;
+ llch[1] = ctrl[0];
+ llch[2] = ctrl[1];
+
+ /* append FCS to end of frame */
+ fcs = msgb_put(msg, 3);
+ fcs_calc = gprs_llc_fcs(llch, fcs - llch);
+ fcs[0] = fcs_calc & 0xff;
+ fcs[1] = (fcs_calc >> 8) & 0xff;
+ fcs[2] = (fcs_calc >> 16) & 0xff;
+
+ /* Identifiers passed down: (BVCI, NSEI) */
+
+ return gprs_bssgp_tx_dl_ud(msg);
+}
+
+static int gprs_llc_hdr_dump(struct gprs_llc_hdr_parsed *gph)
+{
+ DEBUGP(DGPRS, "LLC SAPI=%u %c %c FCS=0x%06x(%s) ",
+ gph->sapi, gph->is_cmd ? 'C' : 'R', gph->ack_req ? 'A' : ' ',
+ gph->fcs, gph->fcs_calc == gph->fcs ? "correct" : "WRONG");
+
+ if (gph->cmd)
+ DEBUGPC(DGPRS, "CMD=%u ", gph->cmd);
+
+ if (gph->data)
+ DEBUGPC(DGPRS, "DATA ");
+
+ DEBUGPC(DGPRS, "\n");
+}
+static int gprs_llc_hdr_rx(struct gprs_llc_hdr_parsed *gph,
+ struct gprs_llc_lle *lle)
+{
+ switch (gph->cmd) {
+ case GPRS_LLC_SABM: /* Section 6.4.1.1 */
+ lle->v_sent = lle->v_ack = lle->v_recv = 0;
+ if (lle->state == GPRS_LLS_ASSIGNED_ADM) {
+ /* start re-establishment (8.7.1) */
+ }
+ lle->state = GPRS_LLS_REMOTE_EST;
+ /* FIXME: Send UA */
+ lle->state = GPRS_LLS_ABM;
+ /* FIXME: process data */
+ break;
+ case GPRS_LLC_DISC: /* Section 6.4.1.2 */
+ /* FIXME: Send UA */
+ /* terminate ABM */
+ lle->state = GPRS_LLS_ASSIGNED_ADM;
+ break;
+ case GPRS_LLC_UA: /* Section 6.4.1.3 */
+ if (lle->state == GPRS_LLS_LOCAL_EST)
+ lle->state = GPRS_LLS_ABM;
+ break;
+ case GPRS_LLC_DM: /* Section 6.4.1.4: ABM cannot be performed */
+ if (lle->state == GPRS_LLS_LOCAL_EST)
+ lle->state = GPRS_LLS_ASSIGNED_ADM;
+ break;
+ case GPRS_LLC_FRMR: /* Section 6.4.1.5 */
+ break;
+ case GPRS_LLC_XID: /* Section 6.4.1.6 */
+ /* FIXME: implement XID negotiation using SNDCP */
+ {
+ struct msgb *resp;
+ uint8_t *xid;
+ resp = msgb_alloc_headroom(4096, 1024, "LLC_XID");
+ xid = msgb_put(resp, gph->data_len);
+ memcpy(xid, gph->data, gph->data_len);
+ gprs_llc_tx_xid(lle, resp);
+ }
+ break;
+ }
+
+ return 0;
+}
+
+/* parse a GPRS LLC header, also check for invalid frames */
+static int gprs_llc_hdr_parse(struct gprs_llc_hdr_parsed *ghp,
+ const uint8_t *llc_hdr, int len)
+{
+ uint8_t *ctrl = llc_hdr+1;
+ int is_sack = 0;
+ unsigned int crc_length;
+ uint32_t fcs_calc;
+
+ if (len <= CRC24_LENGTH)
+ return -EIO;
+
+ 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->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 (crc_length > UI_HDR_LEN + N202)
+ 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;
+ }
+ }
+
+ /* calculate what FCS we expect */
+ ghp->fcs_calc = gprs_llc_fcs(llc_hdr, crc_length);
+
+ /* FIXME: parse sack frame */
+}
+
+/* receive an incoming LLC PDU (BSSGP-UL-UNITDATA-IND, 7.2.4.2) */
+int gprs_llc_rcvmsg(struct msgb *msg, struct tlv_parsed *tv)
+{
+ struct bssgp_ud_hdr *udh = (struct bssgp_ud_hdr *) msgb_bssgph(msg);
+ struct gprs_llc_hdr *lh = msgb_llch(msg);
+ struct gprs_llc_hdr_parsed llhp;
+ struct gprs_llc_lle *lle;
+ int rc = 0;
+
+ /* Identifiers from DOWN: NSEI, BVCI, TLLI */
+
+ rc = gprs_llc_hdr_parse(&llhp, lh, TLVP_LEN(tv, BSSGP_IE_LLC_PDU));
+ /* FIXME */
+
+ gprs_llc_hdr_dump(&llhp);
+
+ /* find the LLC Entity for this TLLI+SAPI tuple */
+ lle = lle_by_tlli_sapi(msgb_tlli(msg), llhp.sapi);
+ /* allocate a new LLE if needed */
+ if (!lle)
+ lle = lle_alloc(msgb_tlli(msg), llhp.sapi);
+
+ /* Update LLE's (BVCI, NSEI) tuple */
+ lle->bvci = msgb_bvci(msg);
+ lle->nsei = msgb_nsei(msg);
+
+ rc = gprs_llc_hdr_rx(&llhp, lle);
+ /* FIXME */
+
+ if (llhp.data) {
+ msgb_gmmh(msg) = llhp.data;
+ switch (llhp.sapi) {
+ case GPRS_SAPI_GMM:
+ rc = gsm0408_gprs_rcvmsg(msg);
+ break;
+ case GPRS_SAPI_TOM2:
+ case GPRS_SAPI_TOM8:
+ /* FIXME */
+ case GPRS_SAPI_SNDCP3:
+ case GPRS_SAPI_SNDCP5:
+ case GPRS_SAPI_SNDCP9:
+ case GPRS_SAPI_SNDCP11:
+ /* FIXME */
+ case GPRS_SAPI_SMS:
+ /* FIXME */
+ default:
+ LOGP(DGPRS, LOGL_NOTICE, "Unsupported SAPI %u\n", llhp.sapi);
+ rc = -EINVAL;
+ break;
+ }
+ }
+
+ return rc;
+}
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-28 02:45:20 +0000