244 lines
5.4 KiB
C
244 lines
5.4 KiB
C
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/* GPRS LLC protocol implementation as per 3GPP TS 04.64 */
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/* (C) 2009-2010 by Harald Welte <laforge@gnumonks.org>
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include <errno.h>
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#include <stdint.h>
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#include <osmocom/core/msgb.h>
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#include <osmocom/core/linuxlist.h>
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#include <osmocom/core/timer.h>
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#include <osmocom/core/talloc.h>
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#include <osmocom/gprs/gprs_bssgp.h>
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#include <openbsc/gsm_data.h>
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#include <openbsc/debug.h>
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#include <openbsc/gprs_sgsn.h>
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#include <openbsc/gprs_gmm.h>
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#include <openbsc/gprs_llc.h>
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#include <openbsc/crc24.h>
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static const struct value_string llc_cmd_strs[] = {
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{ GPRS_LLC_NULL, "NULL" },
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{ GPRS_LLC_RR, "RR" },
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{ GPRS_LLC_ACK, "ACK" },
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{ GPRS_LLC_RNR, "RNR" },
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{ GPRS_LLC_SACK, "SACK" },
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{ GPRS_LLC_DM, "DM" },
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{ GPRS_LLC_DISC, "DISC" },
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{ GPRS_LLC_UA, "UA" },
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{ GPRS_LLC_SABM, "SABM" },
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{ GPRS_LLC_FRMR, "FRMR" },
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{ GPRS_LLC_XID, "XID" },
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{ GPRS_LLC_UI, "UI" },
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{ 0, NULL }
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};
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#define LLC_ALLOC_SIZE 16384
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#define UI_HDR_LEN 3
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#define N202 4
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#define CRC24_LENGTH 3
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int gprs_llc_fcs(uint8_t *data, unsigned int len)
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{
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uint32_t fcs_calc;
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fcs_calc = crc24_calc(INIT_CRC24, data, len);
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fcs_calc = ~fcs_calc;
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fcs_calc &= 0xffffff;
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return fcs_calc;
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}
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void gprs_llc_hdr_dump(struct gprs_llc_hdr_parsed *gph)
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{
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DEBUGP(DLLC, "LLC SAPI=%u %c %c FCS=0x%06x",
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gph->sapi, gph->is_cmd ? 'C' : 'R', gph->ack_req ? 'A' : ' ',
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gph->fcs);
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if (gph->cmd)
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DEBUGPC(DLLC, "CMD=%s ", get_value_string(llc_cmd_strs, gph->cmd));
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if (gph->data)
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DEBUGPC(DLLC, "DATA ");
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DEBUGPC(DLLC, "\n");
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}
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/* parse a GPRS LLC header, also check for invalid frames */
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int gprs_llc_hdr_parse(struct gprs_llc_hdr_parsed *ghp,
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uint8_t *llc_hdr, int len)
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{
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uint8_t *ctrl = llc_hdr+1;
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if (len <= CRC24_LENGTH)
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return -EIO;
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ghp->crc_length = len - CRC24_LENGTH;
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ghp->ack_req = 0;
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/* Section 5.5: FCS */
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ghp->fcs = *(llc_hdr + len - 3);
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ghp->fcs |= *(llc_hdr + len - 2) << 8;
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ghp->fcs |= *(llc_hdr + len - 1) << 16;
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/* Section 6.2.1: invalid PD field */
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if (llc_hdr[0] & 0x80)
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return -EIO;
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/* This only works for the MS->SGSN direction */
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if (llc_hdr[0] & 0x40)
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ghp->is_cmd = 0;
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else
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ghp->is_cmd = 1;
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ghp->sapi = llc_hdr[0] & 0xf;
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/* Section 6.2.3: check for reserved SAPI */
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switch (ghp->sapi) {
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case 0:
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case 4:
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case 6:
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case 0xa:
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case 0xc:
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case 0xd:
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case 0xf:
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return -EINVAL;
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}
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if ((ctrl[0] & 0x80) == 0) {
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/* I (Information transfer + Supervisory) format */
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uint8_t k;
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ghp->data = ctrl + 3;
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if (ctrl[0] & 0x40)
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ghp->ack_req = 1;
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ghp->seq_tx = (ctrl[0] & 0x1f) << 4;
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ghp->seq_tx |= (ctrl[1] >> 4);
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ghp->seq_rx = (ctrl[1] & 0x7) << 6;
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ghp->seq_rx |= (ctrl[2] >> 2);
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switch (ctrl[2] & 0x03) {
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case 0:
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ghp->cmd = GPRS_LLC_RR;
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break;
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case 1:
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ghp->cmd = GPRS_LLC_ACK;
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break;
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case 2:
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ghp->cmd = GPRS_LLC_RNR;
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break;
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case 3:
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ghp->cmd = GPRS_LLC_SACK;
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k = ctrl[3] & 0x1f;
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ghp->data += 1 + k;
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break;
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}
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ghp->data_len = (llc_hdr + len - 3) - ghp->data;
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} else if ((ctrl[0] & 0xc0) == 0x80) {
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/* S (Supervisory) format */
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ghp->data = NULL;
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ghp->data_len = 0;
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if (ctrl[0] & 0x20)
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ghp->ack_req = 1;
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ghp->seq_rx = (ctrl[0] & 0x7) << 6;
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ghp->seq_rx |= (ctrl[1] >> 2);
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switch (ctrl[1] & 0x03) {
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case 0:
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ghp->cmd = GPRS_LLC_RR;
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break;
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case 1:
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ghp->cmd = GPRS_LLC_ACK;
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break;
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case 2:
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ghp->cmd = GPRS_LLC_RNR;
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break;
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case 3:
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ghp->cmd = GPRS_LLC_SACK;
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break;
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}
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} else if ((ctrl[0] & 0xe0) == 0xc0) {
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/* UI (Unconfirmed Inforamtion) format */
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ghp->cmd = GPRS_LLC_UI;
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ghp->data = ctrl + 2;
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ghp->data_len = (llc_hdr + len - 3) - ghp->data;
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ghp->seq_tx = (ctrl[0] & 0x7) << 6;
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ghp->seq_tx |= (ctrl[1] >> 2);
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if (ctrl[1] & 0x02) {
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ghp->is_encrypted = 1;
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/* FIXME: encryption */
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}
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if (ctrl[1] & 0x01) {
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/* FCS over hdr + all inf fields */
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} else {
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/* FCS over hdr + N202 octets (4) */
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if (ghp->crc_length > UI_HDR_LEN + N202)
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ghp->crc_length = UI_HDR_LEN + N202;
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}
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} else {
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/* U (Unnumbered) format: 1 1 1 P/F M4 M3 M2 M1 */
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ghp->data = NULL;
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ghp->data_len = 0;
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switch (ctrl[0] & 0xf) {
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case GPRS_LLC_U_NULL_CMD:
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ghp->cmd = GPRS_LLC_NULL;
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break;
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case GPRS_LLC_U_DM_RESP:
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ghp->cmd = GPRS_LLC_DM;
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break;
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case GPRS_LLC_U_DISC_CMD:
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ghp->cmd = GPRS_LLC_DISC;
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break;
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case GPRS_LLC_U_UA_RESP:
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ghp->cmd = GPRS_LLC_UA;
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break;
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case GPRS_LLC_U_SABM_CMD:
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ghp->cmd = GPRS_LLC_SABM;
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break;
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case GPRS_LLC_U_FRMR_RESP:
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ghp->cmd = GPRS_LLC_FRMR;
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break;
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case GPRS_LLC_U_XID:
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ghp->cmd = GPRS_LLC_XID;
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ghp->data = ctrl + 1;
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ghp->data_len = (llc_hdr + len - 3) - ghp->data;
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break;
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default:
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return -EIO;
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}
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}
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/* FIXME: parse sack frame */
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if (ghp->cmd == GPRS_LLC_SACK) {
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LOGP(DLLC, LOGL_NOTICE, "Unsupported SACK frame\n");
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return -EIO;
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}
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return 0;
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}
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