diff options
Diffstat (limited to 'openbsc/src/gprs/gprs_llc_parse.c')
| -rw-r--r-- | openbsc/src/gprs/gprs_llc_parse.c | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/openbsc/src/gprs/gprs_llc_parse.c b/openbsc/src/gprs/gprs_llc_parse.c new file mode 100644 index 000000000..b1f1a56dd --- /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; +} |