| /* 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; |
| } |