| /* GPRS LLC protocol implementation as per 3GPP TS 04.64 */ |
| |
| /* (C) 2009 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 <openbsc/gsm_data.h> |
| #include <osmocore/msgb.h> |
| #include <openbsc/debug.h> |
| #include <osmocore/linuxlist.h> |
| #include <osmocore/timer.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; |
| |
| u_int32_t tlli; |
| u_int32_t sapi; |
| |
| u_int8_t v_sent; |
| u_int8_t v_ack; |
| u_int8_t v_recv; |
| |
| unsigned int n200; |
| unsigned int retrans_ctr; |
| }; |
| |
| 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 { |
| u_int8_t sapi; |
| u_int8_t is_cmd:1, |
| ack_req:1, |
| is_encrypted:1; |
| u_int32_t seq_rx; |
| u_int32_t seq_tx; |
| u_int32_t fcs; |
| u_int32_t fcs_calc; |
| u_int8_t *data; |
| 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(u_int8_t *data, unsigned int len) |
| { |
| u_int32_t fcs_calc; |
| |
| fcs_calc = crc24_calc(INIT_CRC24, data, len); |
| fcs_calc = ~fcs_calc; |
| fcs_calc &= 0xffffff; |
| |
| return fcs_calc; |
| } |
| |
| /* transmit a simple U frame */ |
| static int gprs_llc_tx_u() |
| { |
| struct msgb *msg = msgb_alloc(LLC_ALLOC_SIZE, "GPRS/LLC"); |
| |
| if (!msg) |
| return -ENOMEM; |
| |
| |
| |
| /* transmit the frame via BSSGP->NS->... */ |
| } |
| |
| 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++; |
| } |
| } |
| |
| /* Transmit a UI frame over the given SAPI */ |
| int gprs_llc_tx_ui(struct msgb *msg, u_int8_t sapi, int command) |
| { |
| u_int8_t *fcs, *llch; |
| u_int8_t addr, ctrl[2]; |
| u_int32_t fcs_calc; |
| u_int16_t nu = 0; |
| |
| /* 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; |
| |
| 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 */ |
| 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 u_int8_t *llc_hdr, int len) |
| { |
| u_int8_t *ctrl = llc_hdr+1; |
| int is_sack = 0; |
| unsigned int crc_length; |
| u_int32_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 */ |
| u_int8_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; |
| } |
| } else if ((ctrl[0] & 0xc0) == 0x80) { |
| /* S (Supervisory) format */ |
| ghp->data = NULL; |
| |
| 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->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; |
| |
| switch (ctrl[0] & 0xf) { |
| case 0: |
| ghp->cmd = GPRS_LLC_NULL; |
| break; |
| case 0x1: |
| ghp->cmd = GPRS_LLC_DM; |
| break; |
| case 0x4: |
| ghp->cmd = GPRS_LLC_DISC; |
| break; |
| case 0x6: |
| ghp->cmd = GPRS_LLC_UA; |
| break; |
| case 0x7: |
| ghp->cmd = GPRS_LLC_SABM; |
| break; |
| case 0x8: |
| ghp->cmd = GPRS_LLC_FRMR; |
| break; |
| case 0xb: |
| ghp->cmd = GPRS_LLC_XID; |
| 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 */ |
| int gprs_llc_rcvmsg(struct msgb *msg, struct tlv_parsed *tv) |
| { |
| struct bssgp_ud_hdr *udh = (struct bssgp_ud_hdr *) msg->l3h; |
| struct gprs_llc_hdr *lh = msg->llch; |
| struct gprs_llc_hdr_parsed llhp; |
| struct gprs_llc_entity *lle; |
| int rc; |
| |
| rc = gprs_llc_hdr_parse(&llhp, lh, TLVP_LEN(tv, BSSGP_IE_LLC_PDU)); |
| |
| /* FIXME: find LLC Entity */ |
| |
| gprs_llc_hdr_dump(&llhp); |
| rc = gprs_llc_hdr_rx(&llhp, lle); |
| |
| if (llhp.data) { |
| msg->gmmh = llhp.data; |
| switch (llhp.sapi) { |
| case GPRS_SAPI_GMM: |
| rc = gsm0408_gprs_rcvmsg(msg); |
| } |
| } |
| |
| return 0; |
| } |