diff options
Diffstat (limited to 'openbsc/src/gprs_llc.c')
-rw-r--r-- | openbsc/src/gprs_llc.c | 420 |
1 files changed, 420 insertions, 0 deletions
diff --git a/openbsc/src/gprs_llc.c b/openbsc/src/gprs_llc.c new file mode 100644 index 000000000..2c927c6cf --- /dev/null +++ b/openbsc/src/gprs_llc.c @@ -0,0 +1,420 @@ +/* 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; +} |