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Diffstat (limited to 'src/isdn/lapd_core.c')
| -rw-r--r-- | src/isdn/lapd_core.c | 2351 |
1 files changed, 2351 insertions, 0 deletions
diff --git a/src/isdn/lapd_core.c b/src/isdn/lapd_core.c new file mode 100644 index 00000000..b32ed263 --- /dev/null +++ b/src/isdn/lapd_core.c @@ -0,0 +1,2351 @@ +/*! \file lapd_core.c + * LAPD core implementation */ +/* + * (C) 2010-2020 by Harald Welte <laforge@gnumonks.org> + * (C) 2010-2011 by Andreas Eversberg <jolly@eversberg.eu> + * + * All Rights Reserved + * + * SPDX-License-Identifier: GPL-2.0+ + * + * 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. + * + */ + +/*! \addtogroup lapd + * @{ + * + * Osmocom LAPD core, used for Q.921, LAPDm and others. + * + * Notes on Buffering: rcv_buffer, tx_queue, tx_hist, send_buffer, send_queue + * + * RX data is stored in the rcv_buffer (pointer). If the message is complete, it + * is removed from rcv_buffer pointer and forwarded to L3. If the RX data is + * received while there is an incomplete rcv_buffer, it is appended to it. + * + * TX data is stored in the send_queue first. When transmitting a frame, + * the first message in the send_queue is moved to the send_buffer. There it + * resides until all fragments are acknowledged. Fragments to be sent by I + * frames are stored in the tx_hist buffer for resend, if required. Also the + * current fragment is copied into the tx_queue. There it resides until it is + * forwarded to layer 1. + * + * In case we have SAPI 0, we only have a window size of 1, so the unack- + * nowledged message resides always in the send_buffer. In case of a suspend, + * it can be written back to the first position of the send_queue. + * + * The layer 1 normally sends a PH-READY-TO-SEND. But because we use + * asynchronous transfer between layer 1 and layer 2 (serial link), we must + * send a frame before layer 1 reaches the right timeslot to send it. So we + * move the tx_queue to layer 1 when there is not already a pending frame, and + * wait until acknowledge after the frame has been sent. If we receive an + * acknowledge, we can send the next frame from the buffer, if any. + * + * The moving of tx_queue to layer 1 may also trigger T200, if desired. Also it + * will trigger next I frame, if possible. + * + * T203 is optional. It will be stated when entering MF EST state. It will also + * be started when I or S frame is received in that state . It will be + * restarted in the lapd_acknowledge() function, in case outstanding frames + * will not trigger T200. It will be stoped, when T200 is started in MF EST + * state. It will also be stoped when leaving MF EST state. + * + * \file lapd_core.c + */ + +/* Enable this to test content resolution on network side: + * - The first SABM is received, UA is dropped. + * - The phone repeats SABM, but it's content is wrong, so it is ignored + * - The phone repeats SABM again, content is right, so UA is sent. + */ +//#define TEST_CONTENT_RESOLUTION_NETWORK + +#include <stdio.h> +#include <stdbool.h> +#include <stdint.h> +#include <string.h> +#include <errno.h> + +#include <osmocom/core/logging.h> +#include <osmocom/core/timer.h> +#include <osmocom/core/msgb.h> +#include <osmocom/core/utils.h> +#include <osmocom/core/talloc.h> +#include <osmocom/isdn/lapd_core.h> +#include <osmocom/gsm/rsl.h> + +/* TS 04.06 Table 4 / Section 3.8.1 */ +#define LAPD_U_SABM 0x7 +#define LAPD_U_SABME 0xf +#define LAPD_U_DM 0x3 +#define LAPD_U_UI 0x0 +#define LAPD_U_DISC 0x8 +#define LAPD_U_UA 0xC +#define LAPD_U_FRMR 0x11 + +#define LAPD_S_RR 0x0 +#define LAPD_S_RNR 0x1 +#define LAPD_S_REJ 0x2 + +#define CR_USER2NET_CMD 0 +#define CR_USER2NET_RESP 1 +#define CR_NET2USER_CMD 1 +#define CR_NET2USER_RESP 0 + +#define LAPD_HEADROOM 56 +#define LAPD_TAILROOM 16 + +#define SBIT(a) (1 << a) +#define ALL_STATES 0xffffffff + +static void lapd_t200_cb(void *data); +static void lapd_t203_cb(void *data); +static int lapd_send_i(struct lapd_datalink *dl, int line, bool rts); +static int lapd_est_req(struct osmo_dlsap_prim *dp, struct lapd_msg_ctx *lctx); + +/* UTILITY FUNCTIONS */ + +struct msgb *lapd_msgb_alloc(int length, const char *name) +{ + /* adding space for padding, FIXME: add as an option */ + if (length < 21) + length = 21; + return msgb_alloc_headroom(length + LAPD_HEADROOM + LAPD_TAILROOM, LAPD_HEADROOM, name); +} + +static inline uint8_t do_mod(uint8_t x, uint8_t m) +{ + return x & (m - 1); +} + +static inline uint8_t inc_mod(uint8_t x, uint8_t m) +{ + return (x + 1) & (m - 1); +} + +static inline uint8_t add_mod(uint8_t x, uint8_t y, uint8_t m) +{ + return (x + y) & (m - 1); +} + +static inline uint8_t sub_mod(uint8_t x, uint8_t y, uint8_t m) +{ + return (x - y) & (m - 1); /* handle negative results correctly */ +} + +static void lapd_dl_flush_send(struct lapd_datalink *dl) +{ + struct msgb *msg; + + /* Flush send-queue */ + while ((msg = msgb_dequeue(&dl->send_queue))) + msgb_free(msg); + + /* Clear send-buffer */ + msgb_free(dl->send_buffer); + dl->send_buffer = NULL; +} + +static void lapd_dl_flush_hist(struct lapd_datalink *dl) +{ + unsigned int i; + + if (!dl->range_hist || !dl->tx_hist) + return; + + for (i = 0; i < dl->range_hist; i++) { + if (dl->tx_hist[i].msg) { + msgb_free(dl->tx_hist[i].msg); + dl->tx_hist[i].msg = NULL; + } + } +} + +static void lapd_dl_flush_tx_queue(struct lapd_datalink *dl) +{ + struct msgb *msg; + + while ((msg = msgb_dequeue(&dl->tx_queue))) + msgb_free(msg); +} + +static void lapd_dl_flush_tx(struct lapd_datalink *dl) +{ + lapd_dl_flush_tx_queue(dl); + lapd_dl_flush_hist(dl); +} + +/* Figure B.2/Q.921 */ +const struct value_string lapd_state_names[] = { + OSMO_VALUE_STRING(LAPD_STATE_NULL), + OSMO_VALUE_STRING(LAPD_STATE_TEI_UNASS), + OSMO_VALUE_STRING(LAPD_STATE_ASS_TEI_WAIT), + OSMO_VALUE_STRING(LAPD_STATE_EST_TEI_WAIT), + OSMO_VALUE_STRING(LAPD_STATE_IDLE), + OSMO_VALUE_STRING(LAPD_STATE_SABM_SENT), + OSMO_VALUE_STRING(LAPD_STATE_DISC_SENT), + OSMO_VALUE_STRING(LAPD_STATE_MF_EST), + OSMO_VALUE_STRING(LAPD_STATE_TIMER_RECOV), + { 0, NULL } +}; + +static inline const char *lapd_state_name(enum lapd_state state) +{ + return get_value_string(lapd_state_names, state); +} + +static void lapd_start_t200(struct lapd_datalink *dl) +{ + if ((dl->lapd_flags & LAPD_F_RTS)) { + if (dl->t200_rts != LAPD_T200_RTS_OFF) + return; + LOGDL(dl, LOGL_INFO, "Start T200. (pending until triggered by RTS)\n"); + dl->t200_rts = LAPD_T200_RTS_PENDING; + } else { + if (osmo_timer_pending(&dl->t200)) + return; + LOGDL(dl, LOGL_INFO, "Start T200 (timeout=%d.%06ds).\n", dl->t200_sec, dl->t200_usec); + osmo_timer_schedule(&dl->t200, dl->t200_sec, dl->t200_usec); + } +} + +/*! Handle timeout condition of T200 in RTS mode. + * The caller (LAPDm code) implements the T200 timer and must detect timeout condition. + * The function gets called by LAPDm code when it detects a timeout of T200. + * \param[in] dl caller-allocated datalink structure */ +int lapd_t200_timeout(struct lapd_datalink *dl) +{ + OSMO_ASSERT((dl->lapd_flags & LAPD_F_RTS)); + + if (dl->t200_rts != LAPD_T200_RTS_RUNNING) + return -EINVAL; + + dl->t200_rts = LAPD_T200_RTS_OFF; + + lapd_t200_cb(dl); + + return 0; +} + +static void lapd_start_t203(struct lapd_datalink *dl) +{ + if (osmo_timer_pending(&dl->t203)) + return; + LOGDL(dl, LOGL_INFO, "start T203\n"); + osmo_timer_schedule(&dl->t203, dl->t203_sec, dl->t203_usec); +} + +static void lapd_stop_t200(struct lapd_datalink *dl) +{ + if ((dl->lapd_flags & LAPD_F_RTS)) { + if (dl->t200_rts == LAPD_T200_RTS_OFF) + return; + dl->t200_rts = LAPD_T200_RTS_OFF; + } else { + if (!osmo_timer_pending(&dl->t200)) + return; + osmo_timer_del(&dl->t200); + } + LOGDL(dl, LOGL_INFO, "stop T200\n"); +} + +static bool lapd_is_t200_started(struct lapd_datalink *dl) +{ + if ((dl->lapd_flags & LAPD_F_RTS)) + return (dl->t200_rts != LAPD_T200_RTS_OFF); + else + return osmo_timer_pending(&dl->t200); +} + +static void lapd_stop_t203(struct lapd_datalink *dl) +{ + if (!osmo_timer_pending(&dl->t203)) + return; + LOGDL(dl, LOGL_INFO, "stop T203\n"); + osmo_timer_del(&dl->t203); +} + +static void lapd_dl_newstate(struct lapd_datalink *dl, uint32_t state) +{ + LOGDL(dl, LOGL_INFO, "new state %s -> %s\n", + lapd_state_name(dl->state), lapd_state_name(state)); + + if (state != LAPD_STATE_MF_EST && dl->state == LAPD_STATE_MF_EST) { + /* stop T203 on leaving MF EST state, if running */ + lapd_stop_t203(dl); + /* remove content res. (network side) on leaving MF EST state */ + msgb_free(dl->cont_res); + dl->cont_res = NULL; + } + + /* start T203 on entering MF EST state, if enabled */ + if ((dl->t203_sec || dl->t203_usec) + && state == LAPD_STATE_MF_EST && dl->state != LAPD_STATE_MF_EST) + lapd_start_t203(dl); + + dl->state = state; +} + +void *tall_lapd_ctx = NULL; + +/*! Initialize LAPD datalink instance and allocate history + * \param[in] dl caller-allocated datalink structure + * \param[in] k maximum number of unacknowledged frames + * \param[in] v_range range of sequence numbers + * \param[in] maxf maximum frame size (after defragmentation) + * \param[in] name human-readable name for this LAPD datalink */ +void lapd_dl_init2(struct lapd_datalink *dl, uint8_t k, uint8_t v_range, int maxf, + const char *name) +{ + int m; + + memset(dl, 0, sizeof(*dl)); + INIT_LLIST_HEAD(&dl->send_queue); + INIT_LLIST_HEAD(&dl->tx_queue); + dl->reestablish = 1; + dl->n200_est_rel = 3; + dl->n200 = 3; + dl->t200_sec = 1; + dl->t200_usec = 0; + osmo_timer_setup(&dl->t200, lapd_t200_cb, dl); + dl->t203_sec = 10; + dl->t203_usec = 0; + osmo_timer_setup(&dl->t203, lapd_t203_cb, dl); + dl->maxf = maxf; + if (k > v_range - 1) + k = v_range - 1; + dl->k = k; + dl->v_range = v_range; + + /* Calculate modulo for history array: + * - The history range must be at least k+1. + * - The history range must be 2^x, where x is as low as possible. + */ + k++; + for (m = 0x80; m; m >>= 1) { + if ((m & k)) { + if (k > m) + m <<= 1; + dl->range_hist = m; + break; + } + } + + if (!tall_lapd_ctx) { + tall_lapd_ctx = talloc_named_const(NULL, 1, "lapd context"); + OSMO_ASSERT(tall_lapd_ctx); + } + + talloc_free(dl->name); + if (name) + dl->name = talloc_strdup(tall_lapd_ctx, name); + else + dl->name = talloc_asprintf(tall_lapd_ctx, "dl=%p", dl); + + LOGDL(dl, LOGL_INFO, "Init DL layer: sequence range = %d, k = %d, " + "history range = %d\n", dl->v_range, dl->k, dl->range_hist); + + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + + dl->tx_hist = talloc_zero_array(tall_lapd_ctx, + struct lapd_history, dl->range_hist); +} + +/*! Initialize LAPD datalink instance and allocate history + * \param[in] dl caller-allocated datalink structure + * \param[in] k maximum number of unacknowledged frames + * \param[in] v_range range of sequence numbers + * \param[in] maxf maximum frame size (after defragmentation) */ +void lapd_dl_init(struct lapd_datalink *dl, uint8_t k, uint8_t v_range, int maxf) +{ + lapd_dl_init2(dl, k, v_range, maxf, NULL); +} + +void lapd_dl_set_name(struct lapd_datalink *dl, const char *name) +{ + if (!name) + return; + osmo_talloc_replace_string(tall_lapd_ctx, &dl->name, name); +} + +/* reset to IDLE state */ +void lapd_dl_reset(struct lapd_datalink *dl) +{ + LOGDL(dl, LOGL_INFO, "Resetting LAPD instance\n"); + /* enter idle state (and remove eventual cont_res) */ + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + /* flush buffer */ + lapd_dl_flush_tx(dl); + lapd_dl_flush_send(dl); + /* Discard partly received L3 message */ + msgb_free(dl->rcv_buffer); + dl->rcv_buffer = NULL; + /* stop Timers */ + lapd_stop_t200(dl); + lapd_stop_t203(dl); + if (dl->state == LAPD_STATE_IDLE) + return; + /* enter idle state (and remove eventual cont_res) */ + lapd_dl_newstate(dl, LAPD_STATE_IDLE); +} + +/*! Set lapd_flags to change behaviour + * \param[in] dl \ref lapd_datalink instance + * \param[in] flags \ref lapd_flags */ +int lapd_dl_set_flags(struct lapd_datalink *dl, unsigned int flags) +{ + if (lapd_is_t200_started(dl) && (flags & LAPD_F_RTS) != (dl->lapd_flags & LAPD_F_RTS)) { + LOGDL(dl, LOGL_ERROR, "Changing RTS flag not allowed while T200 is running.\n"); + return -EINVAL; + } + + dl->lapd_flags = flags; + + return 0; +} + +/* reset and de-allocate history buffer */ +void lapd_dl_exit(struct lapd_datalink *dl) +{ + /* free all ressources except history buffer */ + lapd_dl_reset(dl); + + /* enter null state */ + lapd_dl_newstate(dl, LAPD_STATE_NULL); + + /* free history buffer list */ + talloc_free(dl->tx_hist); + dl->tx_hist = NULL; + talloc_free(dl->name); + dl->name = NULL; +} + +/*! Set the \ref lapdm_mode of a LAPDm entity */ +int lapd_set_mode(struct lapd_datalink *dl, enum lapd_mode mode) +{ + switch (mode) { + case LAPD_MODE_USER: + dl->cr.loc2rem.cmd = CR_USER2NET_CMD; + dl->cr.loc2rem.resp = CR_USER2NET_RESP; + dl->cr.rem2loc.cmd = CR_NET2USER_CMD; + dl->cr.rem2loc.resp = CR_NET2USER_RESP; + break; + case LAPD_MODE_NETWORK: + dl->cr.loc2rem.cmd = CR_NET2USER_CMD; + dl->cr.loc2rem.resp = CR_NET2USER_RESP; + dl->cr.rem2loc.cmd = CR_USER2NET_CMD; + dl->cr.rem2loc.resp = CR_USER2NET_RESP; + break; + default: + return -EINVAL; + } + dl->mode = mode; + + return 0; +} + +/* send DL message with optional msgb */ +static int send_dl_l3(uint8_t prim, uint8_t op, struct lapd_msg_ctx *lctx, + struct msgb *msg) +{ + struct lapd_datalink *dl = lctx->dl; + struct osmo_dlsap_prim dp; + + osmo_prim_init(&dp.oph, 0, prim, op, msg); + return dl->send_dlsap(&dp, lctx); +} + +/* send simple DL message */ +static inline int send_dl_simple(uint8_t prim, uint8_t op, + struct lapd_msg_ctx *lctx) +{ + return send_dl_l3(prim, op, lctx, NULL); +} + +/* send MDL-ERROR INDICATION */ +static int mdl_error(uint8_t cause, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + struct osmo_dlsap_prim dp; + + LOGDL(dl, LOGL_NOTICE, + "sending MDL-ERROR-IND cause %d from state %s\n", + cause, lapd_state_name(dl->state)); + osmo_prim_init(&dp.oph, 0, PRIM_MDL_ERROR, PRIM_OP_INDICATION, NULL); + dp.u.error_ind.cause = cause; + return dl->send_dlsap(&dp, lctx); +} + +/* send UA response */ +static int lapd_send_ua(struct lapd_msg_ctx *lctx, uint8_t len, uint8_t *data) +{ + struct msgb *msg = lapd_msgb_alloc(len, "LAPD UA"); + struct lapd_msg_ctx nctx; + struct lapd_datalink *dl = lctx->dl; + + memcpy(&nctx, lctx, sizeof(nctx)); + msg->l3h = msgb_put(msg, len); + if (len) + memcpy(msg->l3h, data, len); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.resp; + nctx.format = LAPD_FORM_U; + nctx.s_u = LAPD_U_UA; + /* keep nctx.p_f */ + nctx.length = len; + nctx.more = 0; + + return dl->send_ph_data_req(&nctx, msg); +} + +/* send DM response */ +static int lapd_send_dm(struct lapd_msg_ctx *lctx) +{ + struct msgb *msg = lapd_msgb_alloc(0, "LAPD DM"); + struct lapd_msg_ctx nctx; + struct lapd_datalink *dl = lctx->dl; + + memcpy(&nctx, lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.resp; + nctx.format = LAPD_FORM_U; + nctx.s_u = LAPD_U_DM; + /* keep nctx.p_f */ + nctx.length = 0; + nctx.more = 0; + + return dl->send_ph_data_req(&nctx, msg); +} + +/* send RR response / command */ +static int lapd_send_rr(struct lapd_msg_ctx *lctx, uint8_t f_bit, uint8_t cmd) +{ + struct msgb *msg = lapd_msgb_alloc(0, "LAPD RR"); + struct lapd_msg_ctx nctx; + struct lapd_datalink *dl = lctx->dl; + + memcpy(&nctx, lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = (cmd) ? dl->cr.loc2rem.cmd : dl->cr.loc2rem.resp; + nctx.format = LAPD_FORM_S; + nctx.s_u = LAPD_S_RR; + nctx.p_f = f_bit; + nctx.n_recv = dl->v_recv; + nctx.length = 0; + nctx.more = 0; + + return dl->send_ph_data_req(&nctx, msg); +} + +/* send RNR response / command */ +static int lapd_send_rnr(struct lapd_msg_ctx *lctx, uint8_t f_bit, uint8_t cmd) +{ + struct msgb *msg = lapd_msgb_alloc(0, "LAPD RNR"); + struct lapd_msg_ctx nctx; + struct lapd_datalink *dl = lctx->dl; + + memcpy(&nctx, lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = (cmd) ? dl->cr.loc2rem.cmd : dl->cr.loc2rem.resp; + nctx.format = LAPD_FORM_S; + nctx.s_u = LAPD_S_RNR; + nctx.p_f = f_bit; + nctx.n_recv = dl->v_recv; + nctx.length = 0; + nctx.more = 0; + + return dl->send_ph_data_req(&nctx, msg); +} + +/* send REJ response */ +static int lapd_send_rej(struct lapd_msg_ctx *lctx, uint8_t f_bit) +{ + struct msgb *msg = lapd_msgb_alloc(0, "LAPD REJ"); + struct lapd_msg_ctx nctx; + struct lapd_datalink *dl = lctx->dl; + + memcpy(&nctx, lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.resp; + nctx.format = LAPD_FORM_S; + nctx.s_u = LAPD_S_REJ; + nctx.p_f = f_bit; + nctx.n_recv = dl->v_recv; + nctx.length = 0; + nctx.more = 0; + + return dl->send_ph_data_req(&nctx, msg); +} + +/* resend SABM or DISC message */ +static int lapd_send_resend(struct lapd_datalink *dl) +{ + struct msgb *msg; + uint8_t h = do_mod(dl->v_send, dl->range_hist); + int length = dl->tx_hist[h].msg->len; + struct lapd_msg_ctx nctx; + + /* assemble message */ + memcpy(&nctx, &dl->lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.cmd; + nctx.format = LAPD_FORM_U; + if (dl->state == LAPD_STATE_SABM_SENT) + nctx.s_u = (dl->use_sabme) ? LAPD_U_SABME : LAPD_U_SABM; + else + nctx.s_u = LAPD_U_DISC; + nctx.p_f = 1; + nctx.length = length; + nctx.more = 0; + + /* Resend SABM/DISC from tx_hist */ + msg = lapd_msgb_alloc(length, "LAPD resend"); + msg->l3h = msgb_put(msg, length); + if (length) + memcpy(msg->l3h, dl->tx_hist[h].msg->data, length); + + return dl->send_ph_data_req(&nctx, msg); +} + +/* reestablish link */ +static int lapd_reestablish(struct lapd_datalink *dl) +{ + struct osmo_dlsap_prim dp; + struct msgb *msg; + + LOGDL(dl, LOGL_DEBUG, "LAPD reestablish\n"); + + msg = lapd_msgb_alloc(0, "DUMMY"); + osmo_prim_init(&dp.oph, 0, PRIM_DL_EST, PRIM_OP_REQUEST, msg); + + return lapd_est_req(&dp, &dl->lctx); +} + +/* Timer callback on T200 expiry */ +static void lapd_t200_cb(void *data) +{ + struct lapd_datalink *dl = data; + + LOGDL(dl, LOGL_INFO, "Timeout T200 state=%s\n", lapd_state_name(dl->state)); + + switch (dl->state) { + case LAPD_STATE_SABM_SENT: + /* 5.4.1.3 */ + /* increment re-transmission counter */ + dl->retrans_ctr++; + if (dl->retrans_ctr >= dl->n200_est_rel + 1) { + /* flush tx and send buffers */ + lapd_dl_flush_tx(dl); + lapd_dl_flush_send(dl); + /* go back to idle state */ + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + /* NOTE: we must not change any other states or buffers + * and queues, since we may reconnect after handover + * failure. the buffered messages is replaced there */ + /* send MDL ERROR INIDCATION to L3 */ + mdl_error(MDL_CAUSE_T200_EXPIRED, &dl->lctx); + /* send RELEASE INDICATION to L3 */ + send_dl_simple(PRIM_DL_REL, PRIM_OP_INDICATION, + &dl->lctx); + break; + } + /* retransmit SABM command */ + lapd_send_resend(dl); + /* restart T200 (PH-READY-TO-SEND) */ + lapd_start_t200(dl); + break; + case LAPD_STATE_DISC_SENT: + /* 5.4.4.3 */ + /* increment re-transmission counter */ + dl->retrans_ctr++; + if (dl->retrans_ctr >= dl->n200_est_rel + 1) { + /* send MDL ERROR INIDCATION to L3 */ + mdl_error(MDL_CAUSE_T200_EXPIRED, &dl->lctx); + /* flush tx and send buffers */ + lapd_dl_flush_tx(dl); + lapd_dl_flush_send(dl); + /* go back to idle state */ + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + /* NOTE: we must not change any other states or buffers + * and queues, since we may reconnect after handover + * failure. the buffered messages is replaced there */ + /* send RELEASE INDICATION to L3 */ + send_dl_simple(PRIM_DL_REL, PRIM_OP_CONFIRM, &dl->lctx); + break; + } + /* retransmit DISC command */ + lapd_send_resend(dl); + /* restart T200 (PH-READY-TO-SEND) */ + lapd_start_t200(dl); + break; + case LAPD_STATE_MF_EST: + /* 5.5.7 */ + dl->retrans_ctr = 0; + lapd_dl_newstate(dl, LAPD_STATE_TIMER_RECOV); + /* fall through */ + case LAPD_STATE_TIMER_RECOV: + dl->retrans_ctr++; + if (dl->retrans_ctr <= dl->n200) { + uint8_t vs = sub_mod(dl->v_send, 1, dl->v_range); + uint8_t h = do_mod(vs, dl->range_hist); + /* retransmit I frame (V_s-1) with P=1, if any */ + if (dl->tx_hist[h].msg) { + struct msgb *msg; + int length = dl->tx_hist[h].msg->len; + struct lapd_msg_ctx nctx; + + LOGDL(dl, LOGL_INFO, "retransmit last frame V(S)=%d\n", vs); + /* Create I frame (segment) from tx_hist */ + memcpy(&nctx, &dl->lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.cmd; + nctx.format = LAPD_FORM_I; + nctx.p_f = 1; + nctx.n_send = vs; + nctx.n_recv = dl->v_recv; + nctx.length = length; + nctx.more = dl->tx_hist[h].more; + msg = lapd_msgb_alloc(length, "LAPD I resend"); + msg->l3h = msgb_put(msg, length); + memcpy(msg->l3h, dl->tx_hist[h].msg->data, + length); + dl->send_ph_data_req(&nctx, msg); + } else { + /* OR send appropriate supervision frame with P=1 */ + if (!dl->own_busy && !dl->seq_err_cond) { + lapd_send_rr(&dl->lctx, 1, 1); + /* NOTE: In case of sequence error + * condition, the REJ frame has been + * transmitted when entering the + * condition, so it has not be done + * here + */ + } else if (dl->own_busy) { + lapd_send_rnr(&dl->lctx, 1, 1); + } else { + LOGDL(dl, LOGL_INFO, "unhandled, pls. fix\n"); + } + } + /* restart T200 (PH-READY-TO-SEND) */ + lapd_start_t200(dl); + } else { + /* send MDL ERROR INIDCATION to L3 */ + mdl_error(MDL_CAUSE_T200_EXPIRED, &dl->lctx); + /* reestablish */ + if (!dl->reestablish) + break; + LOGDL(dl, LOGL_NOTICE, "N200+1 reached, performingreestablishment\n"); + lapd_reestablish(dl); + } + break; + default: + LOGDL(dl, LOGL_INFO, "T200 expired in unexpected dl->state %s)\n", + lapd_state_name(dl->state)); + } +} + +/* Timer callback on T203 expiry */ +static void lapd_t203_cb(void *data) +{ + struct lapd_datalink *dl = data; + + LOGDL(dl, LOGL_INFO, "Timeout T203 state=%s\n", lapd_state_name(dl->state)); + + if (dl->state != LAPD_STATE_MF_EST) { + LOGDL(dl, LOGL_ERROR, "T203 fired outside MF EST state, please fix!\n"); + return; + } + + /* set retransmission counter to 0 */ + dl->retrans_ctr = 0; + /* enter timer recovery state */ + lapd_dl_newstate(dl, LAPD_STATE_TIMER_RECOV); + /* transmit a supervisory command with P bit set to 1 as follows: */ + if (!dl->own_busy) { + LOGDL(dl, LOGL_INFO, "transmit an RR poll command\n"); + /* Send RR with P=1 */ + lapd_send_rr(&dl->lctx, 1, 1); + } else { + LOGDL(dl, LOGL_INFO, "transmit an RNR poll command\n"); + /* Send RNR with P=1 */ + lapd_send_rnr(&dl->lctx, 1, 1); + } + /* start T200 */ + lapd_start_t200(dl); +} + +/* 5.5.3.1: Common function to acknowlege frames up to the given N(R) value + * In case of a sequence error, the cause is returned with negative sign. */ +static int lapd_acknowledge(struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + uint8_t nr = lctx->n_recv; + int s = 0, rej = 0; + bool t200_reset = false; + int i, h; + + /* supervisory frame ? */ + if (lctx->format == LAPD_FORM_S) + s = 1; + /* REJ frame ? */ + if (s && lctx->s_u == LAPD_S_REJ) + rej = 1; + + /* Flush all transmit buffers of acknowledged frames */ + for (i = dl->v_ack; i != nr; i = inc_mod(i, dl->v_range)) { + h = do_mod(i, dl->range_hist); + if (dl->tx_hist[h].msg) { + msgb_free(dl->tx_hist[h].msg); + dl->tx_hist[h].msg = NULL; + LOGDL(dl, LOGL_INFO, "ack frame %d\n", i); + } + } + + if (dl->state != LAPD_STATE_TIMER_RECOV) { + /* When not in the timer recovery condition, the data + * link layer entity shall reset the timer T200 on + * receipt of a valid I frame with N(R) higher than V(A), + * or an REJ with an N(R) equal to V(A). */ + if ((!rej && nr != dl->v_ack) || (rej && nr == dl->v_ack)) { + t200_reset = true; + lapd_stop_t200(dl); + /* 5.5.3.1 Note 1 + 2 imply timer recovery cond. */ + } + /* 5.7.4: N(R) sequence error + * N(R) is called valid, if and only if + * (N(R)-V(A)) mod 8 <= (V(S)-V(A)) mod 8. + */ + if (sub_mod(nr, dl->v_ack, dl->v_range) > sub_mod(dl->v_send, dl->v_ack, dl->v_range)) { + LOGDL(dl, LOGL_NOTICE, "N(R) sequence error\n"); + return -MDL_CAUSE_SEQ_ERR; + } + } + + /* V(A) shall be set to the value of N(R) */ + dl->v_ack = nr; + + /* If T200 has been stopped by the receipt of an I, RR or RNR frame, + * and if there are outstanding I frames, restart T200 */ + if (t200_reset && !rej) { + if (dl->tx_hist[sub_mod(dl->v_send, 1, dl->range_hist)].msg) { + LOGDL(dl, LOGL_INFO, "start T200, due to unacked I frame(s)\n"); + lapd_start_t200(dl); + } + } + + /* This also does a restart, when I or S frame is received */ + + /* Stop T203, if running */ + lapd_stop_t203(dl); + /* Start T203, if T200 is not running in MF EST state, if enabled */ + if (!lapd_is_t200_started(dl) && (dl->t203_sec || dl->t203_usec) && (dl->state == LAPD_STATE_MF_EST)) + lapd_start_t203(dl); + + return 0; +} + +/* L1 -> L2 */ + +/* Receive a LAPD U SABM(E) message from L1 */ +static int lapd_rx_u_sabm(struct msgb *msg, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + int length = lctx->length; + int rc = 0; + uint8_t prim, op; + + prim = PRIM_DL_EST; + op = PRIM_OP_INDICATION; + + LOGDL(dl, LOGL_INFO, "SABM(E) received in state %s\n", lapd_state_name(dl->state)); + /* 5.7.1 */ + dl->seq_err_cond = 0; + /* G.2.2 Wrong value of the C/R bit */ + if (lctx->cr == dl->cr.rem2loc.resp) { + LOGDL(dl, LOGL_ERROR, "SABM response error\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_FRM_UNIMPL, lctx); + return -EINVAL; + } + + /* G.4.5 If SABM is received with L>N201 or with M bit + * set, AN MDL-ERROR-INDICATION is sent to MM. + */ + if (lctx->more || length > lctx->n201) { + LOGDL(dl, LOGL_ERROR, "SABM too large error\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_UFRM_INC_PARAM, lctx); + return -EIO; + } + + switch (dl->state) { + case LAPD_STATE_IDLE: + break; + case LAPD_STATE_TIMER_RECOV: + LOGDL(dl, LOGL_INFO, "SABM command, timer recovery state\n"); + /* If link is lost on the remote side, we start over + * and send DL-ESTABLISH indication again. */ + /* 3GPP TS 44.006 8.6.3 "Procedures for re-establishment" */ + if (length) { + /* check for contention resoultion */ + LOGDL(dl, LOGL_ERROR, "SABM L>0 not expected in timer " + "recovery state\n"); + mdl_error(MDL_CAUSE_SABM_INFO_NOTALL, lctx); + lapd_send_dm(lctx); + msgb_free(msg); + return 0; + } + /* re-establishment, continue below */ + lapd_stop_t200(dl); + break; + case LAPD_STATE_MF_EST: + LOGDL(dl, LOGL_INFO, "SABM command, multiple frame established state\n"); + /* If link is lost on the remote side, we start over + * and send DL-ESTABLISH indication again. */ + /* Additionally, continue in case of content resoltion + * (GSM network). This happens, if the mobile has not + * yet received UA or another mobile (collision) tries + * to establish connection. The mobile must receive + * UA again. */ + /* 5.4.2.1 */ + if (!length) { + /* If no content resolution, this is a + * re-establishment. */ + LOGDL(dl, LOGL_INFO, "Remote reestablish\n"); + break; + } + if (!dl->cont_res) { + LOGDL(dl, LOGL_INFO, "SABM command not allowed in state %s\n", + lapd_state_name(dl->state)); + mdl_error(MDL_CAUSE_SABM_MF, lctx); + msgb_free(msg); + return 0; + } + /* Ignore SABM if content differs from first SABM. */ + if (dl->mode == LAPD_MODE_NETWORK && length) { +#ifdef TEST_CONTENT_RESOLUTION_NETWORK + dl->cont_res->data[0] ^= 0x01; +#endif + if (memcmp(dl->cont_res->data, msg->data, + length)) { + LOGDL(dl, LOGL_INFO, "Another SABM with different content - " + "ignoring!\n"); + msgb_free(msg); + return 0; + } + } + /* send UA again */ + lapd_send_ua(lctx, length, msg->l3h); + msgb_free(msg); + return 0; + case LAPD_STATE_DISC_SENT: + /* 5.4.6.2 send DM with F=P */ + lapd_send_dm(lctx); + /* stop Timer T200 */ + lapd_stop_t200(dl); + msgb_free(msg); + return send_dl_simple(prim, op, lctx); + default: + /* collision: Send UA, but still wait for rx UA, then + * change to MF_EST state. + */ + /* check for contention resoultion */ + if (dl->tx_hist[0].msg && dl->tx_hist[0].msg->len) { + LOGDL(dl, LOGL_NOTICE, "SABM not allowed during contention " + "resolution (state=%s)\n", lapd_state_name(dl->state)); + mdl_error(MDL_CAUSE_SABM_INFO_NOTALL, lctx); + } + lapd_send_ua(lctx, length, msg->l3h); + msgb_free(msg); + return 0; + } + /* save message context for further use */ + memcpy(&dl->lctx, lctx, sizeof(dl->lctx)); +#ifndef TEST_CONTENT_RESOLUTION_NETWORK + /* send UA response */ + lapd_send_ua(lctx, length, msg->l3h); +#endif + /* set Vs, Vr and Va to 0 */ + dl->v_send = dl->v_recv = dl->v_ack = 0; + /* clear tx_hist */ + lapd_dl_flush_hist(dl); + /* enter multiple-frame-established state */ + lapd_dl_newstate(dl, LAPD_STATE_MF_EST); + /* store content resolution data on network side + * Note: cont_res will be removed when changing state again, + * so it must be allocated AFTER lapd_dl_newstate(). */ + if (dl->mode == LAPD_MODE_NETWORK && length) { + dl->cont_res = lapd_msgb_alloc(length, "CONT RES"); + memcpy(msgb_put(dl->cont_res, length), msg->l3h, + length); + LOGDL(dl, LOGL_INFO, "Store content res.\n"); + } + /* send notification to L3 */ + if (length == 0) { + /* 5.4.1.2 Normal establishment procedures */ + rc = send_dl_simple(prim, op, lctx); + msgb_free(msg); + } else { + /* 5.4.1.4 Contention resolution establishment */ + msgb_trim(msg, length); + rc = send_dl_l3(prim, op, lctx, msg); + } + return rc; +} + +/* Receive a LAPD U DM message from L1 */ +static int lapd_rx_u_dm(struct msgb *msg, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + int rc = 0; + + LOGDL(dl, LOGL_INFO, "DM received in state %s\n", lapd_state_name(dl->state)); + /* G.2.2 Wrong value of the C/R bit */ + if (lctx->cr == dl->cr.rem2loc.cmd) { + LOGDL(dl, LOGL_ERROR, "DM command error\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_FRM_UNIMPL, lctx); + return -EINVAL; + } + if (!lctx->p_f) { + /* 5.4.1.2 DM responses with the F bit set to "0" + * shall be ignored. + */ + msgb_free(msg); + return 0; + } + switch (dl->state) { + case LAPD_STATE_SABM_SENT: + break; + case LAPD_STATE_MF_EST: + if (lctx->p_f) { + LOGDL(dl, LOGL_INFO, "unsolicited DM response\n"); + mdl_error(MDL_CAUSE_UNSOL_DM_RESP, lctx); + } else { + LOGDL(dl, LOGL_INFO, "unsolicited DM response, " + "multiple frame established state\n"); + mdl_error(MDL_CAUSE_UNSOL_DM_RESP_MF, lctx); + /* reestablish */ + if (!dl->reestablish) { + msgb_free(msg); + return 0; + } + LOGDL(dl, LOGL_NOTICE, "Performing reestablishment\n"); + lapd_reestablish(dl); + } + msgb_free(msg); + return 0; + case LAPD_STATE_TIMER_RECOV: + /* FP = 0 (DM is normal in case PF = 1) */ + if (!lctx->p_f) { + LOGDL(dl, LOGL_INFO, "unsolicited DM response, multiple frame " + "established state\n"); + mdl_error(MDL_CAUSE_UNSOL_DM_RESP_MF, lctx); + msgb_free(msg); + /* reestablish */ + if (!dl->reestablish) + return 0; + LOGDL(dl, LOGL_NOTICE, "Performing reestablishment\n"); + return lapd_reestablish(dl); + } + break; + case LAPD_STATE_DISC_SENT: + /* stop Timer T200 */ + lapd_stop_t200(dl); + /* go to idle state */ + lapd_dl_flush_tx(dl); + lapd_dl_flush_send(dl); + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + rc = send_dl_simple(PRIM_DL_REL, PRIM_OP_CONFIRM, lctx); + msgb_free(msg); + return 0; + case LAPD_STATE_IDLE: + /* 5.4.5 all other frame types shall be discarded */ + default: + LOGDL(dl, LOGL_INFO, "unsolicited DM response! (discarding)\n"); + msgb_free(msg); + return 0; + } + /* stop timer T200 */ + lapd_stop_t200(dl); + /* go to idle state */ + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + rc = send_dl_simple(PRIM_DL_REL, PRIM_OP_INDICATION, lctx); + msgb_free(msg); + return rc; +} + +/* Receive a LAPD U UI message from L1 */ +static int lapd_rx_u_ui(struct msgb *msg, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + int length = lctx->length; + + LOGDL(dl, LOGL_INFO, "UI received\n"); + /* G.2.2 Wrong value of the C/R bit */ + if (lctx->cr == dl->cr.rem2loc.resp) { + LOGDL(dl, LOGL_ERROR, "UI indicates response error\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_FRM_UNIMPL, lctx); + return -EINVAL; + } + + /* G.4.5 If UI is received with L>N201 or with M bit + * set, AN MDL-ERROR-INDICATION is sent to MM. + */ + if (length > lctx->n201 || lctx->more) { + LOGDL(dl, LOGL_ERROR, "UI too large error (%d > N201(%d) or M=%d)\n", + length, lctx->n201, lctx->more); + msgb_free(msg); + mdl_error(MDL_CAUSE_UFRM_INC_PARAM, lctx); + return -EIO; + } + + /* do some length checks */ + if (length == 0) { + /* 5.3.3 UI frames received with the length indicator + * set to "0" shall be ignored + */ + LOGDL(dl, LOGL_INFO, "length=0 (discarding)\n"); + msgb_free(msg); + return 0; + } + msgb_trim(msg, length); + return send_dl_l3(PRIM_DL_UNIT_DATA, PRIM_OP_INDICATION, lctx, msg); +} + +/* Receive a LAPD U DISC message from L1 */ +static int lapd_rx_u_disc(struct msgb *msg, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + int length = lctx->length; + int rc = 0; + uint8_t prim, op; + + prim = PRIM_DL_REL; + op = PRIM_OP_INDICATION; + + LOGDL(dl, LOGL_INFO, "DISC received in state %s\n", lapd_state_name(dl->state)); + /* flush tx and send buffers */ + lapd_dl_flush_tx(dl); + lapd_dl_flush_send(dl); + /* 5.7.1 */ + dl->seq_err_cond = 0; + /* G.2.2 Wrong value of the C/R bit */ + if (lctx->cr == dl->cr.rem2loc.resp) { + LOGDL(dl, LOGL_ERROR, "DISC response error\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_FRM_UNIMPL, lctx); + return -EINVAL; + } + if (length > 0 || lctx->more) { + /* G.4.4 If a DISC or DM frame is received with L>0 or + * with the M bit set to "1", an MDL-ERROR-INDICATION + * primitive with cause "U frame with incorrect + * parameters" is sent to the mobile management entity. + */ + LOGDL(dl, LOGL_ERROR, "U frame iwth incorrect parameters\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_UFRM_INC_PARAM, lctx); + return -EIO; + } + switch (dl->state) { + case LAPD_STATE_IDLE: + LOGDL(dl, LOGL_INFO, "DISC in idle state\n"); + /* send DM with F=P */ + msgb_free(msg); + return lapd_send_dm(lctx); + case LAPD_STATE_SABM_SENT: + LOGDL(dl, LOGL_INFO, "DISC in SABM state\n"); + /* 5.4.6.2 send DM with F=P */ + lapd_send_dm(lctx); + /* stop Timer T200 */ + lapd_stop_t200(dl); + /* go to idle state */ + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + msgb_free(msg); + return send_dl_simple(PRIM_DL_REL, PRIM_OP_INDICATION, + lctx); + case LAPD_STATE_MF_EST: + case LAPD_STATE_TIMER_RECOV: + LOGDL(dl, LOGL_INFO, "DISC in est state\n"); + break; + case LAPD_STATE_DISC_SENT: + LOGDL(dl, LOGL_INFO, "DISC in disc state\n"); + prim = PRIM_DL_REL; + op = PRIM_OP_CONFIRM; + break; + default: + lapd_send_ua(lctx, length, msg->l3h); + msgb_free(msg); + return 0; + } + /* send UA response */ + lapd_send_ua(lctx, length, msg->l3h); + /* stop Timer T200 */ + lapd_stop_t200(dl); + /* enter idle state, keep tx-buffer with UA response */ + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + /* send notification to L3 */ + rc = send_dl_simple(prim, op, lctx); + msgb_free(msg); + return rc; +} + +/* Receive a LAPD U UA message from L1 */ +static int lapd_rx_u_ua(struct msgb *msg, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + int length = lctx->length; + int rc = 0; + + LOGDL(dl, LOGL_INFO, "UA received in state %s\n", lapd_state_name(dl->state)); + /* G.2.2 Wrong value of the C/R bit */ + if (lctx->cr == dl->cr.rem2loc.cmd) { + LOGDL(dl, LOGL_ERROR, "UA indicates command error\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_FRM_UNIMPL, lctx); + return -EINVAL; + } + + /* G.4.5 If UA is received with L>N201 or with M bit + * set, AN MDL-ERROR-INDICATION is sent to MM. + */ + if (lctx->more || length > lctx->n201) { + LOGDL(dl, LOGL_ERROR, "UA too large error\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_UFRM_INC_PARAM, lctx); + return -EIO; + } + + if (!lctx->p_f) { + /* 5.4.1.2 A UA response with the F bit set to "0" + * shall be ignored. + */ + LOGDL(dl, LOGL_INFO, "F=0 (discarding)\n"); + msgb_free(msg); + return 0; + } + switch (dl->state) { + case LAPD_STATE_SABM_SENT: + break; + case LAPD_STATE_MF_EST: + case LAPD_STATE_TIMER_RECOV: + LOGDL(dl, LOGL_INFO, "unsolicited UA response! (discarding)\n"); + mdl_error(MDL_CAUSE_UNSOL_UA_RESP, lctx); + msgb_free(msg); + return 0; + case LAPD_STATE_DISC_SENT: + LOGDL(dl, LOGL_INFO, "UA in disconnect state\n"); + /* stop Timer T200 */ + lapd_stop_t200(dl); + /* go to idle state */ + lapd_dl_flush_tx(dl); + lapd_dl_flush_send(dl); + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + rc = send_dl_simple(PRIM_DL_REL, PRIM_OP_CONFIRM, lctx); + msgb_free(msg); + return 0; + case LAPD_STATE_IDLE: + /* 5.4.5 all other frame types shall be discarded */ + default: + LOGDL(dl, LOGL_INFO, "unsolicited UA response! (discarding)\n"); + msgb_free(msg); + return 0; + } + LOGDL(dl, LOGL_INFO, "UA in SABM state\n"); + /* stop Timer T200 */ + lapd_stop_t200(dl); + /* compare UA with SABME if contention resolution is applied */ + if (dl->tx_hist[0].msg->len) { + if (length != (dl->tx_hist[0].msg->len) + || !!memcmp(dl->tx_hist[0].msg->data, msg->l3h, + length)) { + LOGDL(dl, LOGL_INFO, "**** UA response mismatches ****\n"); + /* go to idle state */ + lapd_dl_flush_tx(dl); + lapd_dl_flush_send(dl); + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + rc = send_dl_simple(PRIM_DL_REL, PRIM_OP_INDICATION, lctx); + msgb_free(msg); + return 0; + } + } + /* set Vs, Vr and Va to 0 */ + dl->v_send = dl->v_recv = dl->v_ack = 0; + /* clear tx_hist */ + lapd_dl_flush_hist(dl); + /* enter multiple-frame-established state */ + lapd_dl_newstate(dl, LAPD_STATE_MF_EST); + /* send outstanding frames, if any (resume / reconnect) */ + lapd_send_i(dl, __LINE__, false); + /* send notification to L3 */ + rc = send_dl_simple(PRIM_DL_EST, PRIM_OP_CONFIRM, lctx); + msgb_free(msg); + return rc; +} + +/* Receive a LAPD U FRMR message from L1 */ +static int lapd_rx_u_frmr(struct msgb *msg, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + + LOGDL(dl, LOGL_NOTICE, "Frame reject received\n"); + /* send MDL ERROR INIDCATION to L3 */ + mdl_error(MDL_CAUSE_FRMR, lctx); + msgb_free(msg); + /* reestablish */ + if (!dl->reestablish) + return 0; + LOGDL(dl, LOGL_NOTICE, "Performing reestablishment\n"); + return lapd_reestablish(dl); +} + +/* Receive a LAPD U (Unnumbered) message from L1 */ +static int lapd_rx_u(struct msgb *msg, struct lapd_msg_ctx *lctx) +{ + switch (lctx->s_u) { + case LAPD_U_SABM: + case LAPD_U_SABME: + return lapd_rx_u_sabm(msg, lctx); + case LAPD_U_DM: + return lapd_rx_u_dm(msg, lctx); + case LAPD_U_UI: + return lapd_rx_u_ui(msg, lctx); + case LAPD_U_DISC: + return lapd_rx_u_disc(msg, lctx); + case LAPD_U_UA: + return lapd_rx_u_ua(msg, lctx); + case LAPD_U_FRMR: + return lapd_rx_u_frmr(msg, lctx); + default: + /* G.3.1 */ + LOGDL(lctx->dl, LOGL_NOTICE, "Unnumbered frame not allowed\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_FRM_UNIMPL, lctx); + return -EINVAL; + } +} + +/* Receive a LAPD S (Supervisory) message from L1 */ +static int lapd_rx_s(struct msgb *msg, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + int length = lctx->length; + + if (length > 0 || lctx->more) { + /* G.4.3 If a supervisory frame is received with L>0 or + * with the M bit set to "1", an MDL-ERROR-INDICATION + * primitive with cause "S frame with incorrect + * parameters" is sent to the mobile management entity. */ + LOGDL(dl, LOGL_ERROR, "S frame with incorrect parameters\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_SFRM_INC_PARAM, lctx); + return -EIO; + } + + if (lctx->cr == dl->cr.rem2loc.resp + && lctx->p_f + && dl->state != LAPD_STATE_TIMER_RECOV) { + /* 5.4.2.2: Inidcate error on supervisory reponse F=1 */ + LOGDL(dl, LOGL_NOTICE, "S frame response with F=1 error\n"); + mdl_error(MDL_CAUSE_UNSOL_SPRV_RESP, lctx); + } + + switch (dl->state) { + case LAPD_STATE_IDLE: + /* if P=1, respond DM with F=1 (5.2.2) */ + /* 5.4.5 all other frame types shall be discarded */ + if (lctx->p_f) + lapd_send_dm(lctx); /* F=P */ + /* fall though */ + case LAPD_STATE_SABM_SENT: + case LAPD_STATE_DISC_SENT: + LOGDL(dl, LOGL_NOTICE, "S frame ignored in this state\n"); + msgb_free(msg); + return 0; + } + switch (lctx->s_u) { + case LAPD_S_RR: + LOGDL(dl, LOGL_INFO, "RR received in state %s\n", lapd_state_name(dl->state)); + /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */ + lapd_acknowledge(lctx); + + /* 5.5.3.2 */ + if (lctx->cr == dl->cr.rem2loc.cmd + && lctx->p_f) { + if (!dl->own_busy && !dl->seq_err_cond) { + LOGDL(dl, LOGL_INFO, "RR frame command with polling bit set and " + "we are not busy, so we reply with RR frame response\n"); + lapd_send_rr(lctx, 1, 0); + /* NOTE: In case of sequence error condition, + * the REJ frame has been transmitted when + * entering the condition, so it has not be + * done here + */ + } else if (dl->own_busy) { + LOGDL(dl, LOGL_INFO, "RR frame command with polling bit set and " + "we are busy, so we reply with RR frame response\n"); + lapd_send_rnr(lctx, 1, 0); + } + } else if (lctx->cr == dl->cr.rem2loc.resp + && lctx->p_f + && dl->state == LAPD_STATE_TIMER_RECOV) { + LOGDL(dl, LOGL_INFO, "RR response with F==1, and we are in timer recovery " + "state, so we leave that state\n"); + /* V(S) to the N(R) in the RR frame */ + dl->v_send = lctx->n_recv; + /* stop Timer T200 */ + lapd_stop_t200(dl); + /* 5.5.7 Clear timer recovery condition */ + lapd_dl_newstate(dl, LAPD_STATE_MF_EST); + } + /* Send message, if possible due to acknowledged data */ + lapd_send_i(dl, __LINE__, false); + + break; + case LAPD_S_RNR: + LOGDL(dl, LOGL_INFO, "RNR received in state %s\n", lapd_state_name(dl->state)); + /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */ + lapd_acknowledge(lctx); + + /* 5.5.5 */ + /* Set peer receiver busy condition */ + dl->peer_busy = 1; + /* Flush pending messages in TX queue. */ + lapd_dl_flush_tx_queue(dl); + /* stop Timer T200 */ + lapd_stop_t200(dl); + + if (lctx->p_f) { + if (lctx->cr == dl->cr.rem2loc.cmd) { + if (!dl->own_busy) { + LOGDL(dl, LOGL_INFO, "RNR poll command and we are not busy, " + "so we reply with RR final response\n"); + /* Send RR with F=1 */ + lapd_send_rr(lctx, 1, 0); + } else { + LOGDL(dl, LOGL_INFO, "RNR poll command and we are busy, so " + "we reply with RNR final response\n"); + /* Send RNR with F=1 */ + lapd_send_rnr(lctx, 1, 0); + } + } else if (dl->state == LAPD_STATE_TIMER_RECOV) { + LOGDL(dl, LOGL_INFO, "RNR poll response and we in timer recovery " + "state, so we leave that state\n"); + /* 5.5.7 Clear timer recovery condition */ + lapd_dl_newstate(dl, LAPD_STATE_MF_EST); + /* V(S) to the N(R) in the RNR frame */ + dl->v_send = lctx->n_recv; + } + } else + LOGDL(dl, LOGL_INFO, "RNR not polling/final state received\n"); + + /* Send message, if possible due to acknowledged data */ + lapd_send_i(dl, __LINE__, false); + + break; + case LAPD_S_REJ: + LOGDL(dl, LOGL_INFO, "REJ received in state %s\n", lapd_state_name(dl->state)); + /* 5.5.3.1: Acknowlege all tx frames up the the N(R)-1 */ + lapd_acknowledge(lctx); + + /* 5.5.4.1 */ + if (dl->state != LAPD_STATE_TIMER_RECOV) { + /* Clear an existing peer receiver busy condition */ + dl->peer_busy = 0; + /* V(S) and V(A) to the N(R) in the REJ frame */ + dl->v_send = dl->v_ack = lctx->n_recv; + /* Flush pending messages in TX queue. */ + lapd_dl_flush_tx_queue(dl); + /* stop Timer T200 */ + lapd_stop_t200(dl); + /* 5.5.3.2 */ + if (lctx->cr == dl->cr.rem2loc.cmd && lctx->p_f) { + if (!dl->own_busy && !dl->seq_err_cond) { + LOGDL(dl, LOGL_INFO, "REJ poll command not in timer recovery " + "state and not in own busy condition received, so we " + "respond with RR final response\n"); + lapd_send_rr(lctx, 1, 0); + /* NOTE: In case of sequence error + * condition, the REJ frame has been + * transmitted when entering the + * condition, so it has not be done + * here + */ + } else if (dl->own_busy) { + LOGDL(dl, LOGL_INFO, "REJ poll command not in timer recovery " + "state and in own busy condition received, so we " + "respond with RNR final response\n"); + lapd_send_rnr(lctx, 1, 0); + } + } else + LOGDL(dl, LOGL_INFO, "REJ response or not polling command not " + "in timer recovery state received\n"); + /* send MDL ERROR INIDCATION to L3 */ + if (lctx->cr == dl->cr.rem2loc.resp && lctx->p_f) { + LOGDL(dl, LOGL_ERROR, "unsolicited supervisory response!\n"); + mdl_error(MDL_CAUSE_UNSOL_SPRV_RESP, lctx); + } + + } else if (lctx->cr == dl->cr.rem2loc.resp && lctx->p_f) { + LOGDL(dl, LOGL_INFO, "REJ poll response in timer recovery state received\n"); + /* Clear an existing peer receiver busy condition */ + dl->peer_busy = 0; + /* V(S) and V(A) to the N(R) in the REJ frame */ + dl->v_send = dl->v_ack = lctx->n_recv; + /* Flush pending messages in TX queue. */ + lapd_dl_flush_tx_queue(dl); + /* stop Timer T200 */ + lapd_stop_t200(dl); + /* 5.5.7 Clear timer recovery condition */ + lapd_dl_newstate(dl, LAPD_STATE_MF_EST); + } else { + /* Clear an existing peer receiver busy condition */ + dl->peer_busy = 0; + /* V(S) and V(A) to the N(R) in the REJ frame */ + dl->v_send = dl->v_ack = lctx->n_recv; + /* Flush pending messages in TX queue. */ + lapd_dl_flush_tx_queue(dl); + /* 5.5.3.2 */ + if (lctx->cr == dl->cr.rem2loc.cmd && lctx->p_f) { + if (!dl->own_busy && !dl->seq_err_cond) { + LOGDL(dl, LOGL_INFO, "REJ poll command in timer recovery " + "state and not in own busy condition received, so we " + "respond with RR final response\n"); + lapd_send_rr(lctx, 1, 0); + /* NOTE: In case of sequence error + * condition, the REJ frame has been + * transmitted when entering the + * condition, so it has not be done + * here + */ + } else if (dl->own_busy) { + LOGDL(dl, LOGL_INFO, "REJ poll command in timer recovery " + "state and in own busy condition received, so we " + "respond with RNR final response\n"); + lapd_send_rnr(lctx, 1, 0); + } + } else + LOGDL(dl, LOGL_INFO, "REJ response or not polling command in " + "timer recovery state received\n"); + } + + /* FIXME: 5.5.4.2 2) */ + + /* Send message, if possible due to acknowledged data and new V(S) and V(A). */ + lapd_send_i(dl, __LINE__, false); + + break; + default: + /* G.3.1 */ + LOGDL(dl, LOGL_ERROR, "Supervisory frame not allowed\n"); + msgb_free(msg); + mdl_error(MDL_CAUSE_FRM_UNIMPL, lctx); + return -EINVAL; + } + msgb_free(msg); + return 0; +} + +/* Receive a LAPD I (Information) message from L1 */ +static int lapd_rx_i(struct msgb *msg, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + //uint8_t nr = lctx->n_recv; + uint8_t ns = lctx->n_send; + int length = lctx->length; + int rc; + bool i_frame_in_queue = false; + int mdl_cause = 0; + + LOGDL(dl, LOGL_INFO, "I received in state %s on SAPI(%u)\n", + lapd_state_name(dl->state), lctx->sapi); + + /* G.2.2 Wrong value of the C/R bit */ + if (lctx->cr == dl->cr.rem2loc.resp) { + LOGDL(dl, LOGL_ERROR, "I frame response not allowed (state %s)\n", + lapd_state_name(dl->state)); + msgb_free(msg); + mdl_error(MDL_CAUSE_FRM_UNIMPL, lctx); + return -EINVAL; + } + + if (length == 0 || length > lctx->n201) { + /* G.4.2 If the length indicator of an I frame is set + * to a numerical value L>N201 or L=0, an MDL-ERROR-INDICATION + * primitive with cause "I frame with incorrect length" + * is sent to the mobile management entity. */ + LOGDL(dl, LOGL_ERROR, "I frame length not allowed (state %s)\n", + lapd_state_name(dl->state)); + msgb_free(msg); + mdl_error(MDL_CAUSE_IFRM_INC_LEN, lctx); + return -EIO; + } + + /* G.4.2 If the numerical value of L is L<N201 and the M + * bit is set to "1", then an MDL-ERROR-INDICATION primitive with + * cause "I frame with incorrect use of M bit" is sent to the + * mobile management entity. */ + if (lctx->more && length < lctx->n201) { + LOGDL(dl, LOGL_ERROR, "I frame with M bit too short (state %s)\n", + lapd_state_name(dl->state)); + msgb_free(msg); + mdl_error(MDL_CAUSE_IFRM_INC_MBITS, lctx); + return -EIO; + } + + switch (dl->state) { + case LAPD_STATE_IDLE: + /* if P=1, respond DM with F=1 (5.2.2) */ + /* 5.4.5 all other frame types shall be discarded */ + if (lctx->p_f) + lapd_send_dm(lctx); /* F=P */ + /* fall though */ + case LAPD_STATE_SABM_SENT: + case LAPD_STATE_DISC_SENT: + LOGDL(dl, LOGL_NOTICE, "I frame ignored in state %s\n", lapd_state_name(dl->state)); + msgb_free(msg); + return 0; + } + + /* 5.7.1: N(s) sequence error */ + if (ns != dl->v_recv) { + LOGDL(dl, LOGL_NOTICE, "N(S) sequence error: N(S)=%u, V(R)=%u (state %s)\n", + ns, dl->v_recv, lapd_state_name(dl->state)); + /* discard data */ + msgb_free(msg); + /* Send reject, but suppress second reject if LAPD_F_DROP_2ND_REJ flag is set. */ + if (dl->seq_err_cond != 1 || !(dl->lapd_flags & LAPD_F_DROP_2ND_REJ)) { + dl->seq_err_cond = 1; + lapd_send_rej(lctx, lctx->p_f); + } else { + /* If there are two subsequent sequence errors received, + * ignore it. (Ignore every second subsequent error.) + * This happens if our reply with the REJ is too slow, + * so the remote gets a T200 timeout and sends another + * frame with a sequence error. + * Test showed that replying with two subsequent REJ + * messages could the remote L2 process to abort. + * Replying too slow shouldn't happen, but may happen + * over serial link between BB and LAPD. + */ + dl->seq_err_cond = 2; + } + /* Even if N(s) sequence error, acknowledge to N(R)-1 */ + /* 5.5.3.1: Acknowlege all transmitted frames up the N(R)-1 */ + mdl_cause = lapd_acknowledge(lctx); /* V(A) is also set here */ + if (mdl_cause < 0) + mdl_error(-mdl_cause, lctx); + + /* Send message, if possible due to acknowledged data */ + lapd_send_i(dl, __LINE__, false); + + return 0; + } + dl->seq_err_cond = 0; + + /* Increment receiver state */ + dl->v_recv = inc_mod(dl->v_recv, dl->v_range); + LOGDL(dl, LOGL_INFO, "incrementing V(R) to %u\n", dl->v_recv); + + /* Update all pending frames in the queue to the new V(R) state. */ + if (dl->update_pending_frames) { + rc = dl->update_pending_frames(lctx); + if (!rc) + i_frame_in_queue = true; + } + + /* 5.5.3.1: Acknowlege all transmitted frames up the the N(R)-1 */ + mdl_cause = lapd_acknowledge(lctx); /* V(A) is also set here */ + + /* Only if we are not in own receiver busy condition */ + if (!dl->own_busy) { + /* if the frame carries a complete segment */ + if (!lctx->more && !dl->rcv_buffer) { + LOGDL(dl, LOGL_INFO, "message in single I frame\n"); + /* send a DATA INDICATION to L3 */ + msgb_trim(msg, length); + rc = send_dl_l3(PRIM_DL_DATA, PRIM_OP_INDICATION, lctx, + msg); + } else { + /* create rcv_buffer */ + if (!dl->rcv_buffer) { + LOGDL(dl, LOGL_INFO, "message in multiple I frames (first message)\n"); + dl->rcv_buffer = lapd_msgb_alloc(dl->maxf, + "LAPD RX"); + dl->rcv_buffer->l3h = dl->rcv_buffer->data; + } + /* concat. rcv_buffer */ + if (msgb_l3len(dl->rcv_buffer) + length > dl->maxf) { + LOGDL(dl, LOGL_NOTICE, "Received frame overflow!\n"); + } else { + memcpy(msgb_put(dl->rcv_buffer, length), + msg->l3h, length); + } + /* if the last segment was received */ + if (!lctx->more) { + LOGDL(dl, LOGL_INFO, "message in multiple I frames (last message)\n"); + rc = send_dl_l3(PRIM_DL_DATA, + PRIM_OP_INDICATION, lctx, + dl->rcv_buffer); + dl->rcv_buffer = NULL; + } else + LOGDL(dl, LOGL_INFO, "message in multiple I frames (next message)\n"); + msgb_free(msg); + + } + /* the L3 or higher (called in-line above via send_dl_l3) might have destroyed the + * data link meanwhile. See OS#1761 */ + if (dl->state == LAPD_STATE_NULL) + return 0; + } else + LOGDL(dl, LOGL_INFO, "I frame ignored during own receiver busy condition\n"); + + /* Indicate sequence error, if exists. */ + if (mdl_cause < 0) + mdl_error(-mdl_cause, lctx); + + /* Check for P bit */ + if (lctx->p_f) { + /* 5.5.2.1 */ + /* check if we are not in own receiver busy */ + if (!dl->own_busy) { + LOGDL(dl, LOGL_INFO, "we are not busy, send RR\n"); + /* Send RR with F=1 */ + rc = lapd_send_rr(lctx, 1, 0); + } else { + LOGDL(dl, LOGL_INFO, "we are busy, send RNR\n"); + /* Send RNR with F=1 */ + rc = lapd_send_rnr(lctx, 1, 0); + } + } else { + /* 5.5.2.2 */ + /* check if we are not in own receiver busy */ + if (!dl->own_busy) { + /* NOTE: V(R) is already set above */ + rc = lapd_send_i(dl, __LINE__, false); + if (rc && !i_frame_in_queue) { + LOGDL(dl, LOGL_INFO, "we are not busy and have no pending data, " + "send RR\n"); + /* Send RR with F=0 */ + return lapd_send_rr(lctx, 0, 0); + } + /* all I or one RR is sent, we are done */ + return 0; + } else { + LOGDL(dl, LOGL_INFO, "we are busy, send RNR\n"); + /* Send RNR with F=0 */ + rc = lapd_send_rnr(lctx, 0, 0); + } + } + + /* Send message, if possible due to acknowledged data */ + lapd_send_i(dl, __LINE__, false); + + return rc; +} + +/* Receive a LAPD message from L1 */ +int lapd_ph_data_ind(struct msgb *msg, struct lapd_msg_ctx *lctx) +{ + int rc; + + switch (lctx->format) { + case LAPD_FORM_U: + rc = lapd_rx_u(msg, lctx); + break; + case LAPD_FORM_S: + rc = lapd_rx_s(msg, lctx); + break; + case LAPD_FORM_I: + rc = lapd_rx_i(msg, lctx); + break; + default: + LOGDL(lctx->dl, LOGL_NOTICE, "unknown LAPD format 0x%02x\n", lctx->format); + msgb_free(msg); + rc = -EINVAL; + } + return rc; +} + +/*! Enqueue next LAPD frame and run pending T200. (Must be called when frame is ready to send.) + * The caller (LAPDm code) calls this function before it sends the next frame. + * If there is no frame in the TX queue, LAPD will enqueue next I-frame, if possible. + * If the T200 is pending, it is changed to running state. + * \param[in] lctx LAPD context + * \param[out] rc set to 1, if timer T200 state changed to running, set to 0, if not. */ +int lapd_ph_rts_ind(struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + + /* If there is no pending frame, try to enqueue next I frame. */ + if (llist_empty(&dl->tx_queue) && (dl->state == LAPD_STATE_MF_EST || dl->state == LAPD_STATE_TIMER_RECOV)) { + /* Send an I frame, if there are pending outgoing messages. */ + lapd_send_i(dl, __LINE__, true); + } + + /* Run T200 at RTS, if pending. Tell caller that is has been started. (rc = 1) */ + if (dl->t200_rts == LAPD_T200_RTS_PENDING) { + dl->t200_rts = LAPD_T200_RTS_RUNNING; + return 1; + } + + return 0; +} + +/* L3 -> L2 */ + +/* send unit data */ +static int lapd_udata_req(struct osmo_dlsap_prim *dp, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + struct msgb *msg = dp->oph.msg; + struct lapd_msg_ctx nctx; + + memcpy(&nctx, lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.cmd; + nctx.format = LAPD_FORM_U; + nctx.s_u = LAPD_U_UI; + /* keep nctx.p_f */ + nctx.length = msg->len; + nctx.more = 0; + + return dl->send_ph_data_req(&nctx, msg); +} + +static void msg_to_tx_hist(struct lapd_history *tx_hist, const struct msgb *msg, int length, int more) +{ + tx_hist->msg = lapd_msgb_alloc(msg->len, "HIST"); + tx_hist->more = more; + msgb_put(tx_hist->msg, msg->len); + if (length) + memcpy(tx_hist->msg->data, msg->l3h, msg->len); +} + +static void msg_to_tx_hist0(struct lapd_datalink *dl, const struct msgb *msg) +{ + return msg_to_tx_hist(&dl->tx_hist[0], msg, msg->len, 0); +} + +/* request link establishment */ +static int lapd_est_req(struct osmo_dlsap_prim *dp, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + struct msgb *msg = dp->oph.msg; + struct lapd_msg_ctx nctx; + + if (msg->len) + LOGDL(dl, LOGL_INFO, "perform establishment with content (SABM)\n"); + else + LOGDL(dl, LOGL_INFO, "perform normal establishm. (SABM)\n"); + + /* Flush send-queue */ + /* Clear send-buffer */ + lapd_dl_flush_send(dl); + /* be sure that history is empty */ + lapd_dl_flush_hist(dl); + + /* save message context for further use */ + memcpy(&dl->lctx, lctx, sizeof(dl->lctx)); + + /* Discard partly received L3 message */ + msgb_free(dl->rcv_buffer); + dl->rcv_buffer = NULL; + + /* assemble message */ + memcpy(&nctx, &dl->lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.cmd; + nctx.format = LAPD_FORM_U; + nctx.s_u = (dl->use_sabme) ? LAPD_U_SABME : LAPD_U_SABM; + nctx.p_f = 1; + nctx.length = msg->len; + nctx.more = 0; + + /* Transmit-buffer carries exactly one segment */ + msg_to_tx_hist0(dl, msg); + + /* set Vs to 0, because it is used as index when resending SABM */ + dl->v_send = 0; + + /* Set states */ + dl->own_busy = dl->peer_busy = 0; + dl->retrans_ctr = 0; + lapd_dl_newstate(dl, LAPD_STATE_SABM_SENT); + + /* Tramsmit and start T200 */ + dl->send_ph_data_req(&nctx, msg); + lapd_start_t200(dl); + + return 0; +} + +/* send data */ +static int lapd_data_req(struct osmo_dlsap_prim *dp, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + struct msgb *msg = dp->oph.msg; + + if (msgb_l3len(msg) == 0) { + LOGDL(dl, LOGL_ERROR, "writing an empty message is not possible\n"); + msgb_free(msg); + return -1; + } + + LOGDL(dl, LOGL_INFO, "writing message to send-queue: l3len: %d\n", msgb_l3len(msg)); + + /* Write data into the send queue */ + msgb_enqueue(&dl->send_queue, msg); + + /* Send message, if possible */ + lapd_send_i(dl, __LINE__, false); + + return 0; +} + +/* Send next I frame from queued/buffered data */ +static int lapd_send_i(struct lapd_datalink *dl, int line, bool rts) +{ + struct lapd_msg_ctx *lctx = &dl->lctx; + uint8_t k = dl->k; + uint8_t h; + struct msgb *msg; + int length, left; + int rc = - 1; /* we sent nothing */ + struct lapd_msg_ctx nctx; + + if (!rts) + LOGDL(dl, LOGL_INFO, "%s() called from line %d\n", __func__, line); + + if ((dl->lapd_flags & LAPD_F_RTS) && !llist_empty(&dl->tx_queue)) { + if (!rts) + LOGDL(dl, LOGL_INFO, "There is a frame in the TX queue, not checking for sending I frame.\n"); + return rc; + } + + next_frame: + + if (dl->peer_busy) { + if (!rts) + LOGDL(dl, LOGL_INFO, "Peer busy, not sending.\n"); + return rc; + } + + if (dl->state == LAPD_STATE_TIMER_RECOV) { + if (!rts) + LOGDL(dl, LOGL_INFO, "Timer recovery, not sending.\n"); + return rc; + } + + /* If the send state variable V(S) is equal to V(A) plus k + * (where k is the maximum number of outstanding I frames - see + * subclause 5.8.4), the data link layer entity shall not transmit any + * new I frames, but shall retransmit an I frame as a result + * of the error recovery procedures as described in subclauses 5.5.4 and + * 5.5.7. */ + if (dl->v_send == add_mod(dl->v_ack, k, dl->v_range)) { + if (!rts) + LOGDL(dl, LOGL_INFO, "k frames outstanding, not sending more. (k=%u V(S)=%u V(A)=%u)\n", + k, dl->v_send, dl->v_ack); + return rc; + } + + h = do_mod(dl->v_send, dl->range_hist); + + /* if we have no tx_hist yet, we create it */ + if (!dl->tx_hist[h].msg) { + /* Get next message into send-buffer, if any */ + if (!dl->send_buffer) { + next_message: + dl->send_out = 0; + dl->send_buffer = msgb_dequeue(&dl->send_queue); + /* No more data to be sent */ + if (!dl->send_buffer) + return rc; + LOGDL(dl, LOGL_INFO, "get message from send-queue\n"); + } + + /* How much is left in the send-buffer? */ + left = msgb_l3len(dl->send_buffer) - dl->send_out; + /* Segment, if data exceeds N201 */ + length = left; + if (length > lctx->n201) + length = lctx->n201; + LOGDL(dl, LOGL_INFO, "msg-len %d sent %d left %d N201 %d length %d " + "first byte %02x\n", msgb_l3len(dl->send_buffer), dl->send_out, left, + lctx->n201, length, dl->send_buffer->l3h[0]); + /* If message in send-buffer is completely sent */ + if (left == 0) { + msgb_free(dl->send_buffer); + dl->send_buffer = NULL; + goto next_message; + } + + LOGDL(dl, LOGL_INFO, "send I frame %sV(S)=%d\n", + (left > length) ? "segment " : "", dl->v_send); + + /* Create I frame (segment) and transmit-buffer content */ + msg = lapd_msgb_alloc(length, "LAPD I"); + msg->l3h = msgb_put(msg, length); + /* assemble message */ + memcpy(&nctx, lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.cmd; + nctx.format = LAPD_FORM_I; + nctx.p_f = 0; + nctx.n_send = dl->v_send; + nctx.n_recv = dl->v_recv; + nctx.length = length; + if (left > length) + nctx.more = 1; + else + nctx.more = 0; + if (length) + memcpy(msg->l3h, dl->send_buffer->l3h + dl->send_out, + length); + /* store in tx_hist */ + msg_to_tx_hist(&dl->tx_hist[h], msg, length, nctx.more); + + /* Add length to track how much is already in the tx buffer */ + dl->send_out += length; + } else { + LOGDL(dl, LOGL_INFO, "resend I frame from tx buffer V(S)=%d\n", dl->v_send); + + /* Create I frame (segment) from tx_hist */ + length = dl->tx_hist[h].msg->len; + msg = lapd_msgb_alloc(length, "LAPD I resend"); + msg->l3h = msgb_put(msg, length); + /* assemble message */ + memcpy(&nctx, lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.cmd; + nctx.format = LAPD_FORM_I; + nctx.p_f = 0; + nctx.n_send = dl->v_send; + nctx.n_recv = dl->v_recv; + nctx.length = length; + nctx.more = dl->tx_hist[h].more; + if (length) + memcpy(msg->l3h, dl->tx_hist[h].msg->data, length); + } + + /* The value of the send state variable V(S) shall be incremented by 1 + * at the end of the transmission of the I frame */ + dl->v_send = inc_mod(dl->v_send, dl->v_range); + + /* If timer T200 is not running at the time right before transmitting a + * frame, when the PH-READY-TO-SEND primitive is received from the + * physical layer., it shall be set. */ + if (!lapd_is_t200_started(dl)) { + /* stop Timer T203, if running */ + lapd_stop_t203(dl); + /* start Timer T200 */ + lapd_start_t200(dl); + } + + dl->send_ph_data_req(&nctx, msg); + + /* When using RTS, we send only one frame. */ + if ((dl->lapd_flags & LAPD_F_RTS)) + return 0; + + rc = 0; /* We sent an I frame, so sending RR frame is not required. */ + goto next_frame; +} + +/* request link suspension */ +static int lapd_susp_req(struct osmo_dlsap_prim *dp, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + struct msgb *msg = dp->oph.msg; + + LOGDL(dl, LOGL_INFO, "perform suspension\n"); + + /* put back the send-buffer to the send-queue (first position) */ + if (dl->send_buffer) { + LOGDL(dl, LOGL_INFO, "put frame in sendbuffer back to queue\n"); + llist_add(&dl->send_buffer->list, &dl->send_queue); + dl->send_buffer = NULL; + } else + LOGDL(dl, LOGL_INFO, "no frame in sendbuffer\n"); + + /* Clear transmit buffer, but keep send buffer */ + lapd_dl_flush_tx(dl); + /* Stop timers (there is no state change, so we must stop all timers */ + lapd_stop_t200(dl); + lapd_stop_t203(dl); + + msgb_free(msg); + + return send_dl_simple(PRIM_DL_SUSP, PRIM_OP_CONFIRM, &dl->lctx); +} + +/* request, resume or reconnect of link */ +static int lapd_res_req(struct osmo_dlsap_prim *dp, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + struct msgb *msg = dp->oph.msg; + struct lapd_msg_ctx nctx; + + LOGDL(dl, LOGL_INFO, "perform re-establishment (SABM) length=%d\n", msg->len); + + /* be sure that history is empty */ + lapd_dl_flush_hist(dl); + + /* save message context for further use */ + memcpy(&dl->lctx, lctx, sizeof(dl->lctx)); + + /* Replace message in the send-buffer (reconnect) */ + msgb_free(dl->send_buffer); + dl->send_buffer = NULL; + + dl->send_out = 0; + if (msg->len) { + /* Write data into the send buffer, to be sent first */ + dl->send_buffer = msg; + } else { + msgb_free(msg); + msg = NULL; + dl->send_buffer = NULL; + } + + /* Discard partly received L3 message */ + msgb_free(dl->rcv_buffer); + dl->rcv_buffer = NULL; + + /* Create new msgb (old one is now free) */ + msg = lapd_msgb_alloc(0, "LAPD SABM"); + msg->l3h = msg->data; + /* assemble message */ + memcpy(&nctx, &dl->lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.cmd; + nctx.format = LAPD_FORM_U; + nctx.s_u = (dl->use_sabme) ? LAPD_U_SABME : LAPD_U_SABM; + nctx.p_f = 1; + nctx.length = 0; + nctx.more = 0; + + msg_to_tx_hist0(dl, msg); + + /* set Vs to 0, because it is used as index when resending SABM */ + dl->v_send = 0; + + /* Set states */ + dl->own_busy = dl->peer_busy = 0; + dl->retrans_ctr = 0; + lapd_dl_newstate(dl, LAPD_STATE_SABM_SENT); + + /* Tramsmit and start T200 */ + dl->send_ph_data_req(&nctx, msg); + lapd_start_t200(dl); + + return 0; +} + +/* requesst release of link */ +static int lapd_rel_req(struct osmo_dlsap_prim *dp, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + struct msgb *msg = dp->oph.msg; + struct lapd_msg_ctx nctx; + + /* local release */ + if (dp->u.rel_req.mode) { + LOGDL(dl, LOGL_INFO, "perform local release\n"); + msgb_free(msg); + /* stop Timer T200 */ + lapd_stop_t200(dl); + /* enter idle state, T203 is stopped here, if running */ + lapd_dl_newstate(dl, LAPD_STATE_IDLE); + /* flush buffers */ + lapd_dl_flush_tx(dl); + lapd_dl_flush_send(dl); + /* send notification to L3 */ + return send_dl_simple(PRIM_DL_REL, PRIM_OP_CONFIRM, &dl->lctx); + } + + /* in case we are already disconnecting */ + if (dl->state == LAPD_STATE_DISC_SENT) + return -EBUSY; + + /* flush tx_hist */ + lapd_dl_flush_hist(dl); + + LOGDL(dl, LOGL_INFO, "perform normal release (DISC)\n"); + + /* Push LAPD header on msgb */ + /* assemble message */ + memcpy(&nctx, &dl->lctx, sizeof(nctx)); + /* keep nctx.ldp */ + /* keep nctx.sapi */ + /* keep nctx.tei */ + nctx.cr = dl->cr.loc2rem.cmd; + nctx.format = LAPD_FORM_U; + nctx.s_u = LAPD_U_DISC; + nctx.p_f = 1; + nctx.length = 0; + nctx.more = 0; + + msg_to_tx_hist0(dl, msg); + + /* set Vs to 0, because it is used as index when resending DISC */ + dl->v_send = 0; + + /* Set states */ + dl->own_busy = dl->peer_busy = 0; + dl->retrans_ctr = 0; + lapd_dl_newstate(dl, LAPD_STATE_DISC_SENT); + + /* Tramsmit and start T200 */ + dl->send_ph_data_req(&nctx, msg); + lapd_start_t200(dl); + + return 0; +} + +/* request release of link in idle state */ +static int lapd_rel_req_idle(struct osmo_dlsap_prim *dp, + struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + struct msgb *msg = dp->oph.msg; + + msgb_free(msg); + + /* send notification to L3 */ + return send_dl_simple(PRIM_DL_REL, PRIM_OP_CONFIRM, &dl->lctx); +} + +/* statefull handling for DL SAP messages from L3 */ +static const struct l2downstate { + uint32_t states; + int prim, op; + const char *name; + int (*rout) (struct osmo_dlsap_prim *dp, + struct lapd_msg_ctx *lctx); +} l2downstatelist[] = { + /* create and send UI command */ + {ALL_STATES, + PRIM_DL_UNIT_DATA, PRIM_OP_REQUEST, + "DL-UNIT-DATA-REQUEST", lapd_udata_req}, + + /* create and send SABM command */ + {SBIT(LAPD_STATE_IDLE), + PRIM_DL_EST, PRIM_OP_REQUEST, + "DL-ESTABLISH-REQUEST", lapd_est_req}, + + /* create and send I command */ + {SBIT(LAPD_STATE_MF_EST) | + SBIT(LAPD_STATE_TIMER_RECOV), + PRIM_DL_DATA, PRIM_OP_REQUEST, + "DL-DATA-REQUEST", lapd_data_req}, + + /* suspend datalink */ + {SBIT(LAPD_STATE_MF_EST) | + SBIT(LAPD_STATE_TIMER_RECOV), + PRIM_DL_SUSP, PRIM_OP_REQUEST, + "DL-SUSPEND-REQUEST", lapd_susp_req}, + + /* create and send SABM command (resume) */ + {SBIT(LAPD_STATE_MF_EST) | + SBIT(LAPD_STATE_TIMER_RECOV), + PRIM_DL_RES, PRIM_OP_REQUEST, + "DL-RESUME-REQUEST", lapd_res_req}, + + /* create and send SABM command (reconnect) */ + {SBIT(LAPD_STATE_IDLE) | + SBIT(LAPD_STATE_MF_EST) | + SBIT(LAPD_STATE_TIMER_RECOV), + PRIM_DL_RECON, PRIM_OP_REQUEST, + "DL-RECONNECT-REQUEST", lapd_res_req}, + + /* create and send DISC command */ + {SBIT(LAPD_STATE_SABM_SENT) | + SBIT(LAPD_STATE_MF_EST) | + SBIT(LAPD_STATE_TIMER_RECOV) | + SBIT(LAPD_STATE_DISC_SENT), + PRIM_DL_REL, PRIM_OP_REQUEST, + "DL-RELEASE-REQUEST", lapd_rel_req}, + + /* release in idle state */ + {SBIT(LAPD_STATE_IDLE), + PRIM_DL_REL, PRIM_OP_REQUEST, + "DL-RELEASE-REQUEST", lapd_rel_req_idle}, +}; + +#define L2DOWNSLLEN \ + (sizeof(l2downstatelist) / sizeof(struct l2downstate)) + +int lapd_recv_dlsap(struct osmo_dlsap_prim *dp, struct lapd_msg_ctx *lctx) +{ + struct lapd_datalink *dl = lctx->dl; + int i, supported = 0; + struct msgb *msg = dp->oph.msg; + int rc; + + /* find function for current state and message */ + for (i = 0; i < L2DOWNSLLEN; i++) { + if (dp->oph.primitive == l2downstatelist[i].prim + && dp->oph.operation == l2downstatelist[i].op) { + supported = 1; + if ((SBIT(dl->state) & l2downstatelist[i].states)) + break; + } + } + if (!supported) { + LOGDL(dl, LOGL_NOTICE, "Message %u/%u unsupported\n", + dp->oph.primitive, dp->oph.operation); + msgb_free(msg); + return 0; + } + if (i == L2DOWNSLLEN) { + LOGDL(dl, LOGL_NOTICE, "Message %u/%u unhandled at this state %s\n", + dp->oph.primitive, dp->oph.operation, lapd_state_name(dl->state)); + msgb_free(msg); + return 0; + } + + LOGDL(dl, LOGL_INFO, "Message %s received in state %s\n", + l2downstatelist[i].name, lapd_state_name(dl->state)); + + rc = l2downstatelist[i].rout(dp, lctx); + + return rc; +} + +/*! @} */ |