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libosmocore/src/gsm/lapd_core.c

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/*! \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 <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/gsm/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_msg_ctx *lctx, int line);
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(struct lapd_datalink *dl)
{
struct msgb *msg;
while ((msg = msgb_dequeue(&dl->tx_queue)))
msgb_free(msg);
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 (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);
}
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 (!osmo_timer_pending(&dl->t200))
return;
LOGDL(dl, LOGL_INFO, "stop T200\n");
osmo_timer_del(&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);
}
/* 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 */
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);
/* increment re-transmission counter */
dl->retrans_ctr++;
/* restart T200 (PH-READY-TO-SEND) */
lapd_start_t200(dl);
break;
case LAPD_STATE_DISC_SENT:
/* 5.4.4.3 */
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);
/* increment re-transmission counter */
dl->retrans_ctr++;
/* 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 */
static void lapd_acknowledge(struct lapd_msg_ctx *lctx)
{
struct lapd_datalink *dl = lctx->dl;
uint8_t nr = lctx->n_recv;
int s = 0, rej = 0, t200_reset = 0;
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 = 1;
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");
mdl_error(MDL_CAUSE_SEQ_ERR, lctx);
}
}
/* 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 (!osmo_timer_pending(&dl->t200)
&& (dl->t203_sec || dl->t203_usec)
&& (dl->state == LAPD_STATE_MF_EST)) {
lapd_start_t203(dl);
}
}
/* 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(lctx, __LINE__);
/* 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(lctx, __LINE__);
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;
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(lctx, __LINE__);
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;
/* 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;
/* 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;
/* 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 */
lapd_send_i(lctx, __LINE__);
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;
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);
if (dl->seq_err_cond != 1) {
/* FIXME: help me understand what exactly todo here
*/
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 */
lapd_acknowledge(lctx); /* V(A) is also set here */
/* Send message, if possible due to acknowledged data */
lapd_send_i(lctx, __LINE__);
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);
/* 5.5.3.1: Acknowlege all transmitted frames up the the N(R)-1 */
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");
/* 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(lctx, __LINE__);
/* if update_pending_iframe returns 0 it updated
* the lapd header of an iframe in the tx queue */
if (rc && dl->update_pending_frames)
rc = dl->update_pending_frames(lctx);
if (rc) {
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(lctx, __LINE__);
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\n");
msgb_free(msg);
rc = -EINVAL;
}
return rc;
}
/* 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);
}
/* 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 */
dl->tx_hist[0].msg = lapd_msgb_alloc(msg->len, "HIST");
msgb_put(dl->tx_hist[0].msg, msg->len);
if (msg->len)
memcpy(dl->tx_hist[0].msg->data, msg->l3h, msg->len);
dl->tx_hist[0].more = 0;
/* 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->lctx, __LINE__);
return 0;
}
/* Send next I frame from queued/buffered data */
static int lapd_send_i(struct lapd_msg_ctx *lctx, int line)
{
struct lapd_datalink *dl = lctx->dl;
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;
LOGDL(dl, LOGL_INFO, "%s() called from line %d\n", __func__, line);
next_frame:
if (dl->peer_busy) {
LOGDL(dl, LOGL_INFO, "peer busy, not sending\n");
return rc;
}
if (dl->state == LAPD_STATE_TIMER_RECOV) {
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)) {
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, &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 = 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 */
dl->tx_hist[h].msg = lapd_msgb_alloc(msg->len, "HIST");
msgb_put(dl->tx_hist[h].msg, msg->len);
if (length)
memcpy(dl->tx_hist[h].msg->data, msg->l3h, msg->len);
dl->tx_hist[h].more = 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, &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 = 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 (!osmo_timer_pending(&dl->t200)) {
/* stop Timer T203, if running */
lapd_stop_t203(dl);
/* start Timer T200 */
lapd_start_t200(dl);
}
dl->send_ph_data_req(&nctx, msg);
rc = 0; /* we sent something */
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;
dl->tx_hist[0].msg = lapd_msgb_alloc(msg->len, "HIST");
msgb_put(dl->tx_hist[0].msg, msg->len);
if (msg->len)
memcpy(dl->tx_hist[0].msg->data, msg->l3h, msg->len);
dl->tx_hist[0].more = 0;
/* 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;
dl->tx_hist[0].msg = lapd_msgb_alloc(msg->len, "HIST");
msgb_put(dl->tx_hist[0].msg, msg->len);
if (msg->len)
memcpy(dl->tx_hist[0].msg->data, msg->l3h, msg->len);
dl->tx_hist[0].more = 0;
/* 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;
}
/*! @} */
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