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authorroot <root@nuedel.(none)>2011-09-26 11:23:06 +0200
committerHarald Welte <laforge@gnumonks.org>2011-10-10 08:38:58 +0200
commitaf48bed556079313074d8a2ea132fd689af8a100 (patch)
treec027cc6e8f93257ddcda20c4f794d83760e443d0 /src/gsm
parent8a996b4844f8f89c16ce5062c74942d57f6f73b4 (diff)
Split of LAPDm into a core part and a GSM specific part
Instead of mixing together the GSM layer 1 interface and RSL interface with the implementation of LAPD, the core function of LAPD is now extracted from LAPDm. The core implementation is now in lapd_core.c and lapd_core.h respectively. The lapd_core.c implements exactly one datalink instance for one SAP. The surrounding implementation "lapdm.c" codes/decodes the layer 2 headers and handles multiplexing and datalink instances, as well as translates primitives from/to RSL layer. lapd_core.c can now be used for other LAPD implementations. (ISDN/ABIS)
Diffstat (limited to 'src/gsm')
-rw-r--r--src/gsm/Makefile.am2
-rw-r--r--src/gsm/lapd_core.c2128
-rw-r--r--src/gsm/lapdm.c1947
3 files changed, 2456 insertions, 1621 deletions
diff --git a/src/gsm/Makefile.am b/src/gsm/Makefile.am
index f5e46769..c0f72b3f 100644
--- a/src/gsm/Makefile.am
+++ b/src/gsm/Makefile.am
@@ -10,6 +10,6 @@ lib_LTLIBRARIES = libosmogsm.la
libosmogsm_la_SOURCES = a5.c rxlev_stat.c tlv_parser.c comp128.c gsm_utils.c \
rsl.c gsm48.c gsm48_ie.c gsm0808.c sysinfo.c \
gprs_cipher_core.c gsm0480.c abis_nm.c gsm0502.c \
- lapdm.c
+ lapd_core.c lapdm.c
libosmogsm_la_LDFLAGS = -version-info $(LIBVERSION)
libosmogsm_la_LIBADD = $(top_builddir)/src/libosmocore.la
diff --git a/src/gsm/lapd_core.c b/src/gsm/lapd_core.c
new file mode 100644
index 00000000..f7408e54
--- /dev/null
+++ b/src/gsm/lapd_core.c
@@ -0,0 +1,2128 @@
+/* LAPD core implementation */
+
+/* (C) 2010-2011 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2010-2011 by Andreas Eversberg <jolly@eversberg.eu>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+/*! \addtogroup lapd
+ * @{
+ */
+
+/*! \file lapd.c */
+
+/*!
+ * 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.
+ *
+ */
+
+/* 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 <arpa/inet.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>
+
+/* 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 SBIT(a) (1 << a)
+#define ALL_STATES 0xffffffff
+
+/* 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_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 */
+ if (dl->send_buffer) {
+ msgb_free(dl->send_buffer);
+ dl->send_buffer = NULL;
+ }
+}
+
+static void lapd_dl_flush_hist(struct lapd_datalink *dl)
+{
+ unsigned int i;
+
+ 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 char *lapd_state_names[] = {
+ "LAPD_STATE_NULL",
+ "LAPD_STATE_TEI_UNASS",
+ "LAPD_STATE_ASS_TEI_WAIT",
+ "LAPD_STATE_EST_TEI_WAIT",
+ "LAPD_STATE_IDLE",
+ "LAPD_STATE_SABM_SENT",
+ "LAPD_STATE_DISC_SENT",
+ "LAPD_STATE_MF_EST",
+ "LAPD_STATE_TIMER_RECOV",
+
+};
+
+static void lapd_dl_newstate(struct lapd_datalink *dl, uint32_t state)
+{
+ LOGP(DLLAPD, LOGL_INFO, "new state %s -> %s\n",
+ lapd_state_names[dl->state], lapd_state_names[state]);
+
+ if (state != LAPD_STATE_MF_EST && dl->state == LAPD_STATE_MF_EST) {
+ /* stop T203 on leaving MF EST state, if running */
+ if (osmo_timer_pending(&dl->t203)) {
+ LOGP(DLLAPD, LOGL_INFO, "stop T203\n");
+ osmo_timer_del(&dl->t203);
+ }
+ /* remove content res. (network side) on leaving MF EST state */
+ if (dl->cont_res) {
+ 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) {
+ LOGP(DLLAPD, LOGL_INFO, "start T203\n");
+ osmo_timer_schedule(&dl->t203, dl->t203_sec, dl->t203_usec);
+ }
+
+ dl->state = state;
+}
+
+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);
+
+static void *tall_lapd_ctx = NULL;
+
+/* init datalink instance and allocate history */
+void lapd_dl_init(struct lapd_datalink *dl, uint8_t k, uint8_t v_range,
+ int maxf)
+{
+ 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;
+ dl->t200.data = dl;
+ dl->t200.cb = &lapd_t200_cb;
+ dl->t203_sec = 10;
+ dl->t203_usec = 0;
+ dl->t203.data = dl;
+ dl->t203.cb = &lapd_t203_cb;
+ 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;
+ }
+ }
+
+ LOGP(DLLAPD, 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);
+
+ if (!tall_lapd_ctx)
+ tall_lapd_ctx = talloc_named_const(NULL, 1, "lapd context");
+ dl->tx_hist = (struct lapd_history *) talloc_zero_array(tall_lapd_ctx,
+ struct log_info, dl->range_hist);
+}
+
+/* reset to IDLE state */
+void lapd_dl_reset(struct lapd_datalink *dl)
+{
+ if (dl->state == LAPD_STATE_IDLE)
+ return;
+ LOGP(DLLAPD, LOGL_INFO, "Resetting LAPDm 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 */
+ if (dl->rcv_buffer) {
+ msgb_free(dl->rcv_buffer);
+ dl->rcv_buffer = NULL;
+ }
+ /* reset Timers */
+ osmo_timer_del(&dl->t200);
+ osmo_timer_del(&dl->t203);
+}
+
+/* reset and de-allocate history buffer */
+void lapd_dl_exit(struct lapd_datalink *dl)
+{
+ /* free all ressources except history buffer */
+ lapd_dl_reset(dl);
+ /* free history buffer list */
+ talloc_free(dl->tx_hist);
+}
+
+/*! \brief 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)
+{
+ struct msgb *msg = lapd_msgb_alloc(0, "DUMMY");
+
+ return send_dl_l3(prim, op, lctx, msg);
+}
+
+/* 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;
+
+ LOGP(DLLAPD, LOGL_NOTICE, "sending MDL-ERROR-IND cause %d\n",
+ cause);
+ 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;
+
+ 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;
+
+ LOGP(DLLAPD, LOGL_INFO, "lapd_t200_cb(%p) state=%d\n", dl,
+ (int) dl->state);
+
+ switch (dl->state) {
+ case LAPD_STATE_SABM_SENT:
+ /* 5.4.1.3 */
+ if (dl->retrans_ctr + 1 >= dl->n200_est_rel + 1) {
+ /* send RELEASE INDICATION to L3 */
+ send_dl_simple(PRIM_DL_REL, PRIM_OP_INDICATION,
+ &dl->lctx);
+ /* 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 */
+ break;
+ }
+ /* retransmit SABM command */
+ lapd_send_resend(dl);
+ /* increment re-transmission counter */
+ dl->retrans_ctr++;
+ /* restart T200 (PH-READY-TO-SEND) */
+ osmo_timer_schedule(&dl->t200, dl->t200_sec, dl->t200_usec);
+ break;
+ case LAPD_STATE_DISC_SENT:
+ /* 5.4.4.3 */
+ if (dl->retrans_ctr + 1 >= dl->n200_est_rel + 1) {
+ /* send RELEASE INDICATION to L3 */
+ send_dl_simple(PRIM_DL_REL, PRIM_OP_CONFIRM, &dl->lctx);
+ /* 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 */
+ break;
+ }
+ /* retransmit DISC command */
+ lapd_send_resend(dl);
+ /* increment re-transmission counter */
+ dl->retrans_ctr++;
+ /* restart T200 (PH-READY-TO-SEND) */
+ osmo_timer_schedule(&dl->t200, dl->t200_sec, dl->t200_usec);
+ 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;
+
+ LOGP(DLLAPD, 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 {
+ LOGP(DLLAPD, LOGL_INFO, "unhandled, "
+ "pls. fix\n");
+ }
+ }
+ /* restart T200 (PH-READY-TO-SEND) */
+ osmo_timer_schedule(&dl->t200, dl->t200_sec,
+ dl->t200_usec);
+ } else {
+ /* send MDL ERROR INIDCATION to L3 */
+ mdl_error(MDL_CAUSE_T200_EXPIRED, &dl->lctx);
+ /* reestablish */
+ if (!dl->reestablish)
+ break;
+ LOGP(DLLAPD, LOGL_NOTICE, "N200 reached, performing "
+ "reestablishment.\n");
+ lapd_reestablish(dl);
+ }
+ break;
+ default:
+ LOGP(DLLAPD, LOGL_INFO, "T200 expired in unexpected "
+ "dl->state %d\n", (int) dl->state);
+ }
+}
+
+/* Timer callback on T203 expiry */
+static void lapd_t203_cb(void *data)
+{
+ struct lapd_datalink *dl = data;
+
+ LOGP(DLLAPD, LOGL_INFO, "lapd_t203_cb(%p) state=%d\n", dl,
+ (int) dl->state);
+
+ if (dl->state != LAPD_STATE_MF_EST) {
+ LOGP(DLLAPD, 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) {
+ LOGP(DLLAPD, LOGL_INFO, "transmit an RR poll command\n");
+ /* Send RR with P=1 */
+ lapd_send_rr(&dl->lctx, 1, 1);
+ } else {
+ LOGP(DLLAPD, LOGL_INFO, "transmit an RNR poll command\n");
+ /* Send RNR with P=1 */
+ lapd_send_rnr(&dl->lctx, 1, 1);
+ }
+ /* start T200 */
+ osmo_timer_schedule(&dl->t200, dl->t200_sec, dl->t200_usec);
+}
+
+/* 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, t200_start = 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;
+ LOGP(DLLAPD, 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)) {
+ LOGP(DLLAPD, LOGL_INFO, "reset t200\n");
+ t200_reset = 1;
+ osmo_timer_del(&dl->t200);
+ /* 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)) {
+ LOGP(DLLAPD, 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 reset 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) {
+ LOGP(DLLAPD, LOGL_INFO, "start T200, due to unacked I "
+ "frame(s)\n");
+ t200_start = 1;
+ osmo_timer_schedule(&dl->t200, dl->t200_sec,
+ dl->t200_usec);
+ }
+ }
+
+ /* This also does a restart, when I or S frame is received */
+
+ /* Stop T203, if running */
+ if (osmo_timer_pending(&dl->t203)) {
+ osmo_timer_del(&dl->t203);
+ LOGP(DLLAPD, LOGL_INFO, "stop T203\n");
+ }
+ /* 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)) {
+ LOGP(DLLAPD, LOGL_INFO, "start T203\n");
+ osmo_timer_schedule(&dl->t203, dl->t203_sec, dl->t203_usec);
+ }
+}
+
+/* L1 -> L2 */
+
+/* Receive a LAPD U (Unnumbered) message from L1 */
+static int lapd_rx_u(struct msgb *msg, struct lapd_msg_ctx *lctx)
+{
+ struct lapd_datalink *dl = lctx->dl;
+ int length = lctx->length;
+ int rc;
+ uint8_t prim, op;
+
+ switch (lctx->s_u) {
+ case LAPD_U_SABM:
+ case LAPD_U_SABME:
+ prim = PRIM_DL_EST;
+ op = PRIM_OP_INDICATION;
+
+ LOGP(DLLAPD, LOGL_INFO, "SABM(E) received in state %s\n",
+ lapd_state_names[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) {
+ LOGP(DLLAPD, LOGL_NOTICE, "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) {
+ LOGP(DLLAPD, LOGL_NOTICE, "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_MF_EST:
+ LOGP(DLLAPD, 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. */
+ if (dl->v_send != dl->v_recv) {
+ LOGP(DLLAPD, LOGL_INFO, "Remote reestablish\n");
+ mdl_error(MDL_CAUSE_SABM_MF, lctx);
+ break;
+ }
+ /* Ignore SABM if content differs from first SABM. */
+ if (dl->mode == LAPD_MODE_NETWORK && length
+ && dl->cont_res) {
+#ifdef TEST_CONTENT_RESOLUTION_NETWORK
+ dl->cont_res->data[0] ^= 0x01;
+#endif
+ if (memcmp(dl->cont_res, msg->data, length)) {
+ LOGP(DLLAPD, LOGL_INFO, "Another SABM "
+ "with diffrent 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);
+ /* reset Timer T200 */
+ osmo_timer_del(&dl->t200);
+ 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) {
+ LOGP(DLLAPD, LOGL_NOTICE, "SABM not allowed "
+ "during contention resolution\n");
+ 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);
+ LOGP(DLLAPD, LOGL_NOTICE, "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 */
+ rc = send_dl_l3(prim, op, lctx, msg);
+ }
+ break;
+ case LAPD_U_DM:
+ LOGP(DLLAPD, LOGL_INFO, "DM received in state %s\n",
+ lapd_state_names[dl->state]);
+ /* G.2.2 Wrong value of the C/R bit */
+ if (lctx->cr == dl->cr.rem2loc.cmd) {
+ LOGP(DLLAPD, LOGL_NOTICE, "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) {
+ LOGP(DLLAPD, LOGL_INFO, "unsolicited DM "
+ "response\n");
+ mdl_error(MDL_CAUSE_UNSOL_DM_RESP, lctx);
+ } else {
+ LOGP(DLLAPD, 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;
+ }
+ LOGP(DLLAPD, 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) {
+ LOGP(DLLAPD, 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;
+ LOGP(DLLAPD, LOGL_NOTICE, "Performing "
+ "reestablishment.\n");
+ return lapd_reestablish(dl);
+ }
+ break;
+ case LAPD_STATE_DISC_SENT:
+ /* reset Timer T200 */
+ osmo_timer_del(&dl->t200);
+ /* 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:
+ LOGP(DLLAPD, LOGL_INFO, "unsolicited DM response! "
+ "(discarding)\n");
+ msgb_free(msg);
+ return 0;
+ }
+ /* reset T200 */
+ osmo_timer_del(&dl->t200);
+ /* 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);
+ break;
+ case LAPD_U_UI:
+ LOGP(DLLAPD, LOGL_INFO, "UI received\n");
+ /* G.2.2 Wrong value of the C/R bit */
+ if (lctx->cr == dl->cr.rem2loc.resp) {
+ LOGP(DLLAPD, LOGL_NOTICE, "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) {
+ LOGP(DLLAPD, LOGL_NOTICE, "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
+ */
+ LOGP(DLLAPD, LOGL_INFO, "length=0 (discarding)\n");
+ msgb_free(msg);
+ return 0;
+ }
+ rc = send_dl_l3(PRIM_DL_UNIT_DATA, PRIM_OP_INDICATION, lctx,
+ msg);
+ break;
+ case LAPD_U_DISC:
+ prim = PRIM_DL_REL;
+ op = PRIM_OP_INDICATION;
+
+ LOGP(DLLAPD, LOGL_INFO, "DISC received in state %s\n",
+ lapd_state_names[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) {
+ LOGP(DLLAPD, LOGL_NOTICE, "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.
+ */
+ LOGP(DLLAPD, LOGL_NOTICE,
+ "U frame iwth incorrect parameters ");
+ msgb_free(msg);
+ mdl_error(MDL_CAUSE_UFRM_INC_PARAM, lctx);
+ return -EIO;
+ }
+ switch (dl->state) {
+ case LAPD_STATE_IDLE:
+ LOGP(DLLAPD, 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:
+ LOGP(DLLAPD, LOGL_INFO, "DISC in SABM state\n");
+ /* 5.4.6.2 send DM with F=P */
+ lapd_send_dm(lctx);
+ /* reset Timer T200 */
+ osmo_timer_del(&dl->t200);
+ /* 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:
+ LOGP(DLLAPD, LOGL_INFO, "DISC in est state\n");
+ break;
+ case LAPD_STATE_DISC_SENT:
+ LOGP(DLLAPD, 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);
+ /* reset Timer T200 */
+ osmo_timer_del(&dl->t200);
+ /* 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);
+ break;
+ case LAPD_U_UA:
+ LOGP(DLLAPD, LOGL_INFO, "UA received in state %s\n",
+ lapd_state_names[dl->state]);
+ /* G.2.2 Wrong value of the C/R bit */
+ if (lctx->cr == dl->cr.rem2loc.cmd) {
+ LOGP(DLLAPD, LOGL_NOTICE, "UA indicates command "
+ "error\n");