LAPDm: Add support for RTS based polling
The lower layer must set the 'POLLING_ONLY' flag and provide frame
number when polling a frame. If T200 is pending, it is started with a
timeout frame number in advance to given frame number.
The lower layer must call lapdm_t200_fn() after a frame has been
received or if a frame has not been received. Also it must be called
after a TCH frame has been received. LAPDm uses this to check the T200
timeout condition.
A new function is used to set the frame number based timeout values.
Related: OS#4074
Change-Id: I6ebe83f829d7751ea9de1d90eb478c7a628db64c
diff --git a/TODO-RELEASE b/TODO-RELEASE
index 1d56d45..226450b 100644
--- a/TODO-RELEASE
+++ b/TODO-RELEASE
@@ -10,3 +10,4 @@
core ADD osmo_sock_multiaddr_{add,del}_local_addr()
core ADD gsmtap_inst_fd2() core, DEPRECATE gsmtap_inst_fd()
isdn ABI change add states and flags for external T200 handling
+gsm ABI change add T200 timer states to lapdm_datalink
diff --git a/include/osmocom/gsm/lapdm.h b/include/osmocom/gsm/lapdm.h
index 1a39fca..db66680 100644
--- a/include/osmocom/gsm/lapdm.h
+++ b/include/osmocom/gsm/lapdm.h
@@ -33,6 +33,9 @@
struct lapdm_msg_ctx mctx; /*!< context of established connection */
struct lapdm_entity *entity; /*!< LAPDm entity we are part of */
+
+ uint32_t t200_fn; /*!< T200 timer in frames */
+ uint32_t t200_timeout; /*!< T200 timeout frame number */
};
/*! LAPDm datalink SAPIs */
@@ -119,6 +122,11 @@
void lapdm_entity_set_flags(struct lapdm_entity *le, unsigned int flags);
void lapdm_channel_set_flags(struct lapdm_channel *lc, unsigned int flags);
+void lapdm_entity_set_t200_fn(struct lapdm_entity *le, const uint32_t *t200_fn);
+void lapdm_channel_set_t200_fn(struct lapdm_channel *lc, const uint32_t *t200_fn_dcch, const uint32_t *t200_fn_acch);
+
int lapdm_phsap_dequeue_prim(struct lapdm_entity *le, struct osmo_phsap_prim *pp);
+int lapdm_phsap_dequeue_prim_fn(struct lapdm_entity *le, struct osmo_phsap_prim *pp, uint32_t fn);
+void lapdm_t200_fn(struct lapdm_entity *le, uint32_t fn);
/*! @} */
diff --git a/src/gsm/lapdm.c b/src/gsm/lapdm.c
index 43f5662..d609317 100644
--- a/src/gsm/lapdm.c
+++ b/src/gsm/lapdm.c
@@ -27,6 +27,7 @@
#include <stdio.h>
#include <stdint.h>
+#include <inttypes.h>
#include <string.h>
#include <errno.h>
@@ -196,9 +197,9 @@
char name[256];
if (name_pfx) {
snprintf(name, sizeof(name), "%s[%s]", name_pfx, i == 0 ? "0" : "3");
- lapdm_dl_init(&le->datalink[i], le, t200_ms[i], n200, name);
+ lapdm_dl_init(&le->datalink[i], le, (t200_ms) ? t200_ms[i] : 0, n200, name);
} else
- lapdm_dl_init(&le->datalink[i], le, t200_ms[i], n200, NULL);
+ lapdm_dl_init(&le->datalink[i], le, (t200_ms) ? t200_ms[i] : 0, n200, NULL);
}
lapdm_entity_set_mode(le, mode);
@@ -358,6 +359,18 @@
/* if there is a pending message, queue it */
if (le->tx_pending || le->flags & LAPDM_ENT_F_POLLING_ONLY) {
+ struct msgb *old_msg;
+
+ /* In 'Polling only' mode there can be only one message. */
+ if (le->flags & LAPDM_ENT_F_POLLING_ONLY) {
+ /* Overwrite existing message by removing it first. */
+ if ((old_msg = msgb_dequeue(&dl->dl.tx_queue))) {
+ msgb_free(old_msg);
+ /* Reset V(S) to V(A), because there is no outstanding message now. */
+ dl->dl.v_send = dl->dl.v_ack;
+ }
+ }
+
*msgb_push(msg, 1) = pad;
*msgb_push(msg, 1) = link_id;
*msgb_push(msg, 1) = chan_nr;
@@ -377,21 +390,55 @@
return le->l1_prim_cb(&pp.oph, le->l1_ctx);
}
+/* Get transmit frame from queue, if any. In polling mode, indicate RTS to LAPD and start T200, if pending. */
+static struct msgb *tx_dequeue_msgb(struct lapdm_datalink *dl, uint32_t fn)
+{
+ struct msgb *msg;
+
+ /* Call RTS function of LAPD, to poll next frame. */
+ if (dl->entity->flags & LAPDM_ENT_F_POLLING_ONLY) {
+ struct lapd_msg_ctx lctx;
+ int rc;
+
+ /* Poll next frame. */
+ lctx.dl = &dl->dl;
+ rc = lapd_ph_rts_ind(&lctx);
+
+ /* If T200 has been started, calculate timeout FN. */
+ if (rc == 1) {
+ /* Set T200 in advance. */
+ dl->t200_timeout = fn;
+ ADD_MODULO(dl->t200_timeout, dl->t200_fn, GSM_MAX_FN);
+
+ LOGDL(&dl->dl, LOGL_INFO,
+ "T200 running from FN %"PRIu32" to FN %"PRIu32" (%"PRIu32" frames).\n",
+ fn, dl->t200_timeout, dl->t200_fn);
+ }
+ }
+
+ /* If there is no frame from LAPD, send UI frame, if any. */
+ msg = msgb_dequeue(&dl->dl.tx_queue);
+ if (msg)
+ LOGDL(&dl->dl, LOGL_INFO, "Sending frame from TX queue. (FN %"PRIu32")\n", fn);
+ return msg;
+}
+
/* Dequeue a Downlink message for DCCH (dedicated channel) */
-static struct msgb *tx_dequeue_dcch_msgb(struct lapdm_entity *le)
+static struct msgb *tx_dequeue_dcch_msgb(struct lapdm_entity *le, uint32_t fn)
{
struct msgb *msg;
/* SAPI=0 always has higher priority than SAPI=3 */
- msg = msgb_dequeue(&le->datalink[DL_SAPI0].dl.tx_queue);
- if (msg == NULL) /* no SAPI=0 messages, dequeue SAPI=3 (if any) */
- msg = msgb_dequeue(&le->datalink[DL_SAPI3].dl.tx_queue);
+ msg = tx_dequeue_msgb(&le->datalink[DL_SAPI0], fn);
+ if (msg == NULL) { /* no SAPI=0 messages, dequeue SAPI=3 (if any) */
+ msg = tx_dequeue_msgb(&le->datalink[DL_SAPI3], fn);
+ }
return msg;
}
/* Dequeue a Downlink message for ACCH (associated channel) */
-static struct msgb *tx_dequeue_acch_msgb(struct lapdm_entity *le)
+static struct msgb *tx_dequeue_acch_msgb(struct lapdm_entity *le, uint32_t fn)
{
struct lapdm_datalink *dl;
int last = le->last_tx_dequeue;
@@ -403,7 +450,7 @@
/* next */
i = (i + 1) % n;
dl = &le->datalink[i];
- if ((msg = msgb_dequeue(&dl->dl.tx_queue)))
+ if ((msg = tx_dequeue_msgb(dl, fn)))
break;
} while (i != last);
@@ -417,7 +464,7 @@
/*! dequeue a msg that's pending transmission via L1 and wrap it into
* a osmo_phsap_prim */
-int lapdm_phsap_dequeue_prim(struct lapdm_entity *le, struct osmo_phsap_prim *pp)
+int lapdm_phsap_dequeue_prim_fn(struct lapdm_entity *le, struct osmo_phsap_prim *pp, uint32_t fn)
{
struct msgb *msg;
uint8_t pad;
@@ -425,9 +472,9 @@
/* Dequeue depending on channel type: DCCH or ACCH.
* See 3GPP TS 44.005, section 4.2.2 "Priority". */
if (le == &le->lapdm_ch->lapdm_dcch)
- msg = tx_dequeue_dcch_msgb(le);
+ msg = tx_dequeue_dcch_msgb(le, fn);
else
- msg = tx_dequeue_acch_msgb(le);
+ msg = tx_dequeue_acch_msgb(le, fn);
if (!msg)
return -ENODEV;
@@ -449,6 +496,57 @@
return 0;
}
+static void lapdm_t200_fn_dl(struct lapdm_datalink *dl, uint32_t fn)
+{
+ uint32_t diff;
+
+ OSMO_ASSERT((dl->dl.lapd_flags & LAPD_F_RTS));
+
+ /* If T200 is running, check if it has fired. */
+ if (dl->dl.t200_rts != LAPD_T200_RTS_RUNNING)
+ return;
+
+ /* Calculate how many frames fn is behind t200_timeout.
+ * If it is negative (>= GSM_MAX_FN / 2), we have not reached t200_timeout yet.
+ * If it is 0 or positive, we reached it or we are a bit too late, which is not a problem.
+ */
+ diff = fn;
+ ADD_MODULO(diff, GSM_MAX_FN - dl->t200_timeout, GSM_MAX_FN);
+ if (diff >= GSM_MAX_FN / 2)
+ return;
+
+ LOGDL(&dl->dl, LOGL_INFO, "T200 timeout at FN %"PRIu32", detected at FN %"PRIu32".\n", dl->t200_timeout, fn);
+
+ lapd_t200_timeout(&dl->dl);
+}
+
+/*! Get receive frame number from L1. It is used to check the T200 timeout.
+ * This function is used if LAPD is in RTS mode only. (Applies if the LAPDM_ENT_F_POLLING_ONLY flag is set.)
+ * This function must be called for every valid or invalid data frame received.
+ * The frame number fn must be the frame number of the first burst of a data frame.
+ * This function must be called after the frame is delivered to layer 2.
+ * In case of TCH, this this function must be called for every speech frame received, meaning that there was no valid
+ * data frame. */
+void lapdm_t200_fn(struct lapdm_entity *le, uint32_t fn)
+{
+ unsigned int i;
+
+ if (!(le->flags & LAPDM_ENT_F_POLLING_ONLY)) {
+ LOGP(DLLAPD, LOGL_ERROR, "Function call not allowed on timer based T200.\n");
+ return;
+ }
+
+ for (i = 0; i < ARRAY_SIZE(le->datalink); i++)
+ lapdm_t200_fn_dl(&le->datalink[i], fn);
+}
+
+/*! dequeue a msg that's pending transmission via L1 and wrap it into
+ * a osmo_phsap_prim */
+int lapdm_phsap_dequeue_prim(struct lapdm_entity *le, struct osmo_phsap_prim *pp)
+{
+ return lapdm_phsap_dequeue_prim_fn(le, pp, 0);
+}
+
/* get next frame from the tx queue. because the ms has multiple datalinks,
* each datalink's queue is read round-robin.
*/
@@ -853,6 +951,7 @@
return -EINVAL;
}
/* send to LAPD */
+ LOGDL(lctx.dl, LOGL_DEBUG, "Frame received at FN %"PRIu32".\n", fn);
rc = lapd_ph_data_ind(msg, &lctx);
break;
case LAPDm_FMT_Bter:
@@ -1494,7 +1593,20 @@
/*! Set the flags of a LAPDm entity */
void lapdm_entity_set_flags(struct lapdm_entity *le, unsigned int flags)
{
+ unsigned int dl_flags = 0;
+ struct lapdm_datalink *dl;
+ int i;
+
le->flags = flags;
+
+ /* Set flags at LAPD. */
+ if (le->flags & LAPDM_ENT_F_POLLING_ONLY)
+ dl_flags |= LAPD_F_RTS;
+
+ for (i = 0; i < ARRAY_SIZE(le->datalink); i++) {
+ dl = &le->datalink[i];
+ lapd_dl_set_flags(&dl->dl, dl_flags);
+ }
}
/*! Set the flags of all LAPDm entities in a LAPDm channel */
@@ -1504,4 +1616,25 @@
lapdm_entity_set_flags(&lc->lapdm_acch, flags);
}
+/*! Set the T200 FN timer of a LAPDm entity
+ * \param[in] \ref lapdm_entity
+ * \param[in] t200_fn Array of T200 timeout in frame numbers for all SAPIs (0, 3) */
+void lapdm_entity_set_t200_fn(struct lapdm_entity *le, const uint32_t *t200_fn)
+{
+ unsigned int i;
+
+ for (i = 0; i < ARRAY_SIZE(le->datalink); i++)
+ le->datalink[i].t200_fn = t200_fn[i];
+}
+
+/*! Set the T200 FN timer of all LAPDm entities in a LAPDm channel
+ * \param[in] \ref lapdm_channel
+ * \param[in] t200_fn_dcch Array of T200 timeout in frame numbers for all SAPIs (0, 3) on SDCCH/FACCH
+ * \param[in] t200_fn_acch Array of T200 timeout in frame numbers for all SAPIs (0, 3) on SACCH */
+void lapdm_channel_set_t200_fn(struct lapdm_channel *lc, const uint32_t *t200_fn_dcch, const uint32_t *t200_fn_acch)
+{
+ lapdm_entity_set_t200_fn(&lc->lapdm_dcch, t200_fn_dcch);
+ lapdm_entity_set_t200_fn(&lc->lapdm_acch, t200_fn_acch);
+}
+
/*! @} */
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 056d320..6bb3b4b 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -587,7 +587,11 @@
lapdm_entity_reset;
lapdm_entity_set_flags;
lapdm_entity_set_mode;
+lapdm_entity_set_t200_fn;
+lapdm_channel_set_t200_fn;
lapdm_phsap_dequeue_prim;
+lapdm_phsap_dequeue_prim_fn;
+lapdm_t200_fn;
lapdm_phsap_up;
lapdm_rslms_recvmsg;