llc: Move storage of timestamps into gprs_llc_queue

Currently the receive and expiry timestamps are prepended to the LLC
msgb before it is passed to gprs_llc_queue::enqueue(). Since this meta
information should not be counted as LLC octets, the gprs_llc_queue
needs to known about this (unless the correction was done in the LLC
layer).

This commit moves the meta information storage code into
gprs_llc_queue.  The meta data is now stored in the control block
(cb) area of the msgb.

Note that the info pointer that is returned from the dequeue method
is only valid if that method returns a (non-NULL) msgb. It must not
be used after that msgb has been modified or freed.

Sponsored-by: On-Waves ehf

3 files changed, 38 insertions, 25 deletions

diff --git a/src/llc.cpp b/src/llc.cpp
index 8930d2c8..53a89356 100644
--- a/src/llc.cpp
+++ b/src/llc.cpp
@@ -104,10 +104,19 @@ void gprs_llc_queue::init()
 	m_avg_queue_delay = 0;
 }
 
-void gprs_llc_queue::enqueue(struct msgb *llc_msg)
+void gprs_llc_queue::enqueue(struct msgb *llc_msg, const MetaInfo *info)
 {
+	static const MetaInfo def_meta = {{0}};
+	MetaInfo *meta_storage;
+
+	osmo_static_assert(sizeof(*info) <= sizeof(llc_msg->cb), info_does_not_fit);
+
 	m_queue_size += 1;
-	m_queue_octets += msgb_length(llc_msg) - 2*sizeof(struct timeval);
+	m_queue_octets += msgb_length(llc_msg);
+
+	meta_storage = (MetaInfo *)&llc_msg->cb[0];
+	*meta_storage = info ? *info : def_meta;
+
 	msgb_enqueue(&m_queue, llc_msg);
 }
 
@@ -127,24 +136,29 @@ void gprs_llc_queue::clear(BTS *bts)
 
 #define ALPHA 0.5f
 
-struct msgb *gprs_llc_queue::dequeue()
+struct msgb *gprs_llc_queue::dequeue(const MetaInfo **info)
 {
 	struct msgb *msg;
 	struct timeval *tv, tv_now, tv_result;
 	uint32_t lifetime;
-
+	const MetaInfo *meta_storage;
 
 	msg = msgb_dequeue(&m_queue);
 	if (!msg)
 		return NULL;
 
+	meta_storage = (MetaInfo *)&msg->cb[0];
+
+	if (info)
+		*info = meta_storage;
+
 	m_queue_size -= 1;
-	m_queue_octets -= msgb_length(msg) - 2*sizeof(struct timeval);
+	m_queue_octets -= msgb_length(msg);
 
 	/* take the second time */
 	gettimeofday(&tv_now, NULL);
 	tv = (struct timeval *)&msg->data[sizeof(*tv)];
-	timersub(&tv_now, tv, &tv_result);
+	timersub(&tv_now, &meta_storage->recv_time, &tv_result);
 
 	lifetime = tv_result.tv_sec*1000 + tv_result.tv_usec/1000;
 	m_avg_queue_delay = m_avg_queue_delay * ALPHA + lifetime * (1-ALPHA);
diff --git a/src/llc.h b/src/llc.h
index 065589db..887e210c 100644
--- a/src/llc.h
+++ b/src/llc.h
@@ -24,6 +24,7 @@ extern "C" {
 
 #include <stdint.h>
 #include <string.h>
+#include <time.h>
 
 #define LLC_MAX_LEN 1543
 
@@ -63,6 +64,11 @@ struct gprs_llc {
  * I store the LLC frames that come from the SGSN.
  */
 struct gprs_llc_queue {
+	struct MetaInfo {
+		struct timeval recv_time;
+		struct timeval expire_time;
+	};
+
 	static void calc_pdu_lifetime(BTS *bts, const uint16_t pdu_delay_csec,
 		struct timeval *tv);
 	static bool is_frame_expired(const struct timeval *now,
@@ -71,8 +77,8 @@ struct gprs_llc_queue {
 
 	void init();
 
-	void enqueue(struct msgb *llc_msg);
-	struct msgb *dequeue();
+	void enqueue(struct msgb *llc_msg, const MetaInfo *info = 0);
+	struct msgb *dequeue(const MetaInfo **info = 0);
 	void clear(BTS *bts);
 	size_t size() const;
 	size_t octets() const;
diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index 68e6fab7..853821ca 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -99,20 +99,15 @@ int gprs_rlcmac_dl_tbf::append_data(const uint8_t ms_class,
 				const uint8_t *data, const uint16_t len)
 {
 	LOGP(DRLCMAC, LOGL_INFO, "%s append\n", tbf_name(this));
-	/* TODO: put this path into an llc_enqueue method */
-	/* the TBF exists, so we must write it in the queue
-	 * we prepend lifetime in front of PDU */
-	struct timeval *tv;
-	struct msgb *llc_msg = msgb_alloc(len + sizeof(*tv) * 2,
-		"llc_pdu_queue");
+	gprs_llc_queue::MetaInfo info;
+	struct msgb *llc_msg = msgb_alloc(len, "llc_pdu_queue");
 	if (!llc_msg)
 		return -ENOMEM;
-	tv = (struct timeval *)msgb_put(llc_msg, sizeof(*tv));
-	gprs_llc_queue::calc_pdu_lifetime(bts, pdu_delay_csec, tv);
-	tv = (struct timeval *)msgb_put(llc_msg, sizeof(*tv));
-	gettimeofday(tv, NULL);
+
+	gprs_llc_queue::calc_pdu_lifetime(bts, pdu_delay_csec, &info.expire_time);
+	gettimeofday(&info.recv_time, NULL);
 	memcpy(msgb_put(llc_msg, len), data, len);
-	llc_queue()->enqueue(llc_msg);
+	llc_queue()->enqueue(llc_msg, &info);
 	tbf_update_ms_class(this, ms_class);
 	start_llc_timer();
 
@@ -238,11 +233,11 @@ int gprs_rlcmac_dl_tbf::handle(struct gprs_rlcmac_bts *bts,
 struct msgb *gprs_rlcmac_dl_tbf::llc_dequeue(bssgp_bvc_ctx *bctx)
 {
 	struct msgb *msg;
-	struct timeval *tv_recv, *tv_disc;
 	struct timeval tv_now, tv_now2;
 	uint32_t octets = 0, frames = 0;
 	struct timeval hyst_delta = {0, 0};
 	const unsigned keep_small_thresh = 60;
+	const gprs_llc_queue::MetaInfo *info;
 
 	if (bts_data()->llc_discard_csec)
 		csecs_to_timeval(bts_data()->llc_discard_csec, &hyst_delta);
@@ -250,11 +245,9 @@ struct msgb *gprs_rlcmac_dl_tbf::llc_dequeue(bssgp_bvc_ctx *bctx)
 	gettimeofday(&tv_now, NULL);
 	timeradd(&tv_now, &hyst_delta, &tv_now2);
 
-	while ((msg = llc_queue()->dequeue())) {
-		tv_disc = (struct timeval *)msg->data;
-		msgb_pull(msg, sizeof(*tv_disc));
-		tv_recv = (struct timeval *)msg->data;
-		msgb_pull(msg, sizeof(*tv_recv));
+	while ((msg = llc_queue()->dequeue(&info))) {
+		const struct timeval *tv_disc = &info->expire_time;
+		const struct timeval *tv_recv = &info->recv_time;
 
 		gprs_bssgp_update_queue_delay(tv_recv, &tv_now);