Change in libosmocore[master]: ns2: Don't queie Q.933 LMI messages; only store most recent ones

[laforge]

laforge has uploaded this change for review. ( https://gerrit.osmocom.org/c/libosmocore/+/22637 )


Change subject: ns2: Don't queie Q.933 LMI messages; only store most recent ones
......................................................................

ns2: Don't queie Q.933 LMI messages; only store most recent ones

There's not really any point in storing multiple LMI messages,
and then transmitting them in inverse order, as the existing code
does.  Instead, we shall store only the last (failed) LMI message
and try to transmit that at highest priority, before any NS messages
in the actual queue.

Change-Id: I5407a76a34d7e687966fe1a915febf3a87256593
---
M src/gb/gprs_ns2_fr.c
1 file changed, 18 insertions(+), 3 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/libosmocore refs/changes/37/22637/1

diff --git a/src/gb/gprs_ns2_fr.c b/src/gb/gprs_ns2_fr.c
index fc6a5c4..24cc312 100644
--- a/src/gb/gprs_ns2_fr.c
+++ b/src/gb/gprs_ns2_fr.c
@@ -105,7 +105,9 @@
 	struct {
 		/* file-descriptor for AF_PACKET socket */
 		struct osmo_fd ofd;
-		/* list of msgb (backlog) */
+		/* LMI bucket (we only store the last LMI message, no need to queue */
+		struct msgb *lmi_msg;
+		/* list of NS msgb (backlog) */
 		struct llist_head list;
 		/* timer to trigger next attempt of AF_PACKET write */
 		struct osmo_timer_list timer;
@@ -173,6 +175,7 @@
 	llist_for_each_entry_safe(msg, msg2, &priv->backlog.list, list) {
 		msgb_free(msg);
 	}
+	msgb_free(priv->backlog.lmi_msg);
 
 	osmo_fr_link_free(priv->link);
 	osmo_fd_close(&priv->backlog.ofd);
@@ -357,6 +360,7 @@
 /* enqueue to backlog (LMI, signaling) or drop (userdata msg) */
 static int backlog_enqueue_or_free(struct gprs_ns2_vc_bind *bind, struct msgb *msg)
 {
+	struct priv_bind *priv = bind->priv;
 	uint8_t dlci = msg->data[0];
 	uint8_t ns_pdu_type;
 	uint16_t bvci;
@@ -367,8 +371,9 @@
 	/* we want to enqueue only Q.933 LMI traffic or NS signaling; NOT user traffic */
 	switch (dlci) {
 	case LMI_Q933A_DLCI:
-		/* enqueue Q.933 LMI at head of queue */
-		enqueue_at_head(bind, msg);
+		/* always store only the last LMI message in the lmi_msg bucket */
+		msgb_free(priv->backlog.lmi_msg);
+		priv->backlog.lmi_msg = msg;
 		return 0;
 	default:
 		if (msgb_length(msg) < 3)
@@ -405,6 +410,15 @@
 	struct priv_bind *priv = bind->priv;
 	int i, rc;
 
+	/* first try to get rid of the LMI message, if any */
+	if (priv->backlog.lmi_msg) {
+		rc = fr_netif_write_one(bind, priv->backlog.lmi_msg);
+		if (rc < 0)
+			goto restart_timer;
+		/* fr_netif_write_one() has just free'd it */
+		priv->backlog.lmi_msg = NULL;
+	}
+
 	/* attempt to send up to 10 messages in every timer */
 	for (i = 0; i < 10; i++) {
 		struct msgb *msg = msgb_dequeue(&priv->backlog.list);
@@ -420,6 +434,7 @@
 		osmo_stat_item_dec(bind->statg->items[NS2_BIND_STAT_BACKLOG_LEN], 1);
 	}
 
+restart_timer:
 	/* re-start timer if we still have data in the queue */
 	if (!llist_empty(&priv->backlog.list))
 		osmo_timer_schedule(&priv->backlog.timer, 0, priv->backlog.retry_us);

-- 
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Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-Change-Id: I5407a76a34d7e687966fe1a915febf3a87256593
Gerrit-Change-Number: 22637
Gerrit-PatchSet: 1
Gerrit-Owner: laforge <laforge at osmocom.org>
Gerrit-MessageType: newchange
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