ctr: Count number of dropped messages

In case of back pressure we can not send messages quick enough
and will drop messages. Add a counter so we can count how often
this happened per link/linkset. The SCTP M2UA code is not changed
as we don't have a link in the hands and adding it is too risky
without tests (not all M2UA have a link index so some might not
have a link).

include/counter.h

@@ -29,6 +29,7 @@ enum {
 	MTP_LSET_SCCP_IN_MSG,
 	MTP_LSET_IUSP_IN_MSG,
 	MTP_LSET_TOTA_OUT_MSG,
+	MTP_LSET_TOTA_DRP_MSG,
 	MTP_LSET_SCCP_OUT_MSG,
 	MTP_LSET_ISUP_OUT_MSG,
 };
@@ -37,6 +38,7 @@ enum {
 	MTP_LNK_IN,
 	MTP_LNK_OUT,
 	MTP_LNK_ERROR,
+	MTP_LNK_DRP,
 	MTP_LNK_SLTM_TOUT,
 };
 

src/counter.c

@@ -31,12 +31,14 @@ static const struct rate_ctr_desc mtp_lset_cfg_description[] = {
 	[MTP_LSET_TOTA_OUT_MSG]	= { "total.out",      "Total messages out "},
 	[MTP_LSET_SCCP_OUT_MSG]	= { "sccp.out",       "SCCP messages out  "},
 	[MTP_LSET_ISUP_OUT_MSG]	= { "isup.out",       "ISUP messages out  "},
+	[MTP_LSET_TOTA_DRP_MSG] = { "total.dropped",  "Total dropped msgs "},
 };
 
 static const struct rate_ctr_desc mtp_link_cfg_description[] = {
 	[MTP_LNK_IN]		= { "total.in",       "Messages in        "},
 	[MTP_LNK_OUT]		= { "total.out",      "Messages out       "},
 	[MTP_LNK_ERROR]		= { "total.error",    "Errors occured     "},
+	[MTP_LNK_DRP]		= { "total.dropped",  "Messages dropped   "},
 	[MTP_LNK_SLTM_TOUT]	= { "sltm.timeouts",  "SLTM timeouts      "},
 };
 

src/link_udp.c

@@ -25,6 +25,7 @@
 #include <mtp_pcap.h>
 #include <snmp_mtp.h>
 #include <cellmgr_debug.h>
+#include <counter.h>
 
 #include <osmocom/core/talloc.h>
 
@@ -216,6 +217,8 @@ static int udp_link_write(struct mtp_link *link, struct msgb *msg)
 	if (osmo_wqueue_enqueue(&ulnk->data->write_queue, msg) != 0) {
 		LOGP(DINP, LOGL_ERROR, "Failed to enqueue msg on link %d/%s of %d/%s.\n",
 		     link->nr, link->name, link->set->nr, link->set->name);
+		rate_ctr_inc(&link->ctrg->ctr[MTP_LNK_DRP]);
+		rate_ctr_inc(&link->set->ctrg->ctr[MTP_LSET_TOTA_DRP_MSG]);
 		msgb_free(msg);
 		return -1;
 	}

src/sctp_m3ua_client.c

@@ -19,6 +19,7 @@
 #include <cellmgr_debug.h>
 #include <string.h>
 #include <bsc_data.h>
+#include <counter.h>
 
 #include <osmocom/sigtran/xua_msg.h>
 #include <osmocom/sigtran/m3ua_types.h>
@@ -129,6 +130,8 @@ static int m3ua_conn_send(struct mtp_m3ua_client_link *link,
 
 	if (osmo_wqueue_enqueue(&link->queue, msg) != 0) {
 		LOGP(DINP, LOGL_ERROR, "Failed to enqueue.\n");
+		rate_ctr_inc(&link->base->ctrg->ctr[MTP_LNK_DRP]);
+		rate_ctr_inc(&link->base->set->ctrg->ctr[MTP_LSET_TOTA_DRP_MSG]);
 		msgb_free(msg);
 		return -1;
 	}