nat: We want the remote to respond to our DLCX request

We want to send a TRAP with the MGCP statistics from the NAT and
the connected BSC. The BSC endpoint can be either released because
of a DLCX from the MGCP CallAgent or the SCCP Connection release on
the A-link.

This is why we need to queue the statistics when the deleting the
endpoint on the BSC. The processing is continued once the response
arrives. This code assumes that the response of the DLCX will be sent
by the remote side. The current amount of outstanding responses can be
seen on the VTY. This assumption is based on the fact that the BSC has
already responded to the CRCX and maybe to the MDCX.

The MGCP RFC is bended to prefix the transaction identifier with "nat-"
to easily detect the response and hand it to the handler. This will
then parse the response and generate the TRAP. The current version is
v1. We assume that the transaction space is big enough and we will
not re-assign the transaction identifier too early.

1 files changed, 161 insertions, 7 deletions

diff --git a/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c b/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c
index 480a8f6d1..a29e9d70d 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c
@@ -49,6 +49,7 @@
 #include <openbsc/ipaccess.h>
 #include <openbsc/mgcp.h>
 #include <openbsc/mgcp_internal.h>
+#include <openbsc/control_cmd.h>
 
 #include <osmocom/sccp/sccp.h>
 
@@ -276,14 +277,20 @@ static void bsc_mgcp_send_mdcx(struct bsc_connection *bsc, int port, struct mgcp
 	bsc_write_mgcp(bsc, (uint8_t *) buf, len);
 }
 
-static void bsc_mgcp_send_dlcx(struct bsc_connection *bsc, int endpoint)
+static void bsc_mgcp_send_dlcx(struct bsc_connection *bsc, int endpoint, int trans)
 {
 	char buf[2096];
 	int len;
 
+	/*
+	 * The following is a bit of a spec violation. According to the
+	 * MGCP grammar the transaction id is are upto 9 digits but we
+	 * prefix it with an alpha numeric value so we can easily recognize
+	 * it as a response.
+	 */
 	len = snprintf(buf, sizeof(buf),
-		       "DLCX 26 %x@mgw MGCP 1.0\r\n"
-		       "Z: noanswer\r\n", endpoint);
+		       "DLCX nat-%u %x@mgw MGCP 1.0\r\n",
+			trans, endpoint);
 	if (len < 0) {
 		LOGP(DMGCP, LOGL_ERROR, "snprintf for DLCX failed.\n");
 		return;
@@ -298,18 +305,153 @@ void bsc_mgcp_init(struct sccp_connections *con)
 	con->bsc_endp = -1;
 }
 
+/**
+ * This code will remember the network side of the audio statistics and
+ * once the internal DLCX response arrives this can be combined with the
+ * the BSC side and forwarded as a trap.
+ */
+static void remember_pending_dlcx(struct sccp_connections *con, uint32_t transaction)
+{
+	struct bsc_nat_call_stats *stats;
+	struct bsc_connection *bsc = con->bsc;
+	struct mgcp_endpoint *endp;
+
+	stats = talloc_zero(bsc, struct bsc_nat_call_stats);
+	if (!stats) {
+		LOGP(DNAT, LOGL_NOTICE,
+			"Failed to allocate statistics for endpoint 0x%x\n",
+			con->msc_endp);
+		return;
+	}
+
+	/* take the endpoint here */
+	endp = &bsc->nat->mgcp_cfg->trunk.endpoints[con->msc_endp];
+
+	stats->remote_ref = con->remote_ref;
+	stats->src_ref = con->patched_ref;
+
+	stats->ci = endp->ci;
+	stats->bts_rtp_port = endp->bts_end.rtp_port;
+	stats->bts_addr = endp->bts_end.addr;
+	stats->net_rtp_port = endp->net_end.rtp_port;
+	stats->net_addr = endp->net_end.addr;
+
+	stats->net_ps = endp->net_end.packets;
+	stats->net_os = endp->net_end.octets;
+	stats->bts_pr = endp->bts_end.packets;
+	stats->bts_or = endp->bts_end.octets;
+	mgcp_state_calc_loss(&endp->bts_state, &endp->bts_end,
+				&stats->bts_expected, &stats->bts_loss);
+	stats->bts_jitter = mgcp_state_calc_jitter(&endp->bts_state);
+
+	stats->trans_id = transaction;
+	stats->msc_endpoint = con->msc_endp;
+
+	bsc->pending_dlcx_count += 1;
+	llist_add_tail(&stats->entry, &bsc->pending_dlcx);
+}
+
 void bsc_mgcp_dlcx(struct sccp_connections *con)
 {
 	/* send a DLCX down the stream */
 	if (con->bsc_endp != -1 && con->bsc->_endpoint_status) {
+		LOGP(DNAT, LOGL_NOTICE,
+			"Endpoint 0x%x was still allocated on bsc: %d. Freeing it.\n",
+			con->bsc_endp, con->bsc->cfg->nr);
 		if (con->bsc->_endpoint_status[con->bsc_endp] != 1)
 			LOGP(DNAT, LOGL_ERROR, "Endpoint 0x%x was not in use\n", con->bsc_endp);
+		remember_pending_dlcx(con, con->bsc->next_transaction);
 		con->bsc->_endpoint_status[con->bsc_endp] = 0;
-		bsc_mgcp_send_dlcx(con->bsc, con->bsc_endp);
+		bsc_mgcp_send_dlcx(con->bsc, con->bsc_endp, con->bsc->next_transaction++);
 		bsc_mgcp_free_endpoint(con->bsc->nat, con->msc_endp);
 	}
 
 	bsc_mgcp_init(con);
+
+}
+
+/*
+ * Search for the pending request
+ */
+static void handle_dlcx_response(struct bsc_connection *bsc, struct msgb *msg,
+			int code, const char *transaction)
+{
+	uint32_t trans_id = UINT32_MAX;
+	uint32_t b_ps, b_os, n_pr, n_or, jitter;
+	int loss;
+	struct bsc_nat_call_stats *tmp, *stat = NULL;
+	struct ctrl_cmd *cmd;
+
+	/* parse the transaction identifier */
+	int rc = sscanf(transaction, "nat-%u", &trans_id);
+	if (rc != 1) {
+		LOGP(DNAT, LOGL_ERROR, "Can not parse transaction id: '%s'\n",
+			transaction);
+		return;
+	}
+
+	/* find the answer for the request we made */
+	llist_for_each_entry(tmp, &bsc->pending_dlcx, entry) {
+		if (trans_id != tmp->trans_id)
+			continue;
+
+		stat = tmp;
+		break;
+	}
+
+	if (!stat) {
+		LOGP(DNAT, LOGL_ERROR,
+			"Can not find transaction for: %u\n", trans_id);
+		return;
+	}
+
+	/* attempt to parse the data now */
+	rc = mgcp_parse_stats(msg, &b_ps, &b_os, &n_pr, &n_or, &loss, &jitter);
+	if (rc != 0)
+		LOGP(DNAT, LOGL_ERROR,
+			"Can not parse connection statistics: %d\n", rc);
+
+	/* send a trap now */
+	cmd = ctrl_cmd_create(bsc, CTRL_TYPE_TRAP);
+	if (!cmd) {
+		LOGP(DNAT, LOGL_ERROR,
+			"Creating a ctrl cmd failed.\n");
+		goto free_stat;
+	}
+
+	cmd->id = "0";
+	cmd->variable = "nat.call_stats.v1";
+	cmd->reply = talloc_asprintf(cmd,
+			"bsc_id=%d,mg_ip_addr=%s,mg_port=%d,",
+			bsc->cfg->nr, inet_ntoa(stat->net_addr),
+			stat->net_rtp_port);
+	cmd->reply = talloc_asprintf_append(cmd->reply,
+			"endpoint_ip_addr=%s,endpoint_port=%d,",
+			inet_ntoa(stat->bts_addr),
+			stat->bts_rtp_port);
+	cmd->reply = talloc_asprintf_append(cmd->reply,
+			"nat_pkt_in=%u,nat_pkt_out=%u,"
+			"nat_bytes_in=%u,nat_bytes_out=%u,"
+			"nat_jitter=%u,nat_pkt_lost=%d,",
+			stat->bts_pr, stat->net_ps,
+			stat->bts_or, stat->net_os,
+			stat->bts_jitter, stat->bts_loss);
+	cmd->reply = talloc_asprintf_append(cmd->reply,
+			"bsc_pkt_in=%u,bsc_pkt_out=%u,"
+			"bsc_bytes_in=%u,bsc_bytes_out=%u,"
+			"bsc_jitter=%u,bsc_pkt_lost=%d",
+			n_pr, b_ps,
+			n_or, b_os,
+			jitter, loss);
+
+	/* send it and be done */
+	ctrl_cmd_send_to_all(bsc->nat->ctrl, cmd);
+	talloc_free(cmd);
+
+free_stat:
+	bsc->pending_dlcx_count -= 1;
+	llist_del(&stat->entry);
+	talloc_free(stat);
 }
 
 
@@ -330,7 +472,8 @@ struct sccp_connections *bsc_mgcp_find_con(struct bsc_nat *nat, int endpoint)
 	if (con)
 		return con;
 
-	LOGP(DMGCP, LOGL_ERROR, "Failed to find the connection.\n");
+	LOGP(DMGCP, LOGL_ERROR,
+		"Failed to find the connection for endpoint: 0x%x\n", endpoint);
 	return NULL;
 }
 
@@ -435,7 +578,7 @@ static void free_chan_downstream(struct mgcp_endpoint *endp, struct bsc_endpoint
 				ENDPOINT_NUMBER(endp));
 		} else {
 			if (con->bsc == bsc) {
-				bsc_mgcp_send_dlcx(bsc, con->bsc_endp);
+				bsc_mgcp_send_dlcx(bsc, con->bsc_endp, con->bsc->next_transaction++);
 			} else {
 				LOGP(DMGCP, LOGL_ERROR,
 					"Endpoint belongs to a different BSC\n");
@@ -452,6 +595,9 @@ static void free_chan_downstream(struct mgcp_endpoint *endp, struct bsc_endpoint
  * this transaction and if it belongs to the BSC. Then we will
  * need to patch the content to point to the local network and we
  * need to update the I: that was assigned by the BSS.
+ *
+ * Only responses to CRCX and DLCX should arrive here. The DLCX
+ * needs to be handled specially to combine the two statistics.
  */
 void bsc_mgcp_forward(struct bsc_connection *bsc, struct msgb *msg)
 {
@@ -488,6 +634,11 @@ void bsc_mgcp_forward(struct bsc_connection *bsc, struct msgb *msg)
 		break;
 	}
 
+	if (!bsc_endp && strncmp("nat-", transaction_id, 4) == 0) {
+		handle_dlcx_response(bsc, msg, code, transaction_id);
+		return;
+	}
+
 	if (!bsc_endp) {
 		LOGP(DMGCP, LOGL_ERROR, "Could not find active endpoint: %s for msg: '%s'\n",
 		     transaction_id, (const char *) msg->l2h);
@@ -523,8 +674,11 @@ void bsc_mgcp_forward(struct bsc_connection *bsc, struct msgb *msg)
 
 int bsc_mgcp_parse_response(const char *str, int *code, char transaction[60])
 {
+	int rc;
 	/* we want to parse two strings */
-	return sscanf(str, "%3d %59s\n", code, transaction) != 2;
+	rc = sscanf(str, "%3d %59s\n", code, transaction) != 2;
+	transaction[59] = '\0';
+	return rc;
 }
 
 uint32_t bsc_mgcp_extract_ci(const char *str)