nat: Rewrite the paging handling.

The current code tries to find _one_ bsc for a paging message
and then continues. The new code will try to find multiple BSCs
for each LAC. This is done in preparation of having two BSCs
handle the same LAC. This code right now is O(m*n) but it will
be worse once paging groups are landed.
The code to test the function was reduced to just test the lac
lookup code as the other part can not be tested in a standalone
setup anymore.

openbsc/include/openbsc/bsc_nat.h

@@ -306,7 +306,7 @@ struct bsc_nat_parsed *bsc_nat_parse(struct msgb *msg);
  */
 int bsc_nat_filter_ipa(int direction, struct msgb *msg, struct bsc_nat_parsed *parsed);
 int bsc_nat_vty_init(struct bsc_nat *nat);
-struct bsc_connection *bsc_nat_find_bsc(struct bsc_nat *nat, struct msgb *msg, int *_lac);
+int bsc_nat_find_paging(struct msgb *msg, const uint8_t **,int *len);
 
 /**
  * Content filtering.

openbsc/src/osmo-bsc_nat/bsc_nat.c

@@ -549,6 +549,50 @@ send_refuse:
 	bsc_write(bsc, refuse, IPAC_PROTO_SCCP);
 }
 
+static void bsc_nat_send_paging(struct bsc_connection *bsc, struct msgb *msg)
+{
+	if (bsc->cfg->forbid_paging) {
+		LOGP(DNAT, LOGL_DEBUG, "Paging forbidden for BTS: %d\n", bsc->cfg->nr);
+		return;
+	}
+
+	bsc_send_data(bsc, msg->l2h, msgb_l2len(msg), IPAC_PROTO_SCCP);
+}
+
+static void bsc_nat_handle_paging(struct bsc_nat *nat, struct msgb *msg)
+{
+	struct bsc_connection *bsc;
+	const uint8_t *paging_start;
+	int paging_length, i;
+
+	if (bsc_nat_find_paging(msg, &paging_start, &paging_length) != 0) {
+		LOGP(DNAT, LOGL_ERROR, "Could not parse paging message.\n");
+		return;
+	}
+
+	/* This is quite expensive now */
+	for (i = 0; i < paging_length; i += 2) {
+		unsigned int _lac = ntohs(*(unsigned int *) &paging_start[i]);
+		unsigned int paged = 0;
+		llist_for_each_entry(bsc, &nat->bsc_connections, list_entry) {
+			if (!bsc->cfg)
+				continue;
+			if (!bsc->authenticated)
+				continue;
+			if (!bsc_config_handles_lac(bsc->cfg, _lac))
+				continue;
+			bsc_nat_send_paging(bsc, msg);
+			paged += 1;
+		}
+
+		/* highlight a possible config issue */
+		if (paged == 0)
+			LOGP(DNAT, LOGL_ERROR, "No BSC for LAC %d/0x%d\n", _lac, _lac);
+
+	}
+}
+
+
 /*
  * Update the auth status. This can be either a CIPHER MODE COMAMND or
  * a CM Serivce Accept. Maybe also LU Accept or such in the future.
@@ -677,16 +721,7 @@ send_to_all:
 	 * message and then send it to the authenticated messages...
 	 */
 	if (parsed->ipa_proto == IPAC_PROTO_SCCP && parsed->gsm_type == BSS_MAP_MSG_PAGING) {
-		int lac;
+		bsc_nat_handle_paging(nat, msg);
-		bsc = bsc_nat_find_bsc(nat, msg, &lac);
-		if (bsc && bsc->cfg->forbid_paging)
-			LOGP(DNAT, LOGL_DEBUG, "Paging forbidden for BTS: %d\n", bsc->cfg->nr);
-		else if (bsc)
-			bsc_send_data(bsc, msg->l2h, msgb_l2len(msg), parsed->ipa_proto);
-		else if (lac != -1)
-			LOGP(DNAT, LOGL_ERROR, "Could not determine BSC for paging on lac: %d/0x%x\n",
-			     lac, lac);
-
 		goto exit;
 	}
 	/* currently send this to every BSC connected */

openbsc/src/osmo-bsc_nat/bsc_nat_utils.c

@@ -208,25 +208,23 @@ void sccp_connection_destroy(struct sccp_connections *conn)
 	talloc_free(conn);
 }
 
-struct bsc_connection *bsc_nat_find_bsc(struct bsc_nat *nat, struct msgb *msg, int *lac_out)
+
+int bsc_nat_find_paging(struct msgb *msg,
+			const uint8_t **out_data, int *out_leng)
 {
-	struct bsc_connection *bsc;
 	int data_length;
 	const uint8_t *data;
 	struct tlv_parsed tp;
-	int i = 0;
-
-	*lac_out = -1;
 
 	if (!msg->l3h || msgb_l3len(msg) < 3) {
 		LOGP(DNAT, LOGL_ERROR, "Paging message is too short.\n");
-		return NULL;
+		return -1;
 	}
 
 	tlv_parse(&tp, gsm0808_att_tlvdef(), msg->l3h + 3, msgb_l3len(msg) - 3, 0, 0);
 	if (!TLVP_PRESENT(&tp, GSM0808_IE_CELL_IDENTIFIER_LIST)) {
 		LOGP(DNAT, LOGL_ERROR, "No CellIdentifier List inside paging msg.\n");
-		return NULL;
+		return -2;
 	}
 
 	data_length = TLVP_LEN(&tp, GSM0808_IE_CELL_IDENTIFIER_LIST);
@@ -234,29 +232,15 @@ struct bsc_connection *bsc_nat_find_bsc(struct bsc_nat *nat, struct msgb *msg, i
 
 	/* No need to try a different BSS */
 	if (data[0] == CELL_IDENT_BSS) {
-		return NULL;
+		return -3;
 	} else if (data[0] != CELL_IDENT_LAC) {
 		LOGP(DNAT, LOGL_ERROR, "Unhandled cell ident discrminator: %d\n", data[0]);
-		return NULL;
+		return -4;
 	}
 
-	/* Currently we only handle one BSC */
+	*out_data = &data[1];
-	for (i = 1; i < data_length - 1; i += 2) {
+	*out_leng = data_length - 1;
-		unsigned int _lac = ntohs(*(unsigned int *) &data[i]);
+	return 0;
-		*lac_out = _lac;
-		llist_for_each_entry(bsc, &nat->bsc_connections, list_entry) {
-			if (!bsc->cfg)
-				continue;
-			if (!bsc->authenticated)
-				continue;
-			if (!bsc_config_handles_lac(bsc->cfg, _lac))
-				continue;
-
-			return bsc;
-		}
-	}
-
-	return NULL;
 }
 
 int bsc_write_mgcp(struct bsc_connection *bsc, const uint8_t *data, unsigned int length)

openbsc/tests/bsc-nat/bsc_nat_test.c

@@ -384,12 +384,9 @@ static void test_contrack()
 
 static void test_paging(void)
 {
-	int lac;
 	struct bsc_nat *nat;
 	struct bsc_connection *con;
-	struct bsc_nat_parsed *parsed;
 	struct bsc_config *cfg;
-	struct msgb *msg;
 
 	fprintf(stderr, "Testing paging by lac.\n");
 
@@ -400,34 +397,20 @@ static void test_paging(void)
 	bsc_config_add_lac(cfg, 23);
 	con->authenticated = 1;
 	llist_add(&con->list_entry, &nat->bsc_connections);
-	msg = msgb_alloc(4096, "test");
-
-	/* Test completely bad input */
-	copy_to_msg(msg, paging_by_lac_cmd, sizeof(paging_by_lac_cmd));
-	if (bsc_nat_find_bsc(nat, msg, &lac) != 0) {
-		fprintf(stderr, "Should have not found anything.\n");
-		abort();
-	}
 
 	/* Test it by not finding it */
-	copy_to_msg(msg, paging_by_lac_cmd, sizeof(paging_by_lac_cmd));
+	if (bsc_config_handles_lac(cfg, 8213) != 0) {
-	parsed = bsc_nat_parse(msg);
+		fprintf(stderr, "Should not be handled.\n");
-	if (bsc_nat_find_bsc(nat, msg, &lac) != 0) {
-		fprintf(stderr, "Should have not found aynthing.\n");
 		abort();
 	}
-	talloc_free(parsed);
 
 	/* Test by finding it */
 	bsc_config_del_lac(cfg, 23);
 	bsc_config_add_lac(cfg, 8213);
-	copy_to_msg(msg, paging_by_lac_cmd, sizeof(paging_by_lac_cmd));
+	if (bsc_config_handles_lac(cfg, 8213) == 0) {
-	parsed = bsc_nat_parse(msg);
-	if (bsc_nat_find_bsc(nat, msg, &lac) != con) {
 		fprintf(stderr, "Should have found it.\n");
 		abort();
 	}
-	talloc_free(parsed);
 }
 
 static void test_mgcp_allocations(void)