ns: Force a defined state when sending NS RESET

Currently the state is assumed to remain the same while the reset
procedure is active. While this works correctly in general, a single
unexpected BLOCK_ACK or UNBLOCK_ACK can change the state but will not
stop the reset procedure. The leads to repeated RESET messages, where
the corresponding RESET_ACK is ignored. This is a stable state which
can only be left by manual intervention or by reception of a RESET
message from the peer.

This commit changes the RESET timeout handler to set the state to
BLOCKED/RESET when sending the new NS RESET message.

Note that this should ensure a clean restart even if the state has been
screwed up. It does not fix the handling of BLOCK_ACK or UNBLOCK_ACK
in abnormal cases.

Addresses:
 gprs_ns.c:349 NSEI=8895 Tx NS RESET (NSVCI=8895, cause=O&M intervention)
 gprs_ns.c:878 NSVCI=8895 Rx NS RESET ACK (NSEI=8895, NSVCI=8895)
 gprs_ns.c:887 NS RESET ACK Discarding unexpected message for NS-VCI 8895 from SGSN NSEI=8895

Ticket: OW#1551
Sponsored-by: On-Waves ehf

3 files changed, 108 insertions, 0 deletions

diff --git a/src/gb/gprs_ns.c b/src/gb/gprs_ns.c
index aa43bb8b..a29c9464 100644
--- a/src/gb/gprs_ns.c
+++ b/src/gb/gprs_ns.c
@@ -615,6 +615,12 @@ static void gprs_ns_timer_cb(void *data)
 		break;
 	case NSVC_TIMER_TNS_RESET:
 		rate_ctr_inc(&nsvc->ctrg->ctr[NS_CTR_LOST_RESET]);
+		if (!(nsvc->state & NSE_S_RESET))
+			LOGP(DNS, LOGL_NOTICE,
+				"NSEI=%u Reset timed out but RESET flag is not set\n",
+				nsvc->nsei);
+		/* Mark NS-VC locally as blocked and dead */
+		nsvc->state = NSE_S_BLOCKED | NSE_S_RESET;
 		/* Chapter 7.3: Re-send the RESET */
 		gprs_ns_tx_reset(nsvc, NS_CAUSE_OM_INTERVENTION);
 		/* Re-start Tns-reset timer */
diff --git a/tests/gb/gprs_ns_test.c b/tests/gb/gprs_ns_test.c
index 00b8732e..a742130f 100644
--- a/tests/gb/gprs_ns_test.c
+++ b/tests/gb/gprs_ns_test.c
@@ -710,6 +710,24 @@ static void test_bss_reset_ack()
 	send_ns_reset_ack(nsi, nse[0], 0xf001, 0x1000);
 	gprs_dump_nsi(nsi);
 
+	/* Test crossing RESET and UNBLOCK_ACK */
+
+	printf("---  RESET (BSS -> SGSN) crossing an UNBLOCK_ACK (SGSN -> BSS) ---\n\n");
+
+	setup_ns(nsi, nse[0], 0x1001, 0x1000);
+	nsvc = gprs_nsvc_by_nsvci(nsi, 0x1001);
+	gprs_nsvc_reset(nsvc, NS_CAUSE_OM_INTERVENTION);
+	OSMO_ASSERT(nsvc->state & NSE_S_BLOCKED);
+	OSMO_ASSERT(nsvc->state & NSE_S_RESET);
+	send_ns_unblock_ack(nsi, nse[0]);
+	gprs_dump_nsi(nsi);
+	send_ns_reset_ack(nsi, nse[0], 0x1001, 0x1000);
+	expire_nsvc_timer(nsvc);
+	OSMO_ASSERT(nsvc->state & NSE_S_BLOCKED);
+	OSMO_ASSERT(nsvc->state & NSE_S_RESET);
+	send_ns_reset_ack(nsi, nse[0], 0x1001, 0x1000);
+	gprs_dump_nsi(nsi);
+
 	gprs_ns_destroy(nsi);
 	nsi = NULL;
 }
diff --git a/tests/gb/gprs_ns_test.ok b/tests/gb/gprs_ns_test.ok
index 1e0bf7f8..b0c81e44 100644
--- a/tests/gb/gprs_ns_test.ok
+++ b/tests/gb/gprs_ns_test.ok
@@ -569,6 +569,90 @@ Current NS-VCIs:
          NS-VC replaced other count: 2
          NS-VC changed NSEI count  : 3
 
+---  RESET (BSS -> SGSN) crossing an UNBLOCK_ACK (SGSN -> BSS) ---
+
+Setup NS-VC: remote 0x01020304:2222, NSVCI 0x1001(4097), NSEI 0x1000(4096)
+
+PROCESSING RESET from 0x01020304:2222
+02 00 81 01 01 82 10 01 04 82 10 00 
+
+==> got signal NS_REPLACED: 0x1001/0.0.0.0:0 -> 0xf001/1.2.3.4:2222
+==> got signal NS_RESET, NS-VC 0x1001/1.2.3.4:2222
+MESSAGE to BSS, msg length 9
+03 01 82 10 01 04 82 10 00 
+
+MESSAGE to BSS, msg length 1
+0a 
+
+result (RESET) = 9
+
+PROCESSING ALIVE from 0x01020304:2222
+0a 
+
+MESSAGE to BSS, msg length 1
+0b 
+
+result (ALIVE) = 1
+
+PROCESSING UNBLOCK from 0x01020304:2222
+06 
+
+==> got signal NS_UNBLOCK, NS-VC 0x1001/1.2.3.4:2222
+MESSAGE to BSS, msg length 1
+07 
+
+result (UNBLOCK) = 1
+
+PROCESSING ALIVE_ACK from 0x01020304:2222
+0b 
+
+result (ALIVE_ACK) = 0
+
+MESSAGE to BSS, msg length 12
+02 00 81 01 01 82 10 01 04 82 10 00 
+
+PROCESSING UNBLOCK_ACK from 0x01020304:2222
+07 
+
+==> got signal NS_UNBLOCK, NS-VC 0x1001/1.2.3.4:2222
+result (UNBLOCK_ACK) = 0
+
+Current NS-VCIs:
+    VCI 0xf001, NSEI 0x1000, peer 0x00000000:0, blocked
+         NS-VC Block count         : 1
+         NS-VC replaced other count: 2
+    VCI 0x2001, NSEI 0x2000, peer 0x01020304:1111
+    VCI 0x1001, NSEI 0x1000, peer 0x01020304:2222
+         NS-VC Block count         : 4
+         NS-VC replaced other count: 3
+         NS-VC changed NSEI count  : 4
+
+PROCESSING RESET_ACK from 0x01020304:2222
+03 01 82 10 01 04 82 10 00 
+
+result (RESET_ACK) = 0
+
+MESSAGE to BSS, msg length 12
+02 00 81 01 01 82 10 01 04 82 10 00 
+
+PROCESSING RESET_ACK from 0x01020304:2222
+03 01 82 10 01 04 82 10 00 
+
+MESSAGE to BSS, msg length 1
+0a 
+
+result (RESET_ACK) = 1
+
+Current NS-VCIs:
+    VCI 0xf001, NSEI 0x1000, peer 0x00000000:0, blocked
+         NS-VC Block count         : 1
+         NS-VC replaced other count: 2
+    VCI 0x2001, NSEI 0x2000, peer 0x01020304:1111
+    VCI 0x1001, NSEI 0x1000, peer 0x01020304:2222, blocked
+         NS-VC Block count         : 5
+         NS-VC replaced other count: 3
+         NS-VC changed NSEI count  : 4
+
 Current NS-VCIs:
 
 --- Setup SGSN connection, BSS -> SGSN ---