[PATCH 7/7] gb: Fix gprs_ns_rx_reset to not create NS-VC duplicates

[Jacob Erlbeck]

Under special circumstances receiving a NS-RESET leads to duplicated
NS-VC entries. This patch changes gprs_ns_rx_reset() to check for
this case and to eventually delete the old entry.

This happens when the source port of a NS-VC changes to a new one
that has already been used by another NS-VC.
---
 include/osmocom/gprs/gprs_ns.h |    3 +++
 src/gb/gprs_ns.c               |   45 +++++++++++++++++++++++++++++++---------
 tests/gb/gprs_ns_test.ok       |    2 --
 3 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/include/osmocom/gprs/gprs_ns.h b/include/osmocom/gprs/gprs_ns.h
index c709312..562894a 100644
--- a/include/osmocom/gprs/gprs_ns.h
+++ b/include/osmocom/gprs/gprs_ns.h
@@ -117,8 +117,11 @@ struct gprs_nsvc {
 	enum nsvc_timer_mode timer_mode;
 	int alive_retries;
 
+	int dup_deletion_ctr;
+
 	unsigned int remote_end_is_sgsn:1;
 	unsigned int persistent:1;
+	unsigned int nsvci_is_valid:1;
 
 	struct rate_ctr_group *ctrg;
 
diff --git a/src/gb/gprs_ns.c b/src/gb/gprs_ns.c
index 4414bd5..8bd1df2 100644
--- a/src/gb/gprs_ns.c
+++ b/src/gb/gprs_ns.c
@@ -83,6 +83,8 @@
 
 #include "common_vty.h"
 
+const char *gprs_ns_format_peer(struct gprs_nsvc *nsvc);
+
 static const struct tlv_definition ns_att_tlvdef = {
 	.def = {
 		[NS_IE_CAUSE]	= { TLV_TYPE_TvLV, 0 },
@@ -651,8 +653,8 @@ static int gprs_ns_rx_reset(struct gprs_nsvc *nsvc, struct msgb *msg)
 {
 	struct gprs_ns_hdr *nsh = (struct gprs_ns_hdr *) msg->l2h;
 	struct tlv_parsed tp;
-	uint8_t *cause;
-	uint16_t *nsvci, *nsei;
+	uint8_t cause;
+	uint16_t nsvci, nsei;
 	int rc;
 
 	rc = tlv_parse(&tp, &ns_att_tlvdef, nsh->data,
@@ -671,22 +673,45 @@ static int gprs_ns_rx_reset(struct gprs_nsvc *nsvc, struct msgb *msg)
 		return -EINVAL;
 	}
 
-	cause = (uint8_t *) TLVP_VAL(&tp, NS_IE_CAUSE);
-	nsvci = (uint16_t *) TLVP_VAL(&tp, NS_IE_VCI);
-	nsei = (uint16_t *) TLVP_VAL(&tp, NS_IE_NSEI);
+	cause = *(uint8_t  *) TLVP_VAL(&tp, NS_IE_CAUSE);
+	nsvci = ntohs(*(uint16_t *) TLVP_VAL(&tp, NS_IE_VCI));
+	nsei  = ntohs(*(uint16_t *) TLVP_VAL(&tp, NS_IE_NSEI));
+
+	LOGP(DNS, LOGL_INFO, "NSVCI=%u%s Rx NS RESET (NSEI=%u, NSVCI=%u, cause=%s)\n",
+	     nsvc->nsvci, nsvc->nsvci_is_valid ? "" : "(invalid)",
+	     nsei, nsvci, gprs_ns_cause_str(cause));
 
-	LOGP(DNS, LOGL_INFO, "NSEI=%u Rx NS RESET (NSVCI=%u, cause=%s)\n",
-		nsvc->nsvci, nsvc->nsei, gprs_ns_cause_str(*cause));
+	if (nsvc->nsvci_is_valid && nsvc->nsvci != nsvci) {
+		/* NS-VCI has changed */
+		struct gprs_nsvc *other_nsvc;
+		other_nsvc = gprs_nsvc_by_nsvci(nsvc->nsi, nsvci);
+
+		if (other_nsvc) {
+			/* The NS-VCI is already used by this NS-VC */
+
+			char *old_peer = strdup(gprs_ns_format_peer(other_nsvc));
+			LOGP(DNS, LOGL_INFO,
+			     "NS-VC changed link (NSVCI=%u) from %s to %s\n",
+			     nsvci, old_peer, gprs_ns_format_peer(nsvc));
+			free(old_peer);
+
+			nsvc->dup_deletion_ctr = 1 + other_nsvc->dup_deletion_ctr;
+
+			/* Delete the 'old' object */
+			gprs_nsvc_delete(other_nsvc);
+		}
+	}
 
 	/* Mark NS-VC as blocked and alive */
 	nsvc->state = NSE_S_BLOCKED | NSE_S_ALIVE;
 
-	nsvc->nsei = ntohs(*nsei);
-	nsvc->nsvci = ntohs(*nsvci);
+	nsvc->nsei  = nsei;
+	nsvc->nsvci = nsvci;
+	nsvc->nsvci_is_valid = 1;
 
 	/* inform interested parties about the fact that this NSVC
 	 * has received RESET */
-	ns_osmo_signal_dispatch(nsvc, S_NS_RESET, *cause);
+	ns_osmo_signal_dispatch(nsvc, S_NS_RESET, cause);
 
 	rc = gprs_ns_tx_reset_ack(nsvc);
 
diff --git a/tests/gb/gprs_ns_test.ok b/tests/gb/gprs_ns_test.ok
index 578b905..7416f15 100644
--- a/tests/gb/gprs_ns_test.ok
+++ b/tests/gb/gprs_ns_test.ok
@@ -102,7 +102,6 @@ result (RESET) = 9
 
 Current NS-VCIs:
     VCI 0x1122, NSEI 0x1122, peer 0x01020304:3333
-    VCI 0x1122, NSEI 0x3344, peer 0x01020304:4444
 
 --- Peer port 4444, RESET, NSEI is changed back ---
 
@@ -118,7 +117,6 @@ RESPONSE, msg length 1
 result (RESET) = 9
 
 Current NS-VCIs:
-    VCI 0x1122, NSEI 0x1122, peer 0x01020304:3333
     VCI 0x1122, NSEI 0x1122, peer 0x01020304:4444
 
 ===== NS protocol test END
-- 
1.7.9.5