gb: Fix gprs_ns_rx_reset to not create NS-VC duplicates

Under special circumstances (see below) receiving a NS-RESET leads to
duplicated NS-VC entries.

This happens when the source port of a NS-VC changes to a new one
that has already been used by another NS-VC.

This patch changes gprs_ns_rx_reset() to check for this case and to
use the existing NS-VC object. The NS-VC object that was associated
with the source address before is detached from this source but kept
in the NS-VC list so that it can be reattached when a correspondent
NS-RESET is received later on. Meanwhile it will have a cleared link
layer address which will not match a real link info.

A new counter NS_CTR_REPLACED is incremented each time when the NS-VC
object is replacing another one. A new signal S_NS_REPLACED is added
which gets dispatched in this case, too.

Another new counter NS_CTR_NSEI_CHG is incremented each time when the
NSEI of a NS-VC object (with fixed NSVCI) changes.

Ticket: OW#874
Sponsored-by: On-Waves ehf

1 files changed, 3 insertions, 0 deletions

diff --git a/include/osmocom/gprs/gprs_ns.h b/include/osmocom/gprs/gprs_ns.h
index 7b0ec92d..b28c58d6 100644
--- a/include/osmocom/gprs/gprs_ns.h
+++ b/include/osmocom/gprs/gprs_ns.h
@@ -119,6 +119,7 @@ struct gprs_nsvc {
 
 	unsigned int remote_end_is_sgsn:1;
 	unsigned int persistent:1;
+	unsigned int nsvci_is_valid:1;
 
 	struct rate_ctr_group *ctrg;
 
@@ -197,10 +198,12 @@ enum signal_ns {
 	S_NS_BLOCK,
 	S_NS_UNBLOCK,
 	S_NS_ALIVE_EXP,	/* Tns-alive expired more than N times */
+	S_NS_REPLACED, /* nsvc object is replaced (sets old_nsvc) */
 };
 
 struct ns_signal_data {
 	struct gprs_nsvc *nsvc;
+	struct gprs_nsvc *old_nsvc;
 	uint8_t cause;
 };