gsm_04_11: Support for implicit CP-ACK in case of multi-SMS
See GSM 04.11 Chapter 5.4 for details. The idea is that when
multi-SMS are mobile originated, it's possible the CP-ACK of
the previous transaction to be lost and the reception of a
new CP-DATA for a new transaction should close previous transaction
"as-if" we had received the CP-ACK ...
Note that testing is hard since it's an exceptional condition that's
hard to create. I tested by temporarly disabling CP-ACK processing
and checked it worked as expected.
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/openbsc/src/gsm_04_11.c b/openbsc/src/gsm_04_11.c
index c3a49f3..7f570b8 100644
--- a/openbsc/src/gsm_04_11.c
+++ b/openbsc/src/gsm_04_11.c
@@ -948,6 +948,33 @@
switch(msg_type) {
case GSM411_MT_CP_DATA:
DEBUGPC(DSMS, "RX SMS CP-DATA\n");
+
+ /* 5.4: For MO, if a CP-DATA is received for a new
+ * transaction, equals reception of an implicit
+ * last CP-ACK for previous transaction */
+ if (trans->sms.cp_state == GSM411_CPS_IDLE) {
+ int i;
+ struct gsm_trans *ptrans;
+
+ /* Scan through all remote initiated transactions */
+ for (i=8; i<15; i++) {
+ if (i == transaction_id)
+ continue;
+
+ ptrans = trans_find_by_id(lchan->subscr,
+ GSM48_PDISC_SMS, i);
+ if (!ptrans)
+ continue;
+
+ DEBUGP(DSMS, "Implicit CP-ACK for trans_id=%x\n", i);
+
+ /* Finish it for good */
+ bsc_del_timer(&ptrans->sms.cp_timer);
+ ptrans->sms.cp_state = GSM411_CPS_IDLE;
+ trans_free(ptrans);
+ }
+ }
+
/* 5.2.3.1.3: MO state exists when SMC has received
* CP-DATA, including sending of the assoc. CP-ACK */
/* 5.2.3.2.4: MT state exists when SMC has received