cellular-infrastructure
/
osmo-bsc
mirror of https://gerrit.osmocom.org/osmo-bsc
9
0
Fork 0
Code Issues Releases Wiki Activity

lchan_fsm: safer 'concluded' flag 

The flag lchan->activate.concluded prevents entering the
lchan_on_fully_established()/lchan_on_activation_failure() more than once. So
far it was checked by callers, instead place in the functions themselves.

There is a potential functional change here, since during lchan_fail(), the
concluded flag was set only after entering lchan_on_activation_failure(). Now
it is already set at the start and prevents multiple re-entry beyond doubt.

This patch is not a result of an actual observed faulty behavior, just from
reading the code and seeing the slight loophole.

Change-Id: I0c906438b05442d66255203eb816453b7193a6d8
This commit is contained in:
Neels Hofmeyr 2018-08-27 22:06:24 +02:00
parent e23e1aeec2
commit 193c1e3ab0
2 changed files with 13 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/osmocom/bsc/gsm_data.h
View File

@ -505,7 +505,10 @@ struct gsm_lchan {
struct {
enum lchan_activate_mode activ_for;
bool activ_ack; /*< true as soon as RSL Chan Activ Ack is received */
bool concluded; /*< true as soon as LCHAN_ST_ESTABLISHED is reached */
/*! This flag ensures that when an lchan activation has succeeded, and we have already
* sent ACKs like Immediate Assignment or BSSMAP Assignment Complete, and if other errors
* occur later, e.g. during release, that we don't send a NACK out of context. */
bool concluded;
bool requires_voice_stream;
bool wait_before_switching_rtp; /*< true = requires LCHAN_EV_READY_TO_SWITCH_RTP */
uint16_t msc_assigned_cic;

16
src/osmo-bsc/lchan_fsm.c
View File

@ -88,6 +88,10 @@ static void _lchan_on_activation_failure(struct gsm_lchan *lchan, enum lchan_act
struct gsm_subscriber_connection *for_conn,
const char *file, int line)
{
if (lchan->activate.concluded)
return;
lchan->activate.concluded = true;
switch (activ_for) {
case FOR_MS_CHANNEL_REQUEST:
@ -135,6 +139,10 @@ static void _lchan_on_activation_failure(struct gsm_lchan *lchan, enum lchan_act
static void lchan_on_fully_established(struct gsm_lchan *lchan)
{
if (lchan->activate.concluded)
return;
lchan->activate.concluded = true;
switch (lchan->activate.activ_for) {
case FOR_MS_CHANNEL_REQUEST:
/* No signalling to do here, MS is free to use the channel, and should go on to connect
@ -222,9 +230,7 @@ struct state_timeout lchan_fsm_timeouts[32] = {
lchan_set_last_error(_lchan, "lchan %s in state %s: " fmt, \
_lchan->activate.concluded ? "failure" : "allocation failed", \
osmo_fsm_state_name(fsm, state_was), ## args); \
if (!_lchan->activate.concluded) \
lchan_on_activation_failure(_lchan, _lchan->activate.activ_for, _lchan->conn); \
_lchan->activate.concluded = true; \
lchan_on_activation_failure(_lchan, _lchan->activate.activ_for, _lchan->conn); \
if (fi->state != state_chg) \
lchan_fsm_state_chg(state_chg); \
else \
@ -751,10 +757,6 @@ static void lchan_fsm_established_onenter(struct osmo_fsm_inst *fi, uint32_t pre
return;
}
/* This flag ensures that when an lchan activation has succeeded, and we have already sent ACKs
* like Immediate Assignment or BSSMAP Assignment Complete, and if then, way later, some other
* error occurs, e.g. during release, that we don't send a NACK out of context. */
lchan->activate.concluded = true;
lchan_on_fully_established(lchan);
}