chan_dahdi: Add the chan_dahdi.conf force_restart_unavailable_chans option.

Some telco switches occasionally ignore ISDN RESTART requests.  The fix
for ASTERISK-19608 added an escape clause for B channels in the restarting
state if the telco ignores a RESTART request.  If the telco fails to
acknowledge the RESTART then Asterisk will assume the telco acknowledged
the RESTART on the second call attempt requesting the B channel by the
telco.  The escape clause is good for dealing with RESTART requests in
general but it does cause the next call for the restarting B channel to be
rejected if the telco insists the call must go on that B channel.

chan_dahdi doesn't really need to issue a RESTART request in response to
receiving a cause 44 (Requested channel not available) code.  Sending the
RESTART in such a situation is not required (nor prohibited) by the
standards.  I think chan_dahdi does this for historical reasons to deal
with buggy peers to get channels unstuck in a similar fashion as the
chan_dahdi.conf resetinterval option.

* Add the chan_dahdi.conf force_restart_unavailable_chans compatability
option that when disabled will prevent chan_dahdi from trying to RESTART
the channel in response to a cause 44 code.

ASTERISK-25034 #close
Reported by: Richard Mudgett

Change-Id: Ib8b17a438799920f4a2038826ff99a1884042f65

1 files changed, 2 insertions, 13 deletions

diff --git a/channels/sig_pri.c b/channels/sig_pri.c
index e4ad589c1..c58a3f358 100644
--- a/channels/sig_pri.c
+++ b/channels/sig_pri.c
@@ -133,15 +133,6 @@
  */
 //#define ALWAYS_PICK_CHANNEL	1
 
-/*!
- * Define to force a RESTART on a channel that returns a cause
- * code of PRI_CAUSE_REQUESTED_CHAN_UNAVAIL(44).  If the cause
- * is because of a stuck channel on the peer and the channel is
- * always the next channel we pick for an outgoing call then
- * this can help.
- */
-#define FORCE_RESTART_UNAVAIL_CHANS		1
-
 #if defined(HAVE_PRI_CCSS)
 struct sig_pri_cc_agent_prv {
 	/*! Asterisk span D channel control structure. */
@@ -7158,9 +7149,9 @@ static void *pri_dchannel(void *vpri)
 					pri_hangup(pri->pri, pri->pvts[chanpos]->call, e->hangup.cause);
 					pri->pvts[chanpos]->call = NULL;
 				}
-#if defined(FORCE_RESTART_UNAVAIL_CHANS)
 				if (e->hangup.cause == PRI_CAUSE_REQUESTED_CHAN_UNAVAIL
 					&& pri->sig != SIG_BRI_PTMP && !pri->resetting
+					&& pri->force_restart_unavailable_chans
 					&& pri->pvts[chanpos]->resetting == SIG_PRI_RESET_IDLE) {
 					ast_verb(3,
 						"Span %d: Forcing restart of channel %d/%d since channel reported in use\n",
@@ -7169,7 +7160,6 @@ static void *pri_dchannel(void *vpri)
 					pri->pvts[chanpos]->resetting = SIG_PRI_RESET_ACTIVE;
 					pri_reset(pri->pri, PVT_TO_CHANNEL(pri->pvts[chanpos]));
 				}
-#endif	/* defined(FORCE_RESTART_UNAVAIL_CHANS) */
 				if (e->hangup.aoc_units > -1)
 					ast_verb(3, "Channel %d/%d, span %d received AOC-E charging %d unit%s\n",
 						pri->pvts[chanpos]->logicalspan, pri->pvts[chanpos]->prioffset, pri->span, (int)e->hangup.aoc_units, (e->hangup.aoc_units == 1) ? "" : "s");
@@ -7307,9 +7297,9 @@ static void *pri_dchannel(void *vpri)
 					pri_hangup(pri->pri, pri->pvts[chanpos]->call, e->hangup.cause);
 					pri->pvts[chanpos]->call = NULL;
 				}
-#if defined(FORCE_RESTART_UNAVAIL_CHANS)
 				if (e->hangup.cause == PRI_CAUSE_REQUESTED_CHAN_UNAVAIL
 					&& pri->sig != SIG_BRI_PTMP && !pri->resetting
+					&& pri->force_restart_unavailable_chans
 					&& pri->pvts[chanpos]->resetting == SIG_PRI_RESET_IDLE) {
 					ast_verb(3,
 						"Span %d: Forcing restart of channel %d/%d since channel reported in use\n",
@@ -7318,7 +7308,6 @@ static void *pri_dchannel(void *vpri)
 					pri->pvts[chanpos]->resetting = SIG_PRI_RESET_ACTIVE;
 					pri_reset(pri->pri, PVT_TO_CHANNEL(pri->pvts[chanpos]));
 				}
-#endif	/* defined(FORCE_RESTART_UNAVAIL_CHANS) */
 
 #ifdef SUPPORT_USERUSER
 				if (!ast_strlen_zero(e->hangup.useruserinfo)) {