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

diff --git a/CHANGES b/CHANGES
index fcb4877f4bd8d013e987030066186eef20294487..1b3961954cdb9c59df59dca79d03c60e733a3416 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -48,6 +48,9 @@ chan_dahdi
 ------------------
  * The CALLERID(ani2) value for incoming calls is now populated in featdmf
    signaling mode.  The information was previously discarded.
+ * Added the force_restart_unavailable_chans compatibility option.  When
+   enabled it causes Asterisk to restart the ISDN B channel if an outgoing
+   call receives cause 44 (Requested channel not available).
 
 chan_iax2
 ------------------

diff --git a/channels/chan_dahdi.c b/channels/chan_dahdi.c
index b7df2b8113ac84f7cc7043b1a149441952ceb63c..b9405d5916c4f8ebeb5dfc54619d0c2f18cba356 100644 (file)
--- a/channels/chan_dahdi.c
+++ b/channels/chan_dahdi.c
@@ -12346,6 +12346,7 @@ static struct dahdi_pvt *mkintf(int channel, const struct dahdi_chan_conf *conf,
 #if defined(HAVE_PRI_MCID)
                                                pris[span].pri.mcid_send = conf->pri.pri.mcid_send;
 #endif /* defined(HAVE_PRI_MCID) */
+                                               pris[span].pri.force_restart_unavailable_chans = conf->pri.pri.force_restart_unavailable_chans;
 #if defined(HAVE_PRI_DATETIME_SEND)
                                                pris[span].pri.datetime_send = conf->pri.pri.datetime_send;
 #endif /* defined(HAVE_PRI_DATETIME_SEND) */
@@ -18258,6 +18259,8 @@ static int process_dahdi(struct dahdi_chan_conf *confp, const char *cat, struct
                                else
                                        ast_log(LOG_WARNING, "'%s' is not a valid reset interval, should be >= 60 seconds or 'never' at line %d.\n",
                                                v->value, v->lineno);
+                       } else if (!strcasecmp(v->name, "force_restart_unavailable_chans")) {
+                               confp->pri.pri.force_restart_unavailable_chans = ast_true(v->value);
                        } else if (!strcasecmp(v->name, "minunused")) {
                                confp->pri.pri.minunused = atoi(v->value);
                        } else if (!strcasecmp(v->name, "minidle")) {

diff --git a/channels/sig_pri.c b/channels/sig_pri.c
index e4ad589c18234d6733c46536789fa970c0e61114..c58a3f358292127627b47ee9834a7900907d432e 100644 (file)
--- 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)) {

diff --git a/channels/sig_pri.h b/channels/sig_pri.h
index 12f3dcae70aad8af002d44048990cea390cdbe52..52e6c729db109fd15b322cf6a8305b1f3a9791ed 100644 (file)
--- a/channels/sig_pri.h
+++ b/channels/sig_pri.h
@@ -496,6 +496,8 @@ struct sig_pri_span {
 #if defined(HAVE_PRI_MCID)
        /*! \brief TRUE if allow sending MCID request on this span. */
        unsigned int mcid_send:1;
+       /*! \brief TRUE if forcing RESTART when receive cause 44 on this span. */
+       unsigned int force_restart_unavailable_chans:1;
 #endif /* defined(HAVE_PRI_MCID) */
 #if defined(HAVE_PRI_DATETIME_SEND)
        /*! \brief Configured date/time ie send policy option. */

diff --git a/configs/samples/chan_dahdi.conf.sample b/configs/samples/chan_dahdi.conf.sample
index 13691fcdf231e8c664fe5e37648f1a69bdd479d2..e67574b9b117437bb90fdc78869262f4d6c2de43 100644 (file)
--- a/configs/samples/chan_dahdi.conf.sample
+++ b/configs/samples/chan_dahdi.conf.sample
@@ -196,6 +196,20 @@ context=public
 ;
 ;resetinterval = 3600
 ;
+; Enable per span 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 might help.
+;
+; NOTE: Sending a RESTART in response to a cause 44 is not required
+; (nor prohibited) by the standards and is likely a primitive chan_dahdi
+; response to call collisions (glare) and buggy peers.  However, there
+; are telco switches out there that ignore the RESTART and continue to
+; send calls to the channel in the restarting state.
+; Default no.
+;
+;force_restart_unavailable_chans=yes
+;
 ; Assume inband audio may be present when a SETUP ACK message is received.
 ; Q.931 Section 5.1.3 says that in scenarios with overlap dialing, when a
 ; dialtone is sent from the network side, progress indicator 8 "Inband info