chan_dahdi: Add inband_on_proceeding compatibility option.

The new inband_on_proceeding option causes Asterisk to assume inband audio
may be present when a PROCEEDING message is received.

Q.931 Section 5.1.2 says the network cannot assume that the CPE side has
attached to the B channel at this time without explicitly sending the
progress indicator ie informing the CPE side to attach to the B channel
for audio.  However, some non-compliant ISDN switches send a PROCEEDING
without the progress indicator ie indicating inband audio is available and
assume that the CPE device has connected the media path for listening to
ringback and other messages.

ASTERISK-17834 which causes this issue was dealing with a non-compliant
network switch.

(closes issue ASTERISK-21151)
Reported by: Gianluca Merlo
Tested by: rmudgett


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@384685 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_dahdi.c

@@ -1365,6 +1365,7 @@ static struct dahdi_chan_conf dahdi_chan_conf_default(void)
 			.localdialplan = PRI_NATIONAL_ISDN + 1,
 			.nodetype = PRI_CPE,
 			.qsigchannelmapping = DAHDI_CHAN_MAPPING_PHYSICAL,
+			.inband_on_proceeding = 1,
 
 #if defined(HAVE_PRI_CCSS)
 			.cc_ptmp_recall_mode = 1,/* specificRecall */
@@ -12680,6 +12681,7 @@ static struct dahdi_pvt *mkintf(int channel, const struct dahdi_chan_conf *conf,
 							pris[span].pri.layer1_ignored = 0;
 						}
 						pris[span].pri.append_msn_to_user_tag = conf->pri.pri.append_msn_to_user_tag;
+						pris[span].pri.inband_on_proceeding = conf->pri.pri.inband_on_proceeding;
 						ast_copy_string(pris[span].pri.initial_user_tag, conf->chan.cid_tag, sizeof(pris[span].pri.initial_user_tag));
 						ast_copy_string(pris[span].pri.msn_list, conf->pri.pri.msn_list, sizeof(pris[span].pri.msn_list));
 #if defined(HAVE_PRI_MWI)
@@ -17677,6 +17679,8 @@ static int process_dahdi(struct dahdi_chan_conf *confp, const char *cat, struct
 #endif	/* defined(HAVE_PRI_MWI) */
 			} else if (!strcasecmp(v->name, "append_msn_to_cid_tag")) {
 				confp->pri.pri.append_msn_to_user_tag = ast_true(v->value);
+			} else if (!strcasecmp(v->name, "inband_on_proceeding")) {
+				confp->pri.pri.inband_on_proceeding = ast_true(v->value);
 			} else if (!strcasecmp(v->name, "layer1_presence")) {
 				if (!strcasecmp(v->value, "required")) {
 					confp->pri.pri.layer1_ignored = 0;

channels/sig_pri.c

@@ -5678,9 +5678,11 @@ static void *pri_dchannel(void *vpri)
 					/* Bring voice path up */
 					pri_queue_control(pri, chanpos, AST_CONTROL_PROGRESS);
 					pri->pvts[chanpos]->progress = 1;
+					sig_pri_set_dialing(pri->pvts[chanpos], 0);
 					sig_pri_open_media(pri->pvts[chanpos]);
+				} else if (pri->inband_on_proceeding) {
+					sig_pri_set_dialing(pri->pvts[chanpos], 0);
 				}
-				sig_pri_set_dialing(pri->pvts[chanpos], 0);
 				sig_pri_unlock_private(pri->pvts[chanpos]);
 				break;
 			case PRI_EVENT_FACILITY:

channels/sig_pri.h

@@ -393,6 +393,8 @@ struct sig_pri_span {
 	 * appended to the initial_user_tag[].
 	 */
 	unsigned int append_msn_to_user_tag:1;
+	/*! TRUE if a PROCEEDING message needs to unsquelch the received audio. */
+	unsigned int inband_on_proceeding:1;
 	int dialplan;							/*!< Dialing plan */
 	int localdialplan;						/*!< Local dialing plan */
 	char internationalprefix[10];			/*!< country access code ('00' for european dialplans) */

configs/chan_dahdi.conf.sample

@@ -169,6 +169,18 @@
 ;
 ;resetinterval = 3600
 ;
+; Assume inband audio may be present when a PROCEEDING message is received.
+; Q.931 Section 5.1.2 says the network cannot assume that the CPE side has
+; attached to the B channel at this time without explicitly sending the
+; progress indicator ie informing the CPE side to attach to the B channel
+; for audio.  However, some non-compliant ISDN switches send a PROCEEDING
+; without the progress indicator ie indicating inband audio is available and
+; assume that the CPE device has connected the media path for listening to
+; ringback and other messages.
+; Default yes in current release branches for backward compatibility.
+;
+;inband_on_proceeding=yes
+;
 ; Overlap dialing mode (sending overlap digits)
 ; Cannot be changed on a reload.
 ;