Change fax detection in chan_sip so it behaves as one would expect.

Internally the way T.38 is negotiated has changed and the option no longer
reflects a behavior that is valid. It will now look for a CNG tone on
received calls and if present send the call to the 'fax' extension. It is
then up to the application or channel to request the switch over to T.38.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@230881 65c4cc65-6c06-0410-ace0-fbb531ad65f3

2 files changed, 60 insertions, 27 deletions

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index f36f05036..bb5e49567 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -1828,7 +1828,7 @@ struct sip_pvt {
 	int laststate;				/*!< SUBSCRIBE: Last known extension state */
 	int dialogver;				/*!< SUBSCRIBE: Version for subscription dialog-info */
 
-	struct ast_dsp *dsp;			/*!< Inband DTMF Detection dsp */
+	struct ast_dsp *dsp;			/*!< Inband DTMF or Fax CNG tone Detection dsp */
 
 	struct sip_peer *relatedpeer;		/*!< If this dialog is related to a peer, which one
 							Used in peerpoke, mwi subscriptions */
@@ -4442,23 +4442,40 @@ static int send_request(struct sip_pvt *p, struct sip_request *req, enum xmittyp
 	return res;
 }
 
-static void enable_digit_detect(struct sip_pvt *p)
+static void enable_dsp_detect(struct sip_pvt *p)
 {
+	int features = 0;
+
 	if (p->dsp) {
 		return;
 	}
 
+	if ((ast_test_flag(&p->flags[0], SIP_DTMF) == SIP_DTMF_INBAND) ||
+            (ast_test_flag(&p->flags[0], SIP_DTMF) == SIP_DTMF_AUTO)) {
+		if (!p->rtp || ast_rtp_instance_dtmf_mode_set(p->rtp, AST_RTP_DTMF_MODE_INBAND)) {
+			features |= DSP_FEATURE_DIGIT_DETECT;
+                }
+	}
+
+	if (ast_test_flag(&p->flags[1], SIP_PAGE2_FAX_DETECT)) {
+		features |= DSP_FEATURE_FAX_DETECT;
+	}
+
+	if (!features) {
+		return;
+	}
+
 	if (!(p->dsp = ast_dsp_new())) {
 		return;
 	}
 
-	ast_dsp_set_features(p->dsp, DSP_FEATURE_DIGIT_DETECT);
+	ast_dsp_set_features(p->dsp, features);
 	if (global_relaxdtmf) {
 		ast_dsp_set_digitmode(p->dsp, DSP_DIGITMODE_DTMF | DSP_DIGITMODE_RELAXDTMF);
 	}
 }
 
-static void disable_digit_detect(struct sip_pvt *p)
+static void disable_dsp_detect(struct sip_pvt *p)
 {
 	if (p->dsp) {
 		ast_dsp_free(p->dsp);
@@ -4489,9 +4506,9 @@ static int sip_setoption(struct ast_channel *chan, int option, void *data, int d
 
 			ast_debug(1, "%sabling digit detection on %s\n", *cp ? "En" : "Dis", chan->name);
 			if (*cp) {
-				enable_digit_detect(p);
+				enable_dsp_detect(p);
 			} else {
-				disable_digit_detect(p);
+				disable_dsp_detect(p);
 			}
 			res = 0;
 		}
@@ -6329,7 +6346,7 @@ static int sip_hangup(struct ast_channel *ast)
 	append_history(p, needcancel ? "Cancel" : "Hangup", "Cause %s", p->owner ? ast_cause2str(p->hangupcause) : "Unknown");
 
 	/* Disconnect */
-	disable_digit_detect(p);
+	disable_dsp_detect(p);
 
 	p->owner = NULL;
 	ast->tech_pvt = dialog_unref(ast->tech_pvt, "unref ast->tech_pvt");
@@ -6996,10 +7013,12 @@ static struct ast_channel *sip_new(struct sip_pvt *i, int state, const char *tit
 	else
 		ast_debug(3, "This channel will not be able to handle video.\n");
 
+	enable_dsp_detect(i);
+
 	if ((ast_test_flag(&i->flags[0], SIP_DTMF) == SIP_DTMF_INBAND) ||
 	    (ast_test_flag(&i->flags[0], SIP_DTMF) == SIP_DTMF_AUTO)) {
 		if (!i->rtp || ast_rtp_instance_dtmf_mode_set(i->rtp, AST_RTP_DTMF_MODE_INBAND)) {
-			enable_digit_detect(i);
+			enable_dsp_detect(i);
 		}
 	} else if (ast_test_flag(&i->flags[0], SIP_DTMF) == SIP_DTMF_RFC2833) {
 		if (i->rtp) {
@@ -7321,9 +7340,17 @@ static struct ast_frame *sip_rtp_read(struct ast_channel *ast, struct sip_pvt *p
 	if (f && p->dsp) {
 		f = ast_dsp_process(p->owner, p->dsp, f);
 		if (f && f->frametype == AST_FRAME_DTMF) {
-			if (ast_test_flag(&p->flags[1], SIP_PAGE2_T38SUPPORT) && f->subclass.integer == 'f') {
-				ast_debug(1, "Fax CNG detected on %s\n", ast->name);
+			if (f->subclass.integer == 'f') {
+				if (option_debug)
+					ast_log(LOG_DEBUG, "Fax CNG detected on %s\n", ast->name);
 				*faxdetect = 1;
+				/* If we only needed this DSP for fax detection purposes we can just drop it now */
+				if (ast_test_flag(&p->flags[0], SIP_DTMF) == SIP_DTMF_INBAND) {
+					ast_dsp_set_features(p->dsp, DSP_FEATURE_DIGIT_DETECT);
+				} else {
+					ast_dsp_free(p->dsp);
+					p->dsp = NULL;
+				}
 			} else {
 				ast_debug(1, "* Detected inband DTMF '%c'\n", f->subclass.integer);
 			}
@@ -7344,20 +7371,26 @@ static struct ast_frame *sip_read(struct ast_channel *ast)
 	fr = sip_rtp_read(ast, p, &faxdetected);
 	p->lastrtprx = time(NULL);
 
-	/* If we are NOT bridged to another channel, and we have detected fax tone we issue T38 re-invite to a peer */
-	/* If we are bridged then it is the responsibility of the SIP device to issue T38 re-invite if it detects CNG or fax preamble */
-	if (faxdetected && ast_test_flag(&p->flags[1], SIP_PAGE2_T38SUPPORT) && (p->t38.state == T38_DISABLED) && !(ast_bridged_channel(ast))) {
-		if (!ast_test_flag(&p->flags[0], SIP_GOTREFER)) {
-			if (!p->pendinginvite) {
-				ast_debug(3, "Sending reinvite on SIP (%s) for T.38 negotiation.\n", ast->name);
-				change_t38_state(p, T38_LOCAL_REINVITE);
-				transmit_reinvite_with_sdp(p, TRUE, FALSE);
-			}
-		} else if (!ast_test_flag(&p->flags[0], SIP_PENDINGBYE)) {
-			ast_debug(3, "Deferring reinvite on SIP (%s) - it will be re-negotiated for T.38\n", ast->name);
-			ast_set_flag(&p->flags[0], SIP_NEEDREINVITE);
-		}
-	}
+	/* If we detect a CNG tone and fax detection is enabled then send us off to the fax extension */
+	if (faxdetected && ast_test_flag(&p->flags[1], SIP_PAGE2_FAX_DETECT)) {
+		ast_channel_lock(ast);
+		if (strcmp(ast->exten, "fax")) {
+			const char *target_context = S_OR(ast->macrocontext, ast->context);
+			ast_channel_unlock(ast);
+			if (ast_exists_extension(ast, target_context, "fax", 1, ast->cid.cid_num)) {
+				ast_verbose(VERBOSE_PREFIX_2 "Redirecting '%s' to fax extension\n", ast->name);
+				pbx_builtin_setvar_helper(ast, "FAXEXTEN", ast->exten);
+				if (ast_async_goto(ast, target_context, "fax", 1)) {
+					ast_log(LOG_NOTICE, "Failed to async goto '%s' into fax of '%s'\n", ast->name, target_context);
+				}
+				fr = &ast_null_frame;
+			} else {
+				ast_log(LOG_NOTICE, "Fax detected but no fax extension\n");
+                        }
+		} else {
+			ast_channel_unlock(ast);
+                }
+        }
 
 	/* Only allow audio through if they sent progress with SDP, or if the channel is actually answered */
 	if (fr && fr->frametype == AST_FRAME_VOICE && p->invitestate != INV_EARLY_MEDIA && ast->_state != AST_STATE_UP) {
@@ -26521,9 +26554,9 @@ static int sip_dtmfmode(struct ast_channel *chan, const char *data)
 		ast_rtp_instance_set_prop(p->rtp, AST_RTP_PROPERTY_DTMF, ast_test_flag(&p->flags[0], SIP_DTMF) == SIP_DTMF_RFC2833);
 	if ((ast_test_flag(&p->flags[0], SIP_DTMF) == SIP_DTMF_INBAND) ||
 	    (ast_test_flag(&p->flags[0], SIP_DTMF) == SIP_DTMF_AUTO)) {
-		enable_digit_detect(p);
+		enable_dsp_detect(p);
 	} else {
-		disable_digit_detect(p);
+		disable_dsp_detect(p);
 	}
 	sip_pvt_unlock(p);
 	ast_channel_unlock(chan);
diff --git a/configs/sip.conf.sample b/configs/sip.conf.sample
index c42f9abf7..af3012a7a 100644
--- a/configs/sip.conf.sample
+++ b/configs/sip.conf.sample
@@ -552,7 +552,7 @@ srvlookup=yes                   ; Enable DNS SRV lookups on outbound calls
 ;                                       ; send 400 byte T.38 FAX packets to it.
 ;
 ; FAX detection will cause the SIP channel to jump to the 'fax' extension (if it exists)
-; after T.38 is successfully negotiated.
+; when a CNG tone is detected on an incoming call.
 ;
 ; faxdetect = yes              ; Default false
 ;