Correctly apply FAXOPT settings (V17, V27, V29) before starting spandsp layer

While the FAXOPT function could be used to set the modem capabilities, the
input to that function was not being applied correctly to the spandsp layer.
This patch applies the current model capabilities before starting the spandsp
layer.

(closes issue: ASTERISK-16409)
Reported by: Kristijan Vrban
Tested by: Matt Jordan, Matthew Nicholson
Patches:
  spandsp-modems-1.8.diff uploaded by mnicholson (license 5081)
  spandsp-modems-10.diff uploaded by mnicholson (license 5081)
........

Merged revisions 352144 from http://svn.asterisk.org/svn/asterisk/branches/1.8


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@352149 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_fax_spandsp.c

@@ -166,6 +166,7 @@ static int t38_tx_packet_handler(t38_core_state_t *t38_core_state, void *data, c
 static void t30_phase_e_handler(t30_state_t *t30_state, void *data, int completion_code);
 static void spandsp_log(int level, const char *msg);
 static int update_stats(struct spandsp_pvt *p, int completion_code);
+static int spandsp_modems(struct ast_fax_session_details *details);
 
 static void set_logging(logging_state_t *state, struct ast_fax_session_details *details);
 static void set_local_info(t30_state_t *t30_state, struct ast_fax_session_details *details);
@@ -473,6 +474,31 @@ static int spandsp_v21_new(struct spandsp_pvt *p)
 	return 0;
 }
 
+static int spandsp_modems(struct ast_fax_session_details *details)
+{
+	int modems = 0;
+	if (AST_FAX_MODEM_V17 & details->modems) {
+		modems |= T30_SUPPORT_V17;
+	}
+	if (AST_FAX_MODEM_V27 & details->modems) {
+		modems |= T30_SUPPORT_V27TER;
+	}
+	if (AST_FAX_MODEM_V29 & details->modems) {
+		modems |= T30_SUPPORT_V29;
+	}
+	if (AST_FAX_MODEM_V34 & details->modems) {
+#if defined(T30_SUPPORT_V34)
+		modems |= T30_SUPPORT_V34;
+#elif defined(T30_SUPPORT_V34HDX)
+		modems |= T30_SUPPORT_V34HDX;
+#else
+		ast_log(LOG_WARNING, "v34 not supported in this version of spandsp\n");
+#endif
+	}
+
+	return modems;
+}
+
 /*! \brief create an instance of the spandsp tech_pvt for a fax session */
 static void *spandsp_fax_new(struct ast_fax_session *s, struct ast_fax_tech_token *token)
 {
@@ -730,7 +756,7 @@ static void spandsp_fax_gw_gen_release(struct ast_channel *chan, void *data) {
 static int spandsp_fax_gateway_start(struct ast_fax_session *s) {
 	struct spandsp_pvt *p = s->tech_pvt;
 	struct ast_fax_t38_parameters *t38_param;
-	int i, modems = 0;
+	int i;
 	struct ast_channel *peer;
 	static struct ast_generator t30_gen = {
 		alloc: spandsp_fax_gw_gen_alloc,
@@ -781,26 +807,8 @@ static int spandsp_fax_gateway_start(struct ast_fax_session *s) {
 	t38_gateway_set_transmit_on_idle(&p->t38_gw_state, TRUE);
 	t38_set_sequence_number_handling(p->t38_core_state, TRUE);
 
-	if (AST_FAX_MODEM_V17 & s->details->modems) {
-		modems |= T30_SUPPORT_V17;
-	}
-	if (AST_FAX_MODEM_V27 & s->details->modems) {
-		modems |= T30_SUPPORT_V27TER;
-	}
-	if (AST_FAX_MODEM_V29 & s->details->modems) {
-		modems |= T30_SUPPORT_V29;
-	}
-	if (AST_FAX_MODEM_V34 & s->details->modems) {
-#if defined(T30_SUPPORT_V34)
-		modems |= T30_SUPPORT_V34;
-#elif defined(T30_SUPPORT_V34HDX)
-		modems |= T30_SUPPORT_V34HDX;
-#else
-		ast_log(LOG_WARNING, "v34 not supported in this version of spandsp\n");
-#endif
-	}
 
-	t38_gateway_set_supported_modems(&p->t38_gw_state, modems);
+	t38_gateway_set_supported_modems(&p->t38_gw_state, spandsp_modems(s->details));
 
 	/* engage udptl nat on other side of T38 line 
 	 * (Asterisk changes media ports thus we send a few packets to reinitialize
@@ -895,6 +903,7 @@ static int spandsp_fax_start(struct ast_fax_session *s)
 	set_local_info(p->t30_state, s->details);
 	set_file(p->t30_state, s->details);
 	set_ecm(p->t30_state, s->details);
+	t30_set_supported_modems(p->t30_state, spandsp_modems(s->details));
 
 	/* perhaps set_transmit_on_idle() should be called */