Description: This patch introduces a new channel variable SIPURIOPTION which contains the uri options from Refer-To URI during call transfer. 
It enables passing of important uri options like "transport=tcp" which enable VCC and in turn VoxSBC to transfer the call on tcp.
Author: Nitesh Bansal <nbansal@voxbone.com>
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -17800,6 +17800,7 @@
 	struct sip_request *req = NULL;
 	const char *transfer_context = NULL;
 	struct sip_refer *refer;
+	char *urioption = NULL;
 
 	req = outgoing_req;
 	refer = transferer->refer;
@@ -17910,7 +17911,7 @@
 	}
 
 	if ((ptr = strchr(refer_to, '@'))) {	/* Separate domain */
-		char *urioption = NULL, *domain;
+		char *domain;
 		int bracket = 0;
 		*ptr++ = '\0';
 
@@ -17933,15 +17934,25 @@
 		}
 
 		SIP_PEDANTIC_DECODE(domain);
-		SIP_PEDANTIC_DECODE(urioption);
 
 		/* Save the domain for the dial plan */
 		ast_string_field_set(refer, refer_to_domain, domain);
-		if (urioption) {
-			ast_string_field_set(refer, refer_to_urioption, urioption);
+	}
+	else
+	{
+		/* No domain, but still there could be some URI options */
+		if ((urioption = strchr(ptr, ';')))
+		{
+			*urioption++ = '\0';
 		}
 	}
 
+	SIP_PEDANTIC_DECODE(urioption);
+
+	if (urioption) {
+			ast_string_field_set(refer, refer_to_urioption, urioption);
+	}
+
 	if ((ptr = strchr(refer_to, ';'))) /* Remove options */
 		*ptr = '\0';
 
@@ -26195,6 +26206,7 @@
 	struct ast_channel *chans[2] = { 0, };
 	char *refer_to = NULL;
 	char *refer_to_domain = NULL;
+	char *refer_to_urioption= NULL;
 	char *refer_to_context = NULL;
 	char *referred_by = NULL;
 	char *callid = NULL;
@@ -26391,6 +26403,7 @@
 	/* Copy data we can not safely access after letting the pvt lock go. */
 	refer_to = ast_strdupa(p->refer->refer_to);
 	refer_to_domain = ast_strdupa(p->refer->refer_to_domain);
+	refer_to_urioption = ast_strdupa(p->refer->refer_to_urioption);
 	refer_to_context = ast_strdupa(p->refer->refer_to_context);
 	referred_by = ast_strdupa(p->refer->referred_by);
 	callid = ast_strdupa(p->callid);
@@ -26453,6 +26466,7 @@
 	if (current.chan2) {
 		pbx_builtin_setvar_helper(current.chan2, "BLINDTRANSFER", ast_channel_name(current.chan1));
 		pbx_builtin_setvar_helper(current.chan2, "SIPDOMAIN", refer_to_domain);
+		pbx_builtin_setvar_helper(current.chan2, "SIPURIOPTION", refer_to_urioption);
 		pbx_builtin_setvar_helper(current.chan2, "SIPTRANSFER", "yes");
 		/* One for the new channel */
 		pbx_builtin_setvar_helper(current.chan2, "_SIPTRANSFER", "yes");