From 172dee960aa7ad0bc1acae3e28f886781f65bce3 Mon Sep 17 00:00:00 2001
From: Andreas Eversberg <jolly@eversberg.eu>
Date: Tue, 28 Mar 2023 19:10:49 +0200
Subject: [PATCH] Send Contract when receving a call

Contact with correct peer address must be included, so the call proceeds
correctly.

Only the host/port is used, no user. This seems to work.
---
 src/sip/sip.c | 41 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/src/sip/sip.c b/src/sip/sip.c
index 7064f34..9754f88 100755
--- a/src/sip/sip.c
+++ b/src/sip/sip.c
@@ -586,8 +586,35 @@ static void setup_req(call_t *call, osmo_cc_msg_t *msg)
 	osmo_cc_ll_msg(&call->sip_ep->cc_ep, call->cc_callref, msg);
 }
 
+static const char *response_contact(call_t *call)
+{
+	static char contact[1024] = "";
+	const char *peer, *p;
+
+	/* provide contact with correct peer */
+	if (call->sip_ep->public_ip[0])
+		peer = call->sip_ep->public_ip;
+	else
+		peer = call->sip_ep->local_peer;
+	sprintf(contact, "sip:%s", peer);
+	/* if port is not set (maybe public IP), get it from local_peer */
+	if (!strchr(peer, ':')) {
+		/* append port of local peer or use 5060, if not exits */
+		p = osmo_cc_port_of_address(call->sip_ep->local_peer);
+		if (!p)
+			p = "5060";
+		strcat(contact, ":");
+		strcat(contact, p);
+	}
+	PDEBUG(DSIP, DEBUG_DEBUG, " -> Contact = %s\n", contact);
+
+	return contact;
+}
+
 static void send_progress_sdp(call_t *call, const char *sdp)
 {
+	const char *contact;
+
 	if (call->sdp_sent)
 		return;
 
@@ -603,8 +630,11 @@ static void send_progress_sdp(call_t *call, const char *sdp)
 
 	PDEBUG(DSIP, DEBUG_INFO, "Sending INVITE response: %d %s (callref %d)\n", SIP_183_SESSION_PROGRESS, call->cc_callref);
 
+	contact = response_contact(call);
+
 	nua_respond(call->nua_handle, SIP_183_SESSION_PROGRESS,
 		NUTAG_MEDIA_ENABLE(0),
+		TAG_IF(contact[0], SIPTAG_CONTACT_STR(contact)),
 		TAG_IF(sdp, SIPTAG_CONTENT_TYPE_STR("application/sdp")),
 		TAG_IF(sdp, SIPTAG_PAYLOAD_STR(sdp)),
 		TAG_END());
@@ -635,6 +665,7 @@ static void alert_req(call_t *call, osmo_cc_msg_t *msg)
 {
 	char sdp[65536];
 	int rc;
+	const char *contact;
 
 	rc = osmo_cc_get_ie_sdp(msg, 0, sdp, sizeof(sdp));
 	if (rc >= 0)
@@ -645,9 +676,13 @@ static void alert_req(call_t *call, osmo_cc_msg_t *msg)
 		return;
 	}
 
+	contact = response_contact(call);
+
 	PDEBUG(DSIP, DEBUG_INFO, "Sending INVITE response: %d %s (callref %d)\n", SIP_180_RINGING, call->cc_callref);
 
-	nua_respond(call->nua_handle, SIP_180_RINGING, TAG_END());
+	nua_respond(call->nua_handle, SIP_180_RINGING,
+		TAG_IF(contact[0], SIPTAG_CONTACT_STR(contact)),
+		TAG_END());
 }
 
 static void setup_rsp(call_t *call, osmo_cc_msg_t *msg)
@@ -655,6 +690,7 @@ static void setup_rsp(call_t *call, osmo_cc_msg_t *msg)
 	char sdp_buffer[65536];
 	const char *sdp;
 	int rc;
+	const char *contact;
 
 	rc = osmo_cc_get_ie_sdp(msg, 0, sdp_buffer, sizeof(sdp_buffer));
 	if (rc < 0) {
@@ -674,10 +710,13 @@ static void setup_rsp(call_t *call, osmo_cc_msg_t *msg)
 	} else
 		PDEBUG(DSIP, DEBUG_INFO, "There was no SDP received during PROC/ALERT/PROGRESS/SETUP-RSP from Osmo-CC. The call will fail due to missing SDP. (callref %d)\n", call->cc_callref);
 
+	contact = response_contact(call);
+
 	PDEBUG(DSIP, DEBUG_INFO, "Sending INVITE response: %d %s (callref %d)\n", SIP_200_OK, call->cc_callref);
 
 	nua_respond(call->nua_handle, SIP_200_OK,
 		NUTAG_MEDIA_ENABLE(0),
+		TAG_IF(contact[0], SIPTAG_CONTACT_STR(contact)),
 		TAG_IF(sdp, SIPTAG_CONTENT_TYPE_STR("application/sdp")),
 		TAG_IF(sdp, SIPTAG_PAYLOAD_STR(sdp)),
 		TAG_END());