--- a/sip-in/bye_out.c	Tue Sep 20 20:11:44 2022 -0800
+++ b/sip-in/bye_out.c	Tue Sep 20 20:33:09 2022 -0800
@@ -16,6 +16,9 @@
 #include "../libsip/out_msg.h"
 #include "call.h"
 
+extern char *get_single_header();
+extern struct call *find_call_by_sip_id();
+
 extern struct in_addr sip_bind_ip;
 extern unsigned sip_bind_port;
 
@@ -72,3 +75,32 @@
 	call->sip_state = SIP_STATE_BYE_SENT;
 	call->sip_tx_count = 1;
 }
+
+void
+process_sip_response(msg, sin)
+	struct sip_pkt_rx *msg;
+	struct sockaddr_in *sin;
+{
+	char *call_id_hdr, *cseq_hdr;
+	struct call *call;
+
+	call_id_hdr = get_single_header(msg, "Call-ID", "i", (int *) 0);
+	if (!call_id_hdr)
+		return;
+	call = find_call_by_sip_id(call_id_hdr);
+	if (!call)
+		return;
+	cseq_hdr = get_single_header(msg, "CSeq", (char *) 0, (int *) 0);
+	if (!cseq_hdr)
+		return;
+	if (strcmp(cseq_hdr, "1 BYE")) {
+		syslog(LOG_ERR,
+			"UAC received response with unknown CSeq %.32s",
+			cseq_hdr);
+		return;
+	}
+	if (msg->status_code < 200)
+		return;
+	if (call->sip_state == SIP_STATE_BYE_SENT)
+		call->sip_state = SIP_STATE_ENDED;
+}