--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sip-manual-out/sdp_in.c	Fri Mar 17 12:07:17 2023 -0800
@@ -0,0 +1,74 @@
+/*
+ * In this module we handle SDP responses to our INVITE.
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include "../libsip/parse.h"
+#include "../libsip/sdp.h"
+
+extern char *get_single_header();
+extern char *extract_to_tag();
+
+struct sockaddr_in rtp_remote_addr;
+int pcma_selected;
+
+static
+check_sdp_present(msg)
+	struct sip_pkt_rx *msg;
+{
+	char *hval;
+
+	if (!msg->msg_body_len)
+		return 0;
+	hval = get_single_header(msg, "Content-Type", "c", (int *) 0);
+	if (!hval)
+		return 0;
+	if (!strcasecmp(hval, "application/sdp"))
+		return 1;
+	else
+		return 0;
+}
+
+void
+extract_resp_sdp(msg)
+	struct sip_pkt_rx *msg;
+{
+	struct sdp_parse sdp_parse;
+	int rc;
+
+	if (!check_sdp_present(msg)) {
+		printf("INVITE response has no SDP!\n");
+		return;
+	}
+	rc = parse_incoming_sdp(msg->msg_body, msg->msg_body_len, &sdp_parse);
+	if (rc < 0) {
+		printf("SDP parse error: %d\n", rc);
+		return;
+	}
+	switch (sdp_parse.codec_mask) {
+	case SDP_CODEC_MASK_PCMU:
+	case SDP_CODEC_MASK_BOTH:
+		pcma_selected = 0;
+		break;
+	case SDP_CODEC_MASK_PCMA:
+	case SDP_CODEC_MASK_BOTH | SDP_CODEC_MASK_PCMA_PREF:
+		pcma_selected = 1;
+		break;
+	default:
+		printf("SDP error: no supported codec\n");
+		return;
+	}
+	printf("SDP response: IP %s port %u codec %s\n",
+		inet_ntoa(sdp_parse.ip_addr), sdp_parse.audio_port,
+		pcma_selected ? "PCMA" : "PCMU");
+	rtp_remote_addr.sin_family = AF_INET;
+	rtp_remote_addr.sin_addr = sdp_parse.ip_addr;
+	rtp_remote_addr.sin_port = htons(sdp_parse.audio_port);
+}