/*
 * This program is a combination of rtp-gsmfr-extr and gsmrec-dump into
 * one step: it reads a pcap file, extracts packets belonging to a
 * particular RTP stream as identified by a source or destination
 * IP:port, verifies that an unbroken RTP stream is present, which is
 * expected to be in GSM FR or EFR codec, but instead of writing this
 * FR/EFR frame stream to a gsmx file, decodes it like gsmrec-dump.
 *
 * The advantage of this program over running rtp-gsmfr-extr followed
 * by gsmrec-dump is that TRAUlike Extension Headers (if present) are
 * dumped for analysis, rather than discarded.
 */

#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 <pcap/pcap.h>
#include <gsm.h>
#include <gsm_efr.h>

static pcap_t *pcap;
static in_addr_t match_ip_addr;
static u_short match_udp_port;
static unsigned iphdr_addr_offset, udphdr_port_offset;
static unsigned link_hdr_len, ethertype_offset;
static int stream_init_flag;
static unsigned last_seq, last_tstamp, stream_ssrc;
static gsm dummy_state;

static void
check_dl_type()
{
	int dltype;

	dltype = pcap_datalink(pcap);
	switch (dltype) {
	case DLT_EN10MB:
		link_hdr_len = 14;
		ethertype_offset = 12;
		break;
	case DLT_RAW:
		link_hdr_len = 0;
		break;
	case DLT_LINUX_SLL:
		link_hdr_len = 16;
		ethertype_offset = 14;
		break;
	default:
		fprintf(stderr, "error: unsupported data link type %d\n",
			dltype);
		exit(1);
	}
}

static void
rtp_stream_logic(rtp_hdr, pkt_idx)
	u_char *rtp_hdr;
	unsigned pkt_idx;
{
	unsigned cur_seq, cur_tstamp, cur_ssrc;

	cur_seq = (rtp_hdr[2] << 8) | rtp_hdr[3];
	cur_tstamp = (rtp_hdr[4] << 24) | (rtp_hdr[5] << 16) |
			(rtp_hdr[6] << 8) | rtp_hdr[7];
	cur_ssrc = (rtp_hdr[8] << 24) | (rtp_hdr[9] << 16) |
			(rtp_hdr[10] << 8) | rtp_hdr[11];
	if (stream_init_flag) {
		if (cur_ssrc != stream_ssrc) {
			printf(
		"error in packet #%u: SSRC change from 0x%08X to 0x%08X\n",
				pkt_idx, stream_ssrc, cur_ssrc);
		} else if (cur_seq != last_seq + 1 &&
			   (cur_seq != 0 || last_seq != 0xFFFF)) {
			printf(
		"error in packet #%u: seq break from 0x%04X to 0x%04X\n",
				pkt_idx, last_seq, cur_seq);
		} else if (cur_tstamp != last_tstamp + 160) {
			printf(
		"error in packet #%u: timestamp break from 0x%08X to 0x%08X\n",
				pkt_idx, last_tstamp, cur_tstamp);
		}
	} else
		stream_init_flag = 1;
	last_seq = cur_seq;
	last_tstamp = cur_tstamp;
	stream_ssrc = cur_ssrc;
}

static void
process_payload(payload, payload_len)
	u_char *payload;
	unsigned payload_len;
{
	gsm_signal params[76];
	int i, j, n;

	printf("seq 0x%04X ts 0x%08X: ", last_seq, last_tstamp);
	switch (payload_len) {
	case 0:
		printf("zero-length payload\n");
		return;
	case 1:
		if ((payload[0] & 0xF6) != 0xE6)
			break;
		printf("TEH 0x%02X\n", payload[0]);
		return;
	case 2:
		if (payload[0] != 0xBF)
			break;
		printf("old BFI TAF=%u\n", payload[1] & 1);
		return;
	case 31:
		if ((payload[0] & 0xF0) != 0xC0)
			break;
		printf("std EFR SID=%d LPC", EFR_sid_classify(payload));
		EFR_frame2params(payload, params);
	print_efr:
		n = 0;
		for (i = 0; i < 5; i++)
			printf(" %d", params[n++]);
		putchar('\n');
		for (i = 0; i < 4; i++) {
			putchar(' ');
			for (j = 0; j < 13; j++)
				printf(" %d", params[n++]);
			putchar('\n');
		}
		return;
	case 32:
		if ((payload[0] & 0xF4) != 0xE0)
			break;
		if ((payload[1] & 0xF0) != 0xC0)
			break;
		printf("TEH 0x%02X EFR SID=%d LPC", payload[0],
			EFR_sid_classify(payload+1));
		EFR_frame2params(payload+1, params);
		goto print_efr;
	case 33:
		if ((payload[0] & 0xF0) != 0xD0)
			break;
		fputs("std FR", stdout);
		gsm_explode(dummy_state, payload, params);
	print_fr:
		n = 0;
		for (i = 0; i < 8; i++)
			printf(" %d", params[n++]);
		putchar('\n');
		for (i = 0; i < 4; i++) {
			putchar(' ');
			for (j = 0; j < 17; j++)
				printf(" %d", params[n++]);
			putchar('\n');
		}
		return;
	case 34:
		if ((payload[0] & 0xF4) != 0xE0)
			break;
		if ((payload[1] & 0xF0) != 0xD0)
			break;
		printf("TEH 0x%02X FR", payload[0]);
		gsm_explode(dummy_state, payload+1, params);
		goto print_fr;
	}
	printf("unknown payload format, length=%u\n", payload_len);
}

static void
process_packet(pkt, caplen, pkt_idx)
	u_char *pkt;
	unsigned caplen, pkt_idx;
{
	unsigned udplen, payload_len;

	if (caplen < link_hdr_len + 28)
		return;
	if (link_hdr_len) {
		if (pkt[ethertype_offset] != 0x08)
			return;
		if (pkt[ethertype_offset+1] != 0x00)
			return;
		pkt += link_hdr_len;
		caplen -= link_hdr_len;
	}
	/* check IP header */
	if (pkt[0] != 0x45)
		return;
	if (pkt[9] != 17)	/* UDP */
		return;
	if (bcmp(pkt + iphdr_addr_offset, &match_ip_addr, 4))
		return;
	/* check UDP header */
	if (bcmp(pkt + 20 + udphdr_port_offset, &match_udp_port, 2))
		return;
	/* it is our target - now scrutinize it */
	udplen = (pkt[24] << 8) | pkt[25];
	if (caplen < udplen + 20) {
		fprintf(stderr,
			"error: packet #%u is truncated in the capture\n",
			pkt_idx);
		exit(1);
	}
	if (udplen < 20) {
		fprintf(stderr,
		"error in packet #%u: UDP length is too short for RTP header\n",
			pkt_idx);
		exit(1);
	}
	if (pkt[28] != 0x80) {
		fprintf(stderr,
		"error in packet #%u: unsupported RTP header structure\n",
			pkt_idx);
		exit(1);
	}
	rtp_stream_logic(pkt + 28, pkt_idx);
	process_payload(pkt + 40, udplen - 20);
}

main(argc, argv)
	char **argv;
{
	char errbuf[PCAP_ERRBUF_SIZE];
	u_char *pkt;
	struct pcap_pkthdr pkthdr;
	unsigned pkt_idx;

	if (argc != 5) {
		fprintf(stderr,
			"usage: %s pcap-file src|dest ip-addr udp-port\n",
			argv[0]);
		exit(1);
	}
	pcap = pcap_open_offline(argv[1], errbuf);
	if (!pcap) {
		fprintf(stderr, "%s: %s\n", argv[1], errbuf);
		exit(1);
	}
	check_dl_type();
	if (!strcmp(argv[2], "src")) {
		iphdr_addr_offset = 12;
		udphdr_port_offset = 0;
	} else if (!strcmp(argv[2], "dest")) {
		iphdr_addr_offset = 16;
		udphdr_port_offset = 2;
	} else {
		fprintf(stderr,
		"error: direction argument must be \"src\" or \"dest\"\n");
		exit(1);
	}
	match_ip_addr = inet_addr(argv[3]);
	if (match_ip_addr == INADDR_NONE) {
		fprintf(stderr, "error: IP address argument is invalid\n");
		exit(1);
	}
	match_udp_port = htons(strtoul(argv[4], 0, 0));
	dummy_state = gsm_create();
	if (!dummy_state) {
		fprintf(stderr, "gsm_create() failed!\n");
		exit(1);
	}
	for (pkt_idx = 0; ; pkt_idx++) {
		pkt = pcap_next(pcap, &pkthdr);
		if (!pkt)
			break;
		process_packet(pkt, (unsigned) pkthdr.caplen, pkt_idx);
	}
	if (!stream_init_flag) {
		fprintf(stderr, "error: specified RTP stream not found\n");
		exit(1);
	}
	exit(0);
}