clear buffer

[record-dvb] / sap.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>         
#include <arpa/inet.h>
#include <sys/time.h>
#include <time.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>
#include <sys/select.h>

#include "mcast.h"
#include "sap.h"

#define SAP_ADDR	"224.2.127.254"
#define SAP_PORT	9875
#define SAP_MAX_SIZE	1024

#define SAP_TIMEOUT	3

#define BUFFSIZE	SAP_MAX_SIZE

char *get_url_from_sap(char *service)
{
	struct timeval start, curr;
	struct ip_mreq mreq;
	unsigned char buffer[BUFFSIZE];
	char *url = NULL;
	int fd;

	snprintf(buffer,BUFFSIZE,"udp://%s:%u", SAP_ADDR, SAP_PORT);

	fd = open_mcast(buffer);

	gettimeofday(&start, NULL);

	do {
		int recvd;
		int sap_version, sap_addrtype, sap_messagetype, sap_encrypted, sap_compressed;
		in_addr_t sender_address;
		unsigned char auth_len;
		unsigned short msgid;
		unsigned char *payload, *pos, *host = NULL, *proto = NULL, *port = NULL, *sname = NULL;
		fd_set rfds;
		struct timeval tv;
		int retval;

		FD_ZERO(&rfds);
		FD_SET(fd, &rfds);

		tv.tv_sec = 0;
		tv.tv_usec = 100000;

		if ((retval = select(fd+1, &rfds, NULL, NULL, &tv)) == -1) {
			perror("select");
			return NULL;
		}

		if (!retval) {
			gettimeofday(&curr, NULL);
			continue;
		}

		bzero(buffer, BUFFSIZE);
		if ((recvd = recv(fd, buffer, BUFFSIZE, 0)) < 1) {
			perror("recv");
			return NULL;
		}

		gettimeofday(&curr, NULL);

		sap_version = (buffer[0] >> 5) & 0x7;
		sap_addrtype = (buffer[0] >> 4) & 0x1;
		sap_messagetype = (buffer[0] >> 2) & 0x1;
		sap_encrypted = (buffer[0] >> 1) & 0x1;
		sap_compressed = buffer[0] & 0x1;
		auth_len = buffer[1];
		msgid = buffer[2] << 8 | buffer[3];
		memcpy(&sender_address, buffer+4, (sap_addrtype?16:4));
		payload = buffer + 4 /* (sap_*, auth_len, msgid) */ + (sap_addrtype?16:4) + auth_len;

#ifdef DEBUG
		printf("\n");
		printf("SAP-Version: %d\n", sap_version);
		printf("Adresstyp: %s\n", (sap_addrtype?"IPv6":"IPv4"));
		printf("Messagetype: %s\n", (sap_messagetype?"Announcement":"Deletion"));
		printf("Encrypted: %d\n", sap_encrypted);
		printf("Compressed: %d\n", sap_compressed);
		printf("Authentication Length: %d\n", auth_len);
		printf("Sender: %u\n", sender_address);
		printf("Message Identifier Hash: %u\n", msgid);
#endif

		if (sap_addrtype)
			continue; /* We don't support IPv6 for now */

#if 0 /* Getstream gets this wrong, see rfc2974 */
		if (sap_messagetype)
			continue; /* We are not interested in deletions */
#endif

		if (sap_encrypted || sap_compressed)
			continue;

		/* RFC 2327
		 * v=0
		 * o=- 6dca 1 IN IP4 192.168.100.17:2000
		 * s=TV Das Erste
		 * t=0 0
		 * c=IN IP4 192.168.100.17/1
		 * m=video 2000 http 33
		 * a=tool:getstream
		 * a=type:broadcast
		 */

		pos = payload;
		while(*pos != 0 && (pos-buffer) < recvd) {
			if (*pos == 0x0d)
				*pos = 0;

			if (*pos == 0x0a) {
				*pos = 0;

				if (!strncasecmp("s=", payload, 2)) {
					sname = payload + 2;
				} else if (!strncasecmp("c=", payload, 2)) {
					int poscnt = 0;

					payload += 2;
					while (*payload != 0) {
						if (poscnt == 2 && *payload == '/') {
							*payload = 0;
							break;
						}

						if (*payload == ' ') {
							*payload = 0;
							poscnt++;

							/* c=<network type> <address type> <connection address> */
							if (poscnt == 2)
								host = payload + 1;

							if (poscnt > 2)
								break;
						}
						payload++;
					}
				} else if (!strncasecmp("m=", payload, 2)) {
					int poscnt = 0;

					payload += 2;
					while (*payload != 0) {
						if (*payload == ' ') {
							*payload = 0;
							poscnt++;

							/* m=<media> <port> <transport> <fmt list> */
							if (poscnt == 1)
								port = payload + 1;

							if (poscnt == 2)
								proto = payload + 1;

							if (poscnt > 2)
								break;
						}
						payload++;
					}
				}

				payload = ++pos;
				continue;
			}
			pos++;
		}

		if (sname && proto && port) {
			if (!host) {
				 struct in_addr inaddr;

				 inaddr.s_addr = sender_address;
				 host = inet_ntoa(inaddr);
			}

#ifdef DEBUG
			printf("%s -> %s://%s:%s\n", sname, proto, host, port);
#endif

			if (strlen(service) < strlen(sname)) {
				sname += strlen(sname) - strlen(service);
			}

			if (!strncasecmp(service, sname, strlen(service))) {
				int len = strlen(host)+strlen(proto)+strlen(port)+5;

				if (!(url = malloc(len))) {
					perror("malloc");
					return NULL;
				}

				snprintf(url, len, "%s://%s:%s", proto, host, port);
				url[len-1] = 0;
				break;
			}
		}

	} while(curr.tv_sec < start.tv_sec+SAP_TIMEOUT);

	mreq.imr_multiaddr.s_addr = inet_addr(SAP_ADDR);
	mreq.imr_interface.s_addr = INADDR_ANY;
	setsockopt (fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, &mreq, sizeof(mreq));

	close(fd);

	return url;
}