pmtp.h

开源的组播程序

#include <netinet/in.h>
#include <sys/time.h>

/*
 * Used in the (rather primitive) traffic shaper to smooth out traffic bursts
 */
#define SMOOTHING_SECONDS 5

/*
 * This must be set to at least 255 becode each encoding run results
 * in 255 packets
 */
#define MAX_PACKET_BUFFER_SIZE	300

/* 
 * The only parameter to tweak here is NROOTS. NROOTS specifies how
 * many packets can be lost out of the NN=255 packets for the decoder
 * to still be able to recover the original data. Note that this also
 * affects the overhead which is (NROOTS/NN)%.
 * DON'T FIDDLE with the other paramters as this will kill the codec.
 */
#define NN 255
#define SYMSIZE 8
#define GENPOLY 0x187
#define FCS 1
#define PRIM 1
#define NROOTS 8

#define IP_HEADER_SIZE			20
#define UDP_HEADER_SIZE			8
#define PMTP_HEADER_SIZE		8

/* 
 * PMTP_BITRATE controls the sending rate of sendfile. This must be
 * set to a multiple of 8000.
 */
#define PMTP_BITRATE			64000
/*
 * PMTP_PAYLOAD should be as big as possible but because UDP is used
 * care must be taken that the path mtu supports the payload size. So
 * watch out for those GRE/IPSEC tunnels!
 */
#define PMTP_PAYLOAD			1400

/*
 * This is the maximum packets of a new segment that we receive before
 * we start processing the current (incomplete) segment
 */
#define MAX_PACKETS_LOST	NROOTS

/* 
 * With PMTP_SIMULATE_ERRORS you can simulate packet-loss. Set to 0 to disable.
 */
#define PMTP_SIMULATE_ERRORS	4

/* 
 * The group and port to which a session is multicasted. Note that
 * we don't use the SSM range (232.0.0.0/8) yet because we don't support
 * IGMPv3 yet
 */
#define PMTP_GROUP	"233.5.5.5"
#define PMTP_PORT	12001

/*
 * When computing tigertrees, how big are the chunks of a file that we
 * process at a time
 */
#define TIGERTREE_CHUNKSIZE		256000

/*
 * These are the different debugging levels. `OR' them together to set
 * the DEBUG level
 */
#define DEBUG 4163

#define DEBUG_ERASURES			1
#define DEBUG_PACKETS_MISSED	2
#define DEBUG_PACKETS_RECEIVED	4
#define DEBUG_CODING			8
#define DEBUG_BLOCKS			16
#define DEBUG_CODING_DUMP		32
#define DEBUG_SEGMENTS			64
#define DEBUG_PACKETS_SENT		128

#define DEBUG_BUFFER_ADD		256
#define DEBUG_BUFFER_TRANSMIT	512
#define DEBUG_BUFFER_REMOVE		1024
#define DEBUG_UPLOAD_PROCESSING	2048
#define DEBUG_PMSP				4096
#define DEBUG_PACKETS_SHA		8192
#define DEBUG_SEGMENTS_SHA		16384

/*
 * This defines the header off-sets for the PMTP and PMSP packets. Don't
 * mess with them.
 */
#define PMTP_HEADER_PACKETID	0
#define PMTP_HEADER_SESSIONID	2	
#define PMTP_HEADER_SEGMENTID	4

#define PMSP_HEADER_VERSION			0
#define PMSP_HEADER_CODINGID		0
#define PMSP_HEADER_SESSIONID		2
#define PMSP_HEADER_PAYLOAD			4
#define PMSP_HEADER_START			6
#define PMSP_HEADER_SOURCE			8
#define PMSP_HEADER_GROUP			12
#define PMSP_HEADER_PORT			16
#define PMSP_HEADER_BITRATE			18
#define PMSP_HEADER_FILESIZE		20
#define PMSP_HEADER_FILETIGERTREE	28
#define PMSP_HEADER_PARTOFFSET		52
#define PMSP_HEADER_PARTLENGTH		56
#define PMSP_HEADER_PARTTIGERTREE	60
#define PMSP_HEADER_FILENAME		84

/* 
 * State mechanism for sessions. Immature & incomplete
 */
#define PMSP_STATE_INIT				1	/* No session info received yet */
#define PMSP_STATE_INVALID			2	/* Invalid session info */
#define PMSP_STATE_CONFLICT			4	/* Conflicting info for session id */
#define PMSP_STATE_LEARNED			8	/* Received session information */
#define PMSP_STATE_ACTIVE			16	/* Download of session has started */
#define PMSP_STATE_COMPLETED		32	/* Download has been completed */
#define PMSP_STATE_FAILED			64	/* Download has failed */

/* 
 * Used by traffic shaper
 */
struct packet {
	unsigned char *packet;
	uint16_t length;
};

/* 
 * Used by traffic shaper
 */
struct packet_buffer {
	struct packet **packets;
	uint16_t size;
};

/*
 * This defines a session. Perhaps it should be renamed. Matches mostly
 * with the PMSP header, except for the socket family and protocol.
 */
struct pmsp_header {
	uint8_t status;
	uint8_t version : 4;
	uint16_t codingid : 12;
	uint16_t sessionid;
	uint16_t payload;
	uint16_t start;
	sa_family_t family;
	uint32_t source;
	uint32_t group;
	uint16_t protocol;
	uint16_t port;
	uint32_t bitrate;
	uint64_t filesize;
	unsigned char file_tigertree[24], part_tigertree[24];
	uint32_t partoffset, partlength;
	unsigned char filename[128];
};

/*
 * Each upload is represented with this information. Used a.o. by the
 * traffic shaper
 */
struct pmtp_upload {
	struct timeval previous_invocation;
	uint32_t bytes_sent;
	uint32_t bytes_sent_interval;
	uint32_t credits;
	uint32_t packets_sent;
	int s;
	struct sockaddr_in s_in;
	int fd;
	struct packet_buffer buffer;
	struct pmsp_header session;
};

/* 
 * The receiver receives traffic from multiple segments while downloading
 * because packets can be lost or re-ordered. Each segment is tracked
 * in the pmtp_segment structure
 */
struct pmtp_segment {
	uint32_t segmentid;
	uint32_t packets_received;		/* duplicates are not counted here */
	uint32_t duplicate_packets;
	uint8_t  received_packets[NN];
	uint16_t payload_size;
	unsigned char *packets;
	void *codec;
};

/*
 * Header Encoding / decoding functions
 */
uint8_t decode_header_8 (unsigned char* header);
uint16_t decode_header_16 (unsigned char* header);
uint32_t decode_header_32 (unsigned char* header);

uint8_t encode_header_8 (unsigned char* header, uint8_t value);
uint16_t encode_header_16 (unsigned char* header, uint16_t value);
uint32_t encode_header_32 (unsigned char* header, uint32_t value);

/*
 * Tiger Tree functions
 */

uint64_t get_tigertree (unsigned char *tt, unsigned char *filename,
		uint64_t offset, uint64_t length);

/*
 * Reed-Solomon Encoding / decoding functions for PMTP segments
 */
uint32_t init_segment (struct pmtp_segment *segment, void *codec);
uint32_t free_segment (struct pmtp_segment *segment);
uint8_t * encode_segment (struct pmtp_segment *segment, uint8_t nroots);
uint32_t decode_segment (struct pmtp_segment *segment, int fd,
        uint16_t nroots, uint32_t bytes_left);
int32_t buffer_segment(struct pmtp_upload *upload,struct pmtp_segment *segment);


uint16_t init_packet_buffer (struct packet_buffer *buffer);
uint16_t free_packet_buffer (struct packet_buffer *buffer);
int16_t buffer_packet (struct packet_buffer *buffer, unsigned char *packet,
		uint16_t length);
uint16_t send_buffer (int s, struct sockaddr_in *s_in,
		struct packet_buffer *buffer, uint32_t budget,
		 uint32_t *packets, uint32_t *bytes_sent);
uint16_t remove_packet (struct packet_buffer *buffer, uint16_t position);
void send_packet (int s, struct sockaddr_in *s_in, unsigned char *packet,
	uint16_t length);
uint16_t buffer_packets_free (struct packet_buffer *buffer);

/*
 * Misc functions
 */
off_t get_filesize (const unsigned char *filename);

/*
 * Debugging related functions
 */
unsigned char * get_printable_hex (unsigned char *dest, unsigned char *string,
		uint16_t length);
unsigned char * get_printable_sha (unsigned char *dest,
        unsigned char *string, uint16_t length);