/*
 *	Copyright 1994, 1995, 2000 Neil Russell.
 *	(See License)
 *	Copyright 2000, 2001 DENX Software Engineering, Wolfgang Denk, wd@denx.de
 */

#include <common.h>
#include <command.h>
#include <net.h>
#ifdef CONFIG_IPV6
#include <net6.h>
#endif
#include "tftp.h"
#include "bootp.h"

#include <bootmenu.h>

#define WELL_KNOWN_PORT	69		/* Well known TFTP port #		*/
#define TIMEOUT		5000UL		/* Millisecs to timeout for lost pkt */
#ifndef	CONFIG_NET_RETRY_COUNT
# define TIMEOUT_COUNT	10		/* # of timeouts before giving up  */
#else
# define TIMEOUT_COUNT  (CONFIG_NET_RETRY_COUNT * 2)
#endif
					/* (for checking the image size)	*/
#define HASHES_PER_LINE	65		/* Number of "loading" hashes per line	*/

/*
 *	TFTP operations.
 */
#define TFTP_RRQ	1
#define TFTP_WRQ	2
#define TFTP_DATA	3
#define TFTP_ACK	4
#define TFTP_ERROR	5
#define TFTP_OACK	6

static ulong TftpTimeoutMSecs = TIMEOUT;
static int TftpTimeoutCountMax = TIMEOUT_COUNT;

/*
 * These globals govern the timeout behavior when attempting a connection to a
 * TFTP server. TftpRRQTimeoutMSecs specifies the number of milliseconds to
 * wait for the server to respond to initial connection. Second global,
 * TftpRRQTimeoutCountMax, gives the number of such connection retries.
 * TftpRRQTimeoutCountMax must be non-negative and TftpRRQTimeoutMSecs must be
 * positive. The globals are meant to be set (and restored) by code needing
 * non-standard timeout behavior when initiating a TFTP transfer.
 */
ulong TftpRRQTimeoutMSecs = TIMEOUT;
int TftpRRQTimeoutCountMax = TIMEOUT_COUNT;

enum {
	TFTP_ERR_UNDEFINED           = 0,
	TFTP_ERR_FILE_NOT_FOUND      = 1,
	TFTP_ERR_ACCESS_DENIED       = 2,
	TFTP_ERR_DISK_FULL           = 3,
	TFTP_ERR_UNEXPECTED_OPCODE   = 4,
	TFTP_ERR_UNKNOWN_TRANSFER_ID  = 5,
	TFTP_ERR_FILE_ALREADY_EXISTS = 6,
};

static IPaddr_t TftpServerIP;
static int	TftpServerPort;		/* The UDP port at their end		*/
static int	TftpOurPort;		/* The UDP port at our end		*/
static int	TftpTimeoutCount;
#ifdef __ATL_CHANGE__
static int	TftpTimeoutBackoff;
#endif
static ulong	TftpBlock;		/* packet sequence number		*/
static ulong	TftpLastBlock;		/* last packet sequence number received */
static ulong	TftpBlockWrap;		/* count of sequence number wraparounds */
static ulong	TftpBlockWrapOffset;	/* memory offset due to wrapping	*/
static int	TftpState;
#ifdef CONFIG_TFTP_TSIZE
static int	TftpTsize;		/* The file size reported by the server */
static short	TftpNumchars;		/* The number of hashes we printed      */
#endif

#define STATE_RRQ	1
#define STATE_DATA	2
#define STATE_TOO_LARGE	3
#define STATE_BAD_MAGIC	4
#define STATE_OACK	5

#define TFTP_BLOCK_SIZE		512		    /* default TFTP block size	*/
#define TFTP_SEQUENCE_SIZE	((ulong)(1<<16))    /* sequence number is 16 bit */

#define DEFAULT_NAME_LEN	(8 + 4 + 1)
static char default_filename[DEFAULT_NAME_LEN];

#ifndef CONFIG_TFTP_FILE_NAME_MAX_LEN
#define MAX_LEN 128
#else
#define MAX_LEN CONFIG_TFTP_FILE_NAME_MAX_LEN
#endif

static char tftp_filename[MAX_LEN];

#ifdef CONFIG_SYS_DIRECT_FLASH_TFTP
extern flash_info_t flash_info[];
#endif

/* 512 is poor choice for ethernet, MTU is typically 1500.
 * Minus eth.hdrs thats 1468.  Can get 2x better throughput with
 * almost-MTU block sizes.  At least try... fall back to 512 if need be.
 * (but those using CONFIG_IP_DEFRAG may want to set a larger block in cfg file)
 */
#ifdef CONFIG_TFTP_BLOCKSIZE
#define TFTP_MTU_BLOCKSIZE CONFIG_TFTP_BLOCKSIZE
#else
#define TFTP_MTU_BLOCKSIZE 1468
#endif

static unsigned short TftpBlkSize=TFTP_BLOCK_SIZE;
static unsigned short TftpBlkSizeOption=TFTP_MTU_BLOCKSIZE;

#ifdef CONFIG_MCAST_TFTP
#include <malloc.h>
#define MTFTP_BITMAPSIZE	0x1000
static unsigned *Bitmap;
static int PrevBitmapHole,Mapsize=MTFTP_BITMAPSIZE;
static uchar ProhibitMcast=0, MasterClient=0;
static uchar Multicast=0;
extern IPaddr_t Mcast_addr;
static int Mcast_port;
static ulong TftpEndingBlock; /* can get 'last' block before done..*/

static void parse_multicast_oack(char *pkt,int len);

static void
mcast_cleanup(void)
{
	if (Mcast_addr) eth_mcast_join(Mcast_addr, 0);
	if (Bitmap) free(Bitmap);
	Bitmap=NULL;
	Mcast_addr = Multicast = Mcast_port = 0;
	TftpEndingBlock = -1;
}

#endif	/* CONFIG_MCAST_TFTP */

static __inline__ void
store_block (unsigned block, uchar * src, unsigned len)
{
	ulong offset = block * TftpBlkSize + TftpBlockWrapOffset;
	ulong newsize = offset + len;
#ifdef CONFIG_SYS_DIRECT_FLASH_TFTP
	int i, rc = 0;

	for (i=0; i<CONFIG_SYS_MAX_FLASH_BANKS; i++) {
		/* start address in flash? */
		if (flash_info[i].flash_id == FLASH_UNKNOWN)
			continue;
		if (load_addr + offset >= flash_info[i].start[0]) {
			rc = 1;
			break;
		}
	}

	if (rc) { /* Flash is destination for this packet */
		rc = flash_write ((char *)src, (ulong)(load_addr+offset), len);
		if (rc) {
			flash_perror (rc);
			NetState = NETLOOP_FAIL;
			return;
		}
	}
	else
#endif /* CONFIG_SYS_DIRECT_FLASH_TFTP */
	{
		(void)memcpy((void *)(load_addr + offset), src, len);
	}
#ifdef CONFIG_MCAST_TFTP
	if (Multicast)
		ext2_set_bit(block, Bitmap);
#endif

	if (NetBootFileXferSize < newsize)
		NetBootFileXferSize = newsize;
}

static void TftpSend (void);
static void TftpTimeout (void);

/**********************************************************************/

static void
TftpSend (void)
{
	volatile uchar *	pkt;
	volatile uchar *	xp;
	int			len = 0;
	volatile ushort *s;

#ifdef CONFIG_MCAST_TFTP
	/* Multicast TFTP.. non-MasterClients do not ACK data. */
	if (Multicast
	 && (TftpState == STATE_DATA)
	 && (MasterClient == 0))
		return;
#endif
	/*
	 *	We will always be sending some sort of packet, so
	 *	cobble together the packet headers now.
	 */
#ifdef CONFIG_IPV6	
	if ( NetIpVersion == 6 )
	{
		pkt = NetTxPacket + NetEthHdrSize() + IP6_HDR_SIZE + IP6_UDPHDR_SIZE;
	} else
#endif
	pkt = NetTxPacket + NetEthHdrSize() + IP_HDR_SIZE;

	switch (TftpState) {

	case STATE_RRQ:
		xp = pkt;
		s = (ushort *)pkt;
		*s++ = htons(TFTP_RRQ);
		pkt = (uchar *)s;
		strcpy ((char *)pkt, tftp_filename);
		pkt += strlen(tftp_filename) + 1;
		strcpy ((char *)pkt, "octet");
		pkt += 5 /*strlen("octet")*/ + 1;
		strcpy ((char *)pkt, "timeout");
		pkt += 7 /*strlen("timeout")*/ + 1;
		sprintf((char *)pkt, "%lu", TftpTimeoutMSecs / 1000);
		debug("send option \"timeout %s\"\n", (char *)pkt);
		pkt += strlen((char *)pkt) + 1;
#ifdef CONFIG_TFTP_TSIZE
		memcpy((char *)pkt, "tsize\0000\0", 8);
		pkt += 8;
#endif
		/* try for more effic. blk size */
		pkt += sprintf((char *)pkt,"blksize%c%d%c",
				0,TftpBlkSizeOption,0);
#ifdef CONFIG_MCAST_TFTP
		/* Check all preconditions before even trying the option */
		if (!ProhibitMcast
		 && (Bitmap=malloc(Mapsize))
		 && eth_get_dev()->mcast) {
			free(Bitmap);
			Bitmap=NULL;
			pkt += sprintf((char *)pkt,"multicast%c%c",0,0);
		}
#endif /* CONFIG_MCAST_TFTP */
		len = pkt - xp;
		break;

	case STATE_OACK:
#ifdef CONFIG_MCAST_TFTP
		/* My turn!  Start at where I need blocks I missed.*/
		if (Multicast)
			TftpBlock=ext2_find_next_zero_bit(Bitmap,(Mapsize*8),0);
		/*..falling..*/
#endif
	case STATE_DATA:
		xp = pkt;
		s = (ushort *)pkt;
		*s++ = htons(TFTP_ACK);
		*s++ = htons(TftpBlock);
		pkt = (uchar *)s;
		len = pkt - xp;
		break;

	case STATE_TOO_LARGE:
		xp = pkt;
		s = (ushort *)pkt;
		*s++ = htons(TFTP_ERROR);
		*s++ = htons(3);
		pkt = (uchar *)s;
		strcpy ((char *)pkt, "File too large");
		pkt += 14 /*strlen("File too large")*/ + 1;
		len = pkt - xp;
		break;

	case STATE_BAD_MAGIC:
		xp = pkt;
		s = (ushort *)pkt;
		*s++ = htons(TFTP_ERROR);
		*s++ = htons(2);
		pkt = (uchar *)s;
		strcpy ((char *)pkt, "File has bad magic");
		pkt += 18 /*strlen("File has bad magic")*/ + 1;
		len = pkt - xp;
		break;
	}

#ifdef CONFIG_IPV6	
	if ( NetIpVersion == 6 )
	{
		NetSendUDPPacket6(NetServerEther, &NetServerIP6, TftpServerPort, TftpOurPort, len);
	} else
#endif
	NetSendUDPPacket(NetServerEther, TftpServerIP, TftpServerPort, TftpOurPort, len);
}


static void
TftpHandler (uchar * pkt, unsigned dest, unsigned src, unsigned len)
{
	ushort proto;
	ushort *s;
	int i;

	if (dest != TftpOurPort) {
#ifdef CONFIG_MCAST_TFTP
		if (Multicast
		 && (!Mcast_port || (dest != Mcast_port)))
#endif
		return;
	}
	if (TftpState != STATE_RRQ && src != TftpServerPort) {
		return;
	}

	if (len < 2) {
		return;
	}
	len -= 2;
	/* warning: don't use increment (++) in ntohs() macros!! */
	s = (ushort *)pkt;
	proto = *s++;
	pkt = (uchar *)s;
	switch (ntohs(proto)) {

	case TFTP_RRQ:
	case TFTP_WRQ:
	case TFTP_ACK:
		break;
	default:
		break;

	case TFTP_OACK:
		debug("Got OACK: %s %s\n",
			pkt,
			pkt + strlen((char *)pkt) + 1);
		TftpState = STATE_OACK;
		TftpServerPort = src;
		/*
		 * Check for 'blksize' option.
		 * Careful: "i" is signed, "len" is unsigned, thus
		 * something like "len-8" may give a *huge* number
		 */
		for (i=0; i+8<len; i++) {
			if (strcmp ((char*)pkt+i,"blksize") == 0) {
				TftpBlkSize = (unsigned short)
					simple_strtoul((char*)pkt+i+8,NULL,10);
				debug("Blocksize ack: %s, %d\n",
					(char*)pkt+i+8,TftpBlkSize);
			}
#ifdef CONFIG_TFTP_TSIZE
			if (strcmp ((char*)pkt+i,"tsize") == 0) {
				TftpTsize = simple_strtoul((char*)pkt+i+6,NULL,10);
				debug("size = %s, %d\n",
					 (char*)pkt+i+6, TftpTsize);
			}
#endif
		}
#ifdef CONFIG_MCAST_TFTP
		parse_multicast_oack((char *)pkt,len-1);
		if ((Multicast) && (!MasterClient))
			TftpState = STATE_DATA;	/* passive.. */
		else
#endif
		TftpSend (); /* Send ACK */
		break;
	case TFTP_DATA:
		if (len < 2)
			return;
		len -= 2;
		TftpBlock = ntohs(*(ushort *)pkt);

		/*
		 * RFC1350 specifies that the first data packet will
		 * have sequence number 1. If we receive a sequence
		 * number of 0 this means that there was a wrap
		 * around of the (16 bit) counter.
		 */
		if (TftpBlock == 0) {
			TftpBlockWrap++;
			TftpBlockWrapOffset += TftpBlkSize * TFTP_SEQUENCE_SIZE;
			printf ("\n\t %lu MB received\n\t ", TftpBlockWrapOffset>>20);
		}
#ifdef CONFIG_TFTP_TSIZE
		else if (TftpTsize) {
			while (TftpNumchars < NetBootFileXferSize * 50 / TftpTsize) {
				putc('#');
				TftpNumchars++;
			}
		}
#endif
		else {
			if (((TftpBlock - 1) % 10) == 0) {
				putc ('#');
			} else if ((TftpBlock % (10 * HASHES_PER_LINE)) == 0) {
				puts ("\n\t ");
			}
		}

		if (TftpState == STATE_RRQ)
			debug("Server did not acknowledge timeout option!\n");

		if (TftpState == STATE_RRQ || TftpState == STATE_OACK) {
			/* first block received */
			TftpState = STATE_DATA;
			TftpServerPort = src;
			TftpLastBlock = 0;
			TftpBlockWrap = 0;
			TftpBlockWrapOffset = 0;

#ifdef CONFIG_MCAST_TFTP
			if (Multicast) { /* start!=1 common if mcast */
				TftpLastBlock = TftpBlock - 1;
			} else
#endif
			if (TftpBlock != 1) {	/* Assertion */
				printf ("\nTFTP error: "
					"First block is not block 1 (%ld)\n"
					"Starting again\n\n",
					TftpBlock);
				NetStartAgain ();
				break;
			}
		}

		if (TftpBlock == TftpLastBlock) {
			/*
			 *	Same block again; ignore it.
			 */
			break;
		}

		TftpLastBlock = TftpBlock;
		TftpTimeoutCountMax = TIMEOUT_COUNT;
#ifdef __ATL_CHANGE__
		// Exponential backoff for timeout
		if (TftpTimeoutBackoff > 0) {
			TftpTimeoutBackoff--;
		}
		NetSetTimeout ((CONFIG_SYS_HZ/4) << TftpTimeoutBackoff, TftpTimeout);
#else
		NetSetTimeout (TftpTimeoutMSecs, TftpTimeout);
#endif

		store_block (TftpBlock - 1, pkt + 2, len);

		/*
		 *	Acknoledge the block just received, which will prompt
		 *	the server for the next one.
		 */
#ifdef CONFIG_MCAST_TFTP
		/* if I am the MasterClient, actively calculate what my next
		 * needed block is; else I'm passive; not ACKING
		 */
		if (Multicast) {
			if (len < TftpBlkSize)  {
				TftpEndingBlock = TftpBlock;
			} else if (MasterClient) {
				TftpBlock = PrevBitmapHole =
					ext2_find_next_zero_bit(
						Bitmap,
						(Mapsize*8),
						PrevBitmapHole);
				if (TftpBlock > ((Mapsize*8) - 1)) {
					printf ("tftpfile too big\n");
					/* try to double it and retry */
					Mapsize<<=1;
					mcast_cleanup();
					NetStartAgain ();
					return;
				}
				TftpLastBlock = TftpBlock;
			}
		}
#endif
		TftpSend ();

#ifdef CONFIG_MCAST_TFTP
		if (Multicast) {
			if (MasterClient && (TftpBlock >= TftpEndingBlock)) {
				puts ("\nMulticast tftp done\n");
				mcast_cleanup();
				NetState = NETLOOP_SUCCESS;
			}
		}
		else
#endif
		if (len < TftpBlkSize) {
			/*
			 *	We received the whole thing.  Try to
			 *	run it.
			 */
#ifdef CONFIG_TFTP_TSIZE
			/* Print out the hash marks for the last packet received */
			while (TftpTsize && TftpNumchars < 49) {
				putc('#');
				TftpNumchars++;
			}
#endif
			puts ("\ndone\n");
			NetState = NETLOOP_SUCCESS;
		}
		break;

	case TFTP_ERROR:
		printf ("\nTFTP error: '%s' (%d)\n",
					pkt + 2, ntohs(*(ushort *)pkt));
#ifdef CONFIG_BOOTMENU
		bootmenu_tftp_error((char *)pkt + 2, ntohs(*(ushort *)pkt));
#endif

		switch (ntohs(*(ushort *)pkt)) {
		case TFTP_ERR_FILE_NOT_FOUND:
		case TFTP_ERR_ACCESS_DENIED:
			puts("Not retrying...\n");
			eth_halt();
			NetState = NETLOOP_FAIL;
			break;
		case TFTP_ERR_UNDEFINED:
		case TFTP_ERR_DISK_FULL:
		case TFTP_ERR_UNEXPECTED_OPCODE:
		case TFTP_ERR_UNKNOWN_TRANSFER_ID:
		case TFTP_ERR_FILE_ALREADY_EXISTS:
		default:
			puts("Starting again\n\n");
#ifdef CONFIG_MCAST_TFTP
			mcast_cleanup();
#endif
			NetStartAgain();
			break;
		}
		break;
	}
}


static void
TftpTimeout (void)
{
#ifdef __ATL_CHANGE__
	// Exponential backoff for timeout
	{	int t = (CONFIG_SYS_HZ / 4) << TftpTimeoutBackoff;
		// TIMEOUT defined in ms need to convert back to secs
		int timeout_sec  = TIMEOUT / 1000;
		if (t < timeout_sec * CONFIG_SYS_HZ) {
			TftpTimeoutBackoff++;
			NetSetTimeout (t, TftpTimeout);
			TftpSend ();
			return;
		}
		if (TftpTimeoutBackoff > 0) {
			TftpTimeoutBackoff--;
		}
	}
#endif
	if (++TftpTimeoutCount > TftpTimeoutCountMax) {
		puts ("\nRetry count exceeded; starting again\n");
#ifdef CONFIG_BOOTMENU
		bootmenu_tftp_timeout(-1);
#endif
#ifdef CONFIG_MCAST_TFTP
		mcast_cleanup();
#endif
		NetStartAgain ();
	} else {
		puts ("T ");
#ifdef CONFIG_BOOTMENU
		bootmenu_tftp_timeout(TftpTimeoutCount);
#endif
#ifdef __ATL_CHANGE__
		NetSetTimeout ((CONFIG_SYS_HZ/4) << TftpTimeoutBackoff, TftpTimeout);
#else
		NetSetTimeout (TftpTimeoutMSecs, TftpTimeout);
#endif
		TftpSend ();
	}
}


void
TftpStart (void)
{
	char *ep;             /* Environment pointer */

	/*
	 * Allow the user to choose TFTP blocksize and timeout.
	 * TFTP protocol has a minimal timeout of 1 second.
	 */
	if ((ep = getenv("tftpblocksize")) != NULL)
		TftpBlkSizeOption = simple_strtol(ep, NULL, 10);

	if ((ep = getenv("tftptimeout")) != NULL)
		TftpTimeoutMSecs = simple_strtol(ep, NULL, 10);

	if (TftpTimeoutMSecs < 1000) {
		printf("TFTP timeout (%ld ms) too low, "
			"set minimum = 1000 ms\n",
			TftpTimeoutMSecs);
		TftpTimeoutMSecs = 1000;
	}

	debug("TFTP blocksize = %i, timeout = %ld ms\n",
		TftpBlkSizeOption, TftpTimeoutMSecs);

	TftpServerIP = NetServerIP;
	if (BootFile[0] == '\0') {
		sprintf(default_filename, "%02lX%02lX%02lX%02lX.img",
			NetOurIP & 0xFF,
			(NetOurIP >>  8) & 0xFF,
			(NetOurIP >> 16) & 0xFF,
			(NetOurIP >> 24) & 0xFF	);

		strncpy(tftp_filename, default_filename, MAX_LEN);
		tftp_filename[MAX_LEN-1] = 0;

		printf ("*** Warning: no boot file name; using '%s'\n",
			tftp_filename);
	} else {
		char *p = strchr (BootFile, ':');

		if (p == NULL) {
			strncpy(tftp_filename, BootFile, MAX_LEN);
			tftp_filename[MAX_LEN-1] = 0;
		} else {
			TftpServerIP = string_to_ip (BootFile);
			strncpy(tftp_filename, p + 1, MAX_LEN);
			tftp_filename[MAX_LEN-1] = 0;
		}
	}

#if defined(CONFIG_NET_MULTI)
	printf ("Using %s device\n", eth_get_name());
#endif
#ifdef CONFIG_IPV6	
	if ( NetIpVersion == 6 ) {
		puts ("TFTP from server ");
		print_IP6addr (&NetServerIP6);
		puts ("; our IP address is ");
		print_IP6addr (&NetOurIP6);
	}
	else
#endif
	printf("TFTP from server %pI4"
		"; our IP address is %pI4", &TftpServerIP, &NetOurIP);

	/* Check if we need to send across this subnet */
#ifdef CONFIG_IPV6
	if ( (NetIpVersion == 6) || (strcmp (getenv("ipversion") ? getenv("ipversion") : "4", "6") == 0) )
	{
		if ( !ip6_addr_in_subnet(&NetOurIP6, &NetServerIP6, NetPrefixLength) )
		{
			puts ("; sending through gateway ");
			print_IP6addr (&NetOurGatewayIP6) ;
		}
	} else
#endif /* CONFIG_IPV6 */
	if (NetOurGatewayIP && NetOurSubnetMask) {
	    IPaddr_t OurNet	= NetOurIP    & NetOurSubnetMask;
	    IPaddr_t ServerNet	= TftpServerIP & NetOurSubnetMask;

	    if (OurNet != ServerNet)
		printf("; sending through gateway %pI4", &NetOurGatewayIP);
	}
	       
	putc ('\n');

	printf ("Filename '%s'.", tftp_filename);

	if (NetBootFileSize) {
		printf (" Size is 0x%x Bytes = ", NetBootFileSize<<9);
		print_size (NetBootFileSize<<9, "");
	}

	putc ('\n');

	printf ("Load address: 0x%lx\n", load_addr);

	puts ("Loading: *\b");

	TftpTimeoutCountMax = TftpRRQTimeoutCountMax;

#ifdef __ATL_CHANGE__
	NetSetTimeout (CONFIG_SYS_HZ, TftpTimeout);	// 1 second for first timeout
	TftpTimeoutBackoff = 0;
#else
	NetSetTimeout (TftpTimeoutMSecs, TftpTimeout);
#endif
	NetSetHandler (TftpHandler);

	TftpServerPort = WELL_KNOWN_PORT;
	TftpTimeoutCount = 0;
	TftpState = STATE_RRQ;
	/* Use a pseudo-random port unless a specific port is set */
	TftpOurPort = 1024 + (get_timer(0) % 3072);

#ifdef CONFIG_TFTP_PORT
	if ((ep = getenv("tftpdstp")) != NULL) {
		TftpServerPort = simple_strtol(ep, NULL, 10);
	}
	if ((ep = getenv("tftpsrcp")) != NULL) {
		TftpOurPort= simple_strtol(ep, NULL, 10);
	}
#endif
	TftpBlock = 0;

	/* zero out server ether in case the server ip has changed */
	memset(NetServerEther, 0, 6);
	/* Revert TftpBlkSize to dflt */
	TftpBlkSize = TFTP_BLOCK_SIZE;
#ifdef CONFIG_MCAST_TFTP
	mcast_cleanup();
#endif
#ifdef CONFIG_TFTP_TSIZE
	TftpTsize = 0;
	TftpNumchars = 0;
#endif

	TftpSend ();
}

#ifdef CONFIG_MCAST_TFTP
/* Credits: atftp project.
 */

/* pick up BcastAddr, Port, and whether I am [now] the master-client. *
 * Frame:
 *    +-------+-----------+---+-------~~-------+---+
 *    |  opc  | multicast | 0 | addr, port, mc | 0 |
 *    +-------+-----------+---+-------~~-------+---+
 * The multicast addr/port becomes what I listen to, and if 'mc' is '1' then
 * I am the new master-client so must send ACKs to DataBlocks.  If I am not
 * master-client, I'm a passive client, gathering what DataBlocks I may and
 * making note of which ones I got in my bitmask.
 * In theory, I never go from master->passive..
 * .. this comes in with pkt already pointing just past opc
 */
static void parse_multicast_oack(char *pkt, int len)
{
 int i;
 IPaddr_t addr;
 char *mc_adr, *port,  *mc;

	mc_adr=port=mc=NULL;
	/* march along looking for 'multicast\0', which has to start at least
	 * 14 bytes back from the end.
	 */
	for (i=0;i<len-14;i++)
		if (strcmp (pkt+i,"multicast") == 0)
			break;
	if (i >= (len-14)) /* non-Multicast OACK, ign. */
		return;

	i+=10; /* strlen multicast */
	mc_adr = pkt+i;
	for (;i<len;i++) {
		if (*(pkt+i) == ',') {
			*(pkt+i) = '\0';
			if (port) {
				mc = pkt+i+1;
				break;
			} else {
				port = pkt+i+1;
			}
		}
	}
	if (!port || !mc_adr || !mc ) return;
	if (Multicast && MasterClient) {
		printf ("I got a OACK as master Client, WRONG!\n");
		return;
	}
	/* ..I now accept packets destined for this MCAST addr, port */
	if (!Multicast) {
		if (Bitmap) {
			printf ("Internal failure! no mcast.\n");
			free(Bitmap);
			Bitmap=NULL;
			ProhibitMcast=1;
			return ;
		}
		/* I malloc instead of pre-declare; so that if the file ends
		 * up being too big for this bitmap I can retry
		 */
		if (!(Bitmap = malloc (Mapsize))) {
			printf ("No Bitmap, no multicast. Sorry.\n");
			ProhibitMcast=1;
			return;
		}
		memset (Bitmap,0,Mapsize);
		PrevBitmapHole = 0;
		Multicast = 1;
	}
	addr = string_to_ip(mc_adr);
	if (Mcast_addr != addr) {
		if (Mcast_addr)
			eth_mcast_join(Mcast_addr, 0);
		if (eth_mcast_join(Mcast_addr=addr, 1)) {
			printf ("Fail to set mcast, revert to TFTP\n");
			ProhibitMcast=1;
			mcast_cleanup();
			NetStartAgain();
		}
	}
	MasterClient = (unsigned char)simple_strtoul((char *)mc,NULL,10);
	Mcast_port = (unsigned short)simple_strtoul(port,NULL,10);
	printf ("Multicast: %s:%d [%d]\n", mc_adr, Mcast_port, MasterClient);
	return;
}

#endif /* Multicast TFTP */
