strip.c

linux-2.6.15.6

/*
 * Maximum Starmode packet length is 1183 bytes. Allowing 4 bytes for
 * protocol key, 4 bytes for checksum, one byte for CR, and 65/64 expansion
 * for STRIP encoding, that translates to a maximum payload MTU of 1155.
 * Note: A standard NFS 1K data packet is a total of 0x480 (1152) bytes
 * long, including IP header, UDP header, and NFS header. Setting the STRIP
 * MTU to 1152 allows us to send default sized NFS packets without fragmentation.
 */
static const unsigned short MAX_SEND_MTU = 1152;
static const unsigned short MAX_RECV_MTU = 1500;	/* Hoping for Ethernet sized packets in the future! */
static const unsigned short DEFAULT_STRIP_MTU = 1152;
static const int STRIP_MAGIC = 0x5303;
static const long LongTime = 0x7FFFFFFF;

/************************************************************************/
/* Global variables							*/

static LIST_HEAD(strip_list);
static DEFINE_SPINLOCK(strip_lock);

/************************************************************************/
/* Macros								*/

/* Returns TRUE if text T begins with prefix P */
#define has_prefix(T,L,P) (((L) >= sizeof(P)-1) && !strncmp((T), (P), sizeof(P)-1))

/* Returns TRUE if text T of length L is equal to string S */
#define text_equal(T,L,S) (((L) == sizeof(S)-1) && !strncmp((T), (S), sizeof(S)-1))

#define READHEX(X) ((X)>='0' && (X)<='9' ? (X)-'0' :      \
                    (X)>='a' && (X)<='f' ? (X)-'a'+10 :   \
                    (X)>='A' && (X)<='F' ? (X)-'A'+10 : 0 )

#define READHEX16(X) ((__u16)(READHEX(X)))

#define READDEC(X) ((X)>='0' && (X)<='9' ? (X)-'0' : 0)

#define ARRAY_END(X) (&((X)[ARRAY_SIZE(X)]))

#define JIFFIE_TO_SEC(X) ((X) / HZ)


/************************************************************************/
/* Utility routines							*/

static int arp_query(unsigned char *haddr, u32 paddr,
		     struct net_device *dev)
{
	struct neighbour *neighbor_entry;

	neighbor_entry = neigh_lookup(&arp_tbl, &paddr, dev);

	if (neighbor_entry != NULL) {
		neighbor_entry->used = jiffies;
		if (neighbor_entry->nud_state & NUD_VALID) {
			memcpy(haddr, neighbor_entry->ha, dev->addr_len);
			return 1;
		}
	}
	return 0;
}

static void DumpData(char *msg, struct strip *strip_info, __u8 * ptr,
		     __u8 * end)
{
	static const int MAX_DumpData = 80;
	__u8 pkt_text[MAX_DumpData], *p = pkt_text;

	*p++ = '\"';

	while (ptr < end && p < &pkt_text[MAX_DumpData - 4]) {
		if (*ptr == '\\') {
			*p++ = '\\';
			*p++ = '\\';
		} else {
			if (*ptr >= 32 && *ptr <= 126) {
				*p++ = *ptr;
			} else {
				sprintf(p, "\\%02X", *ptr);
				p += 3;
			}
		}
		ptr++;
	}

	if (ptr == end)
		*p++ = '\"';
	*p++ = 0;

	printk(KERN_INFO "%s: %-13s%s\n", strip_info->dev->name, msg, pkt_text);
}


/************************************************************************/
/* Byte stuffing/unstuffing routines					*/

/* Stuffing scheme:
 * 00    Unused (reserved character)
 * 01-3F Run of 2-64 different characters
 * 40-7F Run of 1-64 different characters plus a single zero at the end
 * 80-BF Run of 1-64 of the same character
 * C0-FF Run of 1-64 zeroes (ASCII 0)
 */

typedef enum {
	Stuff_Diff = 0x00,
	Stuff_DiffZero = 0x40,
	Stuff_Same = 0x80,
	Stuff_Zero = 0xC0,
	Stuff_NoCode = 0xFF,	/* Special code, meaning no code selected */

	Stuff_CodeMask = 0xC0,
	Stuff_CountMask = 0x3F,
	Stuff_MaxCount = 0x3F,
	Stuff_Magic = 0x0D	/* The value we are eliminating */
} StuffingCode;

/* StuffData encodes the data starting at "src" for "length" bytes.
 * It writes it to the buffer pointed to by "dst" (which must be at least
 * as long as 1 + 65/64 of the input length). The output may be up to 1.6%
 * larger than the input for pathological input, but will usually be smaller.
 * StuffData returns the new value of the dst pointer as its result.
 * "code_ptr_ptr" points to a "__u8 *" which is used to hold encoding state
 * between calls, allowing an encoded packet to be incrementally built up
 * from small parts. On the first call, the "__u8 *" pointed to should be
 * initialized to NULL; between subsequent calls the calling routine should
 * leave the value alone and simply pass it back unchanged so that the
 * encoder can recover its current state.
 */

#define StuffData_FinishBlock(X) \
(*code_ptr = (X) ^ Stuff_Magic, code = Stuff_NoCode)

static __u8 *StuffData(__u8 * src, __u32 length, __u8 * dst,
		       __u8 ** code_ptr_ptr)
{
	__u8 *end = src + length;
	__u8 *code_ptr = *code_ptr_ptr;
	__u8 code = Stuff_NoCode, count = 0;

	if (!length)
		return (dst);

	if (code_ptr) {
		/*
		 * Recover state from last call, if applicable
		 */
		code = (*code_ptr ^ Stuff_Magic) & Stuff_CodeMask;
		count = (*code_ptr ^ Stuff_Magic) & Stuff_CountMask;
	}

	while (src < end) {
		switch (code) {
			/* Stuff_NoCode: If no current code, select one */
		case Stuff_NoCode:
			/* Record where we're going to put this code */
			code_ptr = dst++;
			count = 0;	/* Reset the count (zero means one instance) */
			/* Tentatively start a new block */
			if (*src == 0) {
				code = Stuff_Zero;
				src++;
			} else {
				code = Stuff_Same;
				*dst++ = *src++ ^ Stuff_Magic;
			}
			/* Note: We optimistically assume run of same -- */
			/* which will be fixed later in Stuff_Same */
			/* if it turns out not to be true. */
			break;

			/* Stuff_Zero: We already have at least one zero encoded */
		case Stuff_Zero:
			/* If another zero, count it, else finish this code block */
			if (*src == 0) {
				count++;
				src++;
			} else {
				StuffData_FinishBlock(Stuff_Zero + count);
			}
			break;

			/* Stuff_Same: We already have at least one byte encoded */
		case Stuff_Same:
			/* If another one the same, count it */
			if ((*src ^ Stuff_Magic) == code_ptr[1]) {
				count++;
				src++;
				break;
			}
			/* else, this byte does not match this block. */
			/* If we already have two or more bytes encoded, finish this code block */
			if (count) {
				StuffData_FinishBlock(Stuff_Same + count);
				break;
			}
			/* else, we only have one so far, so switch to Stuff_Diff code */
			code = Stuff_Diff;
			/* and fall through to Stuff_Diff case below
			 * Note cunning cleverness here: case Stuff_Diff compares 
			 * the current character with the previous two to see if it
			 * has a run of three the same. Won't this be an error if
			 * there aren't two previous characters stored to compare with?
			 * No. Because we know the current character is *not* the same
			 * as the previous one, the first test below will necessarily
			 * fail and the send half of the "if" won't be executed.
			 */

			/* Stuff_Diff: We have at least two *different* bytes encoded */
		case Stuff_Diff:
			/* If this is a zero, must encode a Stuff_DiffZero, and begin a new block */
			if (*src == 0) {
				StuffData_FinishBlock(Stuff_DiffZero +
						      count);
			}
			/* else, if we have three in a row, it is worth starting a Stuff_Same block */
			else if ((*src ^ Stuff_Magic) == dst[-1]
				 && dst[-1] == dst[-2]) {
				/* Back off the last two characters we encoded */
				code += count - 2;
				/* Note: "Stuff_Diff + 0" is an illegal code */
				if (code == Stuff_Diff + 0) {
					code = Stuff_Same + 0;
				}
				StuffData_FinishBlock(code);
				code_ptr = dst - 2;
				/* dst[-1] already holds the correct value */
				count = 2;	/* 2 means three bytes encoded */
				code = Stuff_Same;
			}
			/* else, another different byte, so add it to the block */
			else {
				*dst++ = *src ^ Stuff_Magic;
				count++;
			}
			src++;	/* Consume the byte */
			break;
		}
		if (count == Stuff_MaxCount) {
			StuffData_FinishBlock(code + count);
		}
	}
	if (code == Stuff_NoCode) {
		*code_ptr_ptr = NULL;
	} else {
		*code_ptr_ptr = code_ptr;
		StuffData_FinishBlock(code + count);
	}
	return (dst);
}

/*
 * UnStuffData decodes the data at "src", up to (but not including) "end".
 * It writes the decoded data into the buffer pointed to by "dst", up to a
 * maximum of "dst_length", and returns the new value of "src" so that a
 * follow-on call can read more data, continuing from where the first left off.
 * 
 * There are three types of results:
 * 1. The source data runs out before extracting "dst_length" bytes:
 *    UnStuffData returns NULL to indicate failure.
 * 2. The source data produces exactly "dst_length" bytes:
 *    UnStuffData returns new_src = end to indicate that all bytes were consumed.
 * 3. "dst_length" bytes are extracted, with more remaining.
 *    UnStuffData returns new_src < end to indicate that there are more bytes
 *    to be read.
 * 
 * Note: The decoding may be destructive, in that it may alter the source
 * data in the process of decoding it (this is necessary to allow a follow-on
 * call to resume correctly).
 */

static __u8 *UnStuffData(__u8 * src, __u8 * end, __u8 * dst,
			 __u32 dst_length)
{
	__u8 *dst_end = dst + dst_length;
	/* Sanity check */
	if (!src || !end || !dst || !dst_length)
		return (NULL);
	while (src < end && dst < dst_end) {
		int count = (*src ^ Stuff_Magic) & Stuff_CountMask;
		switch ((*src ^ Stuff_Magic) & Stuff_CodeMask) {
		case Stuff_Diff:
			if (src + 1 + count >= end)
				return (NULL);
			do {
				*dst++ = *++src ^ Stuff_Magic;
			}
			while (--count >= 0 && dst < dst_end);
			if (count < 0)
				src += 1;
			else {
				if (count == 0)
					*src = Stuff_Same ^ Stuff_Magic;
				else
					*src =
					    (Stuff_Diff +
					     count) ^ Stuff_Magic;
			}
			break;
		case Stuff_DiffZero:
			if (src + 1 + count >= end)
				return (NULL);
			do {
				*dst++ = *++src ^ Stuff_Magic;
			}
			while (--count >= 0 && dst < dst_end);
			if (count < 0)
				*src = Stuff_Zero ^ Stuff_Magic;
			else
				*src =
				    (Stuff_DiffZero + count) ^ Stuff_Magic;
			break;
		case Stuff_Same:
			if (src + 1 >= end)
				return (NULL);
			do {
				*dst++ = src[1] ^ Stuff_Magic;
			}
			while (--count >= 0 && dst < dst_end);
			if (count < 0)
				src += 2;
			else
				*src = (Stuff_Same + count) ^ Stuff_Magic;
			break;
		case Stuff_Zero:
			do {
				*dst++ = 0;
			}
			while (--count >= 0 && dst < dst_end);
			if (count < 0)
				src += 1;
			else
				*src = (Stuff_Zero + count) ^ Stuff_Magic;
			break;
		}
	}
	if (dst < dst_end)
		return (NULL);
	else
		return (src);
}


/************************************************************************/
/* General routines for STRIP						*/

/*
 * get_baud returns the current baud rate, as one of the constants defined in
 * termbits.h
 * If the user has issued a baud rate override using the 'setserial' command
 * and the logical current rate is set to 38.4, then the true baud rate
 * currently in effect (57.6 or 115.2) is returned.
 */
static unsigned int get_baud(struct tty_struct *tty)
{
	if (!tty || !tty->termios)
		return (0);
	if ((tty->termios->c_cflag & CBAUD) == B38400 && tty->driver_data) {
		struct async_struct *info =
		    (struct async_struct *) tty->driver_data;
		if ((info->flags & ASYNC_SPD_MASK) == ASYNC_SPD_HI)
			return (B57600);
		if ((info->flags & ASYNC_SPD_MASK) == ASYNC_SPD_VHI)
			return (B115200);
	}
	return (tty->termios->c_cflag & CBAUD);
}

/*
 * set_baud sets the baud rate to the rate defined by baudcode
 * Note: The rate B38400 should be avoided, because the user may have
 * issued a 'setserial' speed override to map that to a different speed.
 * We could achieve a true rate of 38400 if we needed to by cancelling
 * any user speed override that is in place, but that might annoy the
 * user, so it is simplest to just avoid using 38400.
 */
static void set_baud(struct tty_struct *tty, unsigned int baudcode)
{
	struct termios old_termios = *(tty->termios);
	tty->termios->c_cflag &= ~CBAUD;	/* Clear the old baud setting */
	tty->termios->c_cflag |= baudcode;	/* Set the new baud setting */
	tty->driver->set_termios(tty, &old_termios);
}

/*
 * Convert a string to a Metricom Address.
 */

#define IS_RADIO_ADDRESS(p) (                                                 \
  isdigit((p)[0]) && isdigit((p)[1]) && isdigit((p)[2]) && isdigit((p)[3]) && \
  (p)[4] == '-' &&                                                            \
  isdigit((p)[5]) && isdigit((p)[6]) && isdigit((p)[7]) && isdigit((p)[8])    )

static int string_to_radio_address(MetricomAddress * addr, __u8 * p)
{
	if (!IS_RADIO_ADDRESS(p))
		return (1);
	addr->c[0] = 0;
	addr->c[1] = 0;
	addr->c[2] = READHEX(p[0]) << 4 | READHEX(p[1]);
	addr->c[3] = READHEX(p[2]) << 4 | READHEX(p[3]);
	addr->c[4] = READHEX(p[5]) << 4 | READHEX(p[6]);
	addr->c[5] = READHEX(p[7]) << 4 | READHEX(p[8]);
	return (0);
}

/*
 * Convert a Metricom Address to a string.
 */

static __u8 *radio_address_to_string(const MetricomAddress * addr,
				     MetricomAddressString * p)
{
	sprintf(p->c, "%02X%02X-%02X%02X", addr->c[2], addr->c[3],
		addr->c[4], addr->c[5]);
	return (p->c);
}

/*