/*
   * ppp_deflate.c - interface the zlib procedures for Deflate compression
   * and decompression (as used by gzip) to the PPP code.
   *
   * Copyright 1994-1998 Paul Mackerras.
   *
   *  This program is free software; you can redistribute it and/or
   *  modify it under the terms of the GNU General Public License
   *  version 2 as published by the Free Software Foundation.
   */
  
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/vmalloc.h>
  #include <linux/init.h>
  #include <linux/string.h>
  
  #include <linux/ppp_defs.h>
  #include <linux/ppp-comp.h>
  
  #include <linux/zlib.h>
  #include <asm/unaligned.h>
  
  /*
   * State for a Deflate (de)compressor.
   */
  struct ppp_deflate_state {
      int		seqno;
      int		w_size;
      int		unit;
      int		mru;
      int		debug;
      z_stream	strm;
      struct compstat stats;
  };
  
  #define DEFLATE_OVHD	2		/* Deflate overhead/packet */
  
  static void	*z_comp_alloc(unsigned char *options, int opt_len);
  static void	*z_decomp_alloc(unsigned char *options, int opt_len);
  static void	z_comp_free(void *state);
  static void	z_decomp_free(void *state);
  static int	z_comp_init(void *state, unsigned char *options,
  				 int opt_len,
  				 int unit, int hdrlen, int debug);
  static int	z_decomp_init(void *state, unsigned char *options,
  				   int opt_len,
  				   int unit, int hdrlen, int mru, int debug);
  static int	z_compress(void *state, unsigned char *rptr,
  				unsigned char *obuf,
  				int isize, int osize);
  static void	z_incomp(void *state, unsigned char *ibuf, int icnt);
  static int	z_decompress(void *state, unsigned char *ibuf,
  				int isize, unsigned char *obuf, int osize);
  static void	z_comp_reset(void *state);
  static void	z_decomp_reset(void *state);
  static void	z_comp_stats(void *state, struct compstat *stats);
  
  /**
   *	z_comp_free - free the memory used by a compressor
   *	@arg:	pointer to the private state for the compressor.
   */
  static void z_comp_free(void *arg)
  {
  	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
  
  	if (state) {
  		zlib_deflateEnd(&state->strm);
  		vfree(state->strm.workspace);
  		kfree(state);
  	}
  }
  
  /**
   *	z_comp_alloc - allocate space for a compressor.
   *	@options: pointer to CCP option data
   *	@opt_len: length of the CCP option at @options.
   *
   *	The @options pointer points to the a buffer containing the
   *	CCP option data for the compression being negotiated.  It is
   *	formatted according to RFC1979, and describes the window
   *	size that the peer is requesting that we use in compressing
   *	data to be sent to it.
   *
   *	Returns the pointer to the private state for the compressor,
   *	or NULL if we could not allocate enough memory.
   */
  static void *z_comp_alloc(unsigned char *options, int opt_len)
  {
  	struct ppp_deflate_state *state;
  	int w_size;
  
  	if (opt_len != CILEN_DEFLATE ||
  	    (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT) ||
  	    options[1] != CILEN_DEFLATE ||
  	    DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL ||
  	    options[3] != DEFLATE_CHK_SEQUENCE)
  		return NULL;
  	w_size = DEFLATE_SIZE(options[2]);
  	if (w_size < DEFLATE_MIN_SIZE || w_size > DEFLATE_MAX_SIZE)
  		return NULL;
  
  	state = kzalloc(sizeof(*state),
  						     GFP_KERNEL);
  	if (state == NULL)
  		return NULL;
  
  	state->strm.next_in   = NULL;
  	state->w_size         = w_size;
  	state->strm.workspace = vmalloc(zlib_deflate_workspacesize(-w_size, 8));
  	if (state->strm.workspace == NULL)
  		goto out_free;
  
  	if (zlib_deflateInit2(&state->strm, Z_DEFAULT_COMPRESSION,
  			 DEFLATE_METHOD_VAL, -w_size, 8, Z_DEFAULT_STRATEGY)
  	    != Z_OK)
  		goto out_free;
  	return (void *) state;
  
  out_free:
  	z_comp_free(state);
  	return NULL;
  }
  
  /**
   *	z_comp_init - initialize a previously-allocated compressor.
   *	@arg:	pointer to the private state for the compressor
   *	@options: pointer to the CCP option data describing the
   *		compression that was negotiated with the peer
   *	@opt_len: length of the CCP option data at @options
   *	@unit:	PPP unit number for diagnostic messages
   *	@hdrlen: ignored (present for backwards compatibility)
   *	@debug:	debug flag; if non-zero, debug messages are printed.
   *
   *	The CCP options described by @options must match the options
   *	specified when the compressor was allocated.  The compressor
   *	history is reset.  Returns 0 for failure (CCP options don't
   *	match) or 1 for success.
   */
  static int z_comp_init(void *arg, unsigned char *options, int opt_len,
  		       int unit, int hdrlen, int debug)
  {
  	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
  
  	if (opt_len < CILEN_DEFLATE ||
  	    (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT) ||
  	    options[1] != CILEN_DEFLATE ||
  	    DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL ||
  	    DEFLATE_SIZE(options[2]) != state->w_size ||
  	    options[3] != DEFLATE_CHK_SEQUENCE)
  		return 0;
  
  	state->seqno = 0;
  	state->unit  = unit;
  	state->debug = debug;
  
  	zlib_deflateReset(&state->strm);
  
  	return 1;
  }
  
  /**
   *	z_comp_reset - reset a previously-allocated compressor.
   *	@arg:	pointer to private state for the compressor.
   *
   *	This clears the history for the compressor and makes it
   *	ready to start emitting a new compressed stream.
   */
  static void z_comp_reset(void *arg)
  {
  	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
  
  	state->seqno = 0;
  	zlib_deflateReset(&state->strm);
  }
  
  /**
   *	z_compress - compress a PPP packet with Deflate compression.
   *	@arg:	pointer to private state for the compressor
   *	@rptr:	uncompressed packet (input)
   *	@obuf:	compressed packet (output)
   *	@isize:	size of uncompressed packet
   *	@osize:	space available at @obuf
   *
   *	Returns the length of the compressed packet, or 0 if the
   *	packet is incompressible.
   */
  static int z_compress(void *arg, unsigned char *rptr, unsigned char *obuf,
  	       int isize, int osize)
  {
  	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
  	int r, proto, off, olen, oavail;
  	unsigned char *wptr;
  
  	/*
  	 * Check that the protocol is in the range we handle.
  	 */
  	proto = PPP_PROTOCOL(rptr);
  	if (proto > 0x3fff || proto == 0xfd || proto == 0xfb)
  		return 0;
  
  	/* Don't generate compressed packets which are larger than
  	   the uncompressed packet. */
  	if (osize > isize)
  		osize = isize;
  
  	wptr = obuf;
  
  	/*
  	 * Copy over the PPP header and store the 2-byte sequence number.
  	 */
  	wptr[0] = PPP_ADDRESS(rptr);
  	wptr[1] = PPP_CONTROL(rptr);
  	put_unaligned_be16(PPP_COMP, wptr + 2);
  	wptr += PPP_HDRLEN;
  	put_unaligned_be16(state->seqno, wptr);
  	wptr += DEFLATE_OVHD;
  	olen = PPP_HDRLEN + DEFLATE_OVHD;
  	state->strm.next_out = wptr;
  	state->strm.avail_out = oavail = osize - olen;
  	++state->seqno;
  
  	off = (proto > 0xff) ? 2 : 3;	/* skip 1st proto byte if 0 */
  	rptr += off;
  	state->strm.next_in = rptr;
  	state->strm.avail_in = (isize - off);
  
  	for (;;) {
  		r = zlib_deflate(&state->strm, Z_PACKET_FLUSH);
  		if (r != Z_OK) {
  			if (state->debug)
  				printk(KERN_ERR
  				       "z_compress: deflate returned %d
  ", r);
  			break;
  		}
  		if (state->strm.avail_out == 0) {
  			olen += oavail;
  			state->strm.next_out = NULL;
  			state->strm.avail_out = oavail = 1000000;
  		} else {
  			break;		/* all done */
  		}
  	}
  	olen += oavail - state->strm.avail_out;
  
  	/*
  	 * See if we managed to reduce the size of the packet.
  	 */
  	if (olen < isize && olen <= osize) {
  		state->stats.comp_bytes += olen;
  		state->stats.comp_packets++;
  	} else {
  		state->stats.inc_bytes += isize;
  		state->stats.inc_packets++;
  		olen = 0;
  	}
  	state->stats.unc_bytes += isize;
  	state->stats.unc_packets++;
  
  	return olen;
  }
  
  /**
   *	z_comp_stats - return compression statistics for a compressor
   *		or decompressor.
   *	@arg:	pointer to private space for the (de)compressor
   *	@stats:	pointer to a struct compstat to receive the result.
   */
  static void z_comp_stats(void *arg, struct compstat *stats)
  {
  	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
  
  	*stats = state->stats;
  }
  
  /**
   *	z_decomp_free - Free the memory used by a decompressor.
   *	@arg:	pointer to private space for the decompressor.
   */
  static void z_decomp_free(void *arg)
  {
  	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
  
  	if (state) {
  		zlib_inflateEnd(&state->strm);
  		vfree(state->strm.workspace);
  		kfree(state);
  	}
  }
  
  /**
   *	z_decomp_alloc - allocate space for a decompressor.
   *	@options: pointer to CCP option data
   *	@opt_len: length of the CCP option at @options.
   *
   *	The @options pointer points to the a buffer containing the
   *	CCP option data for the compression being negotiated.  It is
   *	formatted according to RFC1979, and describes the window
   *	size that we are requesting the peer to use in compressing
   *	data to be sent to us.
   *
   *	Returns the pointer to the private state for the decompressor,
   *	or NULL if we could not allocate enough memory.
   */
  static void *z_decomp_alloc(unsigned char *options, int opt_len)
  {
  	struct ppp_deflate_state *state;
  	int w_size;
  
  	if (opt_len != CILEN_DEFLATE ||
  	    (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT) ||
  	    options[1] != CILEN_DEFLATE ||
  	    DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL ||
  	    options[3] != DEFLATE_CHK_SEQUENCE)
  		return NULL;
  	w_size = DEFLATE_SIZE(options[2]);
  	if (w_size < DEFLATE_MIN_SIZE || w_size > DEFLATE_MAX_SIZE)
  		return NULL;
  
  	state = kzalloc(sizeof(*state), GFP_KERNEL);
  	if (state == NULL)
  		return NULL;
  
  	state->w_size         = w_size;
  	state->strm.next_out  = NULL;
  	state->strm.workspace = vmalloc(zlib_inflate_workspacesize());
  	if (state->strm.workspace == NULL)
  		goto out_free;
  
  	if (zlib_inflateInit2(&state->strm, -w_size) != Z_OK)
  		goto out_free;
  	return (void *) state;
  
  out_free:
  	z_decomp_free(state);
  	return NULL;
  }
  
  /**
   *	z_decomp_init - initialize a previously-allocated decompressor.
   *	@arg:	pointer to the private state for the decompressor
   *	@options: pointer to the CCP option data describing the
   *		compression that was negotiated with the peer
   *	@opt_len: length of the CCP option data at @options
   *	@unit:	PPP unit number for diagnostic messages
   *	@hdrlen: ignored (present for backwards compatibility)
   *	@mru:	maximum length of decompressed packets
   *	@debug:	debug flag; if non-zero, debug messages are printed.
   *
   *	The CCP options described by @options must match the options
   *	specified when the decompressor was allocated.  The decompressor
   *	history is reset.  Returns 0 for failure (CCP options don't
   *	match) or 1 for success.
   */
  static int z_decomp_init(void *arg, unsigned char *options, int opt_len,
  			 int unit, int hdrlen, int mru, int debug)
  {
  	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
  
  	if (opt_len < CILEN_DEFLATE ||
  	    (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT) ||
  	    options[1] != CILEN_DEFLATE ||
  	    DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL ||
  	    DEFLATE_SIZE(options[2]) != state->w_size ||
  	    options[3] != DEFLATE_CHK_SEQUENCE)
  		return 0;
  
  	state->seqno = 0;
  	state->unit  = unit;
  	state->debug = debug;
  	state->mru   = mru;
  
  	zlib_inflateReset(&state->strm);
  
  	return 1;
  }
  
  /**
   *	z_decomp_reset - reset a previously-allocated decompressor.
   *	@arg:	pointer to private state for the decompressor.
   *
   *	This clears the history for the decompressor and makes it
   *	ready to receive a new compressed stream.
   */
  static void z_decomp_reset(void *arg)
  {
  	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
  
  	state->seqno = 0;
  	zlib_inflateReset(&state->strm);
  }
  
  /**
   *	z_decompress - decompress a Deflate-compressed packet.
   *	@arg:	pointer to private state for the decompressor
   *	@ibuf:	pointer to input (compressed) packet data
   *	@isize:	length of input packet
   *	@obuf:	pointer to space for output (decompressed) packet
   *	@osize:	amount of space available at @obuf
   *
   * Because of patent problems, we return DECOMP_ERROR for errors
   * found by inspecting the input data and for system problems, but
   * DECOMP_FATALERROR for any errors which could possibly be said to
   * be being detected "after" decompression.  For DECOMP_ERROR,
   * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
   * infringing a patent of Motorola's if we do, so we take CCP down
   * instead.
   *
   * Given that the frame has the correct sequence number and a good FCS,
   * errors such as invalid codes in the input most likely indicate a
   * bug, so we return DECOMP_FATALERROR for them in order to turn off
   * compression, even though they are detected by inspecting the input.
   */
  static int z_decompress(void *arg, unsigned char *ibuf, int isize,
  		 unsigned char *obuf, int osize)
  {
  	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
  	int olen, seq, r;
  	int decode_proto, overflow;
  	unsigned char overflow_buf[1];
  
  	if (isize <= PPP_HDRLEN + DEFLATE_OVHD) {
  		if (state->debug)
  			printk(KERN_DEBUG "z_decompress%d: short pkt (%d)
  ",
  			       state->unit, isize);
  		return DECOMP_ERROR;
  	}
  
  	/* Check the sequence number. */
  	seq = get_unaligned_be16(ibuf + PPP_HDRLEN);
  	if (seq != (state->seqno & 0xffff)) {
  		if (state->debug)
  			printk(KERN_DEBUG "z_decompress%d: bad seq # %d, expected %d
  ",
  			       state->unit, seq, state->seqno & 0xffff);
  		return DECOMP_ERROR;
  	}
  	++state->seqno;
  
  	/*
  	 * Fill in the first part of the PPP header.  The protocol field
  	 * comes from the decompressed data.
  	 */
  	obuf[0] = PPP_ADDRESS(ibuf);
  	obuf[1] = PPP_CONTROL(ibuf);
  	obuf[2] = 0;
  
  	/*
  	 * Set up to call inflate.  We set avail_out to 1 initially so we can
  	 * look at the first byte of the output and decide whether we have
  	 * a 1-byte or 2-byte protocol field.
  	 */
  	state->strm.next_in = ibuf + PPP_HDRLEN + DEFLATE_OVHD;
  	state->strm.avail_in = isize - (PPP_HDRLEN + DEFLATE_OVHD);
  	state->strm.next_out = obuf + 3;
  	state->strm.avail_out = 1;
  	decode_proto = 1;
  	overflow = 0;
  
  	/*
  	 * Call inflate, supplying more input or output as needed.
  	 */
  	for (;;) {
  		r = zlib_inflate(&state->strm, Z_PACKET_FLUSH);
  		if (r != Z_OK) {
  			if (state->debug)
  				printk(KERN_DEBUG "z_decompress%d: inflate returned %d (%s)
  ",
  				       state->unit, r, (state->strm.msg? state->strm.msg: ""));
  			return DECOMP_FATALERROR;
  		}
  		if (state->strm.avail_out != 0)
  			break;		/* all done */
  		if (decode_proto) {
  			state->strm.avail_out = osize - PPP_HDRLEN;
  			if ((obuf[3] & 1) == 0) {
  				/* 2-byte protocol field */
  				obuf[2] = obuf[3];
  				--state->strm.next_out;
  				++state->strm.avail_out;
  			}
  			decode_proto = 0;
  		} else if (!overflow) {
  			/*
  			 * We've filled up the output buffer; the only way to
  			 * find out whether inflate has any more characters
  			 * left is to give it another byte of output space.
  			 */
  			state->strm.next_out = overflow_buf;
  			state->strm.avail_out = 1;
  			overflow = 1;
  		} else {
  			if (state->debug)
  				printk(KERN_DEBUG "z_decompress%d: ran out of mru
  ",
  				       state->unit);
  			return DECOMP_FATALERROR;
  		}
  	}
  
  	if (decode_proto) {
  		if (state->debug)
  			printk(KERN_DEBUG "z_decompress%d: didn't get proto
  ",
  			       state->unit);
  		return DECOMP_ERROR;
  	}
  
  	olen = osize + overflow - state->strm.avail_out;
  	state->stats.unc_bytes += olen;
  	state->stats.unc_packets++;
  	state->stats.comp_bytes += isize;
  	state->stats.comp_packets++;
  
  	return olen;
  }
  
  /**
   *	z_incomp - add incompressible input data to the history.
   *	@arg:	pointer to private state for the decompressor
   *	@ibuf:	pointer to input packet data
   *	@icnt:	length of input data.
   */
  static void z_incomp(void *arg, unsigned char *ibuf, int icnt)
  {
  	struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
  	int proto, r;
  
  	/*
  	 * Check that the protocol is one we handle.
  	 */
  	proto = PPP_PROTOCOL(ibuf);
  	if (proto > 0x3fff || proto == 0xfd || proto == 0xfb)
  		return;
  
  	++state->seqno;
  
  	/*
  	 * We start at the either the 1st or 2nd byte of the protocol field,
  	 * depending on whether the protocol value is compressible.
  	 */
  	state->strm.next_in = ibuf + 3;
  	state->strm.avail_in = icnt - 3;
  	if (proto > 0xff) {
  		--state->strm.next_in;
  		++state->strm.avail_in;
  	}
  
  	r = zlib_inflateIncomp(&state->strm);
  	if (r != Z_OK) {
  		/* gak! */
  		if (state->debug) {
  			printk(KERN_DEBUG "z_incomp%d: inflateIncomp returned %d (%s)
  ",
  			       state->unit, r, (state->strm.msg? state->strm.msg: ""));
  		}
  		return;
  	}
  
  	/*
  	 * Update stats.
  	 */
  	state->stats.inc_bytes += icnt;
  	state->stats.inc_packets++;
  	state->stats.unc_bytes += icnt;
  	state->stats.unc_packets++;
  }
  
  /*************************************************************
   * Module interface table
   *************************************************************/
  
  /* These are in ppp_generic.c */
  extern int  ppp_register_compressor   (struct compressor *cp);
  extern void ppp_unregister_compressor (struct compressor *cp);
  
  /*
   * Procedures exported to if_ppp.c.
   */
  static struct compressor ppp_deflate = {
  	.compress_proto =	CI_DEFLATE,
  	.comp_alloc =		z_comp_alloc,
  	.comp_free =		z_comp_free,
  	.comp_init =		z_comp_init,
  	.comp_reset =		z_comp_reset,
  	.compress =		z_compress,
  	.comp_stat =		z_comp_stats,
  	.decomp_alloc =		z_decomp_alloc,
  	.decomp_free =		z_decomp_free,
  	.decomp_init =		z_decomp_init,
  	.decomp_reset =		z_decomp_reset,
  	.decompress =		z_decompress,
  	.incomp =		z_incomp,
  	.decomp_stat =		z_comp_stats,
  	.owner =		THIS_MODULE
  };
  
  static struct compressor ppp_deflate_draft = {
  	.compress_proto =	CI_DEFLATE_DRAFT,
  	.comp_alloc =		z_comp_alloc,
  	.comp_free =		z_comp_free,
  	.comp_init =		z_comp_init,
  	.comp_reset =		z_comp_reset,
  	.compress =		z_compress,
  	.comp_stat =		z_comp_stats,
  	.decomp_alloc =		z_decomp_alloc,
  	.decomp_free =		z_decomp_free,
  	.decomp_init =		z_decomp_init,
  	.decomp_reset =		z_decomp_reset,
  	.decompress =		z_decompress,
  	.incomp =		z_incomp,
  	.decomp_stat =		z_comp_stats,
  	.owner =		THIS_MODULE
  };
  
  static int __init deflate_init(void)
  {
          int answer = ppp_register_compressor(&ppp_deflate);
          if (answer == 0)
                  printk(KERN_INFO
  		       "PPP Deflate Compression module registered
  ");
  	ppp_register_compressor(&ppp_deflate_draft);
          return answer;
  }
  
  static void __exit deflate_cleanup(void)
  {
  	ppp_unregister_compressor(&ppp_deflate);
  	ppp_unregister_compressor(&ppp_deflate_draft);
  }
  
  module_init(deflate_init);
  module_exit(deflate_cleanup);
  MODULE_LICENSE("Dual BSD/GPL");
  MODULE_ALIAS("ppp-compress-" __stringify(CI_DEFLATE));
  MODULE_ALIAS("ppp-compress-" __stringify(CI_DEFLATE_DRAFT));