/* 
   * Cryptographic API.
   *
   * Deflate algorithm (RFC 1951), implemented here primarily for use
   * by IPCOMP (RFC 3173 & RFC 2394).
   *
   * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
   * 
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License as published by the Free
   * Software Foundation; either version 2 of the License, or (at your option) 
   * any later version.
   *
   * FIXME: deflate transforms will require up to a total of about 436k of kernel
   * memory on i386 (390k for compression, the rest for decompression), as the
   * current zlib kernel code uses a worst case pre-allocation system by default.
   * This needs to be fixed so that the amount of memory required is properly
   * related to the  winbits and memlevel parameters.
   *
   * The default winbits of 11 should suit most packets, and it may be something
   * to configure on a per-tfm basis in the future.
   *
   * Currently, compression history is not maintained between tfm calls, as
   * it is not needed for IPCOMP and keeps the code simpler.  It can be
   * implemented if someone wants it.
   */
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/crypto.h>
  #include <linux/zlib.h>
  #include <linux/vmalloc.h>
  #include <linux/interrupt.h>
  #include <linux/mm.h>
  #include <linux/net.h>
  #include <linux/slab.h>
  
  #define DEFLATE_DEF_LEVEL		Z_DEFAULT_COMPRESSION
  #define DEFLATE_DEF_WINBITS		11
  #define DEFLATE_DEF_MEMLEVEL		MAX_MEM_LEVEL
  
  struct deflate_ctx {
  	struct z_stream_s comp_stream;
  	struct z_stream_s decomp_stream;
  };
  
  static int deflate_comp_init(struct deflate_ctx *ctx)
  {
  	int ret = 0;
  	struct z_stream_s *stream = &ctx->comp_stream;
  
  	stream->workspace = vmalloc(zlib_deflate_workspacesize());
  	if (!stream->workspace ) {
  		ret = -ENOMEM;
  		goto out;
  	}
  	memset(stream->workspace, 0, zlib_deflate_workspacesize());
  	ret = zlib_deflateInit2(stream, DEFLATE_DEF_LEVEL, Z_DEFLATED,
  	                        -DEFLATE_DEF_WINBITS, DEFLATE_DEF_MEMLEVEL,
  	                        Z_DEFAULT_STRATEGY);
  	if (ret != Z_OK) {
  		ret = -EINVAL;
  		goto out_free;
  	}
  out:	
  	return ret;
  out_free:
  	vfree(stream->workspace);
  	goto out;
  }
  
  static int deflate_decomp_init(struct deflate_ctx *ctx)
  {
  	int ret = 0;
  	struct z_stream_s *stream = &ctx->decomp_stream;

  	stream->workspace = kzalloc(zlib_inflate_workspacesize(), GFP_KERNEL);

  	if (!stream->workspace ) {
  		ret = -ENOMEM;
  		goto out;
  	}

  	ret = zlib_inflateInit2(stream, -DEFLATE_DEF_WINBITS);
  	if (ret != Z_OK) {
  		ret = -EINVAL;
  		goto out_free;
  	}
  out:
  	return ret;
  out_free:
  	kfree(stream->workspace);
  	goto out;
  }
  
  static void deflate_comp_exit(struct deflate_ctx *ctx)
  {

  	zlib_deflateEnd(&ctx->comp_stream);

  	vfree(ctx->comp_stream.workspace);
  }
  
  static void deflate_decomp_exit(struct deflate_ctx *ctx)
  {

  	zlib_inflateEnd(&ctx->decomp_stream);

  	kfree(ctx->decomp_stream.workspace);
  }

  static int deflate_init(struct crypto_tfm *tfm)

  {

  	struct deflate_ctx *ctx = crypto_tfm_ctx(tfm);

  	int ret;
  	
  	ret = deflate_comp_init(ctx);
  	if (ret)
  		goto out;
  	ret = deflate_decomp_init(ctx);
  	if (ret)
  		deflate_comp_exit(ctx);
  out:
  	return ret;
  }

  static void deflate_exit(struct crypto_tfm *tfm)

  {

  	struct deflate_ctx *ctx = crypto_tfm_ctx(tfm);

  	deflate_comp_exit(ctx);
  	deflate_decomp_exit(ctx);
  }

  static int deflate_compress(struct crypto_tfm *tfm, const u8 *src,
  			    unsigned int slen, u8 *dst, unsigned int *dlen)

  {
  	int ret = 0;

  	struct deflate_ctx *dctx = crypto_tfm_ctx(tfm);

  	struct z_stream_s *stream = &dctx->comp_stream;
  
  	ret = zlib_deflateReset(stream);
  	if (ret != Z_OK) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	stream->next_in = (u8 *)src;
  	stream->avail_in = slen;
  	stream->next_out = (u8 *)dst;
  	stream->avail_out = *dlen;
  
  	ret = zlib_deflate(stream, Z_FINISH);
  	if (ret != Z_STREAM_END) {
  		ret = -EINVAL;
  		goto out;
  	}
  	ret = 0;
  	*dlen = stream->total_out;
  out:
  	return ret;
  }
   

  static int deflate_decompress(struct crypto_tfm *tfm, const u8 *src,
  			      unsigned int slen, u8 *dst, unsigned int *dlen)

  {
  	
  	int ret = 0;

  	struct deflate_ctx *dctx = crypto_tfm_ctx(tfm);

  	struct z_stream_s *stream = &dctx->decomp_stream;
  
  	ret = zlib_inflateReset(stream);
  	if (ret != Z_OK) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	stream->next_in = (u8 *)src;
  	stream->avail_in = slen;
  	stream->next_out = (u8 *)dst;
  	stream->avail_out = *dlen;
  
  	ret = zlib_inflate(stream, Z_SYNC_FLUSH);
  	/*
  	 * Work around a bug in zlib, which sometimes wants to taste an extra
  	 * byte when being used in the (undocumented) raw deflate mode.
  	 * (From USAGI).
  	 */
  	if (ret == Z_OK && !stream->avail_in && stream->avail_out) {
  		u8 zerostuff = 0;
  		stream->next_in = &zerostuff;
  		stream->avail_in = 1; 
  		ret = zlib_inflate(stream, Z_FINISH);
  	}
  	if (ret != Z_STREAM_END) {
  		ret = -EINVAL;
  		goto out;
  	}
  	ret = 0;
  	*dlen = stream->total_out;
  out:
  	return ret;
  }
  
  static struct crypto_alg alg = {
  	.cra_name		= "deflate",
  	.cra_flags		= CRYPTO_ALG_TYPE_COMPRESS,
  	.cra_ctxsize		= sizeof(struct deflate_ctx),
  	.cra_module		= THIS_MODULE,
  	.cra_list		= LIST_HEAD_INIT(alg.cra_list),

  	.cra_init		= deflate_init,
  	.cra_exit		= deflate_exit,

  	.cra_u			= { .compress = {

  	.coa_compress 		= deflate_compress,
  	.coa_decompress  	= deflate_decompress } }
  };

  static int __init deflate_mod_init(void)

  {
  	return crypto_register_alg(&alg);
  }

  static void __exit deflate_mod_fini(void)

  {
  	crypto_unregister_alg(&alg);
  }

  module_init(deflate_mod_init);
  module_exit(deflate_mod_fini);

  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("Deflate Compression Algorithm for IPCOMP");
  MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");